Dependence of spin pumping spin Hall effect measurements on layer thicknesses and stacking order

TL;DR

This study investigates how layer thicknesses and stacking order affect spin pumping and spin Hall effect measurements in ferromagnetic/non-magnetic bilayers, revealing a spin diffusion length in Pd and systematic effects of stacking order.

Contribution

It provides new insights into the dependence of spin Hall effect measurements on layer thickness and stacking order, highlighting systematic discrepancies despite calibration.

Findings

Determined the spin diffusion length in Pd as 5.5 +/- 0.5 nm.

Observed systematic changes in voltage lineshape with stacking order.

Identified persistent quantitative discrepancies in spin Hall effect analysis.

Abstract

Voltages generated from inverse spin Hall and anisotropic magneto-resistance effects via spin pumping in ferromagnetic (F)/non-magnetic (N) bilayers are investigated by means of a broadband ferromagnetic resonance approach. Varying the non-magnetic layer thickness enables the determination of the spin diffusion length in Pd of 5.5 +/- 0.5 nm. We also observe a systematic change of the voltage lineshape when reversing the stacking order of the F/N bilayer, which is qualitatively consistent with expectations from spin Hall effects. However, even after independent calibration of the precession angle, systematic quantitative discrepancies in analyzing the data with spin Hall effects remain.