Critical currents in vicinal YBa$_2$Cu$_3$O$_{7-δ}$ films

J. H. Durrell; G. Burnell; Z. H. Barber; M. G. Blamire; J. E. Evetts

doi:10.1103/PhysRevB.70.214508

paper

Critical currents in vicinal YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ films

arXiv:cond-mat/0406620 · doi:10.1103/PhysRevB.70.214508

Abstract

Most measurements of critical current densities in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ thin films to date have been performed on films where the \textit{c}-axis is grown normal to the film surface. With such films, the analysis of the dependence of $j_{c}$ on the magnetic field angle is complex. The effects of extrinsic contributions to the angular field dependence of $j_{c}$ , such as the measurement geometry and disposition of pinning centres, are convoluted with those intrinsically due to the anisotropy of the material. As a consequence of this, it is difficult to distinguish between proposed FLL structure models on the basis of angular critical current density measurements on \textit{c}-axis films. Films grown on mis-cut (vicinal) substrates have a reduced measurement symmetry and thus provide a greater insight into the critical current anisotropy. In this paper previous descriptions of the magnetic field angle dependence of $j_{c}$ in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ are reviewed. Measurements on YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ thin films grown on a range of vicinal substrates are presented and the results interpreted in terms of the structure and dimensionality of the FLL in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ . There is strong evidence for a transition in the structure of the flux line lattice depending on magnetic field magnitude, orientation and temperature. As a consequence, a simple scaling law can not, by itself, describe the observed critical current anisotropy in YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ . The experimentally obtained $j_{c} (θ)$ behaviour of YBCO is successfully described in terms of a kinked vortex structure for fields applied near parallel to the \textit{a-b} planes.

10 pages, 12 figures, Submitted to PRB

Critical currents in vicinal YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ films

Abstract

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Critical currents in vicinal YBa2​Cu3​O7−δ​ films

Abstract

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Critical currents in vicinal YBa $_{2}$ Cu $_{3}$ O $_{7 - δ}$ films