Structure, Magnetoresistance and Electrical Properties of La_0.8Sr_xCa_0.2-xMnO₃ Compounds

Abstract

The La0.8SrxCa0.2-xMnO3 (x=0, 0.05 and 0.15) compounds were synthesized by combining sol-gel method and high temperature sintering. The effects of Sr doping content on the microstructure, metal-insulator transition and magnetoresistance (MR) of the La0.8SrxCa0.2-xMnO3 were investigated. The results show that the La0.8SrxCa0.2-xMnO3 exhibit single perovskite phase and the change of Sr doping content can result in phase structure transition. The La0.8Sr0.15Ca0.05MnO3 is rhombohedra structure and the La0.8SrxCa0.2-xMnO3 shows distorted cubic structure when x is no more than 0.05. Increasing Sr doping content causes the degeneration of microstructure homogeneity and density and the decrease of average grain size of the La0.8SrxCa0.2-xMnO3, which can be attributed to the weakening of atomic diffusion during the sintering process. The metal-insulator transition temperature (TMI) of the compounds increases with the decrease of Sr doping content due to the improvement of microstructure. The La0.8Sr0.15Ca0.05MnO3 has the highest MR peak value, which is about 95%. The La0.8Ca0.2MnO3 has the highest room temperature MR, which is about 28%. Moreover, the magnetoresistance of the La0.8Ca0.2MnO3 is very stable between 125~300K.