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Room-temperature antiskyrmions and sawtooth surface textures in a non-centrosymmetric magnet with S4 symmetry

Abstract

Topological spin textures have attracted much attention both for fundamental physics and spintronics applications. Among them, antiskyrmions possess a unique spin configuration with Bloch-type and Néel-type domain walls owing to anisotropic Dzyaloshinskii–Moriya interaction in the non-centrosymmetric crystal structure. However, antiskyrmions have thus far only been observed in a few Heusler compounds with D2d symmetry. Here we report a new material, Fe1.9Ni0.9Pd0.2P, in a different symmetry class (S4), in which antiskyrmions exist over a wide temperature range that includes room temperature, and transform into skyrmions on changing magnetic field and lamella thickness. The periodicity of magnetic textures greatly depends on the crystal thickness, and domains with anisotropic sawtooth fractals were observed at the surface of thick crystals and attributed to the interplay between the dipolar interaction and the Dzyaloshinskii–Moriya interaction as governed by crystal symmetry. Our findings provide an arena in which to study antiskyrmions, and should stimulate further research on topological spin textures and their applications.

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Fig. 1: Antiskyrmions and basic properties of Fe1.9Ni0.9Pd0.2P.
Fig. 2: Magnetic textures in a lamella with a thickness t ≈ 130 nm.
Fig. 3: Lamella-thickness-dependent transformation between skyrmions and antiskyrmions.
Fig. 4: Thickness evolution of topological spin textures.

Data availability

All the data presented in the article and Supplementary Information are available from the corresponding authors upon reasonable request.

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Acknowledgements

We thank N. Nagaosa, W. Koshibae, Y. Tokunaga and T. Arima for fruitful discussions. We also thank F. S. Yasin for technical support for the DPC-STEM measurement and K. Nakajima for technical support for the preparation of the FIB sample. This work was supported by JSPS Grant-in-Aids for Scientific Research (grant numbers 17K18355, 18H05225, 19H00660 and 20K15164), JST CREST (grant numbers JPMJCR1874 and JPMJCR20T1) and the Humboldt/JSPS International Research Fellow Programme (grant number 19F19815).

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Contributions

K.K., X.Y., Y. Tokura and Y. Taguchi jointly conceived the project. K.K. synthesized the bulk crystals and performed magnetization measurements. L.P. fabricated the FIB samples and performed the LTEM and DPC-STEM measurements. MFM measurements were performed by K.K. with the support of F.K. J.M. theoretically considered the experimental results and performed micromagnetic simulations. The results were discussed and interpreted by all the authors.

Corresponding authors

Correspondence to Kosuke Karube or Yasujiro Taguchi.

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The authors declare no competing interests.

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Peer review information Nature Materials thanks the anonymous reviewers for their contribution to the peer review of this work.

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Extended data

Extended Data Fig. 1 Micromagnetic simulations of the sawtooth magnetic texture.

The panels show the magnetization in various layers at different depth of a film as obtained from a three-dimensional micromagnetic simulation. The simulated sample measures 1.6 µm × 0.8 µm × 5.3 µm where periodic boundary conditions are applied in the x–y-plane to mimic an extended plate. The colour encodes the direction of the magnetization in the plane and black/white encodes the out-of-plane component, as indicated by the square-shaped antiskyrmion on the bottom right panel, which also sketches the DMI-preferred helicities. In addition, small arrows also show the direction of the in-plane components of the magnetization.

Supplementary information

Supplementary Information

Supplementary Notes 1–10, Figs. 1–7, Tables 1 and 2, and references 1–19.

Supplementary Video 1

Field-induced transformation from antiskyrmions to skyrmions.

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Karube, K., Peng, L., Masell, J. et al. Room-temperature antiskyrmions and sawtooth surface textures in a non-centrosymmetric magnet with S4 symmetry. Nat. Mater. 20, 335–340 (2021). https://doi.org/10.1038/s41563-020-00898-w

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