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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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.

Author information

Author notes

  1. These authors contributed equally: Do Bang, Rahul Mishra

Affiliations

  1. Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore

    • Jiawei Yu
    • , Rahul Mishra
    • , Rajagopalan Ramaswamy
    • , Yi Wang
    • , Shuyuan Shi
    •  & Hyunsoo Yang
  2. Toyota Technological Institute, Tempaku, Nagoya, Japan

    • Do Bang
    • , Pham Van Thach
    •  & Hiroyuki Awano
  3. Institute of Materials Science, Vietnam Academy of Science and Technology, Hanoi, Vietnam

    • Do Bang
    •  & Pham Van Thach
  4. Department of Materials Science and Engineering, Korea University, Seoul, Korea

    • Jung Hyun Oh
    • , Dong-Kyu Lee
    • , Gyungchoon Go
    • , Seo-Won Lee
    •  & Kyung-Jin Lee
  5. KU-KIST Graduate School of Conversing Science and Technology, Korea University, Seoul, Korea

    • Hyeon-Jong Park
    •  & Kyung-Jin Lee
  6. Department of Semiconductor Systems Engineering, Korea University, Seoul, Korea

    • Yunboo Jeong
    •  & Kyung-Jin Lee
  7. Shanghai Key Laboratory of Special Artificial Macrostructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, China

    • Xuepeng Qiu

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Contributions

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.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Kyung-Jin Lee or Hyunsoo Yang.

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  1. Supplementary Information

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DOI

https://doi.org/10.1038/s41563-018-0236-9