Abstract
The peak effect in pure and heavily Pb doped Bi2212 single crystals with different oxygen doping levels were studied by measuring M-H loops. The peak effect in pure Bi2212 crystals was obtained only for crystals with optimum oxygen doping and overdoping but not for oxygen underdoping. For Pb-doped Bi2212 crystals, a strong peak effect appeared in higher field than in pure crystals and it persisted up to T c. Formation and decomposition of Bi 5+ and/or Pb 4+ rich clusters, which caused the reduction of c-axis and ϱ c, were proposed to be responsible for the appearance and disappearance of the peak effect in pure and Pb doped crystals. The peak effect was characterised by plotting (H max-H min)/H max vs T/T c, where H max and H min represents the field in which the magnetisation reaches maximum and starts to increase around secondary peak position, respectively. Results showed that the evolution of the peak effect with temperature in the Pb doped crystals was similar to that in Y123.
Published Version
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