Magnetic Properties of (CoFe2O4)-(Co-CoO) Composite Films for Perpendicular Magnetic Recording

Cobalt ferrite films were prepared by facing targets sputtering, and then post-annealed at various temperatures (Ta=200-500°C) in air. Their magnetic properties and fine structure were investigated. A coercivity Hc⊥ measured in a perpendicular direction to the film surface of a film deposited at the oxygen gas pressure (Po2) of 0 mTorr and post-annealed at 300°C was 1.5 kOe. The value was 3.5 times greater than a coercivity Hc// measured in a parallel direction to the film surface. This high coercivity ratio Hc⊥/ Hc// showed that this film had the perpendicular magnetic anisotropy. It was investigated by the SEM observation that the perpendicular magnetic anisotropy was mainly caused by the columnar structure of the film. Moreover, the film was found to be made up of a (CoFe2O4)-(Co-CoO) composite by the XPS measurement of the binding energies of Co2p and Fe2p electrons of the film