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

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.

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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.

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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.

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Contributions

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.

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Correspondence to Hyunsoo Yang.

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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.

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Supplementary Information

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

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Shi, S., Liang, S., Zhu, Z. et al. All-electric magnetization switching and Dzyaloshinskii–Moriya interaction in WTe2/ferromagnet heterostructures. Nat. Nanotechnol. 14, 945–949 (2019). https://doi.org/10.1038/s41565-019-0525-8

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