High critical flux density gradients near the surface of superconducting niobium

Abstract

The profiles of the magnetic induction near the surface of cylindrical niobium samples were measured by the method of differential susceptibility in minor hysteresis loops. The flux density gradient near the surface generally is considerably higher than in the bulk. This may be interpreted in terms of a surface barrier or of a surface pinning force. The experimental results can be summarized as follows: (1) Surface pinning always increased with surface roughness.(2) When the surface was polished the barrier was only observed in a plastically deformed sample. (3) The influence of the surface seems to extend down to a depth of some tenth of a millimeter.

Superconducting Properties in Arrays of Nanostructured β-Gallium

“…To further explore the magnetization behavior of the nGa samples a minor hysteresis loop 27 , 28 , was measured on top of the second MH curve at , represented by open stars in the first quadrant of Fig. 2 , with an inverted vertical scale at the right axis.…”

Properties of the distorted flux-line lattice near a planar surface

“…The first term, Uv= 89 (13) describes the interaction of all line elements dr~ with all line elements dr~ and with all images d~ by a three-dimensional, spherically symmetric potential V3(lrl),…”

“…From pinning experiments the shear stiffness is expected to be smaller near the surface. 13 We calculate the shear energy for the most important case where the FLL planes are sheared parallel to the surface. The interaction potential of parallel FLL planes is derived in Appendix B,…”