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Magnetization hysteresis loops and relaxation in a twin-free Nd1+ xBa2− xCu3O7− ysingle crystal

Physica C Superconductivity
Publication Date
DOI: 10.1016/s0921-4534(98)00112-9
  • Minor And Large Hysteresis Loops
  • Critical Current Density
  • Flux Pinning
  • Relaxation


Abstract We have measured the minor (MHL) and large hysteresis loops (LHL) in a twin-free Nd 1+ x Ba 2− x Cu 3O 7− y (NdBCO) single crystal exhibiting fish-tail peak effect (FTPE) at high temperature and high field. At low temperature, both MHL and LHL can be explained using the exponential model. However, this model is found not to be valid to explain the loops at high temperature where FTPE is observed. The main reason for this is the exponential decay of the central peak with increasing temperature and field and the rapid fall of the penetration field (field necessary to reach centre of the sample) into the crystal. The field and temperature dependence of the critical current clearly demonstrates the interplay of two separate pinning regimes, one from the central peak at low temperature and another from the FTPE emerging with the increasing field and temperature. The minimum in FTPE is believed to be caused by the superposition of two pinning processes. The dynamic magnetic relaxation carried out over a whole temperature region distinguishes two different pinning process which is observed from a crossover from the relaxation rate. The relaxation process at high temperature scales well with the FTPE peak field displaying that pinning due to FTPE is dominated at high fields and at high temperatures.

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