Extraction of two-magnon scattering and detection of inverse spin Hall effect up to 40 GHz in low-damping Fe₆₅Co₃₅/Pt bilayer thin film

Abstract We report an investigation of the inverse spin Hall effect (ISHE), as a measure of the pure spin current ( J S ), induced by spin pumping in a Fe 65 Co 35 /Pt bilayer using coplanar waveguide ferromagnetic resonance (CPW-FMR) in the in-plane (IP) geometry over the broadband microwave frequency range of 8–40 GHz. From the IP-FMR measurements, the defect-induced two-magnon scattering (TMS) contribution is evaluated by analyzing the frequency dependence of FMR linewidth using Arias and Mills approach [Arias R and Mills D L (1999 Phys. Rev. B 60 , 7395), Mills D L and Arias R (2006 Physica B 384 147–151)]. Here, we have determined a very low Gilbert damping constant ( α G ) for Fe 65 Co 35 bare film around 1.3 × 10 −3 , which is essential for the high spin current (&gt;10 7 A/m 2 ) generation. The enhanced value of α G ≈3.2 × 10 −3 obtained for Fe 65 Co 35 /Pt bilayer film is due to spin pumping damping, α SP = 1.9 × 10 −3 , confirmed by the ISHE induced DC voltage ( V DC ) signal measured across the edges of Pt layer. Out-of-plane (OP) angular ISHE measurements have been performed to disentangle spin pumping from spin rectification effects in the V DC signal. Further, we evaluated the effective spin-mixing conductance <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>g</mml:mi> </mml:mrow> <mml:mrow> <mml:mi mathvariant="italic">eff</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>↑</mml:mo> <mml:mo>↓</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> = 3.33 × 10 19 m −2 , which is higher than the values reported in FeCo-alloy-based bilayer systems. The present study aims to detect the J S injected by low-damping Fe 65 Co 35 thin films, leading to the realization of energy-efficient spintronic devices.