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.

For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale.

We study propagation of the Gaussian beam of spin waves and its reflection from the edge of thin yttrium-iron-garnet film with in-plane magnetization perpendicular to this edge. We have performed micromagnetic simulations supported by analytical calculations to investigate the influence of the surface magnetic anisotropy present at the film edge on the reflection, especially in the context of the Goos-Hänchen effect. We have shown the appearance of a negative lateral shift between reflected and incident spin wave beams' spots. This shift is particularly sensitive to the surface magnetic anisotropy value and is a result of the Goos-Hänchen shift which is sensitive to the magnitude of the anisotropy and of the bending of the spin wave beam. We have demonstrated that the demagnetizing field provide graded increase of the refractive index for spin waves, which is responsible for the bending.PACS numbers: 75.30.Ds, 75.30.Gw, 75.70.Rf, 75.78.Cd In recent years magnetic nanostructures with controlled magnetization dynamics have been considered as candidates for design of new miniaturized devices with enhanced performance and functionality for various applications, e.g. heat transport, energy conversion, magnetic field sensing, information storage and processing. 1-3 Spin waves (SWs), being propagating collective excitations of the magnetization are also regarded as information carriers, which can be exploited for information processing in devices potentially competitive with standard CMOS systems. 4,5 Thus, understanding of SW properties in nanostructures is crucial in designing magnonic units and this is one of the main goal in the research field called magnonics. 6,7 It is expected that magnonic devices allow energy-efficient processing of information which will combine the advantages of photonics (high frequency and wide band) and electronics (miniaturization) in a single unit. 8 One of the basic phenomena connected with wave propagation is the wave transmission and reflection. [9][10][11] The reflection of SWs is determined by magnetic properties of the film and boundary conditions at the border of the ferromagnetic material. The reflection of SWs has already been investigated in theoretical and experimental papers 10,12 where SWs were treated as plane waves. Use of wave beams, instead of the plane waves or spherical waves, in many cases, can be much more useful and opens new possibilities due to its coherence and low divergence. The known example of the wave beam is a light beam emitted by laser. Usually, its intensity profiles can be described by Gaussian distribution (beams with such property are called Gaussian beams). However, in magnonics the idea of SW beams is unexplored, with only a few theoretical and experimental studies considering formation of SW beams at low frequencies due to the caustic or nonlinear effects. [13][14][15][16][17][18][19] An interesting phenomenon characteristic for the reflection of beam is a possibility for occurrence of a lateral shift of the beam spot along the interface between...