Magnetic order and superconductivity in Y1-xPrxBa2Cu3O7

The system Y_1-xPr_xBa₂Cu_3-yFe_yO_z, with x=0 to 1, y=0 and 0.3, and z=6 and 7, has been studied by ac and dc magnetometry to determine the superconducting phase transition temperature, T_c, by ⁵⁷Fe Mössbauer spectroscopy to determine the antiferromagnetic phase transition temperature of the Cu(2) site, T_N, and by specific-heat measurements to determine γ and the antiferromagnetic ordering temperature of the Pr site, T_n. T_c (x,z=7), T_N (x,z=6,7), and T_n (x,z=7) were obtained for x values of 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0. For z=6, T_N changes very little with x [T_N(0,6)=415 K and T_N(1,6)=350 K], but for z=7, T_N changes sharply with x [T_N(1,7)=325 K, T_N(0.6,7)=230 K, and T_N(0.4,7)<=35 K]. There is no conclusive evidence for overlap of superconductivity and antiferromagnetism. T_n also decreases strongly with decreasing x, T_n(1,7)=17 K, while T_n(0.4,7)<=2.5 K. The specific-heat measurements show large linear temperature terms. The slope γ increases strongly with x and with the introduction of the Fe probe.