RIS ID
20082
Abstract
Magnetic field and angle dependences of the critical current density JcH, in epitaxial c-oriented YBa2Cu3O7−delta thin films are measured by the four-probe transport current technique, low-frequency ac magnetic susceptibility, and superconducting quantum interference device magnetometry. The films under study are deposited by off-axis dc magnetron sputtering onto r-cut sapphire substrates buffered with a CeO2 layer. A consistent model of vortex pining and supercurrent limitation is developed and discussed. Rows of growthinduced out-of-plane edge dislocations forming low-angle boundaries LAB’s are shown to play a key role in achievement of the highest critical current density Jc2106 A/cm2 at 77 K. The model takes into account the transparency of LAB’s for supercurrent as well as the pinning of vortex lattice on a network of LAB’s. Principal statistical parameters of the film defect structure, such as the domain size distribution and mean misorientation angle, are extracted from JcH curves measured in a magnetic field H applied parallel to the c axis and from x-ray diffraction data. An evolution of angle dependences Jc with H is shown to be consistent with the model supposing dominant pinning on edge dislocations. Strongly pinned vortices parallel to the c axis appear to exist in tilted low magnetic fields up to a characteristic threshold field, below which the magnetic induction within the film obeys a simple relation B=H cos . This feature is shown to explain the absence of the expected maximum of Jc at Hc in a low applied field. A peak of JcH and an angular hysteresis of Jc, which have been observed in an intermediate-field range, are discussed in terms of film thickness, surface quality, and orientation of the applied field. The observed effects are found to be consistent with the developed model.
Publication Details
This article was originally published as: Pan, V, Cherpak, Y, Komashko, V, Pozigun, S, Tretiatchenko, C, Semenov, S, Pashitskii, E & Pan, AV, Supercurrent transport in YBa2Cu3O7–delta epitaxial thin films in a dc magnetic field, Physical Review B, 2006, 73, 054508. Copyright 2006 American Physical Society. The original journal can be found here.