title: Li+ ionic diffusion and vacancy ordering in beta-LiGa.
abstract: 7Li and 71Ga NMR measurements have been performed to study the Li+ ionic motion and vacancy ordering in the lithium semimetal beta-LiGa. The temperature dependence of the spin-lattice relaxation rate, T1(-1) of the 7Li nuclei in the 50 atom% Li sample shows an asymmetric broad peak around 175 K and is interpreted in terms of fast Li ionic diffusion. The activation energy of hopping is estimated as 0.11 eV using a non-Debye type relaxation model. In the temperature dependence of T1(-1) of the 7Li nuclei in 44 and 47 atom% Li samples, steep peaks are observed at 225 and 195 K, respectively. The origin of these anomalous peaks is attributed to the order-disorder transformation of Li+ vacancies. The temperature dependence of T1(-1) of the 71Ga nuclei measured above 200 K is interpreted in terms of the relaxation originating from the fluctuation of the electric field gradient at the 71Ga nuclei due to mobile Li+ ions. The activation energy for the Li+ ionic diffusion estimated from T1(-1) of the 71Ga nuclei is comparable with that obtained from T1(-1) of the 7Li nuclei.
authors.affiliation: Department of Physics, Faculty of Engineering, The University of Tokushima, Tokushinma 770-8506, Japan. koichi@pm.tokushima-u.ac.jp
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakamura
authors.forename: Keisuke
authors.initials: K
authors.lastname: Motoki
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Michihiro
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Kanashiro
authors.forename: Masahito
authors.initials: M
authors.lastname: Yahagi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Hamanaka
authors.forename: Kazuo
authors.initials: K
authors.lastname: Kuriyama