Paper

Depth-resolved measurement of the Meissner screening profile in a niobium thin film from spin-lattice relaxation of the implanted \\(\\beta\\)-emitter \\(^{8}\\)Li

Asaduzzaman, Md, MacFarlane, W Andrew, Laxdal, Robert E, Buck, Terry J, Dunsiger, Sarah R, Morris, Gerald D, Dehn, Martin H, Pearson, Matthew R, Levy, C D Philip, Thoeng, Edward, McFadden, Ryan M L, Kiefl, Robert F, Junginger, Tobias, Cortie, David L

2023

Overview

We report measurements of the Meissner screening profile in a Nb(300 nm)/Al\\(_{2}\\)O\\(_{3}\\) thin film using \\(^{8}\\)Li \\(\\beta\\)-detected nuclear magnetic resonance (\\(\\beta\\)-NMR). The NMR probe \\(^{8}\\)Li was ion-implanted into the Nb film at energies \\(\\leq\\) 20 keV, corresponding to mean stopping depths comparable to Nb's magnetic penetration depth \\(\\lambda\\). \\(^{8}\\)Li's strong dipole-dipole coupling with the host \\(^{93}\\)Nb 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/T_{1}\\). From a fit of the \\(1/T_{1}\\) data to a model accounting for its dependence on temperature, magnetic field, and \\(^{8}\\)Li\\(^{+}\\) implantation energy, we obtained a magnetic penetration depth \\(\\lambda_{0}\\) = 51.5(22) nm, consistent with a relatively short carrier mean-free-path \\(\\ell\\) = 18.7(29) nm typical of similarly prepared Nb films. The results presented here constitute an important step towards using \\(^{8}\\)Li \\(\\beta\\)-NMR to characterize bulk Nb samples with engineered surfaces, which are often used in the fabrication of particle accelerators.

• Publisher: Cornell University Library, arXiv.org
• Subject: Aluminum / Cross relaxation / Dipole interactions / Emitters / Magnetic fields / Niobium / NMR / Nuclear magnetic resonance / Particle accelerators / Penetration depth / Screening / Spin-lattice relaxation / Temperature dependence / Thin films