Lubricant Evaporation and Flow due to Laser Heating With a Skewed Temperature Distribution Induced by Disk Motion

Due to the fast disk rotation, the temperature distribution on the disk under laser illumination in heat-assisted magnetic recording (HAMR) tends to deviate significantly from an axisymmetric distribution. A lognormal approximation scheme for the temperature distribution containing a tail based on a fast-moving heat source solution was proposed for use in an equation for the lubricant film involving evaporation, surface tension, disjoining pressure and thin-film enhanced effective viscosity. The results reveal the process of formation of a lubricant trough: an indent of the lubricant profile first forms and grows to a steady-state depth, followed by a continuous extension at the rate of the disk velocity. Both evaporation and thermal capillarity due to the surface tension gradient contribute greatly to the creation of a trough in the lubricant profile while the latter also causes boundary ridges. Unlike the Gaussian temperature-based solution, the local minimum of the lubricant thickness occurs at the trailing edge of the thermal spot.