All-electric magnetization switching and Dzyaloshinskii–Moriya interaction in WTe2/ferromagnet heterostructures

Article metrics

Abstract

All-electric magnetization manipulation at low power is a prerequisite for a wide adoption of spintronic devices. Materials such as heavy metals1,2,3 or topological insulators4,5 provide good charge-to-spin conversion efficiencies. They enable magnetization switching in heterostructures with either metallic ferromagnets or with magnetic insulators. Recent work suggests a pronounced Edelstein effect in Weyl semimetals due to their non-trivial band structure6,7; the Edelstein effect can be one order of magnitude stronger than it is in topological insulators or Rashba systems. Furthermore, the strong intrinsic spin Hall effect from the bulk states in Weyl semimetals can contribute to the spin current generation8. The Td phase of the Weyl semimetal WTe2 (WTe2 hereafter) possesses strong spin–orbit coupling6,9 and non-trivial band structures10 with a large spin polarization protected by time-reversal symmetry in both the surface and bulk states9,10,11. Atomically flat surfaces, which can be produced with high quality12, facilitate spintronic device applications. Here, we use WTe2 as a spin current source in WTe2/Ni81Fe19 (Py) heterostructures. We report field-free current-induced magnetization switching at room temperature. A charge current density of ~2.96 × 105 A cm−2 suffices to switch the magnetization of the Py layer. With the charge current along the b axis of the WTe2 layer, the thickness-dependent charge-to-spin conversion efficiency reaches 0.51 at 6–7 GHz. At the WTe2/Py interface, a Dzyaloshinskii–Moriya interaction (DMI) with a DMI constant of −1.78 ± 0.06 mJ m−2 induces chiral domain wall tilting. Our study demonstrates the capability of WTe2 to efficiently manipulate magnetization and sheds light on the role of the interface in Weyl semimetal/magnet heterostructures.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

Fig. 1: Raman measurements and MOKE measurements.
Fig. 2: ST-FMR measurements.
Fig. 3: Spin-orbit-torque-driven magnetization switching measurements.
Fig. 4: DW tilting induced by the interfacial DMI in WTe2/Py.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

References

  1. 1.

    Miron, I. M. et al. Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection. Nature 476, 189–193 (2011).

  2. 2.

    Liu, L. et al. Spin-torque switching with the giant spin Hall effect of tantalum. Science 336, 555–558 (2012).

  3. 3.

    Avci, C. O. et al. Current-induced switching in a magnetic insulator. Nat. Mater. 16, 309–314 (2017).

  4. 4.

    Wang, Y. et al. Room temperature magnetization switching in topological insulator–ferromagnet heterostructures by spin–orbit torques. Nat. Commun. 8, 1364 (2017).

  5. 5.

    Han, J. et al. Room-temperature spin–orbit torque switching induced by a topological insulator. Phys. Rev. Lett. 119, 077702 (2017).

  6. 6.

    Li, Q. et al. Interference evidence for Rashba-type spin splitting on a semimetallic WTe2 surface. Phys. Rev. B 94, 115419 (2016).

  7. 7.

    Johansson, A., Henk, J. & Mertig, I. Edelstein effect in Weyl semimetals. Phys. Rev. B 97, 085417 (2018).

  8. 8.

    Sun, Y., Zhang, Y., Felser, C. & Yan, B. Strong intrinsic spin Hall effect in the TaAs family of Weyl semimetals. Phys. Rev. Lett. 117, 146403 (2016).

  9. 9.

    Jiang, J. et al. Signature of strong spin–orbital coupling in the large nonsaturating magnetoresistance material WTe2. Phys. Rev. Lett. 115, 166601 (2015).

  10. 10.

    Feng, B. et al. Spin texture in type-II Weyl semimetal WTe2. Phys. Rev. B 94, 195134 (2016).

  11. 11.

    Soluyanov, A. A. et al. Type-II Weyl semimetals. Nature 527, 495–498 (2015).

  12. 12.

    Lee, C.-H. et al. Tungsten ditelluride: a layered semimetal. Sci. Rep. 5, 10013 (2015).

  13. 13.

    Song, Q. et al. The polarization-dependent anisotropic Raman response of few-layer and bulk WTe2 under different excitation wavelengths. RSC Adv. 6, 103830 (2016).

  14. 14.

    Bayreuther, G., Premper, J., Sperl, M. & Sander, D. Uniaxial magnetic anisotropy in Fe/GaAs(001): role of magnetoelastic interactions. Phys. Rev. B 86, 054418 (2012).

  15. 15.

    Liu, L., Moriyama, T., Ralph, D. & Buhrman, R. Spin-torque ferromagnetic resonance induced by the spin Hall effect. Phys. Rev. Lett. 106, 036601 (2011).

  16. 16.

    Mellnik, A. et al. Spin-transfer torque generated by a topological insulator. Nature 511, 449–451 (2014).

