Electrical transport and magnetic properties in La0.67Ca0.33MnO3 and CuFe2O4 composites

The (1 - x) La0.67Ca0.33MnO3/xCuFe(2)O(4) (X = 0, 0.04, 0.07, 0.10 and 0.15) composites have been prepared and investigated systematically for their microstructure, electrical and magnetic properties. The X-ray diffraction and scanning electronic microscopy analysis reveal that both La0.67Ca0.33MnO3 (LCMO) and CuFe2O4 phases are distributed in the composites. Compared with pure LCMO, an obvious enhancement of magnetoresistance is observed over a wide temperature range for the composites. Under 3T field, the magnetoresistance rises from a base value 44.5% for pure LCMO, to a maximum value of 66.7% for x=0.1 composite. Meanwhile, a weak temperature-dependent MR platform is observed in the temperature range from 210K to 240K. The MR enhancement is discussed in terms of spin-polarized intergrain tunneling due to enhanced magnetic disorder and magnetic coupling near boundaries between LCMO and CuFe2O4 grains. (C) 2008 Published by Elsevier B.V.