Investigation of heat transfer across a nanoscale air gap between a flying head and a rotating disk

Understanding nanoscale heat transfer at the head-disk interface (HDI) is necessary for thermal management of hard disk drives (HDDs), especially for heat-assisted magnetic recording and microwave-assisted magnetic recording. To accurately model the head temperature profile in HDDs, it is imperative to employ a spacing-dependent heat transfer coefficient due to the combined effects of pressurized air conduction and wave-based phonon conduction. Moreover, while flying at near-contact, the fly height and heat transfer are affected by adhesion/contact forces in the HDI. In this study, we develop a numerical model to predict the temperature profile and the fly height for a flying slider over a rotating disk. We compare our simulations with touchdown experiments performed with a flying Thermal Fly-Height Control (TFC) slider with a near-surface Embedded Contact Sensor (ECS), which helps us to detect the temperature change. We incorporate the effects of disk temperature rise, adhesion/contact forces, air and phonon conduction heat transfer, and friction heating in our model. As the head approaches the disk with increasing TFC power, enhanced nanoscale heat transfer leads to a drop in the ECS temperature change vs TFC power curve. We find that the exclusion of the disk temperature rise causes the simulation to overestimate the ECS cooling drop. The incorporation of adhesion force results in a steeper ECS cooling drop. The addition of phonon conduction in the model causes a larger ECS cooling drop. The simulation with friction heating predicts a larger ECS temperature slope beyond contact. The simulation with these features agrees with the experiment.