Nonhomogeneous magnetization reversal in 2D Ising clusters

We have performed Monte Carlo simulations on 2D circular Ising clusters, studying the distribution of the magnetization within the cluster as well as the magnetization reversal process when an applied external field is suddenly changed. We have shown that for highly anisotropic systems (the Ising-like limit), the magnetization reversal process is not uniform in a wide range of temperatures. Spins having a lower coordination at cluster edges drive the reversal process, acting as nucleation centers. We have found that there is a connection between the roughness transition temperature and the differences in the time evolution patterns of the magnetization. Our simulations agree with experimental results on magnetization reversal of single domain particles. (C) 1996 American Institute of Physics.