The Sr Compositions Dependence of Magnetoresistance of Perovskite-Type Compounds La_1-xSr_xMnO₃

Abstract

The effect of electrical resistivity and magnetoresistance on the Jahn-Teller distortion of perovskaite type La_1-xSr_xMnO₃ (LSMO) were examined. The samples were the polycrystalline specimens that are well grown the crystal in the <100> axis, and prepared by the sintering process with the synthesis of powder oxides La₂O₃, SrCO₃ and Mn₂O₃, respectively. It was proven by the measurement of XPS in respect of g_e-orbit and t_2g-orbit of the Mn³⁺ on the Jahn-Teller ion of LSMO crystal, and the difference of both energy levels had been 2 eV. The electrical resistivity of the samples becomes a minimum, when Sr composition ratio x are 0.2 and 0.5. This fact means that the hopping of the conduction electron becomes active due to relaxation of the Jahn-Teller distortion and transformation from the insulator phase to metallic phase on account of substituting the Sr ion for the part of the La ion in LaMnO₃. It was proven to become a maximum by linking the magnetoresistance effect with the phenomenon, when electrical resistivity undergoes transition by the effect of Sr composition ratio.