Grain boundaries and low-field transport properties in colossal magnetoresistance materials

The grain-boundary structure and the temperature dependence of resistivity were investigated for (1 - x)LCMO + xYSZ, where LCMO and YSZ represent La2/3Ca1/3MnO3 and yttria-stabilized zirconia, respectively. It is shown that the YSZ doped samples for x < 2% show transport and low-field magnetoresistance (LFMR) behaviours different from that for x > 2%. The metal-insulator transition temperature (T-p) decreases for x < 2% but increases for x &GT; 2% as x is increased. LFMR increases with x for x &LT; 2% but decreases for x &GT; 2%. The experimental observations are discussed on the basis of scanning electron microscopy (SEM) analysis, which reveals YSZ appearing at the grain boundaries of LCMO for x &LT; 2%, while presenting itself within the sample in the form of clusters for x &GT; 2%.