Experimental Study of Head-Disk Interface Flyability and Durability at Sub-1-nm Clearance

As dynamic fly-height (DFH) sliders with active flying-height (FH) control using local thermal expansion caused by a heating element were introduced in hard disk drives recently, the minimum clearance between the head and disk has been reduced to sub-3-nm. To achieve a higher recording density, the clearance will have to become even smaller, which will make the slider more likely to contact the disk and thus may cause head-disk interface (HDI) instability and slider/disk wear. This paper describes a test to study the flyability and durability of the DFH sliders at sub-1-nm clearance. The test involves the DFH sliders flying for a series of durations at 1 and 0.5 nm clearances. The sub-1-nm clearance was achieved by making the pole-tip protrusion back off 1 or 0.5 nm immediately after an initial touchdown. During flying, the acoustic emission and friction signals were monitored to investigate the slider flyability. The HDI durability was evaluated by inspecting the lube pickup on the slider air-bearing surface, carbon wear of the sliders and disks, and lubricant modulation/depletion using optical microscopy, scanning electron microscopy, and an optical surface analyzer, respectively, after each test. Finally, the possibility of stable on-track flying of the optimized DFH sliders at 1-nm clearance was demonstrated.