Spin-orbit torques in magnetic bilayers (Presentation Recording)

Spintronics aims to utilize the coupling between charge transport and magnetic dynamics to develop improved and novel memory and logic devices. Future progress in spintronics may be enabled by exploiting the spin-orbit coupling present at the interface between thin film ferromagnets and heavy metals. In these systems, applying an in-plane electrical current can induce magnetic dynamics in single domain ferromagnets, or can induce rapid motion of domain wall magnetic textures. There are multiple effects responsible for these dynamics. They include spin-orbit torques and a chiral exchange interaction (the Dzyaloshinskii-Moriya interaction) in the ferromagnet. Both effects arise from the combination of ferromagnetism and spin-orbit coupling present at the interface. There is additionally a torque from the spin current flux impinging on the ferromagnet, arising from the spin hall effect in the heavy metal. Using first principles calculations, we identify spin-orbit hybridization at the ferromagnet-heavy metal interface as central to the spin-orbit torques present in Co-Pt bilayers. We additionally propose that the transverse spin current (from the spin hall effect) is locally enhanced over its bulk value due to scattering at an interface which is oriented normal to the charge current direction.