Confinement effects in antiferromagnets

Phase equilibrium in confined Ising antiferromagnets was studied as a funct ion of the coupling (v) and a magnetic field (h) at the surfaces, in the pr esence of an external field H. Thr ground-slate properties were calculated exactly for symmetric boundary conditions and nearest-neighbor interactions , and a full zero-temperature phase diagram in the plane v-h was obtained f or films with symmetry-preserving surface orientations. The ground-state an alysis was extended to the H-T plane using a cluster-variation free energy. The study of the finite-T properties las a function of v and h) reveals th e close interdependence between the surface and finite-size effects and, to gether with the ground-state phase diagram, provides an integral picture of the confinement in anisotropic antiferromagnets with surfaces that preserv e the symmetry of the order parameter.