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  1. 37 Acta Physica Polonica A

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  1. 8 Kołodziejczyk A.

  2. 7 Woch W.

  3. 6 Zalecki R.

  4. 5 Chabanenko V.

  5. 5 Diko P.

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1
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Analysis of Electromagnetic Phenomena in HTc Superconductors

100%
Sosnowski J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
269-274
EN
Unique electromagnetic properties, especially concerning recent observations of the giant remanent magnetic moment in HTc superconductors, require new approach to modeling these phenomena in the oxide ceramics. The present paper is devoted to the analysis of the influence of flux pinning on critical current and flux trapping in HTc superconductors. Modeling of the interaction between nanosized pinning centers and pancake vortices is presented, allowing to determine critical current density, taking into account elasticity forces of the vortices lattice. Ceramic structure of oxide superconductors was considered in trapped flux analysis. The mechanism of trapped flux generation was regarded as strongly related to vortex pinning and critical current phenomena.
2
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Contactless Estimation of Critical Current Density and Its Temperature Dependence Using Magnetic Measurements

100%
Youssef A., Baničová L., Švindrych Z., Janů Z.
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issue 5
1036-1037
EN
We have measured magnetic response of second-generation high temperature superconductor YBa_2Cu_3O_{x} wire and Nb thin film in perpendicular ac field as a function of temperature. We compare experimental complex ac susceptibility to the calculated susceptibility based on the model of Bean's critical-state response in two-dimensional disk in perpendicular field. The harmonic analysis is needed for comparison between the model and the experimental data. We present a method of linking model and experimental susceptibility. Good agreement of experimental susceptibility with model susceptibility of 2D disk allows contactless estimation of critical depinning current density and its temperature dependence.
3
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Critical State Stability and Flux Jumps' Dynamics in a Single Crystal of YBa_{2}Cu_{3}O_{7-δ }

100%
Nabiałek A., Vasiliev S., Chabanenko V., Yao X., Cai Y., Guo L., Kuzovui M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
836-840
EN
We studied the critical state stability and the dynamics of the flux jumps, caused by thermomagnetic avalanches, in a large (3× 3× 1 mm^{3}) single crystal of YBa_{2}Cu_{3}O_{7-δ } superconductor. Flux jumps were observed only at the lowest temperatures attainable in our system (at about 2.2 K) and for the external magnetic field parallel to the c-axis of the investigated crystal. It is shown that thermomagnetic avalanches are initiated in dynamic conditions, for which the magnetic diffusivity is much smaller than the thermal diffusivity. For large single crystals of YBa_{2}Cu_{3}O_{7-δ } immersed directly in liquid helium, the analysis of the critical state stability can be performed in isothermal approximation. However, the conditions of the critical state stability can change dramatically by improving the thermal isolation between the sample and the surrounding coolant. The dynamics of the flux jumps was analyzed in the framework of the model of magnetic diffusion. It is shown that the magnetic diffusivity changes dramatically during the process of the thermomagnetic avalanche. We also studied the influence of the external magnetic field and of the magnetic history on the duration of the flux jumps.
4
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Effect of Nano-SiC Doping on the Superconducting Critical Parameters in MgB_2/Fe Wires and Tapes

100%
Gajda D., Zaleski A., Morawski A., Kario A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
371-374
EN
In this paper the results of critical current measurements for MgB_2 wires and tapes in iron sheath with and without nano-SiC doping are presented. We focus on power-in-tube processing technique, using both in situ and ex situ methods. In situ MgB_2 wires and tapes were fabricated from MgH_2 and B or Mg and B powders. The methods such as hydrostatic extrusion and rolling were used. The samples were annealed under high Ar gas pressure (hot isostatic pressing) at 750°C and 1.0 GPa for 40 min. It was found that critical current of MgB_2/Fe superconducting wire or tape with nano-SiC dopant increased in higher magnetic field values in comparison to pure MgB_2. A significant difference of J_c in tapes made by in situ way from MgH_2 and Mg were found.
5
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The Influence of Magnetic History on the Stability of Critical State and the Dynamics of Flux Jumps in Conventional NbTi Superconductor

100%
Nabiałek A., Vasiliev S., Chabanenko V., Perez-Rodriguez F., Piechota S., Szymczak H.
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issue 2
343-345
EN
We studied the influence of magnetic history on the stability of critical state and the dynamics of flux jumps in conventional NbTi superconductor. We have found that both the stability of critical state and the dynamics of flux jumps are strongly influenced by the magnetic history and by the magnetic field distribution induced within the sample by preceding jumps. This magnetic field distribution can be particularly complex in the region of the hysteresis loop where the external magnetic field changes its sign (region of remagnetization), because of demagnetizing effects. For this reason, the most complex structure of the flux jumps is observed in the third quadrant of magnetization hysteresis loop. Flux jumps observed in the region of remagnetization have different dynamics in comparison to the jumps observed in other regions of the magnetization hysteresis loop. Duration of these jumps is usually significantly longer than others, and their structure is more complex.
6
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The Influence of the Magnetic Field on the Dynamics of the Flux Jumps in the Flux Flow Model

