X-ray Photoemission Spectroscopy and Magnetic Properties of Bi Doped LaMnO₃

Abstract

Perovskite-type La_1−xBi_xMnO₃ (LBMO), which are prepared by doping the Bismuth (Bi) ion in LaMnO₃, were shown to exhibit the colossal magnetoresistance (CMR) effect. Samples were produced using a sintering process in an air atmosphere as a function of the Bi composition ratio x. X-ray diffraction measurements showed that the LBMO crystal structure varied among an orthorhombic (or rhombohedral) type with 0.0<x<0.3, to a cubic type with 0.3<x<0.5, and to a monoclinic type with for 0.5<x. The CMR effect of LBMO for x=0.2 was approximately 400% at 140 K. In addition, the magnetoresistance of the LBMO system was found to be proportional to the square of the magnetization. It was interpreted that, from XPS analysis, the valence states of manganese and bismuth atoms in LBMO contain [Mn³⁺,Mn⁴⁺] and [Bi³⁺, Bi²⁺ (or pseudo-divalent Bismuth)] ionic states.