Properties of CoFe2O4 Films Prepared by Annealing Co/Fe Multilayered Films in the Atmosphere

CoFe2O4 films were fabricated by air annealing of Co/Fe multilayer films prepared by sputtering onto glass substrates. During sputtering, the thickness of the Co and Fe layers and the number N of Co/Fe bilayers were varied, while the total film thickness was held at 2000 Å. The oxide films exhibited a large coercive force near 3 kOe, and the largest Kerr rotation, 0.8° (¿=825 nm), was obtained at a Co:Fe ratio of 1:2 and with N=40. Perpendicular magnetic anisotropy was obtained in (400)-oriented CoFe2O4 films prepared from Fe (200)-oriented multilayer films, through appropriate control of the Co concentration, number of bilayers N, substrate temperature, and background gas pressure. Auger electron spectroscopy analysis revealed that the distribution of Co and Fe atoms is not uniform in the oxide films.