What Can we Learn from Magnetization Experiments on HIGH-TC Superconductors? an Overview

1992 ◽  
Vol 275 ◽  
Author(s):  
J. R. Thompson
Keyword(s):  
High Temperature ◽  
Mixed State ◽  
High Temperature Superconductors ◽  
Critical Currents ◽  
High Tc Superconductors ◽  
High Tc ◽  
Convenient Means ◽  
Current Densities ◽  
Types Of Information ◽  
Insight Into

ABSTRACTMagnetization studies provide a facile and convenient means for investigating high temperature superconductors. This work provides an overview and some specific examples of the types of information attainable through magnetic experiments. Regimes to be discussed include the Meissner region with low applied magnetic fields; the mixed state in higher fields at high temperatures, where equilibrium superconductive properties are accessible; and the magnetically irreversible mixed state at lower temperatures, often with large critical current densities Jc. Generally, the critical currents in the last region are metastable. The associated flux creep phenomenon also provides insight into the materials problem of optimizing the pinning of vortices, in order to maximize Jc.

THE MULTILAYERED HIGH Tc SUPERCONDUCTORS; THE JOSEPHSON MODEL OF WEAK LINKS

1995 ◽  
Vol 09 (21) ◽  
pp. 2811-2820
Author(s):  
VALERY A. CHERENKOV
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
High Temperature Superconductors ◽  
Weak Links ◽  
High Tc Superconductors ◽  
Main Attention ◽  
Multilayered Structures ◽  
High Tc ◽  
Stimulation Of

The multilayered (N-S(D)-N)-types structures have been observed: there are the traditional Niobium low-temperature superconductors and new high-temperature superconductors. The main attention had been directed to the anisotropy, defectively and the stimulation of the superconductivity in the multilayered structures.

Structural and Superconducting Properties of RE1 - 2xPrxCaxSr0.8Ba1.2Cu3O7 - δ (RE = Er and Gd) High Tc Superconductors

2003 ◽  
Vol 17 (13) ◽  
pp. 2609-2622 ◽  
Author(s):  
N. Charoenthai ◽  
P. Winotai ◽  
R. Suryanarayanan ◽  
I. M. Tang
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Transition Temperature ◽  
Size Effect ◽  
High Temperature Superconductors ◽  
Superconducting Properties ◽  
High Tc Superconductors ◽  
High Tc ◽  
Oxygen Annealing ◽  
Ion Size

We report here on the structural and superconducting properties of RE 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ (RE = Er and Gd, 0 ≤ x ≤ 0.2) high temperature superconductors. The transition temperature (Tc) of these compounds decreases when the Pr and Ca concentrations are increased. At constant Pr and Ca concentrations, the Tc of Er 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ superconductor system is higher than that observed for the Gd 1 - 2x Pr x Ca x Sr 0.8 Ba 1.2 Cu 3 O 7 - δ system. For the Gd 0.8 Pr 0.1 Ca 0.1 Sr 0.8 Ba 1.2 Cu 3 O 7 - δ sample, after heating in argon followed by oxygen annealing, the orthorhombicity increases accompanied by 10 K increase in Tc. These results show that though our data indicate an ion-size effect, the Tc suppression rate dTc/dx depends very much on the heat treatment adopted to prepare the samples.

SEPARATED SPIN AND CHARGE DEGREES OF FREEDOM IN HIGH-Tc SUPERCONDUCTORS

2005 ◽  
Vol 19 (01n03) ◽  
pp. 193-197
Author(s):  
L. KRUSIN-ELBAUM ◽  
T. SHIBAUCHI ◽  
G. BLATTER
Keyword(s):  
High Temperature ◽  
Magnetic Fields ◽  
Fermi Surface ◽  
Degrees Of Freedom ◽  
High Temperature Superconductors ◽  
Energy Scale ◽  
High Tc Superconductors ◽  
Critical Fields ◽  
High Tc

Recent Nernst and interlayer transport experiments in Bi 2 Sr 2 CaCu 2 O 8+y (BSCCO) high temperature superconductors report hugely different limiting magnetic fields. We demonstrate that both fields convert to the same pseudogap energy scale T* upon transformation as orbital and Zeeman critical fields, respectively. We suggest a consistent interpretation of this finding based on separation of spin and charge degrees of freedom residing in different regions of a truncated Fermi surface.

scholarly journals An Analysis of Strong Coupling in the High Tc Superconductors

2014 ◽  
Vol 2014 ◽  
pp. 1-7
Author(s):  
J. H. Turner
Keyword(s):  
High Temperature ◽  
Strong Coupling ◽  
High Temperature Superconductors ◽  
High Tc Superconductors ◽  
High Tc ◽  
Cubic Symmetry

A new McMillan formula is assembled for the High Temperature Superconductors that evidences strong coupling in these materials. The McMillan-Hopfield parameter is calculated in each case, in addition to the Bergmann and Rainer enhancement frequency. The cubic symmetry of the CuO layers and the lattice cohesion and oxygen presence are suggested reasons for the effect.

