# Spin pumping from nuclear spin waves

## Abstract

Various spintronic phenomena originate from the exchange of angular momentum between the spin of electrons and other degrees of freedom in crystalline materials. Many degrees of freedom, such as magnetization1 and mechanical motion2, have already been united into this exchange framework. However, the nuclear spin—a key angular momentum—has yet to be incorporated. Here we observe spin pumping from nuclear magnetic resonance (NMR), in which nuclear spin dynamics emits a spin current, a flow of spin angular momentum of electrons. By using the canted antiferromagnet MnCO3, in which typical nuclear spin-wave formation is established due to the reinforced hyperfine coupling, we find that a spin current is generated from an NMR. Nuclear spins are indispensable for quantum information technology3 and are also frequently used in various sensors, such as in magnetic resonance imaging4. The observed NMR spin pumping allows spin-current generation from nuclei and will enable spintronic detection of nuclear spin states.

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## Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding authors upon reasonable request.

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## Acknowledgements

We thank H. Yasuoka, S. Maekawa, M. Matsuo, H. Chudo, K. Harii and M. Imai for fruitful discussions. This research was supported by JST ERATO ‘Spin Quantum Rectification Project’ (JPMJER1402), JSPS KAKENHI (no. 17H04806, no. JP18H04215, no. 18H04311, no. JP16J03699 and no. 17H02927) and MEXT (Innovative Area ‘Nano Spin Conversion Science’ (no. 26103005)).

## Author information

Authors

### Contributions

S.W. conceived the experiments in discussions with Y.S. and D.H. Y.S., J.L. and S.W. constructed the experimental set-up, performed the experiments, and analysed the experimental data. S.T. conducted the theoretical calculations. Y.S., J.L., S.W. and E.S. wrote the manuscript. E.S. supervised the project. All authors discussed the results and reviewed the manuscript.

### Corresponding authors

Correspondence to Yuki Shiomi or Eiji Saitoh.

## Ethics declarations

### Competing interests

The authors declare no competing interests.

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## Supplementary information

### Supplementary Information

Theoretical calculations; Supplementary Figures 1–8; Supplementary References 1–8

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Reprints and Permissions

Shiomi, Y., Lustikova, J., Watanabe, S. et al. Spin pumping from nuclear spin waves. Nature Phys 15, 22–26 (2019). https://doi.org/10.1038/s41567-018-0310-x

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