Relaxation-to-creep transition of domain-wall motion in a two-dimensional random-field Ising model with an ac driving field

Monte Carlo simulations of a two-dimensional, random-field Ising model with an ac driving field are used to study the relaxation-to-creep transition of domain-wall motion at low temperatures. The resultant complex susceptibility chi = chi' - i chi '' exhibits features in agreement with the experiments of ultrathin ferromagnetic and ferroelectric films: the semicircle and straight line in the chi' - chi '' plot are Cole-Cole signatures of relaxation and creep states, respectively. The exponent beta describing the creep motion is measured, and an intermediate state between the relaxation and creep states is identified. Copyright (C) EPLA, 2010