Large Spin Nernst Effect in Ni70Cu30 Alloy

TL;DR

This study reports a large spin Nernst effect in Ni70Cu30 alloy, significantly exceeding that of platinum, driven by electronic structure modifications, advancing the understanding of heat-to-spin conversion in spin caloritronics.

Contribution

The paper demonstrates a large spin Nernst effect in Ni70Cu30 alloy and explains its origin through ab initio calculations, providing new insights into material design for spin caloritronic applications.

Findings

Ni70Cu30 exhibits a spin Nernst angle from -28% to -72%.

The spin Nernst effect in Ni70Cu30 surpasses that of platinum.

Electronic structure shifts cause the large spin Nernst conductivity.

Abstract

The interplay among heat, spin, and charge is the central focus in spin caloritronic research. While the longitudinal heat-to-spin conversion via the spin Seebeck effect has been intensively studied, the transverse heat-to-spin conversion via the spin Nernst effect (SNE) has not been equally explored. One major challenge is the minuscule signals generated by the SNE, which are often mixed with the background noises. In this work, we overcome this difficulty by studying the thin films of Ni70Cu30 alloy with not only a sizable spin Hall angle but also a large Seebeck coefficient. We observe in the Ni70Cu30 alloy a large spin Nernst effect with an estimated spin Nernst angle ranging from -28% to -72%. In comparison, the spin Nernst angle for Pt is -8.2%. Our ab initio calculation reveals that the large spin Nernst conductivity in Ni70Cu30 is caused by the Fermi energy shift to the steepest slope of the spin Hall conductivity curve due to electron doping from 30% Cu. Our study provides critical directions in searching for materials with a large spin Nernst effect.