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Symmetry-dependent field-free switching of perpendicular magnetization

Abstract

Modern magnetic-memory technology requires all-electric control of perpendicular magnetization with low energy consumption. While spin–orbit torque (SOT) in heavy metal/ferromagnet (HM/FM) heterostructures1,2,3,4,5 holds promise for applications in magnetic random access memory, until today, it has been limited to the in-plane direction. Such in-plane torque can switch perpendicular magnetization only deterministically with the help of additional symmetry breaking, for example, through the application of an external magnetic field2,4, an interlayer/exchange coupling6,7,8,9 or an asymmetric design10,11,12,13,14. Instead, an out-of-plane SOT15 could directly switch perpendicular magnetization. Here we observe an out-of-plane SOT in an HM/FM bilayer of L11-ordered CuPt/CoPt and demonstrate field-free switching of the perpendicular magnetization of the CoPt layer. The low-symmetry point group (3m1) at the CuPt/CoPt interface gives rise to this spin torque, hereinafter referred to as 3m torque, which strongly depends on the relative orientation of the current flow and the crystal symmetry. We observe a three-fold angular dependence in both the field-free switching and the current-induced out-of-plane effective field. Because of the intrinsic nature of the 3m torque, the field-free switching in CuPt/CoPt shows good endurance in cycling experiments. Experiments involving a wide variety of SOT bilayers with low-symmetry point groups16,17 at the interface may reveal further unconventional spin torques in the future.

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Fig. 1: Crystal structure and symmetry analysis.
Fig. 2: Symmetry-dependent field-free magnetization switching.
Fig. 3: Symmetry dependence of current-induced effective fields.
Fig. 4: Theoretical model for current-induced spin torque in the CuPt/CoPt bilayer.
Fig. 5: Current-induced field-free magnetization switching in CuPt (13 nm)/CoPt (4 nm) pillar sample.

Data availability

The authors declare that the main data supporting the findings of this study are available within the Letter and its Supplementary Information. Extra data are available from the corresponding author upon reasonable request. Source data are provided with this paper.

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).

    CAS  Article  Google Scholar 

  2. 2.

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

    CAS  Article  Google Scholar 

  3. 3.

    Manchon, A. et al. Current-induced spin-orbit torques in ferromagnetic and antiferromagnetic systems. Rev. Mod. Phys. 91, 035004 (2019).

    CAS  Article  Google Scholar 

  4. 4.

    Liu, L., Lee, O. J., Gudmundsen, T. J., Ralph, D. C. & Buhrman, R. A. Current-induced switching of perpendicularly magnetized magnetic layers using spin torque from the spin Hall effect. Phys. Rev. Lett. 109, 096602 (2012).

    Article  Google Scholar 

  5. 5.

    Pai, C. F. et al. Spin transfer torque devices utilizing the giant spin Hall effect of tungsten. Appl. Phys. Lett. 101, 122404 (2012).

    Article  Google Scholar 

  6. 6.

    Lau, Y. C., Betto, D., Rode, K., Coey, J. M. D. & Stamenov, P. Spin–orbit torque switching without an external field using interlayer exchange coupling. Nat. Nanotechnol. 11, 758–762 (2016).

    CAS  Article  Google Scholar 

  7. 7.

    Oh, Y. W. et al. Field-free switching of perpendicular magnetization through spin–orbit torque in antiferromagnet/ferromagnet/oxide structures. Nat. Nanotechnol. 11, 878–884 (2016).

    CAS  Article  Google Scholar 

  8. 8.

    Fukami, S., Zhang, C., DuttaGupta, S., Kurenkov, A. & Ohno, H. Magnetization switching by spin–orbit torque in an antiferromagnet–ferromagnet bilayer system. Nat. Mater. 15, 535–541 (2016).

    CAS  Article  Google Scholar 

  9. 9.

    van den Brink, A. et al. Field-free magnetization reversal by spin-Hall effect and exchange bias. Nat. Commun. 7, 10854 (2016).

    Article  Google Scholar 

  10. 10.

    Yu, G. et al. Switching of perpendicular magnetization by spin–orbit torques in the absence of external magnetic fields. Nat. Nanotechnol. 9, 548–554 (2014).

    CAS  Article  Google Scholar 

  11. 11.

    You, L. et al. Switching of perpendicularly polarized nanomagnets with spin orbit torque without an external magnetic field by engineering a tilted anisotropy. Proc. Natl Acad. Sci. USA 112, 10310–10315 (2015).

    CAS  Article  Google Scholar 

  12. 12.

    Liu, L. et al. Current-induced magnetization switching in all-oxide heterostructures. Nat. Nanotechnol. 14, 939–944 (2019).

    CAS  Article  Google Scholar 

  13. 13.

    Safeer, C. K. et al. Spin–orbit torque magnetization switching controlled by geometry. Nat. Nanotechnol. 11, 143–146 (2016).

    CAS  Article  Google Scholar 

  14. 14.

    Kong, W. J. et al. Spin–orbit torque switching in a T-type magnetic configuration with current orthogonal to easy axes. Nat. Commun. 10, 233 (2019).

    CAS  Article  Google Scholar 

  15. 15.

