Control of orientation and crystallite size of barium ferrite thin films in sputter deposition

Hexagonal barium ferrite thin films were deposited in a facing target sputtering system. Films with random orientation, and c-axis orientation were obtained by depositing the films on a thermally oxidized silicon wafer and on a c-axis oriented ZnO underlayer, respectively. The film deposited on the thermally oxidized silicon wafer had crystallite sizes as large as 1500 Å, which was increased to about 2000 Å by depositing the film on the substrate with ZnO underlayer. The randomly oriented film had a large coercive force of about 4000 Oe and exhibited almost isotropic properties. In contrast, the c-axis oriented film deposited on ZnO underlayer had a large perpendicular magnetic anisotropy field above 10 kOe and exhibited an angular dependence of coercivity consistent with a fanning model, although the film had a smaller coercive force and smaller saturation magnetization. A strong negative magnetic interaction operated between the particles in the perpendicular direction of the film. These BaM films had a large dispersion in coercivity even in the film with excellent c-axis orientation (Δθ₅₀=1.6°)