Nikolai S. Kiselev
Institute for Advanced Simulation and Peter Grünberg Institute, Forschungsyentrum Jülich, 52425 Jülich Germany
In thin plates of cubic chiral magnets, the skyrmions represent vortex-like spin textures forming strings penetrating through the sample. Short skyrmion strings are typically parallel to each other. Using transmission electron microscopy (TEM), we found that in buck crystals and relatively thick plates of cubic chiral magnets, the skyrmions can form braids — the superstructures of skyrmion strings that wind around one another [1]. The experimental observation of skyrmion braids is supported by comprehensive theoretical analysis, which explains the mechanism of their stability, dependencies on the external field, and the plate thickness. We also provide a reliable approach for creating skyrmion braids composed of an arbitrary number of skyrmion strings in the cluster.
In the second part of my talk, I will talk about stable antiskyrmions in B-20 type FeGe [2]. Earlier it was assumed that the coexistence of statically stable skyrmion and its antiparticle – antiskyrmions in cubic chiral magnets is impossible. The experimental observation of the skyrmion-antiskyrmion pairs production and annihilation in FeGe plates is consistent with the earlier theoretical findings in two-dimensional (2D) systems [3]. Still, it has some essential peculiarities connected with the additional twist of magnetization across the thickness of the plate. Contrary to 2D systems, skyrmion antiskyrmion pairs in FeGe can appear as statically stable configurations [2]. We estimated the antiskyrmion stability range and presented a reliable approach for the nucleation of antiskyrmions in FeGe plates.
We acknowledge financial support from the European Research Council under the European Union's Horizon 2020 Research and Innovation Programme (Grant 856538 - project “3D MAGiC”) and the Deutsche Forschungsgemeinschaft through SPP 2137 “Skyrmionics” Grants KI 2078/1-1 and BL 444/16.
References
[1] F. Zheng et al., Nature Commun. 12, 5316 (2021).[2] F. Zheng et al., Nature Phys. (2022) 18, 863 (2022).
[3] V. M. Kuchkin and N. S. Kiselev Phys. Rev. B 101, 064408 (2020).