Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method

A Sola,D Meier,M Kuepferling,G Reiss,V Basso,M Pasquale,P Bougiatioti,T Kuschel

doi:10.1038/srep46752

Abstract

The determination of the longitudinal spin Seebeck effect (LSSE) coefficient is currently plagued by a large uncertainty due to the poor reproducibility of the experimental conditions used in its measurement. In this work we present a detailed analysis of two different methods used for the determination of the LSSE coefficient. We have performed LSSE experiments in different laboratories, by using different setups and employing both the temperature difference method and the heat flux method. We found that the lack of reproducibility can be mainly attributed to the thermal contact resistance between the sample and the thermal baths which generate the temperature gradient. Due to the variation of the thermal resistance, we found that the scaling of the LSSE voltage to the heat flux through the sample rather than to the temperature difference across the sample greatly reduces the uncertainty. The characteristics of a single YIG/Pt LSSE device obtained with two different setups was (1.143 ± 0.007) 10−7 Vm/W and (1.101 ± 0.015) 10−7 Vm/W with the heat flux method and (2.313 ± 0.017) 10−7 V/K and (4.956 ± 0.005) 10−7 V/K with the temperature difference method. This shows that systematic errors can be considerably reduced with the heat flux method.

Highlights

The interactions between charge carriers and heat currents is a topic of great interest both for fundamental research and technological applications such as thermoelectric power generators[1]
In order to correct the effects of this misalignment on the values of the coercive fields reported in Fig. 2, we performed an additional magnetization measurement by means of a vibrating sample magnetometer (VSM)
The thermal resistance of the contacts leads to a substantial temperature drop so that the temperature difference across the sample is largely overestimated by this method

Summary

Introduction

The interactions between charge carriers and heat currents is a topic of great interest both for fundamental research and technological applications such as thermoelectric power generators[1] This class of devices exploits the Seebeck effect which allows the conversion of heat into electricity through the electric field which occurs in a junction of two different materials under a thermal gradient[2]. The SSE is usually measured in the longitudinal configuration (LSSE)[10] where the temperature gradient is applied perpendicularly to the sample plane and the applied magnetic field In this configuration other thermoelectric contributions to the SSE result negligible[11,12,13,14,15,16,17]. We will show a comparison between two different experimental procedures for the determination of ∇T

Methods

Results

Conclusion