Abstract
Magnetic hysteresis loops and magnetic relaxation have been measuredfor pure and heavily lead-doped Bi2-xPbxSr2CaCu2Oy (Bi2212)single crystals. From the hysteresis loop measurements, the normalizedcritical current density Jc/Jc0 has been calculated, and from therelaxation measurements the activation energy, current-voltage curves andnormalized relaxation rate have been obtained. The field and temperaturedependences of Jc/Jc0 for Pb-doped crystals were much weaker than forthe pure Bi2212 crystals. A large upward shift in the crossover temperatureTCR, a temperature separating two different pinning regimes, has beenobserved for the first time with heavy lead doping. This was interpreted byimproved inter-layer Josephson coupling of two-dimensional vortices, as aresult of Pb doping. Heavily Pb-doped crystal had TCR = 35 K for the fieldthat was within the secondary peak in its magnetic hysteresis loop. For pureBi2212, TCR = 19 K.
Published Version
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