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Commensurability and chaos in magnetic vortex oscillations

Nature Physics volume 8, pages 682–687 (2012)Cite this article

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Abstract

Magnetic vortex dynamics in thin films is characterized by gyrotropic motion, the sense of gyration depending on the vortex core polarity, which reverses when a critical velocity is reached. Although self-sustained vortex oscillations in nanoscale systems are known to be possible, the precise role of core reversal in such dynamics remains unknown. Here we report on an experimental observation of periodic core reversal during self-sustained vortex gyration in a magnetic nanocontact system. By tuning the ratio between the gyration frequency and the rate of core reversal, we show that commensurate phase-locked and incommensurate chaotic states are possible, resulting in Devil’s staircases with driving currents. These systems could have the potential to serve as tunable nanoscale radiofrequency electrical oscillators for secure communications, allowing schemes such as encryption by chaos on demand.

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Figure 1: Schematic illustration of vortex dynamics in magnetic nanocontacts.
Figure 2: Experimental power spectrum of the nanocontact vortex oscillator.
Figure 3: Calculated power spectra from micromagnetics simulations.
Figure 4: Simulated Devil’s staircases and chaotic states.

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Acknowledgements

This work was partially supported by the European Commission, under contract numbers MRTN-CT-2006-035327 SPINSWITCH and MRTN-CT-2008-215368-2 SEMISPINNET, the French National Research Agency (ANR), within the VOICE project no ANR-09-NANO-006, the RTRA foundation ‘Triangle de la Physique’, under contract number 2007-051T, and the Flanders Research Foundation. The authors thank R. Guillemet, S. Fusil and C. Deranlot for their assistance during the growth and fabrication of the samples, and A. Dussaux for complementary experiments and discussions.

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Authors and Affiliations

  1. Institut d’Electronique Fondamentale, Université Paris-Sud, 91405 Orsay, France

    Sebastien Petit-Watelot, Joo-Von Kim, Ruben M. Otxoa & Thibaut Devolder

  2. UMR 8622, CNRS, 91405 Orsay, France

    Sebastien Petit-Watelot, Joo-Von Kim, Ruben M. Otxoa & Thibaut Devolder

  3. Unité Mixte de Physique CNRS/Thales and Université Paris-Sud, 1 avenue A. Fresnel, 91767 Palaiseau, France

    Antonio Ruotolo, Karim Bouzehouane, Julie Grollier & Vincent Cros

  4. Department of Physics and Materials Science, City University of Hong Kong, Kowloon, Hong Kong

    Antonio Ruotolo

  5. Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, B-9000 Ghent, Belgium

    Arne Vansteenkiste

  6. Department of Electrical Energy, Systems and Automation, Ghent University, Sint-Pietersnieuwstraat 41, B-9000 Ghent, Belgium

    Ben Van de Wiele

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  1. Sebastien Petit-Watelot
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Contributions

J-V.K., T.D., A.R., J.G. and V.C. designed the project, and V.C., T.D. and J-V.K. coordinated the project. K.B. fabricated the samples. T.D. designed and implemented the experimental set-up. A.R. and T.D. performed the high-frequency electrical measurements. T.D., A.R. and J-V.K. analysed the data. S.P-W., J-V.K., R.M.O. and T.D. interpreted the data and developed the model. A.V. and B.V.d.W. wrote the micromagnetics simulation code. J-V.K., S.P-W. and R.M.O. performed the simulations and interpreted the results. J-V.K. prepared the manuscript. All authors edited and commented on the manuscript.

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Correspondence to Joo-Von Kim.

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Petit-Watelot, S., Kim, JV., Ruotolo, A. et al. Commensurability and chaos in magnetic vortex oscillations. Nature Phys 8, 682–687 (2012). https://doi.org/10.1038/nphys2362

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