Observation of an oxygen isotope effect in superconducting (Y1-xPrx)Ba2Cu3O7- delta.

The oxygen isotope effect was studied in the system (Y{sub 1{minus}{ital x}}Pr{sub {ital x}})Ba{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} for {ital x}=0.2, 0.3, 0.4, and 0.5. It is found that the oxygen isotope exponent {alpha} increases with increasing {ital x} and therefore decreasing transition temperature {ital T}{sub {ital c}}. For the highest Pr concentrations {alpha} tends toward {alpha}=0.5. The value of the isotope exponent depends on the concentration of mobile holes. The lower this concentration is, the larger becomes the isotope exponent.