Critical current as a function of temperature in thin YBa2Cu3O7−δ films

The critical current Ic of several triode-sputtered and laser-ablated thin YBa2Cu3O7−δ films is investigated over the temperature range of 5–85 K. Near the critical temperature Tc it is found that Ic∝(1−T/Tc)γ with γ≂1.5–2. The value of γ depends very sensitively on the value determined for Tc. The low-temperature data, for temperatures below about 0.6Tc, can be well analyzed in terms of a proximity-effect model. The effective barrier thickness dN between superconducting parts of the samples is of the order of a few nanometers for all samples studied.