Micromagnetic investigation of spin waves propagation in nanoscale YIG waveguides

Abstract

This work investigates, via micromagnetic modeling, the specific features of magnetostatic wave propagation in nanometer-thick yttrium iron garnet (YIG) waveguides with a periodic system of grooves. It is demonstrated that in narrow waveguides with a width of 1 µm, the confinement of the vertical dimension and the inhomogeneity of the demagnetizing fields lead to the hybridization of surface and volume spin waves, manifesting as a splitting of the width modes into families of modes with distinct cut-off eigenfrequencies.
The groove depth, varied within a range of 10 nm to 50 nm, is established to significantly influence the spectral structure: at shallow depths, primary orders of Bragg resonances are observed, whereas when the depth exceeds 2/5 of the film thickness, the number of pronounced band gaps and local spectral perturbations increases substantially.
An increase in the external magnetic field results in a narrowing of the spin-wave frequency range, a more pronounced suppression of the transmission coefficient in the frequency response, and, at critically high field strengths, a transition of the characteristics toward a dispersionless regime.
A comparative analysis of periodicities of 4 µm and 8 µm reveals that doubling the period enhances the efficiency of band-gap formation and leads to an increase in their total number.
Furthermore, the influence of the ridge-to-groove length ratio a/b – at a fixed period– on the frequency and energy dynamics of the mode system arising from the split width modes is examined.
The obtained results open up avenues for tailoring the modal composition and frequency properties of magnonic crystals through the deliberate variation of geometric parameters and the external magnetic field.

The work was supported by the Russian Science Foundation (Project No. 23-79-30027).

Speaker

Varvara Ochkina
Saratov State University
Russia

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