Magnons in 3-layer ferromegnetic superlattices

A brief study of bulk and surface mangons in 3-layer Heisenberg ferromagnetic superlattices is presented. Each layer is modelled by a simple-cubic lattice fo spins coupled via nearest-neighbor exchange interactions. The superlattice has a larger periodicity in the direction perpendicular to the slabs and therefore many magnon branches in the folded Brillouin zone. In the gaps existing between these manon branches appear the surface-localized magnons. We give closed-form expressions for bulk and surface magnons in 3-layer superlattices, together with the corresponding dispersion curves for one spectific case. An application is also done for a Fe/Co superlattice. (orig.)