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).