scholarly journals Температурные зависимости критических параметров неоднородных сверхпроводящих пленок

2021 ◽  
Vol 63 (8) ◽  
pp. 1035
Author(s):  
П.И. Безотосный ◽  
К.А. Дмитриева
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
External Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Superconducting Films ◽  
Critical Magnetic Field ◽  
Temperature Dependences ◽  
Comparison Of The Results

The results of calculating the temperature dependences of the critical current density and critical magnetic field of thin inhomogeneous superconducting films are presented. Comparison of the results obtained for inhomogeneous films with the results of calculations for homogeneous ones showed that in both cases, the decrease in the critical magnetic field occurs according to the root law, and the critical current density changes according to a power law with a degree of 3/2 when approaching the critical temperature. Quantitatively, the critical current density for inhomogeneous films in the absence of an external magnetic field is lower than for homogeneous ones. In turn, the critical magnetic field of inhomogeneous films is much larger than the critical field of homogeneous films.

scholarly journals Theoretical Derivation of Critical Current Density and Critical Magnetic Field Considering Many-Body Interactions of Magnetic Flux Quanta

2021 ◽  
Author(s):  
Shinichi Ishiguri
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
Magnetic Flux ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Critical Magnetic Field ◽  
Many Body ◽  
Magnetic Flux Quantum ◽  
Many Body Interactions

To clarify the relationships among critical temperature, critical magnetic field, and critical current density, this paper describes many-body interactions of quantum magnetic fluxes (i.e., vortices) and calculates pinning-related critical current density. All calculations are analytically derived, without numerical or fitting methods. After calculating a magnetic flux quantum mass, we theoretically obtain the critical temperature in a many-body interaction scenario (which can be handled by our established method). We also derive the critical magnetic field and inherent critical current density at each critical temperature. Finally, we determine the pinning-related critical current density with self-fields. The relationships between the critical magnetic field and critical temperature, inherent critical current density and critical temperature, and pinning critical current density and self-magnetic field were consistent with experimental observations. From the critical current density and critical magnetic field, we clarified the magnetic field transition. It appears that a magnetic flux quantum collapses when the lattice of magnetic flux quanta melts. Our results, combined with our previously published papers, provide a comprehensive understanding of the transition points in high-Tc cuprates.

Superconducting Tape-Shaped Wire by Y1Ba2cu3o7-δ with Jc ≈ 2000 A/cm2

1987 ◽  
Vol 99 ◽  
Author(s):  
S. Matsuda ◽  
M. Okada ◽  
T. Morimoto ◽  
T. Matsumoto ◽  
K. Ihara
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Superconducting Tape ◽  
Rolling Method ◽  
The Wire

ABSTRACTA tape-shaped wire with Y1 Ba2Cu3, O7-δ, core and Ag sheath was fabricated by a drawing-rolling method. The critical current density of the wire with 0.1 mm thickness and 6 mm width was in 2 the range of 2000 A/cm at 77 K in the absence of external magnetic field. Presence of 20 m Tesla magnetic field reduced the J value to 1/100.

Microwave Synthesis of Nano SiC Doping Mg(B1-2x(SiC)x)2 Superconductor and Superconductivity

2012 ◽  
Vol 512-515 ◽  
pp. 11-16
Author(s):  
Yuan Dong Peng ◽  
Qing Lin Xia ◽  
Qian Ming Huang ◽  
Li Ya Li ◽  
Hong Zhong Wang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Direct Synthesis ◽  
Xrd Analysis ◽  
Magnetization Measurement ◽  
Superconducting Transition ◽  
Short Time

Superconductor samples Mg(B1-2x(SiC)x)2 (x=0, 5%, 10%) are synthesized from nano SiC, Mg and amorphous boron powders by microwave direct synthesis in a short time. Powder X-ray diffraction (XRD) analysis indicates that the phases of the synthesis sample are MgB2 (major phase) and a small amount of MgO and Mg2Si. The main peaks of MgB2, (100), (101), (002) and (110) are shift to the higher diffraction angle position and the width of half height of the diffraction plane is broaden for the SiC doping Mg(B1-2x(SiC)x)2, which show that the B positions of MgB2 are partly substituted and the grains of MgB2 are fine. Scanning electron microscope (SEM) observation shows that the MgB2 grain size is very small and the sample is tightness (compact). The onset superconducting transition temperature of the Mg(B1-2x(SiC)x)2 (x=0, 5%, 10%) samples measured by magnetization measurement are about 37.6 K, 37.0 K, 36.8 K respectively. The critical current density Jc are calculated according to the Bean model from the magnetization hysteresis loop of the slab Mg(B1-2x(SiC)x)2 (x=0, 5%, 10%) samples. The critical current density Jc of nano SiC doping Mg(B1-2x(SiC)x)2 samples are greatly enhanced. In higher external magnetic field, the Jc of 10% SiC doped sample is the highest; in lower external magnetic field, the Jc of 5% SiC doped sample is the highest; while in the whole external magnetic field, the Jc of undoped sample is the lowest.

