Surface and bulk TM polaritons in a linear magnetoelectric multiferroic with canted spins

Abstract

We present a theory for surface polaritons on ferroelectric-antiferromagnetic materials with canted spin structure. Canting is assumed to be due to a Dzyaloshinkii-Moriya interaction with the electric polarisation and weak ferromagnetism directed in the plane parallel to the surface. Surface and bulk modes for a semi-infinite film are calculated for the case of transverse magnetic polarisation. Example results are presented using parameters appropriate for BaMnF4. We find that the magnetoelectric interaction gives rise to "leaky" surface modes, i.e. pseudosurface waves that exist in the pass band, and that dissipate energy into the bulk of material. We show that these psuedosurface mode frequencies and properties can be modified by temperature, and application of external electric or magnetic fields.