Proceedings of 38th Annual Condensed Matter and Materials Meeting 2014 Waiheke Island Resort, Waiheke, Auckland, New Zealand 4th February - 7th February, 2014 ISBN: 978-0-646-93339-9 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Australian Institute of Physics Editorial Note 'Proceedings of Wagga 2014' The 38th Annual Condensed Matter and Materials Meeting ISBN: 978-0-646-93339-9 Editor: Tilo Söhnel The 38th Annual Condensed Matter and Materials Meeting was held at Waiheke Island, Auckland, New Zealand, from 4-7 February, 2014. There were 87 attendees, including international visitors [France, Germany, USA, Taiwan]. A total of 11 invited and 28 contributed oral papers were presented during the two and one half days of scientific sessions. There were also two sessions with a total of 42 poster presentations. All presenters were invited to submit a manuscript (six pages for invited papers and four for contributed papers) for publication in the conference proceedings. Each manuscript was refereed by at least two anonymous reviewers who worked to a set of guidelines made available by the editor. Each accepted publication therefore satisfies the requirements for classification as a refereed conference publication (E1). The organizers would like to thank the reviewers for their time and effort in reviewing manuscripts, which resulted in 8 papers being accepted for publication. The accepted manuscripts are available at the on-line publication section of the Australian Institute of Physics national web site (http://www.aip.org.au/). Organising committee: Tilo Söhnel (chair), Graham Bowmaker, Morgan Allison, Daniel Wilson (all University of Auckland), Dr Ben Ruck (Victoria University of Wellington), Dr Mark Waterland, (Massey University) Correspondence: t.soehnel@auckland.ac.nz Date: December 2014 I Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Contents Participants III Overall Timetable VII Program VIII Refereed conference publications 1 Abstracts, oral presentations 36 Abstracts, poster presentations 78 http://www.iycr2014.org II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 PARTICIPANTS Participant E-mail Affiliation Abu Bakar Faridah faridah.abubakar@pg.canterbury.ac MacDiarmid Institute/The .nz University of Canterbury Al-Azri Zakiya zala006@aucklanduni.ac.nz The University of Auckland Allison Morgan mall632@aucklanduni.ac.nz The University of Auckland Andrae Dirk dirk.andrae@fu-berlin.de Freie Universität Berlin, Germany Anton Eva-Maria eva.anton@vuw.ac.nz Victoria University of Wellington Appadoo Dominique Dominique.Appadoo@synchrotron. Australian Synchrotron org.au Ashcroft Neil ashcroftnw@gmail.com Cornell University, USA Auckett Josie jauc3270@uni.sydney.edu.au The University of Sydney Binns Jack j.binns@sms.ed.ac.uk The University of Edinburgh/The Bragg Institute Bowmaker Graham g.bowmaker@auckland.ac.nz The University of Auckland Cadogan Sean s.cadogan@adfa.edu.au The University of New South Wales, Canberra/ADFA Callori Sara sara.callori@ansto.gov.au The Bragg Institute/ANSTO/The University of New South Wales Cashion John john.cashion@monash.edu Monash University Chahal Harpreet hcha203@aucklanduni.ac.nz The University of Auckland Chan Andrew acha343@aucklanduni.ac.nz The University of Auckland Chan Ming mcha281@aucklanduni.ac.nz The University of Auckland Chen Wan-Ting wche214@aucklanduni.ac.nz The University of Auckland Chong Shen shen.chong@callaghaninnovation. Callaghan Innovation/ govt.nz Victoria University of Wellington Culcer Dimitrie d.culcer@unsw.edu.au The University of New South Wales, Sydney II I Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Donaldson Jethro jethro.donaldson@gmail.com Victoria University of Wellington Edgar Andy andy.edgar@vuw.ac.nz Victoria University of Wellington Edwards Alison alisonedwar@gmail.com The Bragg Insititute/ANSTO Finlayson Trevor trevorf@unimelb.edu.au The University of Melbourne Golovko Vladimir vladimir.golovko@canterbury.ac.nz The University of Canterbury/The MacDiarmid Institute Hamilton Alex alex.hamilton@unsw.edu.au The University of New South Wales, Sydney Hutchison Wayne w.hutchison@adfa.edu.au The University of New South Wales, Canberra Hsieh Pei-Huan phsi013@aucklanduni.ac.nz The University of Auckland Jin Jianyong j.jin@auckland.ac.nz The University of Auckland Kang Scott hkan026@aucklanduni.ac.nz The University of Auckland Kharkov Yaroslav y.kharkov@gmail.com The University of New South Wales, Sydney Kinnersley Tim tim.kinnersley@cleveland.co.nz Cleveland Process Automation Ltd Lewis Roger roger@uow.edu.au The University of Wollongong Lee Wai Tung (Hal) wtl@ansto.gov.au Australian Nuclear Science & Technology Organisation Leveneur Jerome j.leveneur@gns.cri.nz GNS Science Li Tommy z3185754@zmail.unsw.edu.au The University of New South Wales, Sydney Liang Chao clia493@aucklanduni.ac.nz The University of Auckland Liu Samuel liu_s@chem.usyd.edu.au The University of Sydney Loewenhaupt Michael loewenhaupt@physik.tu-dresden.de Technical University Dresden, Germany Maity Tanmay Tanmay.Maity@vuw.ac.nz MacDiarmid Institute/Victoria University of Wellington IV Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Mayard-Casely Helen helenmc@ansto.gov.au The Bragg Insititute/ANSTO McCree-Grey Jonathan jonathan.mccree-grey@ansto.gov. The Bragg au Insititute/ANSTO McIntyre Garry garry.mcintyre@ansto.gov.au Australian Nuclear Science & Technology Organisation Mohamed Zakiah mohame_z@chem.usyd.edu.au The University of Sydney Narayanan Narendirakumar n.narayanan@adfa.edu.au The University of New South Wales, Canberra Narayanaswamy Suresh suresh.narayanaswamy@callaghan MacDiarmid innovation.govt.nz Institute/Victoria University of Wellington Pahl Elke e.pahl@massey.ac.nz Massey University, Auckland Park Sy Eun park.syeun@gmail.com The University of Auckland Pavan Adriano apav0788@uni.sydney.edu.au The University of Sydney Prakash Tushara tusharap@gmail.com MacDiarmid Institute/Victoria University of Wellington Riley Daniel dry@ansto.gov.au Australian Nuclear Science & Technology Organisation Ruck Ben ben.ruck@vuw.ac.nz Victoria University of Wellington Qin Meng mqi@ansto.gov.au Australian Nuclear Science & Technology Organisation Sambale Sebastian sebastian.sambale@vuw.ac.nz Victoria University of Wellington Schwerdtfeger Peter peter.schwerdtfeger@gmail.com Massey University, Auckland Shahlori Rayomand RSHA206@aucklanduni.ac.nz The University of Auckland Smith Kevin kevin.smith@auckland.ac.nz The University of Auckland Söhnel Tilo t.soehnel@auckland.ac.nz The University of Auckland Srinivasan Ashwin ashwin@phys.unsw.edu.au The University of New South Wales, Sydney Stewart Glen g.stewart@adfa.edu.au The University of New South Wales, Canberra V Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Storey James james.storey@callaghaninnovation. Callaghan Innovation govt.nz Sushkov Oleg sushkov@phys.unsw.edu.au The University of New South Wales, Sydney Tallon Jeffery j.tallon@irl.cri.nz Callaghan Innovation Timmers Heiko h.timmers@adfa.edu.au The University of New South Wales, Canberra Trodahl Joe joe.trodahl@vuw.ac.nz MacDiarmid Institute/Victoria University of Wellington Ulrich Clemens c.ulrich@unsw.edu.au The University of New South Wales, Sydney von Seggern Heinz seggern@e-mat.tu-darmstadt.de Technical University Darmstadt, Germany Wang Xianglei xianglei.wang@student.adfa.edu.au The University of New South Wales, Canberra Waterland Mark M.Waterland@massey.ac.nz Massey University Whittle Thomas thomas.whittle@chem.usyd.edu.au The University of Sydney Wildes Andrew wildes@ill.fr Institute Laue-Langevin, Grenoble, France Willmott Geoff g.willmott@auckland.ac.nz The University of Auckland Wilson Daniel dwil259@aucklanduni.ac.nz The University of Auckland Winch Nicola nicola.winch@vuw.ac.nz Victoria University of Wellington Wu Chun-Ming muconic@gmail.com National Synchrotron Radiation Research Center, Taiwan Xu Guangyuan gxu331@aucklanduni.ac.nz The University of Auckland Yeoh Lareine lareine.yeoh@phys.unsw.edu.au The University of New South Wales, Sydney V I Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Overall Timetable Tuesday, 4th February 16:00 – 18:00 Registration 17:30 – 18:30 Welcome Drinks at “The Lookout” 18:30 Dinner at “The Lookout” Wednesday, 5th February 08:50 – 09:00 Opening 09:00 – 10:40 Presentations 10:40 – 11:00 Morning tea 11:00 – 12:50 Presentations 12:50 – 13:50 Lunch 14:00 – 15:50 Presentations 15:50 – 16:10 Afternoon Tea 16:10 – 16:40 Presentation 16:45 – 17:00 Business Meeting 17:00 – 18:30 Poster Session & Drinks from bar 19:00 Dinner – BBQ Buffet 20:30 Quiz night - 'Wagga Trivia' Thursday, 6th February 09:00 – 10:30 Presentations 10:30 – 10:50 Morning tea 10:50 – 12:40 Presentations 12:50 – 13:50 Lunch 14:00 – 15:30 Presentations 15:30 – 15:50 Afternoon Tea 15:50 – 17:00 Presentations 17:00 – 18:30 Poster Session & Drinks from bar 19:00 Departure to 'The Bay' 19:30 Conference Dinner at 'The Bay' Friday, 7th February 09:00 – 10:30 Presentations 10:30 – 10:50 Morning Tea 10:50 – 12:20 Presentations 12:20 – 12:30 Closing 12:30 – 13:30 Lunch V II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 2014 Program Tuesday, 4th February 16:00 – 18:00 Registration 17:30 Welcome Drinks at “The Lookout” 18:30 Dinner at “The Lookout” Wednesday, 5th February 08:50 – 09:00 Opening: Tilo Söhnel, The University of Auckland Chairperson: Glen Stewart 09:00 – 09:30 wo1 Adventures in Reciprocal Space – From Laue to Bragg and Back Again Allison Edwards, ANSTO, Sydney, Australia INVITED 09:30 – 09:50 wo2 Enhanced Ferroelectric Response in Strained Perovskites Joe Trodahl, Victoria University of Wellington, New Zealand 09:50 – 10:10 wo3 Weak antilocalisation in topological insulators Dimitrie Culcer, University of New South Wales, Sydney, Australia 10:10 – 10:40 wo4 The dynamics and critical properties of FePS3, an Ising-like two- dimensional magnet on a honeycomb lattice Andrew Wildes, Institut Laue-Langevin, Grenoble, France INVITED 10:40 – 11:00 Morning tea VI II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 11:00 – 12:50 Chairperson: Sean Cadogan 11:00 – 11:30 wo5 Colour Tunable Light Emission from Organic Field- Effect Transistors Heinz von Seggern, Technical University Darmstadt, Germany INVITED 11:30 – 11:50 wo6 Organic luminescent solar concentrators for solar cells Nicola Winch, Victoria University of Wellington, New Zealand 11:50 – 12:10 wo7 Structural Studies of Phase Transitions in Hybrid Organic- Inorganic Salts with Temperature and Pressure Jack Binns, The University of Edinburgh, Scotland 12:10 – 12:30 wo8 Optically and Electrically Detected Electron Spin Resonance in OLEDs Andy Edgar, Victoria University of Wellington, New Zealand 12:30 – 12:50 wo9 Characterization of a Fluoroperovskite Based Fibre Coupled Optical Dosimeter for Radiotherapy Jethro Donaldson, Wellington Regional Hospital, New Zealand 12:50 – 13:50 Lunch 14:00 – 15:50 Chairperson: Mark Waterland 14:00 – 14:30 wo10 Towards better understanding of atomically precise gold clusters and titania made using surface modifying agents Vladimir Golovko, University of Canterbury, New Zealand INVITED IX Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 14:30 – 14:50 wo11 Low Cost Refractive Index Sensing Using Zirconia Inverse Opal Thin Films Andrew Chan, The University of Auckland, New Zealand 14:50 – 15:10 wo12 Enhanced photocatalytic activity in F-TiO2: effect of solvent and fluorine modifier towards the morphology of TiO2 Fariah Abu Bakar, University of Canterbury, Christchurch, New Zealand 15:10 – 15:30 wo13 Induced few-electron GaAs Quantum Dots Lareine Yeoh, University of New South Wales, Sydney, Australia 15:30 – 15:50 wo14 SDW and AFM order in single crystal EuFe2As2 system under high-pressue using a new ceramic anvil high- pressure cell Narayanaswamy Suresh, Callaghan Innovation, Wellington, New Zealand 15:50 – 16:10 Afternoon Tea 16:10 – 16:40 Chairperson: John Cashion 16:10 – 16:40 wo15 Tribute to CSIRO Scientists Trevor Finlayson, Melbourne University, Australia INVITED 16:45 – 17:00 Business Meeting Chairperson: Tilo Söhnel 17:00 – 18:30 Poster Session 19:00 Dinner - BBQ Buffet 20:30 Wagga Trivia X Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Thursday, 6th February 09:00 – 10:30 Chairperson: Roger Lewis 09:00 – 09:30 to1 Toward an Accurate Description of Rare Gas Phases Peter Schwerdtfeger, Massey University, Auckland, New Zealand INVITED 09:30 – 09:50 to2 Total State Designation for Electronic States of Periodic Systems Dirk Andrae, Freie Universität Berlin, Germany 09:50 – 10:10 to3 Influence of Relativistic Effects on the Melting of Mercury Elke Pahl, Massey University, Auckland, New Zealand 10:10 – 10:30 to4 Transport Models in Nanofluids Geoff Willmott, The University of Auckland, New Zealand 10:30 – 10:50 Morning tea 10:50 – 12:40 Chairperson: Vladimir Golovko 10:50 – 11:20 to5 Magnetic properties of rare-earth nitride heterostructures for MRAM devices Eva-Maria Anton, Victoria University of Wellington, New Zealand INVITED 11:20 – 11:40 to6 Magnetically driven electric polarization in frustrated magnetic oxide multiferroics Narendirakumar Narayanan, University of New South Wales, Canberra, Australia X I Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 11:40 – 12:00 to7 Exploring the Properties of Complex Layered Tin Cluster Compounds Morgan Allison, The University of Auckland 12:00 – 12:20 to8 Low-temperature magnetic structure of Ca2Fe2O5 determined by single-crystal neutron diffraction Josie Auckett, The University of Sydney 12:20 – 12:40 to9 Magnetoelectric coupling in isotopically subtituted TbMn16/18O3 and RMn2O5 (R = Tb, Ho, and Y) explored by Raman light scattering Clemens Ulrich, University of New South Wales, Sydney, Australia 12:50 – 13:50 Lunch 14:00 – 15:30 Chairperson: Peter Schwerdtfeger 14:00 – 14:30 to10 Stress Controlled Metal-to-Insulator Transitions in Thin Film Vanadium Oxides Kevin Smith, The University of Auckland INVITED 14:30 – 14:50 to11 Freudenbergite – a New Example of Electron Hopping John Cashion, Monash University, Melbourne, Australia 14:50 – 15:10 to12 Crystal and magnetic structure of Li2MnSiO4 and Li2CoSiO4 characterized by neutron diffraction measurement Zakiah Mohamed, The University of Sydney, Australia 15:10 – 15:30 to13 Exotic Physics in Neutron Laue Diffraction Garry McIntyre, ANSTO, Sydney, Australia 15:30 – 15:50 Afternoon Tea X II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 15:50 – 17:00 Chairperson: Graham Bowmaker 15:50 – 16:20 to14 Condensed phase studies at the THz/Far-IR Beamline at the Australian Synchrotron Dominique Appadoo, Australian Synchrotron, Melbourne, Australia INVITED 16:20 – 16:40 to15 Status Report on SIKA – Taiwan’s Cold Neutron Triple- Axis Spectrometer at OPAL Chun-Ming Wu, National Synchrotron Radiation Research Center, Taiwan 16:40 – 17:00 to16 Polarised Neutrons for Materials Sciences Research at the Australian Nuclear Science and Technology Organisation (ANSTO) Wai Tung Hal Lee, ANSTO, Sydney, Australia 17:00 – 18:30 Poster Session 19:00 Departure to 'The Bay' 19:30 Conference Dinner at 'The Bay' XI II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Friday 7th February 09:00 – 10:30 Chairperson: Ben Ruck 09:00 – 09:30 fo1 Approaching Metallic Hydrogen by Stealth: Via the High-Hydrides Neil Ashcroft, Cornell University, USA INVITED 09:30 – 09:50 fo2 Exploring Jupiter’s icy moons with old techniques and big facilities – new insights on sulfuric acid hydrates Helen Maynard-Casely, ANSTO, Sydney, Australia 09:50 – 10:10 fo3 Large room temperature magnetoresistance in nanogranular materials Jérôme Leveneur, National Isotope Centre, GNS Science, Wellington, New Zealand 10:10 – 10:30 fo4 Magnetic order in gadolinium manganite probed by 155Gd- Mössbauer spectroscopy Glen Stewart, UNSW Canberra, Australia 10:30 – 10:50 Morning Tea 10:50 – 12:20 Chairperson: Clemens Ulrich 10:50 – 11:20 fo5 Enigma of Resonant Inelastic X-ray Scattering (RIXS) data for cuprates Oleg Sushkov, University of New South Wales, Sydney, Australia INVITED 11:20 – 11:40 fo6 Upper critical and irreversible fields of polycrystalline CeFeAsO1-xFx superconductors Shen Chong, Callaghan Innovation, Wellington, New Zealand XI V Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 11:40 – 12:00 fo7 Phonons in a highly-correlated electron system: the heavy-fermion superconductor CeCu2Si2 Michael Loewenhaupt, Technical University, Dresden, Germany 12:00 – 12:20 fo8 The thermodynamics of high-Tc superconductors Jeff Tallon, Victoria University of Wellington, New Zealand 12:20 – 12:30 Awards and Closing: Tilo Söhnel, University of Auckland 12:30 – 13:30 Lunch from 12:30 onwards Shuttle bus departures to Waiheke Wharf XV Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Poster Presentations Wednesday, 5th February wp1 First–principle study of palladium-defect pairing in doped Si A.A. Abiona and H. Timmers wp2 M/TiO2 Photocatalysts (M=Au, Pd, Pt and Au-Pt) for H2 Production from Ethanol-Water Mixtures Z.H.N. Al-Azri and G.I.N. Waterhouse wp3 Spin-reorientation in DyGa R.A. Susilo, J.M. Cadogan, R. Cobas, S. Muñoz-Pérez and M. Avdeev wp4 90° Magnetic Coupling in a NiFe/FeMn/biased NiFe Spin Valve Investigated by Polarised Neutron Reflectometry S.J. Callori, T. Zhu and F. Klose wp5 Synthesis and Characterisation of 3DOM ZIF-8 Thin-Films for Optical Gas Sensing Applications H.K. Chahal, G.M. Miskelly and G.I.N. Waterhouse wp6 Novel M-Pt/C (M = Ru, Sn, RuSn) Electrodes for Direct Alcohol Fuel Cells M. H. Chan and G.I.N. Waterhouse wp7 Ni/TiO2 – A low cost photocatalyst system for H2 Production from Biofuels W.-T. Chen and G.I.N. Waterhouse wp8 Enriching the properties of Mo-oxide layered hybrids with electron-rich zigzag fused aromatic spacer molecules I. u-din, S.V. Chong, S.G. Telfer, G.B. Jameson, M.R. Waterland and J.L. Tallon wp9 Inorganic/Organic Composites for X-ray Imaging N. Winch and A. Edgar wp10 Mechanical Properties of Tungsten Copper Composites: Direct Measurement by Neutron Diffraction P.J. Mignone, T.R. Finlayson, S. Kabra, S-Y. Zhang, G.V. Franks and D.P. Riley XV I Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 wp11 Novel SERS substrates for the Identification of Adulterants in Milk P.-H. Hsieh, D. Sun-Waterhouse and G.I.N. Waterhouse wp12 ESR studies of Magnetocaloric PrMn2−xFexGe2 Q.Y. Ren, W.D. Hutchison, J.L. Wang and S.J. Campbell wp13 Investigation of the order parameter of Pr in the filled skutterudite PrRu4P12 by soft resonant x-ray diffraction F. Li, A.M. Mulders, W.D. Hutchison, M. Garganourakis, Y. Tanaka, K. Nishimura and H. Sato wp14 The magnetic properties of Nd2Sn2O7 P. Imperia, R.J. Aldus, K.C. Rule and A. Studer wp15 Structure and Magnetism Studies of Cu1-xCoxSb2O6 Solid Solution H.-B. Kang, C. Ling and T. Söhnel wp16 Magnon mediated superconducting pairing in the vicinity of magnetic quantum critical point Y. Kharkov and O.P. Sushkov wp17 Ferromagnetism of Co,Eu Co-doped ZnO and 5%-Co doped TiO2 Magnetic Semiconductors O.J. Lee, X. Luo, W.T. Lee, V. Lauter, G. Triani, S. Li and J.B. Yi wp18 Temperature dependence of structural parameters of the layered magnetic glass Fe0.5Ni0.5PS3 D.J. Goossens, W.T. Lee and A.J. Studer wp19 Generalization of the Onsager quantization condition for spin-orbit coupled systems T. Li and O.P. Sushkov wp20 Characterization of the carboxyl groups in graphene oxide C. Liang, G. Xu and J. Jin wp21 Designing new n = 2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi O 2+2 2] layer S. Liu, P.E.R Blanchard, M. Avdeev, B.J. Kennedy and C.D. Ling XV II Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Thursday, 6th February tp1 Thermoelectric Properties of Polycrystalline Gadolinium Nitride T. Maity, H.J. Trodahl, B.J. Ruck, H. Warring and F. Natali tp2 Reflectometry as a tool for studying dye molecule orientation in dye- sensitised solar cells (DSCs) J. McCree-Grey and J.M. Cole tp3 Fabrication, Optical and Photocatalytic Properties of TiO2 Colloidal Crystals S.E. Park and G.I.N. Waterhouse tp4 Alkali metal and alkaline earth metal oxide materials for high temperature CO2 absorption and desorption studies A.F. Pavan and C.D. Ling tp5 Characterisation of permalloy and magnetite nanopowders T. Prakash, G.V.M. Williams, J. Kennedy, P.P. Murmu, J. Leveneur, S.V. Chong, P. Couture and S. Rubanov tp6 Molecular Dynamics Simulations of Thermal Condutivity of UO2, PuCrO3 and PuAlO3 M.J. Qin, E.Y. Kuo, M. Robinson, N.A. Marks, G.R. Lumpkin and S.C. Middleburgh tp7 Influence of Plasma Impurities on the Effective Performance of Fusion Relevant Materials D.P. Rileya, M. Guenettea, A. Deslandesa, S. C. Middleburgh, G. Lumpkina, L. Thomsenb and C. Corr tp8 Novel Magnetic Properties of Rare-Earth Nitrides B.J. Ruck tp9 75As NMR of underdoped CeFeAsO0.93F0.07 S. Sambale, D. Rybicki, G.V.M. Williams and S.V. Chong tp10 Influence of Oxygen on the Performance of Organic Field Effect Transistors L. Kehrer, A. Gassmann, C. Melzer and H. von Seggern XV III Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 tp11 Solar Hydrogen Production using Au/TiO2 Photocatalysts R. Shahlori and G.I.N. Waterhouse tp12 Electrical tuning of the hole Zeeman spin splitting in (100) Quantum wells A. Srinivasan, I. Farrer, D.A. Ritchie and A.R. Hamilton tp13 Identifying further inelastic neutron crystal field transitions in ErNiAl4 G.A. Stewart, W.D. Hutchison, Z. Yamani, J.M. Cadogan and D.H. Ryan tp14 Thin-Film Thermopower Measurement System Open for Business J.G. Storey and N. Suresh tp15 Phase transition enhanced thermoelectric performance in Cu2Se H. Liu, X. Shi, W. Zhang, L. Chen and S. Danilkin tp16 Characterisation of self-supporting submicron-thick graphitic carbon foils with reflection spectroscopy H. Timmers, C. Jansing, M. Tesch, M. Gilbert, A.G. Muirhead, A. Gauppd and H.-Ch. Mertins tp17 X-ray Dose Dependence and Spectral Hole-Burning Properties of Ball Milled Nanocrystalline Ba0.5Sr0.5FCl 3+0.5Br0.5:Sm X.Wang and H. Riesen tp18 Characterising Graphene Nanoribbons using Raman Microscopy M.R. Waterland, H. Dykstra and A.J. Way tp19 Structural Investigation of Tungsten Bronze Type Relaxor Ferroelectrics T.A. Whittle and S. Schmid tp20 Neutron powder diffraction and Synchrotron PD and XAS studies of Cu5- xMnxSbO6 and Cu5Sb1-xMoxO6 D.J. Wilson and T. Söhnel tp21 A novel approach to synthesis of highly reduced graphene oxide G. Xu, C. Liang, J. Zhang, H. Kang and J. Jin XI X Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Refereed conference publications Page 1 – to2 Total State Designation for Electronic States of Periodic Systems………..1 D. Andrae 2 – to7 Exploring the Properties of Complex Layered Tin Cluster Compounds…..6 M. Allison, S. Liu C. Ling G. Stewart and T. Söhnel 3 – to11 Freudenbergite – a New Example of Electron Hopping…….………..……10 J. D. Cashion, A. Lashtabeg, E. R. Vance, D.H.Ryan and J. Solano 4 – wo15 Tribute to CSIRO Scientists…………………………………………………..14 T.R. Finlayson 5 – wp15 Exploring the Structural and Magnetic Phase Transition of Cu1xCoxSb2O6…………………………………………………………………..20 H.-B. Kang a C. Ling b and T. Söhnel 6 – tp13 Identifying Further Inelastic Neutron Crystal Field Transitions in ErNiAl4…………………………………………………………………………..24 G.A. Stewart, W.D. Hutchison, Zahra Yamani, J.M. Cadogan and D.H. Ryan 7 – tp19 Structural Investigation of Tungsten Bronze Type Compounds in the Relaxor Ferroelectric Sr3Ti1-yZryNb4O15 System………………………..…..28 T. A. Whittle and S. Schmid 8 – tp20 Synchrotron and Neutron Powder Diffraction and XANES Studies of Cu5-xMnxSbO6……………………………………………………………….….32 D. J. Wilson and T. Söhnel XX Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Total State Designation for Electronic States of Periodic Systems D. Andrae Institute of Chemistry and Biochemistry, Physical and Theoretical Chemistry, Freie Universität Berlin, Takustr. 3, D-14195 Berlin, Germany. The role of a complete set of commuting operators (CSCO) is first recalled with the discussion of the electronic states of two finite systems as illustrative examples. It is then shown that its role is very well transferable to sequences of finite systems that approach a real periodic system in the limit where the number of monomers becomes huge. In addition, the concept of the density of states (DOS) of total energy E, n(E−E0) (E0 is the energy of the electronic ground state), is introduced as a system’s characteristic. 1. Introduction The state of a quantum mechanical system is completely specified by its eigenvalues associated with a complete set of commuting operators (CSCO) [1]. Consider bound states of the hydrogen atom as simple, but illustrative examples. The Hamiltonian H, the squared orbital angular momentum operator L2 and its z-component Lz form part of the CSCO for this case (inclusion of the Runge-Lenz vector operator and of spin operators completes the CSCO). The well-known eigenvalue equations for this case can be written as (in atomic units) H |nlm 2L〉 = − (2n2)−1 |nlm 2L〉, L2 |nlm 2L〉 = l(l + 1) |nlm 2L〉, Lz |nlm 2L〉 = m |nlm 2L〉, (1) where |nlm 2L〉 denotes a state under consideration. A given set of quantum numbers {n, l, m} (n > 0, 0 ≤ l < n, − l ≤ m ≤ l) identifies both the eigenvalues and the state (except for the spin part, which is, however, trivial in this case). Therefore, a state’s quantum numbers can be used as labels to designate it, as has already been done in eq. (1). Our example illustrates that “group-theoretical deductions are usually quite easy to perform and the information so obtained concerning the solutions [of the system’s Schrödin- ger equation (D. A.)], although not complete, often contains the essential physics” [2]. Only the eigenvalue associated with the Hamiltonian, i.e. the energy, cannot be deduced from group theory alone. The principle just stated, and illustrated above for the hydrogen atom, holds true for periodic systems (polymers, surfaces, crystals) as well, but it is not fully exploited there. In this context, one may ask to which extent we really master the problem of electronic structure in periodic systems with the currently available software tools. Or, more provoking, to which extent are we being mastered by the limitations still present in the theories that form the basis for existing software? In the next section, two finite systems and their low-lying electronic states are briefly discussed, as a reminder of the type of information that is contained in the symmetry labels of total electronic states and in order to introduce the density of states (DOS) of total energy E, n(E−E0) (E0 is the energy of the electronic ground state). The subsequent section extends the discussion then to electronic states of periodic systems, in order to show how the principle stated above is applicable there. 2. Electronic states of finite systems: two examples The first example is the oxygen atom, O, with electron configuration 1s2 2s2 2p4 (point group Kh in Schönflies notation). Three LS terms exist in Russell-Saunders coupling [2]: 3P 1 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 (L = S = 1), 1S (L = S = 0), 1D (L = 2, S = 0). Each term has a weight g = (2L+1)(2S+1), according to the number of degenerate states |p4 LMLSMS〉 differing only by ML and MS for given L and S. It is instructive to consider the situation also under reduced symmetry, because the full rotation-reflection group Kh cannot be used with standard software tools designed for the study of electronic structure of molecules. An overview of the situation, including the cases of the finite point groups D2h, C2v and C1, is given in Table 1. It is important to remark that all properties of the states (like, e.g., degrees of degeneracy of orbital and state energies, orbital occupation numbers, orbital radial parts) are independent of the point group actually used. The density of states (DOS) of total energy E, n(E−E0), for this case is shown in Fig. 1 (up to E−E0 ≈ 4.5 eV, E0 is the ground state energy). Table 1. Low-lying electronic terms of the oxygen atom, O, and of a trinuclear transition me- tal complex ion, [(µ q+3-L)M3] (assuming one unpaired electron per M ion), labeled under dif- ferent point groups. See Fig. 1 for corresponding densities of states (DOS) of total energy E. Electron configuration and List of resulting electronic termsa point group O 2p4: (p 4 3 1 1+1, p0, p−1) in Kh P / S / D (px, py, pz)4 in D 3 32h B1g, B2g, 3B 13g / A / 1g Ag(2), 1B 1 11g, B2g, B3g (px, py, pz)4 in C 32v A2, 3B1, 3B 1 1 1 1 12 / A1 / A1(2), A2, B1, B2 (px, py, p 4 3 1 1z) in C1 A(3) / A / A(5) [(µ q+ 33-L)M3] (a,e) : a2 e1 – a1 e2 – e3 in C 2 4 2 2 2 23 E – A / A, A, E – E a2 (a,a)1 – a1 (a,a)2 – (a,a)3 in C 2 41 A(2) – A / 2A, 2A, 2A(2) – 2A(2) a Number of degenerate terms of same symmetry in parentheses. Fig. 1. Density of low-lying states (DOS) of total energy E, n(E−E0), for finite systems, being a sequence of Dirac delta “peaks” with weights (indicated in parentheses at the top of each panel). Left panel: O atom (point group Kh), DOS for LS terms [3] from electron configuration 1s2 2s2 2p4. Right panel: A trinuclear transition metal complex ion [(µ3-L)M q+3] (point group C3), DOS for electronic terms from electron configuration (a,e)3. Our second example is a trinuclear transition metal complex ion with a triply bridging ligand L, [(µ3-L)M3]q+ (point group C3). We assume that each M ion contributes just a single unpaired electron, such that low-lying electronic states in ΓS coupling, |αΓγSMS〉, originate from an electron configuration (a,e)3. The resulting sets of electronic terms, both in C3 and in C1, are listed in Table 1, and a density of states (DOS) of total energy E, n(E−E0), associated 2 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 with this case is schematically shown in Fig. 1 (details of energy spacings and sequence of states are case-dependent, but unimportant for the present discussion). The designation of a state | I 〉 of a quantum mechanical system properly combines spin and space symmetry information (here denoted by a composite index I). If the state’s wave- function is constructed from single-electron functions (orbitals), then the eigenvalue asso- ciated with the Hamiltonian, the energy EI, reduces to a linear combination of one- and two- electron integrals. For a normalized state function (〈 I | I 〉 = 1), EI = 〈 I | H | I 〉 = Σ I Iij γ ij hij + Σijkl Γ ijkl gijkl. (2) All summations run over orbital indices, the state-specific coefficients γIij and ΓIijkl are known as structure factors or density matrix elements (for further details see [2] or any other good textbook on electronic structure theory for atoms and molecules). 3. Electronic states of periodic systems An ideal infinite periodic system (polymer, slab, crystal) built from monomers A has an infinite number of electronic states. An important quantity of interest, irrespective of the actual electronic state of the system, is the energy per unit cell limN→∞ E(AN)/N, which is finite (a single monomer A per unit cell was assumed). However, the limit process just indicated always ends abruptly because only finite pieces of periodic systems exist in the real world. But this implies that the tools discussed in the previous section become applicable, sometimes without great difficulties. For example, the designation 1A1g (point group Oh) can be given for the electronic ground state of both halite (rock salt, space group Fm-3m, no. 225) and diamond (space group Fd-3m, no. 227) crystals, if we idealize and assume cube-shaped crystals in the former case and octahedron-shaped crystals in the latter. In the case of diamond, dangling bonds at the crystal surface must have been saturated somehow (e. g. by H atoms) to make our designation valid. The situation is much more complicated for the simple metal lithium. Several polymorphs of lithium are known to exist up to moderate pressure [4], including bcc (under ambient conditions), fcc, hcp, and a low-temperature phase with samarium structure (hR9). What is the electronic ground state for each of these polymorphs, and how large are the energy differences between them at T = 0 K? How does the density of states (DOS) of total energy E per Li atom differ between these polymorphs? These questions cannot be answered yet. An approach to the electronic structure of periodic systems via finite-sized structures requires again the consideration of the spin and space parts of the electronic states of these structures. The problem of designation of these states is addressed in the following. 3.1 The spin part A set of N spins, each characterized by the same spin quantum number s (2s = 1, 2, 3, …), leads to a Hilbert space of spin functions of dimension d = (2s + 1)N. The resulting total spin quantum number S can take any value from the set {0 ≤ Smin, Smin + 1, …, Smax − 1, Smax = Ns}, and for each value of S, the associated spin projection quantum number M is restricted to 2S + 1 values obeying the condition −S ≤ M ≤ S. Total spin states |αSM〉 can then be construc- ted as eigenfunctions of the total spin operators S2 and Sz, such that S2 |αSM〉 = S(S + 1) |αSM〉, Sz |αSM〉 = M |αSM〉 (3) (the label α distinguishes between eigenfunctions that do not differ in S and M). It is now of great interest to determine for given N the dimension of Hilbert subspaces with given M, d(N,M), and with given S, f(N,S). The calculation of these numbers for arbitrary s has been 3 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 solved, in principle: The dimensions d(N,M) can be either read off from the expansion of their generating function (1 + x + … + x2s)N = Σ kk ak x (a2Ns-k = ak, d(N,M) = aM+Ns) [5] or calculated from binomial coefficients [6]. And then for S < Smax: f(N,S) = d(N,M = S) − d(N,M = S + 1) (f(N,Smax) = 1). The numbers f(N,S) satisfy an invariance condition with respect to the dimen- sion d of the complete Hilbert space: ΣS (2S + 1) f(N,S) = (2s + 1)N = d. It is remarkable that a recursive scheme for the calculation of d(N,M) has been devised already around 1800, long before the discovery of quantum mechanics and spin degrees of freedom, by L. Euler [7]. The recursive scheme for the calculation of f(N,S) generalizes the well-known branching diagram for the case s = 1/2 [8]. For arbitrary s and given N, the maximum value of d(N,M) is obtained for |M| = Smin. The value of S for which f(N,S) takes its maximum value is not known in general. But for s = 1/2 and given N, the maximum value of f(N,S) occurs at S 1/2peak = (Smax/2) (see Fig. 2), and the maximum of the weighted dimensions (2S + 1) f(N,S) is at S′peak = 21/2 Speak = (S 1/2max) . Fig. 2. Renormalized distributions of the number f(N,S) of spin states with total spin S for N spins s = 1/2 (0 ≤ S ≤ Smax = N/2, N = 10, 100, 1000). The maximum of f(N,S) is at Speak = N1/2/2 = (S 1/2max/2) for sufficiently large N. Left panel: Horizontal axis with linear scale for S/Smax. Right panel: Horizontal axis with logarithmic scale for S. 3.2 Combining the spin and space parts The combination of spin and space parts has to be done individually for every system of interest (see the examples in Sect. 2). However, a list of the possible types of electronic terms that can occur for a given sequence of systems can be straightforwardly derived from group- theoretical considerations. The following examples illustrate the situation for Li oligomers: LiN linear chain: Point group D∞h, N times (sσ, pσ)1, possible electronic terms: N even: 1,3,…( Σ +, Σ −, Σ + −g g u , Σu ) N odd: 2,4,…( Σ +g , Σ − + −g , Σu , Σu ) LiN ring: Point group Dnh, N times (s, p 1t) , possible electronic terms: N = 2k + 1 ≥ 3: 2,4,…(A′1, A′2, E′1, …, E′k) N = 2k ≥ 4 (k = 2l): 1,3,…(A1g, A2g, B1g, B2g, E1u, E2g, …, E(k-1)u) N = 2k ≥ 6 (k = 2l + 1): 1,3,…(A1g, A2g, B1u, B2u, E1u, E2g, …, E(k-1)g) LiN planar (lozenge-shaped cutout from close-packed layer): Point group D2h, N times (s, px, py)1, possible electronic terms: N even: 1,3,…(Ag, B1g, B2u, B3u) N odd: 2,4,…( Ag, B1g, B2u, B3u) For given N and S, the number of terms transforming according to a given irreducible repre- sentation Γ of the point group G of the system can be denoted as f(N,S,Γ). These numbers can be calculated recursively for a given sequence of systems (e.g. linear LiN chains, N = 2, 3, 4, 4 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 …). It seems to be possible to obtain recursively also all the energies EI, eq. (2), for all possible electronic terms of given N, from the energies EJ for all possible electronic terms seen for N−1. In this way, a sequence of densities of states of total energy E per monomer is generated that is likely to approach the one for the periodic system in the limit N → ∞. Acknowledgments Fruitful discussions with J. Schnack (Bielefeld University) are gratefully acknowledged. References [1] Dirac P A M 1930 The Principles of Quantum Mechanics (Oxford : Clarendon) § 14. [2] Weissbluth M 1974 Atoms and Molecules (New York : Academic) p 204. [3] Kramida A, Ralchenko Yu, Reader J and NIST ASD Team 2013 NIST Atomic Spectra Database (version 5.0), see http://physics.nist.gov/asd [2014, January 19]. [4] Guillaume C L, Gregoryanz E, Degtyareva O, McMahon M I, Hanfland M, Evans S, Guthrie M, Sinogeikin S V, Mao H-K 2011 Nature Physics 7 211. [5] The coefficients bk in (x−s + x−s+1 + … + xs−1 + xs)N = Σ kk bk x generate the numbers d(N,M) more directly (d(N,M) = bM), but this approach requires consideration of Pui- seux or Laurent polynomials (polynomials with fractional and/or negative powers), instead of just ordinary polynomials in x. [6] Bärwinkel K, Schmidt H-J and Schnack J 2000 J. Magn. Magn. Mater. 