PHASE-DIAGRAM FOR THE STRIPED PHASE IN THE 2-DIMENSIONAL DIPOLAR ISING-MODEL

Ising models with competing dipolar and ferromagnetic short-range inte ractions can exhibit a number of ordered domain phases. In the absence of an external magnetic field, the square lattice version of this mod el exhibits a smectic striped phase at low temperatures. On heating th e smectic phase melts to yield an orientationally disordered tetragona l phase. In this paper we investigate the effect of a magnetic field o n this transition by means of Monte Carlo simulations. The simulations show that application of a field causes the stripes to break up and t he minority spins form elongated islands. The phase boundary of the sm ectic striped phase is obtained for a particular ratio of exchange con stant J to the dipolar interaction strength g. The results are discuss ed and compared with the predictions of mean field theory and previous simulations on a dipolar lattice gas model on a triangular lattice.