To get accurate values of the London penetration depths in YBa 2 Cu 3 O x, 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 λ eff is well described by the two-fluid model, with λ eff (0)= 155 (10) nm. This behavior
of λ eff (T) is consistent with conventional s-wave pairing. The anisotropy ratio λ c λ ab⋍ 5 (1)
was determined from measurements on the polycrystal. These results were used to calculate …