Superconducting and magnetic properties of Ba2LnCu3O7−x compounds (Ln=lanthanides)

The superconducting and magnetic properties of a series of compounds Ba₂LnCu₃O_7–x (Ln=Pr, Nd, Sm ... Gd, Dy ... Yb) are reported and compared with corresponding measurements on the isostructural model substance Ba₂YCu₂O_7–x . The unknownx in the oxygen concentration is obviously responsible for a nonmonotonic variation of bothT _c and the lattice constants with the rare-earth size. No remarkable increase ofT _c was achieved on replacing Y by a magnetic Ln. A partial substitution of Ba by Sr reducedT _c, but increasedT _N of Ba₂GdCu₃O_7–x from 2.3 K to 2.65 K in BaSrGdCu₃O_7–x . Intrinsic pinning effects in external magnetic fields appear to be surprisingly weak at higher temperatures where technical applications of this sort of superconductors might be of interest.