Effects of diffusing impurities on domain growth in the Ising model.

Abstract

We have performed the first simulations of the effects of diffusing impurities on domain growth. These simulations were performed within the framework of a quenched, ferromagnetic Ising model with a nonconserved order parameter. The impurity diffusion was simulated using Kawasaki dynamics. For all impurity concentrations and diffusivities considered, the correlation length (domain size) initially increases with time as ${t}^{1/2}$ and then saturates at a value which is dependent on both the impurity concentration and the diffusivity. For any diffusivity, the final domain size was found to decrease with increasing impurity concentration. For most impurity concentrations, the final domain size was also found to decrease with increasing diffusivity. We find evidence for two modes of domain-edge motion in the presence of diffusing impurities. For large domain-edge velocities, the domain edges effectively bypass impurities. At low velocities, the domain edges can only move by pulling along a cloud of impurities. The concentration of impurities on domain edges in the final configurations is found to increase with increasing impurity concentration and increasing impurity diffusivity. Clustering of impurities was observed during domain growth.