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Two-terminal spin–orbit torque magnetoresistive random access memory

Nature Electronicsvolume 1pages508511 (2018) | Download Citation

Abstract

Spin-transfer torque magnetoresistive random access memory (STT-MRAM) is an attractive alternative to existing random access memory technologies due to its non-volatility, fast operation and high endurance. However, STT-MRAM does have limitations, including the stochastic nature of the STT-switching and a high critical switching current, which makes it unsuitable for ultrafast operation in the nanosecond and subnanosecond regimes. Spin–orbit torque (SOT) switching, which relies on the torque generated by an in-plane current, has the potential to overcome these limitations. However, SOT-MRAM cells studied so far use a three-terminal structure to apply the in-plane current, which increases the size of the cells. Here we report a two-terminal SOT-MRAM cell based on a CoFeB/MgO magnetic tunnel junction pillar on an ultrathin and narrow Ta underlayer. In this device, in-plane and out-of-plane currents are simultaneously generated on application of a voltage, and we demonstrate that the switching mechanism is dominated by SOT.

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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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References

  1. 1.

    International Technology Roadmap for Semiconductors (ITRS, accessed 17 June 2018); http://www.itrs2.net/

  2. 2.

    Ikeda, S. et al. A perpendicular-anisotropy CoFeB–MgO magnetic tunnel junction. Nat. Mater. 9, 721–724 (2010).

  3. 3.

    Worledge, D. C., Hu, G., Abraham, D. W., Trouilloud, P. L. & Brown, S. Development of perpendicularly magnetized Ta|CoFeB|MgO-based tunnel junctions at IBM (invited). J. Appl. Phys. 115, 172601 (2014).

  4. 4.

    Sato, H. et al. MgO/CoFeB/Ta/CoFeB/MgO recording structure in magnetic tunnel junctions with perpendicular easy axis. IEEE. Trans. Magn. 49, 4437–4440 (2013).

  5. 5.

    Yuasa, S., Hono, K., Hu, G. & Worledge, D. C. Materials for spin-transfer-torque magnetoresistive random-access memory. MRS. Bull. 43, 352–357 (2018).

  6. 6.

    Dieny, B., Goldfarb, R. B. & Lee, K.-J. Introduction to Magnetic Random-Access Memory (Wiley-IEEE Press, New York, 2016).

  7. 7.

    Zhang, S. Spin Hall effect in the presence of spin diffusion. Phys. Rev. Lett. 85, 393–396 (2000).

  8. 8.

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

  9. 9.

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

  10. 10.

    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).

  11. 11.

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

  12. 12.

    Garello, K. et al. Ultrafast magnetization switching by spin–orbit torques. Appl. Phys. Lett. 105, 212402 (2014).

  13. 13.

    Manipatruni, S., Nikonov, D. E. & Young, I. A. Beyond CMOS computing with spin and polarization. Nat. Phys. 14, 338–343 (2018).

  14. 14.

    Brosse, J. K. D., Liu, L. & Worledge, D. Spin Hall effect assisted spin transfer torque magnetic random access memory. US patent 20140264511A1 (2014).

  15. 15.

    Wang, Z., Zhao, W., Deng, E., Klein, J.-O. & Chappert, C. Perpendicular-anisotropy magnetic tunnel junction switched by spin-Hall-assisted spin-transfer torque. J. Phys. D 48, 065001 (2015).

  16. 16.

    van den Brink, A. et al. Spin-Hall-assisted magnetic random access memory. Appl. Phys. Lett. 104, 012403 (2014).

  17. 17.

    Lee, K.-S., Lee, S.-W., Min, B.-C. & Lee, K.-J. Threshold current for switching of a perpendicular magnetic layer induced by spin Hall effect. Appl. Phys. Lett. 102, 112410 (2013).

  18. 18.

    Cubukcu, M. et al. Ultra-fast perpendicular spin–orbit torque MRAM. IEEE. Trans. Magn. 54, 9300204 (2018).

  19. 19.

    Zhang, C., Fukami, S., Sato, H., Matsukura, F. & Ohno, H. Spin–orbit torque induced magnetization switching in nano-scale Ta/CoFeB/MgO. Appl. Phys. Lett. 107, 012401 (2015).

  20. 20.

    Lee, K.-S., Lee, S.-W., Min, B.-C. & Lee, K.-J. Thermally activated switching of perpendicular magnet by spin–orbit spin torque. Appl. Phys. Lett. 104, 072413 (2014).

  21. 21.

    Taniguchi, T., Mitani, S. & Hayashi, M. Critical current destabilizing perpendicular magnetization by the spin Hall effect. Phys. Rev. B 92, 024428 (2015).

  22. 22.

    Wang, M. et al. Field-free switching of perpendicular magnetic tunnel junction by the interplay of spin orbit and spin transfer torques. Preprint at https://arXiv.org/abs/1806.06174 (2018).

  23. 23.

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

  24. 24.

    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).

  25. 25.

    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).

  26. 26.

    Hsu, W.-H., Bell, R. & Victora, R.H. Ultra-low write energy composite free layer spin-orbit torque MRAM. IEEE Tran. Mag. https://doi.org/10.1109/TMAG.2018.2847235 (2018).

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Acknowledgements

S.X.W. thanks TSMC, Stanford SystemX Alliance, Stanford Center for Magnetic Nanotechnology, and the NSF Center for Energy Efficient Electronics Science (E3S) for financial support. N.S. thanks Funai Foundation for Information Technology for the overseas scholarship. This work was supported in part by ASCENT, one of six centres in JUMP, a Semiconductor Research Corporation (SRC) programme sponsored by DARPA. The experimental work has benefited from the equipment and tools at the Stanford Nanofabrication Facility, Stanford Nano Shared Facilities, and Michigan Lurie Nanofabrication Facility (LNF), which are supported by the National Science Foundation (NSF).

Author information

Affiliations

  1. Department of Electrical Engineering, Stanford University, Stanford, CA, USA

    • Noriyuki Sato
    • , Fen Xue
    • , Robert M. White
    • , Chong Bi
    •  & Shan X. Wang
  2. Department of Electrical Engineering, Tsinghua University, Beijing, China

    • Fen Xue
  3. Department of Material Science and Engineering, Stanford University, Stanford, CA, USA

    • Robert M. White
    •  & Shan X. Wang

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Contributions

N.S., R.M.W. and S.X.W. conceived the experiments, N.S. and F.X. conducted the experiments, and N.S., C.B. and S.X.W. analysed the results. All authors reviewed the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding author

Correspondence to Shan X. Wang.

Supplementary information

  1. Supplementary Information

    Supplementary Notes 1–5 and Supplementary Figures 1–10

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DOI

https://doi.org/10.1038/s41928-018-0131-z

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