Inverse magnetoresistance in single layer Fe3O4 film

Abstract

Half-metallic magnetite with high spin polarization at the Fermi level has always been an ideal candidate for spin dependent transport study, and understanding of the magnetic transportation property of Fe₃O₄ becomes a critical issue for its future applications in spintronics. Generally the resistance of Fe₃O₄ decreases (negative MR) when applied in a magnetic field as the conduction in Fe₃O₄ is attributed to a small polaron hopping mechanism between Fe²⁺ ions and Fe³⁺ ions in oxygen ions octahedral sites, and the applied field is suggested to broaden the polaronic band leading to enhanced conduction. Previous studies on magnetic transportation of Fe₃O₄ film also confirm its negative MR effect, and positive MR effect is only observed in a few specific structures such as TiN/ Fe₃O₄ superlattices, magnetic tunnel junctions with Fe₃O₄ electrode, the increase of resistance after application of magnetic field for these system is ascribed to the spin selective quantum confinement effects in the heterostructure, which refer to the extrinsic structures instead of the intrinsic magnetic transportation property of magnetite film. However, in our recent studies, an anomalous positive magnetotransport behavior is demonstrated on high oriented Fe₃O₄ film grown on Si substrate at high temperature, and the inverse MR effect is believed to be highly correlated to the strong orientation of Fe₃O₄ film.