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

¹ Zhejiang University, Zhejiang Institute of Modern Physics - Hangzhou 310027, PRC
² Asia Pacific Center for Theoretical Physics, POSTECH - Pohang 790-784, Korea
³ Center for Simulational Physics, The University of Georgia - Athens, GA 30602, USA

^a zheng@zimp.zju.edu.cn

Received: 21 June 2010
Accepted: 14 October 2010

Abstract

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 χ=χ′−iχ″ exhibits features in agreement with the experiments of ultrathin ferromagnetic and ferroelectric films: the semicircle and straight line in the χ′-χ″ plot are Cole-Cole signatures of relaxation and creep states, respectively. The exponent β describing the creep motion is measured, and an intermediate state between the relaxation and creep states is identified.