Localized magnetic polaritons in antiferromagnetic superlattice with impurity

The dispersion relation for magnetic polaritons localized at the antiferromagnetic impurity film in the antiferromagnetic superlattice (antiferromagnetic/nonmagnetic or antiferromagnetic/antiferromagnetic) are derived in the effective -medium approximation and calculations are performed for the properties of long-wavelength electromagnetic modes. In such systems one finds both surface polaritons which are localized near the surface and guided modes where excitations have a standing-wave -like character and the impurity region acts as a waveguide, because of the magnetic polaritons propagating freely over the impurity layer and dampen in the perpendicular direction on either sides of this region. We assume an external magnetic field parallel to the magnetization and the film interfaces. The dispersion curves and frequency region of the existence of the surface-guided modes of the magnetic polaritons localized at the impurity layer of the antiferromagnetic superlattice are investigated for two values of the external magnetic field: H=0 and H=0.3T.