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Magnetic penetration depths in Y2Ba4Cu6+nO14+n−δ and local-pair condensation

1991; Elsevier BV; Volume: 158; Issue: 9 Linguagem: Inglês

10.1016/0375-9601(91)90464-j

1873-2429

Eduardo J. Ansaldo, Ch. Niedermayer, J. L. Tallon, D. Pooke, J. H. Brewer, G.D. Morris,

Advanced Condensed Matter Physics

The magnetic penetration depth λ(T) has been measured by means of positive-muon spin rotation and relaxation for YBa2Cu4O8, Y2Ba4Cu7O15minus;δ and quenched YBa2Cu3O7minus;δ samples, altogether spanning a range of critical temperatures (Tc) from 29 to 90 K. The extrapolated (T→0) spin relaxation rate (proportional to λ(0)minus;2, and thus to the ratio of density to effective mass nsm∗ for the superconducting condensate) for YBa2Cu4O8 and Y2Ba4Cu7O15minus;δ increases almost linearly with Tc, similar to th e monotonic increase of Tc with decreasing δ previously determined for Y2Ba4Cu7O15minus;δ. Within the framework of models based on Bose condensation of local pairs, the data indicate that the double-chain ribbons play a more active role in the superconductivity than as mere charge reservoirs.