Reconstruction of the electric field in type-II superconducting thin films in perpendicular geometry

Abstract

The study of electric field distributions induced by flux creep in type-II superconducting films allows for important insight into the mechanism of vortex dynamics, the temporal evolution of flux and current distributions, and the occurrence of local losses. Most studies are based on the assumption that a phenomenological materials law, which has been extracted from macroscopic transport measurements, can be also applied to the local electric field during magnetization decay. We evaluate this ansatz by reconstructing the threedimensional-induced E i and potential E p electric fields from experimentally measured time dependence of the flux density distribution. The results are quantitatively compared with solutions of the nonlinear and nonlocal equation of motion for the flux penetration, where the Maxwell equations as well as a materials law are utilized to obtain a two-dimensional E i,2D and E p,2D . We focus our analysis on the electric field distributions on a partially penetrated magnetized state of an epitaxial YBa 2 Cu 3 O 6.95 film.

3D magnetization currents, magnetization loop, and saturation field in superconducting rectangular prisms

“…An interesting issue is that the current loops do not close within the same plane (figure 5). The roughly straight segments close to one side (point 1 at figures 3(c) and 4(c)) bend downwards when approaching the diagonal (point 2 in figures 3(c) and 4(c)), where < J 0 z , reaches a lower layer, where | | J is slightly below J c , and bends in the xy plane, Thickness-average current density for the sample with aspect ratio 0.1 (same situation as figure 3) is consistent with both previous calculations for thin films [14,15] and current density extracted from magnetic-field imaging [28][29][30]. The lines are current lines for the thickness-averaged J.…”

“…Current loops close to the prism side surfaces are still nearly square ( figure 3). Non-square current paths in thin films with regions with |J| < J c were found in [14,15] from numerical modeling and in [27][28][29] from inversion of measured magnetic field maps. Although thin film models assume uniform J along the film thickness, their predictions are valid for the thicknessaveraged J of samples with small but finite thickness.…”

Observation of Transient Overcritical Currents in YBCO Thin Films using High-Speed Magneto-Optical Imaging and Dynamic Current Mapping

“…1 for the current timeline. This central line was chosen in order to avoid inaccuracies in calculation due to transient charges which arise close to the discontinuity lines during field ramping 22,36,37 .…”

Dynamic magneto-optical imaging of superconducting thin films

“…However, investigations into the charge on superconducting films during penetration have shown that square regions near the sample corners do in fact acquire a charge proportional to the rate of external field ramping [37,38], which may invalidate equation (2) in parts of the film, causing slight inaccuracy in the calculated current in these areas. However, the area around a line through the middle of the film bisecting each edge should always remain charge-free [37].…”