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Fast current-driven domain walls and small skyrmions in a compensated ferrimagnet

Abstract

Spintronics is a research field that aims to understand and control spins on the nanoscale and should enable next-generation data storage and manipulation. One technological and scientific key challenge is to stabilize small spin textures and to move them efficiently with high velocities. For a long time, research focused on ferromagnetic materials, but ferromagnets show fundamental limits for speed and size. Here, we circumvent these limits using compensated ferrimagnets. Using ferrimagnetic Pt/Gd44Co56/TaOx films with a sizeable Dzyaloshinskii–Moriya interaction, we realize a current-driven domain wall motion with a speed of 1.3 km s–1 near the angular momentum compensation temperature (TA) and room-temperature-stable skyrmions with minimum diameters close to 10 nm near the magnetic compensation temperature (TM). Both the size and dynamics of the ferrimagnet are in excellent agreement with a simplified effective ferromagnet theory. Our work shows that high-speed, high-density spintronics devices based on current-driven spin textures can be realized using materials in which TA and TM are close together.

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Fig. 1: Measurement of TA and TM.
Fig. 2: SOTs and DMI.
Fig. 3: Accurate modelling of the temperature and current dependence of vDW.
Fig. 4: Stray-field versus DMI skyrmions.
Fig. 5: Room-temperature-stable ferrimagnetic DMI skyrmions.

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

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Acknowledgements

Work at MIT was supported by the US Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0012371 (X-ray holography materials growth, device fabrication and imaging), and by the DARPA TEE program (current-induced dynamics experiments, modelling and skyrmion size analysis). Devices were fabricated using equipment in the MIT Microsystems Technology Laboratory and the MIT Nanostructures Laboratory. The authors thank L. Liu for use of the ion milling equipment. L.C. acknowledges financial support from the NSF Graduate Research Fellowship Program and from the GEM Consortium. F.B. thanks the DFG for funding under grant no. BU 3297/1-1. The authors thank C. Avci, A.J. Tan and M. Huang for discussions.

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G.S.D.B. proposed and supervised the study. L.C., M.M., F.B. and G.S.D.B. designed the experiments. L.C. and M.M. designed the measurement apparatus and performed domain wall experiments. C.M. and D.B. designed the high-voltage pulse generator. K.U. optimized the GdCo film growth and deposited the samples. L.C. and M.M. performed lithographic steps for the domain wall tracks and F.B., C.M.G., A.C., D.E. and M.S. prepared and characterized the holography samples. F.B., B.P., C.M.G., P.H., A.C. and C.K. performed the X-ray holographic imaging with the assistance of K.B., and with input and supervision from S.E. P.H. reconstructed the holographic images. F.B. performed all the micromagnetic simulations and analytical calculations. All of the authors participated in the discussion and interpreted the results. L.C., F.B., M.M. and G.S.D.B. drafted the manuscript. All authors commented on the manuscript.

Corresponding author

Correspondence to Geoffrey S. D. Beach.

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Supplementary Information

Supplementary Figures 1–11

Supplementary Video 1

Imaging of skyrmions during increasing field sweep depicted in Fig. 4c.

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Caretta, L., Mann, M., Büttner, F. et al. Fast current-driven domain walls and small skyrmions in a compensated ferrimagnet. Nature Nanotech 13, 1154–1160 (2018). https://doi.org/10.1038/s41565-018-0255-3

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