Enhanced ferromagnetic transition and magnetoresistance in granular Ag-added La0.7Ca0.3MnO3

Granular Ag-added La0.7Ca0.3MnO3 (LCMO) samples were prepared by a sol-gel chemical route. Significant enhancements in Curie temperature (TC), metal-insulator transition (Tp) and magnetoresistance (MR) effects near room temperature are observed in as-obtained samples. 10 wt% addition of Ag in LCMO causes TC shift from 272 to 290 K, Tp boost up for more than 100 K and resistivity decrease by more than 3 orders of magnitude. X-ray diffraction patterns, thermal analysis and energy dispersive analysis of X-rays evidently show the existence of metal silver in LCMO matrices. High-resolution electron microscopy illustrates a well crystallization for LCMO grains in existence of Ag. It is argued that improved grain boundary effect and better crystallization caused by Ag addition are responsible for the enhancements