Critical behavior of two-dimensional magnetic lattice gas model

Using Monte Carlo simulations and finite-size scaling, we investigate the critical behavior of two-dimensional magnetic lattice gas at densities ρ = 0.90, 0.95, 1.0. There is a ferromagnetic phase transition at each density. As expected, the critical temperature T _c depends on system density ρ. Unexpectedly, there is a density dependence of the critical exponent of correlation length ν. For densities ρ = 0.90,0.95,1.0, we obtain the inverse of critical exponent 1/ν = 0.835(5), 0.905(5), 1.00(1) respectively. It is found that the ratios of critical exponent β/ν and γ/ν of magnetization and susceptibility are independent of density.