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Direct observation of a propagating spin wave induced by spin-transfer torque

Abstract

Spin torque oscillators with nanoscale electrical contacts1,2,3,4 are able to produce coherent spin waves in extended magnetic films, and offer an attractive combination of electrical and magnetic field control, broadband operation5,6, fast spin-wave frequency modulation7,8,9, and the possibility of synchronizing multiple spin-wave injection sites10,11. However, many potential applications rely on propagating (as opposed to localized) spin waves, and direct evidence for propagation has been lacking. Here, we directly observe a propagating spin wave launched from a spin torque oscillator with a nanoscale electrical contact into an extended Permalloy (nickel iron) film through the spin transfer torque effect. The data, obtained by wave-vector-resolved micro-focused Brillouin light scattering, show that spin waves with tunable frequencies can propagate for several micrometres. Micromagnetic simulations provide the theoretical support to quantitatively reproduce the results.

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Figure 1: Schematic sample layout.
Figure 2: Characterization of the optical window.
Figure 3: Spin-wave frequencies as a function of the injected d.c. intensity.
Figure 4: Proof of spin-wave propagation.
Figure 5: Spin-wave attenuation as a function of distance from the STO.

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Acknowledgements

This work was supported by CNISM under the μ-BLS INNESCO project. Authors acknowledge the European Community's Seventh Framework Programme (FP7/2007-2013, grant agreement no. 228673, MAGNONICS). Support from the Swedish Foundation for Strategic Research (SSF), the Swedish Research Council (VR) and the Knut and Alice Wallenberg Foundation is gratefully acknowledged. J.Å. is a Royal Swedish Academy of Sciences Research Fellow supported by a grant from the Knut and Alice Wallenberg Foundation. The authors gratefully acknowledge S. Redjai Sani at the Royal Institute of Technology for help with the wet etching process, F. Magnusson and W. Michelsen at NanOsc AB for their help in designing the printed circuit boards, and S. Gunnarsson, S. Sandelin and K. Penkkilä at Sivers IMA AB for performing the wire bonding. S.B. gratefully acknowledges support from the C.M. Lerici foundation.

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Contributions

M.M., G.G., S.T. and G.Ca. performed μ-BLS measurements. S.B., M.A.Y. and J.Å. realized the procedure to open the optical access to the sample and performed EDS measurements. F.B.M. fabricated the original samples. G.Co. performed numerical simulations. All authors co-wrote the manuscript.

Corresponding authors

Correspondence to M. Madami or S. Bonetti.

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The authors declare no competing financial interests.

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Madami, M., Bonetti, S., Consolo, G. et al. Direct observation of a propagating spin wave induced by spin-transfer torque. Nature Nanotech 6, 635–638 (2011). https://doi.org/10.1038/nnano.2011.140

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