Ac Susceptibility Studies of the High Tc Superconductors: Dissipative Effects in La2.xSrxCuO4-Y and YBa2Cu3O7-Y Systems

1989 ◽  
Vol 169 ◽  
Author(s):  
Xinsheng Ling ◽  
M. E. Filipkowski ◽  
E. K. Heller ◽  
J. I. Budnick
Keyword(s):  
Grain Boundaries ◽  
Order Parameter ◽  
Ac Susceptibility ◽  
Similar Process ◽  
Charge Carrier Density ◽  
High Tc Superconductors ◽  
High Tc ◽  
Spatial Fluctuation ◽  
Dissipative Effects ◽  
Ceramic Samples

AbstractWe have studied the variation of dissipative effects with doping in the high Tc superconductors La2-xSrxCuO4-y and YBa2Cu3O7-y by studying the lossy component of ac susceptibility as a function of temperature. We find relatively strong excess losses at low temperature in both systems, which indicate stronger flux creep at grain boundaries, in lower level doped ceramic samples produced by a similar process. This effect is more significant in the La2-xSrxCuO4-y (214) system than in the YBa2Cu3O7-y(123) system. We suggest that the microscopic mechanisms of weakening of the order parameter in the grain boundaries may be different in the two systems. In the 214 system, as the charge carrier density in the CuO2 planes is reduced, the spatial fluctuation of the order parameter in the CuO2 planes is enhanced. In the 123 system, the initial removal of O from the sample, which weakens the coupling between planes and increases the spatial fluctuation of the order parameter between CuO2 planes. The grain boundaries are degraded in both systems. The degradation in the 214 samples is more significant than in the 123 samples.

Field induced transition of the AC susceptibility in high-Tc superconductors

1996 ◽  
Vol 46 (S3) ◽  
pp. 1589-1590 ◽  
Author(s):  
Oliver Waldmann ◽  
Gerald Lichtschlag ◽  
Florian Steinmeyer ◽  
Andrei Talalaevskii ◽  
Paul Müller
Keyword(s):  
Ac Susceptibility ◽  
High Tc Superconductors ◽  
High Tc

Doping induced enhancement of the critical currents of grain boundaries in high-Tc superconductors

2000 ◽  
Vol 341-348 ◽  
pp. 1393-1396 ◽  
Author(s):  
J. Mannhart ◽  
H. Bielefeldt ◽  
B. Goetz ◽  
H. Hilgenkamp ◽  
A. Schmehl ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Critical Currents ◽  
High Tc Superconductors ◽  
High Tc

On the Origin of Zero-Bias Conductance Peak in High-Tc Superconductors

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3027-3030
Author(s):  
Alexander B. Nazarenko ◽  
Ernst A. Pashitskii ◽  
Alexander E. Pashitskii
Keyword(s):  
Elastic Scattering ◽  
Order Parameter ◽  
Magnetic Impurities ◽  
High Tc Superconductors ◽  
Zero Bias ◽  
High Tc ◽  
Conductance Peak ◽  
Wave Symmetry ◽  
Zero Bias Conductance ◽  
D Wave

We show that the zero-bias conductance peak observed in tunnel and point junctions of cuprates can be a consequence of "unitary" elastic scattering of the carriers by non-magnetic impurities in the vicinity of the junction interface and d-wave symmetry of the order parameter.

INFLUENCE OF GRAIN BOUNDARIES ON THE TRANSPORT CRITICAL CURRENT DENSITY OF HIGH Tc SUPERCONDUCTORS

1991 ◽  
Vol 05 (14n15) ◽  
pp. 993-999 ◽  
Author(s):  
HUIMIN SHAO ◽  
MU LU ◽  
TIANCHANG LU ◽  
XICHUN JIN ◽  
LINJIANG SHEN ◽  
...  
Keyword(s):  
Critical Current Density ◽  
Grain Boundaries ◽  
Critical Current ◽  
Current Density ◽  
Transport Critical Current Density ◽  
High Tc Superconductors ◽  
High Tc ◽  
Preparation Conditions ◽  
Percolation Path ◽  
Superconducting Current

This paper describes our efforts to improve the preparation conditions of YBCO samples and increase their density by doping with Sn, F, or Ag and our analysis of the influence of different grain boundaries on superconducting current. We come to the conclusion that, as the grain boundaries have an insulation layer between them forming Josephson junctions and the metalled grain boundaries form proximity junctions which are kind of weak couplings for superconductors, the current-carrying capacity of samples having such grain boundaries cannot be expected to greatly increase. Only by increasing the density of samples and purifying the grain boundaries can a better percolation path for supercurrent be created, thereby considerably increasing the critical current density.

