Magnetoresistance in manganite/alumina nanocrystalline composites

Magnetotransport properties of manganite/insulator composites are studied in this article. By merging the half metallic character of ${\mathrm{La}}_{\mathrm{2/3}}{\mathrm{Ca}}_{\mathrm{1/3}}{\mathrm{MnO}}_{\mathrm{3}}$ and the mixed composition with alumina grains dispersed in the structure we have been able to increase three times intergranular magnetoresistance around the percolation threshold. The transport properties have been studied employing a theoretical model for ferromagnetic–insulator systems and a two channel equation in order to reproduce the behavior of resistivity in the whole temperature range. The percolation theory is introduced to try to understand and improve the fascinating properties of these mixed systems.