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 (T-C), metal-insulator transition (T-p) and magnetoresistance (MR) effects near room temperature arc observed in as-obtained samples. 10 wt% addition of Ag in LCMO causes T-C shift from 272 to 290 K T-p 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. (C) 2003 Elsevier Inc. All rights reserved.