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Self-Injection Locking of a Vortex Spin Torque Oscillator by Delayed Feedback.
Sumito Tsunegi1,2, Eva Grimaldi2, Romain Lebrun2
1National Institute of Advanced Industrial Science and Technology (AIST), Spintronics Research Center, Tsukuba, Japan.
Scientific Reports
|June 1, 2016
Summary
This study shows how delaying radiofrequency (rf) current in spin torque oscillators improves performance. Optimal delays and phase differences enhance power and spectral linewidth, crucial for spintronics.
Area of Science:
- Spintronics
- Nonlinear Dynamics
- Microwave Engineering
Background:
- Spin torque oscillators (STOs) are key components in spintronics.
- Controlling STO dynamics is essential for advanced applications.
- Self-synchronization phenomena in STOs are not fully understood.
Purpose of the Study:
- To experimentally investigate the self-synchronization of spin torque oscillators.
- To explore the impact of delayed radiofrequency (rf) current re-injection on STO performance.
- To understand the role of phase difference in the self-injection regime.
Main Methods:
- Experimental setup involving re-injecting the STO's rf current after a controlled delay.
- Varying the delay time and phase difference between emitted and re-injected rf currents.
- Analyzing integrated power, spectral linewidth, frequency, and phase dynamics.
Main Results:
- Optimal delay times were found to improve integrated power and spectral linewidth.
- A clear 2π periodic oscillatory dependence of frequency, power, and linewidth on phase difference was observed.
- The experimental results align well with a general model of nonlinear auto-oscillators with delayed feedback.
Conclusions:
- Delayed rf current re-injection offers a method to control STO dynamics.
- This control enhances STO performance metrics like power and linewidth.
- Findings pave the way for improved rf spintronics and neuro-inspired devices.
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