Observation of transverse spin Nernst magnetoresistance induced by thermal spin current in ferromagnet/non-magnet bilayers

TL;DR

This study demonstrates the generation of transverse spin currents via the spin Nernst effect in ferromagnet/non-magnet bilayers, revealing significant magnetoresistance changes and suggesting efficient thermally-induced spin current generation.

Contribution

It provides experimental evidence of the spin Nernst effect in heavy metals and quantifies the spin Nernst angles, highlighting their potential for spintronic applications.

Findings

Transverse magnetoresistance is significantly affected by heavy metal layer and thickness.

Spin Nernst angles of W and Pt have opposite signs to their spin Hall angles.

Spin Nernst angle magnitude is comparable to the spin Hall angle, indicating efficient spin current generation.

Abstract

Electric generation of spin current via spin Hall effect is of great interest as it allows an efficient manipulation of magnetization in spintronic devices. Theoretically, spin current can be also created by a temperature gradient, which is known as spin Nernst effect. Here, we report spin Nernst effect-induced transverse magnetoresistance in ferromagnet (FM)/non-magnetic heavy metal (HM) bilayers. We observe that the magnitude of transverse magnetoresistance (i.e., planar Nernst signal) in FM/HM bilayers is significantly modified by HM and its thickness. This strong dependence of transverse magnetoresistance on HM evidences the spin Nernst effect in HM; the generation of thermally-induced spin current in HM and its subsequent reflection at the FM/HM interface. Our analysis of transverse magnetoresistance shows that the spin Nernst angles of W and Pt have the opposite sign to their spin Hall angles. Moreover, our estimate implies that the magnitude of the spin Nernst angle would be comparable to that of the spin Hall angle, suggesting an efficient generation of spin current by the spin Nernst effect.