Monte Carlo Simulation of Disordered 2-Dimensional Ising Systems

Abstract

We report extensive Monte Carlo simulations of the site-disordered 2-dimensional Ising system. For concentrations between p = 0.6 and p = 1.0 (pc = 0.59) we have studied the magnetic and caloric properties as well as the cumulants of the magnetization distribution in the critical region. We have found that disorder induces a strong increase of γeff (γmax = 2.16 for p = 0.7) in the usual experimental temperature range (T - Tc)/Tc = 10-2 ÷ 100. Asymptotically near Tc, γ approaches the theoretical value γ = 1.75 independent of the concentration. We propose a model of weakly coupled compact clusters of spins to describe this crossover behaviour of disordered spin systems.