Browsing by Author "Collison, D"

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    Inelastic neutron scattering and EPR studies of cobalt dimers
    (Australian Institute of Physics, 2011-02-03) Mole, RA; Boeer, AB; Simeoni, GG; Collison, D; McInnes, EJL; Timco, GA; Winpenny, REP
    The phenomenon of single molecule magnetism has been known for over fifteen years and the fundamentals of this behaviour are well understood; the observed hysteresis is due to an energy barrier for spin reversal, the magnitude of this energy barrier is given by the magnitude and anisotropy of the molecular spin. Despite intensive research it has not been possible to improve the performance of the best single molecule magnets to obtain operating temperatures above a few Kelvin. Recent work has suggested that the anisotropy parameter might play a more important role than previously thought. As such clusters consisting of octahedral Co(II) are promising candidates due to the large anisotropy associated with the spin orbit coupling of the 4T1g ground term. There are however no clear cut cobalt single molecule magnets and the magnetic properties of coordination clusters consisting of octahedral cobalt (II) ions are often complex. Here I present an inelastic neutron scattering study of two cobalt dimers Co2(D2O)(L)4(HL)2(C5D5N)2 and Co2(D2O)L4(HL)4 where L = (CD3)3Co2H [1]. These dimers share a common core; though display different bulk magnetic properties. The dimer was chosen as it is the simplest possible exchange coupled unit that can be studied. The use of inelastic scattering for this problem is incredibly powerful, both due to the zero field nature of the technique and the flexible selection rules [2]. The INS data is presented together with the results of multiple frequency EPR and bulk magnetic properties. The complimentary nature of these techniques allows both the energy scale and the ground state to be determined.
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    Kinetics vs. thermodynamics: a unique crystal transformation from a uranyl peroxo-nanocluster to a nanoclustered uranyl polyborate
    (Royal Society of Chemistry, 2014-07-30) Zhang, YJ; Bhadbhade, MM; Price, JR; Karatchevtseva, I; Collison, D; Lumpkin, GR
    A novel method to prepare a nano-clustered uranyl polyborate in aqueous solution at room temperature has been developed. The initially formed kinetically favoured sodium uranyl peroxide yellow crystals transform, in the presence of boric acid, to the thermodynamically stable sodium uranyl polyborate in light yellow-green single crystal form. © Royal Society of Chemistry 2016
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    A spectroscopic investigation of magnetic exchange between highly anisotropic spin centers
    (Wiley-Blackwell, 2011-04-18) Boeer, AB; Barra, AL; Chibotaru, LF; Collison, D; McInnes, EJL; Mole, RA; Simeoni, GG; Timco, GA; Ungur, L; Unruh, T; Winpenny, REP
    Structurally similar, magnetically diverse: The exchange and Zeeman parameters of two dimetallic, six-coordinate cobalt(II) compounds—i.e., with orbitally degenerate metal ions—have been determined by a combination of high-resolution EPR and INS spectroscopies, together with ab intio calculations. It is suggested that the correlation between the local crystal field about the CoII centers and the superexchange pathway controls the magnetic interaction. © 2011, Wiley-Blackwell.