212 240. [7] Euler L 1801 Nova Acta Acad. Sci. Imper. Petropol. 12 47 (paper no. 709 in the Ene- ström index), also in Euler L (1992) Opera Omnia Ser 1, Vol 16 (Basel : Birkhäuser) p 28, see arXiv:math/0505425 for an English translation. [8] McWeeny R and Sutcliffe B T 1969 Methods of Molecular Quantum Mechanics (New York : Kluwer) p 67. 5 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Exploring the Properties of Complex Layered Tin Cluster Compounds M. Allisona, b, S. Liub, G. Stewartc, C. Lingb and T. Söhnel a a School of Chemical Sciences, University of Auckland, Auckland, New Zealand. b School of Chemistry, University of Sydney, NSW, Australia. c School of PEMS, UNSW@AFDA, Canberra, Australia. Solid oxide sintering reactions were used to prepare three new phases with the formula: Fe1+xMn3-xSi2Sn7O16 (x = 0.82, 1.65, 2.52). High resolution neutron and synchrotron powder diffraction investigations determined these to be isostructural to the iron rich Fe4Si2Sn7O16 phase; space group P-3m1 (164). Surprisingly, these phases show non-linear changes in unit cell parameters and magnetic behaviour depending on the specific transition metal content, which may indicate that each type of transition metal exhibits a unique set of behaviours that compete rather than cooperate with each other. 1. Introduction X-ray powder and neutron powder diffraction experiments have shown that all of the Fe1+xMn3-xSi2Sn7O16 (x = 0.82, 1.65, 2.52) phases form trigonal layered materials isostructural to the iron rich phase Fe4Si2Sn7O16 described by Söhnel et. al.[1]. All members of this solid state series form layered structures that can be viewed as a combination of a pseudo two dimensional layer of oxygen bridged FeSn6 clusters linked by SiO4 tetrahedra to a second two dimensional layer analogous to a tin substituted fayalite-like layer of MO6 octahedra with a transition metal to tin ratio of 3:1 through the SnO6 octahedra (Fig. 1). Ionically it can be broken down as [(Fe2+) 2+1(Sn )6](Fe2+)1(Sn4+)1(Si4+)2(O2-)16] with the solution of the 18 valence-electron rule for the Fe2+ cluster being: 6e- + 6×2e- = 18e- (octahedra). The predicted valence state of the Fe and Sn nuclei was confirmed with 57Fe and 119Sn Mössbauer spectroscopy [1]. The 57Fe Mössbauer measurements also showed the presence of both high spin and low spin Fe2+ in a ratio of 3:1, indicating the oxide layer sites are all high spin Fe2+. Magnetic measurements confirmed the predicted paramagnetic nature of this material dominating and there was no suggestion of magnetic ordering above 4.2 K. The novel structure of Fe4Si2Sn7O16 could however allow for substitution of other high spin nuclei into both of the transition metal crystallographic sites (the MSn6 cluster and the three transition metal sites in the oxide layer) and presents us a unique opportunity to investigate the engineering of magnetic effects into semiconducting materials by substituting each of the sites by different transition metals. These results will help us to develop a model for synthesis of complex multiferroic stannides to be used in devices with molecular level electronic applications.. Fig. 1. Crystal structure of Fe1+xMn3-xSi2Sn7O16. 6 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 2. Experimental Details Highly crystalline powders and single crystals were prepared by solid state sintering by combining the required metal oxide powders together with an excess of tin metal. The samples were places in corundum tubes and sealed under an air atmosphere in quartz tubes. The tubes were heated to 900 ºC over 48 hours followed by a controlled cooling to 750 ºC over a period of 200 hours. Synchrotron X-ray powder diffraction (SXRD) measurements were conducted on the powder diffraction beamline, 10-BM, at the Australian Synchrotron over a 6 to 86° 2θ range with a step size of 0.00375° 2θ, using the MYTHEN detector and the double crystal monochromator of Si(111) flat crystal pair. High resolution neutron powder diffraction measurements (NPD) were carried out using the Echidna instrument located at the OPAL reactor in Sydney, Australia, over a range of 2.75° to 162° 2θ with a step size of 0.125° 2θ at room temperature. Low temperature NPD measurements were carried out using the same parameters with an Oxford Instruments 12T cryomagnet at 5 K at 0 T and 1.8 K between 0 and 10 T using 2 hours per scan. All powder diffraction measurement data sets were refined with the Reitveld method using the FullProf suite software package [2]. 57Fe Mössbauer spectra were recorded with transmission geometry in a constant acceleration mode using a 57Co(Rh) source at room temperature in order to determine the valence and spin states of the iron nuclei. Magnetic susceptibility measurements were carried out using a Quantum Design Physical Properties Measurement System (PPMS) under a 1 T magnetic field from room temperature down to 2 K. 3. Results and Discussion 3.1 X-ray Powder Diffraction High-resolution synchrotron X-ray powder diffraction patterns were collected at the Australian Synchrotron between 6 and 86° 2θ at room temperature to determine the structure of the solid solution Fe1+xMn3-xSi2Sn7O16. These measurements confirmed the presence of new phases with a pattern near identical to that of the iron rich phase. However, all mixed Fe/Mn phases showed the presence of a significant amount of SnO2 contamination indicating an incomplete reaction and/or the oxidation of some of the final products and tin flux during the reaction cooling phase. Rietveld refinements show that as the transition metal ratio trends towards the Mn rich end of the series, there is an increase in the unit cell volume consistent with increasing replacement of Fe2+ with Mn2+ in line with Vegard's law [3]. However, a more detailed look at the cell parameters show that they increase slightly asymmetrically with the a/b parameters increasing more rapidly than that of the c parameter. This indicates that the oxide layer transition metal positions rather than the cluster positions were being preferentially substituted. That is be explained by the oxide layer transition metal positions being substituted with Mn as there are three potential transition metal crystallographic positions that lie in that plane rather than two positions which lie in the c plane. Synchrotron measurements from 303 to 823 K were also carried out which allowed us to determine the coefficient of thermal expansion for each of our phases (Fig. 2 and Table 1). These results show a decreasing coefficient of thermal expansion as the phases became richer in Mn, however, the most surprising results showed that the thermal expansion seen is asymmetric in the a/b plane with a value of almost double that of the c coefficient. Whilst this is commonly seen in most non-cubic materials, the large difference between the a/b plane and the c plane indicates that this behaviour is related to the layering that we have described in the crystal structure. 7 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Fig. 2. Cell parameter of Fe1+xMn3-xSi2Sn7O16 as a function of composition at room temperature (left) and temperature between 303 K and 823 K (right). Table 1. Calculated coefficients of thermal expansion. Formal Phase αL (a) αL (c) αV [Å3.K-1] Composition [Å.K-1] [Å.K-1] Fe Si Sn O 1.176x10-5 -6 -5 4 2 7 16 5.500x10 2.912x10 Fe MnSi Sn O 1.147x10-5 5.831x10-6 -5 3 2 7 16 2.888x10 Fe Mn Si Sn O 1.111x10-5 5.841x10-6 2.820x10-5 2 2 2 7 16 FeMn3Si2Sn7O16 1.094x10 -5 5.837x10-6 2.783x10-5 3.2. Neutron Powder Diffraction Neutron powder diffraction (NPD) measurements were carried out between 2.75° and 162° 2θ at room temperature in order to refine the occupation of the transition metal positions, the results of these measurements are shown in Table 2. Refinements of all samples were solved for the space group P-3m1. Except for the iron rich end member of the solid solution the calculated change in unit cell parameters were within agreement with those obtained from the synchrotron powder diffraction measurements. The elemental occupation refinement of the oxide layer and cluster layer transition metal positions revealed that there was no measurable amount of Mn contained in the Sn6 clusters. The occupational refinements did however show that the iron rich end member phase was iron and oxygen deficient but this has yet to be explained satisfactorily. For the mixed Fe/Mn phases refinements showed that a significantly lower than expected amount of Mn had been substituted into the oxide layer positions resulting in the phase formulas needing to be recalculated to: Fe1+xMn3-xSi2Sn7O16 (x = 0.82, 1.65, 2.52). Table 2. Unit cell parameter changes for formal and actual fractional change in Mn elemental composition. Formal Composition Fe% Mn% a/b [Å] c [Å] Vol. [Å3] (refined) (refined) Fe4Si2Sn7O16 100.00 0 6.8322(2) 9.1385(3) 369.42(2) Fe3MnSi2Sn7O16 79.50 20.50 6.8278(2) 9.1331(2) 368.73(2) Fe2Mn2Si2Sn7O16 58.75 41.25 6.8399(2) 9.1395(2) 370.28(2) FeMn3Si2Sn7O16 37.00 63.00 6.8550(2) 9.1477(3) 372.26(2) 8 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 3.3 57Fe Mössbauer Spectroscopy 57Fe Mössbauer spectra (Fig. 3) were recorded in order to determine the valence state and amount of Fe in each environment for the new phases. The measurements for all phases were resolved using MOSFIT and are resolved into two sets of doublets each phase that show two chemical environments of the iron nuclei present - the cluster and oxide layer positions. No sextets were observed indicating a lack of room temperature magnetic ordering and so these results are typical for paramagnetic Fe2+ nuclei [4]. Fig. 3. 57Fe Mössbauer spectra of Fe1+xMn3-xSi2Sn7O16 3.4. Magnetic Properties Magnetic susceptibility measurements were carried out down to 2 K to explore magnetic behaviours of the phases. These measurements show that the Mn richest member Fe1.48Mn2.52Si2Sn7O16 showed a transition to antiferromagnetic (AFM) ordering at 2.5 K, whilst all other phases remained paramagnetic above 2 °K. These low Curie temperatures are likely due to strong spin-orbit of the Fe2+ that prevents the Mn from ordering within the layer. Low temperature (1.8 K) neutron powder diffraction measurements were then carried out under magnetic fields on Fe1.48Mn2.52Si2Sn7O16 in order to determine the magnetic structures. These powder patterns showed new peaks at low angles – indicating the AFM transition, at low magnetic fields up to about 1 T. These magnetic peaks disappeared at fields above 2 T and the nuclear peaks increased in intensity, which could be a sign of a spin flip transition. However, work is still currently ongoing to explain these results. Acknowledgements We would like to thank Maxim Avdeev and the Bragg Institute (ANSTO) for the opportunity to carry out neutron experiments and AINSE for financially supporting this work. We also thank the Australian synchrotron for support with synchrotron experiments. Finally we also thank the University of Auckland for financial and academic support with this research. References [1] Söhnel T, Böttcher P, Reichelt W, Wagner F E 1998 Z. Anorg. Allg. Chem. 624, 708 [2] Rodriguez-Carvajal, J 1993 Physica B. 192, 55 [3] Vegard, L. 1921 Z. Phys. 5 17 [4] Recham N, Casas-Cabanas M, Cabana J, Grey C P, Jumas J-C, Dupont L, Armand M and Tarascon J-M 2008 Chem. Mater. 20 6798 9 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Freudenbergite – a New Example of Electron Hopping J. D. Cashiona, A. Lashtabegb*, E. R. Vancec, D.H.Ryand and J. Solanoe a School of Physics, Monash University, Melbourne, Victoria 3800, Australia, b Nanolytical, PO Box 21, The Gap, Brisbane, Qld 4061, Australia, cAustralian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia, d Physics Department, McGill University, Montreal, Québec H3A 2T8, Canada, e School of Chemistry, Monash University, Melbourne, Victoria 3800, Australia. Mössbauer spectra of freudenbergite samples with different composition have showed that although the Fe and Ti populate the octahedra randomly, Fe prefers the M(1) site over the M(2) site by approximately 1.3:1. Ti was able to accommodate mixed valence more easily than Fe, but some samples showed dynamic electron hopping in the Fe ions, which also affected the diffuse reflectance in the 400-800 nm region. 1. Introduction The monoclinic freudenbergite structure of Na Fe3+2 2Ti6O16 is composed of double sheets of edge sharing (Fe,Ti)O6 octahedra parallel to (001), with corner sharing along [100] to make a 3D structure [1]. The charge compensating Na+ ions are in the channels between the octahedra. We have recently [2] examined several samples of ferric and ferrous freudenbergite and showed that some samples of freudenbergite with mixed valence can undergo electron hopping, as evidenced by temperature dependence of the quadrupole splitting in their Mössbauer spectra. 2. Sample preparation Several samples of freudenbergite were prepared. Most were prepared from aqueous mixtures of NaNO3, Fe(NO3)3.9H2O, and Ti isopropoxide as previously described [2, 3]. The compositions were chosen to correspond to ferric freudenbergite, Na 3+2Fe 2Ti6O16 (1), to ferrous freudenbergite, Na2Fe2+Ti7O16, (2), with additional samples containing aluminium to try and achieve mixed valence. These had the composition Na2Al2-2xFexTi6+xO16, with x = 0.50, (3), and 0.25, (4), and were heated in argon. Both used 10% excess of Na and 10% excess of Ti to try to keep all the Fe in the freudenbergite. A further sample, (5), was prepared from the oxides of iron, titanium and aluminium in sodium hydroxide, with several sequences of sintering, pressing and grinding. This method produces a slightly reduced freudenbergite. SEM studies of the samples showed that those from the aqueous mixture method were all homogeneous. However, the solid state reaction sample was two-phase with the second phase being an iron-free alumina-based composition. All the samples were checked by XRD and SEM. The XRD showed that sample 1 had a few percent of the ferric brownmillerite Fe2TiO5, which has Mössbauer parameters very similar to those expected for freudenbergite [6]. Samples 2 and 3 had freudenbergite as the only iron-containing phase. These results were all confirmed by SEM. We note that in the previous report of our experiments on some of these samples [2], the sample labels 2 and 3 were reversed between the description of the preparation, which is correct, and the description of the spectra. Samples 2 and 3 in the preparation description in [1] correspond to the same samples in this report. 10 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 3. Results 3.1 Colour, composition and diffuse reflectance spectra We have made ten samples of freudenbergite with different compositions of Fe, Ti and Al in the octahedral sites to try and achieve ferric, ferrous and mixed ferric-ferrous systems. Heating was carried out in both air and argon. However, only two of the samples gave mixed valence and these two also exhibited electron hopping. The remainder were either pure ferric or pure ferrous. The cation charges in the octahedra should sum to 30, assuming a stoichiometric Na concentration, and even when compositions were chosen to try and force mixed valence, e.g. Na2Al2-2xFexTi6+xO16, which was all ferrous, or Na2AlFeTi6+xO16, which was all ferric, the mixed valence was accommodated by the Ti and not by the Fe. It was noticeable that the two samples with electron hopping were black (2) or blue- black (5) and the remainder were coloured through the gold-green-grey hues, except for the two ferrous samples of Na2Al2-2xFexTi6+xO16, with x = 0.50 and 0.25 (3 and 4), which were also black. As Coey [4] points out, materials which host spontaneous charge transfer are usually black, with a metallic lustre, but the converse, strong broadband absorption in the visible is not a guarantee of thermally-activated electron hopping. However, the colour of these last two samples raises the possibility that they are close to an electron hopping regime. We note that the Fe2+ - Ti4+ charge band absorbs in the red, so the crystals are usually blue. Diffuse reflectance spectra of powders is made up of light which has been reflected from the surface, and hence resembles the inverted specular reflectance spectrum, and light which has penetrated the sample before being scattered and hence contains the transmission spectrum. For a strong absorber, the former effect dominates. Diffuse reflectance spectra were taken of samples 1, 2 and 3 over the range 200-800 nm, using a Carey 1e spectrophotometer. Sample 1 showed a very rapid drop-off in reflected intensity between 500-600 nm (Fig. 1a), very similar to the spectra of the ferric α-, β- and γ-FeOOH polymorphs [5]. In contrast, the spectra of the other two samples (Fig. 1b, 1c) showed a continuous increase from 400 nm up to 800 nm, very similar to wüstite [5]. Wüstite is non-stoichiometric Fe1-xO, where the charge balance is maintained by a small percentage of the iron ions being ferric, so that it is mixed valence. Fig 1. Diffuse reflectance spectra of (a) 1, (b) 2 Fig. 2. Room temperature Mössbauer spectrum of 4. and (c) 3 11 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Absorption features in Fe-Ti materials are typically in the 400-2000 nm region, but assigning their origin is notoriously difficult [6]. This is particularly true when there are multiple possibilities, such as the homonuclear inter-valence transitions, Fe2+ ↔ Fe3+, Ti3+ ↔ Ti4+, or the heteronuclear Fe2+ + Ti4+ ↔ Fe3+ + Ti3+, and will not be attempted here. Fig. 3a. Mössbauer spectrum of 5 showing broadening Fig. 3b. Mössbauer spectrum of 5 in an applied field due to electron hopping. of 1.6 T showing modification of the electron hopping. 3.2 Mössbauer spectra The Mössbauer spectrum of 4 at room temperature is shown in Fig. 2. It has been fitted, similarly to that of 3 [1], to two ferrous doublets and a weak ferric doublet, all with Voigtian lineshapes, and the parameters for both samples are given in Table 1. The top blue line is the difference between the data and the fit in all the spectra. It is notable that the width of the inner doublet is approximately 2.5 times larger than that of the outer one. The Mössbauer spectrum of 5 at room temperature is shown in Fig. 3a, with the effect of the electron hopping in the ferrous component evident in the broadened right hand region. Each of the ferrous and ferric components have been fitted to two doublets with the inner ferrous doublet being noticeably broadened. The fit to the ferric doublets was very unstable, depending critically on the allowed width of the lines as characterised by the standard deviation, σ(Δ), of the Gaussian spread in the quadrupole splitting, Δ. However, the total ferric area remained quite constant at 66%. Fig. 3b shows 5 in a transverse applied field of 1.6 T. This modified the electron hopping so that each valence state was now able to be fitted to one unresolved sextet with a Gaussian spread of hyperfine fields. The mean hyperfine fields of 2.6 T for the ferric sites and 4.2 T for the ferrous sites are both significantly larger than the applied field, due to enhancement by the magnetization of the paramagnetic iron ions. Table 1. Fitted parameters to the room temperature Mössbauer spectra. Sample B Ferric sites Ferrrous sites T δ Δ, ε σ(Δ) B Area δ Δ, ε σ(Δ) B Area mm/s mm/s mm/s T % mm/s mm/s mm/s T % 3 0 0.23(3) 0.48(5) 0 0 3.2 0.99(1) 2.43(1) 0.21 0 55.3 1.00(1) 1.55(7) 0.50 0 41.5 4 0 0.19(2) 0.45(4) 0.02 0 5.5 0.96(1) 2.43(1) 0.18 0 53.1 0.96(1) 1.60(9) 0.55 0 41.4 5 0 0.39(1) 0.30(1) 0.10 0 37.7 0.97(1) 2.18(3) 0.17 0 12.8 0.40(1) 0.67(3) 0.16 0 27.6 0.87(3) 1.23(9) 0.63 0 21.9 5 1.6 0.35(1) 0.01(1) 2.4 73.1 1.10(4) -0.69(3) 4.2 26.9 12 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 4. Discussion and Conclusions In the fitting of 3 [1] and 4 (Fig 2), the isomer shifts of the weak ferric doublet in the two mainly ferrous samples were consistently lower than would be expected for an Fe3+ ion in an octahedral environment. Attempts to force them to a value in the region 0.35-0.38 mm/s produced a noticeably poorer fit. It was tentatively suggested in [1] that although the subspectrum could be due to an impurity, it was also possible that the parameters appropriate for a pure ferric freudenbergite had been altered by a change in lattice parameter. We now believe that the most likely explanation for the observed values is that the Fe3+ is in a tetrahedral environment, which does not exist in the freudenbergite structure. The samples were made with an excess of Na and a small amount of NaAl11O17 impurity was found in sample 3. All the compounds NaAlO2, Na7Al3O8, Na17Al5O16 and Na5AlO4 have Al in a tetrahedral coordination, with Fe3+ being able to substitute for Al3+ in all of them. Hence, we attribute the location of the Fe3+ to such a tetrahedral site and with only a few percent of the total iron being incorporated, it would be undetectable by XRD. It would thus seem that the ferric doublet in the spectra of 3 and 4 is not associated with the freudenbergite so we can accept the areas of the two ferrous doublets without needing any modification. Following Stähle et al. [7], we will assign the outer doublet to the more distorted M(1) site. We then get the ratio of the populations of the two sites, M(1)/M(2), to be 1.28 for 3 and 1.33 for 4, showing that although the filling of the octahedral sites by Fe2+ and Ti4+ appears to be random, in the sense that there is no clustering, there is a preference by the Fe2+ as the larger ion, for the larger M(1) site. Stähle et al. obtained a ratio of 1.22 for the M(1)/M(2) ratio for Fe3+ even though the ionic radius of Fe3+ of 0.064 nm is slightly smaller than that of Ti4+ at 0.068 nm. We noted before that 3 and 4 were the only two of the non-electron hopping Mössbauer samples which were black. However, their spectra showed that the inner doublet was very much broader than the outer one, as was the case in 5 and the diffuse reflectance of 3 showed an increase in the 400-800 nm region, similar that of the electron hopping 5. The raises the suggestion that electron hopping is close to occurring in 3 and 4 and furthermore that it is easier to achieve on the M(2) site, which is the less favoured site for Fe occupation. We must remember that the Fe concentration in the octahedra has dropped from 25% in ferric freudenbergite, to 6% in 3 and 3% in 4, with the Al substitution inhibiting electron movement. Our results also show that mixed valence is easier to achieve for the Ti ions than for the Fe ions, but it is not clear whether the Ti mixed valence states are static or dynamic. Acknowledgments We are pleased to acknowledge the support of Monash University for this work. We are grateful to Joel Davis for carrying out the SEM analysis. References [1] Ishiguru T, Tanaka K, Marumo F, Ismail M G M U, Hirano S and Somiya S 1978 Acta Crystallogr. B34 255 [2] Cashion J D, Lashtabeg A, Vance E R and Ryan D H 2013 Hyperfine Interact. 226 579 [3] Vance E R. Angel P J, Cassidy D J, Stewart M W A, Blackford M G and McGlinn P A 1994 J. Amer. Ceram. Soc. 77 1576 [4] Coey J M D 1984 Mössbauer Spectroscopy Applied to Inorganic Chemistry, Vol. 1 ed G J Long (New York: Plenum) p443 [5] Strens R G J and Wood B J 1979 Mineral. Mag. 43 347 [6] Burns R G 1981 Ann. Rev. Earth Planet. Sci. 9 345 [7] Stähle V, Koch M, McCammon C A, Mann U and Markl G 2002 Can. Mineral. 40 1609 13 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Tribute to CSIRO Scientists T.R. Finlaysona a School of Physics, University of Melbourne, Victoria 3010, Australia. In this invited presentation we pay tribute to the four CSIRO colleagues, Drs. John Dunlop, Tony Farmer, Gerry Haddad and Don Price, who lost their lives in the horrific crash of a Robinson R44 helicopter in March, 2013. The presentation briefly summarises the scientific careers of all four colleagues. Two of these scientists, Dunlop and Price, had been most enthusiastic supporters of and regular contruibutors to this Annual Condensed Matter and Materials Conference, since its inception in 1977, and their respective contributions are also included. 1. Introduction A couple of months ago, I received a call from Dr. Stephen Collocott, CSIRO, Lindfield, who had been invited by the Organising Committee for this Conference, to prepare and present a tribute to his four colleagues, Drs. Tony Farmer, Gerry Haddad, Don Price and John Dunlop, who lost their lives in the horrific crash of a Robinson R44 helicopter, near Panorama House, Bulli Tops, Wollongong, on 21st March, 2013. While Stephen shared the view of the Organising Committee that it would be most appropriate for such a tribute to be presented at the 2014 “Wagga” Conference, he knew at the time that he could not attend, so before accepting the invitation, he telephoned me to ask if I would present such an invited tribute. As I too felt it was a good idea on the part of the Organising Committee, I agreed and while I cannot claim to have known all four of Stephen’s CSIRO colleagues as well as he did, I am grateful to the Organising Committee for the opportunity to make this presentation on Stephen’s behalf. 2. Tony Farmer, 1944 - 2013 Anthony John Douglas Farmer was brought up in Adelaide and following a BSc (Hons) from the University of Adelaide, he completed a PhD in physics at that same university in 1970. “Post- doccing” followed, firstly overseas at York University in Toronto, Canada, and then a year at the University of Newcastle, NSW. Farmer started with the CSIRO in 1973 as a Research Scientist with the Division of Applied Physics, then based in the grounds of Sydney University. His research had already been in spectroscopy at very short wavelengths (in the vacuum ultraviolet range) and his initial project with the CSIRO was the development of a new method to make precise measurements of the spectral characteristics of light sources and detectors. He also collaborated with the US National Bureau of Standards on a successful project that eventually improved Tony Farmer (1944 – 2013) the accuracy of silicon photodiodes. From 1981, Farmer was involved in a new research area, thermal plasmas, in keeping with the increased emphasis on industrial physics of what was then the Division of Applied Physics. With Gerry Haddad, he published a series of benchmark papers on temperature measurements of electric arcs. Initially the measurements used spectroscopic techniques, which made use of the light emitted by the arc. 14 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 After that, to avoid some of the problems inherent in this approach, Farmer and Haddad were pioneers in the use of laser scattering - a more accurate approach, but one that presented extreme experimental difficulties, as the strength of the scattered signal is minuscule compared to that of the intense arc radiation. It was a tribute to Farmer’s skill and persistence that this work was successful. He led many industrial projects in the arc-physics area in the 1990s, two of which were outstanding successes. One was the development of a process to coat artificial hip joints with hydroxyapatite using plasma spraying, for Portland Square Pty Ltd. The second, in collaboration with the CSIRO’s Division of Manufacturing Technology and SRL Plasma, was on the development of the PLASCON waste treatment process to allow destruction of ozone- depleting substances. Twelve PLASCON plants, most of which are still operating, have been constructed around the world. For this work, Farmer was awarded, together with two CSIRO colleagues, the 2008 Alan Walsh Medal for Service to Industry, by the Australian Institute of Physics (AIP). Shortly before his untimely death, he had taken on the position of Editor of the “house journal” of the AIP, Australian Physics, but unfortunately only two issues of the journal (Jan-Feb and Mar-Apr, 2013) resulted from this voluntary involvement with the Institute. Farmer was promoted to Senior Principal Research Scientist (Level 8) in 1998. In 2000, he took on the leadership of the sub-surface radar project. This team made significant advances in the understanding of the interaction of electromagnetic waves and the geophysical environment, and they developed borehole electromagnetic probes for geophysical measurements while drilling, in coal mines. This technology was adapted for environmental applications including measuring moisture, salinity and soil quality. This team also developed SiroPulse, a sub-surface radar system designed for security counter-measures applications, which received wide acceptance within Australia, New Zealand and US government agencies. In 2005, Farmer became a Theme Leader in CSIRO’s Industrial Physics Division, and from 2008 was Deputy Chief of Operations at CSIRO’s Materials Science and Engineering Division. He retired in 2010, but continued as an Honorary Fellow, working in the area of high-power ultrasonic processing. 3. Gerry Haddad, 1941 - 2013 Gerald Neil Haddad hailed from Mount Gambier in South Australia but completed his secondary schooling at Adelaide High School after winning a bursary to attend that institution. There followed a BSc (Hons) and a PhD in the Physical Sciences from the University of Adelaide in 1968. He then worked at the University of Adelaide, Culham Laboratory in the UK, the University of Nebraska and the University of Oklahoma and he returned to Australia as a Research Fellow at the Australian National University. His CSIRO career began in 1982 when he was recruited as a Senior Research Scientist with the Division of Applied Physics at Lindfield. He was an outstanding experimentalist, with a real talent for the engineering and technical development of new Gerry Haddad (1941 – 2013) systems. Less than a year after starting at the CSIRO, his group leader described him as being “the best experimentalist I have ever worked with.” Haddad led a number of projects in the gas-discharge field, ranging from fundamental studies of the interactions of electrons with molecules, through spectroscopic measurements of welding arcs to the design of high-power 15 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 arc plasma reactors for mineral processing for Australian companies, including a facility for the dissociation of zircon sands to produce zirconia for ICI. The success of his work contributed strongly to the rapid development of the CSIRO plasma group’s international reputation. The landmark papers of Haddad and Tony Farmer on the temperature measurements of electric arcs, which are cited in leading textbooks on arc welding, showed that the approximate properties of welding arcs can be predicted theoretically assuming “local thermal equilibrium.” This made the development of sophisticated computer codes for the prediction of weld properties possible for almost any industrial configuration, and these have been adopted worldwide by companies and universities. Haddad earned rapid promotion as a scientist, reaching Senior Principal Research Scientist (Level 8) in 1989. In 1988, Haddad decided to pursue a career in research management and took a position as Program Manager in plasmas, thin films and thermometry in the Division of Applied Physics. Nevertheless, for many years he remained strongly involved in the research and development of the plasma group, often taking the opportunity to “get his hands dirty” in the lab. The plasma researchers who followed, remained indebted to him for the experimental facilities he had developed. Haddad’s success as a research manager and leader echoed that of his research career. Following the formation of CSIRO Telecommunications and Industrial Physics, he was appointed as a Portfolio Manager in 1996, Deputy Chief in 1999 and Chief in 2003. He was also Chief of CSIRO Industrial Physics from its formation in 2004 until he retired in 2007. After retiring he took a position at Standards Australia and was there until his second retirement in 2012. 