Large enhancement in room-temperature magnetoresistance and dramatic decrease in resistivity in La0.7Ca0.3MnO3-Ag composites

A ferromagnet-metal-type composite, La0.7Ca0.3MnO3 (LCMO)-Ag, was fabricated by a two-step chemical route which can avoid the doping of Ag into the lattice of LCMO. The grain size of Ag can be reduced by increasing calcination temperature, which favors the penetration of Ag into LCMO matrices. A large enhancement in magnetoresistance (MR) near room temperature and a dramatic decrease in resistivity are observed for the samples calcined at above the melting temperature of Ag. We suggest that the shift of metal-insulator transition up to Curie temperature in melted-Ag-added LCMO and magnetic inhomogeneity are responsible for the enhanced MR. (C) 2002 American Institute of Physics.