Interfacial effects in spin-wave resonance of iron films grown by molecular beam epitaxy

We report theoretical results for iron films prepared by the molecular beam epitaxy technique which give further evidence for the existence of magnetic parameter variations near the film-substrate interface. The ferromagnetic resonance experiments reported earlier complement recent magnetometer measurements. The calculations consist of determining both volume and surface spin-wave dispersions as a function of various assumed variations of magnetic parameters near the interface. This allowed us to predict the excitation of surface modes in addition to the usual volume spin-wave modes. Experimentally, surface modes are excited for thickness $t>1000$ {} and are displaced about 500-1000 Oe above the main line. In addition, we are able to predict the observed deviation from quadratic behavior for low-order-number spin-wave excitations.