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Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets

Abstract

Magnetic skyrmions1,2 are topologically protected spin textures that exhibit fascinating physical behaviours1,2,3,4,5,6 and large potential in highly energy-efficient spintronic device applications7,8,9,10,11,12,13. The main obstacles so far are that skyrmions have been observed in only a few exotic materials and at low temperatures1,2,3,4,6,7,8, and fast current-driven motion of individual skyrmions has not yet been achieved. Here, we report the observation of stable magnetic skyrmions at room temperature in ultrathin transition metal ferromagnets with magnetic transmission soft X-ray microscopy. We demonstrate the ability to generate stable skyrmion lattices and drive trains of individual skyrmions by short current pulses along a magnetic racetrack at speeds exceeding 100 m s−1 as required for applications. Our findings provide experimental evidence of recent predictions10,11,12,13 and open the door to room-temperature skyrmion spintronics in robust thin-film heterostructures.

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Figure 1: Soft X-ray imaging of domain structure.
Figure 2: Spin structure phase diagram.
Figure 3: Skyrmion lattice generation.
Figure 4: Current-driven skyrmion motion.
Figure 5: Skyrmion displacement at high current densities for Pt/Co/Ta and Pt/CoFeB/MgO.

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Acknowledgements

Work at MIT was primarily supported by the US Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) under Award No. DE-SC0012371 (sample fabrication and MTXM and STXM experiments). The operation of the X-ray microscope at the Advanced Light Source was supported by the Director, Office of Science, Office of Basic Energy Sciences, Scientific User Facilities Division, of the US Department of Energy under Contract No. DE-AC02-05-CH11231. M.-Y.I. acknowledges support from the Leading Foreign Research Institute Recruitment Program (Grant No. 2012K1A4A3053565) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (MEST). P.F. acknowledges support from the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the US Department of Energy under Contract No. DE-AC02-05-CH11231 within the Non-Equilibrium Magnetic Materials programme. G.S.D.B. acknowledges support from C-SPIN, one of the six SRC STARnet Centers, sponsored by MARCO and DARPA. M.K. and the group at Mainz acknowledge support by the DFG, the Graduate School of Excellence Materials Science in Mainz (MAINZ, GSC 266), the EU (MASPIC, ERC-2007-StG 208162; WALL, FP7-PEOPLE-2013-ITN 608031; MAGWIRE, FP7-ICT-2009-5), the MOGON (ZDV Mainz computing centre) and the Research Center of Innovative and Emerging Materials at Johannes Gutenberg University (CINEMA). B.K. is grateful for financial support by the Carl-Zeiss-Foundation. K.L. gratefully acknowledges financial support by the Graduate School of Excellence Materials Science in Mainz (MAINZ). S.W. acknowledges support from the Kwanjeong Foundation. L.C. acknowledges support by the NSF Graduate Research Fellowship Program. Measurements were carried out at the MAXYMUS endstation at Helmholtz-Zentrum Berlin. We thank HZB for the allocation of beamtime.

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Contributions

S.W., P.F., M.K. and G.S.D.B. designed and initiated the research. S.W. and I.L. fabricated devices and S.W., I.L., L.C. and P.A. performed the film characterization. L.C. performed MOKE measurements of bubble domain expansion. S.W., M.-Y.I., L.C., M.M., K.L., I.L. and P.F. performed X-ray imaging experiments using MTXM at the Advanced Light Source in Berkeley, California. S.W., K.L., L.C., K.R., A.K., R.M.R. and M.W. conducted STXM experiments at the MAXYMUS beamline at the BESSY II synchrotron in Berlin. K.L., B.K. and M.K. performed and analysed the micromagnetic simulations. M.-A.M. provided technical input on sample design. B.K. derived the effective medium scaling laws and wrote the corresponding section in the Supplementary Information. P.A. and I.L. performed the analytical analysis of domain-spacing data. All authors participated in the discussion and interpreted results. S.W. drafted the manuscript and G.S.D.B. revised it with assistance from P.F. and M.K. All authors commented on the manuscript.

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Correspondence to Mathias Kläui or Geoffrey S. D. Beach.

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The authors declare no competing financial interests.

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Woo, S., Litzius, K., Krüger, B. et al. Observation of room-temperature magnetic skyrmions and their current-driven dynamics in ultrathin metallic ferromagnets. Nature Mater 15, 501–506 (2016). https://doi.org/10.1038/nmat4593

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