Dresden 2003 – wissenschaftliches Programm
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M: Metallphysik
M 41: Postersitzung
M 41.6: Poster
Donnerstag, 27. März 2003, 14:30–16:30, HSZ
Electric quadrupole relaxation in substoichiometric dideuterides of hafnium and titanium — •Günter Majer1, Jürgen Gottwald1, and Richard G. Barnes2 — 1Max-Planck-Institut für Metallforschung, Heisenbergstr. 3, 70569 Stuttgart — 2Ames Laboratory, Iowa State University, Ames Iowa 50011, USA
The deuteron spin-lattice relaxation rates Γ1 have been measured in the substoichiometric dideuterides of hafnium, HfDx (1.68 ≤ x ≤ 1.90), and titanium, TiDx (x = 1.91), at temperatures between 300 and 830 K. The deuteron Γ1 values, which consist of quadrupolar (Γ1,quad), dipolar (Γ1,dip) and electronic (Γ1,e) contributions, are over wide temperature ranges dominated by Γ1,quad. An important feature of the quadrupolar relaxation is that the quadrupole moment interacts with the total electric field gradient (EFG) due to all surrounding charges taken together. Hence, to analyse Γ1,quad data, many-particle correlation functions are needed, in contrast to the dipolar relaxation which is adequately described by two-particle correlation functions only. In the case of the substoichiometric dideuterides, the fluctuations of the EFGs are related to the jumps of the vacancies on the deuterium sublattice. The temperature dependence of Γ1,quad yields the activation enthalpy Ha of the deuterium vacancies and thus that of the deuterium atoms. While the position of the Γ1,quad maximum is concentration independent, the amplitude scales as c(1−c) with the deuterium-vacancy concentration c = (1−x/2).