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Direct observation of the skyrmion Hall effect

Abstract

The well-known Hall effect describes the transverse deflection of charged particles (electrons/holes) as a result of the Lorentz force. Similarly, it is intriguing to examine if quasi-particles without an electric charge, but with a topological charge, show related transverse motion. Magnetic skyrmions with a well-defined spin texture with a unit topological charge serve as good candidates to test this hypothesis. In spite of the recent progress made on investigating magnetic skyrmions, direct observation of the skyrmion Hall effect has remained elusive. Here, by using a current-induced spin Hall spin torque, we experimentally demonstrate the skyrmion Hall effect, and the resultant skyrmion accumulation, by driving skyrmions from the creep-motion regime (where their dynamics are influenced by pinning defects) into the steady-flow-motion regime. The experimental observation of transverse transport of skyrmions due to topological charge may potentially create many exciting opportunities, such as topological selection.

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Figure 1: Schematic of Hall effects for electronic and topological charges.
Figure 2: MOKE microscopy images of pulse current-driven skyrmion motion.
Figure 3: Phase diagram of current-driven skyrmion motion.
Figure 4: Transport features of skyrmions along the device edge.
Figure 5: Accumulation of skyrmions at the device edge.

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Acknowledgements

Work carried out at the Argonne National Laboratory including lithographic processing and MOKE imaging was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. Lithography was carried out at the Center for Nanoscale Materials, which is supported by the DOE, Office of Science, Basic Energy Sciences under Contract No. DE-AC02-06CH11357. W.J. was partially supported by the 1000-Youth Talent Program of China, and National Key Research Plan of China under contract number 2016YFA0302300. Thin film growth performed at UCLA was partially supported by the NSF Nanosystems Engineering Research Center for Translational Applications of Nanoscale Multiferroic Systems (TANMS). Y.Z. acknowledges support by the National Natural Science Foundation of China (Project No. 1157040329), Shenzhen Fundamental Research Fund under Grant No. JCYJ20160331164412545. X.Z. was supported by JSPS RONPAKU (Dissertation Ph.D.) Program. Work at Bryn Mawr College is supported by NSF CAREER award (No. 1053854). The authors wish to thank C. Reichhardt for insightful discussions.

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W.J., A.H. and S.G.E.t.V. conceived and designed the experiments. G.Y. and K.L.W. fabricated the thin film. W.J., W.Z., X.W., M.B.J. and J.E.P., performed lithographic processing. X.Z., Y.Z. and O.H. performed micromagnetic simulation. W.J., X.W. and X.C. performed MOKE experiments and data analysis. W.J., A.H. and S.G.E.t.V. wrote the manuscript. All authors commented on the manuscript.

Corresponding authors

Correspondence to Wanjun Jiang, Axel Hoffmann or Suzanne G. E. te Velthuis.

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The authors declare no competing financial interests.

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Jiang, W., Zhang, X., Yu, G. et al. Direct observation of the skyrmion Hall effect. Nature Phys 13, 162–169 (2017). https://doi.org/10.1038/nphys3883

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