Browsing by Author "Li, RH"

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    Evolution of the metallic state in LaNiO3/LaAlO3 superlattices measured by Li8β-detected NMR
    (American Physical Society (APS), 2021-11-12) Karner, VL; Chatzichristos, A; Cortie, DL; Fujimoto, D; Kiefl, RF; Levy, CDP; Li, RH; McFadden, RML; Morris, GD; Pearson, MR; Benckiser, E; Boris, AV; Cristiani, G; Logvenov, G; Keimer, B; MacFarlane, WA
    Using ion-implanted Li8 β-detected NMR, we study the evolution of the correlated metallic state of LaNiO3 in a series of LaNiO3/LaAlO3 superlattices as a function of bilayer thickness. Spin-lattice relaxation measurements in an applied field of 6.55T reveal two equal amplitude components: one with metallic (T linear) 1/T1 and a second with a more complex T dependence. The metallic character of the slow relaxing component is only weakly affected by the LaNiO3 thickness, while the fast component is much more sensitive, exhibiting the opposite temperature dependence (increasing toward low T) in the thinnest, most magnetic samples. The origin of this bipartite relaxation is discussed in terms of electronic phase separation. ©2021 American Physical Society.
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    Local electronic and magnetic properties of the doped topological insulators Bi2Se3:Ca and Bi2Te3 : Mn investigated using ion-implanted 8Li β-NMR
    (American Physical Society (APS), 2020-12-28) McFadden, RML; Chatzichristos, A; Cortie, DL; Fujimoto, D; San Hor, Y; Ji, H; Karner, VL; Kiefl, RF; Levy, CDP; Li, RH; McKenzie, I; Morris, GD; Pearson, MR; Stachura, M; Cava, RJ; MacFarlane, WA
    We report β-NMR measurements in Bi2Se3:Ca and Bi2Te3:Mn single crystals using Li+8 implanted to depths on the order of 100 nm. Above ∼200K, spin-lattice relaxation reveals diffusion of Li+8, with activation energies of ∼0.4eV (∼0.2eV) in Bi2Se3:Ca (Bi2Te3:Mn). At lower temperatures, the NMR properties are those of a heavily doped semiconductor in the metallic limit, with Korringa relaxation and a small, negative, temperature-dependent Knight shift in Bi2Se3:Ca. From this, we make a detailed comparison with the isostructural tetradymite Bi2Te2Se [McFadden, Phys. Rev. B 99, 125201 (2019)2469-995010.1103/PhysRevB.99.125201]. In the magnetic Bi2Te3:Mn, the effects of the dilute Mn moments predominate, but remarkably the Li+8 signal is not wiped out through the magnetic transition at 13 K, with a prominent critical peak in the spin-lattice relaxation that is suppressed in a high applied field. This detailed characterization of the Li+8 NMR response is an important step toward using depth-resolved β-NMR to study the low-energy properties of the chiral topological surface state in the Bi2Ch3 tetradymite topological insulator. ©2024 American Physical Society.