Fe3O4 and its magnetic tunneling junctions grown by ion beam deposition

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 [1 (1) over bar0] 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 2x2 mum(2) to 9x9 mum(2) were fabricated by optical lithography. The junctions show magnetoresistance ratios of similar to14% and no geometrical effect due to the junction size. (C) 2003 American Institute of Physics.