Effect of geometry on the critical currents of thin films

Journal Article · Sat Jan 01 00:00:00 EST 1994 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.49.1274· OSTI ID:5282798

Stejic, G ^[1]; Gurevich, A ^[2]; Kadyrov, E ^[1]; Christen, D ^[3]; Joynt, R ^[1]; Larbalestier, D C ^[4]

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1. Department of Physics, University of Wisconsin (enMadison, Madison, Wisconsin 53706 (United States))
2. Applied Superconductivity Center, University of Wisconsin (enMadison, Madison, Wisconsin 53706 (United States))
3. Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
4. Applied Superconductivity Center, Department of Physics and Department of Materials Science and Engineering, University of Wisconsin (enMadison, Madison, Wisconsin 53706 (United States))

We consider experimentally and theoretically the effect of the thickness on the critical current density [ital J][sub [ital c]] of superconducting films. In order to eliminate possible contributions from intrinsic pinning, our measurements of [ital J][sub [ital c]]([ital cphi]) as a function of the amplitude and orientation of the magnetic field [bold H] with respect to the film plane were performed on isotropic Nb-Ti films having thicknesses [ital d] ranging from [lambda]/4 to 4[lambda], where [lambda] is the London penetration depth, and [bold H][perpendicular][bold J]. The angular dependent [ital J][sub [ital c]]([ital cphi]) has a sharp peak for [bold H] parallel to the film surface, similar to that observed for high-[ital T][sub [ital c]] films. The amplitude of the peak increases as [ital d] decreases and reaches 20--30 % of the depairing current density ([ital J][sub [ital d]]) for the [lambda]/2 film. The ratio of [ital J][sub [ital c]] values for parallel ([ital J][sub [ital c][parallel]]) and perpendicular ([ital J][sub [ital c][perpendicular]]) film orientation increases as [ital d] decreases, so that [ital J][sub [ital c][parallel]][much lt][ital J][sub [ital c][perpendicular]] for the 4[lambda] film and [ital J][sub [ital c][parallel]][much gt][ital J][sub [ital c][perpendicular]] for the [lambda]/4 film, the crossover occurring at [ital d][approx]2[lambda]. A proposed interpretation of these results is based on our calculations of the vortex behavior in thin ([ital d][much lt][lambda]) films, which give analytical formulas for the field distribution around a fluxon, the lower critical field, [ital H][sub [ital c]1], the surface barrier, and the vortex-vortex interaction potential.

• OSTI ID: 5282798
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 49:2; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
NIOBIUM ALLOYS
CRITICAL CURRENT
TITANIUM ALLOYS
BINARY ALLOY SYSTEMS
MAGNETIC FLUX
SUPERCONDUCTING FILMS
THICKNESS
VORTICES
ALLOY SYSTEMS
ALLOYS
CURRENTS
DIMENSIONS
ELECTRIC CURRENTS
FILMS
665411* - Basic Superconductivity Studies- (1992-)