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Title: Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum

Abstract

125Te NMR spectra and spin-lattice relaxation times, T 1, have been measured for several GeTe-based materials with Te excess. In this paper, the spectra show inhomogeneous broadening by several thousand ppm and a systematic variation in T 1 relaxation time with resonance frequency. The quadratic dependence of the spin-lattice relaxation rate, 1/T 1, on the Knight shift in the Korringa relation is found to be valid over a wide range of Knight shifts. This result confirms that T 1 relaxation in GeTe-based materials is mostly dominated by hyperfine interaction between nuclei and free charge carriers. In GeTe with 2.5% excess of Te, about 15% of the material exhibits a Knight shift of ≥4500 ppm and a T 1 of only 0.3 ms, indicating a high hole concentration that could correspond to close to 50% vacancies on the Ge sublattice in this component. Lastly, our findings provide a basis for determining the charge carrier concentration and its distribution in complex thermoelectric and phase-change tellurides, which should lead to a better understanding of electronic and thermal transport properties as well as chemical bonding in these materials.

Authors:
 [1];  [2];  [3];  [1];  [4]
  1. Ames Lab., Ames, IA (United States). Division of Materials Sciences and Engineering
  2. (United States). Department of Physics and Astronomy
  3. Iowa State Univ., Ames, IA (United States). Department of Chemistry
  4. (United States). Department of Chemistry
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1355399
Alternate Identifier(s):
OSTI ID: 1359893
Report Number(s):
IS-J-9110
Journal ID: ISSN 0926-2040; PII: S0926204016300571
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Solid State Nuclear Magnetic Resonance
Additional Journal Information:
Journal Volume: 78; Journal ID: ISSN 0926-2040
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Complex tellurides; 125Te NMR; Knight shift; Spin-lattice relaxation; Korringa relation

Citation Formats

Levin, E. M., Iowa State Univ., Ames, IA, Cui, J. -F., Schmidt-Rohr, K., and Iowa State Univ., Ames, IA. Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum. United States: N. p., 2016. Web. doi:10.1016/j.ssnmr.2016.07.003.
Levin, E. M., Iowa State Univ., Ames, IA, Cui, J. -F., Schmidt-Rohr, K., & Iowa State Univ., Ames, IA. Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum. United States. doi:10.1016/j.ssnmr.2016.07.003.
Levin, E. M., Iowa State Univ., Ames, IA, Cui, J. -F., Schmidt-Rohr, K., and Iowa State Univ., Ames, IA. Sat . "Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum". United States. doi:10.1016/j.ssnmr.2016.07.003. https://www.osti.gov/servlets/purl/1355399.
@article{osti_1355399,
title = {Sub-millisecond 125Te NMR spin-lattice relaxation times and large Knight shifts in complex tellurides: Validation of a quadratic relation across the spectrum},
author = {Levin, E. M. and Iowa State Univ., Ames, IA and Cui, J. -F. and Schmidt-Rohr, K. and Iowa State Univ., Ames, IA},
abstractNote = {125Te NMR spectra and spin-lattice relaxation times, T1, have been measured for several GeTe-based materials with Te excess. In this paper, the spectra show inhomogeneous broadening by several thousand ppm and a systematic variation in T1 relaxation time with resonance frequency. The quadratic dependence of the spin-lattice relaxation rate, 1/T1, on the Knight shift in the Korringa relation is found to be valid over a wide range of Knight shifts. This result confirms that T1 relaxation in GeTe-based materials is mostly dominated by hyperfine interaction between nuclei and free charge carriers. In GeTe with 2.5% excess of Te, about 15% of the material exhibits a Knight shift of ≥4500 ppm and a T1 of only 0.3 ms, indicating a high hole concentration that could correspond to close to 50% vacancies on the Ge sublattice in this component. Lastly, our findings provide a basis for determining the charge carrier concentration and its distribution in complex thermoelectric and phase-change tellurides, which should lead to a better understanding of electronic and thermal transport properties as well as chemical bonding in these materials.},
doi = {10.1016/j.ssnmr.2016.07.003},
journal = {Solid State Nuclear Magnetic Resonance},
number = ,
volume = 78,
place = {United States},
year = {Sat Jul 16 00:00:00 EDT 2016},
month = {Sat Jul 16 00:00:00 EDT 2016}
}

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