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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 sp^2 cluster size. [ABSTRACT FROM PUBLISHER]

Ever decreasing magnetic spacing in the hard disk drive requires each contribution to the magnetic spacing to be examined for possible reduction. Currently, the lubricant layer on top of the disk carbon overcoat is typically 10\–20\ \\rm\AA thick. This paper studies the contact resistance of nonlubricated disks with the aim of seeking a way to reduce the lubricant thickness contribution to the magnetic spacing. We prepared normally lubricated (\thickness>7\ \\rm\AA), partially lubricated (thickness 3.5\ \\rm\AA), and barely lubricated (thickness 0.5\ \\rm\AA) disks. Partially lubricated disks showed contact wear resistance as good as normally lubricated disks when they were baked in a dry oven. We suggest that this enhanced contact wear resistance comes from the softening (graphitization) of the carbon overcoat and/or reduced number of active sites on the overcoat for water adsorption due to oxidation during the baking. However, corrosion resistance of partially lubricated disks became worse after baking and the amount of lubricant transfer from partially lubricated disk to slider surface did not decrease compared to normally lubricated disks. Barely lubricated disks showed very bad contact wear resistance even after baking, showing that it is necessary to have at least partial lubrication on the disk surface. [ABSTRACT FROM AUTHOR]