Thermal Protrusion-Induced Air Bearing Slider Instability at Disk Proximity and Light Contact

As the head-disk spacing is locally reduced to a few nanometers by the introduction of thermal fly-height control sliders, the instability of the flying slider at disk proximity and the detection of slider-disk contacts are of fundamental importance. Slider-disk contacts have been reported in several component-level experimental studies by observing an increase in averaged acoustic emission or laser Doppler vibrometry signals. In this paper, we investigate the transient slider dynamics at multiple locations on a slider body to study the instability from the conditions of disk proximity to light contacts. We define the onset of contact using the pattern transitions of acoustic emission signals, and we study separately the instabilities at the slider's trailing edge center (TEC), leading edge center (LEC), and down-track direction (DTD). The results show there is an evolution of slider instability that occurs during the transition from flying to contacts. Slider dynamics modulation in the DTD are more sensitive to the onset of contacts than at the LEC, whereas the dynamics at the TEC show the least instability. The results suggest that the down-track modulation, which happens prior to a severe TEC modulation, provides a preferred early contact detection criterion that can be used to prevent a more engaged slider-disk contact and mechanical wear.