Carbon Capping Layer Effect on Magnetic Properties and Microstructure of FePt/MoC/CrRu Films

A capping C layer with various thicknesses was sputtered on FePt/MoC/CrRu/glass and postannealed from 190 °C to 365 °C. The optimal magnetic property was obtained at 2 nm-thick C layer annealed at 268 °C and used to discuss an FePt thickness effect. The FePt films with a thickness of 4-10 nm were deposited on MoC/CrRu at 425 °C using magnetron sputtering. The MoC intermediate layer was epitaxially grown on the (200) textured CrRu seed layer, and the FePt film was prepared on the (200) textured MoC at 425 °C. The FePt film shows strong (001) texture, and the out-of-plane coercivity of 7.5 kOe has been demonstrated in 10 nm-thick FePt film. After capping a 2 nm-thick C layer and postannealed at 268 °C, the out-of-plane coercivity was increased to 10 kOe compared with FePt without C capping. From microstructure, the FePt grains were distributed in- or between-islandlike structure and further separated by excess carbon from a capping carbon layer and an MoC intermediate layer.