100%
Vasiliev S., Nabiałek A., Rusakov V., Belevtsov L., Chabanenko V., Szymczak H.
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issue 2
340-342
EN
We studied the dynamics of the flux jumps in type II superconductors assuming this dynamics to be determined by magnetic diffusion. The conductivity of the sample during the jump was described by the flux flow conductivity, which depends on local magnetic field. We solved this problem numerically for an infinite slab sample. We assumed that superconducting sample was fully penetrated by the magnetic flux at the beginning and that the local induction of the magnetic field, in the whole sample, was equal to B_0. Then, the external magnetic field was increased by a value of ΔB_{a} and in the external magnetic field of B_0 + ΔB_{a} flux jump occurred. In our simulations we used the parameters characteristic of a conventional NbTi superconductor at 4.2 K. In particular, we studied the influence of the parameter B_0 on the flux jumps' dynamics. We have found that this parameter strongly influences initial stage of the diffusion process. With increasing B_0, the time during which flux front of the avalanche reaches the center of the sample decreases. The results of numerical simulations were compared with experiments.
7
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Pinning Improvement of A15 Applied Superconducting Materials

80%
Glowacki B.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
531-536
EN
Electron-phonon coupling is one of the most common interaction in superconducting materials ranging from Nb₃Sn, MgB₂, iron-based superconductors and high temperature cuprates such as YBa₂Cu₃O_{7-δ} and HgBa₂Ca₂Cu₃O_{8+δ}. However an importance of the electron-phonon coupling constant, λ_{ep}, should not be underestimated for characterisation of the electronic properties of superconducting materials, but it is important that the enhanced flux pinning mechanism can be hold responsible for the applicability of the A15 superconducting materials in emerging hydrogen cryomagnetic technology where temperature of the liquid H₂ can be as low as 14 K.
8
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Critical Current Density and Microstructure of NdBa_2Cu_3O_7 Single Crystal

80%
Diko P., Zmorayová K., Šefčiková M., Antal V., Kováč J., Yao X.
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issue 5
1028-1030
EN
The top-seeded solution growth method was used to grow NdBCOss single crystals in air. The microstructure of the samples has shown that the oxygenation crack structure developed in the single crystals. The intrinsic critical current density was estimated to be at least twice higher than the value of volume critical current density determined from the magnetization measurements.
9
Content available remote

Effects of Magnetic History on AC Loss Minimum in BSCCO-2223 Composite Tape

80%
Maievskyi E., Ciszek M., Trojanowski S.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
527-530
EN
In the paper we report experimental results of AC magnetization losses in a multi-filamentary BSCCO-2223 superconducting composite tape due to coaxial AC and DC magnetic fields subjected perpendicularly to the plane of the tape. Such superposition of magnetic fields usually leads to some reduction of magnetization losses. A distinguished minimum in the AC loss is observed, at a certain DC bias magnetic field and at a certain fixed magnetic field amplitude. It is shown that the minimum of the AC losses very strongly depends on magnetic history of the investigated tape, which is directly related to the magnetic flux trapping within tape's superconducting filaments region. Measurements were carried out with a sinusoidally varying magnetic fields at amplitudes up to 100 mT and a superimposed DC magnetic field up to 50 mT, at frequency range of 21-113 Hz.
10
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Analysis of Resistive Superconducting Transition of a (Tl_{0.6}Pb_{0.24}Bi_{0.16})(Ba_{0.1}Sr_{0.9})_2Ca_2Cu_3O_{y} Film

80%
Woch W., Chrobak M., Kołodziejczyk A.
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issue 2
389-392
EN
In this paper we analyze the resistive transition as a function of both the temperature and the dc applied magnetic field. We use the two models: first, based on the Ambegaokar and Halperin theory that describes the resistive transitions by the modified Bessel function and second, based on the Anderson and Kim theory represented by the exponential formula. The fits of the models to experimental results show that the freezing into superconducting vortex-glass phase takes place at the same temperature that does not practically depend on the applied magnetic field.
11
Publication available in full text mode
Content available

Temperature and Magnetic Field Dependences of Critical Current of Thallium-Based Superconducting Films

80%
Zalecki R., Kołodziejczyk A., Heiml O., Gritzner G.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
669-674
EN
The critical current densities of three superconducting thallium-based films, prepared by screen printing, were measured as a function of temperature and applied magnetic field. The degradation of critical current densities was investigated for two different magnetic field orientations with respect to the sample plane - parallel and perpendicular.
12
Content available remote

