Super-harmonic injection locking of nano-contact spin-torque vortex oscillators

Abstract

Super-harmonic injection locking of single nano-contact (NC) spin-torque vortex oscillators (STVOs) subject to a small microwave current has been explored. Frequency locking was observed up to the fourth harmonic of the STVO fundamental frequency $f_0$ in microwave magneto-electronic measurements. The large frequency tunability of the STVO with respect to $f_0$ allowed the device to be locked to multiple sub-harmonics of the microwave frequency $f_{RF}$, or to the same sub-harmonic over a wide range of $f_{RF}$ by tuning the DC current. In general, analysis of the locking range, linewidth, and amplitude showed that the locking efficiency decreased as the harmonic number increased, as expected for harmonic synchronization of a non-linear oscillator. Time-resolved scanning Kerr microscopy (TRSKM) revealed significant differences in the spatial character of the magnetization dynamics of states locked to the fundamental and harmonic frequencies, suggesting significant differences in the core trajectories within the same device. Super-harmonic injection locking of a NC-STVO may open up possibilities for devices such as nanoscale frequency dividers, while differences in the core trajectory may allow mutual synchronisation to be achieved in multi-oscillator networks by tuning the spatial character of the dynamics within shared magnetic layers.

21 pages, 8 figures

References in corpus (5)

• Current-driven vortex oscillations in metallic nanocontacts
• Dynamics of Pinned Magnetic Vortices
• Phase locking dynamics of dipolarly coupled vortex-based spin transfer oscillators
• Understanding of phase noise squeezing under fractional synchronization of non-linear spin transfer vortex oscillator
• Direct observation of magnetization dynamics generated by nano-contact spin-torque vortex oscillators

Cited by in corpus (6)

• Chaos in Magnetic Nanocontact Vortex Oscillators
• Optomechanical Synchronization across Multi-Octaves Frequency Spans
• A platform for time-resolved scanning Kerr microscopy in the near-field
• Magnetic Droplet Soliton Nucleation in Oblique Fields
• Enhancing the injection locking range of spin torque oscillators through mutual coupling
• Injection locking at fractional frequencies of magnetic tunnel junction (MTJ)-based read sensors' ferromagnetic resonance modes