Spin-orbit torque switching of synthetic antiferromagnets

TL;DR

This paper demonstrates that synthetic antiferromagnets can be switched by spin-orbit torques through a novel mechanism involving asymmetric domain expansion, challenging traditional models and offering new application possibilities.

Contribution

It introduces a new switching mechanism based on field-modulated domain wall motion, diverging from the macrospin model, and explains anomalous switching behaviors in SAFs.

Findings

Both positive and negative SHA-like switching observed with only positive SHA.

Switching direction is dominated by domain wall motion, not SHA sign.

Domain wall motion measurements confirm the new mechanism.

Abstract

We report that synthetic antiferromagnets (SAFs) can be efficiently switched by spin-orbit torques (SOTs) and the switching scheme does not obey the usual SOT switching rule. We show that both the positive and negative spin Hall angle (SHA)-like switching can be observed in Pt/SAF structures with only positive SHA, depending on the strength of applied in-plane fields. A new switching mechanism directly arising from the asymmetric domain expansion is proposed to explain the anomalous switching behaviors. Contrary to the macrospin-based switching model that the SOT switching direction is determined by the sign of SHA, the new switching mechanism suggests that the SOT switching direction is dominated by the field-modulated domain wall motion and can be reversed even with the same sign of SHA. The new switching mechanism is further confirmed by the domain wall motion measurements. The anomalous switching behaviors provide important insights for understanding SOT switching mechanisms and also offer novel features for applications.