# Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device

## TL;DR

This study measures the anomalous spin Hall angle in CoFe using a multiterminal device, revealing a negative anomalous spin Hall angle and contrasting with other ferromagnetic metals.

## Contribution

First direct measurement of the anomalous spin Hall angle in CoFe using a multiterminal spin injection/detection device.

## Key findings

- CoFe exhibits a negative anomalous spin Hall angle.
- The ordinary spin Hall angle in CoFe is negligible.
- Results differ from those of Co and permalloy.

## Abstract

We report on the determination of the anomalous spin Hall angle in the ferromagnetic metal alloy cobalt-iron (Co$_{25}$Fe$_{75}$, CoFe). This is accomplished by measuring the spin injection/detection efficiency in a multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto the magnetic insulator yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$, YIG). Applying a spin-resistor model to our multiterminal spin transport data, we determine the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface and finally the anomalous spin Hall angle of CoFe as a function of its spin diffusion length in a single device. Our experiments clearly reveal a negative anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing ordinary spin Hall angle. This is in contrast to the results reported for the ferromagnetic metals Co and permalloy.