Magnetization reversal by a field pulse

The stochastic dynamics of a thermally relaxing uniaxial superparamagnetic particle are studied here by means of numerical simulations. First we discuss backscattering effects in zero field relaxation, and the non-monotonic dependence of coercivity on the dissipation strength eta. We then proceed to analyze magnetization reversal by a field pulse of a given amplitude and duration. Reversals by long-duration pulses are governed by the eta-dependence of the relaxation rate, while reversals by brief, large amplitude field pulses are dominated by backscattering effects. (C) 2004 Elsevier B.V. All rights reserved.