Perpendicular magnetic anisotropy in epitaxially strained cobalt-ferrite (001) thin films

We investigated the dependencies of both the magnetization characteristics and the perpendicular magnetic anisotropy of CoxFe3–xO4(001) epitaxial films (x = 0.5 and 0.75) on the growth conditions of the reactive magnetron sputtering process. Both saturation magnetization and the magnetic uniaxial anisotropy constant Ku are strongly dependent on the reactive gas (O2) flow rate, although there is little difference in the surface structures for all samples observed by reflection high-energy electron diffraction. In addition, certain dead-layer-like regions were observed in the initial stage of the film growth for all films. Our results suggest that the magnetic properties of CoxFe3–xO4 epitaxial films are governed by the oxidation state and the film structure at the vicinity of the interface.