Superconducting transition in oxygen deficient YBa2Cu3O7-δ

In this paper we compare the superconductive transition of several oxygen deficient samples measured inductively to that measured resistively and point out important systematic differences between the results of the two types of measurements. Superconducting transition temperatures were determined by magnetic shielding measurements in a low field SQUID magnetometer in fields of 2 Gauss. The measurements were carried out by cooling the sample to 4.2 K in zero field, applying the measuring field and taking data on warming. Resistivity measurements were made by the four probe AC technique at frequency of 100 Hz and with a measuring current of 1.5 mA.