Imaging magnetic skyrmion tubes Magnetic skyrmions are nano-sized FIGURE 1 particles found in chiral magnetic materials. Typically they are envisaged as two dimensional objects, but in reality they have a vertical, tube-like structure. This three dimensional structure has not previously been observed due to the limitations of typical magnetic imaging techniques. In this work, by exploiting the advantages of magnetic x-ray imaging, the tube-like structure of skyrmion tubes was observed for the first time. Magnetic skyrmions have been the focus of intense research due to their potential applications in future spintronic devices [1,2]. To ensure that any encoded skyrmion data survives, the FIGURE 2 stability of the skyrmions are vital. This stability is governed by the formation and annihilation dynamics of the skyrmion tubes. The extended tube-like structure of a skyrmion holds the key to these dynamics: a skyrmion tube is destroyed by breaking into parts, leading to the creation of magnetic singularities known as Bloch points [3]. The subsequent motion of these Bloch points unwinds the skyrmion tube along its length, as illustrated in Fig. 1. In work recently published in Nature Communications, we employed magnetic x-ray imaging methods to catch the first glimpse of these dynamics in real-space. HOLOGRAPHIC IMAGING A thin lamella of FeGe, a well-known skyrmion material, was prepared using a focussed ion beam, and placed over an aperture in a gold-coated silicon nitride membrane. In such a lamella sample, various chiral spin textures can be realised. At low applied magnetic fields, the helical state is stabilised, as illustrated in Fig. 2a. When applying an out-of-plane magnetic field, a hexagonal skyrmion lattice is formed, shown in Fig. 2b. Finally, when applying an in-plane magnetic field, one anticipates In order to convert the reciprocal space diffraction pattern into the formation of the conical state, depicted in Fig. 2c. a real-space image, one must perform a Fourier transform. Due At the SEXTANTS beamline at SOLEIL, we utilised coherent to the loss of the phase information when measuring diffraction circularly polarised soft x-rays with an energy tuned to the intendity, typically such a direct reconstruction is not possible. Fe L edge (/home/webapps/asp_fr/data/asp/publications/synchrotron-soleil/synchrotron-soleil-2020/soleil-highlights-2020-hd-ss-tc705 eV), allowing for magnetic contrast. By3 However, utilising the holographic method, it is possible to encode directing the x-ray beam through the lamella sample under and recover this phase information [4]. Therefore, our samples various temperature and applied magnetic field conditions, included a small reference slit neighbouring the FeGe lamella, small angle x-ray scattering patterns corresponding to each resulting in the vertical line of diffraction on the CCD in Fig. 2d-f. magnetic structure were measured using a CCD camera, as shown in Fig. 2d-f. 24