Pole tip recession studies of thin-film rigid disk head sliders II. Effects of air bearing surface and pole tip region designs and carbon coating

Abstract

Pole tip recession (PTR) results in an increase in spacing between recording elements and magnetic media which is undesirable for high-density recording. The effects of air bearing surface (ABS) designs, pole tip region designs and carbon coating on the growth of PTR with increasing start-stop cycles have been investigated. A better ABS design for less PTR should reduce contact time between slider and disk during take-off and landing of the slider. Among the two-rail, tail-dragger and negative pressure sliders, the negative pressure slider has shortest contact time during take-off and landing, followed by the two-rail slider and tail-dragger slider. The growth mechanisms of PTR for two-rail slider with or without U-shaped slot consists of knocking-off protruded poles, generation of wear particles and three-body abrasive wear. The PTR reaches a saturated value after a certain start-stop cycles. However, for the tail-dragger slider with square-shaped slot, there is a fourth step of erosion which leads to no saturation of PTR and a relatively rough surface of poles. Mechanisms of PTR for negative pressure slider is similar to the two-rail slider but with a lower saturated PTR value. Carbon coating minimizes or eliminates the PTR growth through reducing static and kinetic friction during take-off and landing, providing a wear-resistant protective layer and eliminating dissimilarities of ABS, thin film structure and poles. Based on this study, we find that negative pressure slider which minimizes contact at head-disk interface and carbon coating which protects thin-film region are desirable alternatives for slider designs. Initial recession is desirable as compared to protrusion.