Flux pinning properties ofc-axis correlated pinning centres in PLD-YBCO films

Abstract

Flux pinning properties of pinning centres having correlation along the c-axis in epitaxial YBCO films were investigated by measuring the magnetic-field angle ψ-dependence of the critical current density JC and the E–J-characteristics. YBCO films were prepared by using the pulsed-laser-deposition method on four different substrates at three different target-to-substrate distances D. The ψ-dependence of JC showed large peaks when magnetic field B was applied parallel to the c-axis (), and we observed two types of JC-peak: that is, a broad peak for the films deposited at small D (50–60 mm), and a narrow peak for the films deposited at large D (112 and 142 mm). The E–J-characteristics followed the power law, , and the ψ-dependence of the n-value also showed broad peaks around for the films deposited at D = 50–60 mm, and narrow peaks for the film deposited at D = 112 mm. Based on these results and our previous microstructural observations by AFM and TEM, we confirm that the broad-angle flux pinning effect around may be attributed to a high density of elongated precipitates, and the narrow-angle pinning effect around may be attributed to dense planar defects parallel to the c-axis.

Anisotropic connectivity and its influence on critical current densities, irreversibility fields, and flux creep inin situprocessed MgB2strands

“…From the slopes of these lines, which clearly follow the expected relationship E/E 0 = J/J 0 n (e.g. [39]), n-values of from 2 to 7…”

Dirty limit scattering behind the decreased anisotropy of doped YBa2Cu3O7−δthin films

“…According to these results, the change occurs both in pulsed-laser-deposited (PLD) films and chemical-solution-deposited (CSD) films. In PLD-made films, BZO forms columnar, correlated structures [3,4] with diameters below 10 nm [4,5], somewhat larger than the sizes of the vortex cores at low temperatures. In contrast, if films are made by CSD, BZO forms much larger, non-correlated, mostly randomly oriented particles with a diameter of 30 nm [2,6].…”

Atomic interface sequence, misfit strain relaxation and intrinsic flux-pinning defects in different YBa2Cu3O7−δheterogeneous systems

“…Film matrix to enhance its flux-pinning properties under applied magnetic field [7][8][9][10]. Among all the defects incorporated into YBCO matrix for successful self-field and in-field performance enhancements, intrinsic film defects such as threading dislocations [11,12], misfit dislocations [13], stacking faults [14,15] etc are considered to be the most promising candidates. Moreover, the formation of these potential vortex-pinning sites are closely related to the YBCO thin film initial nucleation [16][17][18] and lattice strain relaxation [19].…”