    Baek, Sh. C. et al. Spin currents and spin–orbit torques in ferromagnetic trilayers. Nat. Mater. 17, 509–513 (2018).

    CAS  Article  Google Scholar 

  16. 16.

    Laref, S., Kim, K. W. & Manchon, A. Elusive Dzyaloshinskii-Moriya interaction in monolayer Fe3GeTe2. Phys. Rev. B 102, 060402 (2020).

    CAS  Article  Google Scholar 

  17. 17.

    Johansen, Ø., Risinggård, V., Sudbø, A., Linder, J. & Brataas, A. Current control of magnetism in two-dimensional Fe3GeTe2. Phys. Rev. Lett. 122, 217203 (2019).

    CAS  Article  Google Scholar 

  18. 18.

    Iwata, S., Yamashita, S. & Tsunashima, S. Perpendicular magnetic anisotropy and magneto-optical Kerr spectra of MBE-grown PtCo alloy films. IEEE Trans. Magn. 33, 3670–3672 (1997).

    CAS  Article  Google Scholar 

  19. 19.

    Dannenberg, A., Gruner, M. E., Hucht, A. & Entel, P. Surface energies of stoichiometric FePt and CoPt alloys and their implications for nanoparticle morphologies. Phys. Rev. B 80, 245438 (2009).

    Article  Google Scholar 

  20. 20.

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

    CAS  Article  Google Scholar 

  21. 21.

    Suzuki, D., Ohtake, M., Kirino, F. & Futamoto, M. Preparation of CoPt-alloy thin films with perpendicular magnetic anisotropy on MgO(111), SrTiO3(111), and Al2O3(0001) single-crystal substrates. IEEE Trans. Magn. 48, 3195–3198 (2012).

    CAS  Article  Google Scholar 

  22. 22.

    Garello, K. et al. Symmetry and magnitude of spin–orbit torques in ferromagnetic heterostructures. Nat. Nanotechnol. 8, 587–593 (2013).

    CAS  Article  Google Scholar 

  23. 23.

    Hayashi, M., Kim, J., Yamanouchi, M. & Ohno, H. Quantitative characterization of the spin-orbit torque using harmonic Hall voltage measurements. Phys. Rev. B 89, 144425 (2014).

    Article  Google Scholar 

  24. 24.

    Pi, U. H. et al. Tilting of the spin orientation induced by Rashba effect in ferromagnetic metal layer. Appl. Phys. Lett. 97, 162507 (2010).

    Article  Google Scholar 

  25. 25.

    Kim, J. et al. Layer thickness dependence of the current-induced effective field vector in Ta|CoFeB|MgO. Nat. Mater. 12, 240–245 (2013).

    CAS  Article  Google Scholar 

  26. 26.

    Guillemard, C., Petit-Watelot, S., Andrieu, S. & Rojas-Sánchez, J. C. Charge-spin current conversion in high quality epitaxial Fe/Pt systems: isotropic spin Hall angle along different in-plane crystalline directions. Appl. Phys. Lett. 113, 262404 (2018).

    Article  Google Scholar 

  27. 27.

    Pai, C.-F., Mann, M., Tan, A. J. & Beach, G. S. D. Determination of spin torque efficiencies in heterostructures with perpendicular magnetic anisotropy. Phys. Rev. B 93, 144409 (2016).

    Article  Google Scholar 

  28. 28.

    Železný, J. et al. Spin-orbit torques in locally and globally noncentrosymmetric crystals: antiferromagnets and ferromagnets. Phys. Rev. B 95, 014403 (2017).

    Article  Google Scholar 

Download references

Acknowledgements

This research is supported by the Singapore National Research Foundation under CRP Award No. NRF-CRP10-2012-02 and the Singapore Ministry of Education MOE2018-T2-1-019 and MOE2018-T2-2-043, A*STAR Grant No. A1983C0036, A*STAR IAF-ICP 11801E0036, MOE Tier1 R-284-000-195-114 and the King Abdullah University of Science and Technology (KAUST). J.S.C. is a member of the Singapore Spintronics Consortium (SG-SPIN).

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L.L. and J.S.C. conceived and designed the experiments. L.L. and C.Z. performed the thin film deposition, device fabrication, transport measurements and data analysis. A.M. theoretically proposed the 3m torque and performed the calculations. T.Z., X.S., J.D., Q.X., S.C., S.S. and J.Y. contributed to the thin film deposition and device fabrication. W.L., J.Z., R.G., H.W. and P.Y. contributed to the data analysis. C.L. and S.P. performed the STEM experiments. L.L., C.Z., A.M. and J.S.C. wrote the manuscript and all authors contributed to its final version.

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Correspondence to Aurelien Manchon or Jingsheng Chen.

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Peer review information Nature Nanotechnology thanks Byong-Guk Park and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Sections 1–14, Figs. 1–38 and refs. 1–4.

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Source Data Fig. 3

Numerical data.

Source Data Fig. 5

Numerical data.

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Liu, L., Zhou, C., Shu, X. et al. Symmetry-dependent field-free switching of perpendicular magnetization. Nat. Nanotechnol. 16, 277–282 (2021). https://doi.org/10.1038/s41565-020-00826-8

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