Phase diagram for the striped phase in the two-dimensional dipolar Ising model.

Abstract

Ising models with competing dipolar and ferromagnetic short-range interactions can exhibit a number of ordered domain phases. In the absence of an external magnetic field, the square lattice version of this model exhibits a smectic striped phase at low temperatures. On heating the smectic phase melts to yield an orientationally disordered tetragonal phase. In this paper we investigate the effect of a magnetic field on this transition by means of Monte Carlo simulations. The simulations show that application of a field causes the stripes to break up and the minority spins form elongated islands. The phase boundary of the smectic striped phase is obtained for a particular ratio of exchange constant J to the dipolar interaction strength g. The results are discussed and compared with the predictions of mean field theory and previous simulations on a dipolar lattice gas model on a triangular lattice. \textcopyright{} 1996 The American Physical Society.