High critical current density and its field dependence in mixed rare earth (Nd,Eu,Gd)Ba2Cu3O7-δ thin films

Compared with mono-rare earth 123 films, ternary rare earth (Nd,Eu,Gd)Ba2Cu3O7-delta (NEG123) films show higher critical current density (J(c)) and improved irreversibility field (H-irr), but no increase in the characteristic field corresponding to a crossover from a low-field plateau to a linear region in a log J(c)-log H plot. At intermediate fields, J(c) vs H scales as H(-0.5+/-0.05) for NEG123, in contrast to H(-0.73+/-0.05) for mono-rare earth samples such as Gd123. The slow power decay of J(c) vs H together with the improved J(c) and H-irr strongly implies that extra flux pinning centers exist in NEG123, which are thought to be noncorrelated stress fields induced by lattice mismatch. (C) 2004 American Institute of Physics.