Flux distribution and penetration depth measured by muon spin rotation in high-T_{c} superconductors

Abstract

The determination of the magnetic penetration depth \ensuremath{\lambda} in type-II superconductors from the field distribution n(B) measured by muon-spin rotation (\ensuremath{\mu}SR) is discussed. Particular stress is put on high-${T}_{c}$ oxide superconductors (coherence length \ensuremath{\xi}\ensuremath{\ll}\ensuremath{\lambda}; upper critical field much greater than the applied field; anisotropy and pinning). Fitting of the highly asymmetric n(B) by a Gaussian or Lorentzian, as done in existing \ensuremath{\mu}SR experiments, yields for a perfect vortex lattice \ensuremath{\lambda} values which are too large, and for a strongly distorted (due to pinning) lattice \ensuremath{\lambda} values which are too small. An improved evaluation of \ensuremath{\mu}SR data is suggested.