Theory of far-infrared attenuated total reflection from surface magnetic polaritons in rare-earth superlattices

Abstract

We present a theory for the attenuated total reflection (ATR) spectra to probe surface magnetic polaritons that propagate in semi-infinite superlattices made up of a rare-earth material intercalated by a nonmagnetic layer. We consider both the spiral and the cone states of the rare-earth constituent, apart from its simple ferromagnetic (antiferromagnetic) alignment due to the nearest (next-nearest) exchange coupling. We use the framework of the effective medium theory to determine the magnetic polariton’s dispersion relation, since it is very suitable to explain experimental observations of excitations in the far-infrared. Numerical results are presented to illustrate the ATR spectra, with emphasis in the surface polariton’s nonreciprocal aspect shown in the cone state of the rare-earth material.