Anisotropy of Pinning in the Cross Section of a Superconducting Wire

Marked anisotropy of pinning in the cross section of a superconducting niobium-titanium wire was predicted and found experimentally. The pinning of the azimuthal magnetic flux appears to be higher than that of the radial flux; this fact correlates with the character of deformation of the material during the production of wire. The anisotropy of pinning in the cross section of a wire shows up in the behavior of the dependence of the critical current on the applied magnetic field and substantially affects the magnetic moment of the wire in a transverse magnetic filed. Procedures neglecting the real anisotropy of superconducting samples lead to an error in the determination of the critical current density and cause differences in the values determined by the four- probe and contact-free techniques. The use of the newly developed methods and algorithms for the investigation of superconductors with anisotropic pinning allows one to calculate both integral parameters of the wire and the distribution of the magnetic induction and critical current density over the cross section.