Understanding of phase noise squeezing under fractional synchronization of non-linear spin transfer vortex oscillator

TL;DR

This paper explores phase noise reduction in spin transfer vortex oscillators through fractional synchronization, demonstrating record low phase noise levels and highlighting the importance of symmetry and nonlinear effects.

Contribution

It provides experimental and theoretical insights into phase locking mechanisms, achieving a record phase noise reduction in vortex-based spin transfer oscillators.

Findings

Record phase noise reduction to -90dBc/Hz at 1 kHz offset

Synchronization at multiple fractional frequencies achieved

Symmetries and nonlinearities critically influence locking process

Abstract

We investigate experimentally the synchronization of a vortex based spin transfer oscillator to an external rf current whose frequency is at multiple integers, as well as half integer, of the oscillator frequency. Through a theoretical study of the locking process, we highlight both the crucial role of the symmetries of the spin torques acting on the magnetic vortex and the nonlinear properties of the oscillator on the phase locking process. Through the achievement of a perfect injection locking state, we report a record phase noise reduction down to -90dBc/Hz at 1 kHz offset frequency. The phase noise of these nanoscale oscillators is demonstrating as being low and controllable which is of significant importance for real applications using spin transfer devices.