Theoretical model of the mechanism study on the positive magnetoresistance in the heterostructure composed of two oxides

A positive colossal magnetoresistance (CMR) has been discovered at low applied magnetic field and in the temperature range from 130 to 290 K in the epitaxial p-n heterostructure fabricated with Sr-doped LaMnO3 and Nb-doped SrTiO3 by laser molecular-beam epitaxy. The mechanism causing the unusual positive CMR is proposed as an interface effect, i.e., creation of the region near the interface with electron filling in the t2g spin-down band in La0.9Sr0.1MnO3 plays a crucial role in spin-dependent carrier transport of the system. Self-consistent calculation has been carried out to obtain the band diagram around the interface of the heterostructure. Other puzzling CMR features, which exhibit values of positive CMR first increase and then decrease with increase of negative bias voltage and temperature, are well explained by the present scenario.