Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe

Y. Zheng; T. Lu; Md M.H. Polash; M. Rasoulianboroujeni; N. Liu; M. E. Manley; Y. Deng; P. J. Sun; X. L. Chen; R. P. Hermann; D. Vashaee; J. P. Heremans; H. Zhao

doi:10.1126/sciadv.aat9461

Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe

Y. Zheng, T. Lu, Md M.H. Polash, M. Rasoulianboroujeni, N. Liu, M. E. Manley, Y. Deng, P. J. Sun, X. L. Chen, R. P. Hermann, D. Vashaee, J. P. Heremans, H. Zhao

Neutron & X-Ray Scattering, & Thermophys

Research output: Contribution to journal › Article › peer-review

103 Scopus citations

Abstract

Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower a strongly at temperatures up to 900 K. Below the Néel temperature (T_N ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes a_md to the thermopower, which scales as ~T³. Magnon drag persists into the paramagnetic state up to >3 × T_N because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier–magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit ZT > 1 at T > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.

Original language	English
Article number	eaat9461
Journal	Science Advances
Volume	5
Issue number	9
DOIs	https://doi.org/10.1126/sciadv.aat9461
State	Published - Sep 13 2019

Funding

We thank O. Garlea and D. Abernathy at ORNL for assistance in collecting the neutron spectroscopy data at HYSPEC and ARCS, respectively. Y.Z. and J.P.H. acknowledge the Center for Emergent Materials, an NSF-MRSEC under grant number DMR-1420451, and the Army Research Office (ARO) MURI Materials with Extraordinary Spin-heat Coupling under grant number W911NF-14-1-0016. M.M.H.P. and D.V. acknowledge partial support by Air Force Office of Scientific Research (AFOSR) under contract number FA9550-12-1-0225 and the National Science Foundation (NSF) under grant numbers ECCS-1515005 and CMMI-1363485. H.Z. acknowledges the funding support by the National Natural Science Foundation of China under contract numbers U1601213 and 51572287. Neutron scattering work by R.P.H. and M.E.M. was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. This research used resources at the Spallation Neutron Source (SNS), a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory (ORNL).

Funders	Funder number
DOE Office of Science
NSF-MRSEC	DMR-1420451
National Science Foundation	1515005, ECCS-1515005, CMMI-1363485, 1363485, 1420451, 1351533
U.S. Department of Energy
Air Force Office of Scientific Research	FA9550-12-1-0225
Army Research Office	W911NF-14-1-0016
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory
Division of Materials Sciences and Engineering
National Natural Science Foundation of China	51572287, U1601213

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title = "Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe",

abstract = "Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower a strongly at temperatures up to 900 K. Below the N{\'e}el temperature (TN ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes amd to the thermopower, which scales as ~T3. Magnon drag persists into the paramagnetic state up to >3 × TN because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier–magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit ZT > 1 at T > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.",

author = "Y. Zheng and T. Lu and Polash, {Md M.H.} and M. Rasoulianboroujeni and N. Liu and Manley, {M. E.} and Y. Deng and Sun, {P. J.} and Chen, {X. L.} and Hermann, {R. P.} and D. Vashaee and Heremans, {J. P.} and H. Zhao",

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AU - Lu, T.

AU - Polash, Md M.H.

AU - Rasoulianboroujeni, M.

AU - Liu, N.

AU - Manley, M. E.

AU - Deng, Y.

AU - Sun, P. J.

AU - Chen, X. L.

AU - Hermann, R. P.

AU - Vashaee, D.

AU - Heremans, J. P.

AU - Zhao, H.

PY - 2019/9/13

Y1 - 2019/9/13

N2 - Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower a strongly at temperatures up to 900 K. Below the Néel temperature (TN ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes amd to the thermopower, which scales as ~T3. Magnon drag persists into the paramagnetic state up to >3 × TN because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier–magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit ZT > 1 at T > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.

AB - Local thermal magnetization fluctuations in Li-doped MnTe are found to increase its thermopower a strongly at temperatures up to 900 K. Below the Néel temperature (TN ~ 307 K), MnTe is antiferromagnetic, and magnon drag contributes amd to the thermopower, which scales as ~T3. Magnon drag persists into the paramagnetic state up to >3 × TN because of long-lived, short-range antiferromagnet-like fluctuations (paramagnons) shown by neutron spectroscopy to exist in the paramagnetic state. The paramagnon lifetime is longer than the charge carrier–magnon interaction time; its spin-spin spatial correlation length is larger than the free-carrier effective Bohr radius and de Broglie wavelength. Thus, to itinerant carriers, paramagnons look like magnons and give a paramagnon-drag thermopower. This contribution results in an optimally doped material having a thermoelectric figure of merit ZT > 1 at T > ~900 K, the first material with a technologically meaningful thermoelectric energy conversion efficiency from a spin-caloritronic effect.

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Paramagnon drag in high thermoelectric figure of merit Li-doped MnTe

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