Reshetnyak S. Spin-wave optics in essentially inhomogeneous magnetic structures

The processes of reflection, refraction and relaxation of spin waves in essentially inhomogeneous magnetic structures are discussed. The influence of the characteristics of interfaces is explored on reflection processes of surface spin waves in biaxial ferromagnetic media and bulk spin waves in easy-axial antiferromagnetic media, as well as magnetoacoustic waves in uniaxial ferromagnetic media. A refraction index is defined for spin waves propagating in such materials with inhomogeneous distribution of magnetic parameters taking into account the effect of birefringence revealed in these systems. The amplitudes of reflection and transmission are defined for each branch of spin waves taking into account the interface coupling parameter. The influence of damping parameter and characteristics of interfaces between layers is studied on a spin wave amplitude of reflection from finite multilayer uniaxial ferromagnetic medium with periodically changing parameters of exchange interaction, magnetic anisotropy and saturation magnetization in the presence of an external homogeneous permanent magnetic field. It is shown that a multilayer structure is an analogue of diffraction lattice for spin waves. Spin wave spectrum is calculated taking into account the contribution of relaxation processes to the spin wave propagation in helicoidal antiferromagnetic media of the type of Cation-Cation-Halogen3. The existence of three spin wave branches is shown, that corresponds to two types of oscillations of magnetic moment. The contribution of relaxation parameters to each of the branches is defined. The refraction indexes are calculated for the corresponding branches.