Agglomerates and media-noise of ultra-thin coated rigid disks

Abstract

This paper discusses the media-noise properties of ultra-thin coated rigid disks and their origin. The ultra-thin coated rigid disks using Co-γFe 2O 3 fine particles were obtained after spin-coating Al-substrates with magnetic paints. Thickness values between 0.12 and 0.33 μm were obtained after controlled spin-coating. After removing high protrusions on disk-surfaces, the read/write properties of ultra-thin coated rigid disks were investigated using a MIG head. The media-noise properties of the ultra-thin coated disks were compared with those of a conventional particulate disk and a thin film disk. The signal-recorded noises, the dc-erase noise, and the reverse dc-erase (RDC) noises were measured. A peculiar recording density dependence for the signal-recorded noise was found. The signal-recorded noise of the ultra-thin coated disks has a maximum value at a density of 17.5 kFCI. In the region below 17.5 kFCI, the signal-recorded noise increases like a thin film disk as the recording density increases. In the region larger than 17.5 kFCI, the signal-recorded noise decreases like a conventional particulate disk as the recording density increases from 17.5 kFCI. This peculiar dependence is caused by cohered agglomerates which consist of randomly oriented magnetic particles in the magnetic layer of the ultra-thin coated disks.