Spin pumping and inverse spin Hall effect in CoFeB/C$_{60}$ bilayers

TL;DR

This study investigates spin pumping and inverse spin Hall effect in CoFeB/C60 bilayers, revealing a spin Hall angle of 0.055, and explores organic semiconductors as promising materials for spintronic devices due to their low SOC and long spin diffusion length.

Contribution

First experimental demonstration of spin pumping and ISHE in CoFeB/C60 bilayers, including measurement of spin Hall angle and analysis of spin rectification effects.

Findings

Measured spin Hall angle of 0.055 in C60

Disentangled spin rectification effects from ISHE signals

Provided insights into organic semiconductors for spintronics

Abstract

Pure spin current based research is mostly focused on ferromagnet (FM)/heavy metal (HM) system. Because of the high spin orbit coupling (SOC) these HMs exhibit short spin diffusion length and therefore possess challenges for device application. Low SOC (elements of light weight) and large spin diffusion length make the organic semiconductors (OSCs) suitable for future spintronic applications. From theoretical model it is explained that, due to $\pi$ - $\sigma$ hybridization the curvature of the C$_{60}$ molecules may increase the SOC strength. Here, we have investigated spin pumping and inverse spin hall effect (ISHE) in CoFeB/C$_{60}$ bilayer system using coplanar wave guide based ferromagnetic resonance (CPW-FMR) set-up. We have performed angle dependent ISHE measurement to disentangle the spin rectification effects for example anisotropic magnetoresistance, anomalous Hall effect etc. Further, effective spin mixing conductance (g$_{eff}^{\uparrow\downarrow}$) and spin Hall angle ($\theta_{SH}$) for C$_{60}$ have been reported here. The evaluated value for $\theta_{SH}$ is 0.055.