The dynamic coupling of the slider to the disk surface and its relevance to take-off height

Recent studies have attempted to correlate take-off height (TOH or Glide Avalanche) of rigid disks to their topography. Roughness average, mean peak height, and waviness have been emphasized, but no model has been proposed that takes into account the dynamic response of the glide slider to the spatial frequency of the disk topography. In this paper, we calculate the frequency response of glide sliders to disk inputs of various wavelengths, using an air-bearing solver. This calculated transfer function is then used to filter the one-dimensional disk topography, obtained with a conventional stylus profiler, using its complex Fourier transform. From the filtered profile, a mean peak height Rpm can be obtained which correlates well with actual TOH values. The slope is close to unity as expected from a first-principle model. Schemes to break down the wavelength range of interest into short (roughness) and long (waviness) parts will be demonstrated, as well as the practical use of optical profilers.