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Nanomechanical detection of itinerant electron spin flip

Nature Nanotechnology volume 3, pages 720–723 (2008)Cite this article

Abstract

Electrons and other fundamental particles have an intrinsic angular momentum called spin. A change in the spin state of such a particle is therefore equivalent to a mechanical torque. This spin-induced torque is central to our understanding of experiments1,2 ranging from the measurement of the angular momentum of photons3 and the g-factor of metals4,5,6,7 to magnetic resonance8 and magnetization reversal in magnetic multilayers8,9,10,11,12,13,14,15. When a spin-polarized current passes through a metallic nanowire in which one half is ferromagnetic and the other half is nonmagnetic, the spins of the itinerant electrons are ‘flipped’ at the interface between the two regions to produces a torque. Here, we report direct measurement of this mechanical torque in an integrated nanoscale torsion oscillator, and measurements of the itinerant electron spin polarization that could yield new information on the itinerancy of the d-band electrons. The unprecedented torque sensitivity of 1 × 10−22 N-m Hz−1/2 may have applications in spintronics and precision measurements of charge–parity-violating forces16,17, and might also enable experiments on the untwisting of DNA18 and torque-generating molecules19,20.

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Figure 1: The spin-torsion mechanism.
Figure 2: The spin-torsion oscillator.
Figure 3: The response of devices with and without the FM–NM interface.
Figure 4: Voltage response for the gold–cobalt sample.

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Acknowledgements

This work was primarily supported by the National Science Foundation (Division of Material Research (DMR)-0346707) under the NSF-European Community (EC) Cooperative Activity in Materials Research (Material World Network). S.K. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG) (Sonderforschungsbereich (SFB)668 B3 and DFG SFB508 B9). P.D. acknowledges support from the Condensed Matter Theory visitors program at Boston University, the Centre National de la Recherche Scientifique/Direction des Relations Internationales (CNRS/DREI) (contract no. 4024) and Agence Nationale pour la Recherche (ANR)-PNANO Quspin. The authors thank M. Johnson, I. Zutic, T. Wehling, J. Wei, L. Saminadayar, C. Bäuerle and C. Chamon for helpful discussions.

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Authors and Affiliations

  1. Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, 02215, Massachusetts, USA

    Guiti Zolfagharkhani, Pascal Degiovanni & Pritiraj Mohanty

  2. Department of Mechanical and Aerospace Engineering, Boston University, 110 Cummington Street, Boston, 02215, Massachusetts, USA

    Alexei Gaidarzhy

  3. Université de Lyon, Fédération de Physique André Marie Ampère, CNRS-Laboratoire de Physique de l'Ecole Normale, Supérieure de Lyon, 46 Allée d'Italie, Lyon Cedex 07, 69364, France

    Pascal Degiovanni

  4. Jacobs University Bremen, School of Engineering and Science, Campus Ring 1, Bremen, D-28759, Germany

    Stefan Kettemann

  5. Asia Pacific Centre for Theoretical Physics, Namgu Pohang, Gyeongbuk, 790-784, Korea

    Peter Fulde

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  1. Guiti Zolfagharkhani
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Contributions

All authors discussed the results and commented on the manuscript.

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Correspondence to Pritiraj Mohanty.

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Zolfagharkhani, G., Gaidarzhy, A., Degiovanni, P. et al. Nanomechanical detection of itinerant electron spin flip. Nature Nanotech 3, 720–723 (2008). https://doi.org/10.1038/nnano.2008.311

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