Surface polaritons on semi-infinite gyromagnetic media

TLDR

Surface polaritons on magnetic media are TE modes with elliptically polarized magnetic fields in the sagittal plane when the propagation wavevector, static magnetization, and surface normal are mutually perpendicular. The paper develops a macroscopic theory of surface polaritons on semi‑infinite magnetic media and discusses their potential experimental observation on ferromagnetic insulators. On ferromagnetic insulators, the surface polaritons show nonreciprocal propagation, a new dispersion branch is identified, and magnon‑type polaritons are absent on ferromagnetic metals.

Abstract

A macroscopic theory of surface polaritons on semi-infinite magnetic media is presented. The general nature of surface polaritons on magnetic media is discussed. In the configuration k, M0, and n mutually perpendicular (where k is the propagation wavevector, M0 is the static magnetization of the medium, and n is the outward normal to the surface), the surface polaritons are TE modes with H elliptically polarized in the sagittal plane. The surface polaritons, which exist on a ferromagnetic insulator, exhibit nonreciprocal propagation characteristics of a medium with gyromagnetic permeability. A new branch of the surface polariton dispersion curve is demonstrated. The corresponding magnon type surface polaritons do not occur on a ferromagnetic metal. The possible experimental observation of the magnon type surface polariton modes on a ferromagnetic insulator is also discussed.