Abstract
We study the ground state of a classical X-Y model with p ⩾ 3-fold spin anisotropy D in a uniform external field, H. An interface is introduced into the system by a suitable choice of boundary 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 transitions end in a sequence of critical end points.