ISOTOPE EFFECT IN HIGH-T-C MATERIALS - ROLE OF NONADIABATICITY AND MAGNETIC-IMPURITIES

Based on previous calculations of the isotope effect (IE) in supercond uctors, we present a detailed study of the influence of non-adiabatici ty and magnetic impurities on the value of the isotope coefficient (IC ). We focus on the combined effect of these factors and examine how th eir relative weight affects the IC. The isotope effect of the supercon ducting critical temperature T-c, and of the penetration depth delta a re discussed. It is shown that both non-adiabaticity and magnetic impu rities have to be taken into account to describe the oxygen isotope ef fect of Pr-doped and oxygen-depleted YBa2Cu3O7-delta (YBCO). The calcu lations suggest that the effect of magnetic impurities is stronger for Pr-doped than for O-depleted YBCO. We also present new results for th e IC of delta in O-depleted YBCO.