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Electrically tunable spin injector free from the impedance mismatch problem

Nature Materials volume 10, pages 655–659 (2011)Cite this article

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Abstract

Injection of spin currents into solids is crucial for exploring spin physics and spintronics1,2. There has been significant progress in recent years in spin injection into high-resistivity materials, for example, semiconductors and organic materials, which uses tunnel barriers to circumvent the impedance mismatch problem3,4,5,6,7,8,9,10,11,12,13,14; the impedance mismatch between ferromagnetic metals and high-resistivity materials drastically limits the spin-injection efficiency15. However, because of this problem, there is no route for spin injection into these materials through low-resistivity interfaces, that is, Ohmic contacts, even though this promises an easy and versatile pathway for spin injection without the need for growing high-quality tunnel barriers. Here we show experimental evidence that spin pumping enables spin injection free from this condition; room-temperature spin injection into GaAs from Ni81Fe19 through an Ohmic contact is demonstrated through dynamical spin exchange. Furthermore, we demonstrate that this exchange can be controlled electrically by applying a bias voltage across a Ni81Fe19/GaAs interface, enabling electric tuning of the spin-pumping efficiency.

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Figure 1: Spin injection through carrier transport and dynamical exchange interaction.
Figure 2: Dynamical spin injection and ISHE.
Figure 3: Measurements of spin injection.
Figure 4: Electric control of dynamical spin injection.

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Acknowledgements

This work was supported by the Cabinet Office, Government of Japan, through its ‘Funding Program for Next Generation World-Leading Researchers’, a Grant-in-Aid for Research Activity Start-Up (2284005) from MEXT, Japan, a Strategic Information and Communications R&D Promotion Program from MIC (102102001), Japan, a Grant-in-Aid for Scientific Research in Priority Area ‘Creation and control of spin current’ (19048028, 19048009) from MEXT, Japan, a Grant-in-Aid for Scientific Research (A) (21244058) from MEXT, Japan, CREST-JST, Japan, and the Next Generation Supercomputing Project of Nanoscience Program from IMS, Japan.

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Authors and Affiliations

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

    K. Ando, S. Takahashi & E. Saitoh

  2. CREST, Japan Science and Technology Agency, Sanbancho, Tokyo 102-0075, Japan

    S. Takahashi, J. Ieda, S. Maekawa & E. Saitoh

  3. The Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan

    J. Ieda, S. Maekawa & E. Saitoh

  4. Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge CB3 0HE, UK

    H. Kurebayashi, T. Trypiniotis & C. H. W. Barnes

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  1. K. Ando
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  2. S. Takahashi
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  3. J. Ieda
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  4. H. Kurebayashi
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  7. S. Maekawa
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Contributions

K.A. designed the experiment, collected all of the data and analysed the data. E.S. supervised the study. K.A., H.K. and T.T. fabricated the samples. K.A., S.T., J.I., H.K., C.H.W.B. and S.M. developed the explanation of the experiment. K.A. and S.T. wrote the manuscript. All authors discussed the results and commented on the manuscript.

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Correspondence to K. Ando.

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Ando, K., Takahashi, S., Ieda, J. et al. Electrically tunable spin injector free from the impedance mismatch problem. Nature Mater 10, 655–659 (2011). https://doi.org/10.1038/nmat3052

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