THE INFLUENCE OF EXCHANGE INTERACTIONS ON SURFACE SPIN-WAVES IN A SEMIINFINITE FEBR2 FIELD-INDUCED METAMAGNET

Properties of surface spin waves are studied in an FeBr2 field-induced metamagnet that consists of ferromagnetically ordered layers, with in tralayer nearest-neighbour ferromagnetic exchange coupling, intralayer next-nearest-neighbour antiferromagnetic exchange coupling and interl ayer antiferromagnetic exchange coupling as well as strong three-ion a nisotrophy. A Green-function method is applied to calculate surface sp in-wave modes for the (001) surface and for the paramagnetic phase at low temperatures. By allowing the surface exchange parameters to devia te from the bulk values, the full richness of the surface spin-wave sp ectra is found. The problem of the stability of the ground state of di e system is also discussed.