4. Don Price, 1945 - 2013 Donald Carruthers Price was born in Dumfries, Scotland, where his parents had been taking part in the British war effort. After the war, the family returned to Australia and settled in Melbourne. Don’s first degree was at the “new” (at least then) Monash University and this was followed by a PhD in which he applied Mössbauer spectroscopy to the measurement of hyperfine field distributions at the 119Sn nuclei in ferromagnetic, transition-metal alloys, under the supervision of the late Professor Bob Street. There followed a series of post-doctoral fellowships at the University of Manitoba, Canada, the University of Liverpool, UK, the Research School of Physical Sciences at the Australian National University and the Royal Military College, Duntroon, where his prime research interest was again focussed on the Mössbauer effect. He then worked on the detection Don Price (1945 – 2013) of breast cancer using ultrasound at the Queensland Institute of Technology. It was in the field of ultrasonics that in 1982, he was appointed to the CSIRO, Division of Applied Physics in Lindfield, as a Research Scientist, and where he expanded his research to include both measurement techniques and materials properties. He went on to become Discipline Leader (equivalent to a Research Group Leader) for Acoustics and Ultrasonics, and held leadership positions, including as a member of Divisional Management teams. He was promoted to Senior Principal Research Scientist in 1993. Price’s work on modelling the behaviour of ultrasonic waves in composite materials led to the development of instrumentation for the non-destructive testing of aerospace structures. Modern aeroplanes are no longer just made of metal riveted together, but rather materials such as carbon fibres glued together, and Price worked out how to test the joins ultrasonically 16 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 without destroying them. He performed outstanding research in this area in collaboration with Boeing for many years. He was instrumental in the development of a collaboration with NASA that resulted in the Ageless Aerospace Vehicle (AAV) project, for which he was project leader. The project focused on intelligent active sensing systems for structural health management in aerospace vehicles, though the principles had much broader applicability. Price also led the tube eccentricity measurement project, which developed an online system to measure the wall thickness and eccentricity of extruded copper tube using high- frequency ultrasound. The system was installed in the production line at Metal Manufactures Ltd., Port Kembla Tube and Fittings Mill, where it is used to sort tubes for subsequent processing, and continues to provide valuable results. Beyond science, Price contributed greatly to the Division. As a member of the management teams of CSIRO Telecommunication and Industrial Physics, he was instrumental in setting research directions and increasing the awareness of the Division’s science achievements in the broader community. He played a major role in internal Divisional review processes, and in managing the Division’s contribution to external reviews of its science. He was responsible for coordinating and leading the work of various research teams, and managed and developed valuable external collaborations. He was also a great mentor to students, regularly hosting students from both Australia and overseas. He was very active in the Australian physics community, being a regular attendee at AIP events. In addition, for a number of the issues of Australian Physics, prior to Don’s untimely death, he had been preparing a column for the journal, reporting on topical issues of physics research and development, internationally, that had “caught his eye” in the literature. Don was conscientious and generous, frequently making sacrifices for the benefit of his colleagues. He was quietly spoken, with a wry sense of humour. He was never comfortable with self-promotion, preferring the quality of his work to speak for itself. Following his retirement in 2009, Price continued with the Division at Lindfield as an Honorary Fellow. My personal friendship with Don Price began in his early years as a PhD student at Monash University where he was also an active sportsman, and particularly excelled at baseball. In his later years he took to long-distance running and could boast a best time for the marathon of 2 hrs 36 mins. He has been an active contributor to this conference throughout its history and from the records, I have counted a total of 21 “Wagga” papers which he authored or co-authored and 17 attendances at “Wagga” conferences. 5. John Dunlop, 1946 - 2013 John Burton Dunlop’s life began in Wigan, England and following an English Grammar School education, he graduated with a Bachelor of Science with Honours and a PhD in Physics in 1972, from Imperial College, London. His research was concerned with the magnetic properties of hard magnetic materials. John had research fellowships at the University of Sheffield in England and at the University of Genoa, Italy, prior to joining the CSIRO in 1976 as a Research Scientist with the National Measurement Laboratory, then in the grounds of Sydney University. Subsequent changes within CSIRO meant that he worked in CSIRO Applied Physics, CSIRO Telecommunications and Industrial Physics and, later, CSIRO Materials Science and Engineering. He was John Dunlop (1946 – 2013) promoted to Principal Research Scientist (Level 7) in 1987 and retired in 2008. 17 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 In his early years at the CSIRO, Dunlop’s research focused on the magnetic properties of transition metal alloys and glassy metals. With the latter he developed techniques for their fabrication, which involved rapid solidification from the molten phase. However, the greater part of Dunlop’s career was devoted to the study of the rare-earth permanent magnets and their application in devices, in particular, electrical nachines. He was part of the team that developed a pilot plant for the production of the rare-earth magnet neodymium-iron-boron. This was as an extremely successful project, and resulted in the formation of a spin-out company, Australian Magnet Technology. John was always keen to see his science translated into real-world applications, and this was achieved many times with projects conducted through the Sydney Electrical Machines, Controls and Applied Magnetics (or SEMCAM) consortium and with industrial partners that included, for example, General Motors Holden and Electrolux. These more commercial activities were balanced by a fundamental interest in the magnetism of rare-earth metals, and related alloys, and Dunlop and his fellow team members were credited with the discovery of the so-called ‘‘Fifth Family of Permanent Magnets’’, the 3:29 alloys. He also contributed to the development of novel methods for producing titanium-based alloys. However, he was not comfortable seeking rewards for himself, he preferred instead to perform useful work for his colleagues and collaborators and for Australian companies. He was highly respected for his deep scientific knowledge, his cheerful willingness to assist and provide practical advice to other researchers, and his friendly and generous nature. Dunlop was also very active in the Australian solid-state physics community. His efforts, with close colleagues, saw the establishment, in 1977, of the Australian Institute of Physics Solid State Physics Meeting which, on account of its residential location in Wagga Wagga, NSW, became known simply as “Wagga.” A later name change to ANZIP Solid State Physics Meeting evolved from the participation in and hosting of this annual conference by New Zealand groups and later still, further name changes to “Condensed Matter Physics” and “Condensed Matter and Materials” reflected changes in fashion of the day. But it remains the “Wagga Meeting” and the records show that of the 37 “Wagga” conferences up to and including “Wagga 2013”, (L→R): Stephen Collocott, John Dunlop, Charles Johnson and Don Price, at “Wagga John Dunlop had attended 29 of them and had 2012.” authored or co-authored 33 “Wagga” papers. 6. Conclusion In conclusion, may I say that at a personal level I must pay tribute to both John Dunlop and Don Price for their active involvement in what has become an aspect of “Wagga” conferences, the Trivia Night. John, in particular, was a master at setting Trivia Quiz questions and recently both John and Don served as Trivia judges on the night itself. They will be sadly missed from this year’s quiz night. May I invite you all to stand and observe a (L→R): John Dunlop, Don Price and Trevor minute’s silence, to enable those of you who knew Finlayson running the Trivia Night at “Wagga any of Tony Farmer, Gerry Haddad, Don Price or 2013.” 18 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 John Dunlop, to reflect on your own personal experiences in interacting with them professionally and/or socially. Acknowledgments The assistance, particularly of Dr. Stephen Collocott, and also that of Dr. Tony Murphy, both of CSIRO, Lindfield, in providing most of the information concerning their colleagues, presented in this invited tribute is gratefully acknowledged. 19 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Exploring the Structural and Magnetic Phase Transition of Cu1-xCoxSb2O6 H.-B. Kanga C.D. Lingb and T. Söhnela a School of Chemical Sciences, University of Auckland, Auckland, New Zealand. b School of Chemistry, University of Sydney, Sydney, Australia. The system Cu1-xCoxSb2O6 has been investigated using sealed-tube and synchrotron X-ray powder diffraction, neutron powder diffraction and single crystal neutron diffraction. An orthorhombic phase is proposed between the previously established tetragonal and monoclinic phases for x < 1. In addition, evidence is presented for a possible ferroelastic phase transition in Cu0.3Co0.7Sb2O6 single crystals at low temperatures. Magnetic susceptibility measurements confirm antiferromagnetic ordering across the complete solid solution series. 1. Introduction CuSb2O6 has been the most intensively studied compound in the ternary Cu-Sb-O system since the high transition temperature (Tc) superconducting materials based on copper oxides were found by Bednorz and Müller in 1986 [1]. It is reported to undergo a second- order phase transition from a tetragonal to a monoclinic distorted trirutile structure between 100 and 130 °C [2]. The transition is thought to be driven by a Jahn-Teller distortion on Cu2+ (a d9 ion, stabilising square-planar geometry). This square lattice cupric oxide layer is similar to that found in the two-dimensional Heisenberg antiferromagnet (HAF) La2CuO4, [3, 4]; however, the magnetic behaviour of CuSb2O6 is considered to be an S=½ one-dimensional Heisenberg antiferromagnet with strong anisotropy above 20 K [2]. The difference between these two compounds can be understood by applying and combining the total energy and tight-binding model calculation results [5]. A sudden decrease in magnetic susceptibility at 8.6 K indicates antiferromagnetic long-range ordering due to inter-chain interactions [2], and has recently been revealed as a crossover behavior from S = ½ one-dimensional HAF to a three-dimensional HAF [8]. CuSb2O6 also exhibits a spin-flop transition at 2.2 T and 5 K, leading to greatly enhanced magnetic moments [6]. CoSb2O6 also crystallizes in the tetragonal trirutile structure (Fig. 1) and exhibits two-dimensional HAF behaviour with a broad transition at about 35 K [7]. The magnetic structure of CoSb2O6 has only been refined against neutron powder diffraction (NPD) data. Two alternative models for antiferromagnetic ordering have been proposed, which are indistinguishable by NPD [7]. This study concerns the doping of divalent Co onto the A site of CuSb2O6, which is of interest for two reasons. Fig. 1. The structure of Firstly, a direct second-order phase transition from a CoSb2O6 as refined against tetragonal to a monoclinic trirutile ought not to be possible. A single crystal neutron Laue systematic reduction in symmetry, as shown in Bärnighausen diffraction data (Co: blue, trees, would require the existence of an orthorhombic Sb: brown, O: red). 20 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 intermediate phase. Secondly, this doping changes the magnetic behaviour from a S=½ one- dimensional Heisenberg antiferromagnet to a two-dimensional Heisenberg antiferromagnet. The main aim of this study is thus to investigate the structural and magnetic behaviour of the solid solutions (Cu1-xCox)Sb2O6 in combination with very detailed investigations of the phase transition of CuSb2O6. 2. Sample preparation Stoichiometric mixtures of CuO, Co3O4 and Sb2O3 powders were placed in corundum crucibles and heated to 960 °C for 36-48 hours in a muffle furnace prior to quenching in air yielding in phase pure powders. Powder samples were initially characterized by X-ray powder diffraction (XRD) using a sealed-tube source (Panalytical Empyrean, monochromated Cu Kα radiation, 10 - 80° 2θ range). Synchrotron X-ray powder diffraction (SXRD) data were subsequently collected on the Powder Diffraction beamline (10-BM) at the Australian Synchrotron over a 6 to 86° 2θ range with a step size of 0.00375° 2θ, using the MYTHEN detector and the double crystal monochromator of Si(111) flat crystal pair (λ = 0.774235 Å, calibrated with LaB6). Single crystal neutron Laue diffraction data were collected on the instrument Koala at the OPAL research reactor, Lucas Heights, Australia. Complete single crystal data sets were collected at 100 K, 25 K and 5 K (well above, close to, and below the magnetic ordering temperature respectively) for each crystal, comprised of 0.5 h measurements taken at 15 different orientations. Magnetic susceptibility data from room temperature to 2 K were collected on a Quantum Design Physical Properties Measurement System (PPMS) in zero-field-cooled mode using a 1 T magnetic field. 3. Results 3.1 X-ray Powder Diffraction Analysis Sealed-tube XRD data were collected from samples prepared at 960 °C and quenched in water. Preparations using slower cooling rates from high temperatures down to room temperature could not preserve the 960 °C structure, the sample composition was identical in all cases independent of cooling rate. At room temperature, a wide two-phase region was observed from x = 0.2–0.5, involving a Cu-rich monoclinic phase and a Co-rich tetragonal phase. For the monoclinic Cu-rich component, all the lattice constants increase from x = 0– 0.15 (Fig. 2). Between 0.2 and 0.5, the lattice constants a and b are relatively constant, while c decreases slightly. The tetragonal phase could be Rietveld-refined starting from x = 0.2, with the lattice constant a increasing and c decreasing from x = 0.2–1. Despite the observed doping trend and two-phase region, it was not possible to fully interpret the phase behaviour of the system based on these XRD data, due to difficulties in refining two phases distinguished only by a small monoclinic distortion (~1 °). Fig. 2. Lab X-ray powder diffraction patterns of Cu1-xCoxSb2O6 solid solutions (left) and lattice constants distribution of Cu1-xCoxSb2O6 solid solutions (right). 21 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 3.2 High Resolution Synchrotron Powder Diffraction Analysis SXRD data were used to analyse the two-phase region in more detail. These data confirmed the existence of a two-phase region at room temperature. At 200 °C, we had expected to observe a complete solid-solution in the tetragonal phase, as the tetrgonal- monoclinic phase transition of CuSb2O6 is observed around 100 °C to 130 °C; however, the SXRD data indicate that this is not the case (Fig. 3). An orthorhombic phase is clearly identifiable on the Cu-rich side, including undoped CuSb2O6. The proposed space group is Pnnm, which is the only possible space group according to Bärnighausen trees. A second order transition from the tetragonal modification (P42/mnm) to the monoclinic modification (P21/n) can be related via translationsgleiche group-subgroup relations but only via an orthorhombic modification (Pnnm): P42/mnm -t2→ Pnnm -t2→ P21/n The structural distortion in Pnnm is very subtle, even using synchrotron radiation. Nevertheless, the diffraction peaks clearly show different behaviours on the Cu-rich and the Co-rich sides of the solid solution, indicating the presence of two different structural modifications (Fig. 3). No additional peaks were observed that could indicate a superstructure ordering of Cu and Co. The orthorhombic phase was observed at 200 °C for the entire Cu1- xCoxSb2O6 solid solution except CoSb2O6. Even at 500 °C, we still observe different symmetries on the Cu-rich and Co-rich ends of the solid solution. The phase transition from tetragonal to lower symmetry can be observed for compositions of x = 0–0.3 (Fig. 3). All these transitions were fully reversible. Fig. Fig. 3. SXRD patterns of Cu1-xCoxSb2O6 solid solutions at 200 °C (left) and Rietveld refinement of synchrotron powder diffraction data of Cu0.3Co0.7Sb2O6 at 500 °C (right). 3.3 Single Crystal Neutron Laue Diffraction Single crystal Laue diffraction data were collected for CuSb2O6, Cu0.3Co0.7Sb2O6 and CoSb2O6 single crystals. The trirutile structure of CoSb2O6, which could be refined against these data, is shown in Fig. 1. All CuSb2O6 crystals were twinned and could not refined successfully. For Cu0.3Co0.7Sb2O6, after the initial appearance of diffuse scattering below room temperature, a peak splitting could be observed on decreasing the temperature from to 100 K and then 5 K (Fig. 4). This peak splitting was reversible on increasing the temperature, which suggests a ferroelastic phase transition. 22 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Fig. 4. Single-crystal neutron Laue diffraction pattern of Cu0.3Co0.7Sb2O6 3.4 Magnetic Measurements The magnetic susceptibilty behaviour of Cu1-xCoxSb2O6 from x = 0.3 and 0.7 is similar to that of CoSb2O6 (Fig. 5), confirming antiferromagnetic ordering across the entire solid solution. The transition is broad, as reported for the pure Co sample (x = 1) [7]. The composition at x = 0.1 shows behaviour more akin to that of the pure Cu sample (x = 0). The change in Néel temperatures is small for x = 0–0.7 (13 K difference) but a significant jump is observed to x = 1 CoSb2O6 (13 K difference, Fig. 5 inset). It appears that all these compounds except the Cu-rich samples are likely to exhibit 2D HAF behavior, with magnetic susceptibility decreasing in accordance with the reduced moment of Cu(II) compared to Co(II). Fig. 5. Magnetic susceptibility data (x = 0, 0.1, 0.3, 0.7 and 1, from the bottom to top) and Néel temperatures for Cu1-xCoxSb2O6. Acknowledgments The authors thank Dr Justin Kimpton at the Australian Synchrotron and Drs Ross Piltz and Maxim Avdeev at the Australian Nuclear Science and Technology Organisation (ANSTO) for their advice and assistance in the collection of diffraction data. They also thank the Australian Institute of Nuclear Science and Engineering (AINSE), The University of Auckland and The University of Sydney for funding. References [1] Bednorz J G and Müller K A 1986 Z. Phys. B64 189 [2] Prokofiev A V, Ritter F, Assmus W, Gibson B J and Kremer R K 2003 J. Cryst. Growth 247 457 [3] Nakua A, Yun H, Reimers J N, Greedan J E and Stager C V 1991 J Solid State Chem. 91, 105 [4] Sandvik A W and Scalapino D J 1995 Phys. Rev. B. 51 9403 [5] Kasinathan D, Koepernik K and Rosner H 2008 Phys. Rev. Lett. 100 237202 [6] Nakua A M and Greedan J E 1995 J. Solid State Chem. 118 199 [7] Reimers J N, Greedan J E, Stager C V, Kremer R 1989 J. Solid State Chem. 83 20 [8] Rebello A, Smith M G, Neumeier J J, White B D and Yu Y-K. 2013, Phys. Rev. B 87 224427. 23 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Identifying Further Inelastic Neutron Crystal Field Transitions in ErNiAl4 G.A. Stewarta, W.D. Hutchisona, Zahra Yamanib, J.M. Cadogana and D.H. Ryanc a School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, Australian Defence Force Academy, PO Box 7916, ACT, BC 2610, Australia. b Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, ON K0J 1J0, Canada. c Physics Department, McGill University, Montreal, Quebec, H3A 2T8, Canada. Interim results are presented for a thermal INS project seeking to identify further crystal field transitions for the J = 15/2 ground state of Er3+ in ErNiAl4. Previously reported transitions at 3, 7.4 and 11.3 meV are confirmed and a possible two further transitions have been located at 14.4 and 18.2 meV. 1. Introduction The orthorhombic, intermetallic series RNiAl4 (R = rare earth) exhibits interesting magnetic behaviour [1-2], including the potential for low temperature, inverse, magnetic cooling [3]. Given that the RNiAl4 magnetism is associated solely with the R sub-lattice and is influenced strongly by the local crystal field (CF) interaction at the R-site, it is important that the CF interaction is characterised. Thermal neutrons are used here to extend a previous cold neutron inelastic neutron scattering (INS) investigation [4] of the crystal field (CF) transitions at the single Er3+ site in ErNiAl4. 2. Experimental details Substantial amounts of ErNiAl4 (34.8 g) and YNiAl4 (26 g) were prepared as a set of smaller 1-2 g lots via repeated argon arc melting followed by vacuum annealing for 5-6 d at 1050 °C. X-ray powder diffraction was used to identify the acceptable single-phase lots. All neutron scattering measurements were performed on the C5 polarised triple-axis spectrometer at CNBC in Chalk River, Canada. The INS spectra were accumulated with a final scattering energy of Ef = 14 meV. 3. Results Neutron scattering measurements were performed using both the elastic and inelastic modes of operation for the C5 spectrometer. 3.1 Elastic neutron scattering Neutron diffraction patterns (λ = 2.37051 Å) were recorded for ErNiAl4 at 290 K and 3.9 K (Fig. 1). Rietveld analysis of the 3.9 K pattern (well below TN = 5.8 K) using FullProf software [5] yielded an incommensurate sinusoidal structure with a propagation vector of [0.191 1 .0 0.038] and a local moment amplitude of µ(Er3+) = 7.0 µB aligned with the c-axis (Fig. 2). The propagation vecto r is similar to that reported earlier [6] although the moment is about 16% smaller (cf 8.3 µB). Recent 166Er-Mössbauer results [7] rule out a spread in the local Er moment so that a square wave modulation is more appropriate. However, in subsequent reconsideration of the Rietveld analysis, it has proved difficult to identify the weak higher harmonics. In order to confirm the magnetic origin of the reflection at Q = 2.3134 Å-1 (2θ ≈ 51.75°) its intensity was monitored as a function of temperature using polarised neutrons (p // Q) with both spin flip (SF) and non spin flip (NSF) detection. From Fig. 3, it is evident that the net 24 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnetic R(Bragg) = 8.1 reflections R(F) = 3.9 R(mag) = 7.4 2θ (deg) Fig. 1. Neutron diffraction pattern of ErNiAl4 recorded at 3.9 K (λ = 2.37051 Å). The three rows of Bragg position mark ers are (top) nuclear, (middle) incommensurate mag netic, and (bottom) small component of Er2O3 impurity. b Fig. 2. Incommensurate sinusoidal magnetic a structure fitted to the neutron diffraction pattern for ErNiAl4 at 3.9 K. For simplicity, the Ni and c Al atoms are ignored and just one orthorhombic crystallographic cell is shown. magnetic intensity (SF - normalised NSF) drops to zero above the ordering temperature. The maximum of the differentiated net signal (upper inset in Fig. 3) yields an ordering temperature of 6.5 K, in close agreement with the bulk specific heat value of TN = 5.8 K [6]. 700 200 100 500 dNdT 0 TN ≈76.57K Fig. 3. Temperature dependent intensity !100 of the ErNiAl4 magnetic reflection at 300 SF 4 6 8 10 2θ = 51.75° (λ = 2.37051 Å): SF = spin flip, NSF = non spin flip, and NSF SF7! NSF NSFnorm indicates NSF normalised to SF norm in the temperature range 7.5 < T < 10 K. 100 0 4 8 12 !100 0 2 4 6 8 10 Temperature7(K) 25 Counts Counts Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 3.1 Inelastic neutron scattering Unpolarised INS spectra were recorded for ErNiAl4 at 10 K with four different scattering vectors, Q, over the energy ranges of 0 - 25 meV (Q = 1.2 Å-1), 0 - 41 meV (Q = 2.7 Å-1), 0 - 50 meV (Q = 3.0 Å-1), and 20 - 50 meV (Q = 5.2 Å-1). As shown in Fig. 4, strong transitions were observed at 3.08(2), 7.53(2) and 11.6(1) meV. These energies are in excellent agreement with those observed previously using cold neutrons [4] and the evident Q-independence confirms that they are associated with “magnetic” CF transitions. However, the objective of these new measurements was to identify additional CF transitions at higher energies. From Fig. 5 the INS spectra in the range of 15 - 50 meV are seen to be of relatively low intensity with broader features that are believed to be associated with phonon transitions. Because of this, additional INS spectra were recorded for non- magnetic YNiAl4 whose Y3+ ion’s ground S-state is not subjected to a CF interaction.! 15 00 200 Q2=23.02Å$1 Er Q1=15.21Å!1 10 00 150 100 Y 500 50 0 1500 $3 0 3 6 9 12 15 Er -Y? ? norm 2.72Å$1 0 1000 !50150 10 20 30 4!01 50 500 Neutron1energy13lo.s0s11(ÅmeV) 100 Er 0 1500 $3 0 3 6 9 12 15 50 3.08(2) Y 1.22Å$1 meV Er -Y 1000 norm 7.53(2)2meV 0 500 11.6(1)2meV !50150 10 20 30 40 50!1 0 Neutron1energy12lo.s7s11(ÅmeV) $3 0 3 6 9 12 15 100 Er Neutron2energy2loss2(meV) Fig. 4. The 0 < E < 15 meV region of the INS 50 Y spectra recorded for ErNiAl4 at 10 K with scattering vectors of Q = 1.2, 2.7 and 3.0 Å-1. The solid lines Er -Ynorm are fitted Pseudo-Lorentzian peaks superimposed on 0 a linear background. 11.6 15.4 18.21meV 34.21meV? !50 10 20 30 40 50 Neutron1energy1loss1(meV) Fig. 5. The 10 < E < 50 meV region of INS spectra recorded at 10 K with scattering vectors of Q = 2.7, 3.0 and 5.2 Å-1. The data for ErNiAl4, the scaled up data for YNiAl4, and their subtraction are indicated by the labels “Er”, “Y” and “Er - Y”, respectively. The scaling of the YNiAl4 spectra employed a multiplying factor of the form A + B*E (where E is the neutron energy loss) and the spectra were smoothed prior to their subtraction. 26 Counts Counts Counts Counts Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The approach taken was to scale up the intensities of theYNiAl4 spectra so that their broad features matched as closely as possible those of their ErNiAl4 counterparts. To this end, it was found useful to employ a scaling factor that increased linearly across the spectra. The scaled YNiAl4 spectra were then su!btracted from the ErNiAl4 spectra in an effort to identify the true CF transitions for ErNiAl4. Based on this approach, possible additional CF transitions are located at 14.4 and 18.2 meV as indicated by the superimposed triangular peaks in Fig. 5.!A further candidate is observed at 34.2 meV with Q = 2.7 Å-1 but it is no longer evident for Q = 3.0 and 5.2 Å-1. Conclusions and on-going work Valuable information has been gained regarding the incommensurate magnetic phase of ErNiAl4 below TN = 5.8 K and likely additional CF transitions have been located at 14.4 and 18.2 meV. It is hoped that further polarised neutron beam INS measurements currently being conducted on the C5 spectrometer at Chalk River will ultimately separate the remaining weak CF transitions out from the broad phonon signals via the comparison of SF and NSF spectra. Acknowledgments The CNBC is gratefully acknowledged for time allocated on the C5 spectrometer and Vernon Edge is thanked for his valuable assistance with the specimen preparation. References [1] Stewart G A, Hutchison W D, Edge A V J, Rupprecht K, Wortmann G, Nishimura K and Isikawa Y 2005 J. Magn. Magn. Mater. 292 72. [2] Hutchison W D, Goossens D J, Whitfield R E, Studer A J, Nishimura K and Mizushima T 2012 Phys. Rev. B 86 014412/1-5. [3] Li L, Nishimura K and Hutchison W D 2009 Solid State Commun. 149 932. [4] Saensunon B, Stewart G A, Gubbens P C M, Hutchison W D and Buchsteiner A 2009 J. Phys.: Condens. Matter 21 124215; Corrigendum 2010 J. Phys.: Cond. Matter 22 029801. [5] Rodriguez-Carvajal J 1993 Physica B 192 55. [6] Hutchison W D, Goossens D J, Saensunon B, Stewart G A, Avdeev M and Nishimura K 2007 Proceedings of the 31st Annual Condensed Matter and Materials Meeting, 6-9 Feb., Wagga Wagga. [7] Ryan D H, Lee-Hone N and Stewart G A 2013 Solid State Phenom. 194 84. 27 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Structural Investigation of Tungsten Bronze Type Compounds in the Relaxor Ferroelectric Sr3Ti1-yZryNb4O15 System T. A. Whittlea and S. Schmida a School of Chemistry, The University of Sydney, NSW 2006, Australia. Compounds in the Sr3Ti1-yZryNb4O15 system were investigated by synchrotron X-ray powder diffraction. New structural models are proposed for all compositions across the series. These models include a doubled unit cell and orthorhombic symmetry. A solid solution was found to persist across the composition range from y = 0 - 1. Variable temperature studies reveal phase transitions from orthorhombic to tetragonal symmetry on heating. 1. Introduction Compounds of the general formula A1A22B1B24O15 have been shown to form with a tungsten bronze type structure. The tungsten bronze structure consists of a network of corner sharing BO6 octahedra with A cations located in interstitial sites. The A1 site is a 12- coordinate site and the A2 site is a larger 15-coordinate site. Combined with a smaller, unnocupied, 9-coordinate C site, these A and C sites form channels through the structure running along the c-direction. The compositional and structural flexibility of tungsten bronzes allows for a variety of A and B site cations as well as cation mixing in these sites. A site cations tend to be large alkali, alkaline earth or Pb2+ cations. The B sites are occupied by smaller transition metal cations such as Ti4+, Zr4+, Ta5+ and Nb5+. Tungsten bronze type compounds have been shown to display technologically important properties, finding use in volatile memory, actuators, infrared radiation detection as well as in optical applications amongst others [1-4]. Sr3TiNb4O15 and Sr3ZrNb4O15 are compounds which form with tungsten bronze type structures. Both have been described in the literature. While a variety of different models have been reported for Sr3TiNb4O15 [5-7], Sr3ZrNb4O15 has only one mention in the literature [8] and no detailed structural analysis has been performed on it. This report is on the the results of synchrotron X-ray powder diffraction investigations of the Sr3Ti1-yZryNb4O15 system from, y = 0 - 1, at both room temperature and high temperatures. 2. Sample preparation Polycrystalline powder samples were prepared using standard solid state synthesis techniques. Reagent oxides and carbonates: SrCO3 (Sigma Aldrich, 99.9 %), TiO2 (Aithaca, 99.999 %), ZrO2 (Aithaca, 99.99 %) and Nb2O5 (Aithaca, 99.999 %) were weighed out in stoichiometric ratios with x values of: x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. Samples were ground either by hand using an agate mortar and pestle or by an agate ball mill. These samples were then pressed into dense pellets or rods using a pellet press at 8 tonnes for pellets or hydrostatic press at between 50-60 MPa for rods. The samples were calcined at 950 ºC for 36 h and then sintered with intermittent grinding at 1300 ºC for periods between 24 h to 96 h. Synchrotron X-ray powder diffraction data were collected on the powder diffraction beamline, 10-BM, at the Australian synchrotron using the MYTHEN microstrip detector and a Si(111) monochromator that accepts the beam directly from a bending magnet source. 28 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 3. Results 3.1 Room Temperature For Sr3TiNb4O15 three models are reported in the literature with slight variations between them. The first proposed model for Sr3TiNb4O15 was that it formed with a tetragonal tungsten bronze structure, with space group P4bm [5]. The second model in the literature was for a C-centred othrhombic structure with space group Cmm2 [6]. The final model proposed before this work was for a primitive orthorhombic structure with space group Pba2 [7]. All these models were refined against our synchrotron X-ray diffraction data and the Pba2 model gave by far the best fit to the data. However, the data provided evidence that there was an unreported doubling of the unit cell in the c-direction. Additionally, we found that a better fit to the data could be achieved with space group Pna21 [9]. The refinement profile for the Sr3TiNb4O15 model against the data can be seen in Fig. 1. Fig. 1. Refinement profile for Sr3TiNb4O15. Red crosses are observed data, blue lines are the calculated pattern and the black line is the difference between them. The grey region is excluded from the refinement. As for the titanium analogue, Sr3ZrNb4O15 was reported to form with a tetragonal structure [8]. Refinements against synchrotron X-ray diffraction data indicate that it is isostructural to Sr3TiNb4O15. All diffraction patterns reveal peak splitting which is evidence of the orthorhombic symmetry. Reflections of the type hk1 are present in all patterns indicating a doubling of the unit cell along the c-direction (see Fig 2). Fig. 2. Section of synchrotron X-ray powder diffraction pattern for Sr3ZrNb4O15. Shown is the 211 reflection, the presence of which indicates a unit cell doubling along c. 29 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The unit cell dimensions and volumes for each composition are seen to increase linearly across the composition range. This is consistent with a solid solution forming and is in agreement with Vegard’s law (see Fig. 3). Fig. 3. Left, synchrotron X-ray diffraction patterns across Sr3Ti1-yZryNb4O15 (from bottom to top: y = 0, 0.2, 0.4, 0.6, 0.8, 1). Top right, plot of cell volume as a function of composition. Bottom right, plot of cell parameters as a function of composition. 3.2 High Temperature High temperature synchrotron X-ray diffraction data were collected for all members across the Sr3Ti1-yZryNb4O15 composition range at 300 - 950 K. It was found that every composition underwent an orthrhombic, Pna21, to tetragonal, P4bm, phase transition on heating (Fig. 4). The transition to tetragonal conicided with disappearence of superlattice reflections, which indicated the doubled unit cell. The phase transition temperatures were found to be proportional to the zirconium content in the sample. Higher zirconium content samples underwent the transition at a higher temperature. Fig. 4. Refined structure of Sr3ZrNb4O15. Left, room temperature Pna21 structure. Right, high temperature P4bm structure. Top, looking down c axis, bottom, looking down the a axis. 30 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The orthorhombic strain (b-a/b+a), as a function of temperature was determined for each composition in the series. Analysis of the strain showed that the structure continously evolved towards the higher symmetry tetragonal structure upon heating, but at the final stages the transition occurred abruptly (Fig. 5). For Sr3ZrNb4O15 without the abrupt phase transition the strain would indicate a transition temperature of 990 K instead of the 800 K observed. This type of behaviour has been observed before in other compounds, e.g. spinel type CuCrO4 [11] and perovskite type LaMnO3 [12] both show a gradual change in lattice parameters and then an abrupt shift at the transition point. Fig. 5. Left, a and b cell parameters for Sr3ZrNb4O15 as a function of temperature. Right, orthorhombic strain, (b-a)/(b+a) as a function of temperature. Acknowledgments This research was undertaken on the powder diffraction beamline at the Australian Synchrotron, Victoria, Australia and the authors thank Dr Q. Gu, Dr J. Kimpton and Dr H. Brand for their assistance. The authors also want to thank Prof. B. J. Kennedy for helpful discussions. References [1] Chang H Y, Sivakumar T, Ok K M, Halasyamani P S 2008 Inorg. Chem 47 8511 [2] Stephenson N 1965 Acta Crystallogr. 18 496 [3] Fang L, Zhang H, Yang J F, Hong X K, Meng F C 2004 J. Mater. Sci. Mater. Electron. 15 355 [4] Massarotti V, Capsoni D, Bini M, Azzoni C B, Mozzati M C, Galinetto P, Chiodelli G 2006 J. Phys. Chem. B 110 17798 [5] Ainger F W, Brickley W P, Smith G V 1970 Proc. Br. Ceram. Soc. 18 221 [6] Neurgaonkar R R, Nelson J G, Oliver J R 1992 Mater. Res. Bull. 27 677 [7] Chi E O, Gandini A, Ok K M, Zhang L, Halasyamani P S Chem. Mater. 16 3616 [8] Kryshtop V G, Devlikanova R U, Fesenko E G 1979 Inorg. Mater. 15 1777 [9] Whittle T A, Brant W R, Schmid S, in: Schmid S, Withers L R, Lifshitz R, (Eds.), 2013 Aperiodic Crystals, Springer Netherlands, pp. 179-185. [11] Kennedy B J, Zhou Q 2008 J. Solid State Chem. 181 2227 [12] Rodríguez-Carvajal J, Hennion M, Moussa F, Moudden A H, Pinsard L, Revcolevschi A 1998 Phys. Rev. B 57 R3189. 