Extrinsic properties of colossal magnetoresistive samples

In this work, we report a study on the extrinsic properties of La0.7Ca0.3MnOy samples and their relation with the microstructural configuration. Precursor powders and polycrystalline samples were prepared using three different methods. Comparative results of X-ray diffraction associated with Rietveld refinement, scanning electron microscopy and AC magnetic susceptibility measurements were employed to investigate the influence of grain morphology and the effect of boundaries in the competition between intrinsic and extrinsic properties in these compounds that are known to present the colossal magnetoresistance phenomenon.