arXiv:0809.2503 · Journal of Physics Conference Series
Monte Carlo studies of the Ising square lattice with competing interactions
Ansgar Kalz, A. Honecker, Sebastian Fuchs, Thomas Pruschke
Abstract
We use improved Monte-Carlo algorithms to study the antiferromagnetic 2D-Ising model with competing interactions J 1 on nearest neighbour and J 2 on next-nearest neighbour bonds. The finite-temperature phase diagram is divided by a critical point at J 2 = J 1 /2 where the groundstate is highly degenerate. To analyse the phase boundaries we look at the speciflc heat and the energy distribution for various ratios of J 2 / 1 . We find a first order transition for small J 2 > J 1 /2 and the transition temperature suppressed to T C = 0 at the critical point.