A Method to Measure the Media Lubricant Loss After HAMR Recording

Heat assisted magnetic recording (HAMR) is anticipated to increase the areal density in hard disk drives to multiple Tb/in². During HAMR recording, as a near filed laser light heats the media to the temperature above Curie point to assist magnetic switching, the lubricant that is typically applied to the disk surface will be under an intensive thermal stress, which will lead to the lubricant desorption and/or decomposition, and frequently accompanied with the underneath carbon overcoat (COC) graphitization and oxidation. Due to the optical properties change of the COC at such a high temperature, the traditional optical techniques are not appropriate to measure the lubricant thickness post HAMR recording. In this paper, we introduce a new method based on atomic force microscopy (AFM) in different imaging modes to detect the lubricant and also COC thickness change as a result of laser heating with a vertical resolution at the angstrom scale. Using AFM in a soft tapping mode, we can also characterize the lubricant thickness variation with time after laser exposure, which enables the measurement of the lubricant reflow kinetics on HAMR media.