Co-Pt Clusters on a Highly Oriented Fe-Co Soft Underlayer in a Co-Pt-TiO₂ Perpendicular Medium

Abstract

A granular-type medium with a highly oriented high-B_s Fe-Co soft underlayer (SUL) and a thin Ru intermediate layer of 4 nm was prepared. It displayed low H_ch (H_c in the hard axis direction) value of 1.1 Oe in the SUL and high H_c of 6.0 kOe in a Co-Pt-TiO₂ recording layer. The recording layer in the medium has a novel granular structure, namely, well-isolated clusters composed of 5-15 pieces of small Co-Pt grains 4-7 nm in diameter segregated by TiO₂. The clusters were oval, with an average area of 213 nm². At present, the shape and arrangement of the clusters cannot be controlled successfully.