Mitigation of Gilbert Damping in the CoFe/CuOx Orbital Torque System

Abstract

Charge-spin interconversion processes underpin the generation of spin-orbit torques in magnetic/nonmagnetic bilayers. However, efficient sources of spin currents such as 5d metals are also efficient spin sinks, resulting in a large increase of magnetic damping. Here we show that a partially-oxidized 3d metal can generate a strong orbital torque without a significant increase in damping. Measurements of the torque efficiency ξ and Gilbert damping α in CoFe/CuOx and CoFe/Pt indicate that ξ is comparable. The increase in damping relative to a single CoFe layer is Δα<0.002 in CoFe/CuOx and Δα ~ 0.005 - 0.02 in CoFe/Pt, depending on CoFe thickness. We ascribe the nonreciprocal relationship between Δα and ξ in CoFe/CuOx to the small orbital-to-spin current ratio generated by magnetic resonance in CoFe and the lack of an efficient spin sink in CuOx. Our findings provide new perspectives on the efficient excitation of magnetization dynamics via the orbital torque.

References in corpus (13)

• Study of Intrinsic Spin Hall Effect and Orbital Hall Effect in 4d- and 5d- Transition Metals
• Giant Orbital Hall Effect in Transition Metals: Origin of Large Spin and Anomalous Hall Effects
• Orbitronics: Orbital Currents in Solids
• Interface enhancement of Gilbert damping from first-principles
• Giant orbital Hall effect and orbital-to-spin conversion in 3d, 5d, and 4f metallic heterostructures
• Magnetization oscillations and waves driven by pure spin currents
• Orbital Rashba effect in surface oxidized Cu film
• Spin-orbit torque switching of magnetic tunnel junctions for memory application
• Giant anisotropy of Gilbert damping in epitaxial CoFe films
• Orbital Torque in Rare-Earth Transition-Metal Ferrimagnets
• Spin-Motive Forces and Current-Induced Torques in Ferromagnets
• Unidirectional orbital magnetoresistance in light metal/ferromagnet bilayers
• Calculating the spin memory loss at Cu$|$metal interfaces from first principles