Pair Symmetry and Degree of Gap Depression at S-I Interfaces in HTS Josephson Junctions

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1301-1306
Author(s):  
G. A. Ummarino ◽  
R. S. Gonnelli ◽  
C. Bravi ◽  
Masumi Inoue
Keyword(s):  
Josephson Junctions ◽  
Order Parameter ◽  
Reference Value ◽  
High Tc Superconductors ◽  
S Wave ◽  
General Reference ◽  
High Tc ◽  
Wave Symmetry ◽  
Set Up ◽  
D Wave

A new possible indirect way of testing pair symmetry in high-Tc superconductors has been set up. The degree of intrinsic gap depression at Superconductor-Insulator [S-I] interfaces required to match Ic(T)Rn(T) data in HTS Josephson junctions depends on the pair symmetry of the material itself, so that an higher fraction of d-wave symmetry for the order parameter requires less gap depression, while an higher fraction of s-wave corresponds to a larger degree of gap depression. In order to obtain a general reference value for the intrinsic amount of gap depression at S-I interfaces the de Gennes condition has been used, and resulting reduced Ic(T)Rn(T) data have been calculated in the framework of a mixed (s+id)-wave pair symmetry for the depressed order parameter ranging from pure s to pure d-wave. This model has been tentatively applied to two junctions' made of very different HTSs: YBCO and BKBO, yielding a result of almost pure d-wave for YBCO and of pure s-wave for BKBO.

AC susceptibility and local intergranular magnetic field in high-Tc superconductors

1993 ◽  
Vol 214 (1-2) ◽  
pp. 111-118 ◽  
Author(s):  
P. Levy ◽  
H. Ferrari ◽  
V. Bekeris ◽  
C. Acha
Keyword(s):  
Magnetic Field ◽  
Ac Susceptibility ◽  
High Tc Superconductors ◽  
High Tc

Degradation of high-Tc superconductors by annealing in dry and moist atmospheres

1990 ◽  
Vol 5 (9) ◽  
pp. 1855-1859 ◽  
Author(s):  
W-K. Lee ◽  
A. S. Nowick
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Meissner Effect ◽  
Treatment Temperature ◽  
The Other ◽  
Boundary Phase ◽  
Maximum Effect ◽  
High Tc Superconductors ◽  
High Tc ◽  
Anneal Temperature

A study is made of the effects of annealing both La2−xSrxCuO4 (for x = 0, 0.1, and 0.15) and YBa2Cu3O7 in wet and dry O2 atmospheres at various temperatures between 200 and 930 °C. In the case of La2−xSrxSrCuO4, substantial degradation of resistive properties occurs during annealing in moist O2, the degradation being highest at 200 °C and decreasing as the treatment temperature increases. Since the Meissner effect remains unaffected, it is concluded that degradation is due to the formation of a hydroxide species at grain boundaries, which decomposes as the anneal temperature is increased to 930 °C. In the case of YBa2Cu3O7, on the other hand, moisture does not produce degradation for anneals at 200 °C and above, but severe degradation of resistive behavior does occur for dry O2 anneals, with a maximum effect at 500 °C. It is found that this effect results from a contaminant gas, possibly CO2, absorbed by the furnace when it is open to air. Again, the degradation is due to formation of a grain-boundary phase which decomposes by annealing at 930 °C.

Raman scattering line shapes as a probe of the order parameter symmetry in high — Tc superconductors

1994 ◽  
Vol 235-240 ◽  
pp. 1077-1078
Author(s):  
K.P. Jain ◽  
A.K. Shukla ◽  
R. Ramakumar ◽  
Ratnamala Chatterji ◽  
M. Fukutomi
Keyword(s):  
Raman Scattering ◽  
Order Parameter ◽  
High Tc Superconductors ◽  
High Tc ◽  
Line Shapes ◽  
Parameter Symmetry ◽  
Order Parameter Symmetry
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