Monte Carlo simulations on a triangular ising antiferromagnet with nearest and next-nearest interactions

Monte Carlo (MC) simulations on the triangular Ising antiferromagnet with antiferromagnetic next-nearest neiGhbor interaction points out the existence of a first order phase transition between the low temperature two-sublattice antiferromagnetic phase and the high temperature paramagnetic phase. This scenario differs from that observed when the next-nearest neighbor interaction is ferromagnetic, where a Berezinskii-Kosterlitz-Thouless phase occurs at intermediate temperature between the three- sublattice ferrimagnetic phase at low temperature and the paramagnetic phase at high temperature.