Multi-step topological transitions among meron and skyrmion crystals in a centrosymmetric magnet

H. Yoshimochi; R. Takagi; J. Ju; N. D. Khanh; H. Saito; H. Sagayama; H. Nakao; S. Itoh; Y. Tokura; T. Arima; S. Hayami; T. Nakajima; S. Seki

doi:10.1038/s41567-024-02445-9

arXiv · 2402.13751

Multi-step topological transitions among meron and skyrmion crystals in a centrosymmetric magnet

H. Yoshimochi·R. Takagi·J. Ju·N. D. Khanh·H. Saito·H. Sagayama·H. Nakao·S. Itoh·Y. Tokura·T. Arima·S. Hayami·T. Nakajima·S. Seki

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Abstract

Topological swirling spin textures, such as skyrmions and merons, have recently attracted much attention as a unique building block for high-density magnetic information devices. The controlled transformation among different types of such quasi-particles is an important challenge, while it was previously achieved only in a few non-centrosymmetric systems characterized by Dzyaloshinskii-Moriya interaction. Here, we report an experimental discovery of multi-step topological transitions among a variety of meron and skyrmion crystal states in a centrosymmetric magnet GdRu$_2$Ge$_2$. By performing the detailed magnetic structure analysis based on resonant X-ray and neutron scattering experiments as well as electron transport measurements, we have found that this compound hosts periodic lattice of elliptic skyrmions, meron/anti-meron pairs, and circular skyrmions as a function of external magnetic field. The diameter of these objects is as small as 2.7 nm, which is almost two orders of magnitude smaller than typical non-centrosymmetric magnets. Such an intricate manner of topological magnetic transitions are well reproduced by a theoretical model considering the competition between RKKY interactions at inequivalent wave vectors. The present findings demonstrate that even a simple centrosymmetric magnet with competing interactions can be a promising material platform to realize a richer variety of nanometric magnetic quasi-particles with distinctive symmetry and topology, whose stability may be tunable by various external stimuli.

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H. Yoshimochi, R. Takagi, J. Ju, N. D. Khanh, H. Saito, H. Sagayama, H. Nakao, S. Itoh, Y. Tokura, T. Arima, S. Hayami, T. Nakajima, S. Seki. 2024-02-21. Multi-step topological transitions among meron and skyrmion crystals in a centrosymmetric magnet. https://doi.org/10.1038/s41567-024-02445-9

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