Influence of metal plate on surface magnetostatic modes of magnetic slab

The dispersion relationships for surface magnetostatic modes propagating in a ferrite slab with a conducting plate at a small distance parallel to the surface of the slab have been derived. It is shown that the group velocity of the surface magneto-static mode in this configuration can be both positive and negative, depending on the wavelength of the mode and the distance of the conducting plate from the ferrite surface.