  17. 17.

    Wang, Y. et al. Topological surface states originated spin–orbit torques in Bi2Se3. Phys. Rev. Lett. 114, 257202 (2015).

  18. 18.

    Das, P. K. et al. Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2. Nat. Commun. 7, 10847 (2016).

  19. 19.

    Slonczewski, J. C. Current-driven excitation of magnetic multilayers. J. Magn. Magn. Mater. 159, L1–L7 (1996).

  20. 20.

    Wang, Z., Li, H., Guo, X., Ho, W. & Xie, M. Growth characteristics of topological insulator Bi2Se3 films on different substrates. J. Cryst. Growth 334, 96–102 (2011).

  21. 21.

    MacNeill, D. et al. Control of spin–orbit torques through crystal symmetry in WTe2/ferromagnet bilayers. Nat. Phys. 13, 300–305 (2017).

  22. 22.

    Shao, Q. et al. Strong Rashba–Edelstein effect-induced spin–orbit torques in monolayer transition metal dichalcogenide/ferromagnet bilayers. Nano Lett. 16, 7514–7520 (2016).

  23. 23.

    Zhang, W. et al. Research update: spin transfer torques in permalloy on monolayer MoS2. APL Mater. 4, 032302 (2016).

  24. 24.

    Guimaraes, M. H., Stiehl, G. M., MacNeill, D., Reynolds, N. D. & Ralph, D. C. Spin–orbit torques in NbSe2/permalloy bilayers. Nano Lett. 18, 1311–1316 (2018).

  25. 25.

    Viret, M., Vanhaverbeke, A., Ott, F. & Jacquinot, J.-F. Current induced pressure on a tilted magnetic domain wall. Phys. Rev. B 72, 140403 (2005).

  26. 26.

    Ryu, K.-S., Thomas, L., Yang, S.-H. & Parkin, S. S. Current induced tilting of domain walls in high velocity motion along perpendicularly magnetized micron-sized Co/Ni/Co racetracks. Appl. Phys. Express 5, 093006 (2012).

  27. 27.

    Boulle, O. et al. Domain wall tilting in the presence of the Dzyaloshinskii–Moriya interaction in out-of-plane magnetized magnetic nanotracks. Phys. Rev. Lett. 111, 217203 (2013).

  28. 28.

    Thiaville, A., Rohart, S., Jué, É., Cros, V. & Fert, A. Dynamics of Dzyaloshinskii domain walls in ultrathin magnetic films. Europhys. Lett. 100, 57002 (2012).

  29. 29.

    Tretiakov, O. A. & Abanov, A. Current driven magnetization dynamics in ferromagnetic nanowires with a Dzyaloshinskii–Moriya interaction. Phys. Rev. Lett. 105, 157201 (2010).

  30. 30.

    Wang, W. et al. Magnon-driven domain-wall motion with the Dzyaloshinskii–Moriya interaction. Phys. Rev. Lett. 114, 087203 (2015).

  31. 31.

    Di, K. et al. Direct observation of the Dzyaloshinskii–Moriya interaction in a Pt/Co/Ni film. Phys. Rev. Lett. 114, 047201 (2015).

  32. 32.

    Belmeguenai, M. et al. Interfacial Dzyaloshinskii–Moriya interaction in perpendicularly magnetized Pt/Co/AlOx ultrathin films measured by Brillouin light spectroscopy. Phys. Rev. B 91, 180405 (2015).

  33. 33.

    Vansteenkiste, A. et al. The design and verification of MuMax3. AIP Adv. 4, 107133 (2014).

Download references

Acknowledgements

This research was supported by the National Research Foundation (NRF), Prime Minister’s Office, Singapore, under its Competitive Research Programme (CRP award no. NRFCRP12-2013-01) and SpOT-LITE programme (A*STAR Grant no. A18A6b0057) through RIE2020 funds from Singapore.

Author information

S.S., S.L. and H.Y. conceived and designed the experiments. S.S. and S.L. performed the device fabrications and measurements. Z.Z. and G.L. calculated the spatial DMI field and performed macrospin simulations. K.C., S.D.P. and S.S. performed the micromagnetic simulations. S.S. and Y.W. prepared the ST-FMR and MOKE set-ups. J.W. and G.E. performed the Raman measurements. Q.W. contributed the materials. S.S. and S.L. analysed the data with the help of Y.W., P.H. and J.Y. S.S., Z.Z., S.D.P. and H.Y. prepared the manuscript. H.Y. supervised the project. All the authors discussed the results and commented on the manuscript.

Correspondence to Hyunsoo Yang.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information: Nature Nanotechnology thanks Can Onur Avci and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary Information

Supplementary Information

Supplementary Figs. 1–19, Supplementary Tables S1 and S2 and Supplementary refs. 1–29.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark