Control of grain density by varying lattice mismatch in FePt-C film for heat assisted magnetic recording

Abstract

Controlling the number density of grains in magnetic recording media is critical for improving the areal density of the recording. Herein, we report the dependence of grain density and microstructure of FePt-based granular films for heat-assisted magnetic recording media on the lattice mismatch between the FePt films and substrates SrTiO3, MgAl2O4, MgO and TiO2. The grain density and grain size of the FePt films increased and decreased, respectively, with the increasing lattice mismatch between the films and substrates. The optimum lattice mismatch for the FePt-based granular films was found to be 8%, which corresponds to the MgO substrate. FePt films grown on TiO2 substrate, which had the largest lattice mismatch of 16%, showed poor morphology and low grain density. The results imply that an underlayer with which a film develops a suitable mismatch plays a key role in controlling the microstructure and magnetic properties of the film.