Electrical and Magnetic Properties and Colossal Magnetoresistance Effect of La_1-xBi_xMnO₃

Abstract

Perovskite-type La 1- x Bi x MnO 3 (LBMO) crystals, which were prepared by doping a Bi atom for a La atom in LaMnO 3 , were shown to exhibit the colossal magnetoresistance (CMR) effect. Samples were produced by sintering in an air atmosphere that depended on the Bi composition ratio x . X-ray diffraction measurements showed that the LBMO crystal structure can be orthorhombic (or rhombohedral) with γ (= c / a )=1.02 for 0.0< x <0.3, cubic with γ=1.005 for 0.3< x <0.5 or monoclinic with γ=1.014 for 0.5< x . The CMR effect of LBMO for x =0.2 was approximately 400% at 88 K. In addition, the magnetoresistance of LBMO was found to be proportional to the square of magnetization. On the basis of these results, the CMR occurrence mechanics of LBMO were shown to significantly contribute to a Mn 3+ –Mn 4+ double exchange interaction, which is closely associated with the cooperative phenomenon in the Jahn–Teller effect.