Browsing by Author "Buck, TJ"

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    Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted β-emitter 8Li
    (AIP Publishing, 2023-10-28) McFadden, RML; Asaduzzaman, M; Buck, TJ; Cortie, DL; Dehn, MH; Dunsiger, SR; Kiefl, RF; Laxdal, RE; Levy, CDP; MacFarlane, WA; Morris, GD; Pearson, MR; Thoeng, E; Junginger, T
    We report measurements of the Meissner screening profile in a Nb(300 nm)/Al2O3 thin film using 8Liβ-detected nuclear magnetic resonance (β-NMR). The NMR probe 8Li was ion-implanted into the Nb film at energies ≤ 20 keV, corresponding to mean stopping depths comparable to Nb’s magnetic penetration depth λ. 8Li’s strong dipole–dipole coupling with the host 93Nb nuclei provided a “cross-relaxation” channel that dominated in low magnetic fields, which conferred indirect sensitivity to the local magnetic field via the spin-lattice relaxation (SLR) rate 1/T1. From a fit of the 1/T1 data to a model accounting for its dependence on temperature, magnetic field, and 8Li+ implantation energy, we obtained a magnetic penetration depth λ0= 51.5(22) nm, consistent with a relatively short carrier mean-free-path ℓ= 18.7(29) nm typical of similarly prepared Nb films. The results presented here constitute an important step toward using 8Liβ-NMR to characterize bulk Nb samples with engineered surfaces, which are often used in the fabrication of particle accelerators. © © 2023 Author(s). Published under an exclusive license by AIP Publishing.
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    β-NMR of 8Li+ in rutile TiO2
    (IOP Publishing, 2014-12-16) McFadden, RML; Cortie, DL; Arseneau, DJ; Buck, TJ; Chen, CC; Dehn, MH; Dunsiger, SR; Kiefl, RF; Levy, CDP; Li, C; Morris, GD; Pearson, MR; Samuelis, D; Xiao, J; Maier, J; MacFarlane, WA
    We report preliminary low-energy β-NMR measurements of 8Li+ implanted in single crystal rutile TiO2 at an applied field of 6.55 T and 300 K. We observe a broad 12 kHz wide quadrupole split resonance with unresolved features and a sharp component at the Larmor frequency. The line broadening may be caused by overlapping multi-quantum transitions or motion of 8Li+ on the scale of its lifetime (1.21 s). We also find spin-lattice relaxation that is relatively fast compared to other wide band gap insulators. The origin of this fast relaxation is also likely quadrupolar and may be due to anisotropic 8Li+ diffusion. © The Authors CC-BY 3.0