The Sr content influence on the positive magnetoresistance in La1-xSrxMnO3/Si heterojunctions

We fabricated La1-xSrxMnO3/Si (LSMO/Si) heterojunctions with different Sr doping concentrations (x = 0.1, 0.2, 0.3) in LSMO and studied the Sr content influence on magnetoresistance (MR) ratio. The heterojunctions show positive MR and high sensitivity of MR ratio in a low applied magnetic field. The MR ratio is dependent on Sr content and the low Sr doping in LSMO causes a large positive MR in LSMO/Si junctions. The MR ratio for 0.1 Sr doping in the LSMO/Si heterostructure is 116% in 100 Oe (1 Oe=79.5775 A/m) at 210 K. The mechanism for the positive MR dependence on the doping density is considered to be the competition between the tunneling rate of electrons in e(g)(1) up arrow to t(2g) down arrow band and that to e(g)(2) up arrow band at the interface region of LSMO. The experimental results are in agreement with those observed in La0.9Sr0.1MnO3/SrNb0.01Ti0.99O3 p-n junction. The results indicate that choosing low doping concentration to improve the low field sensitivity of the heterojunction devices is a very efficacious method.