Quantitative separation of the anisotropic magnetothermopower and planar Nernst effect by the rotation of an in-plane thermal gradient

TL;DR

This paper introduces a novel experimental method to rotate in-plane thermal gradients and magnetic fields, enabling the quantitative separation of anisotropic thermopower and planar Nernst effect in spin caloritronics.

Contribution

It presents a new technique for in-plane thermal gradient rotation, allowing simultaneous measurement and separation of thermopower, anisotropic magnetothermopower, and planar Nernst effect.

Findings

Quantitative separation of thermopower and Nernst effects achieved

Phase shift observed between thermopower and Nernst signals

Method enables anisotropic measurements in spin caloritronics

Abstract

A thermal gradient as the driving force for spin currents plays a key role in spin caloritronics. In this field the spin Seebeck effect (SSE) is of major interest and was investigated in terms of in-plane thermal gradients inducing perpendicular spin currents (transverse SSE) and out-of-plane thermal gradients generating parallel spin currents (longitudinal SSE). Up to now all spincaloric experiments employ a spatially fixed thermal gradient. Thus anisotropic measurements with respect to well defined crystallographic directions were not possible. Here we introduce a new experiment that allows not only the in-plane rotation of the external magnetic field, but also the rotation of an in-plane thermal gradient controlled by optical temperature detection. As a consequence, the anisotropic magnetothermopower and the planar Nernst effect in a permalloy thin film can be measured simultaneously and reveal a phase shift, that allows the quantitative separation of the thermopower, the anisotropic magnetothermopower and the planar Nernst effect.