T2 BEHAVIOR IN THE LOW-TEMPERATURE PENETRATION DEPTH OF OXYGEN DEPLETED YBACUO CRYSTALS

We have made AC susceptibility measurements from 4.2 to 100K on two different types of single crystals of yttrium barium copper oxide (Y1Ba2Cu3O7-δ) as a function of oxygen concentration. In both cases as Tc is reduced by oxygen depletion a small T2 term in the low temperature diamagnetic response grows systematically. It follows a similar trend with Tc as does the c-axis resistivity. This, and other evidence indicate that it corresponds to a small T2 term in λc(T) the largest component of the penetration depth tensor. © 1990.