Magnetic field distribution and characteristic fields of the vortex lattice for a clean superconducting niobium sample in an external field applied along a three-fold axis

Abstract

The field distribution in the vortex lattice of a pure niobium single crystal with an external field applied along a three-fold axis has been investigated by the transverse-field muon-spin-rotation (TF-μSR) technique over a wide range of temperatures and fields. The experimental data have been analyzed with Delrieu's solution for the form factor supplemented by phenomenological formulas for the parameters. This has enabled us to experimentally establish the temperatures and fields for Delrieu's, Ginzburg and Landau's, and Klein's regions of the vortex lattice. Using the numerical solution of the quasiclassical Eilenberger equation, the experimental results have been reasonably understood. They should apply to all clean BCS superconductors. Delrieu's analytical model supplemented by phenomenological formulas for its parameters is found to be reliable for analyzing TF-μSR experimental data for a substantial part of the mixed phase. Abrikosov's limit is contained in it. © 2014 American Physical Society.