# Lack of correlation between the spin mixing conductance and the ISHE-generated voltages in CoFeB/Pt,Ta bilayers

## TL;DR

This study examines spin pumping in CoFeB/Pt and CoFeB/Ta bilayers, revealing no correlation between spin mixing conductance and ISHE voltages, highlighting the influence of magnetic proximity effects and spin rectification.

## Contribution

It demonstrates the lack of correlation between spin mixing conductance and ISHE voltages, emphasizing the role of magnetic proximity effects in these bilayers.

## Key findings

- Anomalous Hall effect dominates spin rectification in CoFeB.
- No correlation between $g^{\uparrow\downarrow}_{eff}$ and ISHE voltages.
- Linear dependence of damping on Pt thickness.

## Abstract

We investigate spin pumping phenomena in polycrystalline CoFeB/Pt and CoFeB/Ta bilayers and the correlation between the effective spin mixing conductance $g^{\uparrow\downarrow}_{\rm eff}$ and the obtained voltages generated by the spin-to-charge current conversion via the inverse spin Hall effect in the Pt and Ta layers. For this purpose we measure the in-plane angular dependence of the generated voltages on the external static magnetic field and we apply a model to separate the spin pumping signal from the one generated by the spin rectification effect in the magnetic layer. Our results reveal a dominating role of anomalous Hall effect for the spin rectification effect with CoFeB and a lack of correlation between $g^{\uparrow\downarrow}_{\rm eff}$ and inverse spin Hall voltages pointing to a strong role of the magnetic proximity effect in Pt in understanding the observed increased damping. This is additionally reflected on the presence of a linear dependency of the Gilbert damping parameter on the Pt thickness.