Three-dimensional control and imaging of spin waves in nanostructured thin films

In the field of magnonics, harnessing the third dimension has become one of the most desired capabilities for introducing new functionalities. To this goal, understanding and manipulating spin-waves in three-dimensional nanostructured systems are crucial. Here, we discuss two recent advancements in the field: the imaging of spin waves in 3D using Soft X-Ray Laminography (TR-SoXL) [1], and the three-dimensional control of magnetism in crystalline Yttrium Iron Garnet via direct laser irradiation [3].

The experimental visualization of propagating spin waves in three-dimensions has been elusive, due to the need of combining nanoscale spatial resolution in 3D, and time resolution in the GHz frequency range. We use TR-SoXL, to image in three-dimensions spin waves emitted by nanoscale spin textures and study their propagation in a synthetic antiferromagnets. We reconstruct propagating spin waves in three-dimensions, and map the distribution of the SW modes throughout the volume. We observe complex depth-dependent SW profiles, giving rise to three-dimensional interference patterns.

Then, we introduce a new methodology based on phase nanoengineering [2] for direct three-dimensional nanostructuring of crystalline YIG thin film [3]. We show that by irradiating single-crystal YIG films with a focused UV laser, we drive a giant stable enhancement of the perpendicular magnetic anisotropy, in nanoscale regions confined in three-dimensions and whose extension within the volume of the system can be finely controlled. By harnessing these three-dimensional anisotropy profiles, we demonstrate a fine tuning of the spin-wave band structure, and spatial localization of the spin-wave modes within the volume, realizing proof-of-principle magnonic materials and magnonic crystals.



[1] Girardi et al. Nat. Commun. 15, 3057 (2024).

[2] V. Levati, et al., Adv. Mater. Technol, 8, 2300166 (2023).

[3] V. Levati, et al., arXiv:2409.17722 (2024).