Scaling of spin Hall angle in 3d, 4d and 5d metals from Y3Fe5O12/metal spin pumping

TL;DR

This study systematically investigates spin pumping from YIG to various metals, revealing that the spin Hall angle scales with the fourth power of atomic number, highlighting the role of spin-orbit coupling.

Contribution

It provides a comprehensive analysis of spin Hall angles in 3d, 4d, and 5d metals using YIG spin pumping, demonstrating the atomic number dependence.

Findings

Spin Hall angles vary with atomic number across metals.

The spin Hall angle scales with the fourth power of atomic number.

Quantitative determination of interfacial spin mixing conductance.

Abstract

Pure spin currents generated by spin pumping in ferromagnet/nonmagnet (FM/NM) bilayers produce inverse spin Hall effect (ISHE) voltages in the NM, from which spin pumping and transport characteristics of the NM can be extracted. Due to its exceptionally low damping, Y3Fe5O12 (YIG) is an important and widely used FM for microwave devices and ferromagnetic resonance (FMR) spin pumping. Here we report systematic investigation of spin pumping from 20-nm thick YIG thin films to a series of 3d, 4d and 5d normal metals (Cu, Ag, Ta, W, Pt and Au) with various spin-orbit coupling strengths. From enhanced Gilbert damping obtained from the frequency dependence of FMR linewidths and ISHE signals, the spin Hall angles and YIG/NM interfacial spin mixing conductances are quantitatively determined for these metals. The spin Hall angles largely vary as the fourth power of the atomic number, corroborating the dominant role of spin-orbit coupling across a broad range in the inverse spin Hall effect.