Friction force microscopy study of lubricant thin films on thin-film magnetic recording media

Abstract

The microscopic frictional properties of lubricant thin films on thin-film magnetic recording media [metal-evaporated (ME) tape] were investigated with a friction force microscope in order to understand the intrinsic frictional properties of the lubricant on the ME tapes. We propose the microscopic effective friction coefficient, the friction force normalized by the normal force based on the JKR theory, of the lubricant thin films, which is the critical parameter to understand microscopic friction phenomena. It is found that the microscopic effective friction coefficient of the lubricants on the ME tapes is not dependent on the surface roughness of the media, but the macroscopic friction coefficient of the lubricants is dependent on the surface roughness. This suggests that the effective friction coefficient describes the intrinsic friction properties of the lubricant materials on the ME tapes in the microscopic level. It is also found that the magnitude of the microscopic effective friction coefficient is dependent on the lubricant materials on the ME tapes and is in fair agreement with the relative intensity of the macroscopic friction coefficient for three kinds of the lubricants. This indicates that lubricants with smaller effective friction coefficients correspond to the lubricants with lower friction properties. Furthermore, concerning the two-dimensional distribution of the friction force, it is found that the friction force of the higher part of the surface grains is lower than that of the lower part of the surface grains.