Direct imaging of an inhomogeneous electric current distribution using the trajectory of magnetic half-skyrmions

Abstract
The direct imaging of current density vector distributions in thin films has remained a daring challenge. Here, we report that an inhomogeneous current distribution can be mapped directly by the trajectories of magnetic half-skyrmions driven by an electrical current in Pt/Co/Ta trilayer, using polar magneto-optical Kerr microscopy. The half-skyrmion carries a topological charge of 0.5 due to the presence of Dzyaloshinskii-Moriya interaction, which leads to the half-skyrmion Hall effect. The Hall angle of half-skyrmions is independent of current density and can be reduced to as small as 4° by tuning the thickness of the Co layer. The Hall angle is so small that the elongation path of half-skyrmion approximately delineates the invisible current flow as demonstrated in both a continuous film and a curved track. Our work provides a practical technique to directly map inhomogeneous current distribution even in complex geometries for both fundamental research and industrial applications.

Citation
Zhang, S., Zhang, X., Zhang, J., Ganguly, A., Xia, J., Wen, Y., … Zhang, X.-X. (2020). Direct imaging of an inhomogeneous electric current distribution using the trajectory of magnetic half-skyrmions. Science Advances, 6(6), eaay1876. doi:10.1126/sciadv.aay1876

Acknowledgements
This publication is based on research supported by the King Abdullah University of Science and Technology (KAUST), Office of Sponsored Research (OSR), under award nos. OSR-2016-CRG5-2977, OSR-2017-CRG6-3427, and CRF-2015-SENSORS-2708. X.Z. acknowledges the support by the Presidential Postdoctoral Fellowship of The Chinese University of Hong Kong, Shenzhen (CUHKSZ). Y.Z. acknowledges the support by the President’s Fund of CUHKSZ, Longgang Key Laboratory of Applied Spintronics, National Natural Science Foundation of China (grant no. 11574137), and Shenzhen Fundamental Research Fund (grant nos. JCYJ20160331164412545 and JCYJ20170410171958839). W.W. acknowledge financial support by the National Key R&D Program of China (no. 2017YFA0303202). Author contributions: S.Z. and X.-X.Z. conceived and coordinated the project and analyzed the data. X.Z., J.X., and Y.Z. developed the theoretical model. Y.W. and S.Z. fabricated the samples, and S.Z. performed the MOKE measurements. S.Z., X.Z., and X.-X.Z. wrote the manuscript. The study was supervised by X.-X.Z. All authors contributed to the discussion and preparation of the manuscript. Competing interests: The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. Additional data related to this paper may be requested from the authors.

Publisher
American Association for the Advancement of Science (AAAS)

Journal
Science Advances

DOI
10.1126/sciadv.aay1876

Additional Links
https://advances.sciencemag.org/lookup/doi/10.1126/sciadv.aay1876https://advances.sciencemag.org/content/advances/6/6/eaay1876.full.pdf

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