Effects of bottom layer on recording performance and thermal stability for AFC media

Recording performance and thermal stability of the antiferromagnetically coupled (AFC) media that utilize CoCrPt alloy as the bottom layer were investigated. The dependence of media noise on the bottom layer thickness (t/sub B/) is sensitive to the magnetization of the bottom layer (Ms/sub B/). A strong dependence of media noise on t/sub B/ is observed for the media with high Ms/sub B/ (>0.7 T). Contrary, the media noise is almost constant in the range of t/sub B/=2--5nm for low Ms/sub B/ (<0.7 T). The relationship between Ku.V/kT and t/sub B/ is sensitive to anisotropy field of the bottom layer (Hk/sub B/). Thermal stability can be improved by increasing Hk/sub B/, which is noticeable for the media with thicker t/sub B/.