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

We proposed a methodology for determining the demagnetization effect (magnetic damage) created by scratches on the surface of the perpendicular magnetic recording disks of a hard disk drives (HDDs). Scratches, which may occur on the disk’s surface during head and disk contact, result in read and write errors on the HDD. Investigating the amount of magnetic damage is thus an important issue. In this study, the scratched area composed of scratches having a fine pitch and shallow depth were generated, and Kerr loop measurements on the normal and scratched area were conducted. Magnetic damage was then estimated from the difference of Kerr loops. By comparing the results of the proposed methodology with the results of a previous methodology using a magnetic force microscopy, it was confirmed that the proposed methodology can be used to quantitatively evaluate scratch-induced magnetic damage.