Critical currents and vortex pinning in U/n treated Bi2223/Ag tapes

2004 ◽  
Vol 408-410 ◽  
pp. 524-525
Author(s):  
I. Kušević ◽  
E. Babić ◽  
D. Marinaro ◽  
S.X. Dou ◽  
R. Weinstein
Keyword(s):  
Critical Currents ◽  
Vortex Pinning

VORTEX PINNING AND CRITICAL CURRENTS IN JOSEPHSON JUNCTION ARRAYS WITH DEFECTS

1996 ◽  
Vol 10 (10) ◽  
pp. 451-458 ◽  
Author(s):  
SUJAY DATTA ◽  
SHANTILAL DAS ◽  
DESHDEEP SAHDEV ◽  
RAVI MEHROTRA
Keyword(s):  
Size Effects ◽  
Finite Size ◽  
Critical Currents ◽  
Vortex Pinning ◽  
Resistive State ◽  
Finite Size Effects ◽  
Josephson Junction Arrays ◽  
Pinning Potential ◽  
State Regime ◽  
Junction Arrays

We develop an algorithm based on the Fast Cosine Transform to study two-dimensional arrays of Josephson junctions containing defects. We apply it to arrays as large as 128 × 256 and study vortex pinning, the transition from the superconducting to the resistive state, and various finite size effects. We find that the pinning potential for vortices is highly anisotropic in rectangular arrays due to boundaries and finite size effects. As a result we observe pinned vortices in arrays much smaller than expected so far. The energy of an array changes discontinuously at transitions from one vortex sector to another in the steady-state regime.

scholarly journals Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe2(As1−xPx)2

2013 ◽  
Vol 87 (9) ◽  
Author(s):  
S. Demirdiş ◽  
Y. Fasano ◽  
S. Kasahara ◽  
T. Terashima ◽  
T. Shibauchi ◽  
...  
Keyword(s):  
Critical Currents ◽  
Vortex Pinning ◽  
Pinning Energies

All-chemical high-Jc YBa2Cu3O7 multilayers with SrTiO3 as cap layer

2006 ◽  
Vol 21 (5) ◽  
pp. 1106-1116 ◽  
Author(s):  
A. Pomar ◽  
M. Coll ◽  
A. Cavallaro ◽  
J. Gàzquez ◽  
J.C. González ◽  
...  
Keyword(s):  
Ybco Film ◽  
Growth Conditions ◽  
Critical Currents ◽  
Layer Growth ◽  
Vortex Pinning ◽  
Buffer Layers ◽  
Superconducting Thin Films ◽  
Chemical Solution ◽  
Superconducting Properties ◽  
Chemical Methods

We grew high-quality epitaxial YBa2Cu3O7 (YBCO) superconducting thin films by the trifluoroacetate route on top of chemical solution deposited SrTiO3 buffer layers. We show that high lattice mismatches can be accommodated in heterostructures grown by chemical methods. Clean interfaces were observed between the different layers. The influence of the buffer layer growth conditions on the final superconducting properties was studied in depth. We have proved that the main parameter affecting the YBCO critical currents is the SrTiO3 surface roughness, which promotes the nucleation of a/b axis grains and, as a consequence, the porosity of the YBCO film. On the other hand, an improved dependence of the critical current with perpendicular applied magnetic field was observed. This suggests a strengthened vortex pinning due to a higher density of a/b axis oriented grains.

scholarly journals Targeted evolution of pinning landscapes for large superconducting critical currents

2019 ◽  
Vol 116 (21) ◽  
pp. 10291-10296 ◽  
Author(s):  
Ivan A. Sadovskyy ◽  
Alexei E. Koshelev ◽  
Wai-Kwong Kwok ◽  
Ulrich Welp ◽  
Andreas Glatz
Keyword(s):  
Critical Current ◽  
Optimization Problems ◽  
A Priori ◽  
Biological Evolution ◽  
Critical Currents ◽  
Vortex Pinning ◽  
Material Defects ◽  
Future Design ◽  
Material Optimization ◽  
Particle Irradiation

The ability of type II superconductors to carry large amounts of current at high magnetic fields is a key requirement for future design innovations in high-field magnets for accelerators and compact fusion reactors, and largely depends on the vortex pinning landscape comprised of material defects. The complex interaction of vortices with defects that can be grown chemically, e.g., self-assembled nanoparticles and nanorods, or introduced by postsynthesis particle irradiation precludes a priori prediction of the critical current and can result in highly nontrivial effects on the critical current. Here, we borrow concepts from biological evolution to create a vortex pinning genome based on a genetic algorithm, naturally evolving the pinning landscape to accommodate vortex pinning and determine the best possible configuration of inclusions for two different scenarios: a natural evolution process initiating from a pristine system and one starting with preexisting defects to demonstrate the potential for a postprocessing approach to enhance critical currents. Furthermore, the presented approach is even more general and can be adapted to address various other targeted material optimization problems.

