Researchers used a new 3D X‑ray imaging method to directly map the magnetic patterns called skyrmions inside a thin metal film. For the first time they reconstructed an extended lattice of skyrmion tubes in three dimensions, showing how the spins wind through the full thickness of the sample. The images expose the tube shape, how wide the domain walls are, the sense of the spin winding (helicity), and a measure of three‑dimensional linking called the Hopf index.

The team studied a multilayer film made of iron and gadolinium (Fe/Gd). They imaged a lattice of 24 skyrmions, each carrying topological charge 1. From the 3D reconstruction they measured domain wall widths that vary with depth from about 23 to 40 nanometres. The helicity, which describes the direction of the spin winding, changes with depth from near ±155° at the surfaces to about ±30° in the middle. The arrangement can also be described as a fractional hopfion with a Hopf index near ±0.3 — that is, a partial form of a 3D linked spin structure confined by the film surfaces.

To get these results the authors used vector ptycho‑tomography, a form of coherent diffractive imaging. They recorded X‑ray diffraction patterns while rotating the sample and then used algorithms that are robust to noise to reconstruct the full three‑component magnetic vector field without assuming the sample shape. The experiment used soft X‑rays tuned to magnetic resonances, which gives element‑specific magnetic contrast. More than 10 terabytes of diffraction data were processed to produce a 3D map over a volume larger than 0.4 cubic micrometres, with spatial detail down to the Nyquist limit of about 8 nm.

Why this matters: skyrmions are candidate bits for future magnetic devices because they can be small, stable, and moved by currents. But their behaviour depends on their full 3D structure. Directly seeing the depth dependence, the twisted helicity, and the partial hopfion character gives new, model‑free information that can test simulations and guide device design. The technique also fills a gap in magnetic imaging by combining high resolution, element specificity, and full 3D vector information over an extended area.