Symmetry properties of 2D magnetic photonic crystals with square lattice

We consider possible magnetic symmetries of 2D square lattices with circular ferrite rods magnetized by a uniform DC magnetic field. These structures can be used as tunable and non-reciprocal photonic crystals. Classification of eigenmodes in such crystals and compatibility relations are defined on the basis of magnetic group theory and the theory of representations. Some general electromagnetic properties of the magnetic crystals such as change in the basic domain of the Brillouin zone, bidirectionality and nonreciprocity, symmetry restrictions for the electromagnetic waves and lifting of eigenwave degeneracies by the DC magnetic field are also discussed.