Low-temperature magnetoresistance in polycrystalline manganites: Connectivity versus grain size

Abstract

The effects of connectivity between grains on the magnetic and transport properties on La0.7Ca0.3MnO3 polycrystalline pellets and thin films were investigated. A model was developed to reproduce the low-field and high-field magnetoresistance at low temperature. The opening of new conduction channels in parallel due to the ordering of Mn spins blocked at the grain surface was used to model the decrease of the resistance at high fields.