The oxygen nonstoichiometry, structure, magnetic and calorimetric data for La doped Ba-site PrBa2-xLaxCu3Oz systems (0≤x≤1 and 6.881≤z≤ 7392) are reported. The x-dependence of the oxygen content increases monotonically and two structural phase transitions are observed, confirmed by powder x-ray Rietveld analysis, from the orthorhombic 1212C-phase (space group: Pmmm) to tetragonal 1212 (P4/mmm) at x = 0.45, and then to another orthorhombic (Cmmm) phase around x = 0.7. Magnetic susceptibility and heat capacity measurements show that the anomalous Néel temperature TN(Pr) decreases monotonically from 18 K for x = 0 to 2.8 K for PrBa1.3La0.7Cu3O7.236 and to below 2 K for x≥0.8 for samples prepared under the same conditions, while TN(Pr) increases with an increase of oxygen content for the same compound. The increasing Pr-O bond length observed with decreasing TN(Pr) indicates that this unusual Pr magnetic ordering is closely related to the wave-function overlap between the Pr-4f orbital and eight O-2pπ orbital in the CuO2 bi-layer. No superconductivity has been detected for these insulating cuprates.
Superconductor Science and Technology 14(6), pp.320-325