Influence of the intrinsic dynamics of the magnetisation on the hysteresisloop

We present numeric simulations of switching processes in small ferromagneti c particles. The dynamics of these processes and the influence of the dynam ics of the applied and internal fields on the magnetization reversal are st udied. In particular, the derivative in time of the effective fields influe nces the hysteresis of these particles. It is shown that fast switching, as is required in high-speed data storage, reduces the coercive field. A dyna mically corrected Stoner-Wohlfarth dependence of the nucleation field is in troduced for the limit of high-field rates and low damping. Implications of these findings are discussed for both, numerical simulation of hysteretic properties and the interpretation of experimental data. (C) 2000 Elsevier S cience B.V. All rights reserved.