High field superconducting properties of Ba(Fe1-xCox)2As2 thin films

Abstract

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.