Harmonic Analysis of the AC Magnetic Response on Directionally Solidified YBaCuO Samples

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1101-1106 ◽  
Author(s):  
M. Polichetti ◽  
S. Pace ◽  
A. Vecchione
Keyword(s):  
Magnetic Field ◽  
Diffusion Processes ◽  
Ac Susceptibility ◽  
Magnetic Response ◽  
Experimental Conditions ◽  
Flux Dynamics ◽  
Flux Flow ◽  
Flux Lines ◽  
Flux Dynamic ◽  
Ac Response

The transport properties and the dynamics of the flux lines have been investigated on YBaCuO melt textured by measuring the AC susceptibility harmonics as function of the temperature, at different frequencies and amplitudes of the AC magnetic field. The interpretation of the behavior of the experimental curves has been done by their comparison with the results obtained by critical state pictures and by simulations of the diffusion processes of the magnetic field which determine the AC response in presence of different regimes of flux dynamics. The temperature dependencies of the third harmonics of the AC susceptibility at different frequencies have been used in particular to determine what is the flux dynamic regime governing the magnetic response of melt textured samples in the different experimental conditions. A good qualitative agreement has been found between the experimental curves and the ones simulated by assuming that dissipation processes are a sequence of independent flux creep and flux flow events within a collective pinning framework.

Theoretical Foucault Images of Superconducting Fluxons

1997 ◽  
Vol 3 (S2) ◽  
pp. 509-510
Author(s):  
M. Beleggia ◽  
G. Pozzi ◽  
K. Harada ◽  
H. Kasai ◽  
T. Matsuda ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Dynamic Behaviour ◽  
Structural Defects ◽  
Experimental Conditions ◽  
Transmitted Beam ◽  
Factors Affecting ◽  
One Dimensional ◽  
Flux Lines ◽  
Main Disadvantage ◽  
Individual Flux

Individual flux lines in superconducting specimens have been recently observed using a 300kV holography electron microscope equipped with a cold field emission gun in the transmission mode by means of the out-of-focus method. In this way it has been possible to observe the dynamic behaviour of fluxons depending upon the variations of the temperature and/or the applied magnetic field or current. The main disadvantage of this method is that correlation with structural defects is troublesome owing to the large defocus distance (of the order of 1 cm for conventional superconductors) necessary for the detection of flux lines.This drawback is not present in the Foucault technique, where the contrast is generated in the focused image by masking part of the transmitted beam by means of an aperture. Therefore, some preliminary calculations have been made recently using one-dimensional models, which allow for a quick and easy simulation of the factors affecting the experimental conditions .

Flux-Flow and Fluctuations in the Microwave Resistivity of YBa2Cu3O7-δ

1999 ◽  
Vol 13 (09n10) ◽  
pp. 1107-1110 ◽  
Author(s):  
E. Silva ◽  
D. Neri ◽  
R. Marcon ◽  
R. Fastampa ◽  
M. Giura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Coherence Length ◽  
Quantitative Description ◽  
Zero Field ◽  
Flux Flow ◽  
Flux Dynamic ◽  
Dissipative Mechanism ◽  
The Magnetic Field ◽  
Microwave Resistivity ◽  
Field Transition

We present measurements of the microwave resistivity at 48 GHz in YBa 2 Cu 3 O 7-δ film, as a function of the temperature and the magnetic field. The magneto-dissipation from 60 K up to a few kelvins below Tc finds a quantitative description in terms of free flux flow. Approaching Tc, the data are not consistent with a dissipative mechanism based solely on flux dynamic. Fluxon viscosity is measured as a function of the temperature, and the in-plane coherence length is estimated. The analysis of the zero-field transition at 48 GHz in terms of anisotropic renormalized fluctuations yields identical estimate.

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.

Optimization of Sample Holder Materials for Sensitive Magnetometry Measurements at Low Temperatures

2004 ◽  
Vol 825 ◽  
Author(s):  
I. Bossi ◽  
N.R. Dilley ◽  
J. R. O'Brien ◽  
S. Spagna
Keyword(s):  
Magnetic Field ◽  
Low Temperatures ◽  
Magnetic Response ◽  
Sample Holder ◽  
Magnetization Measurements ◽  
Temperature Range ◽  
Paramagnetic Impurities ◽  
Fused Quartz

AbstractMagnetization measurements were performed as a function of magnetic field H and temperature T on samples of nine different materials including clear fused quartz, cartridge brass, G-10 glass-reinforced epoxy, acetal homopolymer, glass-filled acetal, phenolic, and other plastics. A small yet distinct amount of ferromagnetic or paramagnetic impurities is observed in all the materials investigated in this study except quartz. In contrast, the magnetic response of quartz is typical of a diamagnet over the temperature range 5 K to 300 K. The volume susceptibility is equal to −4.4×10−7 (cgs) over the whole temperature range.

