THE DOMAIN-STRUCTURE IN ULTRATHIN MAGNETIC-FILMS

We discuss the domain structure in ultrathin magnetic films (of a few monolayer thickness), where the easy direction of magnetization is perpendicular to the film. We calculate the dependence of the width D of domains on film thickness L within the continuum approximation. Provided that the thickness of the film is large compared with the range of the exchange interactions, r(e), we find that D is proportional to L e(piD0/2L), where D0 is the 'dipolar length'. However, for L < r(e) we obtain a domain size that is linearly proportional to L. We calculate the energies for stripe and check patterns and find that they are extremely close and have the same functional dependence on L.