Efficient spin to charge conversion and spin memory loss mitigation in oriented $\text{RuO}_2$ films

TL;DR

This study demonstrates efficient spin to charge conversion in oriented RuO₂ films, achieving high spin Hall conductivity and low spin memory loss, advancing spintronics device performance.

Contribution

It provides a detailed analysis of spin to charge conversion in (110)-oriented RuO₂ films, including measurements of spin Hall angle, spin diffusion length, and interface transparency.

Findings

Spin Hall angle of 0.14 ± 0.01

Spin diffusion length of 4.58 ± 0.40 nm

Spin memory loss of 15% at interface

Abstract

$\text{RuO}_2$, a transition metal oxide, is attracting attention in spintronics for its unique altermagnetic properties, which influence spin currents. Its ability to produce large spin-orbit torques and spin Hall effects is key for energy-efficient magnetic memory and logic devices. Additionally, the tunable thickness and crystallinity of $\text{RuO}_2$ thin films optimize torque efficiency for low-power switching. Spin pumping, a versatile method for investigating spin dynamics in $\text{RuO}_2$ thin films, has garnered considerable interest because of its straightforward, non-invasive and uncomplicated approach to addressing impedance mismatch and direct measurement of spintronic parameters. Here we present a systematic and detailed analysis on the efficient spin to charge conversion in (110)-oriented $\text{RuO}_2$ films with amorphous CoFeB as spin source. The spin Hall angle, and spin diffusion length were estimated to be 0.14 $\pm$ 0.01 and 4.58 $\pm$ 0.40 nm, respectively. The spin Hall conductivity of 998.89 $\pm$ 58.23 $\hbar \cdot \frac{\Omega^{-1} \, \text{cm}^{-1}}{e}$ has been estimated which is theoretically predicted to be of the similar order. The interfacial spin transparency has been achieved to be 90%. We have shown that the spin memory loss at the $\text{RuO}_2$/CoFeB interface is 15%, which is very small.