Giant magnetoresistance of bulk polycrystalline La 0.833Na 0.167MnO 3 with Ag 2O addition

Abstract

A series of bulk polycrystalline samples of La 0.833Na 0.167MnO 3 with Ag 2O addition were prepared by conventional solid-state reaction processing in air. The mol proportion between La 0.833Na 0.167MnO 3 and Ag 2O is 1: x ( x=0, 0.04, 0.08, 0.125, 0.25, and 0.50). X-ray diffraction patterns show that the sample for x=0, i.e., pure La 0.833Na 0.167MnO 3, contains a single perovskite phase and that the samples for x>0 are composed of two phases (a magnetic perovskite phase and a nonmagnetic Ag-rich phase). It is found that, in this series of polycrystalline samples, a maximum magnetoresistance occurs for x=0.25, i.e., for a composite of the two phases. The corresponding magnetoresistance ratio is about 27% at room temperature. The enhancement of the magnetoresistance effect in such an inhomogeneous granular system can be attributed to the spin dependent scattering of electrons at the interface of the two phases.