Possibility of surface force effect in slider air bearings of 100 Gbit/in2 hard disks

The recording density has been increasing in a high rate of 60% per year in the last 10 years. In the next several years it is expected that the recording density will be 100 Gbit/in2 and then 1000 Gbit/in2. It is said that a spacing of about 5 nm will be necessary for 100 Gbit/in2. For two solid surfaces with such a small spacing, it is expected reasonably that the surface force will come into action. In this paper, numerical analysis was conducted to explore the possibility of the surface force for the slider air bearing working with respect to the glide avalanche. The numerical results show that surface force reduces the stiffness of the slider air bearing and the load carrying capacity as well. It is worth noting that, although the decrease in the load carrying capacity may not be significant, the reduction in the stiffness may be critical for many cases. The reduction in the stiffness of slider air bearings due to the surface force may be one of the most important mechanisms of the glide avalanche. The predicted take-off height to overcome the surface force is about several nano-meters. Increasing the pitch angle tends to decreases the take-off height. A lubricant film of about 1 nm will reduce the risk of the glide avalanche in some extent, but increasing the film thickness has little effect.