Precursor superconducting diamagnetism in YBa2Cu3O7-δ with in-plane or intercalated magnetic impurities

The magnetization around the superconducting transition was measured in YBa2Cu3O7-delta with magnetic impurities in the CuO2 layers (Cu substituted by Zn or Ni) or between them (Y substituted by Gd or Pr). While some of these impurities have an important effect on the superconducting transition temperature (T-c), the precursor diamagnetism observed above T-c is not appreciably affected. This result contrasts with recent observations in a conventional BCS superconductor (La), in which the precursor diamagnetism was found to increase several orders of magnitude with the addition of a small amount (a few atomic per cent) of Gd or Pr magnetic impurities.