Simulated annealing with time-varying strain in a dipole-coupled array of magnetostrictive nanomagnets

TL;DR

This paper demonstrates experimentally how time-varying strain in magnetostrictive nanomagnets can emulate simulated annealing by allowing the system to escape metastable states and return to ground state, aiding optimization.

Contribution

It introduces an experimental method to emulate simulated annealing using strain in nanomagnet arrays, a novel hardware approach for optimization.

Findings

Time-varying strain erodes energy barriers in nanomagnets.

Nanomagnet arrays can be driven from metastable to ground state.

Experimental validation of strain-induced simulated annealing.

Abstract

In a two-dimensional arrangement of closely spaced elliptical nanomagnets with in-plane magnetic anisotropy, whose major axes are aligned along columns and minor axes along rows, dipole coupling will make the magnetic ordering "ferromagnetic" along the columns and "anti-ferromagnetic" along the rows. Noise and other perturbations can drive the system out of this ground state configuration and pin it in a metastable state where the magnetization orientations will not follow this pattern. Internal energy barriers, sufficiently larger than the thermal energy kT, will prevent the system from leaving the metastable state and decaying spontaneously to the ground state. These barriers can be temporarily eroded by globally straining the nanomagnets with time-varying strain if the nanomagnets are magnetostrictive, which will allow the system to return to ground state after strain is removed. This is a hardware emulation of simulated annealing in an interacting many body system. Here, we demonstrate this function experimentally.