Frequency shift keying in vortex-based spin torque oscillators

TL;DR

This paper demonstrates frequency shift keying modulation in vortex-based spin torque oscillators, showing rapid, phase-coherent frequency transitions and highlighting their potential for RF circuit applications.

Contribution

It introduces the implementation of FSK modulation in vortex oscillators, demonstrating fast, phase-coherent frequency switching and advancing their use in RF technology.

Findings

Frequency follows current command with clear spectral swapping.

Transitions are phase coherent and under 25 ns.

Oscillators exhibit multi-octave tunability and high agility.

Abstract

Vortex-based spin-torque oscillators can be made from extended spin valves connected to an electrical nanocontact. We study the implementation of frequency shift keying modulation in these oscillators. Upon a square modulation of the current in the 10 MHz range, the vortex frequency follows the current command, with easy identification of the two swapping frequencies in the spectral measurements. The frequency distribution of the output power can be accounted for by convolution transformations of the dc current vortex waveform, and the current modulation. Modeling indicates that the frequency transitions are phase coherent and last less than 25 ns. Complementing the multi-octave tunability and first-class agility, the capability of frequency shift keying modulation is an additional milestone for the implementation of vortex-based oscillators in RF circuit.