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Long-range mutual synchronization of spin Hall nano-oscillators

Nature Physics volume 13, pages 292–299 (2017)Cite this article

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Abstract

The spin Hall effect in a non-magnetic metal with spin–orbit coupling injects transverse spin currents into adjacent magnetic layers, where the resulting spin transfer torque can drive spin wave auto-oscillations. Such spin Hall nano-oscillators (SHNOs) hold great promise as extremely compact and broadband microwave signal generators and magnonic spin wave injectors. Here we show that SHNOs can also be mutually synchronized with unprecedented efficiency. We demonstrate mutual synchronization of up to nine individual SHNOs, each separated by 300 nm. Through further tailoring of the connection regions we can extend the synchronization range to 4 μm. The mutual synchronization is observed electrically as an increase in the power and coherence of the microwave signal, and confirmed optically using micro-Brillouin light scattering microscopy as two spin wave regions sharing the same spectral content, in agreement with our micromagnetic simulations.

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Figure 1: Device schematic, current distribution, and static measurements.
Figure 6: Multiple SHNO synchronization.
Figure 2: Electrical microwave characterization.
Figure 3: Micromagnetic simulations.
Figure 4: μ-BLS measurements.
Figure 5: Long-range synchronization.

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Acknowledgements

We thank M. Madami for assistance in building the μ-BLS microscope. This work was supported by the European Research Council (ERC) under the European Community’s Seventh Framework Programme (FP/2007-2013)/ERC Grant 307144 ‘MUSTANG’. This work was also supported by the Swedish Research Council (VR), the Swedish Foundation for Strategic Research (SSF), and the Knut and Alice Wallenberg Foundation.

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Authors and Affiliations

  1. Physics Department, University of Gothenburg, 412 96 Gothenburg, Sweden

    A. A. Awad, P. Dürrenfeld, A. Houshang, M. Dvornik, E. Iacocca, R. K. Dumas & J. Åkerman

  2. Material Physics, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista, Sweden

    J. Åkerman

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Contributions

A.A.A. designed the devices. P.D. and A.H. fabricated the devices. A.A.A., P.D. and A.H. performed all electrical measurements. R.K.D. and A.A.A. built the μ-BLS microscope. A.A.A. carried out all optical measurements. A.A.A. and M.D. performed the micromagnetic simulations. All authors contributed to the data analysis and co-wrote the manuscript.

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Correspondence to J. Åkerman.

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The authors declare no competing financial interests.

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Awad, A., Dürrenfeld, P., Houshang, A. et al. Long-range mutual synchronization of spin Hall nano-oscillators. Nature Phys 13, 292–299 (2017). https://doi.org/10.1038/nphys3927

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