31 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Synchrotron and Neutron Powder Diffraction and XANES Studies of Cu5-xMnxSbO6 D. J. Wilsona and T. Söhnela a School of Chemical Sciences, University of Auckland, Auckland, New Zealand. Cu5SbO6 is a mixed copper compound that crystallises in a modified Delafossite structure type (CuFeO2), with two distinct modifications. Compounds, like CuFeO2, that crystallise in the Delafossite group are one of the few groups that showcase the rare property of multiferroic behaviour. The high temperature modification is of particular interest due to ferromagnetic- antiferromagnetic short range ordering of Cu2+ pairs in the structure. In order to influence the properties of Cu5SbO6, manganese were doped into the structure. This lead to an overall increase to the unit cell volume and distorted the copper to oxygen and antimony to oxygen bond lengths. Two oxidations states of manganese were found to be present within Cu5-xMnxSbO6, with a different ratio of oxidation states in the modifications. 1. Introduction Low-dimensional transition metal compounds, especially copper based oxides with mixed Cu valence states, such as Cu5SbO6, seem to be very promising for strongly correlated electron systems. Cu5SbO6 forms two modifications. The high temperature modification shows a ferromagnetic-antiferromagnetic short range ordering of Cu2+ pairs. Doping of Cu5SbO6 with a magnetically active transition metals such as Mn, replacing either the magnetic Cu2+ or the non-magnetic Sb5+ ions, would significantly influence the electric and magnetic properties in this system. Cu5SbO = [(Cu+(Cu2+ 5+6 2/3Sb 1/3)O2)]3 crystallises in a modified Delafossite structure type (CuFeO2) [1-3]. Compounds like CuFeO2 crystallising in the Delafossite structure are one of the few groups of compounds showing the rare property of multiferroic behaviour [4]. In Cu5SbO6 the magnetically active brucite-like CuO2 layer is diluted in an ordered fashion with non-magnetic Sb5+. Exploring and tuning the properties of compounds that crystallise in the Delafossite structure type could lead to interesting new developments. In particular, doping magnetically active transition metals could lead to changes of the short range ordering. The main perspective of this study is to investigate the effects of doping manganese in to brucite-like layer of Cu5SbO6. By doping metals into the oxide layer, the properties of the material should change, such as magnetism or conductivity. Manganese should have interesting influences on Cu5SbO6, with the potential to affect the short-range magnetic ordering already present. Here, we describe the structural changes that occur due to the doping of manganese into Cu5SbO6 by using synchrotron and neutron powder diffraction. XANES measurements have been used to determine the oxidation state of Mn in the solid solution Cu5Sb1-xMnxO6. 2. Experimental details Powder samples of Cu5-xMnxSbO6 were prepared by mixing stoichiometry amount of starting oxides CuO, MnO2 and Sb2O3; the mixtures were then place inside a furnace at 1100 °C and 900°C for the high and low temperature modification, respectively. After a nominal time, the samples were quenched in air proceed by grinding with a mortar and pestle. 32 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Laboratory X-ray powder diffraction patterns were obtained on a Siemen D5000 X-ray Diffractometer, equipped with a copper anode X-ray tube (λ = 1.5418 Å). The diffraction patterns were collected at room temperature between 2θ range of 10°-80° with a step size of 0.02°. Synchrotron X-ray powder diffraction (SXRD) measurements were conducted on the powder diffraction beamline, 10-BM, at the Australian Synchrotron with approximate photon energy of 16 keV, using the MYTHEN dectector and the double crystal monochromator of Si(111) flat crystal pair. Complementary to the SXRD experiments, neutron powder diffraction (NPD) measurements were performed on the high-resolution powder diffractometer ‘ECHIDNA’ at the Australian Nuclear Science and Technology Organisation (ANSTO). The desired wavelength of 1.6220 λ was selected by Ge 355 monochromator. The powder diffraction patterns were obtained at room temperature under atmospheric pressure. For data analysis of the synchrotron and neutron powder data the software packages GSAS and FullProf were used [5-7]. The oxidation state of manganese was investigated by X-ray absorption near edge structure (XANES) spectroscopy on the X-ray absorption spectroscopy beamline, Australian Synchrotron. These measurements were carried out at the Mn K-edge (Mode 2, 6539 eV) at room temperature, with a 100 element Ge Fluoro detector. In addition to measurements performed on samples, a range of binary and ternary manganese oxides with known oxidation states were utilised as standards. Data analysis was done with software package IFEFFIT (data reduction (Athena) and data analysis (Artemis)) with Average2.0 used to calibrate against a metal foil standard (Mn) [8]. 3. Results 3.1 Laboratory X-ray powder diffraction of Cu5-xMnxSbO6 Initially samples were prepared to the composition of Cu5MnxSb1-xO6 in an attempt to replace Sb5+ with Mn4+ or Mn5+. However, during quenching a green flame was observed. This was attributed to excess copper, which laboratory diffraction patterns of Cu5MnxSb1-xO6 confirmed the presence of CuO. The excess of CuO suggested the nominal composition of Cu5MnxSb1-xO6 required adjustment. Preparation of further samples was done with the adjusted composition Cu5-xMnxSbO6 to compensate for the excess CuO. The adjusted composition diffraction patterns did not contain the characteristic reflections expected from the presence of a CuO phase. 3.2 Synchrotron and neutron powder diffraction of Cu5-xMnxSbO6 SXRD was performed on both high temperature and low temperature modifications of Cu5-xMnxSbO6 in order to determine the structural changes with increasing fractional content of manganese. Comparing the diffraction patterns for the low temperature modification showed small shifts of reflections with manganese doping. However, in the high temperature modification diffraction patterns, there is a noticeable shift of the reflections as shown in Fig. 1. These shifts in reflections are indicative of a change in the lattice parameters with doping of manganese. According to the oxidation state of manganese obtained from XANES measurements, we expect the high temperature modification to incorporate more Mn2+, with consideration of the ionic sizes of Cu2+, Mn2+ and Mn3+ (0.65 Å, 0.83 Å and 0.645 Å, respectively) [9]. The Cu2+ and Mn3+ ions are similar in size, while Mn2+ is significantly larger. Thus the incorporation of Mn2+ into the Cu2+ sites results in an overall increase of the unit cell volume of 0.6% for Cu4.7Mn0.3SbO6. The inclusion of manganese into the structure also lead to a linear expansion of a, a non-linear contraction of b, a non-linear expansion of c and increasing plane angle β. In addition to changes in the lattice parameters, there is a noticeable increase to reflections attributed to the low-temperature modification in the high- temperature modification samples with increasing manganese content (Fig. 1; reflections of the lt-modification are marked with italic indicies). The increase in these reflections is not 33 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 present in samples with longer preparation time. It is suggested that the presence of these reflections is due to the increase disorder by statistical nature of doping manganese into the structure and prompts that the two modifications differ by disordered and ordered nature, with reaction temperature affecting the oxidation state of manganese. Fig.1. Left: Synchrotron X-ray powder patterns of Cu5-xMnxSbO6 normal indicies: high temperature modfaction, italic indicies low temperature modification. Right: Neutron powder diffraction patterns. In addition to SXRD, NPD has been utilised to refine the atomic positions, in order to confirm where manganese is placed within the structure and the effect on the bonding environment. Rietveld refinements were attempted with different positions of manganese, manganese replacing Cu2+ or manganese replacing Sb5+ in order to confirm the results on manganese obtained during SXRD Rietveld refinement. Due to the difference in neutron scattering lengths of manganese and copper, Rietveld refinements of the NPD patterns were able to confirm that the doped manganese is in the copper positions. Thus it is expected that the replacement of the Cu2+ with the larger Mn2+, the bond lengths of Cu-O and Sb-O will be distorted. Distortion of the bond lengths were observed in the NPD patterns, increasing the manganese content lead to the increase of 3% in the bond lengths of Sb-O in the antimony octahedral at a manganese content of 0.5. While, the copper octahedral shows an overall decrease in Cu-O length of 2% at the same manganese content. Mn0.1 Mn0.2 Mn0.3 Mn0.4 Mn0.5 Sb-O average bond distance 1.965(7) 1.978(8) 1.983(9) 2.004(5) 2.028(9) Cu-O average bond distance 2.135(1) 2.127(1) 2.123(1) 2.119(5) 2.113(1) Table.1. The average metal to oxygen bond lengths in the antimony and copper octahedral for Cu5-xMnxSbO6 (x = 0.1 to 0.5), showing the increase of the Sb-O and the decrease Cu-O bond lengths. 3.3 Oxidation state analysis of Cu5-xMnxSbO6 by XANES To determine the oxidation state of manganese in Cu5-xMnxSbO6, a series of XANES measurements were performed at the Mn K-edge. Comparing the energy position of the absorption edge for the variety of manganese oxidation state standards (oxidation state ranging between Mn0 to Mn7+), a linear relationship between energy position of the absorption edge and oxidation state of manganese was produced (Fig. 2). Comparing the energy position of the absorption edge for both modifications of Cu5-xMnxSbO6 against the manganese standards enabled us to determine the average oxidation state of manganese in these compounds. The high temperature modification was determined to have an average manganese oxidation state of 2.3, while the low temperature modification was found to be 2.7. This result suggested that manganese contained in both modifications is a mixture of 34 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Mn2+ and Mn3+, while the ratio of these two oxidation sates is different between the two modifications. Also there was no observance of a shift in energy position of the absorption edge with varying manganese content and thus no change in manganese oxidation state with varying manganese content. For Cu5-xMnxSbO6 to remain charge neutral without the inclusion of oxygen, the Mn2+ has to sit in the Cu2+ site, replacing the copper ion, while the Mn3+ must be replacing a unit of Cu2+ 5+2/3 Sb 1/3 to remain charge neutral. Fig.2. XANES spectra of various manganese containing tertiary and binary oxides (left). The relationship of oxidation state of manganese with the position of the absorption edge (right). 4 Conclusions Powder samples of both high and low temperature of Cu5-xMnxSbO6 were prepared by tradition solid state reactions. The manganese in Cu5-xMnxSbO6 was found to be a mixture of Mn2+ and Mn3+, with a higher 2+ to 3+ ratio for the high temperature modification than the low temperature modification. SXRD and NPD confirmed the replacement of copper in the structure by manganese, with distortions in the Cu-O and Sb-O bond lenths by 2% and 3% respectively in Cu4.5Mn0.5SbO6. While an increase in low temperature modification with increasing manganese content in the high temperature modification was observed in SXRD. Acknowledgments The Authors would like to thank Dr. Bernt Johannessen and Dr. Justin Kimpton for the help they provide at the X-ray absorption beamline and the powder diffraction beamline, respectively, at the Australian Synchrotron and Dr. Maxim Avdeev for this help while preforming experiments on Echinda beamline at ANSTO. We would like to thank and acknowledge the financial support provided by the Australian Institute of Nuclear Science and Engineering Inc. (AINSE), the Australian Synchrotron and the University of Auckland. References [1] Rey E 2010 BScHons Thesis The University of Auckland [2] Rey E, Si P Z and Söhnel T 2011 Proceedings of the 35th Annual Condensed Matter and Materials Meeting, Australia Australian Institute of Physics Publications, Canberra, Australian Institute of Physics 22. http://www.aip.org.au/wagga2011 [3] Climent-Pascual E, Norby P, Anderson N H, Stephens P W, Zandbergen H W, Larsen J and Cava R J 2012 Inorg. Chem. 51 557 [4] Kimura T, Lashley J C, Ramirez A P 2006 Phys. Rev.B. 73 220401 [5] Toby B H 2001 J. Appl. Crystallog. 34 210 [6] Larson T C and Von Dreele R B 2000 Los Alamos National Laboratory Report 86 748 [7] Rodriguez-Carvajal J 1993 Physica B 192 55 [8] Ravel B and Newville M 2005 J. Synch. Rad. 12 537 [9] Shannon R D 1976 Acta Crystallog. A32 751 35 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 ABSTRACTS Oral Presentations Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Adventures in Reciprocal Space – From Laue to Bragg and Back Again A.J. Edwardsa a Bragg Institute, Australian Nuclear Science and Technology Organization, Lucas Heights, N.S.W., Australia. The earliest X-ray diffraction experiments [1] employed radiation “as generated” without monochromation to produce the reciprocal space images we know as Laue patterns. The pioneering work of W.L. Bragg [2] using monochromated X-rays followed rapidly and provided the major simplification in the mathematics required to analyse X-ray diffraction patterns to derive data from which atomic resolution structural information can be deduced. In the following century, physicists, chemists and later biologists developed the Bragg methodology into a powerful tool which underpins the structure based paradigm at the core of modern chemistry and biology. Application of the Laue method to questions of structure determination at atomic resolution languished for many decades until the availability of fast computers and the technical challenges of Synchrotron sources led to a resurgence in this experimental approach [3]. With the cost of neutron beams being substantially more than that of X-ray beams, the applicability of this method to neutron diffraction studies was soon investigated [4] and today Laue neutron diffraction is the method of choice for the determination of structures where neutron diffraction is scientifically required to prove aspects of structure for which X-ray diffraction can only be “suggestive”. Chemists typically employ an array of physical methods to support their structural assertions, but a crystal structure is often presented as absolute proof and as justification of inferior characterization by other methods. This being the case it is of great concern that crystallographic studies be critically reviewed by both analyst and in the publication process. Checkcif is a fine tool but insufficient to ensure the integrity of the scientific literature – that is properly the role of the analyst and the reviewers. [1] W. Friedrich, P. Knipping, M. Laue, Sitzungsberichte der (Kgl.) Bayerische Akademie der Wissenschaften 973 (1912). [2] W.L. Bragg, Proc. Camb. Philos. Soc. 17, 45 (1913). [3] J.R. Helliwell, J. Habash, D.W.J. Cruickshank, M.M. Harding, T.J. Greenhough, J.W. Campbell, I.J. Clifton, M. Elder, P.A. Machin, M.Z. Papiz and S. Zurek, J. Appl. Cryst. 22, 483 (1989). [4] C. Wilkinson and M.S. Lehmann, Nucl. Instrum. Methods A. 310, 411 (1991). 36 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Enhanced Ferroelectric Response in Strained Perovskites B. Wylie-van Eerda, T. Yamadab, J. Wangc,d, N. Setterd and J. Trodahla a MacDiarmid Institute of Nanotechnology and Advanced Materials, School of Chemical and Physical Sciences, Vitoria University of Wellington, PO Box 600, Wellington, New Zealand. b Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japan. c Graduate School at Shenzhen, Tsinghua University, 518055, Shenzhen, China. d Ceramics Laboratory, Swiss Federal Institute of Technology (EPFL), 1015 Lausanne, Switzerland. Ferroelectrics are ubiquitous in technology, based on their strong piezoelectric and pyroelectric responses, their nonlinear dielectric response and their multi-stable polarization states. The vast majority of applications make use of polycrystalline PbZrxTi1-xO3 (PZT) ceramics, but there is an ongoing interest in a search for alternative ferroelectrics, both for avoiding Pb in their manufacture and to find stronger responses. Among the aveneus showing promise is a srearch for materials and structures in which the ferroelectric state and its responses are enhanced by built-in strain. Raman spectroscopy provides an especially convenient signature of structural phase transitions that has made it the measurement of choice for the delineation of phase transition lines in a stress-temperature diagram. This presentation will focus on Raman investigations of strong increases of the ferroelectric-phase transition temperatures in two strained systems: (1) core-shell PZT nanowires supporting tensile hydrostatic strain (i.e. negative pressure) and (2) strained SrTiO3 (STO) films grown on sbstrates that impose biaxial compressive strain. The former showed a transition temperature enhanced from 500 to over 600 °C, while the latter led to a ferroelectric phase in normally nonferroelectric STO. 37 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Weak antilocalisation in topological insulators X. Bia, E.M. Hankiewiczb and D. Culcerc a ICQD, The University of Science and Technology of China, Hefei 230026, China. b Universitaet Wuerzburg, Wuerzburg, Germany. c School of Physics, The University of New South Wales, Sydney 2052, Australia. Topological insulators (TI) have revolutionised our understanding of insulating behaviour. They are insulators in the bulk but conducting along their surfaces, thanks to surface states in which the spin and the charge are strongly coupled by means of the spin-orbit interaction. Much of the recent research on TI focuses on overcoming the transport bottleneck [1], namely the fact that surface state transport is overwhelmed by bulk transport stemming from unintentional doping. The key to overcoming this bottleneck is identifying unambiguous signatures of surface state transport. This talk will discuss one such signature, which is manifest in the coherent backscattering of electrons in TI. Because of the strong spin-orbit coupling in TI one expects to observe weak antilocalisation rather than weak localisation, meaning that coherent backscattering increases the electrical conductivity [2]. The features of this effect, however, are rather subtle, because in TI the impurities have strong spin-orbit coupling as well, greatly increasing the complexity of the problem [3]. I will show that spin- orbit coupled impurities introduce an additional time scale, which is expected to be shorter than the dephasing time, and the resulting conductivity has a logarithmic dependence on the carrier number density, a behaviour hitherto unknown in 2D electron systems. The result we predict is directly observable experimentally and would provide a smoking gun test of surface transport. Furthermore, I will also discuss the effect of electron-electron interactions on transport in this regime. [1] D. Culcer, Physica E 44, 860 (2012). [2] G. Tkachov and E.M. Hankiewicz, Phys. Rev. B 84, 035444 (2011). [3] X. Bi, E.M. Hankiewicz and D. Culcer, to be published. 38 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The dynamics and critical properties of FePS3, an Ising-like two- dimensional magnet on a honeycomb lattice A. Wildesa, K. Ruleb, D. Lançona,c and T. Hicksd a Institut Laue-Langevin, Grenoble, France. b Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia. c Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland. d School of Physics, Monash University, Victoria 3800, Australia. The MPS3 compounds (M = transition metal) are a family of materials where the M2+ ions lie in planes forming a honeycomb lattice. The planes are weakly bound by van der Waals forces and, when the M2+ carries a magnetic moment, the materials are good approximations of two- dimensional (2D) antiferromagnets. The FePS3 compound is of particular interest as it is a rare example of an Ising-like 2D magnet with honeycomb symmetry [1]. We have performed experiments with neutron scattering to investigate the magnon dynamics on both a powder [2] and, more recently, on a single crystal. We have further made extensive measurements of the critical dynamics of the compound. We will present our results, showing the magnon dispersion surface and the magnitudes of the exchange interactions along with the scaling behaviour of the magnetization and the anisotropy. The results will be contrasted with a sister compound, MnPS3, which is a good example of a Heisenberg-like 2D magnet. We will also discuss the possibilities for tricritical points and quantum phase transitions in this compound. [1] K.C. Rule, G. McIntyre, S.J. Kennedy and T.J. Hicks, Phys. Rev. B 76, 134402 (2007). [2] A.R. Wildes, K.C. Rule, R.I. Bewley, M. Enderle and T.J. Hicks, J. Phys.: Condens. Matter 24, 416004 (2012). 39 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Colour Tunable Light Emission from Organic Field-Effect Transistors H. von Seggerna a Electronic Materials Division, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany. The unique property of ambipolar organic light emitting field-effect transistors (OLETs) is the ability to position the light emission zone within the transistor channel through the applied transistor biases. In this talk the basics of the ambipolar OLET will be discussed [1,2,3] and two examples for colour tuning will be demonstrated [4,5]. Both approaches take advantage of the ability of a controlled displacement of the recombination zone through the organic semiconductors. In the first approach two different acenes with different emission colours are employed in a parallel stack in a top-contact bottom-gate FET configuration [4]. It will be demonstrated that due to thermionic emission of electrons at the source, light of one colour can be generated near the source contact even in hole accumulation. Due to the electrically controllable positioning, the charge carrier recombination zone can be directed from the top acene layer to the bottom acene layer. Thereby the emitted light can be continuously shifted by about 50 nm from green to red emission. A second approach takes advantage of the horizontal displacement of the recombination zone within the channel of the transistor [5]. On top of the semi-transparent gate electrode of a F8BT transistor a colour conversion layer is deposited in a wedge-like shape partially covering the channel. In the ambipolar regime the charge carrier recombination takes place in the F8BT layer, and dependent on the position of the recombination zone either the emitted light of the F8BT layer or the partially absorbed and converted light from the colour conversion layer can be detected. The electroluminescence maximum of the emitted light can be shifted by about 30 nm. The physics and potential applications of such colour tuneable OLETs will be discussed. [1] A. Hepp, H. Heil, W. Weise, M. Ahles, R. Schmechel and H. von Seggern, Phys. Rev. Let. 91, 157406 (2003). [2] J. Zaumseil, R.H. Friend and H. Sirringhaus, Nat. Mater. 5, 1 (2006). [3] M. Schidleja, C. Melzer and H. von Seggern, Adv. Mater. 21, 1172 (2009). [4] E.J. Feldmeier, M. Schidleja, C. Melzer and H. von Seggern, Adv. Mater. 22, 3568 (2010). [5] E.J. Feldmeier and C. Melzer, Org. Electron. 12, 1166 (2011). 40 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Organic luminescent solar concentrators for solar cells N.M. Wincha, G.J. Smitha, D.H. Bhuiyanb, R.D. Breukersb and A.J. Kayb a School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand. b Callaghan Innovation Research Limited, Lower Hutt, New Zealand. Current inorganic solar cells use silcon-based semiconductors to convert the incident sunlight into electricity. Solar cells are inherently expensive due to the high cost of the semiconductor, and because the light to energy efficiency is very low. The low efficiency arises from both the solar cell not absorbing across the whole solar spectrum, and their poor response to diffuse sunlight. An alternative to solar cells are luminescent solar concentrators (LSCs). A LSC is a device which absorbs sunlight over a large area of material, and then directs the energy, through luminescent emission, to solar cells mounted on the edges. Typically a LSC consists of a glass waveguide with organic luminescent molecules either embedded in the glass matrix, or as a thin film coating. Due to the small number of solar cells required, LSCs are more cost effective than straight silicon solar cells, and have the advantage that they work in diffuse sunlight. Conjugated polymers based on polyphenylenevinylene (PPV) have been widely studied for use in organic light emitting diodes and solar devices [1]. An alternative based on oligo- fluorenevinylenes (OFV) has also been suggested [2] but not extensively investigated. We are investigating the use of these two chromophore families as luminescent molecules for LSCs. The luminescent properties of these molecules have been characterised (for example, quantum yield and fluorescent lifetimes) in a wide range of solvents and as a guest-host system in polymethyl methacrylate (PMMA) thin films. [1] A.J. Tilley, S.M. Dancak, C. Browne, T. Young, T. Tan, K.P. Ghiggino, T.A. Smith and J. White, J. Org. Chem. 76, 3372 (2011). [2] Q. Liu, W. Liu, B. Yao, H. Tian, Z. Xie, Y. Geng and F. Wang, Macromolecules 40, 1851 (2007). 41 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Structural Studies of Phase Transitions in Hybrid Organic-Inorganic Salts with Temperature and Pressure J. Binnsa,d, S. Parsonsa,d, S. Moggacha,d, R. Valienteb, G. McIntyrec, K. Kamenevd a School of Chemistry, Joseph Black Building, West Mains Road, Edinburgh, Scotland. b Applied Physics Department, Faculty of Science, University of Cantabria, 39005 Santander, Spain. c Bragg Institute, ANSTO, Lucas Heights NSW 2234, Australia. d Centre for Science at Extreme Conditions, The University of Edinburgh, Erskine Williamson Building, The King's Buildings, Mayfield Road, Edinburgh, Scotland, United Kingdom. The alkylammonium tetrachlorometallates have attracted significant attention for the numerous phase transitions observed in a relatively narrow range of temperatures and pressures as well as ferroelectric,-elastic and -magnetic behaviours. [1,2] Such simple organic salts could find possible applications as thin-film functional materials in low cost ferroelectric capacitors and RAM. With the exception of bis(tetramethylammonium) tetrachlorozincate(II) this class of materials has been subject to relatively little structural investigation, with a number of general phase sequences being determined from calorimetric and polarisation measurements. [3,4] While there are known to be ferroelectric phase transitions in many of these materials, the exact mechanism by which these simple organic salts exhibit such behaviour is unknown. We report on the phase sequences observed in two related materials: tetramethylammonium tetrachloroferrate(III) (TCF), and the previously unknown tetramethylammonium tetrachlorogallate(III) (TCG) which display re-entrant as well as plastic crystalline phases. [1] D. Wyrzykowski, R. Kruszynski, J. Klak, J. Mrozinski and Z. Warnke, Inorg. Chim. Acta 361, 262 (2008). [2] H. Shimizu, N. Abe, N. Kokubo, N. Yasuda, S. Fujimoto, T. Yamaguchi and S. Sawada, Solid State Commun. 34, 363 (1980). [3] Z. Czapla, O. Czupinski, Z. Galewski and L. Sobczyk, Solid State Commun. 56, 741 (1985). [4] I. Ruiz-Larrea, A. Lopez-Echarri and M.J. Tello, Solid State Commun. 64, 1099 (1987). 42 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Optically and Electrically Detected Electron Spin Resonance in OLEDs R. Suttona and A. Edgara a School of Chemical and Physical Sciences, Victoria University,Wellington, New Zealand. Organic light-emitting diodes (OLEDs) bring the promise of efficient large area light emitting devices which can be manufactured by simple techniques such as spin coating [1]. Whilst technical progress has been rapid, such that OLED screens are now being introduced into television displays (and have been available for some time in cell phones), the basic mechanisms which underpin light emission and “killer” process of non-radiative recombination are as yet still poorly understood. One particular on-going problem with OLEDs is the question of ageing – a deterioration of emission efficiency with time and use. Since the process of electron-hole recombination is spin-dependent, one possible technique which may help unravel the details of the processes is electron spin resonance. However, there are too few spins in a thin OLED layer for the conventional microwave detection of ESR, but detection via a change in electrical conductivity and/or optical emission intensity has been shown to be effective in some cases [2]. We have customised a 9 GHz ESR spectrometer for electrical and optical detection, and present here results of an investigation of spin-dependent ageing processes in OLEDs based on ITO/PEDOT:PSS/emissive layer/metal layer with the emissive layer being PFO or PPV and the metal layer being aluminium, silver, or calcium. Spin-dependent signals are observed at room temperature and discussed in terms of spin dependent trapping, whilst significant zero-field magnetoresistance effects are also observed. [1] J.W. Park, D.C. Shin and S.H. Park, Semicond. Sci. Technol. 26, 034002 (2011). [2] J.M. Lupton, D.R. McCarney and C. Boehme, ChemPhysChem 11, 3040 (2010). 43 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Characterization of a Fluoroperovskite Based Fibre Coupled Optical Dosimeter for Radiotherapy J. Donaldsona,b, G.V.M. Williamsb and S.G. Raymondc a Blood & Cancer Centre, Wellington Regional Hospital, Wellington, New Zealand. b MacDiarmid Institute, SCPS, Victoria University, Wellington, New Zealand. c Callaghan Innovation, Lower Hutt, New Zealand. The increasing complexity of modern radiation treatment techniques demands comparable advances in clinical radiation dosimetry equipment, with emphasis on improving spatial resolution and further developing two and three-dimensional dosimetry systems [1]. Fibre coupled optical dosimeters can potentially deliver significant gains in miniaturization and sensitivity when compared to both ionisation chambers and established solid state detectors. For this reason we are developing a fibre optic dosimeter that uses inorganic fluoroperovskite crystals (NaMgF3 and RbMgF3, activated with either Eu2+ or Mn2+) as the active radiation detection material for applications in medical radiation dosimetry [2]. In this report we discuss the requirements for radiation dosimeters specific to radiotherapy and the results of a selection of radioluminescence characterization measurements made with a prototype fibre optic dosimeter at Wellington Hospital. The results include a dose history dependence as low as 0.01% per Gy, a radioluminescence temperature dependence measured in both the prototype system and bulk crystal samples of less than 0.1% per °C, and independence from dose per pulse for NaMgF3. The response was also compared to measurements made using a small field ionisation chamber. Of the materials studied, only those based on NaMgF3 were found suitable for radiotherapy dosimetry. The primary difficulties arising from use in medical radiations are the stem signal due to Čerenkov photons and the residual dose history dependence. Potential solutions to these difficulties will be discussed, along with the possibilities offered by a wider range of luminescence activators. [1] M.M. Aspradakis et al. Report Number 103, Institute of Physics and Engineering in Medicine, York (2010). [2] G.V.M. Williams and S. Raymond, Radiation Measurem. 46, 1099 (2011). 44 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Towards better understanding of atomically precise gold clusters and titania made using surface modifying agents V.B. Golovkoa,b, J.Y. Ruzickaa, F. Abu Bakara,c, D.P. Andersona, R. Adnana, B. Donoevaa,b, D. Ovoshchnikova, G.F. Methad, G.G. Anderssone, L. Thomsenf, B. Cowief, C. McNicolla,b,g, B. Inghamb,g, T. Kemmittb,g, V. Fangh and J. Kennedyb,h a Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand. b The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. c University Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. d Department of Chemistry, University of Adelaide, SA 5005, Australia. e Flinders Centre for NanoScale Science and Technology, Flinders University, Adelaide, SA 5001, Australia. f Australian Synchrotron, 800 Blackburn Road, Clayton Vic-3168, Australia. g Callaghan Innovation, P.O. Box 31-310, Lower Hutt 5040, New Zealand. h National Isotope Centre, GNS Science, P.O. Box 31312, Lower Hutt 5010, New Zealand. Controlled synthesis of titania nanoparticles using recently perfected sol-gel methodology [1,2], synthesis of atomically precise metal clusters, their deposition and activation on oxide supports and studies of properties of the resulting materials as promising catalysts and sensors will be briefly discussed [3-9]. Our work on synthesis of titania nanoparticles is focused on careful tuning of the reaction conditions and use of selected surface modifying agents capable of directing and controlling growth of nanoparticles with specific size, phase and even population of Ti+3 sites at the surface [2]. Promising performance of titania made using our methodology as near-IR reflective coating will be briefly highlighted. From pre-historic times gold was known as a chemically inert, “noble” metal until, in 1987, Haruta et al. proved that gold nanoparticles can be catalytically active. Results of research focused on the use of size-controlled, chemically pre-synthesised nanoparticles (colloids and clusters) with core sizes ranging from classical 1.5 nm “Au55” systems to atomically precise, uniquely small clusters (Au9 etc.) including a range of mixed-metal clusters will be presented. Immobilization of such clusters on a variety of supports had been pursued in an attempt to fabricate a family of site-isolated 45 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 catalysts, where properties of the active site are defined by the nature of the precursor with great precision. Catalytic performance in selected reactions will be highlighted. New insights in the nature of our precisely defined precursors (pure and immobilised onto supports) obtained using relevant materials characterization techniques, such as Synchrotron X-ray Photoelectron Spectroscopy will be presented. [1] T. Kemmitt et al., Curr. Appl. Phys. 13, 142 (2013). [2] J.Y. Ruzicka et al., RSC Advances (submitted). [3] M. Turner, et al., Nature 454, 981 (2008). [4] D. Anderson et al., Phys. Chem. Chem. Phys. 15, 3917 (2013). [5] D. Anderson et al., Phys. Chem. Chem. Phys. 15, 14806 (2013). [6] M.Z. Ahmad et al., Int. J. Hydrogen Energy 38, 12865 (2013). [7] M.Z. Ahmad et al., Sensors and Actuators B 179, 125 (2013). [8] B.G. Donoeva et al., ACS Catal. 3, 2986 (2013). [9] D. Ovoshchnikov et al., Catal. Sci. Technol. DOI: 10.1039/C3CY01011B (2013). 