Extremely Coherent Microwave Emission from Spin Torque Oscillator Stabilized by Phase Locked Loop.

Area of Science:

• Spintronics
• Microwave Engineering
• Solid-State Electronics

Background:

• Spin torque oscillators (STOs) are promising for next-generation microwave signal sources.
• High phase noise in free-running STOs limits their practical application.
• Stabilization methods for STOs are crucial for widespread adoption.

Purpose of the Study:

• To demonstrate a phase-locked loop (PLL) for stabilizing STO microwave signals.
• To reduce the phase noise of STO-generated signals for practical use.
• To enable STOs in advanced electronic systems requiring stable microwave frequencies.

Main Methods:

• Implemented a phase-locked loop (PLL) circuit.
• Utilized a spin torque oscillator (STO) as a voltage-controlled oscillator (VCO).
• Stabilized a 7.344 GHz STO signal using a 153 MHz reference signal.

Main Results:

• Successfully achieved phase locking between the STO signal and the reference signal.
• Measured an extremely narrow oscillation peak linewidth (< 1 Hz).
• Demonstrated significant reduction in phase noise, meeting practical application requirements.

Conclusions:

• The implemented PLL effectively stabilizes STO oscillations.
• This work represents a major breakthrough for practical STO applications.
• The stabilized STO is suitable for advanced microwave electronics.