Inductive detection of inverse spin-orbit torques in magnetic heterostructures

TL;DR

This study investigates spin-orbit torques in ferromagnetic heterostructures with large spin-orbit interaction, revealing comparable SOT magnitudes to platinum and a correlation with ferromagnetic layer thickness.

Contribution

It demonstrates inductive detection of inverse spin-orbit torques in ferromagnetic heterostructures with large spin-orbit coupling, expanding understanding beyond heavy metal systems.

Findings

SOT magnitudes are comparable to platinum-based systems.

Significant correlation between SOT and CoFeB layer thickness.

Charge currents generated via inverse SOT are measurable with inductive techniques.

Abstract

The manipulation of magnetization via Magnetic torques is one of the most important phenomena in spintronics. In thin films, conventionally, a charge current flowing in a heavy metal is used to generate transverse spin currents and to exert torques on the magnetization of an adjacent ferromagnetic thin film layer. Here, in contrast to the typically employed heavy metals, we study spin-to-charge conversion in ferromagnetic heterostructures with large spin-orbit interaction that function as the torque-generating layers. In particular, we chose perpendicular magnetic anisotropy (PMA) multilayers [Co/Ni] and [Co/Pt] as the torque-generating layers and drive magnetization dynamics in metallic ferromagnetic thin film $\mathrm{Co_{20}Fe_{60}B_{20}}$ (CoFeB) layers with in-plane magnetic anisotropy (IMA). We investigate the spin dynamics driven by spin-orbit torque (SOT) and the concomitant charge current generation by the inverse SOT process using an inductive technique based on a vector network analyzer. In our experimental findings, we find that the SOTs generated by our multilayers are of a magnitude comparable to those produced by Pt, consistent with first-principles calculations. Furthermore, we noted a significant correlation between the SOT and the thickness of the CoFeB layer.