Abstract
Composites of (1 − x)La0.7Ca0.3MnO3/xLa0.7Sr0.2Ca0.1MnO3 were prepared via the sol–gel method combined with the energy milling method. The electrical transport and low-field magnetoresistance properties of the composites were systematically studied. As the La0.7Sr0.2Ca0.1MnO3 level increased, the metal-insulator transition temperature of the composites shifted to a higher temperature. The transport mechanisms in the insulating region of the composites were comprehensively analyzed via small polaron hopping (SPH) and variable range hopping (VRH) models. The combination of electron–electron interaction and spin wave scattering was considered to estimate the conduction mechanism in the metallic region of the composites. Both intrinsic magnetoresistance and extrinsic low-field magnetoresistance were enhanced from 30 K to the Curie temperature for the system. The results were explained on the basis of the competition between spin-dependent scattering and spin-polarized tunneling at La0.7Ca0.3MnO3 grain boundaries induced by interactions between La0.7Ca0.3MnO3 and La0.7Sr0.2Ca0.1MnO3 manganites.
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