Aspects of microanalysis in a transmission electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 510-511
Author(s):  
R. Sinclair ◽  
B.E. Jacobson
Keyword(s):  
Grain Size ◽  
Electron Beam ◽  
Electron Microscope ◽  
Chemical Analysis ◽  
Transmission Electron Microscope ◽  
Vapor Deposition ◽  
Critical Currents ◽  
X Ray ◽  
Fine Grain ◽  
Transmission Electron

INTRODUCTIONThe prospect of performing chemical analysis of thin specimens at any desired level of resolution is particularly appealing to the materials scientist. Commercial TEM-based systems are now available which virtually provide this capability. The purpose of this contribution is to illustrate its application to problems which would have been intractable until recently, pointing out some current limitations.X-RAY ANALYSISIn an attempt to fabricate superconducting materials with high critical currents and temperature, thin Nb3Sn films have been prepared by electron beam vapor deposition [1]. Fine-grain size material is desirable which may be achieved by codeposition with small amounts of Al2O3 . Figure 1 shows the STEM microstructure, with large (∽ 200 Å dia) voids present at the grain boundaries. Higher quality TEM micrographs (e.g. fig. 2) reveal the presence of small voids within the grains which are absent in pure Nb3Sn prepared under identical conditions. The X-ray spectrum from large (∽ lμ dia) or small (∽100 Ǻ dia) areas within the grains indicates only small amounts of A1 (fig.3).

Epitaxy and texture analysis of Bi-Sr-Ca-Cu-O thin films on (100) MgO using Transmission Electron Microscopy

1990 ◽  
Vol 48 (4) ◽  
pp. 68-69
Author(s):  
J. T. Sizemore ◽  
D. G. Schlom ◽  
Z. J. Chen ◽  
J. N. Eckstein ◽  
I. Bozovic ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Critical Currents ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Cell Axis ◽  
Transmission Electron ◽  
Synthesis Procedure

Investigators observe large critical currents for superconducting thin films deposited epitaxially on single crystal substrates. The orientation of these films is often characterized by specifying the unit cell axis that is perpendicular to the substrate. This omits specifying the orientation of the other unit cell axes and grain boundary angles between grains of the thin film. Misorientation between grains of YBa2Cu3O7−δ decreases the critical current, even in those films that are c axis oriented. We presume that these results are similar for bismuth based superconductors and report the epitaxial orientations and textures observed in such films.Thin films of nominally Bi2Sr2CaCu2Ox were deposited on MgO using molecular beam epitaxy (MBE). These films were in situ grown (during growth oxygen was incorporated and the films were not oxygen post-annealed) and shuttering was used to encourage c axis growth. Other papers report the details of the synthesis procedure. The films were characterized using x-ray diffraction (XRD) and transmission electron microscopy (TEM).

Microstructure of YBa2Cu3O7-x thin films deposited by dc sputtering

1989 ◽  
Vol 47 ◽  
pp. 172-173
Author(s):  
O. Eibl ◽  
G. Gieres ◽  
H. Behner
Keyword(s):  
Thin Films ◽  
Cross Sections ◽  
Intermediate Layer ◽  
Amorphous State ◽  
Critical Currents ◽  
Dc Sputtering ◽  
State Process ◽  
Diffraction Patterns ◽  
Film Substrate ◽  
Substrate Temperatures

The microstructure of high-Tc YBa2Cu3O7-X thin films deposited by DC-sputtering on SrTiO3 substrates was analysed by TEM. Films were either (i) deposited in the amorphous state at substrate temperatures < 450°C and crystallised by a heat treatment at 900°C (process 1) or (ii) deposited at around 740°C in the crystalline state (process 2). Cross sections were prepared for TEM analyses and are especially useful for studying film substrate interdiffusion (fig.1). Films deposited in process 1 were polycristalline and the grain size was approximately 200 nm. Films were porous and the size of voids was approximately 100 nm. Between the SrTiO3 substrate and the YBa2Cu3Ox film a densly grown crystalline intermediate layer approximately 150 nm thick covered the SrTiO3 substrate. EDX microanalyses showed that the layer consisted of Sr, Ba and Ti, however, did not contain Y and Cu. Crystallites of the layer were carefully tilted in the microscope and diffraction patterns were obtained in five different poles for every crystallite. These patterns were consistent with the phase (Ba1-XSrx)2TiO4. The intermediate layer was most likely formed during the annealing at 900°C. Its formation can be understood as a diffusion of Ba from the amorphously deposited film into the substrate and diffusion of Sr from the substrate into the film. Between the intermediate layer and the surface of the film the film consisted of YBa2Cu3O7-x grains. Films prepared in process 1 had Tc(R=0) close to 90 K, however, critical currents were as low as jc = 104A/cm2 at 77 K.

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