``Devil's staircase'' in nanomagnetism: fractional synchronization of a nonlinear spin-torque nano-oscillator

ORAL

Abstract

When an oscillator is driven by a periodic external force, the oscillation can become synchronized in a certain phase and frequency relationship with that force. At the main resonance, the frequency $f$ of the oscillation becomes equal to the frequency $f_{e}$ of the driving signal. An infinite number of synchronization regimes with rational values of $r=f_{e}$/$f$ (``Devil's staircase'') develop at large driving amplitudes. For magnetic nano-oscillators driven by spin transfer effect synchronization has been demonstrated only at the main resonance, when $f_{e}$ is close to the auto-oscillation frequency $f_{0}$. By using a new device geometry utilizing a microwave field as the driving force, we demonstrate the ``Devil's staircase'' in magnetic nano-oscillators. Analysis shows that fractional synchronization becomes possible only due to the simultaneous action of both the microwave magnetic field and the microwave current, and is characteristic of the complex nonlinear nature of the magnetic precession.

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Authors

  • Sergei Urazhdin

    Department of Physics, West Virginia University

  • Kurt Wiesenfeld

    Miami University, Summa Health System, Akron, John Carroll University, Prof, Dr, BfS, Germany, Florida State University, Monmouth College, Ohio Wesleyan University, Kenyon College, University of Cincinnati, Brookhaven National Lab, University of Wisconsin Oshkosh, Dept. of Chermical Engineering, Carnegie Mellon University, Cleveland State University, The Neurological Institute, Epilepsy Center, Department of Neurology, Cleveland Clinic, Un. of Stockholm, The University of Akron, Case Western Reserve University, West Virginia University, Kalamazoo College and Editor, American Journal of Physics, Denison University, University of Southern Florida, Johannes-Gutenberg-Universitat, BfS (Germany), Shanghai Jiao Tong University, Department of Physics, West Virginia University, Kansas State University, The Pennsylvania State University, University of Wisconsin-Oshkosh, Purdue University, Saint Jospeh's College, University of Washington, Indiana University, University of Potsdam, Georgia Institute of Technology

  • Andrei Slavin

    Department of Physics, Oakland University, Oakland University

  • Vasil Tiberkevich

    Department of Physics, Oakland University, Oakland University