46 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Low Cost Refractive Index Sensing Using Zirconia Inverse Opal Thin Films A. Chana, D. Sun-Waterhousea and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. A series of zirconia (ZrO2) inverse opal thin films and powders with pseudo photonic band gaps along the [111] direction at 465, 525 and 628 nm were successfully fabricated by the colloidal crystal template technique. SEM, TEM and XRD analyses revealed that the ZrO2 inverse opals comprised a fcc array of spherical macropores (diameters 260, 287 and 342 nm, respectively) within a matrix of nanocrystalline tetragonal ZrO2. The specific surface areas of all samples were 45-47 m2 g-1, and independent of the macropore size. The optical properties of the ZrO2 inverse opal thin films were comprehensively characterised and were found to be in excellent accord with a modified Bragg’s law expression that considers both refraction and diffraction of light in the inverse opal architectures [1]. The photonic band gap (PBG) position for the ZrO2 inverse opals thin films red shifted on immersion in organic solvents, with the magnitude of the shift being directly proportional to the refractive index of the solvent. Solvent refractive index sensing with a precision of ~0.0005 is demonstrated. Air Methanol 80 70 !!!!!!!!!!!!!!!!!!!!!!!!!! ! 60 ! ! ! 50 ! ! 40 460.20 nm - Air (1.0000) ! 581.80 nm - Methanol (1.3284) ! 591.60 nm - Acetone (1.3587) 592.80 nm - Ethanol (1.3614) ! 602.20 nm - n-heptane (1.3876) 30 617.00 nm - DCM (1.4241) ! 630.20 nm - CCl4 (1.4601) !max = 460 nm 642.40 nm - Toluene (1.4969) ! 644.00 nm - Benzene (1.5011) 663.80 nm - Bromobenzene (1.5580) 20 400 500 600 700 800 Wavelength (nm) Figure 1. (above left) ZrO2 inverse opal thin films in air and in methanol. (below left) SEM image of ZrO2 inverse opal thin film. (right) UV-Vis transmittance data of a ZrO2 inverse opal thin film in solvents of increasing refractive index. [1] R. Schroden, M. Al-Daous, C.F. Blanford and A. Stein. Chem. Mater. 14, 3305 (2002). 47 % Transmittance Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Enhanced photocatalytic activity in F-TiO2: effect of solvent and fluorine modifier towards the morphology of TiO2 F. Abu Bakara,b,c, J.-Y. Ruzickaa,c, B.E. Williamsona, C. McNicolla,c,d, B. Inghamc,d, T. Kemmittc,d and V.B. Golovkoa,c a Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand. b University Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. c The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. d Callaghan Innovation, PO Box 31-310, Lower Hutt 5040, New Zealand. Unlike homogeneous radical chemistry, heterogeneous photocatalytic reactions strongly depend on the properties of titania (TiO2), such as its surface chemistry, lattice defects, crystallinity and particle size. Surface properties are particularly critical: surface modification of TiO2 changes not only the reaction rate [1,2] but also the mechanism of the product formation [3,4]. In this study, a range of fluorine-modified TiO2 were synthesised by thermal degradation of peroxotitaic acid in the presence of three non-toxic (cf. HF) surface modifiers: NBu4F, NBu4BF4 and NBu4PF6. Two solvents, ethanol and isopropanol, were used in the synthesis to elucidate the effect of the solvents on the morphology and photocatalytic activity of the resulting materials. The hydrolysis rate of titanium isopropoxide (TTIP) and thus the aggregation rate of primary particles may be affected when different types of solvents are used in the synthesis of TiO2. As a result, primary and secondary particle sizes, morphology and phase composition may be altered. The morphology, crystal phase and specific surface area etc. of the catalyst were determined using FESEM, TEM, PXRD, ATR-FTIR, TGA and BET analysis methods. The photocatalytic activity of synthesised TiO2 was evaluated in the photodegradation of popular, industrially used Reactive Blue 19 (RB19) under both broad spectrum and visible light only irradiation. Obtained results indicate that different anions in the surface-modifying agent and the type of solvent used significantly affect the morphology, particle size and crystal phase of the catalysts. The catalyst synthesised in the presence of EtOH as a solvent using NBu4PF6 as a surface modifier exhibits the highest degradation percentage under both broad spectrum and visible light irradiation compared with other surface-modified TiO2 and commercial TiO2 (Degussa P-25). 38th Annual Condensed Matter and Materials Meeting, Waiheke Island, Auckland, NZ 48 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 [1] A. Fujishima and K. Honda, Nature 238, 37 (1972). [2] H. Zhan, K. Chen and H. Tian, Dyes Pigm. 37, 241 (1998). [3] C. Sriwong, S. Wongnawa and O. Patarapaiboolchai, Chem. Eng. J. 191, 210 (2012). [4] H. Zhang, G. Chen and D.W. Bahnemann, J. Mat. Chem. 19, 5089 (2009). 38th Annual Condensed Matter and Materials Meeting, Waiheke Island, Auckland, NZ 49 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Induced few-electron GaAs Quantum Dots L.A. Yeoha, A.M. Seea, O. Klochana, I. Farrerb, D.A. Ritchieb and A.R. Hamiltona a School of Physics, University of New South Wales, Sydney 2052, Australia. b Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom. Electrostatically defined, tunable quantum dots (QD) have been routinely fabricated from a two-dimensional electron gas (2DEG) in semiconductors such as GaAs [1] and have the potential to form the building blocks of a solid state quantum computer [2]. Such devices have been typically fabricated from modulation doped wafers. However the presence of dopants cause charge noise and temporal instability, as the dopants switch between ionized and de- ionized states [3,4]. To eliminate the need for dopants, the 2DEG can be electrostatically “induced” via a global metal top gate [5]. To operate the QD as a spin qubit, we need to create a small, few-electron QD to study the individual spin states. Such fine nanostructures require metal gate patterns in the sub-micron scale, plus a sharp, well defined, electrostatic potential [5]. Hence the 2DEG needs to be brought as close to the wafer surface as possible. Improvements in fabrication have allowed such induced devices to yield similar mobilities and densities at equivalent 2DEG depths from the wafer surface, as their modulation doped counterparts [6]. Recently, such techniques have allowed for the creation of stable, QDs containing hundreds of electrons [6,7]. Here we will present our work towards the fabrication and characterization of a few-electron QD, created from an induced GaAs/AlGaAs heterostructure. Our first devices exhibit excited states in the coulomb diamonds and contains tens of electrons. [1] R. Hanson and D.D. Awschalom, Nature 453, 1043 (2008). [2] D. Loss and D.P. DiVincenzo, Phys. Rev. A. 57, 120 (1998). [3] M. Pioro-Ladrière et al., Phys. Rev. B 72, 115331 (2005). [4] C. Buizert et al., Phys. Rev. Lett. 101, 226603 (2008). [5] B.E. Kane et al., Appl. Phys. Lett. 67, 1262 (1995). [6] W.Y. Mak et al., Appl. Phys. Lett. 102, 103507 (2013). [7] A.M. See et al., Appl. Phys. Lett. 96, 112104 (2010). 50 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 SDW and AFM order in single crystal EuFe2As2 system under high-pressue using a new ceramic anvil high-pressure cell N. Suresha, S.V. Chonga, J. Tallona and K. Kadowakib a MacDiarmid Institute of Advanced Materials and Nanotechnology Victoria University of Wellington, New Zealand. Callaghan Innovation Lower Hutt 5040 New Zealand. b Institute of Materials Science and Graduate School of Pure & Applied Sciences, University of Tsukuba - 1-1-1, Tennodai, Tsukuba, Ibaraki 305-8573, Japan. Single crystals of EuFe2As2 (Eu122) doped with 0.6-phosphorus (EuFe2As1.4P0.6) were grown using the FeAs flux technique. A newly designed high-pressure cell adapting ceramic anvils was used to probe the competition among spin-density wave (SDW), collapsed phase and superconductivity in Eu122. The magnetic moment at low temperatures was measured using a SQUID magnetometer with lead (Pb) as the pressure marker. The maximum pressure that can be attained with this new design is 5 GPa. This new cell was used in conjunction with dc magnetization measurements and we show that EuFe2As1.4P0.6 undergoes a pressure-induced tetragonal-to-orthorhombic structural transition coinciding with antiferromagnetic ordering. We found the applied pressure and temperature at each of these transitions were similar to those reported in literature measured by resistivity and in other SQUID pressure cell designs giving us the confidence to employ this set-up to study other systems. Research collaborations using this high-pressure facility are invited. 51 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Tribute to CSIRO Scientists T.R. Finlaysona a School of Physics, University of Melbourne, Victoria 3010, Australia. The aim of this invited presentation is to pay tribute to the four CSIRO colleagues, Drs. John Dunlop, Tony Farmer, Gerry Haddad and Don Price, who lost their lives in the horrific crash of a Robinson R44 helicopter, near Panorama House, Bulli Tops, Wollongong, on 21st March, 2013. Two of these scientists, Dunlop and Price, had been most enthusiastic supporters of and regular contruibutors to this Annual Condensed Matter and Materials Conference, since its inception in 1977. The presentation will briefly summarise the scientific careers of all four colleagues. The assistance of Drs. Stephen Collocott and Tony Murphy, CSIRO, Lindfield, in providing some of the details concerning their colleagues for the preparation of this tribute presentation, is acknowledged. 52 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Toward an Accurate Description of Rare Gas Phases P. Schwerdtfegera, A. Hermanna, E. Pahla and J. Wiebkea a Centre for Theoretical Chemistry and Physics, The New Zealand Institute for Advanced Study, Massey University Auckland, Auckland, New Zealand. Rare gas solids provide an ideal testing ground for the accurate many-body treatment of electron correlation through a many-body decomposition of the interaction potential. Here we present complete basis set (CBS) limit calculations for the fcc lattices of solid neon and argon, using second- to fourth-order Møller-Plesset theory, MP2-4, and coupled-cluster calculations, CCSD(T), to describe electron correlation within a many-body expansion of the interaction potential up to third order. A correct description of the three-body Axilrod-Teller- Muto term for the solid state is only obtained from third-order on in the many-body expansion of the correlation energy, correcting the severe underestimation of long-range three-body effects at the MP2 level of theory. The dilemma that all two-body interaction potentials prefer the hcp over the fcc structure is discussed. The performance of the methods with increasing pressure is analyzed, showing that the convergence of the Møller-Plesset series deteriorates as the electronic band gap decreases, resulting in rather large deviations for the equation of state (pressure-volume dependence). The application to the accurate determination of melting temperatures at high pressures is discussed. Figure 1. Temperature-dependence of the molar isobaric heat capacity CP of argon at 10 GPa pressure. Also shown are snapshots of configurations of the Ar256 supercell below and above the homogeneous melting at critical superheating at a temperature of T+ = 1254 K. (from J. Wiebke, E. Pahl and P. Schwerdtfeger, Angew. Chem. 52, 13202 (2013)). 53 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Total State Designation for Electronic States of Periodic Systems D. Andraea a Institute of Chemistry and Biochemistry, Physical and Theoretical Chemistry, Freie Universität Berlin, Germany. The theory of electronic structure of solids has a large variety of tools at hand, from which it can choose to use the ones being (or seeming) most appropriate for a successful solution to a given problem. But the choice eventually made (wave-function-based or density-functional- based, level of treatment of electron correlation, etc.) sometimes appears to merely reflect the type of solid to be studied (molecular crystal, insulator, semiconductor, metal, etc.). Only little attention is given to the fact that a (much more) detailed description of the electronic state(s) of the total system (polymer, slab, crystal) plays, at best, only a minor role in many popular approaches to the problem. This is strange insofar as the clear identification and characterization of the electronic state(s) constitutes a sort of ``ultimate goal´´ of any quantum mechanical study of a system. An improvement of our theory of electronic structure in periodic systems with respect to total state characterization is highly necessary, also from a practical point of view. A better understanding of the possible total electronic states of a crystalline material may help a lot in understanding its behaviour in nanotechnological applications. It will also lead to a true density of (total) states, in contrast to the widely used density of (single particle) states. 54 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Influence of Relativistic Effects on the Melting of Mercury E. Pahla, F. Calvob and P. Schwerdtfegera a Centre for Theoretical Chemistry and Physics, INMS and NZIAS, Massey University Auckland, New Zealand. b ILM, Université de Lyon and CNRS UMR 5306, France. Mercury, Hg, is the only elemental metal liquid at room temperature - the reasons for this phenomenon posed a long-standing puzzle in chemistry. Since the 80’s the importance of relativistic effects in understanding the properties of heavier elements became clear: In the case of mercury, the valence (6s) electrons are stabilized due to relativity causing a very weak bonding in the mercury dimer and small clusters and it was speculated that also the low melting point of mercury at 234.32 K could so be explained. By using parallel-tempering Monte-Carlo simulations we have now modelled the solid-liquid phase transition in mercury based on the so-called DIM (diatomics in molecules) interaction model. In this model, the complicated many-body effects in Hg are included approximately by expanding the Hamiltonian in a basis of the ground and the 12 lowest excited states of the Hg dimer [1]. A non-relativistic version of the DIM model was developed and both, the relativistic and non-relativistic models, were updated by using highly accurate, ab initio ground and excited potential curves of the Hg dimer [2,3]. The results showed that indeed relativistic effects, and more specifically scalar-relativistic relativistic ones, make Hg liquid at room temperature – without them mercury would melt more than 100°C higher than observed [4,5]! [1] H. Kitamura, Chem. Phys. 325, 207 (2006). [2] F. Calvo, E. Pahl, P. Schwerdtfeger and F. Spiegelman, J. Chem.Theory Comput. 8, 639 (2012). [3] E. Pahl, D. Figgen, C. Thierfelder, K.A. Peterson, F. Calvo and P. Schwerdtfeger, J. Chem. Phys. 132, 114301 (2010); E. Pahl, D. Figgen, A. Borschevsky, K.A. Peterson and P. Schwerdtfeger, Theor. Chem. Acc. 129, 651 (2011). [4] F. Calvo, E. Pahl, M.Wormit and P. Schwerdtfeger, Angew. Chem. Int. Ed. 52, 7583 (2013). [5] http://www.youtube.com/watch?v=NtnsHtYYKf0 55 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Transport Models in Nanofluidics G.R. Willmotta,b a Department of Physics, The University of Auckland, New Zealand. b The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. Nanofluidics, which involves fluid flows in and around submicron structures, has evolved from the established fields of microfluidics and nanotechnology. Nanofabrication provides the tools to build nanofluidic structures [1], and the field will be integral in efforts to understand complex biological interactions. Fluid flows are inherently laminar at small length scales, yet interesting and complex transport problems arise from a variety of potentially significant and concurrent effects – mechanisms, species and carriers, and geometries [2]. Here, nanofluidic transport will be discussed in the context of nanopore-based sensors. Such devices use ‘resistive pulse sensing’ to detect and analyse single nanoparticles, by examining the transient blockage of ionic current when the particle passes though the nanopore. Transport of both ions and nanoparticles are considered, while key mechanisms include electrophoresis, electro-osmosis, dielectrophoresis and pressure-driven flow. Molecular-scale nanopores are heavily studied for analysis of single molecules, particularly DNA, while sensors on the scale of ~100 nm are suitable for studying exosomes, emulsions and viruses. Overall transport dominance strongly depends upon experimental parameters [3]. Modelling approaches for molecular-scale transport are usually based on the space-charge model [2], which combines electrostatics with the Nernst-Planck and Navier-Stokes equations. For analysis of experiments using larger pores, a semi-analytical approach is probably more efficient [3]. There are applied research opportunities regarding dimensionless scaling, and validation of semi-empirical approaches. More fundamental nanofluidic challenges include understanding nanoscale wetting, disjoining pressure, and nanobubbles. [1] C. Duan, W.Wang and Q. Xie, Biomicrofluidics 7, 026501 (2013). [2] R.B. Schoch, J. Han and P. Renaud, Rev. Mod. Phys. 80, 839 (2008). [3] G.R. Willmott, M.G. Fisk and J. Eldridge, Biomicrofluidics 7, 064106 (2013). 56 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnetic properties of rare-earth nitride heterostructures for MRAM devices E.-M. Antona, B.J. Rucka, J.F. McNultya, F. Natalia, S. Granvilleb and H.J. Trodahla a The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand. b The MacDiarmid Institute for Advanced Materials and Nanotechnology, Callaghan Innovation, Lower Hutt 5010, New Zealand. In recent years there is a growing demand for affordable and energy efficient memories, especially due to the drastically increased usage of mobile devices. New non-volatile memory (NVM) technologies therefore need to be developed, which keep the data safely stored without continuous power consumption. Promising emerging NVMs are magnetoresistive random access memories (MRAM), which are based on the difference in resistance between two stacked magnetic layers, depending if their magnetisations are aligned parallel or antiparallel. These magnetic tunnel junctions rely on a spin polarised current, a requirement for which the rare-earth nitrides (REN) seem ideal. Many RENs are ferromagnetic semiconductors which only conduct in the majority spin channel, giving rise to a highly spin polarised current and thus a large difference between the two resistance states. Moreover, the RENs show highly contrasting magnetic properties. SmN has a small magnetic moment and large coercive field exceeding 6 T, which makes it an ideal material for the reference layer, whereas GdN has a small coercive field of ~ 0.01 T enabling it to switch easily. Thin film superlattices and bilayers of the two REN materials were made by physical vapour deposition and investigated by superconducting quantum interference device (SQUID) magnetometer, X-ray magnetic circular dichroism (XMCD) and polarised neutron reflectometry (PNR) to gain insights into their magnetic interlayer exchange. Whereas SQUID gives information about the integral magnetisation of the layer systems, XMCD can retrieve spin-, orbital- and element sensitive magnetic information, allowing to separate the magnetisation of the different layers. PNR is a depth resolved method, providing magnetic depth profiles across the constituent layers. The combination of these advanced experimental technologies provides insights into the magnetic interlayer exchange crucial to develop functional MRAM devices. 57 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnetically driven electric polarization in frustrated magnetic oxide multiferroics N. Narayanana,c, N. Reynoldsb, F. Lia, A.M. Muldersa, P. Rovillainb,c, C. Ulrichb,c, M. Bartkowiakd, J. Hesterc, G. McIntyrec and W.D. Hutchisona a School of PEMS, UNSW Canberra, ACT, Australia. b School of Physics, UNSW, Sydney, Australia. c Bragg Institute, ANSTO, Sydney, Australia. d HZB, Berlin, Germany. In multiferroics more than one ferroic order can coexist and in the present case we are interested in systems which exhibit simultaneous magnetic ordering and electric polarization (EP). Of particular interest are frustrated magnetic materials that exhibit an electric polarization that is strongly coupled to the magnetism [1]. Examples of such multiferroics are RMnO3 (R= Tb, Dy), Ni3V2O8, and RbFe(MoO4)2 [2 4]. This coupling can be utilized in applications such as magnetoelectric random access memory. Although technically relevant, the coupling mechanism between these two orders is complicated [1]. Whereas the magnetic ordering results from exchange interaction of unpaired spins, origins of EP coupled to the magnetic ordering depends on the interplay between lattice, orbital, spin and charge degrees of freedom. Several mechanisms such as the inverse Dzyaloshinskii Moriya interaction, magnetostriction and coupling of the chirality to the crystal structure or a combination of them are currently discussed depending on the compound [2-5]. Additionally EP has ionic and electronic contributions. In the present work we investigate the coupling of magnetism to EP involving all three above mechanisms, in orthorhombic DyMnO3 (DMO), Cu3Nb2O8 and Ba3NiNb2O9 with neutron powder diffraction (NPD), magnetization and heat capacity measurements focusing on the magnetic and multiferroic phase transitions. In order to investigate the role of the lattice distortion or equivalently the role of oxygen, isotope substitution of 16O with 18O was performed on DMO. All samples are prepared as single phases via the solid state route and NPD experiments are carried out at Wombat and at Echidna at OPAL. [1] Y. Tokura et al., Adv. Mater. 22, 1554 (2010). [2] R. Feyerherm et al., Phys. Rev. B 73, 180401 (R)(2006). 58 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 [3] M. Kenzelmann et al., Phys. Rev. Lett. 95, 087206 (2005), G. Lawes et al., Phys. Rev. Lett. 95, 087205 (2005). [4] M. Kenzelmann et al., Phys. Rev. Lett. 98, 267205 (2007). [5] R.D. Johnson et al., Phys. Rev. Lett. 107, 137205 (2011), J. Hwang et al., Phys. Rev. Lett. 109, 257205 (2012). 59 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Exploring the Properties of Complex Layered Tin Cluster Compounds M. Allisona, S. Liub, C. Lingb, G. Stewartc and T. Söhnela a School of Chemical Sciences, University of Auckland, New Zealand. b School of Chemistry, University of Sydney, NSW, Australia. c School of PEMS, UNSW@AFDA, Canberra, Australia. Layered oxide structures have been observed to strongly show effects such ferroelectricity and giant magnetoresistance in semiconducting materials. Oxide materials containing Fe, Mn and Co have additionally been shown to exhibit novel multiferroic properties which could be extremely beneficial for future data storage devices. The parent compound for this presentation Fe4Si2Sn7O16 [1] provides a novel situation in oxide compounds. It can be described as a composite of intermetallic (FeSn6) clusters and (FeO6)/(SnO6) oxide layers within the one structure. SiO4 tetrahedra separate these layers which leads to electronic and magnetic isolation of the repeated layers by about 7 Å resulting in a nearly perfectly 2D oxide system comparable to a one layer thick oxide “thin film”. In this study we have systematically replaced the iron positions of the oxide layer in the parent compound with divalent Mn in order to study the change in material properties. Refinements of the structures from Synchrotron and neutron powder diffraction patterns determined changes in lattice parameters which indicate that the MSn6 octahedral layer in these materials may contain manganese instead of iron. 57Fe-Mössbauer spectra (Fig. 1) seem to confirm a clear preference of Mn sitting in the oxide layers and Fe in the cluster layers. In this presentation we will show the current results into the effects this elemental substitution has on the crystal and magnetic structures of this family of compounds, additionally we will present some of the novel results from the spectroscopic and magnetic characterisation of these materials. Figure 1. Crystal structure (left) and 57Fe- Mössbauer spectra of FeFe3-xMnxSi2Sn O . 7 16 [1] T. Söhnel, P. Böttcher, W. Reichelt and F.E. Wagner, Z. Anorg. Allg. Chem. 624, 708 (1998). 60 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Low-temperature magnetic structure of Ca2Fe2O5 determined by single- crystal neutron diffraction J.E. Aucketta, G.J. McIntyreb, M. Avdeevb and C.D. Linga a School of Chemistry, The University of Sydney, NSW 2006, Australia. b Bragg Institute, ANSTO, NSW 2232, Australia. Ca2Fe2O5 is a canted antiferromagnet (TN = 720 K) which displays an anomalous elevation in its magnetic susceptibility for 60 K < T < 140 K. [1] Based on susceptibility measurements performed on oriented single crystals, Zhou et al. [2] proposed a reorientation of the antiferromagnetic (AFM) easy-axis from the crystallographic a axis to the c axis below 40 K, proceeding via a region of minimal magnetocrystalline anisotropy in the anomalous temperature interval. In order to test this proposition, we have refined the atomic and magnetic structure of Ca2Fe2O5 against high-quality neutron Laue diffraction data collected on floating-zone-grown single crystals between 10 K and 300 K. An ad hoc sample mount was designed to apply a small (~35 Oe) magnetic field to the sample, ensuring perfect compatibility with the magnetic susceptibility data, which were also collected in a small field. Our refinements against both zero-field and in-field diffraction data reproduce the G-type AFM structure of Ca2Fe2O5 excellently at room temperature, including the known ferromagnetic canting. Careful examination of the refinement results reveals that the material is in fact best described by the room-temperature magnetic structure at all measured temperatures, though in the intermediate temperature interval (measured at T = 100 K) the spins may be less well-ordered due to competing sublattice interactions. [1] A. Maljuk, J. Strempfer and C.T. Lin, J. Cryst. Growth 258, 435 (2003). [2] H.D. Zhou and J.B. Goodenough, Solid State Sci. 7, 656 (2005). 61 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnetoelectric coupling in isotopically subtituted TbMn16/18O3 and RMn2O5 (R = Tb, Ho, and Y) explored by Raman light scattering P.J. Grahama, P. Rovillaina,b, A.M. Muldersc, M. Yethirajb, D. Argyrioud E. Pomjakushinae, K. Condere, M. Kenzelmanne and C. Ulricha,b a School of Physics, University of New South Wales, New South Wales 2052, Australia. b The Bragg Institute, ANSTO, Lucas Heights, NSW 2234, Australia. c School of PEMS, UNSW Canberra, Canberra, ACT 2600, Australia. d European Spallation Source ESS AB, S-22100 Lund, Sweden. e Paul Scherrer Institute, CH-5232 Villigen, Switzerland. Multiferroic materials demonstrate excellent potential for next-generation multifunctional devices, as they exhibit coexisting ferroelectric and magnetic orders. In magnetoelectric multiferroics, the existing coupling between both properties offers a unique possibility to manipulate ferroelectricity via magnetic order and vice versa opening unexpected new potential for high-density information storage and sensor applications. At present, the underlying physics of the magnetoelectric coupling is not fully understood, and competing theories propose conflicting experimental outcomes. By studying the lattice and magnetic excitations via Raman light scattering, we have obtained insight into the various coupling mechanism in multiferroic materials like TbMnO3 and RMn2O5 (R = Tb, Ho, and Y). Raman light scattering experiments were performed on TbMn16/18O3 oxygen-isotope- substituted single crystals. Pronounced anomalies in sign and strength of the phonon shifts at the magnetic phase transition at 43 K and the ferroelectric phase transition at 28 K indicate an interaction between the lattice and the magnetic and electric ordering, providing information about the nature of the competing magnetic interactions present in this compound. Our Raman light scattering experiments on RMn2O5 (R = Tb, Ho, and Y) revealed opposite spin-phonon interactions for R = magnetic Tb and Ho, in contrast to non-magnetic Y. This offers a unique insight in the various competing spin exchange interactions, which lead to the highly frustrated spin structure and finally the multiferroic properties of RMn2O5. Using single crystal neutron diffraction at high magnetic fields (up to 11 T) we were able to determine a theoretically proposed but hitherto unobserved crystallographic phase transition, which naturally explains the origin of the ferroelectric polarization. 62 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Stress Controlled Metal-to-Insulator Transitions in Thin Film Vanadium Oxides J. Laverocka, A.R.H. Prestona, D. Newby, Jr.a, K.E. Smitha,b, S. Sallisc, L.F.J. Piperc, S. Kittiwatanakuld, J. Lue, S.A. Wolfd,e, M. Leanderssonf and T. Balasubramanianf a Department of Physics, Boston University, Boston, Massachussetts,USA. b School of Chemical Sciences, University of Auckland, Auckland, New Zealand. c Department of Physics, Binghamton University, Binghamton, NY,USA. d Department of Physics, University of Virginia, Charlottesville, VA, USA. e Department of Materials Science and Engineering, University of Virginia, VA,USA. f MAX-lab, Lund University, SE-221 00 Lund, Sweden. The metal-insulator transition (MIT) in VO2 is of both fundamental and technical interest, the former due to important lingering questions about its origins, and the latter due to possible applications in electronic devices such as ultrafast optical switches. In bulk VO2, a structural distortion accompanies the transition from the metallic (rutile) to the insulating (monoclinic) phase, which is known to impose a significant bottleneck on the timescale of the transition. Recently, the ability to control the transition temperature through chemical doping and/or nanoscale engineering has heralded renewed interest in the potential application of VO2 as a novel functional material. Whereas the mechanism of the MIT in bulk VO2 is now reasonably well understood, the situation is less clear with a large applied strain to the lattice. I will present the results of synchrotron radiation-excited photoemission, x-ray emission, and x-ray absorption spectroscopy studies of the MIT in strained VO2 thin films. Our results reveal that the MIT may be driven towards a purely electronic transition, (i.e. one which does not rely on the Peierls dimerization), by the application of mechanical strain. Comparison with a moderately strained system, which does involve the lattice, demonstrates a crossover from Peierls-like to Mott-like transitions. Our observations have important implications for novel functional material engineering of VO2, suggesting a route towards circumventing the structural bottleneck in the ultrafast timescale of the MIT. Research supported in part by the U.S. Department of Energy under Grant No. DE-FG02- 98ER45680. 63 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Freudenbergite – a New Example of Electron Hopping J.D. Cashiona, A. Lashtabegb, E.R. Vancec, D.H. Ryand and J. Solanoe a School of Physics, Monash University, Melbourne, Victoria 3800, Australia. b Nanolytical, PO Box 21, The Gap, Brisbane, Qld 4061, Australia. c Australian Nuclear Science and Technology Organisation, Menai, NSW 2234, Australia. d Physics Department, McGill University, Montreal, Québec H3A 2T8, Canada. e School of Chemistry, Monash University, Melbourne, Victoria 3800, Australia. We have recently [1] found that samples of freudenbergite with a mixed ferric-ferrous composition exhibit considerable electron hopping at room temperature as evidenced in 57Fe Mössbauer spectra. Freudenbergite is most commonly ferric with composition Na 3+2Fe 2Ti6O16, but can be ferrous, Na2Fe2+Ti7O16, with a complete solid solution possible between these end members. Since both iron and titanium can have two valences, it is of importance to understand whether the electron hopping is between neighbouring Fe2+ and Fe3+ ions or whether it involves titanium in the form Fe2+ + Ti4+ ↔ Fe3+ + Ti3+. To try and distinguish between these possibilities, we will discuss the differences in the optical reflectance spectra between the black, electron hopping samples and the grey-green static samples. In addition, we will show new Mössbauer spectra for different freudenbergite compositions. Application of a magnetic field of 1.6 T did not change the proportion of the electron hopping contribution. The measured hyperfine field was enhanced above the applied field for both sites. Without the applied field, the ferrous contribution had to be fitted to two doublets, possibly representing the M1 and M2 sites, but with the applied field, they were able to be fitted as a single contribution. For the ferric sites, the M1 and M2 contributions were indistinguishable in both cases. On strongly heating a mixed valence sample, nearly half the iron was expelled as hematite, while the remainder was still contained as a titanate. [1] J.D. Cashion, A. Lashtabeg, E.R. Vance and D.H. Ryan, Hyperfine Interact. (2013) DOI: 10.1007/s10751-013-0964-9. 64 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Crystal and magnetic structure of Li2MnSiO4 and Li2CoSiO4 characterized by neutron diffraction measurement Z. Mohameda,c, M. Avdeevb and C.D. Linga a School of Chemistry, The University of Sydney, NSW 2006, Australia. b Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia. c Faculty of Applied Sciences, Universiti Teknologi MARA, 40450 Shah Alam, Malaysia. Lithium orthosilicates compounds Li2MnSiO4 and Li2CoSiO4 were synthesized by solid state reaction and characterized using X-ray powder diffraction, magnetic susceptibility measurement, heat capacity and neutron powder diffraction. The magnetic susceptibility measurement shows that Li2MnSiO4 and Li2CoSiO4 obey Curie Weiss behaviour at high temperature and undergo antiferromagnetic ordering below TN = ~12 K and ~13 K respectively. The magnetic structures of both compound have been solved for the first time using low temperature neutron diffraction data. The results reveal that the magnetic structure of Li2CoSiO4 can be described as antiferromagnetic quasi-layers stacked along the a-axis with the magnetic moment ~2.92 µB aligned parallel to the a-axis. The magnetic structure of Li2MnSiO4 showed quite different behaviour compared to Li2CoSiO4. The origin of this complex magnetic structures will be discussed in terms of super-superexchange interactions among the transition metal ions, mediated by bridging SiO4 tetrahedra. Figure 1. (a) Crystal and (b) Magnetic structure of Li2CoSiO4. Co atoms are cyan, Si are blue, Li are green and O are red. [1] C. Masquelier and L. Croguennec, Chem. Rev. 113, 6552 (2013). [2] A. West and F. Glasser, J. Solid State Chem. 4, 20 (1972). 