THE ROLE OF SPIN ANISOTROPY IN THE UNBINDING OF INTERFACES

We study the ground state of a classical X-Y model with p greater than or equal to 3-fold spin anisotropy D in a uniform external field, H. An interface is introduced into the system by a suitable choice of bou ndary conditions. For large D, as H --> 0, we show using an expansion in D-1 that the interface unbinds from the surface through an infinite series of layering transitions. Numerical work shows that the transit ions end in a sequence of critical end points.