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Surface and bulk polaritons in a linear magnetoelectric multiferroic with canted spins: Transverse Electric polarisation

Some magnetoelectric multiferroics have a canted spin structure that can be described by a Dzyaloshinkii-Moriya coupling. We calculate properties and features expected for surface and bulk magnon polaritons in such media with a linear magnetoelectric interaction for the case of transverse electric polarisation. The dielectric polarisation and magnetisation of weak ferromagnetism are constrained to lie in the plane parallel to the surface. We examine a geometry with the polarisation oriented in the film plane and present numerical results for the transverse electric polarisation. Particular attention is given to non-reciprocal surface modes, which exist in frequency between two bulk bands, and show how these modes can be modified by external magnetic field. Results for attenuated total reflection are presented, and discussed in relation to nonreciprocity. Example results are calculated for the canted antiferromagnet BaMnF4.