Noise-enhanced synchronization of stochastic magnetic oscillators

TL;DR

This paper experimentally demonstrates that a stochastic magnetic oscillator can be synchronized to an external periodic current, reducing phase diffusion even with frequency mismatch, using a magnetic tunnel junction with a superparamagnetic free layer.

Contribution

The study shows for the first time that phase-locking can be achieved in a superparamagnetic magnetic tunnel junction driven by spin torques, highlighting robustness against frequency mismatch.

Findings

Synchronization occurs at current densities below 3×10^6 A/cm².

Injection-locking reduces phase diffusion significantly.

Synchronization is possible for input frequencies below the oscillator's mean frequency.

Abstract

We present an experimental study of phase-locking in a stochastic magnetic oscillator. The system comprises a magnetic tunnel junction with a superparamagnetic free layer, whose magnetization dynamics is driven with spin torques through an external periodic driving current. We show that synchronization of this stochastic oscillator to the input current is possible for current densities below $3 \times 10^6$ A/cm$^2$, and occurs for input frequencies lower than the natural mean frequency of the stochastic oscillator. We show that such injection-locking is robust and leads to a drastic reduction in the phase diffusion of the stochastic oscillator, despite the presence of a frequency mismatch between the oscillator and the excitation.