Direct Observation of Propagating Spin Waves in the 2D van der Waals Ferromagnet Fe5GeTe2

Magnetism in reduced dimensionalities is of great fundamental interest while also providing perspectives for applications of materials with novel functionalities. In particular, spin dynamics in two dimensions (2D) have become a focus of recent research. Here, we report the observation of coherent propagating spin-wave dynamics in a similar to 30 nm thick flake of 2D van der Waals ferromagnet Fe5GeTe2 using X-ray microscopy. Both phase and amplitude information were obtained by direct imaging below T-C for frequencies from 2.77 to 3.84 GHz, and the corresponding spin-wave wavelengths were measured to be between 1.5 and 0.5 mu m. Thus, parts of the magnonic dispersion relation were determined despite a relatively high magnetic damping of the material. Numerically solving an analytic multilayer model allowed us to corroborate the experimental dispersion relation and predict the influence of changes in the saturation magnetization or interlayer coupling, which could be exploited in future applications by temperature control or stacking of 2D-heterostructures.

Automated summary

In this study, coherent propagating spin-wave dynamics in a 30 nm thick flake of two-dimensional van der Waals ferromagnet Fe5GeTe2 were observed using X-ray microscopy. Phase and amplitude information were obtained, and parts of the magnonic dispersion relation were determined. The numerical solution of an analytic multilayer model verified the experimental results and predicted the effects of changes in saturation magnetization or interlayer coupling.