The Spin Nernst effect in Tungsten

TL;DR

This paper reports the experimental observation of the spin Nernst effect in tungsten, demonstrating its potential for efficient spin current generation through heat currents, distinct from the spin Hall effect.

Contribution

First experimental detection of the spin Nernst effect in tungsten, revealing its magnitude, sign, and relation to the spin Hall effect in a heterostructure setup.

Findings

Spin Nernst angle in W is similar in magnitude but opposite in sign to its spin Hall angle.

Heat current can generate larger spin currents due to sign differences under open circuit conditions.

Distinct characteristics of spin Nernst and spin Hall effects suggest new pathways for material exploration.

Abstract

The spin Hall effect allows generation of spin current when charge current is passed along materials with large spin orbit coupling. It has been recently predicted that heat current in a non-magnetic metal can be converted into spin current via a process referred to as the spin Nernst effect. Here we report the observation of the spin Nernst effect in W. In W/CoFeB/MgO heterostructures, we find changes in the longitudinal and transverse voltages with magnetic field when temperature gradient is applied across the film. The field-dependence of the voltage resembles that of the spin Hall magnetoresistance. A comparison of the temperature gradient induced voltage and the spin Hall magnetoresistance allows direct estimation of the spin Nernst angle. We find the spin Nernst angle of W to be similar in magnitude but opposite in sign with its spin Hall angle. Interestingly, under an open circuit condition, such sign difference results in spin current generation larger than otherwise. These results highlight the distinct characteristics of the spin Nernst and spin Hall effects, providing pathways to explore materials with unique band structures that may generate large spin current with high efficiency.