High field superconducting properties of Ba(Fe(1−x)Co(x))(2)As(2) thin films

In general, the critical current density, J(c), of type II superconductors and its anisotropy with respect to magnetic field orientation is determined by intrinsic and extrinsic properties. The Fe-based superconductors of the ‘122’ family with their moderate electronic anisotropies and high yet accessible critical fields (H(c2) and H(irr)) are a good model system to study this interplay. In this paper, we explore the vortex matter of optimally Co-doped BaFe(2)As(2) thin films with extended planar and c-axis correlated defects. The temperature and angular dependence of the upper critical field is well explained by a two-band model in the clean limit. The dirty band scenario, however, cannot be ruled out completely. Above the irreversibility field, the flux motion is thermally activated, where the activation energy U(0) is going to zero at the extrapolated zero-kelvin H(irr) value. The anisotropy of the critical current density J(c) is both influenced by the H(c2) anisotropy (and therefore by multi-band effects) as well as the extended planar and columnar defects present in the sample.