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Lubricant reflow for 10 Å Z-Tetraol film is characterized for heat-assisted magnetic recording by numerical simulation using the experimentally determined thickness-dependent diffusion equation. The competition between laser-induced lubricant depletion (troughs) and subsequent healing by reflow is investigated as a function of lubricant depletion rate, trough width, trough depth, and duty cycle (reflow time between successive laser exposures). The simulations include 1, 5, 9 and 13 adjacent troughs. Trough width of 50 nm with an edge-to-edge separation distance of 50 nm and laser depletion rates of 1.0, 0.1 and 0.001 Å/cycle are simulated. Reflow kinetics on 13 troughs with a trough width of 20 nm and an edge-to-edge separation distance of 20 nm is also included to probe the effects in the limit of very small laser spots. Duty cycles of 10 and 100 millisec are used in the simulations. The results of the numerical simulations indicate that trough recovery by reflow increases with increasing duty cycle or decreasing number of adjacent troughs, trough separation distance and laser depletion rate. Conclusions based upon single trough studies are misleading for HAMR interfaces.

Z-dol and Z-tetraol represent most often used disk lubricants. So that we would be better able to design lubricants of higher thermal stability (for Heat-Assisted-Magnetic-Recording application), detailed analysis of thermally induced oxidation processes of Z-dol and Z-tetraol were performed. Samples were heated in a thin-film configuration where facile infusion of oxygen occurred and were examined by F-19 and C-13 NMR. Z-dol was found to be stable in the 150 ∼ 200 °C temperature range. In the same temperature range Z-tetraol was found to undergo either (1) the well known step-wise oxidation of primary alcohol (alcohol → aldehyde → acid) or (2) direct conversion to Z-dol. The latter process is initiated by a base-catalyzed step whereby the end-group Z-O-CF2-CH2-O-CH2-CH(-OH)-CH2-OH converts to an aldehyde, Z-O-CF2-CH2-O-CH2-CH( = O), and CH3OH. Z-dol results upon oxidation of the aldehyde yielding Z-O-CF2-CH2-OH, CH2 = O and CO2. It was found that substitution of the terminal OH with a phenoxy unit suppressed these decomposition processes. Z-tetraol lubricant molecular chains that became bound to the carbon overcoat at their termini are also protected from these oxidation processes. Thus for HAMR application, a combination of lubricants bonded to the carbon overcoat at their termini and mobile lubricants possessing phenoxy groups at their termini may be the best possible system based on perfluoropolyether lubricants.