Spontaneously Formed FePt Graded Granular Media With a Large Gain Factor

In conventional magnetic recording media fabrication processes, magnetically soft regions of composite or graded material are prepared by varying either the substrate temperature or the film composition during deposition. In this work, ultrathin FePt granular media with graded composition was fabricated directly by spontaneous layer diffusion between FePt and Pt layers during the film deposition. Electron energy loss spectroscopy analysis on individual FePt columnar grains identified the composition distribution of Fe and confirmed the Fe composition gradient. A large “gain factor” of 3.74, indicative of a relatively high-thermal energy barrier, was obtained in this spontaneously formed FePt graded granular media.