  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.
