Effects of stoichiometry on the magnetic and structural properties of perpendicular barium ferrite thin film media

The effects of stoichiometry factor n on the magnetic and structural properties of perpendicular barium ferrite thin films with composition of BaO .n(Fe2O3) were systematically investigated. Within the range 2.2 < n < 6, the c-axis for barium ferrite thin films can be oriented perpendicularly by the use of Pt underlayer and with optimized processing conditions. Perpendicular c-axis orientation becomes worse as n decreases from 6 to 2.2. The average grain size was greatly reduced from about 2000 Angstrom to 300 Angstrom with the decrease of n. The decrease of the grain size can be related to the existence of nonmagnetic phase BaFe2O4, which was observed by X-ray diffraction.