Unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic layer heterostructures

TL;DR

This paper reports the observation of unidirectional spin Hall magnetoresistance in topological insulator/ferromagnetic heterostructures, enabling efficient two-terminal spintronic devices with performance comparable to existing metal-based systems.

Contribution

It demonstrates unidirectional spin Hall magnetoresistance in topological insulator/ferromagnet devices, offering a new two-terminal geometry for spintronics.

Findings

Unidirectional spin Hall magnetoresistance observed in TI/FM heterostructures.

Device performance comparable to high-end metal bilayers.

Potential for simplified two-terminal spintronic devices.

Abstract

The large spin orbit coupling in topological insulators results in helical spin-textured Dirac surface states that are attractive for topological spintronics. These states generate an efficient spin-orbit torque on proximal magnetic moments at room temperature. However, memory or logic spin devices based upon such switching require a non-optimal three terminal geometry, with two terminals for the writing current and one for reading the state of the device. An alternative two terminal device geometry is now possible by exploiting the recent discovery of a unidirectional spin Hall magnetoresistance in heavy metal/ferromagnet bilayers and (at low temperature) in magnetically doped topological insulator heterostructures. We report the observation of unidirectional spin Hall magnetoresistance in a technologically relevant device geometry that combines a topological insulator with a conventional ferromagnetic metal. Our devices show a figure-of-merit (magnetoresistance per current density per total resistance) that is comparable to the highest reported values in all-metal Ta/Co bilayers.