An explanation of the observed frequency domain behavior of head-disk interface resonances in the proximity recording regime

Magnetic head-disk interfaces (HDI) which are designed so that the mechanical spacing, between the magnetic recording head and spinning disk media, is so small that frequent intermittent contacts occur during normal steady state operation, can be said to be operating in the "proximity" recording regime. Mechanical spacing ("fly height") modulation, with characteristic frequency well above the estimated air bearing resonance frequencies, but well below slider ringing frequencies, has been observed in the proximity recording regime. In this paper, the effect of slider preload change, and the effect of atmospheric pressure change, on the frequency and amplitude of such fly height modulation, as measured using laser Doppler vibrometry, is reported. A simple analytical model was developed to explain the existence of the modulation and its observed dependence on applied gram load.