Friction, Heat, and Slider Dynamics During Thermal Protrusion Touchdown

Thermal protrusion of the write head in a hard disk drive can be used to control the transition of the slider from flying to contact. Once in contact with the disk, the level of interference can be adjusted gradually by electrical power, making this a very convenient, fast, and high resolution approach for investigating the head disk interface (HDI) during the transition from flying to contact. In this paper we investigate the slider dynamics during the transition from flying to contact, as well as at controlled levels of contact interference. In particular, the touchdown-takeoff hysteresis is analyzed by monitoring friction, read element resistance, tribo-current, acoustic emission and laser Doppler vibrometer signal from the slider. A novel disk texture was developed that significantly improved the contact dynamics and hysteresis. On circumferentially smooth media we observe increased friction, heat, slider bouncing vibrations, and increased hysteresis