Anomalous behavior of the diamagnetic profile of superconducting niobium near a vacuum boundary
Korneev D. A., Chernenko L. P., Petrenko A. V., Balalykin N. I., Skrypnik A. V.
The profile of a static magnetic field penetrating into superconducting niobium films has been measured by specular reflection of polarized thermal neutrons. At a temperature of 4.9 K, a field of 500 Oe penetrates essentially unweakened to a depth ξ = 28 nm at a vacuum interface. The reason is a suppression of the order parameter of the superconductor near the surface. Deeper in the film, the field falls off by a London law with a constant Λ = 45 nm. The measurements were carried out on the SPN polarized-neutron spectrometer of the IBR-2 pulsed reactor of the Joint Institute for Nucelar Research at Dubna.