Fe 3 O 4 and its magnetic tunneling junctions grown by ion beam deposition

Abstract

Magnetic properties of Fe3O4 and magnetic tunnel junctions with Fe3O4 bottom electrode have been investigated. Highly conductive V/Ru layers were used as an underlayer of the Fe3O4 films. The V/Ru/Fe3O4 on [110] out-of-plane oriented MgO single crystal substrate show an anisotropy and high squareness along [11̄0] direction, while the Fe3O4 films with an underlayer of just Ru show isotropic behavior and low squareness. X-ray diffraction shows tensile stress on Fe3O4 for V/Ru/Fe3O4 samples. The anisotropy was shown to be induced by the stress. Finally, magnetic tunnel junction stacks of MgO/V/Ru/Fe3O4/AlO/CoFe/NiFe/Ru were deposited and the magnetic tunnel junctions with a junction size ranging from 2×2 μm2 to 9×9 μm2 were fabricated by optical lithography. The junctions show magnetoresistance ratios of ∼14% and no geometrical effect due to the junction size.