Spin-orbit torque in completely compensated synthetic antiferromagnet

TL;DR

This study demonstrates that synthetic antiferromagnets with complete compensation can be efficiently switched using spin-orbit torque, potentially enabling high-density, high-speed, low-power magnetic memory devices.

Contribution

It provides the first experimental and theoretical analysis of spin-orbit torque in completely compensated SAF structures, showing enhanced torque efficiency over ferromagnetic systems.

Findings

Magnetizations switch simultaneously between antiparallel states.

Switching efficiency is higher than in ferromagnetic counterparts.

Critical switching current is comparable to single ferromagnets.

Abstract

Synthetic antiferromagnets (SAF) have been proposed to replace ferromagnets in magnetic memory devices to reduce the stray field, increase the storage density and improve the thermal stability. Here we investigate the spin-orbit torque in a perpendicularly magnetized Pt/[Co/Pd]/Ru/[Co/Pd] SAF structure, which exhibits completely compensated magnetization and an exchange coupling field up to 2100 Oe. The magnetizations of two Co/Pd layers can be switched between two antiparallel states simultaneously by spin-orbit torque. The magnetization switching can be read out due to much stronger spin-orbit coupling at bottom Pt/[Co/Pd] interface compared to its upper counterpart without Pt. Both experimental and theoretical analyses unravel that the torque efficiency of antiferromagnetic coupled stacks is significantly higher than the ferromagnetic counterpart, making the critical switching current of SAF comparable to the conventional single ferromagnet. Besides adding an important dimension to spin-orbit torque, the efficient switching of completely compensated SAF might advance magnetic memory devices with high density, high speed and low power consumption.