Aging in a two-dimensional Ising model with dipolar interactions

Aging in a two-dimensional Ising spin model with both ferromagnetic exchange and antiferromagnetic dipolar interactions is established and investigated via Monte Carlo simulations. The behavior of the autocorrelation function C(t,t_w) is analyzed for different values of the temperature, the waiting time t_w and the quotient δ=J₀/J_d, J₀ and J_d being the strength of exchange and dipolar interactions, respectively. Our results show that this nondisordered model presents a slow nonequilibrium dynamics which, depending on the values of δ, is consistent either with a linear scaling t/t_w of the correlation function or with a logaritmic scaling ln(t)/ln(t_w) which is usually associated with activated dynamics scenarios in disordered systems.