Surface spin-flop phases and bulk discommensurations in antiferromagnets

Phase diagrams asa function of anisotropy D and magnetic field H are obtained for discommensurations and surface states for a model antiferromagnet, equivalent to a mean-field approximation, in which H is parallel to the easy axis. The surface spin-flop phase exists for all D. We show that there is a region where the penetration length of the surface spin-flop phase diverges. Introducing a discommensuration of even length then becomes preferable to reconstructing the surface. The results are used to clarify and correct previous studies in which discommensurations have been confused with genuine surface spin-hop states.