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Transmission of electrical signals by spin-wave interconversion in a magnetic insulator

Nature volume 464, pages 262–266 (2010)Cite this article

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Abstract

The energy bandgap of an insulator is large enough to prevent electron excitation and electrical conduction1. But in addition to charge, an electron also has spin2, and the collective motion of spin can propagate—and so transfer a signal—in some insulators3. This motion is called a spin wave and is usually excited using magnetic fields. Here we show that a spin wave in an insulator can be generated and detected using spin-Hall effects, which enable the direct conversion of an electric signal into a spin wave, and its subsequent transmission through (and recovery from) an insulator over macroscopic distances. First, we show evidence for the transfer of spin angular momentum between an insulator magnet Y3Fe5O12 and a platinum film. This transfer allows direct conversion of an electric current in the platinum film to a spin wave in the Y3Fe5O12 via spin-Hall effects4,5,6,7,8,9,10,11. Second, making use of the transfer in a Pt/Y3Fe5O12/Pt system, we demonstrate that an electric current in one metal film induces voltage in the other, far distant, metal film. Specifically, the applied electric current is converted into spin angular momentum owing to the spin-Hall effect7,8,10,11 in the first platinum film; the angular momentum is then carried by a spin wave in the insulating Y3Fe5O12 layer; at the distant platinum film, the spin angular momentum of the spin wave is converted back to an electric voltage. This effect can be switched on and off using a magnetic field. Weak spin damping3 in Y3Fe5O12 is responsible for its transparency for the transmission of spin angular momentum. This hybrid electrical transmission method potentially offers a means of innovative signal delivery in electrical circuits and devices.

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Figure 1: Two types of non-equilibrium spin currents in solids.
Figure 2: Spin pumping in Pt/Y3Fe5O12.
Figure 3: Magnetization oscillation induced by spin-transfer torque in Pt/Y3Fe5O12.
Figure 4: Electric-signal transmission via spin-wave spin currents.

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Acknowledgements

We thank K. Sato, Y. Suzuki, Y. Tserkovnyak, G. Tatara, T. Ishibashi and K. M. Itoh for discussions. This work was supported by a Grant-in-Aid for Scientific Research in Priority Area ‘Creation and control of spin current’ (19048028) from MEXT, Japan, a Grant-in-Aid for Scientific Research (A) from MEXT, Japan, the global COE for the ‘Materials integration international centre of education and research’ and ‘High-level global cooperation for leading-edge platform on access spaces (C12)’ from MEXT, Japan, a Grant for Industrial Technology Research from NEDO, Japan, and Fundamental Research Grant from TRF, Japan.

Author Contributions Y.K., K.H., K.U. and K.A. performed the measurements and analysed the data; J.O. carried out the numerical analysis; S.T., S.M. and E.S. provided the theoretical analysis; H.U. and H.K. contributed to the sample fabrication; Y.K., K.H, K.U., M.M. and K.T. contributed to the experimental set-up; Y.K., S.T., J.O., K.U., M.M., H.U., K.T., S.M. and E.S. wrote the manuscript; all authors discussed the results and commented on the manuscript; and E.S. planned and supervised the project.

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Authors and Affiliations

  1. Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan

    Y. Kajiwara, K. Harii, S. Takahashi, J. Ohe, K. Uchida, M. Mizuguchi, K. Ando, K. Takanashi, S. Maekawa & E. Saitoh

  2. Department of Applied Physics and Physico-Informatics, Keio University, Yokohama 223-8522, Japan

    Y. Kajiwara, K. Ando & E. Saitoh

  3. CREST,,

    S. Takahashi, J. Ohe & S. Maekawa

  4. PRESTO, Japan Science and Technology Agency, Sanbancho, Tokyo 102-0075, Japan ,

    E. Saitoh

  5. FDK Corporation, Shizuoka 431-0495, Japan

    H. Umezawa & H. Kawai

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  1. Y. Kajiwara
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Correspondence to E. Saitoh.

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Kajiwara, Y., Harii, K., Takahashi, S. et al. Transmission of electrical signals by spin-wave interconversion in a magnetic insulator. Nature 464, 262–266 (2010). https://doi.org/10.1038/nature08876

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