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

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 Idc2 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.

Automated summary

Vortex based spin torque nano oscillators (STVOs) exhibit complex dynamics compared to gyrotropic motion, with dynamic modes and transitions controlled by experimental parameters. A stochastic transition from G-to-C state was observed at high current densities, with constant active magnetic volume in C-state oscillations. Noise measurements revealed insight into state transition frequency and an increase in flicker noise with constant oscillation volume. These results offer potential for optimizing noise properties in rf applications and exploring new possibilities in neuromorphic computing schemes.