Kim-Type Critical State Models and Critical Currents of Thallium Based Superconductors

80%
Woch W., Zalecki R., Kołodziejczyk A., Heiml O., Sudra H., Gritzner G.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
99-106
EN
The two extended formulae in the power form of the Kim critical state model were used to fit the critical currents versus the dc applied magnetic field. Two samples of thallium based superconductors: the (Tl_{0.6}Pb_{0.24}Bi_{0.16})(Sr_{0.9}Ba_{0.1})_2Ca_2Cu_3O_y film on single-crystalline lanthanum aluminate and the bulk (Tl_{0.5}Pb_{0.5})Sr_2(Ca_{1.8}Gd_{0.2})Cu_2O_y were chosen to test the models. The formulae were compared to the percolation model described by the exponential expression. The first model fits the experimental data better for the thallium based film whereas the second approach is better for the thallium based bulk sample.
13
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Investigation Details of Vortex Density in Laser-Written Π-Shaped Channel of YBCO Bridge by Means of I-V Dependences

80%
Steponaviciene L., Sulcas J., Jukna A., Jung G., Plausinaitiene V., Abrutis A., Maneikis A., Gong M., Sobolewski R.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
180-182
EN
A current-self-induced magnetic field H_{j}, such that H_{c1} < H_{j} < H_{c2} at T < T_{c}, penetrates a thin-film, type-II superconductor forming the Abrikosov magnetic vortex-antivortex pairs in the film's areas of weakest superconductivity. Our atomic force microscopy and scanning tunneling microscopy images confirm that in 50 μm wide, 100 μm long and 0.3 μm thick YBa_2Cu_3O_{7 - x} superconducting devices magnetic flux penetrates first into a 5 μm wide, Π-shaped and partially deoxygenated (x ≈ 0.2) channel for easy vortex motion. When the Lorentz force overcomes pinning force in the channel, the flux starts to move and its drift dissipates energy inducing dc voltage. This work reports on the density of coherently moving vortices along the channel vs. temperature in range from 0.93T_{c} to 0.97T_{c}. Our simulations show that the vortex density vs. temperature dependence extracted from I-V measurements of our devices follows the temperature dependence of magnetic field penetration depth and the coherence length of the superconductor.
14
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Current Distribution in Y-Ba-Cu-O Superconducting Microbridges Containing Π-Shaped Channel for Easy Vortex Motion

80%
Sulcas J., Steponaviciene L., Jukna A., Jung G., Plausinaitiene V., Abrutis A., Gong M., Sobolewski R.
Acta Physica Polonica A
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2011
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vol. 119
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issue 2
183-185
EN
A mixed state in dc-biased thin films of II-type superconductors realizes the Abrikosov magnetic vortices/antivortices, which are the result of the current-self magnetic field penetration into the film at temperatures lower than its critical temperature T_{c}. A nucleation of vortices/antivortices at the superconducting film's edges, their motion perpendicular to the direction of biasing current, and the annihilation in the film's center originates from a current dissipation in the superconductor and expresses itself in experiments as a dc voltage. This work reports on the results of simulation of current density in a 50 μm wide, 100 μm long, and 0.3 μm thick YBa_2Cu_3O_{7 - x} microbridges containing Π-shaped 5 μm wide single channel of easy vortex motion fabricated by means of laser-writing technique. Analyzing a two-dimensional-net of resistors and assuming that, due to the Meissner-Ochsenfeld effect, the magnetic flux penetration into superconducting film is nonlinear, we demonstrate that presence of a Π-shaped channel causes a non-homogeneous distribution of current in the microbridge.
15
Publication available in full text mode
Content available

Effect of the In-Plane Epitaxial Mismatch between the Substrate and the Film on the Properties of YBa_2Cu_3O_{7-δ} Films

80%
Abal'osheva I., Cieplak M., Adamus Z., Berkowski M., Domukhovski V., Aleszkiewicz M.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
549-554
EN
We study the effect of the in-plane epitaxial mismatch between the substrate and the film on the crystallographic structure and the transport properties of YBa_2Cu_3O_{7-δ} superconducting films of thicknesses ranging between 600 and 3000Å. The films are grown by pulsed laser deposition on the new type of single-crystalline substrates prepared by Czochralski method, with the chemical formula (SrAl_{0.5}Ta_{0.5}O_3)_{0.7}(CaAl_{0.5}Ta_{0.5}O_3)_{0 .1}(LaAlO_3)_{0.2}. We find that superconducting properties of the samples are excellent, and generally they improve with increasing of the film thickness as a result of improved structural ordering. We also investigate the influence of the film thickness on the behavior of the critical current densities.
16
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On the Current Flow in Superconductors: Universal Trends and Holographic Analysis

