Sintering temperature effect on electrical transport and magnetoresistance of nanophasic La_0.7Sr_0.3MnO₃

Abstract

Nanophasic La0.7Sr0.3MnO3 (LSMO) samples were prepared by the sol–gel method. The samples were sintered at different temperatures ranging from 600 to 1000 °C. It is shown that the transport and magnetoresistive properties of LSMO samples strongly depend on the sintering temperature (Ts). A substantial decrease in the insulator–metal transition temperature (TIM) and an enhancement in resistivity are found on lowering the sintering temperature. Furthermore, a reduction in magnetization and a slight decrease in paramagnetic–ferromagnetic (PM–FM) transition temperatures (Tc) have been observed as the sintering temperature decreases. The magnetoresistance (MR) at T<Tc increases on decreasing the sintering temperature as well as increasing the applied magnetic field. The enhancement in MR on decreasing the sintering temperature is explained by enhanced spin-polarized tunnelling by assuming an increase of the grain boundary contribution as the sintering temperature decreases.