High Quality-factor of Propagating Submicron-Wavelength Magnons

Yttrium iron garnet (YIG) is a well-known material for its exceptionally low magnetic damping, resulting in a very narrow linewidth (< 10 MHz full-width at half maximum, FWHM) of the spatially-uniform ferromagnetic resonance mode (FMR) at GHz frequencies [1]. While the linewidth and magnetic damping associated with FMR have been extensively studied [2], studies of these properties for propagating spin waves have been more scarce [3]. In this study, we observed a very narrow linewidth (several MHz of FWHM), corresponding to a quality factor of an order of 10³, for a spin wave resonance with a 1-μm wavelength in the Damon-Eshbach geometry in a 100 nm-thick YIG film. A ladder-shaped, multi-element antenna with a submicron-scale period was fabricated using e-beam lithography on top of a sputter-grown YIG film. The multi-element part was integrated with the central conductor of a photolithographically fabricated coplanar waveguide for microwave transmission. Due to its high-quality factor and well-defined wave vector, spin wave resonance can serve as a suitable entity for studying microwave photon–propagating magnon coupling (propagating magnon-polariton) in superconducting resonator-YIG waveguide structures and for developing a high-quality magnon resonator for quantum information applications.

References

[1] C. Hauser, et al., Sci. Rep. 6, 20827 (2016).

[2] G. Schmidt, et al., Phys. Status Solidi B 257, 1900644 (2020).

[3] Q.W. Fu, et al., Chin. Phys. Lett. 37, 087503 (2020).