Field-free magnetization switching in SOT-MRAM devices with noncollinear antiferromagnets

Abstract

Spin-orbit torque magnetoresistive random access memory (SOT-MRAM) is a promising nonvolatile memory technology that offers fast writing speed, low power, and long endurance. However, achieving deterministic perpendicular magnetization switching typically requires an external field, limiting scalability. This work explores the incorporation of noncollinear antiferromagnetic (nc-AFMs), exhibiting the magnetic spin Hall effect (MSHE), and exchange bias to enable field-free deterministic switching. MSHE has been observed in Mn${}_3$Sn, MnPd${}_3$. The ratio of out-of-plane to in-plane polarized spin-currents is crucial for field-free MSHE-driven magnetization switching. It was found that a minimum ratio is needed to drive field-free perpendicular switching. Exchange bias acting at the interface between in-plane AFM and out-of-plane ferromagnet (FM) has been demonstrated to enable field-free SOT-driven magnetization switching. We show, that exchange bias can facilitate field-free perpendicular switching in cases of a missing or too small out-of-plane polarized spin current component. We present a fully three-dimensional finite element model that couples spin currents and magnetization dynamics to simulate SOT-MRAM devices utilizing the MSHE. We show that the use of nc-AFMs eliminates the need for external fields without compromising performance, simplifying design, and boosting scalability.