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Two-terminal spin–orbit torque magnetoresistive random access memory

Nature Electronicsvolume 1pages508511 (2018) | Download Citation


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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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


  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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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.

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  1. Supplementary Information

    Supplementary Notes 1–5 and Supplementary Figures 1–10

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