Friction and Heat at the Head Disk Interface caused by Thermal Protrusion Touchdown

The head disk interface spacing in current disk drives is controlled by thermal protrusion of a small heater coil near the read write element of the slider body. By adjusting the power to the heater coil, the clearance can be very accurately adjusted. In addition to controlling clearance, the amount of interference can be adjusted when going into contact. In this paper, we investigate the slider dynamics during the transition from flying to contact. In particular, the touchdown/takeoff hysteresis is analyzed by monitoring the friction, MR resistance, tribo-current, acoustic emission and laser Doppler signal from the slider. A novel disk texture was developed that significantly improved the contact dynamics and hysteresis. When comparing disk roughness, we observe increased clearance on smoother disks, however, when going into contact, increased friction, heat, slider bouncing vibrations, and increased hysteresis is observed.