Heat-Assisted Multiferroic Solid-State Memory

TL;DR

This paper proposes a heat-assisted multiferroic memory device that uses thermally activated strain-induced magnetisation switching, analyzed through a detailed temperature-dependent magnetisation dynamics model, demonstrating reliable switching conditions.

Contribution

It introduces a novel heat-assisted multiferroic memory design combining antiferroelectric substrates with magnetic layers, and provides a comprehensive model for magnetisation switching analysis.

Findings

Switching probability depends on stress and temperature.

Reliable switching occurs within specific stress and temperature ranges.

The model predicts operational regions for device design.

Abstract

A heat-assisted multiferroic solid-state memory design is proposed and analysed, based on a PbNbZrSnTiO3 antiferroelectric substrate and Ni81Fe19 magnetic free layer. Information is stored as magnetisation direction in the free layer of a magnetic tunnel junction element. The bit writing process is contactless and relies on triggering thermally activated magnetisation switching of the free layer towards a strain-induced anisotropy easy axis. A stress is generated using the antiferroelectric substrate by voltage-induced antiferroelectric to ferroelectric phase change, and this is transmitted to the magnetic free layer by strain-mediated coupling. The thermally activated strain-induced magnetisation switching is analysed here using a three-dimensional, temperature-dependent magnetisation dynamics model, based on simultaneous evaluation of the stochastic Landau Lifshitz Bloch equation and heat flow equation, together with stochastic thermal fields and magnetoelastic contributions. The magnetisation switching probability is calculated as a function of stress magnitude and maximum heat pulse temperature. An operating region is identified, where magnetisation switching always occurs, with stress values ranging from 80 to 180 MPa, and maximum temperatures normalised to the Curie temperature ranging from 0.65 to 0.99.