Rectifying characteristics and magnetoresistance in La0.9Sr0.1MnO3/Nb-doped SrTiO3 heterojunctions

Manganite-based heterojunctions have attracted lots of attention as one of the most promising practical applications of colossal magnetoresistance materials. In this work, heterojunctions were fabricated by depositing La0.9Sr0.1MnO3 (LSMO) films on substrates of 0.7 wt.% Nb-doped SrTiO3 using pulsed laser deposition technique. X-ray diffraction spectra confirmed that the grown films are of single phase and have an orientation with the c-axis perpendicular to the substrate surface. As temperature decreases, the resistivity of LSMO films first increases gradually and then increases abruptly at temperature lower than 150 K. These junctions showed clear rectifying characteristics and strong temperature dependent current–voltage relation. Diffusion voltage decreases as temperature increases. Under forward bias, current is proportion to exp(eV/nkT). Ideal factor increases quickly and tunneling current plays more and more important role as temperature decreases. At 50 K, tunneling current becomes nearly dominant. Large magnetoresistance was observed. The sign and value of such magnetoresistance depends on the direction and value of current.