Agility of vortex-based nanocontact spin torque oscillators

TL;DR

This paper demonstrates that vortex-based nanocontact spin torque oscillators can rapidly switch frequencies with high agility, making them promising for modulation-based RF applications.

Contribution

It provides experimental evidence of high agility and fast frequency switching in vortex-based spin torque oscillators, confirming theoretical predictions.

Findings

Oscillators can switch frequencies in less than ten periods.

Frequency tuning occurs at constant orbital radius.

Oscillators exhibit 25% frequency difference switching.

Abstract

We study the agility of current-tunable oscillators based on a magnetic vortex orbiting around a point contact in spin-valves. Theory predicts frequency-tuning by currents occurs at constant orbital radius, so an exceptional agility is anticipated. To test this, we have inserted an oscillator in a microwave interferometer to apply abrupt current variations while time resolving its emission. Using frequency shift keying, we show that the oscillator can switch between two stabilized frequencies differing by 25% in less than ten periods. With a wide frequency tunability and a good agility, such oscillators possess desirable figures of merit for modulation-based rf applications.