Large spin Hall conductivity in epitaxial thin films of kagome antiferromagnet Mn$_3$Sn at room temperature

TL;DR

This study reports a significant enhancement of spin Hall conductivity in epitaxial Mn$_3$Sn thin films at room temperature, achieved through precise control of Mn composition, with implications for advanced spintronic device applications.

Contribution

The paper demonstrates a method to engineer high spin Hall conductivity in Mn$_3$Sn films by adjusting Mn composition, revealing a sign change and increased magnitude compared to previous studies.

Findings

Measured spin Hall conductivity of -702 Ω^{-1}cm^{-1} in Mn$_3$Sn films.

Identified Mn composition as a key factor in tuning spin Hall effects.

Demonstrated room temperature operation of high spin Hall conductivity in epitaxial films.

Abstract

Mn$_3$Sn is a non-collinear antiferromagnetic quantum material that exhibits a magnetic Weyl semimetallic state and has great potential for efficient memory devices. High-quality epitaxial $c$-plane Mn$_3$Sn thin films have been grown on a sapphire substrate using a Ru seed layer. Using spin pumping induced inverse spin Hall effect measurements on $c$-plane epitaxial Mn$_3$Sn/Ni$_{80}$Fe$_{20}$, we measure spin-diffusion length ($\lambda_{\rm Mn_3Sn}$), and spin Hall conductivity ($\sigma_{\rm{SH}}$) of Mn$_3$Sn thin films: $\lambda_{\rm Mn_3Sn}=0.42\pm 0.04$ nm and $\sigma_{\rm{SH}}=-702~\hbar/ e~\Omega^{-1}$cm$^{-1}$. While $\lambda_{\rm Mn_3Sn}$ is consistent with earlier studies, $\sigma_{\rm{SH}}$ is an order of magnitude higher and of the opposite sign. The behavior is explained on the basis of excess Mn, which shifts the Fermi level in our films, leading to the observed behavior. Our findings demonstrate a technique for engineering $\sigma_{\rm{SH}}$ of Mn$_3$Sn films by employing Mn composition for functional spintronic devices.