X-ray anatomy of a 3D skyrmion

Magnetic Skyrmions are topological spin textures, which have so far been treated as 2D objects. Although this approach has provided an enormous insight into their properties, behavior, and functionality, specifically towards the exploration of magnetic Skyrmions in future spintronics applications, in real systems with a finite thickness larger than the magnetic exchange length, the details of the spin texture extending into the third dimension cannot be neglected. Recent advances in synthesis methods allow for a highly precise engineering of materials that extend into the third dimension, and therefore a fundamental understanding of the full 3D spin texture is not only required, but opens opportunities to explore and tailor 3D topological spintronic devices with enhanced functionalities that cannot be achieved in two dimensions [1]. Examples of novel 3D spin textures include Skyrmion tubes [2,3], Hopfions [4,5], torons, cocoons, and vortex rings [6].

Using soft x-ray laminography we have reconstructed with about 20 nm spatial (voxel) size the full three-dimensional spin texture of a Skyrmion in an 800 nm diameter and 95 nm thin disk patterned from a 30\times[Ir/Co/Pt] multilayered film structure [7]. A quantitative analysis finds that the evolution of the radial profile of the topological skyrmion number is non-uniform across the thickness of the disk. Estimates of the local micromagnetic energy densities suggest that the changes in topological profile are related to non-uniform competing energetic interactions. Theoretical calculations and micromagnetic simulations are consistent with the experimental findings.

Our results provide the foundation for nanoscale magnetic metrology for future tailored spintronics devices using topology as a design parameter.



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[2] M. T. Birch et al., Nat Commun, 11 1726 (2020)

[3] D. Wolf et al., Nat Nanotechnol, 17 250 (2022)

[4] N. Kent et al., Nat Commun, 12, 1562 (2021)

[5] F. Zheng, et al Nature 623, 718–723 (2023)

[6] C. Donnelly et al., Nat Phys, 17 316 (2021)

[7] D. Raftrey et al, Sci Adv 10, eadp8615 (2024)