Magnetic polaritons in layer systems

The modes which result from the coupling between the electromagnetic field and a ferromagnetic or antiferromagnetic layer are considered. It is assumed that the electric permittivity and magnetic permeability are the same on both sides of the layer, and that the ordering direction is normal to the layer. For a given frequency, the coupled mode has a much larger wavenumber than a free photon, and for large frequency the asymptotic behaviour is q approximately omega 2 , as is found for a layer of mobile charge. The dispersion relation for systems of coupled layers are found for ferromagnetic layers coupled ferromagnetically, ferromagnetic layers coupled antiferromagnetically (metamagnet) and antiferromagnetic layers coupled antiferromagnetically. In the long wavelength limit, these dispersion relations reduce to those found in a bulk system of appropriate order, ferromagnetic in the first case, antiferromagnetic in the other two cases.