Theoretical Analysis of Magnetic Recording Media Noise

The noise properties of magnetic recording media partly depend on the type of medium, i.e., whether the medium is of the magnetic thin film type or the particulate type. In magnetic thin film media, such as Co-Ni-P plated disks, the lowest noise level is that of dc-erased noise, and when signals are recorded after dc-erasure the level of the modulation noise increases gradually as the recording wavelength is shortened, until it reaches a maximum level at a certain wavelength. On the other hand, in particulate media, the noise level is highest for modulation noise, followed in turn by dc-erased noise and ac-erased noise. In the analysis described in this paper, the irregular fluctuations in the direction of magnetization and the number of magnetic particles per unit volume have been taken into account, and the results of the analysis make it clear that the relative noise level of the ac-erased, dc-erased, and modulation noise depends on these fluctuations.