Critical Current Characteristics and Flux Pinning in Fe-Based Pnictide Superconductor

2013 ◽  
Vol 750 ◽  
pp. 288-292
Author(s):  
Bao Rong Ni ◽  
Edmund S. Otabe ◽  
Masaru Kiuchi ◽  
Yan Wei Ma
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Flux Pinning ◽  
Ac Susceptibility ◽  
Pinning Mechanism ◽  
Temperature Dependences ◽  
Current Densities ◽  
Current Characteristics

The superconducting Ba1-xKxFe2As2(x = 0.4) single crystals were prepared by the so-called FeAs self-flux method. The critical temperature by ac susceptibility measurement was estimated to be about 36 K. The magnetic field and temperature dependences of critical current densities were investigated by an ac inductive measurement (Campbell’s method). Unlike the phenomenon of co-existence of the global and local critical current densities observed in many polycrystalline Fe-based superconducting pnictides, it was found that only a uniform critical current density (Jc) flows through the whole sample. The value of Jcat 20 K and 1 T was about 5×108A/m2, which is much smaller than the local critical current density observed in polycrystalline samples. This result implies that a dissimilarity of flux pinning mechanism exists between these two kinds of materials. The force-displacement characteristic of fluxoids in sample was investigated. The Labusch parameter was found to increase monotonously with increasing magnetic field, while the interaction distance was proportional to the fluxoid spacing. These results are consistent with the prediction based on a simple flux pinning mechanism.

Critical Current Density and Flux Pinning Properties in Superconducting MgB2 with and without SiC Doping

2013 ◽  
Vol 750 ◽  
pp. 293-297
Author(s):  
Wen Xu Sun ◽  
Bao Rong Ni ◽  
Akiyoshi Matsumoto ◽  
Hiroaki Kumakura
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
High Magnetic Field ◽  
Current Density ◽  
Flux Pinning ◽  
Critical Magnetic Field ◽  
Pinning Mechanism ◽  
Pinning Potential ◽  
Force Displacement

It is well known that SiC doping in superconducting MgB2 improves the upper critical magnetic field (Bc2) and the critical current density (Jc) under high magnetic field. However, the relationship between SiC doping and the flux pinning mechanism has not been clarified. In this study, several MgB2 samples with and without SiC doping were prepared by the conventional in situ powder-in-tube method. The critical current densities and the force-displacement characteristics of fluxoids in samples were investigated by an ac inductive measurement (Campbell’s method). The Labusch parameter (αL) and the interaction distance (di) were estimated from the obtained force-displacement profile. It was found that SiC doping enhances the values of αL, but does not change the characteristics of the magnetic field dependence of αL apparently. Namely, αL vs. B3/2 characteristics in the pure samples and SiC doped samples are almost the same. Such a result of αL properties implies that the pinning mechanism in the SiC doped samples could be consistent with the conventional pinning theory. On the other hand, di, which is considered to be proportional to the size of pinning potential, decreases rapidly with increasing magnetic field, especially in the pure samples. For high magnetic field region, the variations of di were deduced to be caused by flux creep. The depth of pinning potential, U0, was estimated by using the values of αL and di. The values of U0 give evidence of that SiC doping can prevent the flux bundles moving to another pinning center under high magnetic field.

STUDY OF THE TEXTURING IN BSCCO-AG TAPES THROUGH MAGNETIC MEASUREMENTS

2000 ◽  
Vol 14 (25n27) ◽  
pp. 3159-3164
Author(s):  
C. FERDEGHINI ◽  
M. R. CIMBERLE ◽  
G. GRASSO ◽  
P. GUASCONI ◽  
A. MALAGOLI ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Magnetic Measurements ◽  
Texture Evolution ◽  
Rolling Direction ◽  
Longitudinal Direction ◽  
Magnetic Method ◽  
Superconducting Compounds

We have developed a method that allows, by a simple set of magnetic measurements, to study the texturing of the grains inside a BSCCO-Ag tape. Because the texture is anisotropic we define the angle ϑ L that identifies the mean grain misalignment angle with respect to the tape surface in longitudinal direction (i.e. rolling direction) and the angle ϑ T in transverse direction. The technique is based on the assumption that, because of the very high anisotropy of the critical current density in BSCCO superconducting compounds, the magnetic moment is essentially generated by the current circulating in the a-b planes of the BSCCO grains. The different magnetisation cycles, measured when the orientation of the magnetic field with respect to the tape surface is changed, depend only on the grain orientation inside the tape, which determines the effective magnetic field component normal to the a-b planes of the grains. Here we present the texture evolution of the BSCCO grains inside silver sheated multifilamentary tape starting from the initial steps of the mechanical deformation up to the final heating stage. The results obtained from the magnetic method are compared with those obtained with other methods, i.e. X-ray diffraction and critical current density anisotropy. Also results obtained on samples prepared in different way will be presented.

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