The resistance of a preferentially oriented thin film of Y2Ba4Cu8O16−δ has been measured as a function of temperature and fields up to 20 T oriented parallel to the c-axis. The normal state resistance could be well fitted by the Bloch-Grüneisen theory. Below Tc (≈ 80 K) the resistance transitions both in field and temperature could be separated in three regimes. A regime where the data can be analysed in terms of a model combining thermally activated flux flow and flux pinning due to dislocation lines. The upper critical field Bc2, obtained from this analysis, exhibits an upward curvature at low temperatures, possibly indicating a mixed s-d wave pairing. In the second regime just below Bc2 viscous forces are increasingly important for flux-line motion and the resistance is determined by the flux-flow resistance ϱf. At fields higher than Bc2 we find a large contribution of superconducting fluctuations to the conduction.

Preferentially oriented thin films of YBa2Cu3O7 (123) and YBa2Cu4O8 (248) with the c-axis perpendicular to the substrate have been prepared by e-gun evaporation from Y, BaF2 and Cu. Critical current and resistance transition measurements have been carried out in magnetic fields parallel to the c-axis. The results will be analysed in terms of a model for thermally activated flux flow combined with two models for flux pinning, one in which the pinning is predominantly caused by twin boundaries and a second in which pinning by dislocations is considered. The resistance broadening in the 248 is well described by the model with dislocation pinning. The Bc2 (T) values obtained from the fits compare well with estimates from the fluxflow resistivity and a kink in the resistance vs field curves. The slope of Bc2 at Tc is 0.37 T/K, a factor four smaller than in the 123.

Critical currents of YBa2Cu3O7 - δ epitaxial films, obtained by co-evaporation of yttrium, copper and BaF2 in an ultrahigh vacuum system, were measured using resistometric and magnetic torque methods. Typical values of jc $ ̌2 × 1011 A m-2 at 4.2 K and 4 × 1010 A m-2 at 77 K were found. In spite of their good quality these films exhibited large magnetic relaxation even at 4.2 K. Using the results of Monte-Carlo simulations of thermally activated flux motion for the analysis of the relaxation data typical values of 25 ± 3 meV were found for the activation energy U of flux motion at 4.2 K. It is shown that the occurrence of highjc values and small activation energies is not inconsistent in high Tc superconductors because of their short coherence lengths.

With a two coil mutual inductance technique the in plane penetration depth in compact YBaCuO films was measured to be λ (0) ≅ 0.23 μm. In granular YBaCuO films the penetration depth is larger, its value is being determined by the strength of the intergranular Josephson coupling energy.

In this erratum we want to point out that our interpretation and conclusion concerning the closing of our magnetisation curves is not correct. The fact that in our measurements the hysteresis curves close is due to the specific measuring method used in our Quantum Design MPMS SQUID magnetometer, combined with the small length of uniformity of the superconducting magnet. It is, therefore, not related to the fast relaxation of magnetisation with respect to the long measuring time of the SQUID, as we have argued in our paper. [...]

We present magnetic relaxation measurements on an epitaxial YBa2Cu3O7−δ -film. From these we have obtained the activation energy as a function of temperature for several initial conditions. The absolute value of the activation energy is different for the various cases and it increases with temperature. This last property provides evidence for the presence of a distribution of activation energies.

The critical current density, magnetic hysteresis and relaxation of the magnetisation have been measured on a 1000 ÅYBa2Cu3O7-δ-film in a field perpendicular to the plane of the film. The film was made by co-deposition in a UHV triple e -gun system, using BaF2 as one of sources. The results have been interpreted in terms of flux pinning and creep of curved flux lines with locally different pinning energies.

Resistance measurements are reported, carried out on highly textured thin films of YBa2Cu3O7 − gd prepared by co-evaporation of BaF2, copper and yttrium on (100) SrTiO3 in a triple e-gun UHV system, adding oxygen during deposition. The polycrystalline films, with average grain size of the order of 10 μm, show a strong preferential orientation, with the c axis perpendicular to the substrate. The resistance measurements in a field parallel to the c axis have been interpreted in terms of a model combining thermally activated flux flow and flux pinning by twin boundaries. The agreement is satisfactory. The field and temperature dependence of the activation energy differs essentially from expressions proposed recently.

High TC superconducting thin films were prepared on (100) SrTiO3 substrates by dc triode sputtering and subsequent annealing. In these films Hall-bar structures having a width down to 5 μm were patterned using a reactive ion etching technique. Superconductivity above 77 K was observed. When compared with the original film there is only a small reduction in TC. The critical current density determined by electrical measurements is substantially reduced. On the other hand, the critical current density in the bulk of the grains as measured by the torque on a film is not reduced by the patterning process. It is suggested that superconductor-normal metal-superconductor junctions between the grains account for this difference.