Low-field phenomenology and characteristic lengths of hydrogen- and halogen-doped YBa2Cu3O7-delta compounds

We measure the diamagnetic response of YBa(2)Cu(3)O(y)A(x) (A = Cl, F, H) c eramics. We obtain low-field effective penetration depths lambda of a few 1 0 mu m, first flux-penetration field H-1 distinguishable from the volume pe netration field H-C1 and two characteristic temperatures T-s and T-c, T-c < T-s, defined by the onset of the real and imaginary parts of the susceptib ility, respectively. H-1(T) goes to zero as a power law H-1(T, x) = H-1(0, x) (T - T/T-c)(2.7) near T-c. From the values of lambda and H-1 we infer th e correlation length xi at T = 4.2 K. A large range of values for xi(4.2) s uggests that chemical disorder plays an essential role in the phenomenology of cuprates. We find lambda(4.2) similar to H-1(4.2)-(113). This, and the power law xi(4.2) - H-1(4.2)(-2/3) result from the scaling properties of a phase transition governed by disorder.