[Truncated abstract] Polaritons are shown to be influenced by magnetoelectric coupling in a semi-infinite multiferroic material. The magnetoelectric coupling is considered as PML-type which allows a small uniform canting in the magnetic sub-lattices, resulting in a weak ferromagnetism. In this type of coupling, the electric polarisation P, the weak ferromagnetism M, and the antiferromagnetic vector L are perpendicular to each other. The case of transverse electric (TE) and transverse magnetic (TM) polarization are obtained when the electric polarisation P and the weak ferromagnetism M are directed in the plane parallel to the surface while the antiferromagnet vector L is directed out of the plane, perpendicular to the surface. Using parameters appropriate for BaMnF4, Maxwell equations are solved to obtain dispersion relations for bulk and surface modes. It is shown that TE surface polaritons are non-reciprocal, such as ω(k) 6= ω(k), where ω is the frequency and k is the propagation vector. It is also shown that the non-reciprocity can be controlled by an applied electric field. The magnetoelectric interaction also gives rise to “leaky” surface modes in the case of TM polarisation, i.e. pseudosurface waves that exist in the pass band, which dissipate energy into the bulk of material.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2012|