Magnetic and Transport Properties of Phyrochlore Molybdates : Condensed Matter: Electronic Properties, etc.

概要

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Magnetic and transport properties of the pyrochlore molybdate R_<2-x>R'_xMo_2O_7 (R, R' = rare earth, Y), which exhibits the metal-insulator (M-I) transition with varying x, have been studied. The transition from an antiferromagnetic spin-glass state to a ferromagnetic one occurs at x far from the M-1 phase boundary, indicating that the intimate correlation of' the magnetic state with the conducting nature is not so obvious. In Nd_2MO_2O_7, the ordering of Mo spins takes place at about 95 K, where the anomalous Hall resistivity appears with decreasing temperature T along with the spontaneous magnetization. With the ordering of Nd moments which becomes significant below ~20 K with decreasing T, the behavior of the anomalous Hall resistivity markedly changes, while the Mo-magnetization is partially cancelled by the Nd magnetization. It is shown that the anomalous Hall resistivity can be described by two components, 4πR_sM_<Mo> and 4πR'_s~M_<Nd>, the contributions from the uniform magnetizations M_<Mo> and M_<Nd> of Mo and Nd moments, respectively. The sign of R'_s is opposite to that of R_s. Brief arguments are given if the unusual behavior of the Hall resistivity is related with the nonzero chirality of the magnetic moment system.
社団法人日本物理学会の論文
2001-01-15