Successive Phase Transitions of LuBaCo_4O_7 with Kagome and Triangular Lattices(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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Magnetic, thermal and neutron diffraction measurements have been carried out on single-crystal samples of LuBaCo_4O_7 with kagome and triangular lattices of Co spins. Anomalies of the magnetic susceptibility have been found at temperatures T_<a1>〜70K and T_<a2>〜50K. We have also found a second-order structural transition at T_<c1>〜165K and a first-order structural transition at T_<c2>〜105K (T_<c2>'〜80K) with increasing (decreasing) temperature. Two groups of magnetic diffuse scattering, corresponding to the short-range correlations with the commensurate (C) and incommensurate (IC) periods, have been found to exist below the structural transition temperature T_<c2> (T_<c2>'). The reflections with the C and IC periods originate from the moments on the kagome and triangular lattices, respectively. At 10K, the magnetic correlation length is estimated to be 〜100Å. The structural changes of LuBaCo_4O_7 and YBaCo_4O_7 differ significantly, which seems to induce the differences in their magnetic properties.
社団法人日本物理学会の論文
2007-08-15