High sensitivity of positive magnetoresistance in low magnetic field in perovskite oxide p–n junctions

Abstract

Large positive magnetoresistance (MR) and high MR sensitivity in low magnetic fields have been discovered in the Sr-doped LaMnO3 and Nb-doped SrTiO3 p–n junctions fabricated by laser molecular-beam epitaxy. The MR ratios, defined as ΔR∕R0, ΔR=RH−R0, are observed as large as 11% in 5Oe, 23% in 100Oe, and 26% in 1000Oe at 290K; 53% in 5Oe, 80% in 100Oe, and 94% in 1000Oe at 255K. The MR sensitivities are 85Ω∕Oe at 290K, 246Ω∕Oe at 255K, and 136Ω∕Oe at 190K, respectively, with the applied magnetic field changed from 0to5Oe. The positive MR ratios and high MR sensitivities of the p–n junctions are very different from that of the LaMnO3 compound family.