65 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Exotic Physics in Neutron Laue Diffraction G.J. McIntyrea a Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia. Neutron Laue diffraction has been reborn thanks largely to the success of X-ray Laue diffraction for protein crystallography at synchrotrons and to the development of efficient large-area image-plate detectors. The Laue technique with thermal neutrons is proving very successful for small-molecule crystallography on crystals frequently no larger than 0.1 mm3, first on VIVALDI at the Institut Laue-Langevin in Grenoble, France [1], and now on KOALA on the OPAL reactor at ANSTO in Lucas Heights, Australia [2], and is opening neutron diffraction to fields of structural chemistry previously deemed impossible [3]. The high-resolution volumetric view of reciprocal space is particularly advantageous in the detection of phase changes, incommensurability and twinning, but does come at a price though: all scattering from the sample, inelastic as well as elastic, contributes to the observed Laue patterns. This can however reveal valuable physical information about the sample beyond the crystal structure, but careful analysis is required to extract the details in the two- dimensional projection intrinsic to Laue patterns. Examples of exotic physics in neutron Laue diffraction experiments described here include: • Rods of scattering from two-dimensional magnetic ordering [4] • Observation of phonon scattering and determination of sound velocities • Observation of quasi-Kossel lines in experiments with diamond-anvil cells • Spin polarization of hydrogen nuclei to reduce the incoherent background in crystallographic studies of samples with high hydrogen content [5] [1] G.J. McIntyre et al., Physica B 385-386, 1055-1058 (2006). [2] N. Sharma et al., J. Phys.: Conf. Ser. 251, 012028 (2010). [3] A.J. Edwards, Aust. J. Chem. 64, 869-872 (2011). [4] E.M.L. Chung et al., J. Phys.: Condens. Matter 16, 7837-7852 (2004). [5] F. Piegsa et al., J. Appl. Cryst. 46, 30-34 (2013). 66 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Condensed phase studies at the THz/Far-IR Beamline at the Australian Synchrotron D. Appadooa, C. Ennisa and R. Plathea a The Australian Synchrotron, 800, Blackburn Rd, Clayton, VIC 3168, Australia. The THz/Far-IR beamline at the Australian Synchrotron is coupled to a Bruker IFS125HR FT spectrometer equipped with a variety of optical components which can cover the spectral range from 5 to 5000 cm-1. Experiments from a variety of fields such as atmospheric and astrophysical science, geology, electrochemistry, nano-materials as well as biology have been successfully conducted at the beamline. There is a range of instruments to accommodate the diverse requirements of the User community. For gas-phase experiments, the beamline is equipped with multiple-pass optics gas-cells: one of which can be coupled to a furnace to study reactive species, while another can be cooled to liquid nitrogen or helium temperatures to study aerosols and cold gases. Users also have access to a couple of cryostats (one > 79 K, the other > 6 K), a grazing incidence angle optical setup and a near-normal accessory to study condensed phase systems, thin films and surface interactions. The synchrotron infrared light offers a S/N advantage over conventional thermal sources, but this advantage varies to a great degree upon the spectral range, sample size and resolution dictated by the application. In this paper, the capabilities and performance of the THz/Far-IR beamline at the Australian Synchrotron will be presented as well as some applications undertaken at the beamline, and future developments. 67 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Status Report on SIKA – Taiwan’s Cold Neutron Triple-Axis Spectrometer at OPAL C.M. Wua, G. Dengb and J.S. Gardnera a National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan. b Bragg Institute, ANSTO, Lucas Heights, NSW, Australia. We will report on the current status of SIKA, the triple-axis spectrometer with the view of the cold source from the reactor beam hall in OPAL, at ANSTO. SIKA is funded by the National Science Council of Taiwan and currently being commissioned by the National Synchrotron Radiation Research Center. To provide the flexibility for scientific applications, SIKA’s analyser can operate in a flat or in a multiplexing mode when coupled to the one-dimensional PSD consisting of 48 vertical position-sensitive wires, allowing the simultaneous data collection over a specified range in (Q, E). This analyser can also operate in a horizontal focusing mode that directs the scattered neutrons into a single-detector. The entire analyser-detector system as is packed into a single, well shielded secondary spectrometer housing which significantly reduces the background. As a state-of-the-art triple-axis spectrometer, SIKA is also equipped with a full automated sample stage and a series of collimations (both soller and radial). Neutron polarisation will be available for the incident and scattered beams through 3He polarisers. [1] www.ansto.gov.au/research/bragg_institute/facilities/instruments/sika [2] www.ansto.gov.au/discovering_ansto/anstos_research_reactor/opal_capabilities/ cold_neutron_source [3] www.ncnr.nist.gov/instruments/bt7_new/BT7Instrument.pdf [4] W.G. Williams, Polarized Neutrons, Clarendon Press, Oxford (1988). 68 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Polarised Neutrons for Materials Sciences Research at the Australian Nuclear Science and Technology Organisation (ANSTO) W.T. Leea, A. Studera, K. Rulea, S. Danilkina, D. Yua, R. Molea, S. Kennedya, E. Gilberta, K. Wooda, F. Klosea and T. D’Adama a Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia. Polarised neutron scattering has been used extensively to study magnetism in materials. Diffraction allows us to resolve the distribution and orientation of the magnetic moments down to the atomic scale. Inelastic scattering studies the magnetic excitations. The complex magnetic structure in magnetic nanoparticles is a hot topic for Small Angle Neutron Scattering (SANS). Novel magnetic thin film and multilayer are the sujects of neutron reflectometry. The technique is also increasingly being used to significantly enhance the signal-to-noise ratio in SANS measurement of hydrogen-rich materials. At ANSTO, polarised neutron option is currently available on both the SANS instrument “Quokka” (incident beam) and the reflectometer “Platypus” (incident and scattered beam). Recent technological advance of polarised Helium-3 based neutron spin-filter technique has opened up the possibility of using polarised neutrons on a wider range of instruments. In addition to enhancing the capabilities of Quokka (both incident and scattered beam for hydrogen-rich material and magnetic nanoparticle studies) and Platypus (wide-angle analysis for e.g. patterned magnetic surface structure), we are installing and testing polarised neutron equipmetn on the diffractometer “Wombat” and inelastic-scattering instruments “Taipan”, “Pelican” and “Sika”. This new capability will become available for experiments from July 2014. Futhermore, a new supermirror polariser is being commissioned on Pelican for polarised inelastic scattering work. In this presentation, examples illustrating the technique and use of polarised neutron scattering and the current status of installation and test on instruments will be provided. 69 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Approaching Metallic Hydrogen by Stealth: Via the High-Hydrides N.W. Ashcrofta a Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, USA. A metallic phase of hydrogen has been experimentally detected under shock conditions. Underlying it is a familiar founding many-body problem of condensed matter and materials physics namely that of N spin-1/2 interacting electrons in a rigorously neutralizing homogeneous background; this yields the anti-ferromagnetic Wigner crystal at low density and a uniform paramagnetic electron fluid at high. A counterpart problem described by exactly the same physics arises for protons where, in addition to a change in all signs, the mass of these Fermions is increased over those of the electrons by a factor 1836. If these two macroscopic systems are taken to co-occupy a common volume V, and all mutual Coulomb interactions now included, the quantum problem of the first element (hydrogen), then ensues. It can therefore be established as two coupled Fermion problems and its states exhibit a rich array of orderings as temperature and density are progressively increased. A prominent state is the metallic phase of hydrogen occurring at high compression and which is present, for example, in our giant planets. However, the problem can also be extended to include the addition of a second or third element, and if in relatively small proportions this leads to the high-hydrides. Their materials properties are also rich and in structural terms they include the possibility of arrangements arising where the quantum mechanics of the protons are quite central; the consequences may be described as quantum dis-proportionation. Further, the arguments suggesting the possibility of superconductivity at high temperatures in metallic hydrogen (via the standard phonon pairing mechanism) have their close parallels in the high- hydrides. Additionally if the polarizabilities of the ions of the added second or third elements are high there is also the possibility of further enhancement via quantized waves of polarization. In this way materials can be developed which are predominantly hydrogen but which may achieve metallicity at pressures lower than required for pure hydrogen. Research supported by the US National Science Foundation. 70 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Exploring Jupiter’s icy moons with old techniques and big facilities – new insights on sulfuric acid hydrates H.E. Maynard-Caselya, M. Avdeeva, H.E.A. Brandb and K.S. Wallworka a Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia. b Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168, Australia. Sulfuric acid hydrates have been proposed to be abundant on the surface of Europa [1], and hence would be important planetary-forming materials for this moon and its companions Ganymede and Callisto. Understanding of the surface features and subsurface of these moons could be advanced by firmer knowledge of the icy materials that comprise them [2], insight into which can be drawn from firmer knowledge of physical properties and phase behaviour of the candidate materials. We wish to present results from a study that started with the question ‘What form of sulfuric acid hydrate would form on the surface of Europa?’, with this study undertaken with in situ powder diffraction at Australian Synchrotron and ANSTO. We have used the Powder Diffraction beamline at Australian synchrotron [3] and the Echidna (High-resolution neutron powder diffraction) instrument of the Australian Nuclear Science and Technology Organization, [4] to obtain a number of new insights into the crystalline phases formed from H2SO4/H2O mixtures. These instruments have enabled the discovery a new water-rich sulfuric acid hydrate form [5], improved structural characterisation of existing forms [6] and charting of the phase diagram of this fundamental binary system [7]. This has revealed exciting potential for understanding more about the surface of Europa from space, perhaps even providing a window into its past. [1] R.W. Carlson et al., Science, 286, 97 (1999). [2] A.D. Fortes et al., Space Sci. Rev., 153, 185 (2010). [3] K.S. Wallwork et al., AIP Conf. Proc., 879, 879 (2007). [4] Liss, K.D., et al., Phys. B – Cond. Mat., 385, 1010 (2006). [5] H.E. Maynard-Casely et al., J. Geophys Res: P, 118, 1895 (2013). [6] H.E. Maynard-Casely et al., J. App.Cryst., 45, 1198 (2012). [7] H.E. Maynard-Casely et al., Icarus (In Review). 71 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Large room temperature magnetoresistance in nanogranular materials J. Leveneura, G.V.M. Williamsb, J. Kennedya,b, T. Prakasha and P.P. Murmua a National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt 5010, New Zealand. b The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, Victoria University, PO Box 600, Wellington 6140, New Zealand. Magnetoresistance and spin transport have raised a lot of interest in the past decades as they allow for the miniaturisation of high sensitivity magnetic field sensors and new electronic devices [1]. Magnetoresistance can occur in nanogranular materials and have different origins. For instance, spin tunnelling magnetoresistance happens when two ferromagnetic nanoparticles with some degree of electronic spin polarisation are separated by a thin insulator layer. This leads to a negative magnetoresistance that saturates for high magnetic fields. Lorentz-force like and geometric mechanisms lead to positive magnetoresistances and can show no saturation for magnetic fields as high as 9 T [2,3]. However, the magnetoresistance behaviour is often complex and can involve more than one mechanism as well as depending strongly on the investigated systems. Therefore, there is an interest in developing further magnetoresistive nanomaterials in order to improve our understanding of the underlying mechanisms. In this report we present the results from structural, magnetic and magnetotransport measurements on several nanogranular systems. They were made by low energy ion implantation and electron beam annealing, arc-discharge, and chemical methods. Ferromagnetism and superparamagnetism were observed. The resultant magnetoresistance mechanisms with be discussed that include spin tunnelling magnetoresistance and a Lorentz force like magnetoresistance arising from the current injection region. [1] I. Žutić, J. Fabian and S. Das Sarma, Rev. Mod. Phys. 76, 323 (2004). [2] F. Xiu, Y. Wang, K. Wong, Y. Zhou, X. Kou, J. Zou, and K.L. Wang, Nanotechnology 21, 55602 (2010). [3] J. Leveneur, J. Kennedy, G.V.M. Williams, J. Metson, and A. Markwitz, Appl. Phys. Lett. 98, 053111 (2011). 72 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnetic order in gadolinium manganite probed by 155Gd-Mössbauer spectroscopy G.A. Stewarta and G. Wortmannb a School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, Australian Defence Force Academy, PO Box 7916, Canberra BC 2610, Australia. b Department of Physics, University of Paderborn, Paderborn 33098, Germany. The orthorhombic manganites RMnO3 (R = Gd, Tb, Dy) remain of considerable research interest because of their multiferroic behaviour. From an experimental point of view, GdMnO3 differs from the others in that Gd is an extremely strong absorber of neutrons and is not amenable to neutron diffraction investigations of its magnetic structure. Nevertheless, from bulk single crystal magnetization [1] and x-ray diffraction measurements [2], we know that the Mn moments first undergo a transition to an incommensurate (sinusoidal collinear) arrangement at TIC = 42 K. Below TCA = 20 K, they then lock into a canted A-type antiferromagnetic (AFM) structure with weak ferromagnetism (FM) in the b-direction (Pnma notation). It was also concluded that the Gd moments order magnetically in their own right at TGd = 6 - 7 K [1]. More recently, x-ray magnetic resonant scattering (XMRS) was used to probe the local moment at the Gd site [2]. It was confirmed that the Gd moments order at TGd ≈ 7 K with a possible further modification of the magnetic structure at about T* = 4 - 5 K. In this present work, 155Gd-Mössbauer spectroscopy is used to probe the magnetic hyperfine field at the 155Gd nucleus. The magnetic exchange field increases markedly at TGd and the Gd3+ moment at 1.8 K is evidently close to its saturation value of 7 µB. A simple point charge model estimate of the lattice electric field gradient generates likely alignments of the Gd moment. These are then compared with predictions based on the earlier magnetisation and XRMS data [1,3]. [1] A.B. Hemberger, Phys. Rev. B 40, 024414 (2004). [2] T. Arima, T. Goto, Y. Yamasaki, S. Miyasaka, K. Ishii, M. Tsubota, T. Inami, Y. Murakami and Y. Tokura, Phys. Rev. B 72, 100102(R) (2005). [3] R. Feyerherm, E. Dudzik, A.U.B. Wolter, S. Valencia, O. Prokhnenko, A. Maljuk, S. Landsgesell, N. Aliouane, L. Bouchenoire, S. Brown and D.N. Argyriou, Phys. Rev. B 79, 134426 (2009). 73 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Enigma of Resonant Inelastic X-ray Scattering (RIXS) data for cuprates O.P. Sushkova a School of Physics, University of New South Wales, New South Wales 2052, Australia. There have been a dramatic progress in RIXS techniques over the pastdecade. RIXS data for cuprate superconductors became available during pasttwo years. The data map magnetic excitations in the energy range larger than 100meV and for all possible doings, from undoped to overdoped. The magnetic excitations are completely unexpected and contradict to allexisting theoretical models. The contradiction is especially strong in theoverdoped regime which previously was thought to be close to the Normal Fermi Liquid. I will overview the RIXS data and explain what is striking in the data from the theoretical point of view. 74 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Upper critical and irreversible fields of polycrystalline CeFeAsO1-xFx superconductors S.V. Chonga, G.V.M. Williamsb and S. Sambalea,b a MacDiarmid Institute for Advanced Materials and Nanotechnology, Callaghan Innovation Research Ltd., P.O. Box 31310, Lower Hutt 5040, New Zealand. b MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington, New Zealand. We have investigated the upper critical field (Hc2), irreversible field (Hirr) and critical current density (Jc) of polycrystalline samples of Ce oxypnictide at different doping levels (x = 0.13 to 0.25). Hc2 was obtained from temperature dependent resistivity measurements with increasing applied magnetic field. Critical field values as high as 150 Tesla were observed with a decreasing trend as the doping level shifts from a slightly under-doped state to the highly over-doped region. The irreversible fields of as-prepared polycrystalline samples were lower in this superconductor compared with other rare-earth oxypnictides, with values below 3 Tesla at 20 K. However, Hirr in the magnetic-field aligned samples with the c-axis parallel to the applied magnetic field show a much higher Hirr when compared with non-aligned samples. Furthermore, Hirr and the coherence length, ξ(0) were found to increase with increasing doping. The origin of irreversibility was studied by determining the exponent ‘n’ extracted from plots of log10(Hirr) versus log10(1-T/T nc) . We found that Hirr follows a 3D vortex lattice- melting model similar to the other low anisotropic iron-based superconductors. Preliminary Jc measurements from field-loop magnetization measurements show intragrain self-field Jc values as high as 106 A/cm2, which is consistent with that previously found in underdoped (x = 0.10) Ce-oxypnictide [1]. [1] S.V. Chong, T. Mochiji, S. Sato and K. Kadowaki, J. Phys. Soc. Japan: Suppl. C 77, 27 (2008). 75 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Phonons in a highly-correlated electron system: the heavy-fermion superconductor CeCu2Si2 M. Loewenhaupta, S. Danilkinb, L. Capognac, A. Schneidewindd, O. Stockerte and K. Hradilf a Institut für Festkörperphysik, Technische Universität Dresden, 01062 Dresden, Germany. b Bragg Institute, ANSTO, Kirrawee DC, NSW 2232, Australia. c Institut Laue-Langevin, 38042 Grenoble Cedex 9, France. d Jülich Center for Neutron Science at FRM II, 85747 Garching, Germany. e Max-Planck-Institut für Chemische Physik fester Stoffe, 01186 Dresden, Germany. f Röntgenzentrum, TU Wien, 1060 Wien, Austria. CeCu2Si2 crystallizes in the tetragonal ThCr2Si2-type structure with 5 atoms in the primitive unit cell. It exhibits non-conventional superconductivity driven by low-energy magnetic excitations [1]. The Ce3+ Hund’s rule J=5/2 ground state is split by the action of the crystalline electric field into 3 doublets, with two excited doublets forming a quasi-quartet at around 30 meV [2]. Except for Raman data [3] no information about the lattice dynamics was available up to date. We therefore performed inelastic neutron scattering at low temperatures (3 K and 10 K) on a large single crystal on the thermal triple-axis spectrometers PUMA (FRM II) and TAIPAN (OPAL) to determine the phonon dispersion relations in the [001/110] plane. The measured dispersion curves will be compared with ab-initio DFT calculations. In addition we could refine the crystal field level scheme resulting in the observation that the excited quasi- quartet actually consists of two considerably broadened doublets situated at around 28 meV and 35 meV, respectively. [1] O. Stockert, J. Arndt, E. Faulhaber, C. Geibel, H. S. Jeevan, S. Kirchner, M. Loewenhaupt, K. Schmalzl, W. Schmidt, Q. Si and F. Steglich, Nature Physics 7, 119 (2011). [2] E.A. Goremychkin and R. Osborn, Phys. Rev. B 47, 14280 (1993). [3] S.L. Cooper, M.V. Klein, Z. Fisk and J. L. Smith, Phys. Rev. B 34, 6235 (1986). 76 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The thermodynamics of high-Tc superconductors J. Tallona a Robinson Research Institute, Victoria University of Wellington, P.O. Box 31310, Lower Hutt 5040, New Zealand. Thermodynamics presents a powerful theoretical tool which imposes strong constraints on spectroscopic behaviour independent of microscopic mechanism. This is particularly the case for superconductors. This talk will focus on high-temperature superconductors and will illustrate how: (i) thermodynamics can uncover normal-state behaviour that would occur if superconductivity could be suppressed, (ii) the crucial effects of impurity scattering on suppressing superfluid density and transition temperature can be fully accounted for, again with no recourse to microscopic mechanism, (iii) energy gaps in the density of states can be extracted, and (iv) the most important property for applications, critical current density, can be specified as a function of temperature and doping. 77 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 ABSTRACTS Poster Presentations Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 First–principle study of palladium-defect pairing in doped Si A.A. Abionaa,* and H. Timmersa a School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra Campus, ACT 2602, Canberra, Australia. The electric field gradient (EFG) measured by hyperfine interaction techniques, e.g. time- differential perturbed angular correlation (TDPAC), provides relevant information about the interaction of probe atoms like 100Pd/100Rh with other defects. TDPAC study of palladium (Pd) in doped Si identified two possible Pd-defect pairings. Pd-vacancy pairing was observed in n-type Si irrespective of the dopant (P, As and Sb) type while Pd-B pairing was observed in B-doped p-type silicon [1, 2]. In Ge, however, TDPAC measurements confirmed that Pd pairs with vacancy in both n- and p-type dopants (Sb and Ga) [3]. The question that arises is why is Pd pairing with dopant in p-type Si but with vacancy in p-type Ge? TDPAC data interpretation and assigning of a particular defect configuration to the EFG of the defect complex is a very difficult task. This paper aims at complementing the understanding of the pairing of Pd with defects in silicon using Density Functional Theory (DFT). The DFT calculations confirmed the observed palladium-defect pairing in both the n- and p-type Si. However, the Pd atom is located on bond-centred site in Si instead of on the substitutional site as observed in n-type Si. Based on the calculations, we deduce that Pd occupies the interstitial site to pair with B in B-doped Si because of the small atomic size of B relative to its host material Si. [1] R. Dogra et al., Hyperfine Interact. 177, 33 (207). [2] R. Dogra et al., J. Electron. Mater. 38, 623 (2009). [3] A.A. Abiona, W. Kemp and H. Timmers, Hyperfine Interact. 221, 65-72 (2012). * On leave from Centre for Energy Research and Development, Obafemi Awolowo University, Ile-Ife, Nigeria. 78 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 M/TiO2 Photocatalysts (M=Au, Pd, Pt and Au-Pt) for H2 Production from Ethanol-Water Mixtures Z.H.N. Al-Azria,b and G.I.N. Waterhousea,b a School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. b The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand. In this study, the activity of M/TiO2 photocatalysts (M = Au, Pd, Pt and bimetallic Au-Pt) for hydrogen (H2) production from ethanol-water mixtures (80 vol.% CH3CH2OH) under UV irradiation was investigated and compared. Metal loadings were in the range 0-4 wt.%. Nanocrystalline TiO2 (Evonik P25, SBET = 50 m2g-1) was used as the support phase. Results demonstrate that the photocatalytic activity of M/TiO2 photocatalysts for H2 production from aqueous ethanol solutions depends on many factors, including (i) the metal co-catalyst; (ii) the metal loading on the TiO2 support; (iii) the oxidation state of the noble metal, and (iv) the strength of the metal-support interaction (MSI) [1,2]. Pd/TiO2 photocatalysts exhibited the highest activity for H2 production, with the optimum loading being ~0.5 wt.% (H2 production rate of 49 mmol g-1 h-1). For Pt/TiO2 and Au/TiO2 photocatalysts, the optimum metal loadings were 1 wt.% and 2 wt.%, respectively, which afforded similar H2 production rates (33-35 mmol g-1 h-1). Bimetallic Au-Pt/TiO2 photocatalysts showed lower H2 production activity compared to either Au/TiO2 or Pt/TiO2 photocatalysts, indicating that no synergy exists between the co-loaded metals under the applied test conditions. TEM data showed that the Pd and Pt cocatalysts were highly dispersed over the TiO2 support, with an average particle size less than 2 nm. For Au/TiO2, the MSI was weaker and thus the average metal nanoparticle size was larger (6 ± 2 nm) and the metal nanoparticle more spherical in shape. XPS analyses confirmed the presence of zero valent metal on the surface of the photocatalysts. The noble metal co-catalysts function as an electron sinks to suppress electron-hole pair recombination in TiO2 (confirmed through photoluminescence measurements) as well as provide active centres for photocatalytic H2 generation. [1] M.A. Nadeem, M. Murdoch, G.I.N. Waterhouse, J.B. Metson, M.A. Keane, J. Llorca and H. Idriss, J. Photochem. Photobiol. A–Chem. 216, 2-3 (2010). [2] V. Jovic, Z. Al-Azri; W-T. Chen, D. Sun-Waterhouse, H. Idriss, G.I.N. Waterhouse, Top. Catal. 56, 12 (2013). 79 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Spin-reorientation in DyGa R.A. Susiloa, J.M. Cadogana, R. Cobasa, S. Muñoz-Péreza and M. Avdeevb a School of Physical, Environmental and Mathematical Sciences, UNSW Canberra at the Australian Defence Force Academy, Canberra, ACT, BC2610, Australia. b Bragg Institute, ANSTO, PMB 1, Menai, NSW 2234, Australia. The RGa compounds crystallize in the orthorhombic CrB-type structure (Cmcm space-group), which can be viewed as a stacking of trigonal prisms along the crystallographic a-axis with rare earth atoms at the corners and the gallium atoms nearly at the centres. They order ferromagnetically with a Curie temperature ranging from a high of ~187 K in GdGa to a low of 15 K for TmGa. DyGa is a ferromagnet with a Curie temperature (TC) of 115(2) K. Based on single-crystal susceptibility measurements by Shohata [1], the easy direction of magnetic order was found to be along the c-axis. Recently, Zhang et al. [2] reported a weak shoulder at ~25 K in their magnetization data, which might correspond to a spin-reorientation . In this report, we present our neutron diffraction results to investigate the magnetic ordering of DyGa. Despite the substantial neutron absorption by the Dy (50 at.% of the sample), refinement of our neutron diffraction patterns confirms the c-axis order below TC. Furthermore, upon cooling below 25 K we observe a canting of the Dy moments away from the c-axis towards the a-axis. At 3 K, the Dy moment is 9.8(2) µB and the Dy magnetic moments point in the direction θ = 22(2)° with respect to the crystallographic c-axis. [1] N. Shohata, J. Phys. Soc. Japan 42, 1873 (1977). [2] X.Q. Zheng, J. Chen, J. Shen, H. Zhang, Z.Y. Xu, W.W. Gao, J.F. Wu, F.X. Hu, J.R. Sun and B.G. Shen, J. Appl. Phys. 111, 07A917 (2012). 80 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 90° Magnetic Coupling in a NiFe/FeMn/biased NiFe Spin Valve Investigated by Polarised Neutron Reflectometry S.J. Calloria,b, T. Zhuc and F. Klosea a School of Physics, University of New South Wales, Sydney 2052, Australia. b Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights NSW 2234, Australia. c Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China. We have used the PLATYPUS reflectometer at ANSTO to perform polarised neutron reflectometry in order to investigate 90° magnetic coupling in a Ni81Fe19/Fe50Mn50/biased Ni81Fe19 spin valve system. Spin valves play an important role in current and developing technological systems, such as spintronics devices or magnetoresistive sensors. For the later usage, perpendicular coupling in a spin valve structure leads to a desired linear, reversible resistance response to an applied magnetic field. The spin valve presented here consists of both free and exchange biased ferromagnetic Ni81Fe19 layers, the later of which is pinned by an antiferromagnetic Ir25Mn75 layer at low applied magnetic fields. The free Ni81Fe19 may be magnetically reversed under low fields, and standard magnetometry measurements on similar systems have suggested perpendicular orientation of the free and biased magnetisations at zero field [1]. Magnetometry measurements, however, are only capable of providing information about the magnetisation within a sample along the direction of the applied field. In contrast, polarised neutron reflectometry (PNR) is capable of resolving the in-plane magnetisation vectors both along and perpendicular to the applied magnetic field as function of layer depth. Here, PNR was used to obtain magnetic vector depth profiles of the spin valve at several applied fields, including low fields near the switching point of the free Ni81Fe19 layer. At these fields a large spin-flip signal was observed in the free layer, indicating magnetisation aligned perpendicular to the external field applied along the pinned layer magnetisation. Both the non-spin flip and spin-flip signals were also tracked around the free layer hysteresis loops and can be used to map the evolution of the free Ni81Fe19 layer during magnetic reversal. [1] T. Liu, T. Zhu, J.W. Cai and L. Sun, J. Appl. Phys. 109, 094504 (2011). 81 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Synthesis and Characterisation of 3DOM ZIF-8 Thin-Films for Optical Gas Sensing Applications H.K. Chahala, G.M. Miskellya and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. By combining the inherent microporosity and high surface area of metal organic frameworks (MOFs) with the tuneable optical properties of photonic crystals, new and improved optical sensors could potentially be developed. This study describes the successful fabrication of three- dimensionally ordered macroporous (3DOM) ZIF-8 photonic crystal thin-films using the colloidal crystal templating technique. Colloidal crystal thin films comprising mondisperse carboxylate-terminated polystyrene (PS-COOH) colloids of diameter ~300 nm arranged on a face centred cubic lattice were first prepared. ZIF-8 nanoparticles were then grown in the interstitial voids of the colloidal crystal films, by immersion of the template in an aqueous solution containing Zn2+ and 2-methylimidazole (MeIM). Finally, the polymer template was removed by chemical etching in dimethylformamide (DMF) yielding iridescent 3DOM ZIF-8 photonic crystal films with high specific surface area (1767 m2 g-1). The optical properties of the 3DOM ZIF-8 films could be tuned by changing the diameter of the PS-COOH colloids used to prepare the templates. The photonic band gap (PBG) along the [111] direction red- shifted reversibly on exposure to alcohol vapours, suggesting these materials could be useful in gas sensing applications. (a) (b) 50 524 nm 543 nm 545 (b) 40 540 30 535 20 530 10 525 0 450 500 550 600 650 0 2 4 6 8 10 Wavelength (nm) Cycle Figure 1. UV-Vis reflectance spectra of (a) 3DOM ZIF-8 thin film before and after exposure to saturated ethanol vapour. The PBG position is red-shifted upon ethanol sorption (b) Plots showing the PBG shift over repeat cycles of ethanol vapour and nitrogen gas exposure. 82 % Reflectance Peak Position (nm) Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Novel M-Pt/C (M = Ru, Sn, RuSn) Electrodes for Direct Alcohol Fuel Cells M. H. Chana and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, New Zealand. Direct methanol fuel cells (DMFCs) have attracted considerable attention as power sources due to their simplicity and high energy conversion efficiency. Strong economic and environmental pressures exist to develop efficient DEFCs since ethanol is renewable biofuel. This project is aimed at fabrication of novel M-Pt/C anode materials for DMFCs and DEFCs. Ru, Sn and Pt nanoparticles (total metl loading typically 5-20 wt.%) were deposited on 3- dimensionally ordered macroporous carbons fabricated by the colloidal crystal template technique, and the performance of the resulting M-Pt/C (M = Ru, Sn or both) anode materials systematically evaluated through electrochemical studies of ethanol oxidation in acidic media. XPS, XRD and TEM analyses confirmed the presence of metallic Pt, Ru and Sn on graphite like surface of the carbon support (BET area 800 m2 g-1 in the absence of metal). Cyclic voltametry studies of methanol and ethanol oxidation in acidic media show the Pt/C materials fabricated are excellent electrocatalysts, with the electrocatalytic activity for alcohol oxidation increasing linearly with Pt loading in the range 0-15 wt.%. The electrocatalytic activity could be further enhanced through the introduction of Ru (1-2 wt. %) and Sn (1-2 wt. %) as promoters, whilst keeping the total metal content fixed at 10 wt.%. Electrocatalyst activity for methanol and ethanol oxidation decreased in the order RuSn-Pt/C > Ru-Pt/C > Sn-Pt/C > Pt/C. Pt can also be easily poisoned by CO formed from the electrooxidation of alcohols, but the presence of Sn and Ru on the electrocatalyst surface facilitate the oxidation of CO to CO2, which explains the high electrocatalytic activity realised in the trimetallic RuSn-Pt/C system. 0.06 Pt / C RuSn-Pt/C Peak 1 0.04 Peak 2 0.02 0.00 0.0 0.2 0.4 0.6 0.8 1.0 1.2 E / V v s . A g/AgCl Figure 1. SEM of 3DOM Carbon (left) and CV for CH3OH oxidation in acidic media (right). 83 Current Density / Acm-2 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Ni/TiO2 – A low cost photocatalyst system for H2 Production from Biofuels W.-T. Chena and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, New Zealand. Ni/TiO2 photocatalysts (Ni loadings 0-4 wt.%) were prepared by the complex precipitation method [1], H2 reduced at 500 oC, characterised and evaluated for H2 production from ethanol-water mixtures under UV excitation. Degussa P25 TiO2 (85 wt.% anatase, 15 wt.% rutile) was used as the support phase. TGA, XRD, UV-Vis and XPS measurements provided evidence for the presence of metallic Ni nanoparticles on the surface of the photocatalysts, though the Ni nanoparticles were very small (< 2nm) and highly dispersed over the oxide support and thus difficult to observe by TEM. The Ni/TiO2 photocatalysts were very active for H2 production from ethanol-water mixtures under UV excitation, with the optimal Ni loading being ~0.5 wt.% (H2 production rate = 33.4 mmol g-1 h-1). High H2 production rates were achieved over a wide range of ethanol concentrations. The 0.5 wt.% Ni/TiO2 photocatalyst displayed superior photocatalytic activity to a standard reference photocatalyst, 2 wt.% Au/TiO2, at ethanol concentrations between 1-30 vol.%, which may be due to the higher dispersion of the active metal co-catalyst realised in the Ni/TiO2 system. Results suggest that Ni/TiO2 is a promising low cost alternative to noble metal-based photocatalysts for solar H2 production from biofuels. 35 60 (a) 2 wt.