Flicker and random telegraph noise between gyrotropic and dynamic C-state of a vortex based spin torque nano oscillator

TL;DR

This paper investigates flicker and telegraph noise in vortex-based spin torque nano oscillators, revealing how stochastic transitions between dynamic states affect noise properties and potential applications in RF and neuromorphic computing.

Contribution

It provides experimental insights into noise behavior during state transitions in vortex STVOs, confirming theoretical predictions and exploring implications for device optimization.

Findings

Flicker noise increases with the square of the current when oscillation volume is constant.

Stochastic transitions between gyrotropic and C-states can be characterized by specific noise signatures.

The results suggest potential for noise control in RF and neuromorphic applications.

Abstract

Vortex based spin torque nano oscillators (STVOs) can present more complex dynamics than the spin torque induced gyrotropic (G) motion of the vortex core. The respective dynamic modes and the transition between them can be controlled by experimental parameters such as the applied dc current. An interesting behavior is the stochastic transition from the G- to a dynamic C-state occurring for large current densities. Moreover, the C-state oscillations exhibit a constant active magnetic volume. We present noise measurements in the different dynamic states that allow accessing specific properties of the stochastic transition, such as the characteristic state transition frequency. Furthermore,we confirm, as theoretically predicted, an increase of flicker noise with $I_{dc}^2$ when the oscillation volume remains constant with the current. These results bring insight into the potential optimization of noise properties sought for many potential rf applications with spin torque oscillators. Furthermore, the investigated stochastic characteristics open up new potentialities, for instance in the emerging field of neuromorphic computing schemes.