Electrical transport of (1−x)La0.7Ca0.3MnO3+xAl2O3 composites

We report the resistivity (ρ)-temperature (T) patterns in (1-x)La0,7Ca0,3MnO3+xAl2O3 composites (0≤x≤0.05) over a temperature regime of 50-300 K. Al2O3 addition has increased the resistivity of these composites. The Curie temperature (TC) is almost independent on the Al2O3 content and is about 250 K for all the samples, while the metal-insulator transition temperature (TMI) decreases with increasing Al2O3 content. Based on the phenomenological equation for conductivity under a percolation approach, which is dependent on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the experimental data (ρ−T) from 50 to 300 K and find that the activation barrier increases as Al2O3 content increases.