Magnetic Properties of Multilayer ${[({\rm FePt})_{\rm x}/{\rm Os}]}_{\rm n}$ Films

Multilayer [(FePt)_x/Os]_n films (with x being thickness in nm; Os with a fixed thickness 5 nm; n being the number of layers) have been deposited by ion-beam sputtering. Spacer layer was found to have substantial effects on the multilayers to exhibit different magnetic properties and microstructure. The average grain size of the multilayer films can be well controlled by both annealing temperature and thickness of the FePt layer with the Os space layer. The enhancement of H_c can be understood from the fact that for a FePt film with fixed thickness of Os spacer layer, the increasing number of Os spacer layer will inhibit the grain growth of FePt grains and enriches the grain boundary. The layer by layer structure of [(FePt)_x/Os]_n films can control the hard magnetic behaviors. Therefore, the multilayer [(FePt)_x/Os]_n films with Os as the spacer exhibit good hard magnetic properties and are attractive candidates for ultrahigh density magnetic recording media.