Tunability versus deviation sensitivity in a non-linear vortex oscillator

TL;DR

This paper investigates the frequency modulation behavior of a spin torque vortex oscillator, highlighting the importance of deviation sensitivity over tunability in understanding its dynamic response.

Contribution

It introduces deviation sensitivity as a key parameter, distinguishing it from traditional tunability, and analyzes its impact on the oscillator's frequency response.

Findings

Deviation sensitivity significantly influences intermodulation products.

Response time determines the difference between deviation sensitivity and tunability.

Experimental results show distinct behaviors in quasi-steady and transient regimes.

Abstract

Frequency modulation experiments were performed on a spin torque vortex oscillator for a wide range of modulation frequency, up to 10 % of the oscillator frequency. A thorough analysis of the intermodulation products shows that the key parameter that describes these experiments is the deviation sensitivity, which is the dynamical frequency-current dependence. It differs significantly from the oscillator tunability discussed so far in the context of spin-transfer oscillators. The essential difference between these two concepts is related to the response time of the vortex oscillator, driven either in quasi-steady state or in a transient regime.