Orbital torque and efficient magnetization switching using ultrathin Co|Al light-metal interfaces: Experiments and modeling

TL;DR

This paper explores how ultrathin Co|Al interfaces and Co/Pt/Al structures can generate orbital torques for magnetization switching, combining experimental investigations with theoretical modeling to understand orbital-momentum locking and orbital Rashba effects.

Contribution

It demonstrates the impact of ultrathin Pt layers on orbital properties at Co/Al interfaces and models the orbital response using density-functional theory and linear-response approaches.

Findings

Ultrathin Pt layers modify orbital polarization at Co/Al interfaces.

Orbital-momentum locking is observed in Co/Al systems.

Modeling confirms the role of orbital effects in magnetization control.

Abstract

The emergence of the orbital degree of freedom in modern orbitronics offers a promising alternative to heavy metals for the efficient control of magnetization. In this context, identifying interfaces that exhibit orbital-momentum locking and an orbital Rashba-Edelstein response to an external electric field is of primary importance. In this work, we experimentally investigate the Co/Al system and extend the study to Co/Pt/Al structures. We show that inserting ultrathin Pt layers between Co and Al can significantly modify the orbital properties, highlighting the critical role of Co/Al orbital bonding in generating orbital polarization. We further model the orbital response of these systems using semi-phenomenological approaches and linear-response theory within the framework of density-functional theory.