Anomalous spin–orbit torques in magnetic single-layer films

Wenrui Wang, Tao Wang, Vivek P. Amin, Yang Wang, Anil Radhakrishnan, Angie Davidson, Shane R. Allen, T. J. Silva, Hendrik Ohldag, Davor Balzar, Barry L. Zink, Paul M. Haney, John Q. Xiao, David G. Cahill, Virginia O. Lorenz, Xin Fan

Research output: Contribution to journalLetter

Abstract

The spin Hall effect couples charge and spin transport1–3, enabling electrical control of magnetization4,5. A quintessential example of spin-Hall-related transport is the anomalous Hall effect (AHE)6, first observed in 1880, in which an electric current perpendicular to the magnetization in a magnetic film generates charge accumulation on the surfaces. Here, we report the observation of a counterpart of the AHE that we term the anomalous spin–orbit torque (ASOT), wherein an electric current parallel to the magnetization generates opposite spin–orbit torques on the surfaces of the magnetic film. We interpret the ASOT as being due to a spin-Hall-like current generated with an efficiency of 0.053 ± 0.003 in Ni80Fe20, comparable to the spin Hall angle of Pt7. Similar effects are also observed in other common ferromagnetic metals, including Co, Ni and Fe. First-principles calculations corroborate the order of magnitude of the measured values. This work suggests that a strong spin current with spin polarization transverse to the magnetization can be generated within a ferromagnet, despite spin dephasing8. The large magnitude of the ASOT should be taken into consideration when investigating spin–orbit torques in ferromagnetic/non-magnetic bilayers.

Original languageEnglish (US)
Pages (from-to)819-824
Number of pages6
JournalNature Nanotechnology
Volume14
Issue number9
DOIs
StatePublished - Sep 1 2019

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ASJC Scopus subject areas

  • Bioengineering
  • Atomic and Molecular Physics, and Optics
  • Biomedical Engineering
  • Materials Science(all)
  • Condensed Matter Physics
  • Electrical and Electronic Engineering

Cite this

Wang, W., Wang, T., Amin, V. P., Wang, Y., Radhakrishnan, A., Davidson, A., Allen, S. R., Silva, T. J., Ohldag, H., Balzar, D., Zink, B. L., Haney, P. M., Xiao, J. Q., Cahill, D. G., Lorenz, V. O., & Fan, X. (2019). Anomalous spin–orbit torques in magnetic single-layer films. Nature Nanotechnology, 14(9), 819-824. https://doi.org/10.1038/s41565-019-0504-0