Suppression of magnetic granularity by transport current in (Bi,Pb)2Sr2Ca2Cu3Ox tapes

Using the magneto‐optical technique, transport current flow in (Bi,Pb)2Sr2Ca2Cu3Ox (BSCCO) Ag‐sheathed tapes has been imaged. For zero transport current, I, the magnetization currents display a pronounced macroscopic magnetic granularity (on a scale larger than the actual grain size) characterized by a percolative distribution of current loops. By applying I≊0.8Ic this granular behavior was largely replaced by a more uniform current flow. Due to the significant dependence of Ic on E in BSCCO, the extent to which the magnetic granularity is observed strongly depends on the magnetic prehistory and on the electric field E, whose characteristic values are very different for magnetization and transport measurements.