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(5 nm)/Al2O3(1 nm)/CoFe MTJs had room-temperature (RT) magnetoresistance (MR) ratios ranging from -26% to 18%, and Fe3O4/MgO(6 nm)/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 1 V, and normal MR was evident when vertical bar V vertical bar > 1 V because the nontunneling current was dominant. (c) 2008 American Institute of Physics.