Browsing by Author "Wood, PT"
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- ItemLinear spin wave theory calculations for a powder sample: excitations in the distorted kagomé lattice Mn3(1,2,4-(O2C)3C6H3)2(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Mole, RA; Yu, DH; Rule, KC; Stride, JA; Wood, PTThe measurement of spin waves from magnetic crystals has been a longstanding success story of inelastic neutron scattering. The development of linear spin wave theory [1,2] predates the first neutron scattering measurements and is well developed and suited to the determination of spin waves from magnetic ions with large spins. However to date there has been limited success in applying spin wave theory to lower symmetry crystal structures; such structures are commonly occurring in molecule based magnetic systems whereby the packing of the organic ligands often favours lower symmetry space groups. Further the determination of powder averaged spectra has previously been difficult. Recently spin wave calculation software has become readily available; one such package SpinW [3] readily address the problems of low symmetry and powder averaging. A rotation matrix strategy is implemented so that it is suitable for incommensurate structures. In this contribution we will demonstrate the power of these techniques using data obtained on the cold neutron time-of-flight spectrometer PELICAN for the distorted kagomé lattice Mn3(1,2,4-(O2C)3C6H3)2. [4] Our interest in the distorted kagomé lattice compound stems from the observation of a combination of magnetic ordering and glassy behaviour in a distorted frustrated network. Our inelastic neutron scattering and spin wave theory results allow us to characterise all of the exchange interactions in the distorted lattice and relate these to the degree of frustration in the lattice.
- ItemMuon spin relaxation study of manganese hydroxy squarate(Elsevier, 2008-09-01) Mole, RA; Cottrell, SP; Stride, JA; Wood, PTMuon spin relaxation has been used to study the magnetic phase transition and spin dynamics above T-c in Mn-2(OH)(2)(C4O4). These studies confirm previous findings of a transition to long range order, providing a more accurate determination of T-c = 12.5 K as well as indicating short range order at temperatures above the phase transition. The muon measurements are insensitive to the presence of a small quantity of manganese carbonate in the sample that tend to dominate bulk magnetic susceptibility experiments. © 2008, Elsevier Ltd.
- ItemNon-classical behaviour in an S=5/2 chain with next nearest neighbour interactions observed from the inelastic neutron scattering of Mn-2(OD)(2)(C4O4)(Institute of Physics, 2009-02-18) Mole, RA; Stride, JA; Unruh, T; Wood, PTLow-dimensional and frustrated magnetic systems often show interesting quantum phenomena. The use of large moments such as S = 5/2 within such materials is uncommon, partly due to the evidence that the large manifold of states associated with these centres results in pseudo-classical behaviour. Here we report on the inelastic neutron scattering of Mn-2(OD)(2)(C4O4), a well-isolated chain with next nearest neighbour interactions. We observe a magnetic excitation spectrum below 30 K whose characteristics resemble those of quantum spin singlets. Inelastic neutron scattering from a powdered sample is shown to yield a great deal of information about the nature of these effects. © 2009, Institute of Physics
- ItemSwitchable magnetism: neutron diffraction studies of the desolvated coordination polymer Co-3(OH)(2)(C4O4)(2)(American Chemical Society, 2013-11-13) Mole, RA; Nadeem, MA; Stride, JA; Peterson, VK; Wood, PTWe report the magnetic structure of the two magnetically ordered phases of Co3(OH)2(C4O4)2, a coordination polymer that consists of a triangular framework decorated with anisotropic Co(II) ions. Neutron diffraction experiments allow us to confirm that the magnetic behavior changes upon dehydration and reveal the complex phase behavior of this system, relative to the hydrated compound Co3(OH)2(C4O4)2·3H2O. One phase is shown to display spin idle behavior, where only a fraction of the moments order at intermediate temperatures, while at the lowest temperatures the system orders fully, in this case with a net magnetic moment. This novel magnetic behavior is discussed within the framework of a simple Hamiltonian and representational analysis and rationalizes this multiphase behavior by considering the combination of frustration and anisotropy. The change in behavior on dehydration is also rationalized with respect to the changes in the single-ion anisotropy of the cobalt. © 2013, American Chemical Society.
- ItemTwo stage magnetic ordering and spin idle behavior of the coordination polymer Co-3(OH)(2)(C4O4)(2)center dot 3H(2)O determined using neutron diffraction(American Chemical Society, 2011-03-01) Mole, RA; Stride, JA; Henry, PF; Hoelzel, M; Senyshyn, A; Alberola, A; Garcia, CJG; Raithby, PR; Wood, PTWe report the magnetic structure of two of the magnetically ordered phases of Co-3(OH)(2)(C4O4)2 center dot 3H(2)O, a coordination polymer that consists of a triangular framework decorated with anisotropic Co(II) ions. The combination of neutron diffraction experiments and magnetic susceptibility data allows us to identify one phase as displaying spin idle behavior, where only a fraction of the moments order at intermediate temperatures, while at the lowest temperatures the system orders fully. This novel magnetic behavior is discussed within the framework of a simple Hamiltonian and representational analysis and rationalizes this multiphase behavior by considering the combination of frustration and anisotropy. © 2011, American Chemical Society