Lubricant migration in particulate magnetic recording media

Abstract

Lubricants improve the mechanical durability and reliability of particulate magnetic recording disks by orders of magnitude. However, the lubricant at the surface of the disk is depleted by the sliding or flying of the head and by spin-off. The recovery rate of the lubricant from the porous media to the surface determines the effectiveness of the lubricant. Migration of lubricant from the porous magnetic coating and underlayer to the surface is studied by dynamic secondary ion mass spectrometry (SIMS). The lubricant thickness on the surface of particulate media is evaluated as a function of lubricant areal density. The surface area of the porous coating is found to be about ten times the apparent surface area. Migration rates are determined by matching the sputter removal rate with the lubricant replenishment to the surface. They are typically 15 nm/sec for polyperfluoroether with CF<inf>3</inf>side groups and molecular weight of 9,000. The time constant of the lubricant recovery is measured by interrupting the lubricant sputter removal for selected periods. Above critical lubrication areal density, these time constants are in the 100 msec range, while in very depleted conditions they are on the order of 100 sec. © 1991 IEEE