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IR Microscopy Applied to Slider Rail Depletion of Lube on a Thin-Film Magnetic Recording Disk

Volume 44, Number 8 (Oct. 1990) Page 1415-1416

Mastrangelo, C.J.; Von Schell, L.; Le, Y.

Liquid lubricants reduce friction and wear at the recording surface of rigid magnetic disks. Loss of this lubricant can come from centrifugal effects, from evaporation, and from periodic contacts of the recording head slider rails with the lubed disk surface. Magnetic disk lubricant levels have been quantified by ESCA, by IR spectroscopy, and by ellipsometry. However, ellipsometry techniques on multilayered thinly lubed magnetic disks are complicated by multi-angle measurements and numerical calculations that are difficult to apply, while ESCA requires exposure of the lube to undesirable high-vacuum conditions. Infrared spectroscopy is easy to apply, avoids vacuum concerns and, with a grazing angle approach, has very good sensitivity. Also desirable is the capability of submillimeter spatial resolution. A device that meets these requirements is a Grazing Angle Microscopy (GAM) for infrared spectroscopy. Aside from providing magnification to analyze very small spots, a GAM with 65 to 80° incident illumination also provides the enhanced sensitivity to very thin films that ordinary IR microscopes (with normal incident illumination) lack. An example of this sensitivity is shown in Fig. 1, where the GAM measured absorbance for a 0.5 × 0.2 mm spot is distinguishable below 10 angstroms (1 nm) of perfluoropolyether lube thickness. In this study a GAM was used to quantify the polyether lube depletion on a developmental thin-film disk within the contact points of the recording head slider rails used in a routine wear test (i.e., oscillatory wear tester).