Spin orbit torque controlled stochastic oscillators with synchronization and frequency tunability

TL;DR

This paper demonstrates a low-power stochastic oscillator using nanomagnets that can synchronize with weak signals and have tunable frequencies, leveraging spin orbit torque and thermal noise.

Contribution

It introduces a novel spin orbit torque controlled stochastic oscillator with tunable synchronization frequency and significantly reduced power consumption.

Findings

Successful phase synchronization to weak periodic signals

Frequency tunability via electrical feedback control

Synchronization current is over 8 times lower than deterministic switching

Abstract

Stochastic oscillators based on emerging nanodevices are attractive because of their ultra-low power requirement and ability to exhibit stochastic resonance, a phenomenon where synchronization to weak input signals is enabled due to ambient noise. In this work, a low barrier nanomagnet based stochastic oscillator is demonstrated, whose output jumps spontaneously between two states by harnessing the ambient thermal noise, requiring no additional power. Utilizing spin orbit torque in a three terminal device configuration, phase synchronization of these oscillators to weak periodic drives of particular frequencies is demonstrated. Experiments are performed to show the tunability of this synchronization frequency by controlling an electrical feedback parameter. The current required for synchronization is more than 8 times smaller than that required for deterministic switching of similar nanomagnetic devices. A model based on Kramers' transition rate in a symmetric double well potential is adopted and dynamical simulations are performed to explain the experimental results.