High sensitivity of positive magnetoresistance in low magnetic field in perovskite oxide p-n junctions -: art. no. 032502

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 DeltaR/R-0, DeltaR = R-H-R-0, are observed as large as 11 % in 5 Oe, 23 % in 100 Oe, and 26 % in 1000 Oe at 290 K; 53% in 5 Oe, 80 % in 100 Oe, and 94 % in 1000 Oe at 255 K. The MR sensitivities are 85 Omega/Oe at 290 K, 246 Omega/Oe at 255 K, and 136 Omega/Oe at 190 K, respectively, with the applied magnetic field changed from 0 to 5 Oe. The positive MR ratios and high MR sensitivities of the p-n junctions are very different from that of the LaMnO3 compound family. (C) 2005 American Institute of Physics.