THE SURFACE IMPEDANCE OF HIGH Tc SUPERCONDUCTORS

1989 ◽  
Vol 03 (01) ◽  
pp. 5-13 ◽  
Author(s):  
J. CARINI ◽  
L. DRABECK ◽  
G. GRÜNER
Keyword(s):  
High Temperature ◽  
Temperature Dependence ◽  
Power Law ◽  
Surface Impedance ◽  
Low Temperatures ◽  
Qualitative Agreement ◽  
Surface Resistance ◽  
High Temperature Superconductors ◽  
High Tc Superconductors ◽  
High Tc

Recent experiments on the surface impedance of the high temperature superconductors are summarized. The overall temperature dependence of the penetration depth is in broad qualitative agreement with conventional pairing, but with an anomolous power law behavior observed at low temperatures. The surface resistance is orders of magnitude larger than estimates based on the Mattis-Bardeen theory. One possibility is unconventional pairing, but structural inhomogenities are the most likely explanation for the experimental results.

Magnetic-history-dependent critical currents in granular high-temperature superconductors: Dependence on defect structures and morphology

1989 ◽  
Vol 47 ◽  
pp. 186-187
Author(s):  
Martin P. Maley ◽  
Michael E. McHenry ◽  
Jeffrey O. Willis
Keyword(s):  
High Temperature ◽  
Critical Current ◽  
High Temperature Superconductors ◽  
Critical Currents ◽  
Weak Links ◽  
Small Scale ◽  
Defect Structures ◽  
Flux Lattice ◽  
Superconducting Coherence Length ◽  
Current Densities

Critical current densities, Jc’s, in conventional low temperature superconductors are controlled by defect structures that provide pinning for the magnetic flux lattice. High critical current densities and strong pinning have been observed in single crystals of the new oxide, high temperature superconductors (HTS) and have been ascribed to the presence of twin planes and to stoichiometry variations in the YBCO compound. Neutron irradiation studies have shown that intragranular Jc’s in YBCO can be strongly enhanced by the point defects introduced by irradiation. However, transport Jc’s determined by intergranular current transfer have remained dissappointingly low in bulk ceramic HTS materials. This has suggested a model of strongly superconducting grains separated by “weak links” that behave as Josephson tunnel junctions.The extraordinarily small superconducting coherence length ζo ∼ 10 A° in the HTS make them considerably more sensitive to small scale defects. Grain boundaries that act as pinning centers in conventional superconductors thus become barriers to current flow in the HTS.

Wet Chemical Etching of High TC Superconductors by Ethylenediaminetetraacetic Acid (EDTA)

1989 ◽  
Vol 169 ◽  
Author(s):  
F. K. Shokoohi ◽  
L. M. Schiavone ◽  
C. T. Rogers ◽  
A. Inam ◽  
X. D. Wu ◽  
...  
Keyword(s):  
High Temperature ◽  
Ethylenediaminetetraacetic Acid ◽  
Film Material ◽  
High Tc Superconductors ◽  
Surface Layers ◽  
High Tc ◽  
Zero Resistance ◽  
Current Densities ◽  
Wet Chemical ◽  
Chemical Etchant

AbstractA novel chemical etchant for the high temperature superconducting material YBa2Cu3O7‐x is demonstrated. The etching solution which consists of ethylenediaminetetraacetic acid (EDTA) in water does not degrade the properties of the superconducting films and is suitable for applications with standard photolithography. We have etched 2‐200 μm wide wires which show no degradation of Tc ( within 1 K accuracy of the measurements) and show zero‐resistance temperature ≥90 K. The etchant exhibits a polishing effect by selectively removing the porous and semiconducting surface layers which are formed during high temperature annealing process. The dense bulk of the films are etched at a rate of 1400 Å/min which provides control for fine‐line patterning of thin film material. The critical current densities of the unpatterned films which are polished by reactions with EDTA remain unaffected and are measured to be about 5 x 106 A/cm2.

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