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 rho = 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 rho. Unexpectedly, there is a density dependence of the critical exponent of correlation length v. For densities rho = 0.90, 0.95, 1.0, we obtain the inverse of critical exponent 1/v = 0.835(5), 0.905(5), 1.00(1) respectively. It is found that the ratios of critical exponent beta/v and gamma/v of magnetization and susceptibility are independent of density.