Low-field magnetoresistance of (1 − x)La0.7Ca0.3MnO3 + xAg composites

Low-field magnetoresistance of (1 − x) La0.7Ca0.3MnO3 + xAg (LCMO/Ag) composites have been reported in this paper. The low-field magnetoresistance (LFMR), the conductivity (σ) and the metal–insulator transition temperature (Tp) increases when increasing content of Ag. In order to explore the basic physics behind temperature dependence of MR, we analyzed our data in the light of a phenomenological model, which was based on the spin-polarized transport of conduction electrons at the grain boundaries. We find that the temperature dependence of LFMR is described by an expression as Curie–Weiss law-like behavior, i.e., LFMR(T) = a + b/(c + T). Finally, we have attributed this feature of LFMR to the surface magnetization of our nanosize granular LCMO/Ag samples, the role of which becomes very much dominant for our nanodimensional manganite composites.