Enhanced temperature dependent junction magnetoresistance in La0.7Sr0.3MnO3/Zn(Fe, Al)O carrier induced dilute magnetic semiconductor junctions

Metal-semiconductor type junction based on p-type La0.7Sr0.3MnO3 and n-type ZnO, Zn(Fe)O or Zn(Fe,Al)O with different Fe concentrations have been fabricated on (0001) sapphire substrate using pulsed laser deposition technique. While the metal-semiconductor type junction with La0.7Sr0.3MnO3 (LSMO) and ZnO or Zn(Fe)O show very good rectifying behavior, the heterojunction with La0.7Sr0.3MnO3 and Zn(Fe, Al)O fails to show such rectifying characteristics which most likely due to the much higher carrier concentration and thin depletion width. These metal-semiconductor type junctions show reasonably high temperature dependent junction magnetoresistive behavior. At 77 and 300 K all the junctions show negative junction magnetoresistance, whereas they show positive junction magnetoresistance at certain temperature range (150-280 K). The junction MR attains a peak with high positive value similar to 76%, 38%, and 25% for LSMO/Zn(Fe, Al)O, LSMO/Zn(Fe)O, and LSMO/ZnO junctions, respectively, near 250 K, where La0.7Sr0.3MnO3 shows highest spin relaxation near 250 K. The junction magnetoresistive properties have been explained using the standard spin injection mechanism through the magnetic p-n junction. Junction magnetoresistance dies out with the increase of doping concentrations in all the three type of metal-semiconductor type junctions due to the less non equilibrium population of polarized electrons. (C) 2013 AIP Publishing LLC.