ORDER, DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM Influence of the Demagnetizing Factor on the Magnetization of an Ensemble of Stoner-Wohlfarth Particles

The influence of the demagnetizing factor on the coercivity of a sample of oriented uniaxial Stoner-Wohlfarth particles is investigated in the approximation of a relaxation model with a selfconsistent determination of the demagnetization field. The demagnetizing field is shown to change the particle magne� tization reversal conditions and to reduce the blocking temperature and coercivity, for which, despite allow� ance for the demagnetizing field, the Neel-Brown relation holds. It is also shown that under the demagne� tizing field, the internal magnetic field in which the particles are located is not stationary but varies with time concordantly with the time sweep of the temperature during magnetization in a constant external field after zerofield cooling (ZFC). Nonstationarity of the internal field in the ZFC regime causes the interval of tran� sition temperatures of the ensemble particles from a blocked state to a state with equilibrium magnetization