Electrical and magnetic behavior of La0.7Ca0.3MnO3/La0.7Sr0.2Ca0.1MnO3 composites

The electrical transport properties and the magnetoresistance of La0.7Ca0.3MnO3/La0.7Sr0.2Ca0.1MnO3 composites are investigated as a function of sintering temperature. On the basis of an analysis by X-ray powder diffraction and scanning electron microscopy we suggest that raising the sintering temperature enhanced the interfacial reaction and creates interfacial phases at the boundaries of the La0.7Ca0.3MnO3 and La0.7Sr0.2Ca0.1MnO3. Results also show that in 3 kOe, and at the Curie temperature, the magnetoresistance value of 14% was observed for the composite sintered at 1300 °C. Based on the phenomenological equation for conductivity under a percolation approach, which depends on the phase segregation of ferromagnetic metallic clusters and paramagnetic insulating regions, we fitted the experimental resistivity—temperature data from 50–300 K and find that the activation barrier decreases as temperature is increased.