Modified MGL Equation Considering Both Effects of Surface Roughness and Accommodation Coefficient for Ultra-thin Gas Film Lubrication

The clearance between the read/write head and the disk surface, which is normally referred to the flying height (FH), should be small and stable as the FH is one of the important components of the headmedia spacing [1–2]. To achieve a higher areal density, the FH of the slider continuously decreases and has been reduced to about 1–2 nm in modern disk drives [3–4]. Under such low spacing, the considerations of gaseous rarefaction effects and roughness effects of the magnetic recording system become more important. By solving modified Reynolds equation, effects of gaseous rarefaction and surface roughness were investigated [5–6]. The influence of surface accommodation coefficient (AC), which determines the behavior of the reflected molecules at the boundary walls, is an important factor to govern the flying characteristics of the air bearing slider [7–8]. By solving modified molecular gas film lubrication (MGL) equation, which governs ultra-thin gas film lubrication problems, effects of surface accommodation were investigated [9–10]. However, most of the published work considered gaseous rarefaction effects with either surface roughness effects or surface accommodation effects.