Experiments on Superconducting (Rare Earth)-Ba2Cu3O7-δ down to 30 mK

The crystal structure of RBa2Cu3O7-δ (R = Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb) was analyzed, and the resistivity, ac and dc susceptibility were measured down to 30 mK. They all showed superconductivity at about 90 K. The complete Meissner effect was found to be unchanged down to 30 mK for all specimens except for the Yb compound, which showed a partial breakdown below 1 K. The effective magnetic moments were found to be nearly the same as those of free ionic states except for the Eu compound.