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

Journal Article · Sat Jul 16 00:00:00 EDT 2016 · Solid State Nuclear Magnetic Resonance

DOI:https://doi.org/10.1016/j.ssnmr.2016.07.003· OSTI ID:1355399

Levin, E. M. ^[1]; Cui, J. -F. ^[2]; Schmidt-Rohr, K. ^[1]

---

1. Ames Lab., Ames, IA (United States). Division of Materials Sciences and Engineering
2. Iowa State Univ., Ames, IA (United States). Department of Chemistry

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.

• Research Organization: Ames Lab., Ames, IA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: AC02-07CH11358
• OSTI ID: 1355399
• Alternate ID(s): OSTI ID: 1359893
• Report Number(s): IS-J-9110; PII: S0926204016300571
• Journal Information: Solid State Nuclear Magnetic Resonance, Vol. 78; ISSN 0926-2040
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
Complex tellurides
125Te NMR
Knight shift
Spin-lattice relaxation
Korringa relation