Quantitative measurement of figure of merit for transverse thermoelectric conversion in Fe/Pt metallic multilayers

This study presents a measurement method for determining the figure of merit for transverse thermoelectric conversion (\( z_\mathrm{T}T \)) in thin film forms. Leveraging the proposed methodology, we comprehensively investigate the transverse thermoelectric coefficient (\( S_\mathrm{T} \)), in-plane...

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Bibliographic Details
Published in:arXiv.org 2024-01
Main Authors: Yamazaki, Takumi, Hirai, Takamasa, Yagi, Takashi, Yamashita, Yuichiro, Uchida, Ken-ichi, Seki, Takeshi, Takanashi, Koki
Format: Article
Language:English
Subjects:
Anisotropy
Crystal growth
Electrical resistivity
Electron transport
Epitaxial growth
Ferrous alloys
Figure of merit
Iron
Measurement methods
Measurement techniques
Multilayers
Polycrystals
Thermal conductivity
Thermoelectricity
Thin films
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Summary:This study presents a measurement method for determining the figure of merit for transverse thermoelectric conversion (\( z_\mathrm{T}T \)) in thin film forms. Leveraging the proposed methodology, we comprehensively investigate the transverse thermoelectric coefficient (\( S_\mathrm{T} \)), in-plane electrical conductivity (\( \sigma_{yy} \)), and out-of-plane thermal conductivity (\( \kappa_{xx} \)) in epitaxial and polycrystalline Fe/Pt metallic multilayers. The \( \kappa_{xx} \) values of multilayers with a number of stacking repetitions (\( N \)) of 200 are lower than those of FePt alloy films, indicating that the multilayer structure effectively contributes to the suppression of \( \kappa_{xx} \). \( z_\mathrm{T}T \) is found to increase with increasing \( N \), which remarkably reflects the \( N \)-dependent enhancement of the \( S_\mathrm{T} \) values. Notably, \( S_\mathrm{T} \) and \( \sigma_{yy} \) are significantly larger in the epitaxial multilayers than those in the polycrystalline counterparts, whereas negligible differences in \( \kappa_{xx} \) are observed between the epitaxial and polycrystalline multilayers. This discrepancy in \( \sigma_{yy} \) and \( \kappa_{xx} \) with respect to crystal growth is due to the different degree of anisotropy in electron transport between epitaxial and polycrystalline multilayers, and epitaxial growth can lead to an enhancement of \( z_\mathrm{T}T \) in the multilayers. This study is the first demonstration in the evaluation of \( z_\mathrm{T}T \) in thin film forms, and our proposed measurement technique reveals the transverse thermoelectric properties inherent to multilayers.
ISSN:2331-8422