Transition noise model for longitudinal thin-film media

The integrated noise power in longitudinal thin-film media increases with transition density. This behavior has been attributed to transition noise predominating over the more conventional amplitude modulation noise. At low recording densities the total noise power increases linearly with the transition density. At higher recording densities the noise increases more rapidly. The departure from the linear noise power increase with transition density has been attributed to correlation between noise in adjacent transitions. A model is presented for the noise process in longitudinal thin-film media, assuming that each transition´s position fluctuation is correlated to the previous transition´s position fluctuation by the demagnetization field. The dominant effect of the demagnetization fields is to increase the inherent noise in each transition and broaden the transitions as the recording density increases. It is the inherent noise increase in each transition, rather than the contribution from the adjacent transition correlation noise power term, that explains the experimentally found nonlinear noise power increase at higher transition densities. The frequency dependence of the integrated noise power is shown to be a strong function of the transition shape.