Measurement and Simulation of Nanoscale Gap Heat Transfer Using a Read/Write Head with a Contact Sensor

Heat-assisted magnetic recording (HAMR), microwave-assisted magnetic recording, and other new technologies are being developed to boost the storage capacity of current hard disk drives (HDDs). Understanding the mechanisms of heat transfer across the head-disk interface is of major importance, because it is closely related to the design of HDDs, including lubricant flow and contact issues, especially for the reliability design of HAMR drives. In this paper, we report on a series of experiments and simulations with a perpendicular media recording (PMR) head to better understand the head temperature change and to validate the wave-based phonon conduction theory. From the static touchdown experiments, it is found that even without the air bearing, the head temperature of the thermal flight-height control (TFC) slider reduces when the clearance between the head and disk is less than 1 or 2 nm. The effect of lubricant on the disk surface is also studied. When the head temperature is relatively low, repeated touchdowns show that the starting point gets closer to the disk, suggesting that meniscus forces from the lubricant on the thermal fly-height control protrusion gradually reduce the head-disk clearance. But when the head temperature is relatively higher, the head can 'melt through' the lubricant layer. The wave-based phonon conduction theory is integrated into an ANSYS simulation to study the steady state temperature distribution and protrusion profile of the head in the static touchdown experiments. The simulation result shows the same trend as the experiments of cooling before the head is in contact with the disk.