The effect of thermal activation on the coercivity of domain walls

The effect of temperature is rarely taken into account in micromagnetic cal culations. However, thermal perturbations are known to play an important ro le in magnetization reversal processes. In this article, a micromagnetic mo del that includes thermal perturbations is presented. A stochastic zero-mea n Gaussian field is introduced in the Landau-Lifschitz-Gilbert equation and the corresponding Langevin equation is solved numerically. The model is us ed to study the effect of temperature on the coercivity of domain walls due to exchange and anisotropy wells as well as nonmagnetic inclusions. It is shown that, for exchange and anisotropy interactions, thermal perturbations can lower the critical field for which the wall breaks free from the inclu sion. However, when magnetostatic fields are taken into account, thermal pe rturbations are found to inhibit the unpinning process. This phenomenon see ms to be related to the long-range nature of dipolar interactions. (C) 1999 American Institute of Physics. [S0021-8979(99)52508-5].