Nanocomposite L10 FePt–SiNx and FePt–SiNx–C films with large coercivity and small grain size on a TiN intermediate layer

FePt–SiNx–C films with high coercivity, (001) texture and small grain size were obtained by co-sputtering FePt, Si3N4 and C on TiN/CrRu/glass substrate at 380°C. Without C doping, FePt–SiNx films with good perpendicular anisotropy and a single layer structure were obtained. However, the grain size was still too large and the grain isolation was poor. When C was doped into the FePt–SiNx films, the out-of-plane coercivity increased due to the decrease of the exchange coupling. In addition, the grain size of the FePt films decreased, and well-separated FePt grains with uniform size were formed. The microstructure of [FePt–SiNx40vol%]−20vol%C films changed from a single layer structure to a multiple layer structure when the FePt thickness was increased from 4 to 10nm. By optimizing the sputtering process, the [FePt (4nm)–SiNx 40vol%]−20vol%C (001) film with coercivity higher than 21.5kOe, a single layer structure, and small average FePt grain size of 5.6nm was obtained, which makes it suitable for ultrahigh density perpendicular recording. ► FePt films with large coercivity and small grain size were obtained. ► C doping could increase the out-of-plane coercivity and improve the isolation. ► All FePt samples showed a high out-of-plane coercivity and low in-plane coercivity.