Order of phase transition for systems with multispin interactions: Monte Carlo simulations

A family of two-dimensional spin models with n-spin interactions in one direction and two-spin interactions in the other is studied by Monte Carlo simulations. Our results show that for the case where the variables are of the Ising (q-state Potts, $q>2$) type the transition is of first order for n>nc=3 (n>nc=2) in agreement with previous conjecture.