Critical current density in superconducting niobium films

✍ Scribed by R. P. Huebener; R. T. Kampwirth; R. L. Martin; T. W. Barbee; R. B. Zubeck

• Book ID: 104626699
• Publisher: Springer US
• Year: 1975
• Tongue: English
• Weight: 478 KB
• Volume: 19
• Category: Article
• ISSN: 0022-2291
• DOI: 10.1007/bf00116179

✦ Synopsis

We have measured the critical current in Nb strips of 1 #m thickness and different widths w prepared by electron-gun vacuum deposition. The substrate temperature during the deposition was varied between room temperature and 800 ~ C. The width of the Nb strips ranged between 20 and 300 #m. Whereas up to 600~ the different substrate temperatures yielded about the same critical current density Jc (critical current divided by sample cross section), the specimens prepared with 800 ~ C substrate temperature showed a reduction of Jc by a factor of 4-6. In zero applied magnetic field the samples prepared with 400~ substrate temperature or lower showed a decrease of Je roughly proportional to w-a/2. Such behavior can be understood from a homogeneous and field-independent pinning-force density. Our critical current data obtained in an applied perpendicular field, for the high-field regime, were compared with Kramer's theory of flux pinning, which assumes plastic shearing of the flux-line lattice around individual pinning sites during .flux .flow.