OBSERVATION OF A LINEAR REGIME IN IMAGINARY χac OF Bi-2223 SUPERCONDUCTOR

1996 ◽  
Vol 10 (03n05) ◽  
pp. 117-123
Author(s):  
T. SOBHA RANI ◽  
G. RAJARAM
Keyword(s):  
Flow Regime ◽  
Imaginary Part ◽  
Ac Susceptibility ◽  
Peak Temperature ◽  
Linear Regime ◽  
Excitation Field ◽  
Flux Flow

Measurements of complex AC susceptibility were performed on Bi-2223/Bi-2212 high Tc superconductor at low excitation field amplitudes. Unusual features attributable to the Bi-2223 phase are observed in the imaginary part of the AC susceptibility, χ″(T), at different excitation field amplitudes, H m . The peak temperature, T p as a function of H m defines a region in (H, T) plane, where χ″ is independent of H m . Various possible interpretations are discussed, including that of a transition to a viscous flux flow regime.

scholarly journals Effect of Aerosil and Oleic Acid on Sedimentation of Magnetorheological Fluid

2019 ◽  
Vol 8 (12S2) ◽  
pp. 79-83
Keyword(s):  
Magnetic Field ◽  
Oleic Acid ◽  
Magnetic Force ◽  
Particle Concentration ◽  
Nano Particles ◽  
Carrier Fluid ◽  
Flux Lines ◽  
Smart Fluids ◽  
Magnetic Flux Lines ◽  
Ferro Magnetic

Magnetorheological Fluids (MRFs) are considered as smart fluids because they control viscosity using external magnetic field. It contains ferro-magnetic powder which are aligned in magnetic flux lines. The magnetic force between particles are controlled by magnetic field intensity. This controllable viscosity makes them acceptable in many mechanical applications, but due to difference in density between suspended particles and carrier fluid sedimentation is bound to occur. This thus creates the need of some additives. In our study, silica Nano particles (commercially known as Aerosil 200) is used as stabilizer and Oleic Acid is used as surfactant and their effect on sedimentation is studied in this article. Some other synthesis parameters like particle concentration, stirring duration and material loading also cause some change in sedimentation rate.

scholarly journals Vortex Flux Dynamics and Harmonic ac Magnetic Response of Ba(Fe0.94 Ni0.06)2As2 Bulk Superconductor

2016 ◽  
Vol 29 (11) ◽  
pp. 2745-2752
Author(s):  
Martin Nikolo ◽  
Vivien S. Zapf ◽  
John Singleton ◽  
Jianyi Jiang ◽  
Jeremy D. Weiss ◽  
...  
Keyword(s):  
Magnetic Response ◽  
Bulk Superconductor ◽  
Flux Dynamics

Critical Currents in NbSe2: Evidence for Surface Pinning

1972 ◽  
Vol 50 (22) ◽  
pp. 2840-2841 ◽  
Author(s):  
J. Kopp ◽  
D. J. Huntley ◽  
R. F. Frindt
Keyword(s):  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Critical Currents ◽  
Flux Flow ◽  
Flux Lines

The variation of critical current density for flux flow with thickness has been measured for crystals of NbSe2 between 10−6 and 0.03 cm thick. The dominant behavior is that [Formula: see text] (thickness)−1 and this is interpreted as evidence for surface pinning predominating over bulk pinning of the flux lines.

MAGNETORESISTANCE IN Bi1.8Pb0.4Sr2Ca2Cu3Oy THICK FILM

1994 ◽  
Vol 08 (26) ◽  
pp. 1661-1665
Author(s):  
WANG ZHIHE ◽  
HAN HANMIN ◽  
HAN GUCHANG ◽  
WANG SHUNXI
Keyword(s):  
Magnetic Field ◽  
Thick Film ◽  
Applied Magnetic Field ◽  
Flow Region ◽  
Irreversibility Line ◽  
Flow Process ◽  
Flux Flow ◽  
Thermally Activated ◽  
Thermally Activated Flux Flow ◽  
Activated Flux

The magnetoresistance curves of Bi(2223) thick film were measured near T c with applied magnetic field parallel and perpendicular to the c axis ranging up to 0.12 T. The results show that thermally activated flux flow region does not exist very close to T c and magnetoresistive transition can be well described by a thermally activated flux flow process below 108.5 K and at lower magnetic field. The relation between applied magnetic field H and temperature T was found to fit with “irreversibility line.”

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