Nonreciprocal circular polariser using hexagonal ferrites with planar anisotropy

It is the purpose of this letter to describe a nonreciprocal ferrite quarter waveplate which relies on the planar anisotropy of hexagonal ferrites in a longitudinal d.c. magnetic field. In such a system, the energies of the two normal modes are unequal, and the normal modes are in general elliptically polarised. The boundary conditions of the system are satisfied by adjusting the ellipticity of the two normal modes and the overall length of the device.