Cobalt ferrite thin films were prepared at substrate temperature(Ts) ranging from room temperature to 300°C by the targets facing type of sputtering. All the as-deposited films were composed of oxides and metals. When films were sputtered at Ts=150°C or below, they were mainly composed of oxides. When films were deposited at Ts=200°C or above, they were mainly composed of metals. The magnetization(M) of the latter was twice as large as that of the former. However, and films had in-plane magnetic anisotropy, and small values of Hc.
The cobalt ferrite thin films, which were deposited at Ts=150°C or below, with perpendicular magnetic anisotropy were obtained by means of the annealing at 300°C in air. This was caused by the shape magnetic anisotropy with columnar structure as well as the magnetocrystalline anisotropy of CoFe₂O₄. The Faraday rotation of the annealed films were smaller than that of as-deposited ones, because the surface of the annealed films became rough. The film which was prepared at Ts=100°C and was annealed at 300°C had the perpendicular magnetic anisotropy, and its magnetic characteristics: M=177emu/cc, Hc =1.51kOe and Sq=0.45(corrected squareness ratio=0.71). The Faraday rotation angles of the film had the maximum value of 3.67deg./μm.