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 Angstrom, which was increased to about 2000 Angstrom 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 (Delta theta(50) = 1.6 degrees).