% Au/TiO2 (b) 30 50 0.5 wt.% Ni/TiO2 25 40 20 30 15 20 10 10 5 0 0 0 1 2 3 4 0 20 40 60 80 100 wt.% Ni loading Vol% EtOH Figure 1. (a) H2 production rate versus Ni loading for various Ni/TiO2 photocatalysts in ethanol-water mixtures (80 vol.%) under UV excitation (b) H2 production rates versus ethanol concentration for 0.5 wt.% Ni/TiO2 photocatalyst and 2 wt.% Au/TiO2 photocatalyst under UV excitation. [1] L.S. Yoong, F.K Chong and B.K. Binay, Energy 34, 1652 (2009). 84 H2 production rate (mmol g -1 h-1) H2 production rate (mmol g -1 h-1) Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Enriching the properties of Mo-oxide layered hybrids with electron-rich zigzag fused aromatic spacer molecules I. u-dina,b, S.V. Chongb, S.G. Telfera, G.B. Jamesona, M.R. Waterlanda and J.L. Tallonb a MacDiarmid Institute for Advanced Materials and Nanotechnology, Institute of Fundamental Sciences, Massey University, Private Bag 11222 Palmerston North 4442, New Zealand. b MacDiarmid Institute for Advanced Materials and Nanotechnology, Callaghan Innovation Research Ltd., P.O. Box 31310, Lower Hutt 5040, New Zealand. For the first time 3,8-phenanthroline, a zigzag fusion of 3 benzene rings, has been employed as a bridging ligand to develop a system of layered organic-inorganic hybrid materials. The resulting materials exhibit two (2-D) and three dimensional (3-D) covalently bonded hybrid frameworks constructed from single and bimetallic inorganic oxide layers interlinked by organic ligands. This opens up possibilities for developing new materials by introducing different magnetic ions within the inorganic layers and the incorporation of other hetero- polycylic aromatic organic spacers in-search for improved magnetic properties and even superconductivity in these hybrid materials [1]. Here we report the synthesis and properties of 2-D (I) MoO3-(3,8-phenanthroline)0.5 and (II) MoO3-(3,8-phenanthroline)0.3+δ, and 3-D (III) CuMoO4-(3,8-phenanthroline)0.5 hybrids. Raman measurements correlate very well to the structural data and illustrate that how small changes in crystal structure can have significant effects on vibrational characteristics of the hybrid network. Compound II with ~0.33 phenanthrolines appears to be self-doped compared with I, while the insertion of Cu2+ ions within the inorganic layers in III seems to induce antiferromagnetic behaviour in the otherwise diamagnetic material. We also observed a heat capacity peak in zero field at around 8 K and diamagnetic (magnetization) transitions at ~12 K under very low applied magnetic field in III, which might be associated to magnetic orders caused by the different oxidation states of Cu or the compound is superconducting with a very low upper critical field. [1] S.V. Chong and J.L. Tallon, “Novel layered organic/inorganic hybrid materials”, New Zealand Provisional Patent # 615066 (4 September 2013). 85 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Inorganic/Organic Composites for X-ray Imaging N. Wincha and A. Edgara a School of Chemical and Physical Sciences, Victoria University, Welllington, New Zealand. X-ray imaging is widely used in medicine, dentistry, security, and materials inspection. Traditionally, imaging has been done using a photographic film – phosphor screen combination, but over the past two decades, this has been progressively replaced by various imaging plate technologies. One such technology is that of storage phosphors, where incident x-rays falling on a storage-phosphor imaging-plate generate electrons and holes, some of which are locally trapped. Recombination is stimulated by incident red light, and the resulting blue recombination emission I(x,y), which is proportional to the incident X-ray intensity, is recorded across the plate so as to extract an X-ray image of any object placed in the x-ray beam. Currently, the highest performance storage phosphor is CsBr, doped with europium, but as made the material is completely inactive. It must be first thermally processed in the presence of water vapour so as to generate a high concentration of the active recombination centre, whose detailed structure [1,2] is still a matter of some debate, but which appears to involve a Eu2+ - H2O atomic centre. However, whilst the material has an outstanding X-ray sensitivity, the spatial resolution remains inferior compared to other rival techniques due to light scattering of the stimulating and emitted light from the powdered CsBr grains in the plate. We have earlier described how a higher resolution, transparent, non-scattering form can be made by pressing [3] , and how it can be used with a simple image read-out process [4]. In this paper, we describe an alternative process in which the CsBr is chemically modified so as to refractive-index match an organic polymer binder. The materials science design and thermal and spectrocsopic properties of the composite are discussed and the performance of the resulting organic/inorganic composite prototype imaging plates is presented. [1] H. F. Vrielink, F. Loncke et al., Phys. Rev. B, 83, 054102 (2011). [2] G. Appleby, H. von Seggern et al., J. Appl. Phys. 109, 013507 (2011). [3] N.M. Winch and A. Edgar, Phys. Stat. Solidi A 209, 2427 (2012). [4] N.M. Winch and A. Edgar, Nucl. Instrum. Meth. A 654, 308 (2011). 86 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Mechanical Properties of Tungsten Copper Composites: Direct Measurement by Neutron Diffraction P.J. Mignonea,b, T.R. Finlaysona,b, S. Kabrac, S-Y. Zhangc, G.V. Franksa,b and D.P. Rileyb,d aDepartment of Chemical and Biomolecular Engineering, University of Melbourne, Vic., 3010, Australia. bDefence Materials Technology Centre, Hawthorn, Vic., 3122, Australia. cCCLRC Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, England. dAustralian Nuclear Science and Technology Organisation, Lucas Heights, N.S.W., 2234, Australia. The composite W-10 wt%Cu (19.35% by volume, assuming neglegible porosity) has been studied using the ENGIN-X beamline at the ISIS pulsed neutron source at the Rutherford Appleton Laboratory. An as-machined, compression sample was initially measured in order to check for the presence of residual stresses in the composite, using a mixed powder sample of the same elemental weight fractions as the “zero stress” comparison. Then a series of mechanical tests were carried out on the composite for applied compressive loads up to 250 MPa at both room temperature and 100ºC and compared with similar tests carried out on pure tungsten and copper samples. Residual stress values of -280 MPa (for the tungsten matrix) and 480 MPa (for the copper particulate phase) were measured for the as-machined sample. This is a surprising result, given that the yield stress for copper is typically less than 100 MPa but is not inconsistent with residual stresses reported in the literature for W-Cu composites [1]. The mechanical properties for the composite have also been determined from the results of these in-situ, mechancial tests and compared with finite element calculations based on microstructural models for the composite material [2]. [1] T. Wieder, A. Neubrand, H. Fuess and T. Pirling, J. Mater. Sci. Letts. 18, 1135 (1999). [2] P.J. Mignone, M. Wang, T.R. Finlayson, D.P. Riley and G.V. Franks, Mater. Sci. Eng. A (2013) (in press). 87 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Novel SERS substrates for the Identification of Adulterants in Milk P.-H. Hsieha, D. Sun-Waterhousea and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, New Zealand. Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that attracts interest in chemistry and biology for the detection of low concentration analytes. SERS enhancement factors as high as ~1010-1011 have been reported for highly optimised Au and Ag substrates [1], however the low general reproducibility of SERS substrates is an obstacle to the SERS technique’s widespread use in routine quantitative analyses. The development of stable and sensitive SERS active substrates is a priority. This research explores the fabricationa and viability of novel SERS substrates, comprising Au nanoparticles immobilised on 3-dimensionally ordered macroporous (3DOM) Si1-xTixO2 supports. Here we present preliminary data relating to the fabrication and optical characterisation of such SERS substrates. Results show that Au nanoparticles of various size (predominantly < 10 nm) may be successfully deposited on 3DOM Si1-xTixO2 supports at high loadings (up to 70 wt.% Au). The Au localised surface plasmon resonance and photonic bandgap along the [111] direction in the 3DOM supports red-shifted linearly with increasing solvent refractive index, which means that in addition to acting as SERS substrates these materials can also be used for solvent refractive index sensing. Thus, the described materials have potential as multi- functional optical sensing elements. Current work is being directed towards evaluation of the SERS activities of the Au/3DOM Si1-xTixO2 substrates in milk-related systems. 1000 PBG SPR 900 Regression 800 700 600 500 1.0 1.1 1.2 1.3 1.4 1.5 nsolvent Figure 1. Au/3DOM Si1-xTixO2 substrate (left) and Au LSPR and PBG shift versus solvent refractive index (right). [1] B. Sharma, R.R. Frontiera, A.-I. Henry, E. Ringe and R.P. Van Duyne, Mat. Today 15, 16 (2012). 88 ! (nm) Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 ESR studies of Magnetocaloric PrMn2−xFexGe2 Q.Y. Rena, W.D. Hutchisona, J.L. Wangb,c and S.J. Campbella a School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT 2600, Australia. b Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522, Australia. c Bragg Institute, Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW 2234, Australia. In a recent paper, we investigated the magnetic structures, phase transitions and magnetocaloric entropy of PrMn1.6Fe0.4Ge2 by a combination of bulk magnetometry, 57Fe Mössbauer spectroscopy and electron spin resonance (ESR) over the temperature range 5-300 K [1]. This work followed on from a broader study of the PrMn2-xFexGe2 family of compounds [2], in which it was found that with decreasing temperature from the paramagnetic region, three magnetic phase transitions have been detected for PrMn1.6Fe0.4Ge2. The transition temperatures and related magnetic structures (using the notation of [3]) the magnetic structures are [1]: (i) paramagnetism to intralayer antiferromagnetism (AFl) at T intra=370 K; (ii) AFl to canted ferromagnetism (Fmc) at T interN C ∼230 K, and (iii) a third transition around T PrC ∼30 K with ferromagnetic ordering of the Pr sublattice resulting in the combined magnetic region (Fmc+F(Pr)). Here the ESR, focusing on the Pr3+ 4f magnetic moment and undertaken in the vicinity of the lowest transition temperature, is the subject of further analysis in order to correlate the observed resonant line/s and changes in g-factors with the phases mentioned above. In particular an aim is to link the increase in g factor of the Pr3+ ion (from g = 0.85 in the region above T PrC ∼30 K to g ~ 2.5 at 8 K) with the bulk moments measured via DC magnetisation. [1] W.D. Hutchison, J.L. Wang and S.J. Campbell, Hyperfine Interact. 221, 35 (2012). [2] J.L. Wang, S.J. Campbell, A J Studer, M Avdeev, M Hofmann, M Hoelzel and S X Dou, J. Appl. Phys. 104, 103911 (2008). [3] G. Venturini, R. Welter, E. Ressouche and B. Malaman, J. Magn. Magn. Mater. 150, 197 (1995). 89 Proceedings+–+38th+Annual+Condensed+Matter+and+Materials+Meeting+–+Waiheke+Island,+Auckland,+NZ,+2014! Investigation of the order parameter of Pr in the filled skutterudite PrRu4P12 by soft resonant x-ray diffraction F. Lia, A.M. Muldersa, W.D. Hutchisona, M. Garganourakisb, Y. Tanakac, K. Nishimurad and H. Satoe a School of Physical, Environmental and Mathematical Sciences, The University of New South Wales, Canberra, ACT, 2600, Australia. b Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland. c RIKEN SPring-8 Center, Harima Institute, Sayo, Hyogo 679-5148, Japan. d Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan. e Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan. The filled skutterudite PrRu4P12 which shows a metal-insulator (MI) transition at 62.3 K has attracted some attention recently since the origin of the MI transition is not yet well understood [1-6]. Given that no MI transition is observed in LaRu4P12 [7] implies that the Pr 4f electrons have an integral role. In this study the order parameter associated with the Pr 4f shells in PrRu4P12 is investigated via soft resonant x-ray diffraction in combination with x-ray absorption spectroscopy at the Pr M4,5 edges, utilising the dipolar transition 3d → 4f . A resonance enhancement of the (100) superlattice reflection at the Pr M4,5 edges signalling the order parameter of the Pr ions was observed below TMI and underwent a steady increase upon temperature decreasing. The experimental spectra and subsequent analysis rule out the existence of magnetic, charge or orbital order as well as any Pr lattice displacement however imply that the resonant diffraction signal arises in essence from the two different crystal field environments of the Pr 4f electrons. [1] C. Sekine, T. Uchiumi and I. Shirotani, Phys. Rev. Lett. 79, 3218 (1997). [2] C.H. Lee, H. Matsuhata. A. Yamamoto, T. Ohta, K. Ueno, C. Sekine, I. Shirotani and T. Hirayama, J. Phys.: Condens. Matter 13 L45 (2001). [3] C. Sekine, T. Inaba, M. Yokoyama, H. Amitsuka and T. Sakakibara, Physica B 281-282 303 (2000). [4] C.H. Lee, H. Oyanagi, C. Sekine, I. Shirotani and M. Ishii, Phys. Rev. B 60 13253 (1999). [5] K. Ishii et al., J. Magn. Magn. Mat. 310 e178 (2007). [6] S. Kong, W. Zhang and D. Shi, New J. Phys. 10 093020 (2008). [7] S.R. Saha, H. Sugawara, Y. Aoki, H. Sato, Y. Inada, H. Shishido, R. Settai, Y. Onuki and H. Harima, Phys. Rev. B 71 132502 (2005). 90 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 The magnetic properties of Nd2Sn2O7 P. Imperiaa, R.J. Aldusa, K.C. Rulea and A. Studera a ANSTO, The Bragg Institute, Australia. In this paper we will discuss the magnetic properties of the pyrochlore Nd2Sn2O7 as measured with the neutron scattering instruments Wombat and Taipan at the Bragg Institute neutron scattering facility. The measurements were conducted on a polycrystalline sample in zero magnetic field and 10 Tesla. The sample, loaded in OFHC copper can, was mounted into a dilution insert and measured between 340 mK and 50 K. The results indicated that the material doesn’t spontaneously magnetically order. However, upon application of the magnetic field, the sample is easily polarised. Achieving ultra-low temperature with a powder samples is a difficult task. Here we will discuss common strategies used to improve conductivity in the mK range and the implication for this particular study. The equipment available at the neutron scattering instruments of Bragg Institute for measurements in high magnetic fields and low temperature will be also illustrated. 91 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Structure and Magnetism Studies of Cu1-xCoxSb2O6 Solid Solution H.-B. Kanga, C. Lingb and T. Söhnela a The University of Auckland, School of Chemical Sciences, Private Bag 92019, Auckland, New Zealand. b The University of Sydney, School of Chemistry, NSW 2006, Sydney, Australia. CuSb2O6 is the most widely studied structure in the ternary Cu-Sb-O system. The structure and magnetism of CuSb2O6 have been studied intensively revealed due to the discovery of high Tc copper oxides. Doping of Co into CuSb2O6 is designed to investigate two factors. Firstly, it seems not possible to have a direct phase transition from a tetragonal trirutlie modification to a monoclinic modification; subsequently at least an orthorhombic modification should exist between the two modifications. Secondly, it is very interesting how the magnetic behavior changes from 1D magnet (CuSb2O6) to 2D magnet (CoSb2O6) by replacing the transition metal on the A site of the trirutile structure. CuSb2O6 shows a phase transition from tetragonal trirutile structure to a monoclinic distorted structure at around 100 °C to 130 °C due to the Jahn-Teller distortion of Cu2+ (d9-system) [1]. The magnetic behavior of CuSb2O6 is considered as S=1/2 one-dimensional Heisenberg antiferromagnets (HAF) with strong anisotropy in the square Cu-sublattice above 20 K [2]. CoSb2O6 crystallizes in the tetragonal trirutile structure (Fig.1) showing a two-dimensional HAF behavior [3]. Co doping on the A site of CuSb2O6 helps to investigate how the structural phase turns from the monoclinic modification into the tetragonal trirutile modification and we could observe a possible orthorhombic modification between the two phases by Synchrotron X-ray powder diffraction. Assuming that CuSb2O6 adopts the tetragonal trirutile structure based on CoSb2O6 above 130 °C, a complete solid solution should be revealed. However, high synchrotron powder measurements at 200 °C and even at 500 °C indicate that this is not the case. A possible orthorhombic modification can be found from all Cu1-xCoxSb2O6 solid solutions except CoSb2O6 at 200 °C. Two different structures can be found between CuSb2O6 and Cu0.7Co0.3Sb2O6 on one side and Cu0.7Co0.3Sb2O6 and CoSb2O6 on the other side Figure 1. Crystal structure of at 500 °C. It could be considered that CuSb2O6 is still distorted CoSb2O6 refined on single crystal neutron data. even at 500 °C. 92 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 CuSb2O6 exhibits a S = ½ one dimensional Heisenberg antiferromagnet (HAF) with strong anisotropy in the square Cu-sublattice above 20 K [2] whereas CoSb2O6 exhibits two dimensional HAF [3]. According to the magnetic susceptibilities of Cu1-xCoxSb2O6, it is possible to investigate that the magnetic behavior of all compounds except CuSb2O6 are similar to CoSb2O6. It seems like the magnetic behavior of CuSb2O6 can be turned into the 2D magnet behavior with a very small amounts of Co doping. Figure 2. The Rietveld refinement of X-ray synchrotron data of Cu0.7Co0.3Sb2O6 [1] J.G. Bednorz and K.A. Müller, Z. Phys. B. 64, 189 (1986). [2] A.V. Prokofiev, F. Ritter, W. Assmus, B.J. Gibson and R.K. Kremer, J. Cryst. Growth. 247, 457 (2003). [3] J. N. Reimers, J. E. Greedan C. V. Stager, and R. Kremer, J. Solid State Chem. 83, 20 (1989). 93 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Magnon mediated superconducting pairing in the vicinity of magnetic quantum critical point Y. Kharkova and O.P. Sushkov a a School of Physics, University of New South Wales, New South Wales 2052, Australia. It has been recently established, both theoretically and experimentally, that cuprate superconductors have magnetic quantum critical point at about 10% doping. In the present work we consider a simplified theoretical model which allows to address a generic problem how magnetic quantum criticality influences superconducting pairing. We demonstrate that the paring is significantly enhanced in the vicinity of the critical point. 94 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Ferromagnetism of Co,Eu Co-doped ZnO and 5%-Co doped TiO2 Magnetic Semiconductors O.J. Leea, X. Luoa, W.T. Leeb, V. Lauterc, G. Trianib, S. Lia and J.B. Yia a University of New South Wales, Kensington, NSW, Australia. b Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia. c Oak Ridge National Laboratory, Oak Ridge, TN, USA. Diluted magnetic semiconductor has attracted wide interest due to its potential applications in spintronics devices. Oxide semiconductor based diluted magnetic semiconductors has been investigated in detail for possible ferromagnetism above room temperature. However, most of the diluted magnetic semiconductors show very weak ferromagnetism. The magnetic moment is originated from the doped magnetic element, such as Fe, Co, Ni. Rare-earth element, which shows strong spin-orbit coupling, may enhance the magnetic anisotropy of the diluted magnetic semiconductors, thus enhances the ferromagnetism. In this work, we used both Co and Eu to co-dope ZnO and deposited Co doped TiO2 thin films in order to achieve a diluted room-temperature magnetic semiconductor with strong ferromagnetism. 4%Co and 4%Eu or 6% Eu were used for the doping by implantation in ZnO and 5%Co-TiO2 film were deposited on LaAlO3 substrate under different oxygen partial pressures from 10-4 to 10-6 torr. For the ZnO-based thin films, XRD analysis indicates there is no secondary or impurity phase. Magnetic measurement by SQUID shows room temperature ferromagnetism. Polarized neutron reflectometry (PNR) analysis illustrates that ZnO film is 100 nm in thickness and the magnetic layers is around 30 nm, which is in consistent with the penetration depth of Co and Eu implantation, indicating the magnetic moment is due to the Co and Eu codoping. 4%Co, 4%Eu codoped ZnO film has a saturation magnetization of 3.57 emu/cm3, while 4%Co, 6%Eu codoped ZnO film has a saturation magnetization of 9.62 emu/cm3, indicating the significant enhancement of saturation magnetization by more rare earth element doping. For the TiO- based thin films, XRD analysis show epitaxial growth and that the films have anatase phases. TEM confirms the single crystal like microstructure. EDX mapping indicates that Co is uniformly distributed in the TiO2 matrix, suggesting effective doping of Co dopant. Magnetic measurement shows that film deposited under lower oxygen partial pressure has a larger saturation magnetization. PNR shows that the magnetization is uniformly distributed along the film thickness. The magnetization for the film deposited under an oxygen partial pressure of 10-6 torr is about 4.2 emu/cm3, which is much smaller than that measured by SQUID (30 emu/cm3). This suggests a magnetic dead layer on the film surface. 95 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Temperature dependence of structural parameters of the layered magnetic glass Fe0.5Ni0.5PS3 D.J. Goossensa, W.T. Leeb and A.J. Studerb a Australian National University, Canberra, ACT, Australia. b Australian Nuclear Science and Technology Organisation, Lucas Heights, NSW, Australia. The layered magnetic materials of the MPS3 family (M=2+ metal) show a wide range of behaviours. Recently, magnetic glassiness, with a relaxation time of the order of an hour, was observed in Fe0.5Ni0.5PS3 [1]. The relaxation depends on sample history, both thermal and applied magnetic field. Here some aspects of the behaviour of the magnetic and crystal structure with temperature and field are explored using the Wombat powder diffractometer at ANSTO (Figure 1). Diffuse scattering can be seen to decrease as temperature falls and to fall sharply at the magnetic transition, and at different scattering vector Q to the magnetic Bragg peaks. This suggests a short-range ordered magnetic structure with different spin-spin correlations to the long-range ordered structure. Figure 1. Temperature-dependent neutron scattering from Fe0.5Ni0.5PS3. White arrows indicate magnetic Bragg reflections that vanish at TN, noted by the dotted line. [1] D.J. Goossens, S. Brazier-Hollins, D.R. James, W.D. Hutchison and J.R. Hester, J. Magn. Magn. Mater. 334, 82 (2013). 96 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Generalization of the Onsager quantization condition for spin-orbit coupled systems T. Lia and O.P. Sushkov a a School of Physics, University of New South Wales, New South Wales 2052, Australia. The oscillating resistivity of metals in magnetic field was explained by Onsager as a manifestation of quantum interference. Assuming that there are no coupled internal degrees of freedom, a charged particle will accumulate a phase when moving through a full loop in space, and this phase appears in the semi-classical expression for the energy spectrum. We present the extension of the semiclassical theory to spin systems in which both the orbital dynamic and internal dynamics are present, which implies that particle will acquire a total rotation in the internal space over a full loop. We demonstrate that for spin-½ systems, this allows the precessional dynamic of spin to be recovered from magnetic oscillations, and compare results of our theory with recent experiment. 97 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Characterization of the carboxyl groups in graphene oxide C. Lianga, G. Xua and J. Jina a School of Chemical Sciences, University of Auckland, Auckland 1010, New Zealand. The graphite oxide and graphene oxide (GO) have attracted researcher’s interest sustainably after it was first synthesized by Brodie in 1859 due to its outstanding chemical, physical and biological properties as well as served for precursor of chemically converted graphene. The new material has been sparked and largely focuses on optoelectronics transistors, bio-devices, energy storage devices and polymer nanocomposites. Although graphene oxide has been utilised and investigated for more than a century, the accurate structure of graphene oxide remains unclear and elusive. The structure analysis of graphene oxide has been one of the difficult problems in the field of carbon material sciences. One reason is that graphene oxide has a variety of compositions depending on the different synthetic methods and conditions, although it is simply composed of C, H and O. Another reason is that considering the huge size of graphitic platelets, current analysis techniques are not able to distinguish the accurate chemical groups and configuration in graphene oxide sheet. That often leads researchers to draw different conclusions even upon similar spectra results. Among the different chemical groups in graphene oxide, carboxyl groups are very critical and useful due to its unique properties. Carboxyl groups reflect the acidity[1], are relevant to solubility and stability[2] as well as a lot of chemical functionalization involving that[3]. Further understanding the properties of carboxyl group in graphene oxide can be very critical and useful for future research. Herein, we try to show the reactivity and density of carboxyl groups in surface and periphery of graphene oxide by using titration, UV, FTIR and solid state NMR. [1] A.M. Dimiev, L.B. Alemany and J.M. Tour, ACS Nano 7, 576 (2012). [2] D. Li et al., Nature Nanotech. 3, 101 (2008). [3] Z.-B. Liu et al., J. Phys. Chem. B 113, 9681 (2009). 98 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Designing new n = 2 Sillen-Aurivillius phases by lattice-matched substitutions in the halide and [Bi 2+2O2] layer S. Liua, P.E.R Blancharda, M. Avdeevb, B.J. Kennedya and C.D. Linga a School of Chemistry, The University of Sydney, New South Wales 2006, Australia. b The Bragg Institute, ANSTO, PMB 1, Menai 2234, Australia. The chemical and structural flexibility of the perovskite structure, which makes it so ubiquitous in nature and useful in a range of technological applications, extends to layered variants such as Ruddlesden-Popper, Dion- Jacobson and Aurivillius phases. Multi-layered variants such as the Sillen-Aurivillius phases are related to Aurivillius phases by the insertion of an additional halide layer between every second [Bi O ]2+2 2 layer [1]. Sillen-Aurivillius phases exist in various combinations of n number of perovskite layers and m halide layers. We have synthesised a new n = 2, m = 1 Sillen-Aurivillius compound Bi3Sr 2+ 2+2Nb2O11Br [2] based on Bi3Pb2Nb2O11Cl [3] by simultaneously replacing Pb with Sr and Cl- with Br-. Rietveld refinements against X-ray and neutron powder diffraction data revealed a significant relative compression in the stacking axis, in contrary to the belief of inserting a significantly larger halide layer in the new compound. We could not stabilise other combinations such as Bi3Sr2Nb2O11Cl and Bi3Pb2Nb2O11Br due to inter-layer mismatch. Sr2+ doping reduces the impact of the stereochemically active 6s2 lone pair found on Bi3+/Pb2+ site, resulting in a contraction of the stacking axis by 1.22 % and an expansion of the a-b plane by 0.25 %, improving inter-layer compatibility with Br-. XANES analysis shows that the ferroelectric distortion of the B-site cation is less apparent in Bi3Sr2Nb2O11Br compared to Bi3Pb2Nb2O11Cl. Variable-temperature neutron diffraction data show no evidence for a ferroelectric distortion. [1] B. Aurivillius, Chem. Scrip. 23, 143 (1984). [2] S. Liu, P.E.R. Blanchard, M. Avdeev, B.J. Kennedy and C.D. Ling, J. Solid State Chem. 205, 165 (2013). [3] A. M. Kusainova, P. Lightfoot, W. Z. Zhou, S. Y. Stefanovich, A. V. Mosunov and V. A. Dolgikh, Chem. Mater. 13, 4731 (2001). 99 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Thermoelectric Properties of Polycrystalline Gadolinium Nitride T. Maitya, H.J. Trodahla, B.J. Rucka, H. Warringa and F. Natalia a The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand. For decades, magnetic and semi-conducting elements have taken the centre stage in developments of the field of electronics. Recent attention has largely shifted towards producing devices using the electronic spin as well as charge degree of freedom. By manipulating these two properties, spintronics has great promise to avail devices with very high speeds, minimal power usage and added functionality. Ferromagnetic rare earth nitrides (RENs) have promising future in spintronics devices. Though our overall understanding of these materials has improved over the last decade, some fundamental questions about their conducting state are yet to be answered. Gadolinium nitride (GdN) has been widely studied REN to understand its ferromagnetic- ordering and electronic structure. A significant amount of research has been carried out on its magnetic, transport and optical properties but thermopower is yet to be investigated. Thermopower is a strong energy dependent transport phenomena, hence it provides critical insight of the material’s electronic properties and other excitations ( e.g phonon and magnon drag) with variable range of temperature and magnetic field. In this paper we present the first experimental investigation of the thermopower of polycrystalline gadolinium nitride, measured using an experimental set-up designed for measuring the temperature dependent thermopower of thin films inside a bath cryostat. Our initial reasult shows a negative thermopower, as expected because of the negative charge carriers, and strong temperature dependence. At low temperatures we observe a peak near the ferromagnetic transition temperature which is clearly correlated with ferromagnetic-ordering. The results will be interpreated in terms of the normal diffusion theropower and phonon/magnon drag contributions. 100 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Reflectometry as a tool for studying dye molecule orientation in dye- sensitised solar cells (DSCs) J. McCree-Greya,b and J.M. Colea a Cavendish Laboratory, University of Cambridge, UK. b Bragg Institute, ANSTO, Sydney, Australia. With world energy demand set to double by 2050,1 it is imperative that clean, efficient and cost-effective alternatives to fossil fuels are developed. Dye-sensitised Solar Cells (DSCs) are a positive step towards a low-cost, mass-producible source of photovoltaic power, with laboratory devices now capable of reaching efficiencies of up to 15%.2 Typical DSCs consist of a dye-sensitised semiconductor surrounded by a redox electrolyte and sandwhiched between two transparent, conductive substrates. The dye is the principle light adsorber, injecting photo-excited electrons into the semiconductor conduction band and giving rise to the cells electrical characteristics. The electron injection is enabled by the dye’s physical and electrostatic interaction with the semiconductor surface and the nature of this interaction can have a major impact on the cell’s performance. Many dye species have been trialled in DSCs in efforts to improve these characteristics, however, the fundamental properties of dye orientation and molecular packing on the semiconductor surface remain widely unknown. X-ray reflectometry (XRR) has already been successfully applied to this field of DSCs3 but application of reflectometry to a fully- functioning DSC has still yet to be realised. This presentation will discuss results obtained using X-ray reflectometry to study the dye-orientations and packing densities for a number of different dye systems. Further discussion on the development of procedures to then apply neutron reflectometry to study a fully functioning dye-sensitised solar cell will then be examined. [1] International Energy Agency Energy Technology Perspectives 2008 – Scenarios and Strategies to 2050 OECD/IEA (2008). [2] M. Lui, M. B. Johnston and H. J. Snaith, Nature 501, 395 (2013). [3] M. J. Griffith, M. James, G. Triani, P. Wagner, G. G. Wallace and D. L. Officer, Langmuir 27, 12944 (2011). 101 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Fabrication, Optical and Photocatalytic Properties of TiO2 Colloidal Crystals S.E. Parka and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, New Zealand. This study describes the successful fabrication and optical characterisation of TiO2 colloidal crystals, comprising monodisperse TiO2 colloids with diameters in the range 400-1100 nm arranged on a face-centered cubic lattice. Batches of monodisperse TiO2 colloids of different diameters were first fabricated by the dodecylamine-catalysed hydrolysis of titanium tetraisopropoxide (TTIP) in a methanol/acetonitrile/water solvent mixture. By varying the H2O:TTIP ratio, TiO2 colloids of different diameter were obtained. Gravitational sedimentation of the TiO2 colloids dispersed in ethanol yielded well-ordered TiO2 colloidal crystals (Figure 1). XRD, TEM and FT-IR analyses showed the as-prepared TiO2 colloids to be amorphous and containing significant amounts of dodecylamine. Direct calcination of the as-prepared colloids (or colloidal crystals) at 500oC yielded dense, low surface area (10 m2g-1) monodisperse anatase TiO2 colloids. Hydrothermal treatement of the as-prepared colloids, followed by calcination at 500oC, yielded monodisperse mesoporous, high surface area (80- 100 m2g-1) anatase TiO2 colloids. Calcination of the anatase TiO2 colloids at 700oC yielded monodisperse rutile TiO2 colloids. The optical properties of the TiO2 colloidal crystals were consistent with a modified Bragg’s law expression which considers refraction and diffraction of light in the TiO2 colloidal crystals. Decoration of the mesoporous, high surface area anatase TiO2 colloids with Au or Pd nanoparticles (yielded Au/TiO2 and Pd/TiO2 photocatalysts with excellent activities for H2 production from ethanol-water mixtures under UV excitation. 40 Mesoporous anatase As-prepared colloidal crystal colloidal crystal 30 20 10 0 800 1000 1200 1400 1600 Figure 1: (left) TEM image for a mesoporous anatase TiO2W avceloenlgltho (indm) prepared at H2O:TTIP=10; (centre) SEM image of fcc(111) plane of the corresponding TiO2 colloidal crystal; (right) UV-Vis spectrum for the TiO2 colloidal crystal showing a photonic band gap along the [111] direction at nm. 102 Reflectance (%) Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Alkali metal and alkaline earth metal oxide materials for high temperature CO2 absorption and desorption studies A.F. Pavana and C.D. Linga a School of Chemistry, University of Sydney, NSW 2050, Australia. Novel ceramic materials that are able to absorb CO2 at high temperatures (>500OC) have gained wide attention in recent years regarding their stability over a large number of cycles over a range of high temperatures [1,2]. Such ceramics have been considered for use in combustion chambers and in the smoke stacks of power plants where combustion gases, containing a mix primarily of CO2 and N2, exist at high temperature. Compared to other CO2 sequestration technologies, these ceramics have both advantages (eg. can be fit to existing power plants) and disadvantages (eg. limited kinetics) [3]. My research involves the synthesis and CO2 absorption studies of ceramics; specifically, alkali metal and alkaline earth metal oxides. Examples of materials already known to show significant CO2 absorption include Li5AlO4 [4], Li6Zr2O7[5], Na2ZrO3[6] and Ba4Sb2O9[7]. The aim is to investigate the phase formations and structural evolution of these metal oxides under CO2 conditions over the temperature range 873–1173 K. Previous work has focused on the identification of phases ex situ and studies of their practical absorption capacity and kinetics. My work aims to understand both how the process works and how the structural evolution of the phases affects the CO2 sorption of the materials over time in-situ [8]. 