Gyromagnetic Effects in Two-Layer Ferromagnetic Films With Magnonic Crystals

The results of a study on the influence of magnonic crystal configuration on the formation of band gaps in two-layer ferromagnetic structures based on yttrium iron garnet (YIG) are presented. Numerical modeling of the dispersion characteristics was performed using the finite element method for three configurations of magnonic crystals: located in the layer with higher magnetization, in the layer with lower magnetization, and at the interface between the layers. It is demonstrated that asymmetric placement of the magnonic crystal enables selective frequency control: when the periodic structure is positioned in the layer with higher magnetization, band gaps are efficiently formed in the high-frequency region of the spectrum, whereas placement in the layer with lower magnetization results in band gaps in the low-frequency region. It is established that the width of the band gaps increases monotonically with increasing groove depth of the magnonic crystal, while tuning the structural period allows the formation of a multi-band transmission spectrum. Nonreciprocal spectral characteristics, arising from the localization of spin waves in different layers relative to the periodic structure, are confirmed. The obtained results provide a physical foundation for the development of tunable magnonic filters, multiplexers, and unidirectional waveguides, which is of significant interest for advancing the component base of magnonic logic.