Catastrophic damage of magnetic recording disk caused by slider-disk impact during loading/unloading

Abstract

Catastrophic damage of a disk caused by impact between a slider and a disk during loading/unloading is investigated using many variations of disk samples with the different scratch resistances. At first, the accelerated loading/unloading test condition to increase disk damage was studied as the function of disk-runout during a disk rotation, rotational speed of a disk, and sweep velocity of a slider using disk samples with the same scratch resistance. Next, in accelerated test conditions, many kinds of disk samples with different scratch resistances were tested to find a relation between disk damage and scratch resistance of thin films. Flyability of a slider over a disk during a slider sweeping in these tests was monitored using an acoustic emission transducer. Disk surface and slider surface after the test was observed using an optical microscope and an optical surface analyzer. Scratch resistance of a disk was measured using a newly developed high-speed scratch tester. As a result, film-peeling damage broke out at the loading position of a disk with increasing disk-runout. Film-peeling damage broke out much more with decreasing scratch resistance of a disk. When scratch resistance of a disk was lower, flyability became bad suddenly during a slider sweeping over a disk; a sweep zone of the disk surface after the test shows damage, such as cross scratches. It is found that disk damage results in not only environmental contamination but also scratch resistance of a disk. This damage brakes out catastrophically. Finally, a mechanism of catastrophic damage is discussed.