Phase diagram of the Ising square lattice with competing interactions

Abstract

We restudy the phase diagram of the 2D-Ising model with competing interactions J1 on nearest neighbour and J2 on next-nearest neighbour bonds via Monte-Carlo simulations. We present the finite temperature phase diagram and introduce computational methods which allow us to calculate transition temperatures close to the criticalpoint at J2 = J1/2. Further on we investigate the character of the different phase boundariesand find that the transition is weakly first order formoderate J2 > J1/2.