Monte Carlo Study of the Relaxation of the Metastable Phases of a Mixed Ising Ferrimagnet

摘要

We present preliminary results from a Monte Carlo study of the metastable decay of a mixed Ising ferrimagnetic model were spins S that can take values +-1,0 and spins σ that can take values +- 1/2, are on the two sub-lattices of a two dimensional square lattice. We study the relaxation of the system magnetization, starting from an initial metastable configuration in which the magnetization is opposite to the applied field. The relaxation kinetic is simulated by a heat-bath algorithm with random updates. We find that the decay time of the metastable phase depends strongly on the applied field and the size of the system. We have identified three different regimes, depending on the relaxation mechanism by which the system decays: the single-droplet regime for weak fields, and the multidroplet and strong-field regimes. We calculated the cross-over fields between the different regimes. The field and the size dependence of the relaxation process are analyzed in terms of the droplet theory of homogeneous nucleation.