Model for Demagnetization-Induced Noise in Thin-Film Magnetic Recording Media

A linear, statistical model is described which predicts the power spectrum of measured noise in bulk-demagnetized (i.e., ac-erased) thin-film magnetic recording media. It is shown that the noise is the result of magnetic flux which is ascribed to erasure-induced transitions along the track length in the medium. The noise power spectrum for a rigid disk medium is shown to correspond to the power spectrum of Poisson-distributed induced transitions along the track length, while noise along the track width is sufficiently described in terms of a uniform, average magnetization with small variance. Experimental data from two thin-film disks are used with the model to estimate the Poisson parameter for each disk. It is demonstrated that ac-erased noise from particulate media can be considered as a limiting case of the Poisson model.