Magnetic penetration depth and flux dynamics in single-crystal Bi2Sr2CaCu2O8+δ

The muon-spin-relaxation technique has been used to study vortex dynamics in single-phase superconducting single crystals of Bi2Sr2CaCu2O8+δ (Tc≊90 K). The data indicate motional narrowing of the internal field distribution due to vortex motion (on a time scale comparable to the muon lifetime). A field-dependent lattice transition is also observed at Tx∼30 K, as evidenced by the onset of an asymmetric line shape below Tx. Narrowing arising from disordering of the vortices along [001] is also discussed with reference to its effect on the measured penetration depth.