Modified London model for the determination of λ and ζ in a high κ superconductor

Abstract

We present a modified London model suggested by Brandt [1–3] which introduces a finite vortex core size appropriate for isotropic superconductors in which the average internal field is less than approximately (1/4)Hc2. TheμSR lineshape resulting from this model possesses a distinctive shape due to the magnetic penetration depth λ and the vortex core diameter (approximately equal to twice the coherence length ζ). However, for a given lineshape, there is a large range of values of λ and ζ which produce nearly the same lineshape. Lineshape smearing caused by disorder in the vortex lattice increases uncertainty in values for λ and ζ. If well-determined values of either λ(T) or ζ(T) are not available from another technique, both of them can be determined byμSR measurements alone if runs in more than one applied field at the same temperature are fit with λ and ζ as shared parameters. We also present our method of estimating the degree of disorder in the vortex lattice.