The compound PrBa2Cu3O7 −y is not superconducting while most other RBa2Cu3O7 −y (R=rare earth) compounds exhibit superconductivity in the 90K range. The system PrBa2 −xPrxCu3O7 −x has been prepared to study the effect of excess Pr at the Ba site on the structure, resistivity and magnetic behaviour of this system. It is observed that single-phase compounds in the above series form forx=0·8—that is up to the composition Pr1·8Ba1·2Cu3O7 −y. While stoichiometric PrBa2Cu3O7 −y is orthorhombic, the compounds with excess Pr show tetragonal structure. Four-probe dc resistivity measurements show that all the single-phase compounds in the above series do not exhibit superconductivity and are semiconducting down to 12 K. Magnetic susceptibility measurements reveal deviation from Curie-Weiss behaviour starting at a characteristic temperature, which is taken to be the ordering temperature (TN) of the Pr moments. BothTN and overall resistivity decrease with increasingx and may have a common origin.
Volume 42 | Issue 6
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