Improved spectral stability in spin transfer nano-oscillators: single vortex versus coupled vortices dynamics

TL;DR

This study compares the spectral stability of spin transfer nano-oscillators with uniform and vortex spin polarizers, revealing that coupled vortex dynamics significantly enhance phase stability and reduce linewidth.

Contribution

It demonstrates that excitation of coupled vortex dynamics via spin transfer torques improves spectral stability in nano-oscillators, a novel insight for device optimization.

Findings

Linewidth reduced by an order of magnitude to 200kHz

Vortex polarizer yields stronger phase stability

Coupled vortex dynamics are key to improved spectral performance

Abstract

We perform a comparative study of spin transfer induced excitation of the gyrotropic motion of a vortex core with either uniform or vortex spin polarizers. The microwave output voltage associated with the vortex dynamics, detected in both cases, displays a strong reduction of phase fluctuations in the case of the vortex polarizer, with a decrease of the peak linewidth by one order of magnitude down to 200kHz at zero field. A thorough study of rf emission features for the different accessible vortex configurations shows that this improvement is related to the excitation of coupled vortex dynamics by spin transfer torques.