Enhanced low field magnetoresistance of Al₂O₃-La_0.7Sr_0.3MnO₃ composite thin films via a pulsed laser deposition

Al₂O₃-doped La_0.7Sr_0.3MnO₃(Al₂O₃-LSMO) thin films were deposited on Si(111) substrate via a pulsed laser deposition. The deposited Al₂O₃-LSMO composite thin films were characterized by x-ray diffraction, scanning electron microscopy, and electro- and magneto-transport measurements. The main phase in the Al₂O₃-LSMO composite films was the perovskite phase. Texturelike microstructure was observed in the Al₂O₃-LSMO composite films while the average grain size remained almost unchanged compared to the pure samples. The metal-insulator transition temperature decreased as a result of the addition of Al₂O₃ and further reduced with increasing Al₂O₃ content. A maximum low field mangetoresistance of ∼15% was achieved in the 2/20 Al₂O₃-LSMO thin films, which could be well explained in terms of the grain boundary tunneling effect. The composition of the composite thin films can be easily tuned by adjusting the target composition. This method is believed to be applicable to exploring the combinations of other manganites and insulators.