David H. Jen

Potential data loss due to head/disk contacts during dynamic load/unload

A functioning IBM drive was converted into a component load/unload tester in order to determine the consequence of full-speed loading and unloading of a slider on top of magnetic data. Tests using this apparatus show that the disk scratch damage produced by load/unload is necessary but not sufficient to result in defects that are detectable by surface analysis test. Comparison of the AFM of the scratch damage sites with the MFM of the surrounding data bits shows that data loss results from the physical damage and that any magnetostriction effect is negligible.

Investigations of Fly Height Changes Due to Small Particles using Capacitance Measurements

Laser texturing has been introduced recently on high performance magnetic rigid discs to optimize trobological performance. while supporting low glide. However, during take-off and landing, system resonances (i.e., slider body. AE sensor, etc.) excited by the periodic laser bump array can cause enormous AE readout, even in the absence of contact, leading sometimes to erroneous glide testing results. In this paper, the dynamics of a slider flying over laser texture will be analyzed in the framework of a joint timdfrequency analysis (spectrogram). It will be shown that the input excitation by the regular laser bump array remains strong. even up to the loth harmonics. When these input excitations intercept system resonances, a strong AE signal is observed. Individual and combined effects of head, laser texture characteristics, and AE (PZT) sensors on glide methodology will be discussed. novel. non-periodic texture patterns will be described, such as pseudo-random and spiral-line laser texture. Techniques for generating them will be discussed briefly, and spectrogram analysis will demonstrate that, as predicted, the pseudo-random texture shows a dramatic reduction in input excitation. while the spiral-line laser texture removes them completely.