Propagation of nonreciprocal spin waves in a multilayer magnonic crystal

The possibility of frequency-selective propagation of spin waves in a magnonic microwave guide with a magnonic crystal consisting of two layers with different values of the saturation magnetization in the layers is demonstrated. It is shown that multimode propagation of spin waves can occur inside a two-layer structure in two frequency ranges, while the presence of a magnonic crystal on the surface of the structure leads to the manifestation of a band gap in one of the frequency ranges. At the same time, the process of propagation of a spin-wave signal is accompanied by a strong nonreciprocity, which manifests itself in a change in the amplitude-frequency characteristics when the direction of the external magnetic field is reversed, while the frequency range of the band gap differs depending on the direction of the field. The proposed concept of a two-layer spin-wave waveguide can underlie the manufacture of multichannel filters or magnonic logic devices.