The average power density spectrum of the readback voltage from particulate media

An excellent report on the spectrum of readback voltages from magnetic media can be found in Ref. [1] (Thurlings) where the power density spectrum was developed from basic assumptions on the distributions of the particles in the media. In attempting to fit our experimental observations with the above model, it was found that the expressions suggested in [1] had to be extended in order to fit the variations in gain as a function of frequency of the written signal. The extensions include the formulation of a simple but adequate model for magnetic interaction among particles. This interaction model explains the dependence of noise on the frequency of the written signal.