Regensburg 2025 – scientific programme

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MA: Fachverband Magnetismus

MA 11: Spin Transport and Orbitronics, Spin-Hall Effects I (joint session MA/TT)

MA 11.2: Talk

Tuesday, March 18, 2025, 09:45–10:00, H18

Optimization of orbital torques in ferrimagnets and their relationship with Gilbert damping — •shilei ding, william legrand, hanchen wang, mingu kang, paul noel, and pietro gambardella — Department of Materials, ETH Zurich, 8093 Zurich, Switzerland

Application of an electric field can induce a non-equilibrium orbital angular momentum in conductive materials whose electronic bands have a k-dependent orbital character. This phenomenon can lead to the current-induced accumulation of orbital momenta in nonmagnetic layers, which can then diffuse into neighboring magnetic layers and interact with the local magnetization through spin-orbit coupling, giving rise to orbital torques. Conversely, the excitation of spin precession in a magnetic layer can give rise to an orbital current, resulting in orbital pumping and dissipation of angular momentum in the nonmagnetic layer. In the first part, I will present the efficacy of converting orbital to spin momenta in ferrimagnetic materials, specifically in the RE-TM ferrimagnet GdyCo100-y. This work underscores the mechanisms that facilitate orbital-to-spin conversion within a magnetic layer at the atomic level. In the second part, I will discuss how the Gilbert damping parameter correlates to spin and orbital torques in magnetic layers adjacent to Pt and CuOx layers, respectively. I will show that CoFe/CuOx bilayers exhibit a favorable combination of efficient orbital torque and minimal increase in Gilbert damping, which is promising for the implementation of orbital torque oscillators with reduced damping compared to spin torque oscillators.

Keywords: Orbital torque; Orbital-to-spin conversion; Gilbert damping