An Atomistic Study of Perfluoropolyether Lubricant Thermal Stability in Heat Assisted Magnetic Recording

At the head disk interface (HDI), the stability of the perfluoropolyether (PFPE) lubricant and carbon overcoat (COC) materials must be preserved under HAMR conditions. In this work, we investigate this issue by comparing the effects of transient versus steady heating of Zdol to replicate the precise pulsed heating of the HAMR system. These effects include changes in intermolecular lubricant bonding, molecular decomposition and desorption. In order to accurately account for potential changes in covalent and intermolecular bonds, we utilize the cutting-edge molecular simulation method of ab initio molecular dynamics. To simulate constant heating, a series of constant temperature simulations are performed at temperatures ranging from 300 K-700 K where the temperature is maintained via the Nose Hoover thermostat. For the transient heating simulations, the temperature is ramped over 100 K intervals with initial temperatures ranging from 300 K to 700 K. These heating studies are performed for bulk PFPE systems as well as PFPE-COC configurations to highlight the effect of PFPE-COC adhesion on lubricant thermal stability at the HDI. In the PFPE-COC simulations, we evaluate the amount of desorption versus decomposition as a function of initial temperature. Through our analysis, we are able to reveal the molecular mechanism of PFPE depletion as a function of functional group composition and, thereby, provide design criteria for lubricant molecular architecture in HAMR applications.