Van der Waals Spin-Orbit Torque Antiferromagnetic Memory

TL;DR

This paper proposes a van der Waals antiferromagnetic memory device utilizing a LaBr2/WTe2 bilayer, demonstrating low critical current, rapid switching, and high magnetoresistance for efficient, field-free magnetic memory applications.

Contribution

It introduces a novel vdW bilayer device combining LaBr2 and WTe2, achieving low power, fast, and reliable antiferromagnetic memory switching with high magnetoresistance.

Findings

Critical current density ~10 MA/cm²

Switching time of 250 ps

Tunnel magnetoresistance ratio up to 4250%

Abstract

The technique of conventional ferromagnet/heavy-metal spin-orbit torque (SOT) offers significant potential for enhancing the efficiency of magnetic memories. However, it faces fundamental physical limitations, including hunting effects from the metallic layer, broken symmetry for enabling antidamping switching, spin scattering caused by interfacial defects, and sensitivity to stray magnetic fields. To address these issues, we here propose a van der Waals (vdW) field-free SOT antiferromagnetic memory using a vdW bilayer LaBr$_2$ (an antiferromagnet with perpendicular magnetic anisotropy) and a monolayer T$_d$ phase WTe$_2$ (a Weyl semimetal with broken inversion symmetry). By systematically employing density functional theory in conjunction with non-equilibrium Green's function methods and macrospin simulations, we demonstrate that the proposed vdW SOT devices exhibit remarkably low critical current density approximately 10 MA/cm$^2$ and rapid field-free magnetization switching in 250 ps. This facilitates excellent write performance with extremely low energy consumption. Furthermore, the device shows a significantly low read error rate, as evidenced by a high tunnel magnetoresistance ratio of up to 4250%. The superior write and read performance originates from the unique strong on-site (insulating phase) and off-site (magnetic phase) Coulomb interactions in electride LaBr$_2$, a large non-zero z-component polarization in WTe$_2$, and the proximity effect between them.