Phase transitions and autocorrelation times in two-dimensional Ising model with dipole interactions

The two-dimensional Ising model with nearest-neighbor ferromagnetic and long-range dipolar interactions exhibits a rich phase diagram The presence of the dipolar interaction changes the ferromagnetic ground state expected for the pure Ising model to a series of striped phases as a function of the interaction strengths. Monte Carlo simulations and histogram reweighting techniques applied to multiple histogiams are performed to identify the critical temperatures for the phase transitions taking place for stripes of width h = 2 on square lattices In particular, we aim to study the intermediate nematic phase, which is observed for large lattice sizes only For these lattice sizes, we calculate the critical temperatures for the striped-nematic and nematic-tetragonal transitions, critical exponents. and the bulk free-energy barrier associated with the coexisting phases We also evaluate the long-term correlations in our time series near the finite-size critical points by studying the integrated autocorrelation time T as a function of the lattice size This allows LIS to infer how severe the critical slowing down for this system with long-range interaction and nearby thermodynamic phase transitions is (C) 2009 Elsevier B.V. All rights reserved