Photon/magnon conversion near a material interface

Direct coupling between electromagnetic waves and spin waves caused by an abrupt discontinuity in material parameters is studied. It is shown that the simultaneous presence of an evanescent and propagating wave can lead to the conversion of electromagnetic power to exchange power. The partial conversion of an electromagnetic wave travelling in air, and incident normally upon a ferromagnet, is analysed in detail for the case when the material is uniformly magnetised to saturation along the direction of propagation.