Perpendicular magnetic anisotropy and tunneling conductivity of epitaxial cobalt-ferrite (0 0 1) films grown on nonmagnetic metal films

Abstract We successfully fabricated perpendicularly magnetized cobalt-ferrite Co x Fe 3 - x O 4 + δ (0 0 1) films on nonmagnetic metal TiN (0 0 1) films. We found that the in-plane lattice constant of the Co x Fe 3 - x O 4 + δ (0 0 1) films was larger than the out-of-plane lattice constant. This lattice strain induced perpendicular magnetic anisotropy, and square hysteresis curves were observed in out-of-plane magnetic fields for the Co x Fe 3 - x O 4 + δ (x = 0.4 ∼ 0.6) films. With the decrease of the Co composition from x = 1 to x = 0, the Co x Fe 3 - x O 4 + δ films approached not to conductive Fe 3 O 4 but to insulating γ - Fe 2 O 3 accompanying cation vacancies in the cubic spinel structure. The good tunneling conductivity character was observed for the Co x Fe 3 - x O 4 + δ tunnel junctions. The results open up a possibility that insulating Co x Fe 3 - x O 4 + δ films can be applied to elements of perpendicularly magnetized spintronics devices.