Features of nonreciprocal propagation of spin waves in a magnon crystal structure based on a bilayer film of yttrium-iron garnet with partial metallization

This study investigates the spin wave spectra features in a waveguiding structure that is based on a two-layer film. The film has metal strips periodically located on one of its surfaces, forming a magnon crystal (MC). The structure is used to realize the mode of spin wave propagation in two frequency ranges for a selected value of the magnetic field. The article presents a study on the dispersion characteristics of spin waves using the finite element method. It demonstrates the formation of forbidden zones in the high-frequency range of the spectrum. By changing the configuration and location of metal strips on one side of the film, the width and position of the forbidden zones in the spectrum can be controlled. Additionally, the study shows that the properties of nonreciprocity of spin waves can be altered by changing the direction of propagation. The concept proposes a two-layer magnon-crystal structure for designing functional magnonics devices that support frequency-selective multiband modes of operation.