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Direct visualization of the three-dimensional shape of skyrmion strings in a noncentrosymmetric magnet

Nature Materials volume 21, pages 181–187 (2022)Cite this article

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Abstract

Magnetic skyrmions are topologically stable swirling spin textures that appear as particle-like objects in two-dimensional (2D) systems. Here, utilizing scalar magnetic X-ray tomography under applied magnetic fields, we report the direct visualization of the three-dimensional (3D) shape of individual skyrmion strings in the room-temperature skyrmion-hosting non-centrosymmetric compound Mn1.4Pt0.9Pd0.1Sn. Through the tomographic reconstruction of the 3D distribution of the [001] magnetization component on the basis of transmission images taken at various angles, we identify a skyrmion string running through the entire thickness of the sample, as well as various defect structures, such as the interrupted and Y-shaped strings. The observed point defect may represent the Bloch point serving as an emergent magnetic monopole, as proposed theoretically. Our tomographic approach with a tunable magnetic field paves the way for direct visualization of the structural dynamics of individual skyrmion strings in 3D space, which will contribute to a better understanding of the creation, annihilation and transfer of these topological objects.

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Fig. 1: Experimental set-up for the scalar magnetic X-ray tomography measurements.
Fig. 2: Magnetic field dependence of XMCD images taken from various angles θ.
Fig. 3: 3D distribution of mc in the skyrmion state obtained by the tomographic reconstruction.
Fig. 4: Reconstructed 3D shape of magnetic skyrmion strings.

Data availability

The data presented in the current study are available from the corresponding authors on reasonable request.

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Acknowledgements

The authors thank L. Peng, X. Z. Yu, N. Nagaosa, T. Arima and A. Kikkawa for enlightening discussions and experimental help. This work was partly supported by Grants-in-Aid for Scientific Research (grant nos. 18H03685, 18K14117, 20H00349, 21H04440, 21H04990, 21K18595, 21K13876) and Grant-in-Aid for Specially Promoted Research (15H05702) from JSPS, PRESTO (grant no. JPMJPR18L5, JPMJPR20B4) and CREST (grant no. JPMJCR1874) from JST, Asahi Glass Foundation and Murata Science Foundation. The synchrotron radiation experiments were performed with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (proposal nos. 2018A2067, 2019B1173 and 2020A2057).

Author information

Authors and Affiliations

  1. Department of Applied Physics, University of Tokyo, Tokyo, Japan

    S. Seki, R. Takagi & Y. Tokura

  2. Institute of Engineering Innovation, University of Tokyo, Tokyo, Japan

    S. Seki & R. Takagi

  3. RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan

    S. Seki, R. Takagi, N. D. Khanh, W. Koshibae & Y. Tokura

  4. PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Japan

    S. Seki & R. Takagi

  5. Japan Synchrotron Radiation Research Institute, Sayo, Japan

    M. Suzuki

  6. School of Engineering, Kwansei Gakuin University, Sanda, Japan

    M. Suzuki

  7. Institute for Chemical Research, Kyoto University, Uji, Japan

    M. Ishibashi, Y. Shiota & T. Ono

  8. Institute of Industrial Science, The University of Tokyo, Tokyo, Japan

    K. Shibata

  9. Tokyo College, University of Tokyo, Tokyo, Japan

    Y. Tokura

  10. Center for Spintronics Research Network, Graduate School of Engineering Science, Osaka University, Toyonaka, Japan

    T. Ono

  11. Center for Spintronics Research Network, Institute for Chemical Research, Kyoto University, Uji, Japan

    T. Ono

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  1. S. Seki
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Contributions

S.S., M.S. and T.O. planned the project. S.S., M.S., M.I. and T.O. performed the scalar magnetic X-ray tomography measurements. R.T., N.D.K., S.S., and Y.T. prepared the samples. M.I. and Y.S. supported the sample characterization. M.S. performed the reconstruction of the scalar magnetic tomography data. S.S. and M.S. analysed the reconstructed images and performed the simulation of tomographic reconstruction. K.S., S.S. and W.K. performed the theoretical calculations. S.S. wrote the manuscript with the support from M.S. and T.O. All authors discussed the results and commented on the manuscript.

Corresponding authors

Correspondence to S. Seki, M. Suzuki or T. Ono.

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The authors declare no competing interests.

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Peer review information Nature Materials thanks Daniel Haskel and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–8 and Notes 1–9.

Supplementary Video 1

A series of XMCD images taken from various angles −90∘ ≤ θ ≤ 90∘ with 5∘ steps. The images taken at selected θ values are shown in Fig. 2 in the main text.

Supplementary Video 2

360∘ view of the experimentally reconstructed mc(r) profiles. The definition of background colour is the same as in Fig. 3b,c in the main text.

Supplementary Video 3

Slice animation of experimentally reconstructed mc(r) profiles, where the slice position is changed as a function of time. The selected slice images are shown in Fig. 3b,c in the main text.

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Seki, S., Suzuki, M., Ishibashi, M. et al. Direct visualization of the three-dimensional shape of skyrmion strings in a noncentrosymmetric magnet. Nat. Mater. 21, 181–187 (2022). https://doi.org/10.1038/s41563-021-01141-w

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