Phase diagram of the Ising square lattice with competing interactions

We restudy the phase diagram of the 2D-Ising model with competing interactions J<Subscript>1</Subscript> on nearest neighbour and J<Subscript>2</Subscript> 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 J<Subscript>2</Subscript>=J<Subscript>1</Subscript>/2. Further on we investigate the character of the different phase boundariesand find that the transition is weakly first order formoderate J<Subscript>2</Subscript> > J<Subscript>1</Subscript>/2. Copyright Springer 2008