Long spin coherence length and bulk-like spin–orbit torque in ferrimagnetic multilayers

Abstract

Spintronics relies on magnetization switching through current-induced spin torques. However, because spin transfer torque for ferromagnets is a surface torque, a large switching current is required for a thick, thermally stable ferromagnetic cell, and this remains a fundamental obstacle for high-density non-volatile applications with ferromagnets. Here, we report a long spin coherence length and associated bulk-like torque characteristics in an antiferromagnetically coupled ferrimagnetic multilayer. We find that a transverse spin current can pass through >10-nm-thick ferrimagnetic Co/Tb multilayers, whereas it is entirely absorbed by a 1-nm-thick ferromagnetic Co/Ni multilayer. We also find that the switching efficiency of Co/Tb multilayers partially reflects a bulk-like torque characteristic, as it increases with ferrimagnet thickness up to 8 nm and then decreases, in clear contrast to the 1/thickness dependence of ferromagnetic Co/Ni multilayers. Our results on antiferromagnetically coupled systems will invigorate research towards the development of energy-efficient spintronics.

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Fig. 1: Semiclassical illustration of increased spin coherence length in FIMs compared to ferromagnets.
Fig. 2: SOTs in ferromagnetic versus ferrimagnetic film stacks.
Fig. 3: SOT effective fields and switching efficiencies in ferromagnetic versus ferrimagnetic multilayers.
Fig. 4: Spin pumping measurements.
Fig. 5: Characterizations of CoTb alloy samples.

Data availability

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

References

  1. 1.

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

    CAS  Article  Google Scholar 

  2. 2.

    Berger, L. Emission of spin waves by a magnetic multilayer traversed by a current. Phys. Rev. B 54, 9353–9358 (1996).

    CAS  Article  Google Scholar 

  3. 3.

    Tsoi, M. et al. Excitation of a magnetic multilayer by an electric current. Phys. Rev. Lett. 80, 4281–4284 (1998).

    CAS  Article  Google Scholar 

  4. 4.

    Myers, E. B., Ralph, D. C., Katine, J. A., Louie, R. N. & Buhrman, R. A. Current-induced switching of domains in magnetic multilayer devices. Science 285, 867–870 (1999).

    CAS  Article  Google Scholar 

  5. 5.

    Waintal, X., Myers, E. B., Brouwer, P. W. & Ralph, D. C. Role of spin-dependent interface scattering in generating current-induced torques in magnetic multilayers. Phys. Rev. B 62, 12317–12327 (2000).

    CAS  Article  Google Scholar 

  6. 6.

    Stiles, M. D. & Zangwill, A. Anatomy of spin-transfer torque. Phys. Rev. B 66, 014407 (2002).

    Article  Google Scholar 

  7. 7.

    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 

  8. 8.

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

    CAS  Article  Google Scholar 

  9. 9.

    Kovalev, A. A., Bauer, G. E. W. & Brataas, A. Perpendicular spin valves with ultrathin ferromagnetic layers: magnetoelectronic circuit investigation of finite-size effects. Phys. Rev. B 73, 054407 (2006).

    Article  Google Scholar 

  10. 10.

    Núñez, A. S., Duine, R. A., Haney, P. & MacDonald, A. H. Theory of spin torques and giant magnetoresistance in antiferromagnetic metals. Phys. Rev. B 73, 214426 (2006).

    Article  Google Scholar 

  11. 11.

    Haney, P. M. & MacDonald, A. H. Current-induced torques due to compensated antiferromagnets. Phys. Rev. Lett. 100, 196801 (2008).

    Article  Google Scholar 

  12. 12.

    Xu, Y., Wang, S. & Xia, K. Spin-transfer torques in antiferromagnetic metals from first principles. Phys. Rev. Lett. 100, 226602 (2008).

    Article  Google Scholar 

  13. 13.

    Wei, Z. et al. Changing exchange bias in spin valves with an electric current. Phys. Rev. Lett. 98, 116603 (2007).

    CAS  Article  Google Scholar 

  14. 14.

    Urazhdin, S. & Anthony, N. Effect of polarized current on the magnetic state of an antiferromagnet. Phys. Rev. Lett. 99, 046602 (2007).

    Article  Google Scholar 

  15. 15.

    Wadley, P. et al. Electrical switching of an antiferromagnet. Science 351, 587–590 (2016).

    CAS  Article  Google Scholar 

  16. 16.

    Mishra, R. et al. Anomalous current-induced spin torques in ferrimagnets near compensation. Phys. Rev. Lett. 118, 167201 (2017).

    Article  Google Scholar 

  17. 17.

    Finley, J. & Liu, L. Spin–orbit-torque efficiency in compensated ferrimagnetic cobalt-terbium alloys. Phys. Rev. Appl. 6, 054001 (2016).

    Article  Google Scholar 

  18. 18.

    Roschewsky, N., Lambert, C.-H. & Salahuddin, S. Spin–orbit torque switching of ultralarge-thickness ferrimagnetic GdFeCo. Phys. Rev. B 96, 064406 (2017).

    Article  Google Scholar 

  19. 19.

    Ueda, K., Mann, M., de Brouwer, P. W. P., Bono, D. & Beach, G. S. D. Temperature dependence of spin–orbit torques across the magnetic compensation point in a ferrimagnetic TbCo alloy film. Phys. Rev. B 96, 064410 (2017).

