La_<1-X>Bi_XMnO_3系磁性と超巨大磁気抵抗効果

概要

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Perovskite-type La_<1-x>Bi_xMnO_3 (LBMO) crystals, which are prepared by the substitution of Bi atom with La atom from a performed LaMnO3 crystal, have been clarified to have the colossal magnetoresistance (CMR) effect. These samples were produced using a sintering process in an atmosphere as a function of Bi composition ratio x. It was found that the Jahn-Teller distortion exists on LBMO crystal structures of orthorhombic (or rhombohedral ) type with lattice parameter y (=c/a)=1.02 in 0<x<0.3, pseudo cubic type with γ=1.005 in 0.3<x<0.5, and tetragonal type with γ=1.014 in a ratio more than 0.5<x, from X-ray diffraction measurements. The CMR effect of LBMO for x=0.2 was approximately 400% at 88K. On the basis of result, it was defined that the occurrence mechanics of CMR for LBMO significantly contribute Mn^<3+>-Mn^<4+> double exchange interaction which is closely associated with the cooperative phenomena in Jahn-Teller distortion.
東海大学の論文
2004-09-30