Development of ${\rm L}1_{0}$ FePt:C (001) Thin Films With High Coercivity and Small Grain Size for Ultra-High-Density Magnetic Recording Media

The FePt:C films with different volume fractions of carbon were epitaxially grown on the CrRu(200) underlayer with Pt and MgO intermediate layers. The magnetic properties and microstructure of these FePt:C films were investigated. The FePt:C films grown on Pt intermediate layer consisted of a continuous layer of FePt, with overlying granular FePt grains. The FePt:C films grown on MgO intermediate layer consisted of a granular FePt:C layer with overlying granular grains. The formation of the overlying granular FePt grains was attributed to carbon diffusion to the surface, which resulted in the second nucleation of FePt. The different interface energy and surface energy of FePt on Pt and MgO intermediate layers caused the formation of initial continuous FePt layer on Pt intermediate layer and initial granular FePt layers on MgO intermediate layer. The out-of-plane coercivity measured at room temperature increased from 10.2 to 19 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 kOe, respectively. The coercivity of the exchange coupling assisted FePt:C perpendicular media was indeed substantially reduced.