Mutual control of stochastic switching for two electrically coupled superparamagnetic tunnel junctions

TL;DR

This paper demonstrates how two superparamagnetic tunnel junctions can be mutually coupled via an electrical circuit, leading to correlated stochastic switching behavior useful for energy-efficient computing and cognitive applications.

Contribution

It introduces a simple linear circuit for coupling SMTJs and models their collective behavior using a Markov approach, advancing understanding of their interactions.

Findings

Coupling induces significant correlation between SMTJ states.

The Markov model accurately reproduces coupled device behavior.

Electrical coupling affects transition rates and collective dynamics.

Abstract

Superparamagnetic tunnel junctions (SMTJs) are promising sources for the randomness required by some compact and energy-efficient computing schemes. Coupling SMTJs gives rise to collective behavior that could be useful for cognitive computing. We use a simple linear electrical circuit to mutually couple two SMTJs through their stochastic electrical transitions. When one SMTJ makes a thermally induced transition, the voltage across both SMTJs changes, modifying the transition rates of both. This coupling leads to significant correlation between the states of the two devices. Using fits to a generalized N\'eel-Brown model for the individual thermally bistable magnetic devices, we can accurately reproduce the behavior of the coupled devices with a Markov model.