Spin fluctuations yield zT enhancement in ferromagnets

Polash, Mobarak Hossain; Vashaee, Daryoosh

doi:10.1016/j.isci.2021.103356

Cited by 13 publications

(4 citation statements)

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“…Our most intriguing finding beyond the existing literature on the Cr-Te system [20,26,[49][50][51] is the existence of a critical doping (δ c ). From a previous DFT study, FM interactions couple Cr atoms along the in-plane direction on one sublattice, while AFM interactions couple Cr atoms along the out-ofplane direction on the other sublattice, in the case of CrTe (δ = 1) with two clearly differentiated magnetic Cr sublattices [37].…”

Section: H Nature Of Critical Dopingmentioning

confidence: 86%

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2

et al. 2022

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Cr 1+δ Te 2 is a self-intercalated transition metal dichalcogenide that hosts tunable electronic filling and magnetism in its semimetallic band structure. Recent angle-resolved photoemission spectroscopy (ARPES) studies have unveiled a systematic shift in this semimetallic band structure relative to the chemical potential with increased Cr doping. This paper presents the temperature and magnetic field dependence of the longitudinal thermopower S xx for different Cr 1+δ Te 2 compositions. We show that as doping increases, the sign of S xx changes from positive to negative at the critical doping level of δ ∼ 0.5. This observed doping-dependent trend in the thermopower is consistent with the evolution of the semimetallic band structure from ARPES. Importantly, an anomalous enhancement of the thermoelectric response near T C is also observed around δ ∼ 0.5. Combining information from magnetometry and ARPES measurements, existence of the critical nature of the doping level δ c (∼ 0.5) is unveiled in magnetic semimetal Cr 1+δ Te 2 , where antiferromagnetic fluctuation and near-Fermienergy pseudogap formation play a potential vital role in enhancing thermoelectric energy conversion.

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Section: H Nature Of Critical Dopingmentioning

confidence: 86%

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2

et al. 2022

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“…For future study of enhancing the S for high-performance TE materials, we think that the interdisciplinary studies play the key role. Lately, interdisciplinary studies have greatly enriched the optimization method of S . ,, Some are based on the generalized S . The spin caloritronic effect adds new freedom to the enhancement of the S .…”

Section: Discussionmentioning

confidence: 99%

“…In non-spin-degenerate TE materials, spin provides a new dimension for the enhancement of the S . There are four main ways of spin caloritronic effects that have been applied to enhance the S : magnon drag, paramagnon drag, spin entropy and spin fluctuation (SF). The spin Seebeck effect (SSE) provides a new dimension toward S enhancement …”

Section: Introductionmentioning

confidence: 99%

Evolving Strategies Toward Seebeck Coefficient Enhancement

2023

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Metrics & MoreArticle Recommendations CONSPECTUS: Thermoelectric (TE) materials, interconverting electrical energy with heat energy, could improve energy utilization efficiency, optimize the energy structure, and promote sustainable economic and social development. The Seebeck coefficient (S), characterizing the output power, is a particularly important parameter for conversion efficiency of TE materials.In the past 200 years since the Seebeck effect was discovered, researchers have tried various ways to increase S to increase the TE performance of materials. In addition to traditional TE approaches to enhance the S, such as energy filtering effect and band convergence, innovative methods of improving the generalized S have emerged in interdisciplinary disciplines, like spin entropy.We have successfully optimized the S to boost the performance of many TE materials, such as SnTe, SnSe, and SnS. In this Account, we focus on the physical mechanisms affecting the S, discuss traditional and innovative methods to optimize the S, and look forward to some promising interdisciplinary approaches for further research to improve the S. First, we analyze the physical mechanism of the basic parameters and their effects on S. Optimizing the carrier concentration, the adjustment of scattering behavior and the increment of effective mass are common methods of improving the S. Second, we summarize several emerging interdisciplinary methods that could enhance the generalized S, like the spin caloritronic effect including magnon/paramagnon drag, spin entropy, and spin fluctuation. The spin Seebeck effect liberates the traditional direction limit between temperature and S and gives a new path toward the S enhancement. We also emphasize the significance of the utilization of phonon drag in the low temperature area. Third, based on previous work, we think the topological states regulation is a burgeoning innovative method for S enhancement of TE materials. Last, we discuss and envision some interdisciplinary strategies for further improving S in the future. This Account indicates that S could be regulated as required, and the interdisciplinary research is beneficial to expand the methods of optimizing TE parameters. We hope to draw the attention of researchers to the enhancement of S and TE performance via innovative study and guide researchers to promote the theoretical innovation research of TE materials.

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“…Through the control of material structure at these scales, it is possible to manipulate their electrical, thermal, and optical properties, vital for the miniaturization and enhancement of semiconductor devices [ 1 , 2 , 3 ]. Within this context, the field of semiconductors has made significant strides, innovatively employing nanostructuring to develop materials with unique electronic properties or low thermal conductivity [ 4 , 5 , 6 , 7 ]. This approach has expedited the development of advanced thermoelectric materials [ 8 , 9 , 10 , 11 ].…”

Section: Introductionmentioning

confidence: 99%

Microscale Engineering of n-Type Doping in Nanostructured Gallium Antimonide: AC Impedance Spectroscopy Insights on Grain Boundary Characterization and Strategies for Controlled Dopant Distribution

Hall,

Vashaee

2023

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This paper investigates the microscale engineering aspects of n-type doped GaSb to address the challenges associated with achieving high electrical conductivity and precise dopant distribution in this semiconductor material. AC impedance spectroscopy is employed as a reliable technique to characterize the microstructural and electrical properties of GaSb, providing valuable insights into the impact of grain boundaries on overall electrical performance. The uneven distribution of dopants, caused by diffusion, and the incomplete activation of introduced dopants pose significant obstacles in achieving consistent material properties. To overcome these challenges, a careful selection of alloying elements, such as bismuth, is explored to suppress the formation of native acceptor defects and modulate band structures, thereby influencing the doping and compensator formation processes. Additionally, the paper examines the effect of microwave annealing as a potential solution for enhancing dopant activation, minimizing diffusion, and reducing precipitate formation. Microwave annealing shows promise due to its rapid heating and shorter processing times, making it a viable alternative to traditional annealing methods. The study underscores the need for a stable grain boundary passivation strategy to achieve significant improvements in GaSb material performance. Simple grain size reduction strategies alone do not result in better thermoelectric performance, for example, and increasing the grain boundary area per unit volume exacerbates the issue of free carrier compensation. These findings highlight the complexity of achieving optimal doping in GaSb materials and the importance of innovative analytical techniques and controlled doping processes. The comprehensive exploration of n-type doped GaSb presented in this research provides valuable insights for future advancements in the synthesis and optimization of high-conductivity nanostructured n-type GaSb, with potential applications in thermoelectric devices and other electronic systems.

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Spin fluctuations yield zT enhancement in ferromagnets

Cited by 13 publications

References 58 publications

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2

Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2

Evolving Strategies Toward Seebeck Coefficient Enhancement

Microscale Engineering of n-Type Doping in Nanostructured Gallium Antimonide: AC Impedance Spectroscopy Insights on Grain Boundary Characterization and Strategies for Controlled Dopant Distribution

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