Enhanced flux pinning by Fe point defects in Bi 2Sr 2Ca(Cu 1− xFe x) 2O 8+ δ single crystals

Abstract

We study the flux pinning of Bi 2Sr 2CaCu 2O 8+ δ (Bi2212) single crystals doped with up to 2.2% of Fe on the Cu positions using measurements of magnetization hysteresis loop. We found that the critical current density increased with the doping for doping less than 0.5 at.%. This proves that Fe point defects contribute to the flux pinning. However, high doping levels deteriorate the J c. The effect of Fe doping on the peak effect was also studied. The peak position shifts to high temperature, but the peak field decreased with increasing doping levels.