Key Words:colossal magnetoresistance; granular manganites; two-phase composites; spin-dependent scattering

Abstract:The magnetic and electrical properties of the La0.67Ca0.25Sr0.08MnO3/xAg composite system are systematically investigated as a function of Ag-added content. With increasing the Ag dopant amount, the magnetization decreases a little while Curie temperature (T-C) is almost independent of Ag content around 312 K. The resistivity reduces rapidly with Ag addition (x < 0.25) due to the decomposed metal Ag, and then it increases slightly which is probably induced by the less Ag content related to the volatilization of Ag during calcinations. At low temperature, the rho - T curves fit well by the expression of rho = rho(0) + rho T-2(2) + rho T-4.5(4.5) while all data for the above T-C can be fitted by using the adiabatic small-polaron-hopping model rho = rho T-0 exp(E/k(B)T). The enhancement of MR effect (41%) at room temperature is mainly related to the coexistence of intrinsic MR properties and the spin dependent scattering of conduction electrons at the interfaces. These results indicate that combining the doping effect with the composite method is an effective selection in enhancement of MR at room temperature, which is very meaningful for the application research.

Volume:704-705

Translation or Not:no