PROPERTIES OF STANDING SPIN-WAVES IN A THIN-FILM OF FIELD-INDUCED METAMAGNET WITH MODIFIED SURFACE EXCHANGE INTERACTIONS .1. EIGENVALUE PROBLEM AND STABILITY CONDITIONS

Properties of surface spin waves are studied in a thin film of the fie ld-induced metamagnet which consists of ferromagnetically ordered laye rs parallel to the (001) plane, with intralayer ferromagnetic exchange coupling, interlayer antiferromagnetic exchange coupling as well as a strong three-ion anisotropy. A special Rutherford mathematical proced ure for the description of the surface properties of finite crystal st ructures is generalized and applied to solve the eigenvalue problem fo r standing spin waves existing in the paramagnetic phase of the metama gnet at low temperatures. Also, by allowing the surface exchange param eters to deviate from the bulk values the stability conditions for the system are taken under theoretical discussion.