Grain density control in FePt granular films for heat-assisted magnetic recording media

To realize high areal density, hard disk drives larger than 4 Tbit in(-2), ultrafine FePt grains of less than 5 nm and grain density larger than 24 T in(-2) are required. Although there have been many investigations to reduce the grain size of FePt, there are only a few reports on the control of grain density. To increase the grain density, we focused on three aspects of the surface morphology and grain density: nucleation sites on the substrate surface, surface free energy, and lattice mismatch. We achieved 14 T in(-2) by maximizing the number of nucleation sites in the FePt-C granular film and found that the surface free energy and lattice mismatch are crucial parameters for controlling the grain density.

Automated summary

To achieve high areal density in hard disk drives, ultrafine FePt grains and high grain density are required. While there have been studies on reducing the grain size, there are limited reports on controlling grain density. This research focused on three aspects of surface morphology and grain density, and found that maximizing the number of nucleation sites and considering surface free energy and lattice mismatch are crucial for controlling grain density.