Effects of lift on the motion of particles in the recessed regions of a slider

Abstract

Particle contamination in a cavity, or a recessed region, on the slider surface is an important issue in slider designs for magnetic recording. In this paper, a model is developed for the simulation of particle motion in a recessed region, in which various forces such as viscous drag, Saffman lift, Magnus lift, and gravity are considered. It is found that the latter two forces have a very small effect on the vertical motion of the particles compared with the Saffman lift, and they can be neglected in the analysis. It is also found, through the simulation for various cases, that the Saffman lift is not so important for the motion of the smaller particles (d<100 nm) as for the motion of larger particles, and that the magnitude of the velocity of particles relative to the air flow affects the Saffman lift, or vertical motion of the particles, significantly. The air flow velocity is relatively low in a recessed region, and a particle often has a large relative velocity with positive sign when entering it, which causes the Saffman lift force to point to the surface of the slider. Therefore, particle contamination on the slider occurs at the edges of the recessed region. A similar result can also be obtained for the particles entering an air bearing under a taper, which explains why the contamination is concentrated on the surface of tapers.