Orbital Hall effect assisted field-free perpendicular magnetization switching

TL;DR

This paper demonstrates a novel method for field-free perpendicular magnetization switching using the orbital Hall effect to enhance spin-orbit torques, eliminating the need for external magnetic fields and enabling scalable spintronic devices.

Contribution

It introduces the use of the orbital Hall effect with a Mo underlayer to achieve efficient, field-free switching of perpendicular magnetization, advancing spintronics technology.

Findings

Orbital Hall effect amplifies damping-like torque via orbital-to-spin conversion.

Efficient field-free switching achieved without complex device geometries.

Scalable approach for high-speed, low-power spintronic applications.

Abstract

Spin-orbit torques (SOTs) generated through the conventional spin Hall effect (SHE) and/or Rashba-Edelstein effect offer potential for magnetization manipulation. However, deterministic switching of perpendicular ferromagnets via SOTs requires a strong symmetry-breaking perturbation, typically an external magnetic field. Here, we demonstrate that field-free SOT switching of perpendicular magnetization can be facilitated with the assistance of the orbital Hall effect (OHE). Using a representative Co/PtGd bilayer SOT device, we find that while the planar Hall effect (PHE) generates a finite out-of-plane damping-like torque, representing a lateral symmetry breaking, the SHE-induced torque achievable at practical current density is insufficient to switch the perpendicular magnetization. Incorporating a Mo underlayer and exploiting its strong OHE can amplify the in-plane damping-like torque via orbital-to-spin conversion, enabling efficient field-free deterministic switching without complex device geometries or low symmetric spin sources, providing a straightforward and scalable strategy for achieving high-speed and low-power spintronics.