Superconducting and magnetic phase boundaries for the heavy fermion system (Y, Pr)Ba2Cu3O7−y

A series of measurements of the structural, electrical, magnetic, and thermal properties are presented for the (Y 1−x Pr x )Ba 2 Cu 3 O 7−y system. Orthorhombic samples for 0⩽ x ⩽1.0 were prepared for all the experiments performed. Unlike nearly all other systems where rare earth (R) are substituted for the Y cation in superconducting YBa 2 Cu 3 O 7−y the substitution of Pr depresses T c , with the critical concentration, x cr = 0.56, for complete suppression of superconductivity. Evidence for magnetic correlations in the superconducting state is presented for x near x cr . Heat capacity and magnetic susceptibility anomalies indicate that it is the Pr ions that order, in agreement with neutron elastic scattering studies. The results suggest that the Pr ions may be almost tetravalent.