Giant magnetoresistance of the La1−xAgxMnO3 polycrystalline inhomogeneous granular system

A series of bulk polycrystalline La1−xAgxMnO3 samples with x ranging nominally from 0 to 0.5 were prepared by conventional solid-state reaction processing in air. X-ray diffraction patterns show that the samples contain a single perovskite phase when x⩽0.25, and are composed of two phases (a magnetic perovskite phase and a nonmagnetic Ag-rich phase) for x>0.25. It is found that, in this series of polycrystalline samples, maximum magnetoresistance occurs for x=0.30, i.e., for a composite of the two phases whose magnetoresistance ratio is about 25.5% 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.