Monte Carlo analysis of the extended Ashkin-Teller model

Monte Carlo simulations are used to analyse the behavior of the extended Ashkin-Teller model in two dimensions from the ratio of the square of the second moment of the order parameter to its fourth moment. The critical surface in three dimensional parameter space is calculated in regions where the Ising transitions are expected. The continuity of the order parameter at the critical surface is verified by a finite size scaling analysis for both ferromagnetic and antiferromagnetic parts of the phase diagram.