ABSTRACT
Gyrotropic is used to indicate materials which are anisotropic and have a strong frequency dependence in one of their constitutive parameters. When subjected to a constant magnetic bias field, both plasmas and ferrites exhibit anisotropic constitutive parameters. For electronic plasmas this anisotropy must be described by using a permittivity tensor in place of the usual scalar permittivity. Each member of this tensor is also very frequency dependent. Like plasmas, ferrites are a class of materials which become anisotropic when subjected to a static magnetic field. Unlike plasmas, which are dispersive even without the biasing field, dispersion in ferrites is coupled with the presence of the biasing field. When this field disappears the permeability is no longer frequency dependent and the only resonances that exist are comparatively weak.