    Article  Google Scholar 

  20. 20.

    Fert, A., Emley, N. C., Myers, E. B., Ralph, D. C. & Buhrman, R. A. Quantitative study of magnetization reversal by spin-polarized current in magnetic multilayer nanopillars. Phys. Rev. Lett. 89, 226802 (2002).

    Article  Google Scholar 

  21. 21.

    Kim, K.-J. et al. Fast domain wall motion in the vicinity of the angular momentum compensation temperature of ferrimagnets. Nat. Mater. 16, 1187–1192 (2017).

    CAS  Article  Google Scholar 

  22. 22.

    Hebler, B., Hassdenteufel, A., Reinhardt, P., Karl, H. & Albrecht, M. Ferrimagnetic Tb–Fe alloy thin films: composition and thickness dependence of magnetic properties and all-optical switching. Front. Mater. 3, 8 (2016).

    Article  Google Scholar 

  23. 23.

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

    CAS  Article  Google Scholar 

  24. 24.

    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 

  25. 25.

    Jamali, M. et al. Spin–orbit torques in Co/Pd multilayer nanowires. Phys. Rev. Lett. 111, 246602 (2013).

    Article  Google Scholar 

  26. 26.

    Qiu, X. et al. Angular and temperature dependence of current induced spin–orbit effective fields in Ta/CoFeB/MgO nanowires. Sci. Rep. 4, 4491 (2014).

    Article  Google Scholar 

  27. 27.

    Lee, O. J. et al. Central role of domain wall depinning for perpendicular magnetization switching driven by spin torque from the spin Hall effect. Phys. Rev. B 89, 024418 (2014).

    Article  Google Scholar 

  28. 28.

    Brataas, A., Kent, A. D. & Ohno, H. Current-induced torques in magnetic materials. Nat. Mater. 11, 372–381 (2012).

    CAS  Article  Google Scholar 

  29. 29.

    Graves, C. E. et al. Nanoscale spin reversal by non-local angular momentum transfer following ultrafast laser excitation in ferrimagnetic GdFeCo. Nat. Mater. 12, 293–298 (2013).

    CAS  Article  Google Scholar 

  30. 30.

    Chimata, R. et al. All-thermal switching of amorphous Gd–Fe alloys: analysis of structural properties and magnetization dynamics. Phys. Rev. B 92, 094411 (2015).

    Article  Google Scholar 

  31. 31.

    Harris, V. G., Aylesworth, K. D., Das, B. N., Elam, W. T. & Koon, N. C. Structural origins of magnetic anisotropy in sputtered amorphous Tb–Fe films. Phys. Rev. Lett. 69, 1939–1942 (1992).

    CAS  Article  Google Scholar 

  32. 32.

    Hufnagel, T. C., Brennan, S., Zschack, P. & Clemens, B. M. Structural anisotropy in amorphous Fe–Tb thin films. Phys. Rev. B 53, 12024–12030 (1996).

    CAS  Article  Google Scholar 

  33. 33.

    Emori, S., Bauer, U., Ahn, S.-M., Martinez, E. & Beach, G. S. D. Current-driven dynamics of chiral ferromagnetic domain walls. Nat. Mater. 12, 611–616 (2013).

    CAS  Article  Google Scholar 

  34. 34.

    Ryu, K.-S., Thomas, L., Yang, S.-H. & Parkin, S. Chiral spin torque at magnetic domain walls. Nat. Nanotech. 8, 527–533 (2013).

    CAS  Article  Google Scholar 

  35. 35.

    Sampaio, J., Cros, V., Rohart, S., Thiaville, A. & Fert, A. Nucleation, stability and current-induced motion of isolated magnetic skyrmions in nanostructures. Nat. Nanotech. 8, 839–844 (2013).

    CAS  Article  Google Scholar 

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Acknowledgements

The authors acknowledge discussions with P.M. Haney. 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). K.-J.L. was supported by the National Research Foundation of Korea (NRF-2015M3D1A1070465 and NRF-2017R1A2B2006119) and the KIST Institutional Program (project no. 2V05750) and Samsung Research Funding Center of Samsung Electronics under project no. SRFCMA1702-02.

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J.Y. and H.Y. planned the project. J.Y., D.B. and P.V.T. deposited films. J.Y. and R.M. fabricated devices and performed the transport measurements. J.Y., R.R., R.M., Y.W. and S.S. carried out the spin pumping measurements. J.H.O., H.-J.P., Y.J., D.-K.L., S.-W.L., G.G. and K.-J.L. performed theoretical analysis. J.Y., D.B., X.Q., R.M., Y.J. and G.G. analysed the data with the help of H.A., K.-J.L. and H.Y. All authors discussed the results and commented on the manuscript. J.Y., K.-J.L. and H.Y. wrote the manuscript. H.Y. initiated the idea and led the project.

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Correspondence to Kyung-Jin Lee or Hyunsoo Yang.

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Yu, J., Bang, D., Mishra, R. et al. Long spin coherence length and bulk-like spin–orbit torque in ferrimagnetic multilayers. Nature Mater 18, 29–34 (2019). https://doi.org/10.1038/s41563-018-0236-9

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