Structure and superconductivity of Dy(Ba2-yLay)Cu3Oz (0≤y≤0.5) system

Structural and superconducting properties of single-phase La-substituted compounds of the formula Dy(Ba2-yLay)Cu3Oz (0.0less than or equal toyless than or equal to0.5) have been investigated by neutron diffraction, electrical resistivity, and magnetization measurements. The compound DyBa2Cu3O7-delta (orthorhombic, space group Pmmm) exhibits superconductivity with transition temperature, T-c, of about 90 K. Rietveld analysis of the neutron diffraction data on La containing compounds reveals that the orthorhombicity decreases with increasing La concentration and the compounds become tetragonal for higher La content. The overall oxygen content increases as divalent Ba is replaced by trivalent La and approximately compensates for the difference in the valence state of these two ions. The superconducting transition temperature, obtained from low field magnetization and/or four-probe resistivity measurements, decreases from similar to90 K for y=0.0 to similar to34 K for y=0.5. The depression in T-c in Dy(Ba2-yLay)Cu3Oz system is attributed to hole filling/localization caused by the rare earth substitution at the Ba site. (C) 2002 American Institute of Physics.