A Universal Method for Separating Spin Pumping from Spin Rectification Voltage of Ferromagnetic Resonance

TL;DR

This paper introduces a universal method to distinguish spin pumping from spin rectification signals in bilayer spintronics devices, enabling accurate measurement of spin currents and the spin Hall angle regardless of device-specific microwave properties.

Contribution

The method leverages differences in angular and field symmetries of SP and SR, allowing for universal analysis of FMR-induced voltages without relying on line shape, and facilitates direct measurement of nonlinear spin current evolution.

Findings

Successfully measured the spin Hall angle as 0.021±0.015 in Py/Pt bilayers.

Demonstrated the method's applicability across various device configurations.

Enabled direct observation of nonlinear spin current behavior.

Abstract

We develop a method for universally resolving the important issue of separating spin pumping (SP) from spin rectification (SR) signals in bilayer spintronics devices. This method is based on the characteristic distinction of SP and SR, as revealed in their different angular and field symmetries. It applies generally for analyzing charge voltages in bilayers induced by the ferromagnetic resonance (FMR), independent of FMR line shape. Hence, it solves the outstanding problem that device specific microwave properties restrict the universal quantification of the spin Hall angle in bilayer devices via FMR experiments. Furthermore, it paves the way for directly measuring the nonlinear evolution of spin current generated by spin pumping. The spin Hall angle in a Py/Pt bilayer is thereby directly measured as 0.021$\pm$0.015 up to a large precession cone angle of about 20$^{\circ}$.