Microscopic Dynamics of Li${}^{+}$ in Rutile TiO${}_2$ Revealed by ${}^8$Li $\beta$-detected NMR

Abstract

We report measurements of the dynamics of isolated ${}^8$Li${}^{+}$ in single crystal rutile TiO${}_2$ using $\beta$-detected NMR. From spin-lattice relaxation and motional narrowing, we find two sets of thermally activated dynamics: one below 100 K; and one at higher temperatures. At low temperature, the activation barrier is $26.8(6)$ meV with prefactor $1.23(5)\times 10^{10}$ s${}^{-1}$. We suggest this is unrelated to Li${}^{+}$ motion, and rather is a consequence of electron polarons in the vicinity of the implanted ${}^8$Li${}^{+}$ that are known to become mobile in this temperature range. Above 100 K, Li${}^{+}$ undergoes long-range diffusion as an isolated uncomplexed cation, characterized by an activation energy and prefactor of $0.32(2)$ eV and $1.0(5)\times 10^{16}$ s${}^{-1}$, in agreement with macroscopic diffusion measurements. These results in the dilute limit from a microscopic probe indicate that Li${}^{+}$ concentration does not limit the diffusivity even up to high concentrations, but that some key ingredient is missing in the calculations of the migration barrier. The anomalous prefactors provide further insight into both Li${}^{+}$ and polaron motion.

arXiv comment14 pages, 9 figures

References in corpus (4)

• A direct view at excess electrons in TiO${}_2$ rutile and anatase
• Dual behavior of excess electrons in rutile TiO2
• Near-Surface Structural Phase Transition of SrTiO${}_3$ Studied with Zero-Field $\beta$-Detected Nuclear Spin Relaxation and Resonance
• Determination of the nature of fluctuations using ${}^{8}Li$ and ${}^{9}Li$ $\beta$-NMR and spin-lattice relaxation

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• Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted $\beta$-emitter ${}^8$Li
• Investigation of Ionic and Anomalous Magnetic Behavior in CrSe${}_2$ Using ${}^8$Li $\beta$-NMR
• Bi-Arrhenius diffusion and surface trapping of ${}^8$Li${}^{+}$ in rutile TiO${}_2$
• Lithium-ion dynamics in synthetic quartz studied via the NMR of implanted ${}^8$Li${}^{+}$