Field-free magnetization reversal by spin-Hall effect and exchange bias

TL;DR

This paper demonstrates field-free magnetization reversal in perpendicular magnetic layers using spin-Hall effect and exchange bias, eliminating the need for external magnetic fields and advancing MRAM technology.

Contribution

The study introduces a novel method of achieving deterministic SHE-driven switching via interface engineering with antiferromagnetic materials, removing the need for external magnetic fields.

Findings

Successful field-free SHE-driven magnetization reversal.

Exchange bias enables deterministic switching in PMA devices.

Provides insights into spin structure at ferromagnetic/antiferromagnetic interfaces.

Abstract

Magnetic random-access memory (MRAM) driven by spin-transfer torque (STT) is a major contender for future memory applications. The energy dissipation involved in writing remains problematic, even with the advent of more efficient perpendicular magnetic anisotropy (PMA) devices. A promising alternative switching mechanism employs spin-orbit torques and the spin-Hall effect (SHE) in particular, but additional symmetry breaking is required to achieve deterministic switching in PMA devices. Currently used methods rely on in-plane magnetic fields or anisotropy gradients, which are not suitable for practical applications. Here, we interface the magnetic layer with an anti-ferromagnetic material. An in-plane exchange bias (EB) is created, and shown to enable field-free SHE-driven magnetization reversal of a perpendicularly magnetized Pt/Co/IrMn structure. Aside from the potential technological implications, our experiment provides additional insight into the local spin structure at the ferromagnetic/anti-ferromagnetic interface.