On the phase diagram of the 2d Ising model with frustrating dipole interaction

Due to intrinsic frustrations of interaction, the 2d Ising model with competing ferromagnetic short-range nearest-neighbour and antiferromagnetic long-range dipole interactions possesses a rich phase diagram. The order of the phase transition from the striped h=1 phase to the tetragonal phase that is observed in this model has been a subject of recent controversy. We address this question using the partition function density analysis in the complex temperature plane. Our results support the second-order phase transition scenario. To measure the strength of the phase transition we calculate the values of the specific heat critical exponent $\alpha$. Along with the space dimension D, it appears to depend on the ratio of strength of the short-range and long-range interactions.