Li-7 Spin-Lattice Relaxation at Low Temperatures in a Superionic Conductor beta-LiGa

概要

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In order to investigate the Li+ ionic diffusion and the electronic states in a mixed conductor $\beta$-LiGa with high Li+ ionic diffusibility and electron/hole conductivity, 7Li NMR linewidth and spin–lattice relaxation measurements have been performed in 44.0, 47.0, and 50.0 at. % Li $\beta$-LiGa samples at 10.03 MHz in the temperature range between 10 and 320 K. The onset temperature $T_{\text{MN}}=70$ K of the motional narrowing in 50.0 at. % sample has been determined from the temperature dependence of the linewidth. The Li+ ionic diffusion is found to contribute to the spin–lattice relaxation rate $1/T_{1}$ down to ${\sim}0.5\ T_{\text{MN}}$ even below $T_{\text{MN}}$ where the motional narrowing does not occur. The high diffusibility of Li+ ions has been proved from a microscopic point of view. At low temperatures, the relations $1/T_{1}T=3.5\times 10^{-4}$, $3.8\times 10^{-4}$, and $5.1\times 10^{-4}$ s-1 K-1 are observed in 44.0, 47.0, and 50.0 at. % Li samples, respectively. The density of states of conduction electrons at the Fermi level in these compounds becomes higher with increasing Li content, which is consistent with the predictions by band calculations.
Physical Society of Japanの論文
2009-10-15