Crossover from Ising to mean-field critical behavior in a kinetic Ising model with competing flip and exchange dynamics

A two-dimensional kinetic Ising model evolving by a combination of spin flips at temperature T and spin exchanges which are random and of arbitrary range is investigated. We present a mean-field theory and compare its predictions with Monte Carlo simulations. The results indicate that the equilibrium Ising transition that is present without the spin exchanges turns into a mean-field transition as soon as the spin-exchange rate is different from zero. The crossover from Ising to mean-field critical behavior is characterized by an exponent, Φ ≈ 2, equal to the analogous crossover exponent in equilibrium systems.