Magnetic isolation for Hf-capped CoPtCr-SiO₂ perpendicular media by postannealing

Effect of post-annealing on magnetic properties for Hf-capped CoPtCr-SiO₂ perpendicular granular recording media was investigated. It was found that Hf diffusion improved magnetic isolation among magnetic grains of the post-annealed media. Detailed analysis revealed that; non-magnetic layer was formed after post-annealing by interdiffusion of Hf and magnetic grains, retaining saturation magnetization and uniaxial magnetic anisotropy of a columnar part. The results suggest that capped Hf reacted with ferromagnetic Co into non-magnetic CoHf compound at the boundaries of the columns by diffusing through Si-O rich grain boundary.