OBSERVATION OF A LINEAR REGIME IN IMAGINARY CHI(AC) OF BI-2223 SUPERCONDUCTOR

Measurements of complex AC susceptibility were performed on Bi-2223/Bi -2212 high T-c superconductor at low excitation field amplitudes. Unus ual features attributable to the Bi-2223 phase are observed in the ima ginary part of the AC susceptibility, chi ''(T), at different Excitati on field amplitudes, H-m. The peak temperature, T-p as a function of H -m defines a region in (H, T) plane, where chi '' is independent of H- m. Various possible interpretations are discussed, including that of a transition to a viscous flux flow regime.