Optimal field-free magnetization switching via spin-orbit torque on the surface of a topological insulator

TL;DR

This paper develops an optimal, energy-efficient, field-free magnetization switching protocol on topological insulators using spin-orbit torque, with a focus on minimizing Joule heating and optimizing switching time.

Contribution

It introduces an analytically derived, optimal current protocol for magnetization switching on topological insulators, highlighting the advantages of tunable material properties and robustness.

Findings

Energy-efficient switching achieved with vanishing damping-like torque

Optimal reversal time balances speed and energy use

Topological insulators have similar switching costs to heavy metals

Abstract

We present an optimal field-free protocol for current-induced switching of a perpendicularly magnetized ferromagnetic insulator nanoelement on the surface of a topological insulator. The time dependence of in-plane components of the surface current, which drives the magnetization reversal via the Dirac spin-orbit torque with minimal Joule heating, is derived analytically as a function of the switching time and material properties. Our analysis identifies that energy-efficient switching is achieved for vanishing damping-like torque. The optimal reversal time that balances switching speed and energy efficiency is determined. When we compare topological insulators to heavy-metal systems, we find similar switching costs for the optimal ratio between the spin-orbit torque coefficients. However, topological insulators offer the advantage of tunable material properties. Finally, we propose a robust and efficient simplified switching protocol using a down-chirped rotating current pulse, tailored to realistic ferromagnetic/topological insulator systems.