Phase locking of vortex based spin transfer oscillators to a microwave current

TL;DR

This paper demonstrates phase locking, frequency pulling, and fractional synchronization in vortex-based spin transfer oscillators with external microwave currents, achieving large locking ranges and simultaneous locking of two oscillators.

Contribution

It provides experimental evidence of phase locking phenomena and large locking ranges in vortex-based spin transfer oscillators, including simultaneous locking of multiple devices.

Findings

Minimum linewidth of 3 kHz in locked state

Locking ranges up to 1/3 of oscillator frequency

Successful simultaneous locking of two oscillators

Abstract

Phase locking experiments on vortex based spin transfer oscillators with an external microwave current are performed. We present clear evidence of phase locking, frequency pulling, as well as fractional synchronization in this system, with a minimum peak linewidth of only 3 kHz in the locked state. We find that locking ranges of the order of 1/3 of the oscillator frequency are easily achievable because of the large tunability $\partial f/\partial I_{dc}$ observed in our vortex based systems. Such large locking ranges allow us to demonstrate the simultaneous phase locking of two independent oscillators connected in series with the external source.