In this paper we outline a new direction in the area of photonic crystals (PCs), or photonic band gap materials, i.e. one-, two-, or three-dimensional superstructures with periods that are comparable with the wavelengths of electromagnetic radiation. The main (and principal) characteristic of this new class of PCs is the presence of magnetically ordered components (or external magnetic field). The linear and nonlinear optical properties of such magnetic PCs are discussed.

Electromagnetic wave propagation in a one-dimensional magnetic photonic crystal (MPC) made of bigyrotropic magnetic yttrium–iron garnet and nonmagnetic gadolinium–gallium garnet is theoretically investigated using the 4×4 transfer matrix method. Band gaps in the electromagnetic spectrum are numerically obtained and appear to depend on the helicity and direction of light propagation through the MPC.

The transmission characteristics of a two-defect magnetic photonic crystal ͑MPC͒ with respect to oblique incident light are investigated, both for circularly polarized as well as linearly polarized light. It is shown that the transmittivity and Faraday rotation angle are very sensitive to a change of light propagation direction inside the MPC. Possible applications of MPCs as Faraday rotators are discussed.