Lubricant migration in particulate magnetic recording media

Migration of lubricant from the porous magnetic coating and underlayer to the surface in particulate magnetic recording media is studied by dynamic secondary ion mass spectrometry. 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 CF₃ side groups and molecular weight of 9000. The time constant of the lubricant recovery is measured by interrupting the lubricant sputter removal for selected periods. Above crucial lubrication area density, these time constants are in the 100 msec range, while in very depleted conditions they are on the order of 100 sec