The effect of lubricant-roughness ratio, Lambda (Λ), on tribological performance of magnetic thin film disks

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