Experimentally observed roughness effects on the air bearing in the pseudo-contact spacing regime

Recently, sliders with fly heights less than the mean free path of an air molecule have begun to appear in commercial drives. In this near-contact regime, the surface roughness heights of the slider and disk are of the same order as the spacing. Previous numerical and experimental results indicate that surface roughness could significantly effect the fly height in this regime. A new laser interferometer system developed by CML was used to experimentally measure the spacing between an IBM 63% tri-rail slider and disks with different surface roughnesses. Two effects due to disk surface roughness were found: higher fly heights were obtained for smoother disks, and an instability in the air-bearing was observed at low speeds on an ultra-smooth disk.