Flux domes in weak-pinning superconducting films without edges

[摘要] Domelike magnetic-flux-density distributions previously have been observed experimentally and analyzed theoretically in superconducting films with edges, such as in strips and thin plates. Such flux domes have been explained as arising from a combination of strong geometric barriers and weak bulk pinning. In this paper we predict that, even in films with bulk pinning, flux domes also occur when vortices and antivortices are produced far from the film edges underneath current-carrying wires, coils, or permanent magnets placed above the film. Vortex-antivortex pairs penetrating through the film are generated when the magnetic field parallel to the surface exceeds H(c1)+K(c), where H(c1) is the lower critical field and K(c)=j(c)d is the critical sheet-current density (the product of the bulk critical current density j(c) and the film thickness d). The vortices and antivortices move in opposite directions to locations where they join others to create separated vortex and antivortex flux domes. We consider a simple arrangement of a pair of current-carrying wires carrying current I(0) in opposite directions and calculate the magnetic-field and current-density distributions as a function of I(0) both in the bulk-pinning-free case (K(c)=0) and in the presence of bulk pinning, characterized by a field-independent critical sheet-current density (K(c)> 0).

[发布日期] 2006-12-01

[关键词] CRITICAL-CURRENT-DENSITY;II SUPERCONDUCTORS;MAGNETIC-FLUX;THIN-FILMS;NONDESTRUCTIVE DETERMINATION;GEOMETRICAL BARRIER;INTERMEDIATE STATE;SURFACE-BARRIER;PENETRATION;TEMPERATURE