The activation energy U(T,B) in high temperature superconductor

2020 ◽  
Vol 92 (2) ◽  
pp. 20601
Author(s):  
Abdelaziz Labrag ◽  
Mustapha Bghour ◽  
Ahmed Abou El Hassan ◽  
Habiba El Hamidi ◽  
Ahmed Taoufik ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Activation Energy ◽  
Phase Diagram ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Superconductor ◽  
Flux Flow ◽  
Resistivity Measurements ◽  
Vortex Phase ◽  
The Magnetic Field

It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2Cu3O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ (T, B) of the sample under various values of the magnetic field up to 14T in directions B∥ab-plane and B∥c-axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U0 (B) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U (T, B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d ln ρ/dT ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field Hc2 (T), the irreversibility line Hirr (T) and the crossover field HCrossOver (T) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

Magnetoresistance investigation in the mixed state of a high temperature superconductor

2020 ◽  
Author(s):  
Mustapha Bghour ◽  
A. Labrag ◽  
H. El hamidi ◽  
A. Abou El hassan ◽  
A. Taoufik
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Mixed State ◽  
High Temperature Superconductor ◽  
Scaling Law ◽  
Good Alternative ◽  
Magnetic Field Direction ◽  
Flux Flow ◽  
The Magnetic Field ◽  
Good Agreement

In this work we analyze the behavior of magnetoresistance R(H,T) of a high temperature superconductor YBa2Cu3O7-delta thin film optimally doped. Measurements of magnetoresistance were carried out in the mixed state for a magnetic field up to 14T applied in the c-axis then parallel to ab-plane with a DC transport current of 100 and 500nA, 0.1 and 0.3mA perpendicular to the magnetic field direction in both cases. The obtained results show that the magnetoresistance is in a good agreement with the thermally assisted flux creep. However, the magnetoresistance in the flux flow regime cannot be described by the Barden-Stephen model which conjecture another origin of these results. In this sense, the quantum fluctuations of the order be parameter is a good alternative to understanding the shape of the magnetoresistance. The comparison of the magnetoresistance of the two directions shows that Rc(H,T) is larger than Rab(H,T) with anisot-ropy factor gamma=Rc/Rab depending on temperature and magnetic field. The irreversibility line Hirr(T) as well as Hc2(T) are determined and the first one is adjusted with the phenomenological model Hirr(T)=Hirr(0)(1-T/T0)^alpha where Hirr(0), T0 and alpha are parameters obtained from the fit. The investigation of the scaling law allows us to prove that a crossover from 3D to 2D behavior is a feature of our sample which justifies the existence of the decoherence effect.

scholarly journals Heat capacity through the magnetic-field-induced resistive transition in an underdoped high-temperature superconductor

2011 ◽  
Vol 7 (4) ◽  
pp. 332-335 ◽  
Author(s):  
Scott C. Riggs ◽  
O. Vafek ◽  
J. B. Kemper ◽  
J. B. Betts ◽  
A. Migliori ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
High Temperature ◽  
High Temperature Superconductor ◽  
Resistive Transition ◽  
The Magnetic Field

scholarly journals Механизм формирования критического тока высокотемпературных сверхпроводников, содержащих сквозные микроскопические дефекты

2021 ◽  
Vol 63 (1) ◽  
pp. 65
Author(s):  
А.Н. Максимова ◽  
В.А. Кашурников ◽  
А.Н. Мороз ◽  
И.А. Руднев
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Magnetic Flux ◽  
Critical Current ◽  
High Temperature Superconductor ◽  
Physical Mechanism ◽  
Characteristic Size ◽  
Pinning Centers ◽  
The Magnetic Field ◽  
Qualitative Picture

The critical current of a model high-temperature superconductor (HTSC) with defects in the form of through holes (antidots) with a characteristic size greater than or of the order of the penetration depth of the magnetic field is calculated. To do this, the subprocesses equivalent to the trapping of the magnetic flux by the hole and the creation of a vortex at the edge of the hole are introduced into the model of layered HTSC. It is shown that accounting for these subprocesses leads to the appearance of a physical mechanism that allows us to correctly describe the non-monotonic dependence of the critical current on the characteristic size of the antidot, similar to that observed in the experiment. Calculations were performed for a pure superconductor and a superconductor containing nanoscale pinning centers. It is shown that the presence of nanoscale pinning centers along with antipoints does not change the qualitative picture of the influence of the antidot radius on the pinning character of the magnetic flux and the behavior of the critical current in the HTSC.

scholarly journals Levitation and Lateral Stabilization Device Based on a Second-Generation High-Temperature Superconductor

