• Seng, B.; Schönke, D.; Yeste, J.; Reeve, R.M.; Kerber, N.; Lacour, D.; Bello, J.L.; Bergeard, N.; Kammerbauer, F.; Bhukta, M.; Ferté, T.; Boeglin, C.; Radu, F.; Abrudan, R.; Kachel, T.; Mangin, S.; Hehn, M.; Kläui, M.: Direct Imaging of Chiral Domain Walls and Neel-Type Skyrmionium in Ferrimagnetic Alloys. Advanced Functional Materials 31 (2021), p. 2102307/1-7

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The evolution of chiral spin structures is studied in ferrimagnetic Ta/Ir/Fe/GdFeCo/Pt multilayers as a function of temperature using scanning electron microscopy with polarization analysis (SEMPA). The GdFeCo ferrimagnet exhibits pure right-handed Néel-type domain wall (DW) spin textures over a large temperature range. This indicates the presence of a negative Dzyaloshinskii–Moriya interaction that can originate from both the top Fe/Pt and the Co/Pt interfaces. From measurements of the DW width, as well as complementary magnetic characterization, the exchange stiffness as a function of temperature is ascertained. The exchange stiffness is surprisingly more or less constant, which is explained by theoretical predictions. Beyond single skyrmions, it is identified by direct imaging a pure Néel-type skyrmionium, which due to the expected vanishing skyrmion Hall angle, is a promising topological spin structure to enable applications by next generation of spintronic devices.