80%
Rogatko M., Wysokiński K.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
376-379
EN
The superconducting state can be destroyed by the increase of temperature, magnetic field or current flow beyond their critical values. The critical current I_{c} is of special interest as most of the practical applications of superconductors crucially depend on its limiting value. Recent analysis of experimental data in many families of type I and type II superconductors have discovered an interesting universal relation between critical current density j_{c}, the critical magnetic field H_{c} and the penetration depth λ. For type II superconductors the role of the thermodynamic critical field H_{c} is played by the lower critical field H_{c1} and ratio between the relevant dimension of the system d with respect to the penetration depth matters. Thus the effective dimensionality of the system is important and rules the system behaviour. It turns out that the holographic analogy provides an interesting justification of the above findings. We have calculated the temperature dependence of the critical current in the strongly coupled holographic superconductors with the current flow. It has been found that, independently of the symmetry of the order parameter, the critical current depends on temperature in 2d systems as I_{c} ∝ (T_{c}-T)^{3/2} and agrees with that observed in thin films (d < λ). Similar calculations for 3d systems (d > λ) reveal linear T-dependence I_{c} ∝ (T_{c}-T).
17
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Modeling of Critical Current Density of Bulk High T_c Superconductors

80%
Santosh M.
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vol. 126
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issue 3
808-811
EN
Magnetic field dependence of critical current density (J_{c}) of ErBa_2Cu_3O_y thick film "Er-123" and melt textured GdBa_2Cu_3O_y bulk "Gd-123" at liquid nitrogen temperature is reported. Gd-123 exhibits a usual peak effect at magnetic fields around 2 T, while J_{c} of the Er-123 thick film continuously decreases with increasing field. The model of thermally activated flux motion was adopted to fit the critical current density of both Gd-123 and Er-123 materials. It was found that the critical current density of both types of the high T_{c} materials could be modeled by the model of thermally activated flux motion utilizing a combination of two functions; one increasing and another one decreasing with field.
18
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Critical Current Problems in Neutrons Irradiated HTc Multilayered Superconductors

80%
Sosnowski J.
Acta Physica Polonica A
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2016
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vol. 130
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issue 2
585-587
EN
In the paper there is given an analysis of the critical current problems in irradiated multilayered high temperature oxide superconductors. Critical current for the direction of current flow inside the layers is investigated basing on analysis of the capturing interaction of pancake vortices with nanodefects, created by fast neutrons irradiation. Analysis of the pinning potential barrier formation is presented. From performed calculations of current-voltage characteristics fitted to measurements the inherent pinning centers concentration and their average dimensions were estimated. The case of perpendicular to layers current has been regarded too, taking into account the intrinsic Josephson junctions formation. The influence of nanodefects concentration on the Josephson penetration depth has been considered, whose length determines the Swihart velocity and current-voltage characteristics of junction.
19
Publication available in full text mode
Content available

The Irreversibility Fields of (Tl_{0.5}Pb_{0.5}) (Sr_{0.85}Ba_{0.15})_2Ca_2Cu_3O_z Film on Polished Silver Substrate

80%
Woch W., Zalecki R., Kołodziejczyk A., Deinhofer C., Gritzner G.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
737-743
EN
Superconducting (Tl_{0.5}Pb_{0.5})(Sr_{0.85}Ba_{0.15})_2Ca_2Cu_3O_z film was prepared on a highly polished, untextured silver substrate. A superconducting transition temperature (T_{c,50%}) of 114.7±0.3 K was obtained from the resistance versus temperature measurements for different applied ac currents. The density of the critical current measured by transport method was found to be 11.4×10^3 A/cm^2 at 77 K in the self field. This value is smaller than the value calculated from ac susceptibility data: 53×10^3 A/cm^2 at 77 K. The magnetical broadening of the resistivity transition to the superconducting state was observed. The irreversibility fields of the thallium based film were obtained from magnetoresistive measurements for both parallel to the c-axis and parallel to the $ab$ plane showing the anisotropy according to the magnetic field direction. The irreversibility fields as a function of temperature were successfully fitted by the power law.
20
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Resistance and AC Susceptibility of YBCO 1:2:3 Films on Silver Substrates

80%
Zalecki R., Woch W., Chrobak M., Kołodziejczyk A.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
850-853
EN
The YBa_{2}Cu_{3}O_{δ} films were obtained directly on the polished silver substrates by the sedimentation process. Thickness of these films is of the order of several tens micrometers. The temperature dependences of the resistance and the AC susceptibility of the films were measured and analyzed. The critical temperatures of these specimens vary from 89 K to 91 K and they do not depend on the annealing temperatures. The critical currents were calculated from AC susceptibility measurements using the Bean's model.
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