SIMULATION OF THE REORIENTATION TRANSITION IN ULTRATHIN MAGNETIC-FILMS WITH STRIPED AND TETRAGONAL PHASES

We show, using a model of an ultrathin magnetic film, that when the di pole-dipole and exchange interactions are of comparable strength there exists a reorientation transition from a planar ferromagnetic phase a t bw temperature to either an orientationally ordered striped phase or a tetragonal phase at higher temperature, Which of these transitions occurs depends on the relative strength of the magnetic surface anisot ropy. The phase diagram, as found from extensive Monte Carlo simulatio n, is determined as a function of temperature and magnetic surface ani sotropy.