Thermo-molecular Gas-film Lubrication (t-MGL) Theory Considering Temperature Distributions and Accommodation Coefficients at the Boundary

―Flying Characteristics based on Free Molecular t-MGL Equation―

Abstract

As new magnetic recording techniques, thermal fly-height control (TFC) and heat-assisted magnetic recording (HAMR) have been investigated in order to increase the recording density of hard disk drives (HDDs). When the spacing is less than about 10 nm, the flow in the lubrication region is close to the free molecular flow, since spacing h is less than mean free path λ of the gas. In this paper, we derived the free molecular t-MGL equation considering temperature distributions and accommodation coefficients at the boundary, for examining thermo-molecular gas-film lubrication (t-MGL) characteristics in several nanometers. Moreover, we show numerically the effects of accommodation coefficients on the basic characteristics of pressures and shear stresses in free molecular region.