Effect of van der Waals Force on Air-Bearing Flying Characteristics at Ultra-Low Fly Height

Abstract

In order to increase recording density for magnetic recording systems, the fly height of slider, as part of head-media magnetic spacing, has to remain ultra-low through proper air-bearing designs. At these ultra-low fly heights, the presence of interfacial forces, such as van der Waals (vdW) force, can significantly affect air-bearing flying characteristics. In this paper, one air-bearing design has been studied at ultra-low fly heights with a proprietary air-bearing simulation code, where a Lifshitz-theory-based fully retarded vdW force model was applied on the multilayered head-disk interface (HDI), in contrast to most studies with a “nonretarded” single-layer approach. This results in a lower static fly height and a higher touch down/take-off velocity, which clearly demonstrates the necessity of performing the fully retarded calculation on a realistic layered model of the HDI for accurate vdW force predictions. A further breakdown of the vdW force components shows a dominant pitch moment contribution. This is attributed to a nonuniform Hamaker function distribution, which is highly dependent on air-bearing designs.