2019 ◽  
Vol 5 (4) ◽  
pp. 115-123
Author(s):  
Yuri F. Antonov
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
High Temperature Superconductor ◽  
Second Generation ◽  
Permanent Magnets ◽  
Transport Current ◽  
Critical Parameters ◽  
Technical Solution ◽  
The Magnetic Field ◽  
Superconducting Levitation

The superconducting levitation device comprises a stationary magnetic rail of permanent magnets and a cryostat on a vehicle with a second-generation high-temperature tape superconductor placed in the cryostat, folded in a stack or wound by a coil on a non-magnetic frame without electrical connection of the ends and the transport current. Cool tape high-temperature superconductor of the second generation, folded in a stack or wound on a non magnetic frame in the form of axisymmetric or track coil, without electric connections of the ends and a transport current, behaves as a massive sample of a superconductor and the Meissner Oxenfeld effect, the magnetic field created by the magnetic rail is displaced from the volume of the superconductor, causing the power of levitation and the vehicle hangs over the track structure. The high critical parameters of the second-generation high-temperature superconductor belt ensure efficient operation of the superconducting levitation device. Aim: To demonstration the technical feasibility and efficiency of creating a levitation unit based on the use of a second-generation high-temperature superconductor and permanent magnets made of rare earth metals. Methods: Calculations of the magnetic field distribution in the combination of a magnetic rail and a massive superconductor, preliminary design of the levitation unit and experimental studies on the model. Results: Experiments on a model of a superconducting levitation device confirmed the efficiency of this technical solution and its effectiveness. Conclusion: an original technical solution is proposed that allows to significantly improve the energy characteristics of the levitation node by using a second-generation high-temperature superconductor operating in a passive mode without a transport current, using the partial Meissner-Oxenfeld effect and the engagement of quantized magnetic flux strands at the pinning centers.

scholarly journals Measurements and Analysis of AC Losses in HTS Windings of Electrical Machine for Different Operation Modes

2021 ◽  
Vol 11 (6) ◽  
pp. 2741
Author(s):  
Sergey Zanegin ◽  
Nikolay Ivanov ◽  
Vasily Zubko ◽  
Konstantin Kovalev ◽  
Ivan Shishov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
High Temperature Superconductor ◽  
High Temperature Superconductors ◽  
Transport Current ◽  
Operating Conditions ◽  
Ac Losses ◽  
Electrical Machine ◽  
2Nd Generation ◽  
Motor Mode

The article is devoted to the study of losses in devices based on high-temperature superconductors of the 2nd generation. The complexity of the devices under study increases from a single rack coil to a winding assembled from several coils, and finally to an electric machine operating in generator mode. This is the way to experimentally study the behavior of 2nd generation high temperature superconductor (2G HTS) carrying a transport current in various conditions: self-field, external DC, and AC magnetic field. Attention is also paid to the losses in the winding during its operation from the inverter, which simulates the operating conditions in the motor mode of a propulsion system.

Magnetic Coupling in La0.7Ca0.3MnO3/YBa2Cu3O7/La0.7Ca0.3MnO3 Trilayers

2009 ◽  
Vol 289-292 ◽  
pp. 303-309
Author(s):  
N.M. Nemes ◽  
C. Visani ◽  
J. Garcia-Barriocanal ◽  
F.Y. Bruno ◽  
Z. Sefrioui ◽  
...  
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Carrier Density ◽  
High Temperature Superconductor ◽  
Hysteresis Loops ◽  
Magnetic Coupling ◽  
Oxygen Depletion ◽  
Free Carrier ◽  
Half Metallic ◽  
Free Carrier Density

We report on the interplay between ferromagnetism and superconductivity in trilayers La0.7Ca0.3MnO3/YBa2Cu3O7/La0.7Ca0.3MnO3 made of half metallic manganite and high temperature superconductor cuprate. Samples with a fully oxygenated cuprate show a magnetic field interval where the magnetizations of the manganite are aligned antiparallel. A considerable magnetoresistance accompanies the switching between magnetization configurations (parallel vs. antiparallel) of the manganite moments. Suppression of the free carrier density of the cuprate which occurs upon oxygen depletion, results in deep modifications in the shape of the normal state hysteresis loops indicating that there may be a magnetic coupling mediated by free carrier density of the cuprate. This result outlines the importance of quasiparticle transmission in the interplay between ferromagnetism and superconductivity in this kind of samples.

Pressure effect on the magnetic field-temperature phase diagram of

2008 ◽  
Vol 403 (5-9) ◽  
pp. 749-751 ◽  
Author(s):  
Y.J. Jo ◽  
L. Balicas ◽  
C. Capan ◽  
K. Behnia ◽  
P. Lejay ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Diagram ◽  
Pressure Effect ◽  
Temperature Phase ◽  
Field Temperature ◽  
The Magnetic Field ◽  
Temperature Phase Diagram
Sign in / Sign up

Export Citation Format

Share Document