Measurement of the London penetration depths in YBa₂Cu₃O_x by means of muon spin rotation (μSR) experiments

To get accurate values of the London penetration depths in YBa2Cu3Ox, μSR measurements were performed on a high quality, sintered sample and a c-axis-oriented polycrystal. For the sintered sample the temperature dependence of the effective penetration depth λeff is well described by the two-fluid model, with λeff(0) = 155(10) nm. This behavior of λeff(T) is consistent with conventional s-wave pairing. The anisotropy ratio λc λab {reversed tilde equals} 5(1) was determined from measurements on the polycrystal. These results were used to calculate λab(0) = 130(10) nm and λc(0) {reversed tilde equals} 500 - 800 nm. © 1989.