High coercive L10 FePt–C (001) nanocomopsite films with small grain size for perpendicular recording media

FePt–C films with various C concentrations were deposited on $\mathrm{Mg}\mathrm{O}∕\mathrm{Cr}\mathrm{Ru}$ /glass substrate by cosputtering FePt and C at $350°\mathrm{C}$ . The evolution of magnetic properties and microstructure of FePt–C films with the C concentration were investigated. All FePt films showed (001) preferred orientation regardless of C concentrations. With C doping, a two-layer structure of FePt–C films was formed. The FePt–C underlying layer epitaxially grown on MgO intermediate layer were $L{1}_0$ FePt grains, while the FePt overlayer consisted of fcc FePt phase and $L{1}_0$ FePt phase. The out-of-plane coercivity measured at room temperature increased from $10.2\text{to}19\mathrm{kOe}$ when C concentrations increased from 0% to 15%. Further increasing the C contents to 20% and 25% caused the decrease of coercivity to 17.2 and $14.8\mathrm{kOe}$ , respectively.