Magnon-drag thermopower in antiferromagnets <i>versus</i> ferromagnets

Polash, Mobarak Hossain; Mohaddes, Farzad; Rasoulianboroujeni, Morteza; Vashaee, Daryoosh

doi:10.1039/c9tc06330g

Cited by 33 publications

(20 citation statements)

References 37 publications

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“…Heat capacity is one of the reliable and direct methods to probe the existence of different entropy carriers, including electronic, phonons, magnons, Schottky, dilation, spin-state transitions, and spin fluctuations ( Polash et al., 2020b ; Ikeda and Gschneidner, 1982 ). All the contributing sources in heat capacity have distinct temperature dependency ( Polash et al., 2020b ; Ikeda and Gschneidner, 1982 ).…”

Section: Resultsmentioning

confidence: 99%

Spin fluctuations yield zT enhancement in ferromagnets

Polash

Vashaee

2021

iScience

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Section: Resultsmentioning

confidence: 99%

Spin fluctuations yield zT enhancement in ferromagnets

Polash

Vashaee

2021

iScience

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“…The field‐dependent reduction of the thermopower peak may also suggest the presence of the insignificant magnon‐carrier drag thermopower. The magnon‐drag generally maximize at the transition temperature, [ 10,38,44 ] i.e., ≈70 K. According to Figure 5b, the thermopower maximizes at ≈50 K, suggesting that the α peak in the AFM domain must be due to the phonon drag. Moreover, the heat capacity analysis shows only a small contribution from magnonic heat capacity, which has a proportional relationship with α.…”

Section: Thermoelectric Transport Propertiesmentioning

confidence: 97%

Anomalous Thermoelectric Transport Properties of Fe‐Rich Magnetic FeTe

Polash

Vashaee

2021

Physica Rapid Research Ltrs

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The interplay between magnetism and quantum effects has motivated several thermoelectric studies on iron‐telluride yet with little insight on the anomalous features in transport properties near magnetostructural transition temperature (≈70 K). A detailed investigation is carried out on Fe1.1Te by characterizing magnetic, heat capacity, galvanomagnetic, and thermoelectric transport properties to understand the electronic, magnetic, and structural origin of those anomalies. The magnetic susceptibility indicates a bicollinear stripe and short‐range ordering in the antiferromagnetic and paramagnetic domains, respectively. Hall conductivity and transverse magnetoresistance reveal a multicarrier transport impacted by spin fluctuations and magnons. Contributions from phonon‐drag and magnon‐drag are evaluated to understand the origin of the broad peak in antiferromagnetic thermopower. The peak at ≈50 K and the insignificant entropy contribution from the magnonic heat capacity support the phonon‐drag as the origin. The field‐dependent enhancement of thermal conductivity must be associated with field‐dependent spin‐phonon coupling modification. The field‐induced thermopower reduction can be attributed to the suppression of magnons or paramagnons, as evidenced by the magnetic susceptibility data. Above 70 K, the thermal conductivity drops sharply due to the structural change modifying phonon modes. Understanding these properties originated from the spin, and quantum effects are instrumental for designing high‐performance spin‐driven thermoelectrics.

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“…For this reason, the theory does not tell us how to tune the spin entropy under finite temperature. Recently, the Seebeck coefficient in Li-doped MnTe was found to be significantly enhanced by the magnetic phase transition, while the enhancement is strongly dependent on the transition temperature and carrier concentration [ 36 – 38 ]. The phenomenon was explained by magnon (or paramagnon) drag, but not spin entropy.…”

Section: Introductionmentioning

confidence: 99%

Anomalous Thermopower and High ZT in GeMnTe ₂ Driven by Spin’s Thermodynamic Entropy

et al. 2021

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NaxCoO2 was known 20 years ago as a unique example in which spin entropy dominates the thermoelectric behavior. Hitherto, however, little has been learned about how to manipulate the spin degree of freedom in thermoelectrics. Here, we report the enhanced thermoelectric performance of GeMnTe2 by controlling the spin’s thermodynamic entropy. The anomalously large thermopower of GeMnTe2 is demonstrated to originate from the disordering of spin orientation under finite temperature. Based on the careful analysis of Heisenberg model, it is indicated that the spin-system entropy can be tuned by modifying the hybridization between Te-p and Mn-d orbitals. As a consequent strategy, Se doping enlarges the thermopower effectively, while neither carrier concentration nor band gap is affected. The measurement of magnetic susceptibility provides a solid evidence for the inherent relationship between the spin’s thermodynamic entropy and thermopower. By further introducing Bi doing, the maximum ZT in Ge0.94Bi0.06MnTe1.94Se0.06 reaches 1.4 at 840 K, which is 45% higher than the previous report of Bi-doped GeMnTe2. This work reveals the high thermoelectric performance of GeMnTe2 and also provides an insightful understanding of the spin degree of freedom in thermoelectrics.

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Magnon-drag thermopower in antiferromagnets versus ferromagnets

Abstract: Multi magnon interaction with carriers limits the magnon lifetime in FMs compared to AFMs. The longer lifetime, double degeneracy, and higher group velocity of magnons in AFMs generally lead to higher first-order magnon-carrier drag thermopower.

Cited by 33 publications

References 37 publications

Spin fluctuations yield zT enhancement in ferromagnets

Spin fluctuations yield zT enhancement in ferromagnets

Anomalous Thermoelectric Transport Properties of Fe‐Rich Magnetic FeTe

Anomalous Thermopower and High ZT in GeMnTe ₂ Driven by Spin’s Thermodynamic Entropy

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Magnon-drag thermopower in antiferromagnets versus ferromagnets

Abstract: Multi magnon interaction with carriers limits the magnon lifetime in FMs compared to AFMs. The longer lifetime, double degeneracy, and higher group velocity of magnons in AFMs generally lead to higher first-order magnon-carrier drag thermopower.

Cited by 33 publications

References 37 publications

Spin fluctuations yield zT enhancement in ferromagnets

Spin fluctuations yield zT enhancement in ferromagnets

Anomalous Thermoelectric Transport Properties of Fe‐Rich Magnetic FeTe

Anomalous Thermopower and High ZT in GeMnTe 2 Driven by Spin’s Thermodynamic Entropy

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Anomalous Thermopower and High ZT in GeMnTe ₂ Driven by Spin’s Thermodynamic Entropy