103 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 [1] B.N. Nair, R.P. Burwood, V.J. Goh, Nakagawa and K.T. Yamaguchi, Prog. Mater. Sci., 54, 511 (2009). [2] S. Choi, J.H. Drese and C.W. Jones, Chem.Sus.Chem. 2, 796 (2009). [3] E. Favre, J. Membr. Sci. 294, 50 (2007). [4] L. Tatiana, Ávalos-Rendón and H. Pfeiffer, Energy Fuels 26, 3110 (2012). [5] S. Wang, C. An and Q.H. Zhang, J. Mater. Chem. A. 1, 3540 (2013). [6] L. Martínez-Cruz and H. Pfeiffer, J. Phys. Chem. C 116, 9675 (2012). [7] M.T.Dunstan, A.F. Pavan, V.V. Kharton, M. Avdeev, J.A. Kimpton, V.A. Kolotygin, E.V. Tsipis and C.D. Ling, Solid State Ionics, 235, 1 (2013). [8] S.J. Friedmann, Elements, 3, 179 (2007). 38th Annual Condensed Matter and Materials Meeting, Waiheke Island, Auckland, NZ 104 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Characterisation of permalloy and magnetite nanopowders T. Prakasha,b, G.V.M. Williamsa, J. Kennedya,b, P.P. Murmub, J. Leveneurb, S.V. Chongc, P. Couturea,b and S. Rubanovd a The MacDiarmid Institute for Advanced Materials and Nanotechnology, SCPS, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand. b National Isotope Centre, GNS Science, PO Box 31312, Lower Hutt 5010, New Zealand. c Callaghan Innovation Research Limited, PO Box 31310, Lower Hutt 5010, New Zealand. d University of Melbourne, Inst Bio21, Melbourne, Victoria 3010, Australia. Magnetic nanoparticles are being actively researched because of the potential applications that include magnetic storage [1] and magnetic sensors [2]. Very small nanoparticles can be superparamagnetic where there is no hysteresis [3]. This can be advantageous in magnetic sensor applications and can allow for very small magnetic fields to be measured. They can also display a magnetoresistance [4], which can be used in magnetic sensing applications. In this report we present the results from structural, Raman, magnetic, and magnetoresistance measurements on magnetic nanopowders made by arc-discharge and chemical methods. We show that permalloy and magnetite nanopowders can be made by arc-discharge and they contain a fraction of nanoparticles with dimensions below the superparamagnetic limit. We discuss changes to the arc-discharge setup that can lead to a higher fraction of superparamagnetic nanoparticles. The results are compared with similar measurements on magnetite made by a chemical method. [1] G.F. Goya, T.S. Berquo and F.C. Fonseca, J. Appl. Phys. 94, 3250 (2003). [2] J. Daughton, J. Brown, E. Chen, R. Beech, A. Pohm, and W. Kude, IEEE Transactions on Magnetics 30, 4608 (1994). [3] N.A. Spaldin, Magnetic Materials, Fundamentals and Device Applications (Cambridge University Press, Cambridge, England, 2003). [4] J. Leveneur, J. Kennedy, G.V.M. Williams, J. Metson, and A. Markwitz, Appl. Phys. Lett. 98, 053111 (2011). 105 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Molecular Dynamics Simulations of Thermal Condutivity of UO2, PuCrO3 and PuAlO3 M.J. Qina, E.Y. Kuoa, M. Robinsonb, N.A. Marksb, G.R. Lumpkina and S.C. Middleburgha a Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, Australia. b Nanochemistry Research Institute, Curtin University, Perth, Western Australia. The thermal conductivities of the PuCrO3 and PuAlO3 precipitates in UO2 fuel have been calculated using non-equilibrium molecular dynamics simulations. The PuCrO3 phase showed a markedly lower thermal conductivity than UO2, which will impact the microstructure, fission product distribution and gas release properties of UO2-based fuels. The PuAlO3, in both its orthorhombic and rhombohedral structures, showed greater thermal conductivity in comparison to PuCrO3, lower than UO2 at low temperatures but higher at elevated temperatures. Additions of Al with Cr to doped fuels is therefore likely to have a beneficial impact on the thermal conductivity of the fuel as opposed to solely doping with Cr. 106 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Influence of Plasma Impurities on the Effective Performance of Fusion Relevant Materials D.P. Rileya, M. Guenettea, A. Deslandesa, S. C. Middleburgh, G. Lumpkina, L. Thomsenb and C. Corrc a Institute of Materials Engineering, ANSTO, NSW, Australia. b Australian Synchtron, SXR, Victoria, Australia. c Research School of Physics & Engineering, ANU, ACT, Australia. The development of a sustainable source of power derived from fusion energy is presently constrained by the limited number of materials capable of operating under such extreme conditions. Plasma facing components within magnetically confined fusion reactors must withstand extremes of temperature and loads, while maintaining a high tolerance to radiation damage from energetic particles or neutrons. More specifically, factors of sputtering yield, thermal conduction, electrical conduction and retention of fuel can all degrade the performance of the reactor and hence detrimentally lower the efficiency. In aiming to improve our understanding of materials capable of operating within the fusion environment, it is essential to establish how present generation materials become degraded. Use of ion beam accelerators and linear plasma devices simulate the respective impact of energetic neutron damage (14.1 MeV) and plasma erosion (H+, D+, He+) within a magnetically confined fusion environment. Methods of characterising changes in the local structure and chemistry of surface and near surface regions of fusion relevant materials quantify material degradation resulting from the uptake of plasma impurities. While complementary density functional theory (DFT) simulations have identified possible mechanisms for degradation of material performance. An overview of material evaluation methods will also be presented. 107 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Novel Magnetic Properties of Rare-Earth Nitrides B.J. Rucka a The MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand. Most members of the rare-earth nitride series have been recognised as ferromagnetic for over 40 years, though there are some for which that has been confirmed only recently. Their electronic states have been less well characterised, with even basic questions such as whether they are metals or semiconductors adequately addressed only after recent advances in thin film fabrication. Several are now recognised as intrinsic ferromagnetic semiconductors. Here I will describe studies of the magnetic properties of several rare-earth nitrides based on magnetometry and x-ray magnetic circular dichroism, supported by transport measurements to elucidate the interplay between the electronic structure and the magnetic ordering. I will focus in particular on GdN (with zero orbital angular momentum), SmN (with almost zero net magnetic moment), and EuN. The magnetic transition temperature of GdN is independent of the carrier concentration over a large range, which we explain within a model based on magnetic polarons [1]. EuN should not be magnetic at all owing to the Hund’s rule ground state of the Eu3+ ion with J = 0, but we have found that EuN films prepared with a substantial concentration of nitrogen vacancies are ferromagnetic with transition tempertaure exceeding 100 K [2]. The magnetic moments originate from Eu2+ ions within the films, although both the 2+ and the 3+ ions show magnetic polarisation. [1] Do Le Binh, B.J. Ruck, F. Natali, H. Warring, H.J. Trodahl, E.-M. Anton, C. Meyer, L. Ranno, F. Wilhelm and A. Rogalev, Phys. Rev. Lett. 111, 167206 (2013). [2] F. Natali, B.J. Ruck, H. J. Trodahl, Do Le Binh, S. Vezian, B. Damilano, Y. Cordier, F. Semond and C. Meyer, Phys. Rev. B 87, 035202 (2013). 108 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 75As NMR of underdoped CeFeAsO0.93F0.07 S. Sambalea,b,c, D. Rybickic, G.V.M. Williamsa and S.V. Chongb a School of Chemical and Physical Science, Victoria University of Wellington, Wellington 6011, New Zealand. b Callaghan Innovation, Lower Hutt, New Zealand. c Faculty of Physics and Earth Science, Institute for Experimental Physics II, University of Leipzig, Leipzig, Germany. We report the results from a 75As NMR study of underdoped CeFeAsO1-xFx with x=0.07 that should be at the critical point between a spin density wave that occurs for x<0.07 and superconductivity that occurs for x>0.07. Contrary to the previous study on an overdoped and superconducting sample with x=0.20 [1], we find that there is only one As site, which suggests the absence of electronic phase sepration. The temperature dependent shift of the central transition is consistent with hyperfine coupling from magnetic Ce to As, which was also observed for x=0.20. Additional, we found an even higher 75As spin-lattice relaxation rate in x=0.07 when compared with x=0.20 that suggests an even stronger coupling to Ce. Our low temperature 75As NMR spectra for x=0.07 show a splitting of the central line that is also observed in a sample with x=0. The splitting is due to a spin density wave and indicates that the sample is magnetically spatially inhomogeneous. [1] D. Rybicki, T. Meissner, G.V.M. Williams, S.V.Chong, M. Lux and J.Haase, J. Phys.: Condens. Matter. 25, 315701 (2013). 109 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Influence of Oxygen on the Performance of Organic Field Effect Transistors L. Kehrera, A. Gassmanna, C. Melzera and H. von Seggerna a Electronic Materials Department, Institute of Materials Science, Technische Universität Darmstadt, Alarich-Weiss-Straße 2, 64287 Darmstadt, Germany. Functional stability of organic electronic devices such as organic field-effect transistors is still a great challenge for everyday use and a long way from being solved. The instability discussed here results from an oxygen defect, which is crucial for logic elements. In a logic circuit the OFETs are often held in the off-state, thus under depletion, where they change their properties and therewith the properties of the complete electronic circuit. In the present talk we report on the temporal behavior of oxygen based light- and field-induced defects in state- of-the-art poly(3-hexylthiophene), P3HT field-effect transistors. Experimentally a substantial shift of the threshold voltage and an increase in the off-current by three orders of magnitude has been reported when illuminating top-gate P3HT based field-effect transistors with visible light under forward gate bias [1]. Three time constants have been found at room temperature: two for the detrapping of electrons released from oxygen defects and one for the elimination of the oxygen defect itself. A set of rate equations will be shown to describe the behavior of the temporal development of the threshold voltage and the off-current of a P3HT transistor whilst the traps are optically filled as well as during the subsequent detrapping of electrons from the oxygen defects. In addition, the activation energies of the detrapping are determined. [1] L.A. Kehrer, S. Winter, R. Fischer, C. Melzer and H. von Seggern, Synth. Metals 161, 2558 (2012). 110 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Solar Hydrogen Production using Au/TiO2 Photocatalysts R. Shahloria and G.I.N. Waterhousea a School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. Semiconductor photocatalysis is one of the most promising future technologies for H2 production. In this study, a series of Au/TiO2 photocatalysts (Au loadings of 0.75, 1.5 or 3.0 wt.%) were fabricated using Degussa P25 TiO2 as the support phase, and then subjected to detailed characterisation by TEM (Figure 1), XRD, XPS, photoluminescence, UV-Vis spectrometry and H2 production tests (Figure 2). Results show that all the Au/TiO2 photocatalysts comprised Au nanoparticles of average size 4-6 nm uniformly distributed over the TiO2 support. Deposition of Au nanoparticles dramatically enhanced the photocatalytic activity of P25 TiO2 for H2 production from alcohol-water mixtures under UV irradiation, with the optimum Au loading being 1.5 wt.%. The Au nanoparticles serve as cathodic sites by accepting electrons photoexcited in TiO2, and then transferring them to water or aqueous protons to generate H2. The rate of H2 production over the 1.5 wt.% Au/TiO2 photocatalyst was stongly dependent on the nature of the alcohol used as a sacrificial hole scavenger in the H2 productions tests (Figure 2). Eleven different alcohol-water systems were tested, with diols (1,2-ethane diol and 1,2-butane diol) and triols (glycerol) being superior hole scavengers compared to primary, secondary or tertiary mono alcohols. The high hydrogen production rates achieved in this study suggests that Au/TiO2 photocatalysts are promising candidates for solar H2 production from water and biofuels at UV fluxes comparable to those in sunlight. 25 20 15 10 5 0 TEM for 1.5 wt.% Au/TiO2 Figure 1. H2 production rates for 1.5 wt.% Au/TiO2 photocatalyst in different alcohol-water mixtures (10 vol.% alcohol, UV flux 4 mW cm-2). 111 H2 produced (mmol g -1h-1cat ) Water Tertiary Butanol Butan-2-ol Butan-1-ol Glycerol 1,3-Propane diol 1,2-Propane diol Propan-2-ol Propan-1-ol Ethlyene Glycol Ethanol Methanol Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Electrical tuning of the hole Zeeman spin splitting in (100) Quantum wells A. Srinivasana, I. Farrerb, D.A. Ritchieb and A.R. Hamiltona a School of Physics, University of New South Wales, NSW 2052, Australia. b Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, United Kingdom. The Spin-orbit (SO) interaction has attracted great research interest of late, due to its potential application in spintronic devices, which aim to achieve all-electrical control of spin [1]. Quantum confined holes in GaAs heterostructures provide a rich playground for controlling and studying spin, due to the strong SO coupling in the valence band [2]. In particular, these systems allow electrical tuning of SO induced B=0 (Rashba) spin-splitting via the application of gate-biases [3]. Despite the great interest in these systems, a detailed understanding of the spin-orbit interaction and its effects on the spin of holes is far from complete. In particular there is very limited experimental or theroetical work available on the effect of the Rashba interaction on the g-factor of quantum confined holes. In this work, we invesitgate this using a two- dimensional hole system confined to a 15nm quantum well in a (100) GaAs heterostructure. The holes are further confined to a one dimensional (1D) channel using surface gates, and overall top and back gates allow us to control the degree of structural inversion asymmetry and hence alter the strength of the Rashba interaction. The use of a 1D channel allows a direct spectroscopic measurement of the Zeeman spin splitting as a function of magnetic field, which is not possible in a 2D system [4, 5]. Our measurements show that the electric field across the quantum well can be used to tune the g-factor. Perhaps surprisingly, we find that increasing the Rashba strength suppresses the measured g-factors. Our results demonstrate modification of the g-factor via the spin-orbit interaction, which could be of value in spintronics applications. [1] S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990). [2] R. Winkler, Spin–Orbit Coupling Effects in Two-Dimensional Electron and Hole Systems (Berlin: Springer, 2003). [3] S.J. Papdakis et al., Science. 283, 2056 (1999). [4] J. C. H. Chen et al., New J. Phys. 12, 033043 (2010). [5] A. Srinivasan et al., Nano Lett. 13, 148 (2013). 112 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Identifying further inelastic neutron crystal field transitions in ErNiAl4 G.A. Stewarta, W.D. Hutchisona, Z. Yamanib, J.M. Cadogana and D.H. Ryanc a School of Physical, Environmental and Mathematical Sciences, UNSW Canberra, Australian Defence Force Academy, PO Box 7916, Canberra BC 2610, Australia. b Canadian Neutron Beam Centre, National Research Council, Chalk River, Ontario, ON K0J 1J0, Canada. c Physics Department, McGill University, Montreal, Quebec, H3A 2T8, Canada. The orthorhombic, intermetallic series RNiAl4 (R = rare earth) exhibits interesting magnetic behaviour [1], including the potential for low temperature, inverse, magnetic cooling [2]. Given that the RNiAl4 magnetism is associated solely with the R sub-lattice and is influenced strongly by the local crystal field (CF) interaction at the R-site, it is important that the CF interaction be characterised. However, the R site’s local, orthorhombic (C2v) symmetry requires nine CF parameters to be determined. Early CF characterization attempts reported in the literature were based on the observed bulk, single-crystal, magnetic anisotropy but ignored the important rank 6 terms [3, 4].Our first inelastic neutron scattering (INS) measurements were performed on Er3+ (J = 15/2) in ErNiAl4 at the Helmholtz Zentrum Berlin’s NEAT time- of-flight instrument. Despite the limited incident neutron energy range, well-defined transitions were observed for the first three (3, 7.4 and 11.4 meV) of the 7 excited Kramers doublets. A semi-empirical approach was applied in a first effort to interpret these data in terms of a full CF Hamiltonian [5]. We report here on our more recent, on-going, INS measurements that exploit the thermal energies and polarisation neutron capability of the Triple Axis Spectrometer (C5) facility at the Canadian Neutron Beam Centre in Chalk River. In addition to the low energy transitions observed at HZB there already appear to be further peaks at 15.5, 21 and 42 meV. [1] W.D. Hutchison, D.J. Goossens, K. Nishimura, K. Mori, Y. Isikawa and A.J. Studer, J. Magn. Magn. Mater. 301, 352 (2006). [2] L. Li, K. Nishimura and W.D. Hutchison, Solid State Commun. 149, 932 (2009). [3] T. Mizushima et al., J. Phys. Soc. Japan 68, 637 (1999). [4] T. Mizushima et al., J. Phys. Soc. Japan 65, 146 (1996). [5] B. Saensunon, G.A. Stewart, P.C.M. Gubbens, W.D. Hutchison and A. Buchsteiner, J. Phys.: Condens. Matter 21, 124215 (2009); Corrigendum J. Phys.: Cond. Matter 22, 029801 (2010). 113 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Thin-Film Thermopower Measurement System Open for Business J.G. Storeya and N. Suresha,b a Superconductivity & Energy Group, Callaghan Innovation, Lower Hutt, New Zealand. b MacDiarmid Institute, Victoria University of Wellington, New Zealand. Thermopower is a measure of the magnitude of the voltage generated across a material in response to an applied temperature gradient. Besides their obvious use in determining the suitability of a new material for energy-harvesting applications, thermoelectric power measurements provide a wealth of information on the nature and behaviour of the charge carriers in materials [1]. We have constructed a system for measuring the thermopower of thin-film samples at temperatures from 7 to 300 K. The system is based around a closed-cycle cryogen-free vacuum cryostat and is controlled by a Java-based software package written in-house. The presentation will cover a description of the system, including example data obtained from second-generation high-temperature superconductor wires, as well as a discussion of the merits of using Java as an alternative to LabVIEW. New collaborations are welcome. [1] J.G. Storey, J.L. Tallon and G.V.M. Williams, Europhysics Letters 102, 37006 (2013). 114 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Phase transition enhanced thermoelectric performance in Cu2Se H. Liua,b, X. Shia, W. Zhanga, L. Chena and S. Danilkinc aShanghai Institute of Ceramics,Chinese Academy of Sciences,Shanghai 200050, China. bUniversity of Chinese Academy of Sciences, Beijing 100049, China. cThe Bragg Institute, Australian Nuclear Science and Technology Organisation, NSW 2322, Australia. Worldwide efforts to searching for good thermoelectric materials are frequently focusing on normal phases in crystalline semiconductors. The material’s thermoelectric performance is described the parameter of figure of merit, zT, which is around unity around room temperature and above 1.5 at high temperatures. In the Cu2Se with anti-fluorite structure above 400K, Se atoms form a rigid face-centred cubic lattice, while the copper ions are highly disordered or moving around the tetrahedral voids with liquid-like mobility, resulting in an extraordinarily low lattice thermal conductivity, which enables zT up to 1.5 at 1,000K [1]. Here, we report significantly enhanced thermoelectric performance during the phase transitions in Cu2Se and iodine doped Cu2Se. It is showed that the critical electron and phonon scattering greatly improve the thermopower and strongly reduce the thermal coductivity, leading to the improvement in the figure of merit more than 3-7 times compared to the normal phases, and achieving zT value of 2.3 at 400K [2]. This mechanism pave a new way to increase the figure of merit of thermoelectric materials, and expend the utility of thermoelectrics in electronic cooling industry. [1] H. Liu, et al. Nature Mater. 11, 422 (2012). [2] H. Liu, et al. Adv. Mater. (Published online, DOI: 10.1002/adma.201302660, 2013). 115 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Characterisation of self-supporting submicron-thick graphitic carbon foils with reflection spectroscopy H. Timmersa,b,c, C. Jansingb, M. Teschb, M. Gilbertb, A.G. Muirheadc, A. Gauppd,b and H.-Ch. Mertinsb a School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra, ACT 2600, Australia. b University of Applied Sciences, Münster, Fachbereich Physikalische Technik, Stegerwaldstraße 39, D-48565 Steinfurt, Germany. c Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200, Australia. d HZB, Albert-Einstein-Straße 15, D-12489 Berlin, Germany. Some electrostatic ion accelerators, radioactive ion beam facilities, proton synchrotrons and accelerator mass spectrometers rely on submicron-thin, self-supporting graphitic carbon foils that change the charge state of swift heavy ions. This is achieved by 'stripping' electrons off the ion by transmitting it through the foil [1]. In order to be effective, these ‘stripper’ foils may need to be as thin as 20 nm to allow for optimum ion beam focusing. If such foils were single-crystalline graphite, a 20 nm thickness would correspond to about 300 atomic layers. The fundamental challenge in making carbon stripper foils is to achieve stability against ion irradiation at minimum foil thickness. Under heavy ion beam irradiation the foils tend to thicken in the beam spot, experience mechanical tension and can suddenly disintegrate. Such failure interrupts ion beam operation and is not desirable. Recent developments of new types of deposition technologies have produced new types of foils. Some new types of foils perform significantly better under ion bombardment compared to others [2]. These differences may be due to the foil microstructures, which have been suggested to be polycrystalline graphite or to contain single-walled carbon nanotubes. In this work reflection spectroscopy with polarised light in the visible and soft x-ray range [3] is applied to characterise different types of self-supporting, submicron-thick graphitic carbon foils. Anticipated results may identify electronic and corresponding structural differences of the various types of foils that are employed for electron stripping and inform studies on other types of graphitic carbon. Preliminary results will be presented and discussed. 116 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 [1] G. Dollinger and P. Maier-Komor, Nucl. Instr. Meth. in Phys. Res. A 257, 64 (1987). [2] A.G. Muirhead and J.K. Heighway, Nucl. Instr. Meth. in Phys. Res. A 655, 61 (2011). [3] H.-Ch. Mertins et al., Phys. Rev. B 70, 235106 (2004). 117 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 X-ray Dose Dependence and Spectral Hole-Burning Properties of Ball Milled Nanocrystalline Ba0.5Sr0.5FCl0.5Br 3+0.5:Sm X.Wanga and H. Riesena a School of Physical, Environmental and Mathematical Sciences, University of New South Wales, Canberra, ACT 2600, Australia. Nanocrystalline Ba 3+0.5Sr0.5FCl0.5Br0.5 doped with Sm ions was prepared by a facile ball milling mehod at room temperature. Upon X-ray irradiation the Sm3+ is converted to Sm2+ [1- 3]. The integrated photoluminescence intensities of the characteristic Sm3+ transition at around 594 nm and Sm2+ transition at around 687 nm were measured with excitation wavelengths of 401 nm and 415 nm, respectively. The sample was irradiated for a range of different times in a powder X-ray diffractometer and the X-ray dose dependence of both Sm3+ and Sm2+ transition was measured. Spectral hole-burning properties of the resulting Sm2+ were investigated in the 7F 50- D0 transition. The mechanochemical process facilitates the synthesis of a proper solid solution and hence the inhomogeneous width of the Sm2+ transition is significntly increased. Ball-milled samples may have some potential in frequency domain optical data storage. [1] H. Riesen and W.A. Kaczmarek, Inorg. Chem. 46, 7235 (2007). [2] H. Riesen, W.A. Kaczmarek, Radiation storage phosphor & application, International PCT Application, WO 2006063409-A1, (2008). [3] Z. Liu, M.A. Stevens-Kalceff and H. Riesen, J. Phys. Chem. C 116, 8322 (2012). 118 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Characterising Graphene Nanoribbons using Raman Microscopy M.R. Waterlanda, H. Dykstraa and A.J. Waya a Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand. Berry et al. recently reported a novel method for the production of graphene nanoribbons [1]. In this method graphite is mechanically fractured (using a diamond-knife equipped microtome) into nanoribbons with nanometre widths and the graphite ribbons are exfoliated with surfactants. This method produces large quantities of high purity graphene nanoribbons (i.e. no chemical side-products). Edge structure (i.e. zig zag vs armchair) of graphene nanoribbons largely controls their electronic properties but the ability to control the edge structure during mechanical fracturing is an unknown parameter. Polarised Raman spectroscopy can characterise graphene edge structure and provides a valuable tool for investigating the edge structure of graphene nanoribbons. We are applying low-frequency polarised Raman microscopy to the analysis of graphene nanoribbons, produced using the Berry method, in this work. We present preliminary results on graphite and graphene nanoribbons. Computational studies are also being used to establish correlations between spectral features and graphene nanoribbon edge structure. We will also present some preliminary computational studies that examine the changes in vibrational mode frequencies and intensities between models for zig zag edges and arm chair edges. [1] N. Mohanty, D. Moore, Z. Xu, T.S. Sreeprasad, A. Nagaraja, A.A. Rodriguez and V. Berry, Nature Comms. 3, 844 (2012). 119 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Structural Investigation of Tungsten Bronze Type Relaxor Ferroelectrics T.A. Whittlea and S. Schmida a School of Chemistry, The University of Sydney, NSW 2006, Australia. Tungsten bronze type compounds have been shown to display a variety of industrially relevant properties including optical and electronic properties [1,2]. Primary among these properties is ferroelectricity [3,4]. Ferroelectric materials are ubiquitous in technological applications, from everyday consumer electronics to sophisticated technical instruments. Traditional ferroelectric materials are limited by the temperature range at which they can operate effectively. In contrast, relaxor ferroelectric materials show comparable properties over a much larger temperature range. Additionally, relaxor ferroelectric properties can be tuned by the frequency of an applied electric field, this allows for greater material selectivity for a desired application. There is a fundamental relationship between the structure of these compounds and the properties they possess [5]. As such a comprehensive analysis of the crystal structure of relaxor ferroelectric materials is essential to explaining the observed properties and ultimately predicting the relationship between chemistry and properties. The focus of this work is the complementary use of synchrotron X-ray and neutron diffraction for the structural analysis of tungsten bronze type relaxor ferroelectric materials. Of particular interest is the location of morphotropic phase boundaries (MPBs) such as that observed for PZT. MPBs are regions of dramatically enhanced properties due to a mixing of ferroelectric states [6,7]. In this presentation relaxor ferroelectric tungsten bronze type materials in the BaxSr3-xTi1-yZryNb4O15 quaternary phase system will be discussed. The structures of the four end members of this system have been previously reported. However, no investigations utilising synchrotron X-ray diffraction have been performed and little utilising neutrons. Sr3ZrNb4O15 is only mentioned once in the literature [8], contrary to Sr3TiNb4O15 which has had three alternate structural models reported [9-11]. The majority of the phase space of this system remains explored and the location of phase transitions is unreported in the literature. Structural models resulting from Rietveld refinements [12] for members of this quaternary system will be presented, shedding light on new lead free relaxor ferroelectric materials. 120 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 [1] L. Z. Xiao, K. Li, R. M. Asif,Q. L. Xiao and M. C. Xiang, J. Appl. Phys. 114, 124102/1 (2013). [2] B. N. Parida, R. D. Piyush, R. Padhee and R. N. P. Choudhary, J. Phys. Chem. Solids 73, 713 (2012). [3] D.-W. Fu, H.-L. Cai, Y. Liu, Q. Ye, W. Zhang, Y. Zhang, X.-Y. Chen, G. Giovannetti, M. Capone, J. Li and R.-G. Xiong, Science 339, 425 (2013). [4] J. Kreisel, M. Alexe and P. A. Thomas, Nat. Mater. 11, 260 (2012). [5] P. S. Halasyamani and K. R. Poeppelmeier, Chem. Mater. 10, 2753 (1998). [6] M. Ahart, M. Somayazulu, R. E. Cohen, P. Ganesh, P. Dera, H.-K. Mao, R. J. Hemley, Y. Ren, P. Liermann and Z. Wu, Nature 451, 545 (2008). [7] D. Pandey, A. K. Singh and S. Baik, Acta Crystallogr. A 64, 192 (2008). [8] V. G. Kryshtop, R. U. Devlikanova and E. G. Fesenko, Inorg. Mater. 15, 1777 (1979). [9] F. W. Ainger, W. P. Brickley and G. V. Smith, Proc. Brit. Ceram. Soc. 18, 221 (1970). [10] R. R. Neurgaonkar, J. G. Nelson and J. R. Oliver, Mater. Res. Bull. 27, 677 (1992). [11] E. O. Chi, A. Gandini, K. M. Ok, L. Zhang and P. S. Halasyamani, Chem. Mater. 16, 3616 (2004). [12] H. Rietveld, J. Appl. Crystallogr. 2, 65 (1969). 121 Proceedings – 38th Annual Condensed Matter and Materials Meeting – Waiheke Island, Auckland, NZ, 2014 Neutron powder diffraction and Synchrotron PD and XAS studies of Cu5-xMnxSbO6 and Cu5Sb1-xMoxO6 D.J. Wilsona and T. Söhnela a School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. Cu5SbO6 is a mixed valence copper compound that crystallises in a modified Delafossite structure type (CuFeO2), with two distinct modifications [1-3]. The high temperature modification is of particular interest due to ferromagnetic-antiferromagnetic short range ordering of Cu2+ pairs in the structure. Compounds like CuFeO2 crystallising in the Delafossite structure are one of the few groups of compounds showing the rare property of multiferroic behaviour. In order to influence the magnetic properties of Cu5SbO6, magnetically active transition metals were doped into the structure. Manganese and molybdenum were doped into the structure separately and in conjunction. Synchrotron and neutron powder diffraction techniques were conducted in order to determine the incorporation of the doping metal. In addition to powder diffraction techniques, X- ray absorption spectroscopy was used to probe the oxidation state/s of the incorporated metal [4]. Magnetic susceptibility measurements of the doped Cu5SbO6 were performed in order to compare with Cu5SbO6. Figure 1. Shifts of the reflection peaks in the NPD patterns of the high temperature modification of Cu5-xMnxSbO6. [1] E. Rey, BScHons Thesis, The University of Auckland (2010). [2] E. Rey, P. Z. Si and T. Söhnel, Proceedings of the 35th Annual Condensed Matter and Materials Meeting, WaggaWagga, Australia, Canberra, Australian Institute of Physics, 22-25. ISBN: 978-0-646-55969-8 (2011). arXiv:1107.3617v1 [cond-mat.mtrl-sci]. [3] E. Climent-Pascual, P. Norby, N. H. Anderson, P. W. Stephens, H. W. Zandbergen, J. Larsen and R. J. Cava, Inorg. Chem, 51 557 (2012). [4] D.J. Wilson, BScHons Thesis, The University of Auckland (2013). 122 Proceedings+–+38th+Annual+Condensed+Matter+and+Materials+Meeting+–+Waiheke+Island,+Auckland,+NZ,+2014! A novel approach to synthesis of highly reduced graphene oxide G. Xua, C. Lianga, J. Zhanga, H. Kanga and J. Jina a School of Chemical Science, The University of Auckland, New Zealand. Since graphene was firstly isolated by Geim’s group from UK, graphene has expeditiously become a new super star in the view of nanotechnology and material science [1]. Chemically reduced graphene oxide has been viewed as one of the novel methods for preparation of graphenes in large yields. In order to synthesis reduced graphene oxide, various reducing agents have been proposed to reduce graphene oxide, including hydrazine, ascorbic acid, proteins, carbon monoxide, NaOH, ethanol, NaNH3, aluminium powder, hydriodic acid, glucose et. Metal hydrides including a group of powerful reducing reagents have frequently been used in organic synthesis. Until now, sodium borohydride (NaBH4) and lithium aluminium hydride (LAH) [2] have already been applied in GO reduction successfully. Super Hydride is an extraordinarily super-strong nucleophilic reductant available for unselectively reducing carboxylic acid, carbonyl, ester and epoxy groups to hydroxyl groups, even a lot more powerful and cleaner than NaBH4 and lithium aluminium hydride. Here, for the first time, we propose a method using super hydride as a new reducing reagent on graphene oxide, and with the comparison of the reduction capacity towards that of LAH and NaBH4, which have been commonly employed in similar application. We have used a series of analytical techniques including UV-Vis, FTIR, Raman spectroscopy, elemental analysis, XRD, XPS, TGA and AFM characterization to confirm that super hydride is far more powerful and efficient in converting oxygen functional carbon moieties as the reduction towards graphene oxides. Furthermore, our research demonstrates a new advantageous solution processing method that forwards one step towards applicability of the “tool box” in organic chemistry reducing reagents for production of reduced graphene oxides in high quality. [1] A.K. Geim and K.S. Novoselov, Nat. Mater. 6, 183 (2007). [2] A. Ambrosi et al., Chem. Mater. 24, 2012 2292 (2012). 123