Demagnetization effects in coercivity measurements: a generalized Sharrock model for perpendicular media

In the present paper we develop a generalized form of the Sharrock equation which accounts for demagnetization effects in both remanence and time-dependent coercivity experiments. We show that the inclusion of a demagnetization field leads to an apparent time dependence and rescaling of the attempt frequency, f₀. In this paper we compare the predictions of this model to earlier forms of the Sharrock expression as the strength of the demagnetization interaction and the sweep rate is varied. The mean-field approximation leads to a solvable model where the inclusion of volume and anisotropy distributions can be included in a simple manner.