Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier
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arXiv
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| Format: | Preprint |
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2024
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| author | Asaduzzaman, Md McFadden, Ryan M. L. Thoeng, Edward Laxdal, Robert E. Junginger, Tobias |
| author_facet | Asaduzzaman, Md McFadden, Ryan M. L. Thoeng, Edward Laxdal, Robert E. Junginger, Tobias |
| contents | We report measurements of the first-flux-penetration field in surface-treated and coated Nb samples using muon spin rotation ($μ$SR). Using thin Ag foils as energy moderators for the implanted muon spin-probes, we "profile" the vortex penetration field $μ_{0} H_{\mathrm{vp}}$ at sub-surface depths on the order of $\sim 10$ $\mathrmμ$m to $\sim 100$ $\mathrmμ$m. In a coated sample [Nb$_3$Sn(2 $\mathrmμ$m)/Nb], we find that $μ_{0} H_{\mathrm{vp}}$ is depth-independent with a value of 234.5(35) mT, consistent with Nb's metastable superheating field and suggestive of surface energy barrier for flux penetration. Conversely, in a surface-treated sample [Nb baked in vacuum at 120 $^{\circ}$C for 48 h], vortex penetration onsets close to pure Nb's lower critical field $μ_{0}H_\mathrm{c1} \approx 170$ mT, but increases with increasing implantation depth, consistent with flux-pinning localized at the surface. The implication of these results for technical applications of superconducting Nb, such as superconducting radio frequency (SRF) cavities, is discussed. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2402_15500 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier Asaduzzaman, Md McFadden, Ryan M. L. Thoeng, Edward Laxdal, Robert E. Junginger, Tobias Superconductivity We report measurements of the first-flux-penetration field in surface-treated and coated Nb samples using muon spin rotation ($μ$SR). Using thin Ag foils as energy moderators for the implanted muon spin-probes, we "profile" the vortex penetration field $μ_{0} H_{\mathrm{vp}}$ at sub-surface depths on the order of $\sim 10$ $\mathrmμ$m to $\sim 100$ $\mathrmμ$m. In a coated sample [Nb$_3$Sn(2 $\mathrmμ$m)/Nb], we find that $μ_{0} H_{\mathrm{vp}}$ is depth-independent with a value of 234.5(35) mT, consistent with Nb's metastable superheating field and suggestive of surface energy barrier for flux penetration. Conversely, in a surface-treated sample [Nb baked in vacuum at 120 $^{\circ}$C for 48 h], vortex penetration onsets close to pure Nb's lower critical field $μ_{0}H_\mathrm{c1} \approx 170$ mT, but increases with increasing implantation depth, consistent with flux-pinning localized at the surface. The implication of these results for technical applications of superconducting Nb, such as superconducting radio frequency (SRF) cavities, is discussed. |
| title | Measurements of the first-flux-penetration field in surface-treated and coated Nb: Distinguishing between surface pinning and an interface energy barrier |
| topic | Superconductivity |
| url | https://arxiv.org/abs/2402.15500 |