2018 APS March Meeting, Los Angeles, CA - Poster (G60.00304)
Session G60: Poster Session I, 2:00pm-5:00pm, Tuesday, March 6, 2018
Title: NMR and Magnetic Study of Half-Heusler Semiconductor NbFeSb
Abstract Body: The Half-Heusler semiconductor NbFeSb has been of considerable interest due to its excellent thermoelectric performance, especially its enhanced power factor. To further investigate the electronic properties of these materials, we have done Nb NMR and magnetic measurements on several NbFeSb samples with different defect densities, prepared at a series of hot pressing temperatures. Magnetization measurements show the presence of paramagnetic defects in undoped samples with a concentration of about 0.002 per formula unit independent of processing. MAS NMR measurements yield narrow lines with almost identical shifts of +3600 ppm. Changes in static- NMR line widths and amplitudes indicate a significantly larger concentration of apparently electrically inactive defects for samples prepared at lower processing temperatures. In addition, the NMR T1 relaxation time measurements vs. temperature indicate a wide distribution of local behavior which we have analyzed in terms of the distribution of magnetic defects in these samples.
Funding Acknowledgement: This work is supported by the Robert A. Welch Foundation and synthesis work is funded in part by the US Department of Energy and US Air Force.