Superconductivity and antiferromagnetism in Cu(2) layers of RBa₂Cu₃O₂

The systems Y_1-xPr_xBa₂Cu₃O_z with x=0 to 1 and YBa₂(Cu_1-yM_y)₃O_z, MFe and Co, with y=0 to 0.26, and z=6 and 7, doped with ⁵⁷Fe, have been studied by dc magnetometry to determine the superconducting phase transition temperature and by ⁵⁷Fe Mössbauer spectroscopy to determine the antiferromagnetic phase transition temperature T_N of the Cu(2) site. In those cases where substitution is made out of the CuO₂ planes, for z=7, T_c is reduced with increasing the dopant concentration. Antiferromagnetism is found at concentrations where the superconductivity disappears, which means that the materials exhibit either superconductivity or antiferromagnetic order, depending on composition. The phase diagrams obtained are very similar to the well-known oxygen content dependence phase diagram. For z=6, T_N changes very little with x or y. There is no conclusive evidence for overlap of superconductivity and antiferromagnetism. For substitution of Zn in the CuO₂ plane (Zn) a different behavior is observed. Here the magnetic order is never found in oxygen rich samples, and appears in oxygen poor samples only for y<0.08.