Various regimes of flux motion in Bi2Sr2CaCu2O8+δ single crystals

Abstract Four regimes of vortex motion were identified in the magnetoresistance of Bi2Sr2CaCu2O8+δ single crystals: (1) thermally activated flux flow (TAFF) in samples with surface defects caused by thermal annealing; (2) TAFF-like plastic motion of highly entangled vortex liquid at low temperatures, with Upl ∼ (1 − T/Tc)/H 1 2 ; (3) pure free flux flow above the region of (2) in clean and optimally doped samples; or, in its place, (4) a combination of (2) and (3). This analysis gives an overall picture of flux motion in Bi cuprates.