Large room-temperature inverse magnetoresistance in tunnel junctions with a Fe3O4 electrode

Magnetic tunnel junctions (MTJs) consisting of Fe3O4 and three-dimensional ferromagnetic metal electrodes with MgO or MgO∕Al2O3 as a barrier layer have been fabricated. Fe3O4∕MgO(5nm)∕Al2O3(1nm)∕CoFe MTJs had room-temperature (RT) magnetoresistance (MR) ratios ranging from −26% to 18%, and Fe3O4∕MgO(6nm)∕CoFe MTJs with a mildly heat-treated Fe3O4∕MgO interface had only inverse tunneling MR ratios that were as large as −8% at RT. The sign of the MR ratio changed when the absolute value of the bias voltage V was about 1V, and normal MR was evident when ∣V∣>1V because the nontunneling current was dominant.