Theoretical study on the positive magnetoresistance in perovskite oxide p–n junctions

Taking spin current into account, the dependence of magnetoresistance with negative bias and that with doping concentration with various spin polarization in La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 p – n junction are obtained theoretically. The variation of the magnetoresistance value with the reverse bias is found to be due to the competition between the tunneling rate of electrons in e g 1 ↑ band at the homogeneous region of La0.9Sr0.1MnO3to t 2 g ↓ band and that to e g 2 ↑ band at the interface region of La0.9Sr0.1MnO3. From the comparison of calculated magnetoresistance and the experimental data, a dependence of spin polarization of the system on the applied magnetic field is obtained.