THE EFFECT OF LUBRICANT-ROUGHNESS RATIO, LAMBDA (LAMBDA), ON TRIBOLOGICAL PERFORMANCE OF MAGNETIC THIN-FILM DISKS

A dimensionless parameter ''Lambda'' (Lambda), defined as the ratio between lubricant thickness and overage roughness (RMS), is used to optimize tribological performance of head/disk interface (HDI). Sputtered disks having a wide Lambda range (0.15-2.8) were tested for stiction, friction, glide, and CSS performance. The difference in initial ambient stiction for various disks is negligible if Lambda < 0.5, but is significant if Lambda > 0.5. In ambient and wet CSS, an optimal Lambda value is 0.57 for disks of 7.4 nm RMS roughness. Disks of low Lambda values show high stiction due to insufficient protection in ambient and more water absorption in high humidity environment. Disks of high Lambda values have larger stiction modulation due to thick lubricant. The dependence of stiction on Lambda agrees with the Li-Talke stiction model. The critical Lambda phenomenon can be used to explain other reported experimental results.