Head–Disk Interface Materials Issues in Heat-Assisted Magnetic Recording

Abstract

In this paper, some issues concerning the reliability of heat-assisted magnetic recording (HAMR) media are highlighted. The large roughness of the grain structure originates from a surface energy mismatch between the FePt grains and the graphene-like segregant material. A simple roughness model, based on interfacial energies, is proposed that can quantitatively predict media grain structure and roughness. The thermal behavior of the disk lubricant is reviewed both experimentally as well as theoretically using molecular dynamics (MD) and density functional theory (DFT). The lubricant film can be subjected to evaporation and oxidation, both of which follow an Arrhenius reaction rate. MD also predicts that the disk carbon overcoat can undergo structural changes under thermal transient exposure in the nanosecond time frame, and Raman imaging performed on a disk zone that was HAMR written shows small but unequivocal changes, consistent with an increase in carbon sp2 cluster size.