Molecular Dynamics Simulation of Lubricant Transfer at Head–Disk Interface

To achieve heat-assisted magnetic recording (HAMR), it is crucial to ensure the reliability and durability of the head–disk interface (HDI) which involves high temperatures, nanoscale spacings, and high shear rates. In this study, we performed all-atom molecular dynamics simulations to understand the phenomenon of lubricant transfer at the HDI of HAMR by varying temperature, head–disk spacing, translational speed of the head, and bonding ratio of lubricant films. Nonpolar perfluoropolyether Demnum was used as the lubricant and 1.0 nm thick films were formed on the disk at 300 K. For a narrow head–disk spacing of 2.0 nm, lubricant films distributed continuously within the spacing. At 500 and 700 K, the average lubricant density in the upper half region was observed to reach a saturation value within 2.01 ns. The saturation value was nearly equal to the average lubricant density inside the entire head–disk spacing for zero bonding ratio, but it was slightly smaller for a bonding ratio of 0.6. For wide spacings of 4.0 and 6.0 nm, with increasing temperature, the lubricant molecules stood vertically, rendering lubricant transfer more likely to occur. For the atomically smooth head and disk surfaces used in this study, shear exhibited no clear effect on lubricant transfer.