SPIN-WAVES IN THE SEMIINFINITE FEBR2 FIELD-INDUCED METAMAGNET

Properties of surface spin waves are studied in the FeBr2 field-induce d metamagnet that consists of ferromagnetically ordered layers , with intralayer nearest-neighbour ferromagnetic exchange coupling, intralay er next-nearest-neighbour antiferromagnetic exchange coupling and inte rlayer antiferromagnetic exchange coupling as well as a strong three-i on anisotropy. Surface spin-wave modes are calculated for the (001) su rface and for the paramagnetic phase at low temperatures. By allowing the surface exchange parameters to deviate from the bulk values, full richness of the surface spini-wave spectra is displayed. The problem o f the stability of the ground state of the system is also discussed.