The resistive critical field of niobium (columbium) wire

Abstract

The transverse and longitudinal resistive critical fields of niobium (columbium) wires with drawing strains up to eleven were measured. The magnitude and anisotropy of the resistive critical field can both be much greater than the bulk Ginzburg-Landau parameters indicate, even if “internal surface” nucleation of superconductivity is assumed. It is suggested that these effects are due to superconductivity in the dislocation cell walls created by drawing or swaging. A simple model for this effect is offered, and various experiments which test this model are discussed.