We measure the diamagnetic response of YBa2Cu3OyAx (A = Cl, F, H) ceramics. We obtain low-field effective penetration depths λ of a few 10 μm, first flux-penetration field HI distinguishable from the volume penetration field HCI and two characteristic temperatures Ts and Tc, Tc < Ts, defined by the onset of the real and imaginary parts of the susceptibility, respectively. HI(T) goes to zero as a power law HI(T, x) = HI(0, x) (T - T/Tc)2.7 near Tc. From the values of λ and HI we infer the correlation length ξ at T = 4.2 K. A large range of values for ξ(4.2) suggests that chemical disorder plays an essential role in the phenomenology of cuprates. We find λ(4.2) ∼ HI(4.2)-1/3. This, and the power law ξ(4.2) ∼ HI(4.2)-2/3 result from the scaling properties of a phase transition governed by disorder.
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Materials Science (all)
- Condensed Matter Physics