Nuclear magnetic resonance study of the low-temperature localized H(D) motion in α-ScHx(Dx): Isotope effects
Abstract
Nuclear magnetic resonance measurements of the 45Sc, 1H, and 2D spin-lattice relaxation rates in the solid solutions α-ScHx (x=0, 0.11, and 0.27) and α-ScDx (x=0.05 and 0.22) have been performed over the temperature range 4.2-294 K. For the hydrided and deuterided samples we have found pronounced deviations of the 45Sc relaxation rate measured at 86.2 MHz from the Korringa behavior in the range 30-180 K. The excess 45Sc relaxation rate displays a peak near 100 K in α-ScHx and near 110-140 K in α-ScDx, resulting from the quadrupole interaction modulated by fast localized hopping of H(D) atoms. The amplitude of the 45Sc relaxation rate peak in the deuterided samples is found to be much higher than in the hydrided samples with comparable hydrogen content. This unusual isotope effect indicates that the fraction of D atoms participating in the fast localized motion in α-ScDx is approximately six times as large as the corresponding fraction of H atoms in α-ScHx. The results of our measurements of the 1H and 2D relaxation rates are consistent with this conclusion. The strong effect of H<-->D substitution on the fraction of atoms involved in the localized hopping should be accounted for in any microscopic model of hydrogen motion in Sc.
- Publication:
-
Physical Review B
- Pub Date:
- July 1999
- DOI:
- 10.1103/PhysRevB.60.966
- Bibcode:
- 1999PhRvB..60..966B
- Keywords:
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- 66.30.-h;
- 76.60.-k;
- Diffusion in solids;
- Nuclear magnetic resonance and relaxation