Switching Characteristics of Electrically Connected Stochastically Actuated Magnetic Tunnel Junction Nanopillars

TL;DR

This paper explores how electrically connected nanoscale magnetic tunnel junctions exhibit correlated stochastic switching behavior, which can be modeled and interpreted using concepts from statistical physics like the Ising model.

Contribution

It introduces a minimal stochastic model and Markov-chain formalism to describe coupled switching, revealing how simple electrical connections induce Ising-like interactions in nanoscale magnets.

Findings

Connected junctions show correlated switching due to circuit-mediated voltage redistribution.

The stochastic behavior can be modeled with a Markov-chain formalism.

Electrical connections induce tunable Ising-like spin-spin interactions.

Abstract

We investigate the stochastic dynamics of nanoscale perpendicular magnetic tunnel junctions (pMTJs) and the correlations that arise when they are electrically coupled. Individual junctions exhibit thermally activated spin-transfer torque switching with transition probabilities that are well described by a Poisson process. When two junctions are connected in parallel, circuit-mediated redistribution of voltages that occurs in real time as the junction resistances change leads to correlated switching behavior. A minimal stochastic model based on single-junction statistical switching properties and Kirchhoff's laws captures the coupled switching probabilities, while a Markov-chain formalism describes nonequilibrium steady states under multi-pulse driving. Further, these circuit-mediated interactions can be mapped onto the parameters of an Ising Hamiltonian, providing an interpretation in terms of effective spin-spin interactions. Our results demonstrate how simple electrical connections can generate Ising-like couplings and tunable stochastic dynamics in nanoscale magnets.