Nonreciprocal spin wave propagation in bilayer magnonic waveguide

Abstract

Here we present the frequency-selective spin-wave propagation in the magnonic waveguide consisting of two layers with different magnetization saturation. We show that the multimode spin-wave propagation can be performed inside the bilayer structure within two separate frequency range. At the same time this process is accompanied by strong nonreciprocity in spin-wave behavior with the relation to direction of the spin-wave propagation and bias magnetic field. Using the microwave spectroscopy we demonstrate the coexistence of two frequency range in the two samples of pure/modified yttrium iron garnet bilayers with the different orientation of layers with the respect of the substrate. Using the numerical model based on the magnetostatic dispersion relation for spin waves in the bilayer the nonreciprocal behavior of spin-waves was elucidated and its properties for the confined magnonic bilayer stripe was obtained. In particular, it was shown that the narrowing of the stripe leads to the pronounced variation of the nonreciprocity effect for the separate modes in the spin-wave spectra. The experimental data are in good agreement with the predicted by the proposed theoretical model. The proposed concept of bilayer spin-wave waveguide can underlie the fabrication of the magnonic interconnection bus with the support of multiple frequency band operational regimes.