In-Plane Uniaxial Anisotropy of Cobalt Ferrite Films Epitaxially Grown on MgAl2O4 (110)

We have investigated the magnetic properties of cobalt ferrite films epitaxially grown on MgAl2O4 (110) substrates. The unit cell of the cobalt ferrite film on the substrate with twofold surface symmetry is tetragonally distorted with c/a < 1, and the film exhibits uniaxial magnetic anisotropy parallel to the in-plane [001] orientation, which is similar to what is observed for films grown on MgO (001). The magnetic easy axis is parallel to the in-plane [001] direction and the magnetic hard axis is parallel to the out-of-plane [110] direction. Careful measurement of the magnetic torque indicates that the anisotropy energy can be described by a combination of uniaxial, fourfold, and demagnetization terms. The uniaxial term is comparable with that obtained for cobalt-ferrite films epitaxially grown on MgO (001).