Magnon focusing in crystals with alpha-iron structure

The features of the propagation of spin waves (magnons) in crystals with the alpha-iron structure are studied within the framework of a model that takes into account the interaction of an atom with the atoms of the first and second coordination spheres in a layer of a cubic body-centered crystal lattice. It is shown that there is no magnon focusing in long-wave approximation, as for short waves in case of no external constant magnetic field, a focusing effect is observed. The features of focusing are considered with a negative interaction parameter with neighbors.