Large Spin Nernst Effect in Ni₇₀Cu₃₀ Alloy

Wen-Yuan Li^1,2*, Chia-Hsi Lin¹, Guang-Yu Guo^1,3, Ssu-Yen Huang^1,4, Danru Qu^2,4

¹Department of Physics, National Taiwan University, Taipei, Taiwan
²Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
³Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan
⁴Center of Atomic Initiatives for New Materials, National Taiwan University, Taipei, Taiwan

* Presenter:Wen-Yuan Li, email:wl02244135@gmail.com

Heat, spin, and charge interconversion plays an important role in spin caloritronic research. Significant progress has been made in longitudinal heat-to-spin conversion via the spin Seebeck effect (SSE) in ferromagnetic (FM) materials, as well as in transverse charge-to-spin conversion via the spin Hall effect (SHE) in non-magnetic (NM) metals. However, the spin Nernst effect (SNE) in NM metals is still less understood, mainly due to the challenge of detecting small signals mixed with background noise. In this study, we investigate thin films of Ni₇₀Cu₃₀ alloy, a material exhibiting both a large Seebeck coefficient and a sizable spin Hall angle. We demonstrate an even larger SNE with a spin Nernst angle (θ_SN) of -71.7%, which is nearly nine times larger than that of platinum (θ_SN=-8.2%). In addition, our ab initio calculations show that adding Cu shifts the Fermi level of Ni to a position that results in a remarkable enhancement of spin Nernst conductivity. Our findings not only improve our understanding of transverse heat-to-spin conversion in NM metals but also provide guidance for discovering materials with superior spin Nernst effect performance.

Keywords: spin current, spintronics, spin Nernst effect