Low-temperature H-1 nuclear magnetic resonance study of crystal and electronic structures of the nearly stoichiometric yttrium dihydride

: Zogal OJ, Vuorimaki AH, Ylinen EE

Publisher: TAYLOR & FRANCIS LTD

: 2000

Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties

PHILOSOPHICAL MAGAZINE A-PHYSICS OF CONDENSED MATTER STRUCTURE DEFECTS AND MECHANICAL PROPERTIES

: PHILOS MAG A

: 80

: 11

: 2549

: 2558

: 10

: 0141-8610

DOI: https://doi.org/10.1080/01418610008216491

Proton nuclear magnetic resonance absorption spectra and spin-lattice relaxation rates in yttrium dihydride have been measured in the temperature range from 4.2 to 310 K at 36.0 MHz. The second moment of the resonance line corresponds to the rigid-lattice regime for YH1.99 and its value agrees with the anticipated CaF2 type of structure. The main contribution to the spin-lattice relaxation rate R-1 arises from conduction electrons and is characterized by R-1e = 2.77 x 10(-3) s(-1) K-1 x T. Evidence of proton self-diffusion was seen in the linewidth and in R-1 for YH1.99+0.1 The onset temperature, about 250 K, of the self-diffusion, is close to the metal-semiconductor transition reported earlier for that hydride. Below that temperature the linewidth becomes temperature independent and the second moment of the line is explained in terms of different structure models. The fit to the temperature dependence of R-1 in the temperature range 70-310 K gives R-1e = 2.1 x 10(-3) s(-1) K-1 x T. The relaxation becomes almost temperature independent below 50 K. Various mechanisms for this behaviour are discussed. In addition, the R-1 data for the sample prepared with yttrium of 99.9% purity are presented. In contrast with the previous case, where pure yttrium from the Ames Laboratory was used, R-1 has a large contribution of spin diffusion to the paramagnetic Gd3+ ions.

Physical sciences