Browsing by Author "Rey, E"

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    Cu5SbO6 – synchrotron, neutron diffraction studies and magnetic properties
    (Australian Institute of Physics, 2011-02-04) Söhnel, T; Rey, E; Ling, CD; Avdeev, M; Johannessen, B; Wallwork, KS; Kremer, RK; Whangbo, MH
    One very interesting compound in the system Cu/Sb/O is the mixed-valent Cu5SbO6 = (Cu1+(Cu2+ 2/3Sb5+ 1/3)O2) which is crystallising in the high temperature modification as a modified Delafossite structure type. Compounds like Delafossite, CuFeO2, is one of the few groups of compounds showing the rare property of multiferroic behaviour. In Cu5SbO6 the magnetically active brucite-like CuO2 layer is diluted in an ordered fashion with nonmagnetic Sb5+. Cu5SbO6 also shows a phase transition, which exhibits a rather complicated behaviour. It depends on the temperature and the reaction conditions (reactants for preparation, pressure, open or closed system). High resolution Synchrotron and neutron powder diffraction measurements could clearly distinguish between the high temperature and the low temperature modification and reveal an ordering (HT-modification) / disordering (LT-modification) effect of the Sb5+ and Cu2+ ions in the brucite-like layers. The LT-modification can also be assigned to what had wrongly been described in the literature as Cu4.5SbO5. XANES Cu-K edge measurements and NPD measurements should clarify a potential oxidation of the Cu1+ to Cu2+ and a connected additional inclusion of oxygen in the structure. According to magnetic measurements and DFT calculations the magnetic structure in Cu5SbO6 can be described with a short range ferromagnetic-antiferromagnetic interaction model of the (Cu2+) pairs in the (Cu2+ 2/3Sb5+ 1/3)O2 layers with a super-exchange via the nonmagnetic Sb5+ atoms. The systematic replacement of the non-magnetic Sb5+ with magnetically active M5+ ions should change the magnetic properties dramatically and could lead to an long range ordering in the system. First results of Mn and Mo doping will also be presented.