Electrical transport and magnetoresistance in La_(0.67)Ca_(0.33)MnO_3/BaTiO_3 composites

摘要

The results of the structure, electrical transport and magnetoresistance of a ferromagnet-ferroelectric-type La_(0.67)Ca_(0.33)MnO_3 (LCMO)/BaTiO_3 composites fabricated by the sol-gel method are presented. The structure and morphology characterization indicates no apparent variations in morphology and particle size in spite of the existence of BaTiO_3. The insulator-metal transition temperature (T_(IM)) is shifted to a higher temperature and resistivity decreases with the increase of low content BaTiO_3. Magnetoresistance (MR) of the composites is enhanced over the whole temperature range as a result of the introduction of BaTiO_3. By calculating in terms of a ferromagnetic grain coupling model, we attribute these transport properties to the enhancement of the ferromagnetic coupling between the neighboring grains, which could be explained by the increase of the carrier concentration at the grain boundary due to the introduction of BaTiO_3 and the associated magnetoelectric coupling effect.