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 rotating, 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 highspeed scratch tester. As a result, film-peeling damage was broken out at the loading position of a disk with increasing disk-runout. Film-peeling damage was broken 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 is broken out catastrophically. Finally, a mechanism of catastrophic damage is discussed.

A novel methodology for quantitative evaluation of scratch-induced magnetic damage in perpendicular magnetic recording disks

“…Furthermore, the spacing between a head slider and the disk surface has been reduced to increase the recording density of these drives. As a result, the slider and disk contact or the particle sliding between slider and disk easily became to occur and cause super shallow scratches on the disk surface (Shoda 2003;Ovcharenko 2010). Therefore, there is an increased risk of PMR disks experiencing scratch-induced demagnetization (magnetic damage) effects by the scratches (Furukawa 2008).…”

Mechanism study of scratch-induced demagnetization for perpendicular magnetic disks

“…However, with such a narrow spacing, head-disk contact and particle nipping may cause scratches on the disk (Shoda and Tani 2003). In particular, in PMRHDDs, stress-induced demagnetization may occur around the scratches (Furukawa et al 2008).…”