Abstract
The mechanism of scratch induced demagnetization is studied for perpendicular magnetic recording (PMR) disk media. The scratches, which may occur on the disk surface during the head/disk contact, caused demagnetization related to read/write error. The relationship between scratch depth and demagnetization were investigated by the scratch test which is quantitative scratch making technique and the AFM/MFM observation. It is found that demagnetization is not due to flaking off of the disk medium, but deformation in the disk inner medium. Moreover, the disk deformations under scratch were analyzed with transition electron microscopy. It was found that the grain of recording layer, which is perpendicular orientated for PMR disk, was tilted under the scratch. The analyses revealed that the scratch resistance which includes tilting resistance is closely related to perpendicular orientated grain of recording layer. A dense and not-easy titled grain structure at recording layer is a must for a reliable hard disk drive.
