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Designing Spin-Crossover Systems to Enhance Thermopower and Thermoelertic Figure-of-Merit in Paramagnetic Materials
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  • Md Mobarak Hossain Polash,
  • Matthew B. Stone,
  • Songxue Chi,
  • Daryoosh Vashaee
Md Mobarak Hossain Polash
North Carolina State University at Raleigh
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Matthew B. Stone
Oak Ridge National Laboratory
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Songxue Chi
Oak Ridge National Laboratory
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Daryoosh Vashaee
North Carolina State University at Raleigh

Corresponding Author:[email protected]

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Abstract

Thermoelectric materials, capable of converting temperature gradients into electrical power, have been traditionally limited by a trade-off between thermopower and electrical conductivity. This study introduces a novel, broadly applicable approach that enhances both the spin-driven thermopower and the thermoelectric figure-of-merit (zT) without compromising electrical conductivity, using temperature-driven spin crossover. Our approach, supported by both theoretical and experimental evidence, is demonstrated through a case study of chromium doped-manganese telluride, but is not confined to this material and can be extended to other magnetic materials. By introducing dopants to create a high crystal field and exploiting the entropy changes associated with temperature-driven spin crossover, we achieved a significant increase in thermopower, by approximately 136 μV/K, representing more than a 200% enhancement at elevated temperatures within the paramagnetic domain. Our exploration of the bipolar semiconducting nature of these materials reveals that suppressing bipolar magnon/paramagnon-drag thermopower is key to understanding and utilizing spin crossover-driven thermopower. These findings, validated by inelastic neutron scattering, X-ray photoemission spectroscopy, thermal transport, and energy conversion measurements, shed light on crucial material design parameters. We provide a comprehensive framework that analyzes the interplay between spin entropy, hopping transport, and magnon/paramagnon lifetimes, paving the way for the development of high-performance spin-driven thermoelectric materials.
02 Mar 2024Submitted to Energy & Environmental Materials
05 Mar 2024Submission Checks Completed
05 Mar 2024Assigned to Editor
07 Mar 2024Review(s) Completed, Editorial Evaluation Pending
18 Mar 2024Reviewer(s) Assigned
30 May 2024Assigned to Editor
30 May 2024Submission Checks Completed
30 May 2024Review(s) Completed, Editorial Evaluation Pending
31 May 2024Reviewer(s) Assigned
12 Jun 2024Editorial Decision: Accept