Deuteron NMR relaxation rates in cerium deuterides

Nuclear magnetic resonance (NMR) measurements of the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ spin-lattice and transverse relaxation rates, $T_1^{\mathrm{-}1}$ and $T_2^{\mathrm{-}1}$, have been made in a series of cerium deuterides, ${\mathrm{CeD}}_{\mathrm{x}}$. Results are reported for 2.01≤x≤2.90 and temperatures 77 ≤T≤573 K. Spin-lattice relaxation rates for ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ are compared to published rates for ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ and they are found to be in substantial agreement when ${}_{}{}^1{}_{}{}^{}\mathrm{H}$ rates are multiplied by the square of the ratio of gyromagnetic ratios, (${\gamma }_2$/${\gamma }_1$ ${)}^2$. As in the cerium hydrides, the spin-lattice relaxation rates are dominated by the direct magnetic dipolar interaction between the hydrogen nuclear moments and the cerium electronic moments. No noticeable effects of nuclear quadrupole interactions were observed in the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$ data. Transverse relaxation rates (spin echo) are narrowed as temperature is increased with narrowing temperatures ranging from about 200 to 250 K, depending upon concentration. Spin-lattice relaxation rates of both isotopes of hydrogen are observed to be enhanced in the regime 2.1≤x≤2.55 and ${10}^3$/T>3.5 ${\mathrm{K}}^{\mathrm{-}1}$. From the data it could not be established whether this enhancement is attributed primarily to increased values of the mean squared magnetic moments of the cerium ions or to an increase in the relaxation time of the cerium moments in this regime.