Fe_(3)O_(4) and its magnetic tunneling junctions grown by ion beam deposition

摘要

Magnetic properties of Fe_(3)O_(4) and magnetic tunnel junctions with Fe_(3)O_(4) bottom electrode have been investigated. Highly conductive V/Ru layers were used as an underlayer of the Fe_(3)O_(4) films. The V/Ru/Fe_(3)O_(4) on 110 out-of-plane oriented MgO single crystal substrate show an anisotropy and high squareness along 110 direction, while the Fe_(3)O_(4) films with an underlayer of just Ru show isotropic behavior and low squareness. X-ray diffraction shows tensile stress on Fe_(3)O_(4) for V/Ru/Fe_(3)O_(4) samples. The anisotropy was shown to be induced by the stress. Finally, magnetic tunnel junction stacks of MgO/V/Ru/Fe_(3)O_(4)/AlO/CoFe/NiFe/Ru were deposited and the magnetic tunnel junctions with a junction size ranging from 2×2 μm~(2) to 9×9 μm~(2) were fabricated by optical lithography. The junctions show magnetoresistance ratios of ～14 and no geometrical effect due to the junction size.