Some Advanced Air-Bearing Design Issues for Proximity Recording

In magnetic hard disk drives the minimum spacing between the air-bearing slider and disk has been reduced to under 50 nm, and some drives now employ so-called proximity sliders that are designed to operate at some level of interference between the slider and the peak asperities on the disk. This ultra-low flying condition brings into play some new interface phenomena and accentuates some of the well known ones as well. In this paper, we consider some air-bearing design issues related to proximity recording. First, we examine the effects of shear flow in the bearing, which is usually neglected, and we show that for high-pitch proximity slider designs the effect is not negligible. Next, we note that such low spacing also tends to accelerate particle accumulation at the trailing edges of the slider. In an effort to address this problem, a model is developed for calculating forces on particles in the air bearing. Including this in the CML air bearing design code we show that designs can be created that eject most of the particles from the sides rather than trapping them at the trailing edge. Finally, we investigate the performance of proximity sliders with regard to their sensitivity to altitude changes. We include altitude sensitivity as an objective in the design optimization scheme and demonstrate that it can yield air-bearing design with performance much less sensitive to changes in altitude.