Search results

1

Superconductivity and Magnetism of Dy_{1-x}Y_xRh_4B_4: Candidate for Spin-Triplet Cooper Pairing

100%

Dmitriev V., Zaleski A., Khlybov E., Rybaltchenko L., Khristenko E., Ishchenko L., Terekhov A.

Acta Physica Polonica A

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2008

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vol. 114

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issue 1

83-90

EN

In this work for the first time we give the evidence that compound Dy_{1-x}Y_x Rh_4B_4 with the tetragonal body-centered crystal structure LuRu_4B_4 is the ferrimagnetic at temperatures T_{Cur}<40 K, ferrimagnetic superconductor at T_C <10 K and antiferromagnetic superconductor at T_N <3 K. No reentrant behavior was found down to T = 0.32 K. For the first time by means of a method of microcontact spectroscopy of the Andreev reflection in point contact Ag-Dy_{0.8}Y_{0.2}Rh_4B_4 the value and temperature and field dependences of superconducting gap parameter∆(T, H) in Dy_{0.8}Y_{0.2}Rh_4B_4 were determined. The value of the ratio 2∆(0)/kT_C is about 4. Some unusual features of∆(T, H) dependences were observed, which give the evidence that the Dy_{1-x}Y_xRh_4B_4 is a candidate for spin-triplet Cooper pairing of charges with the parallel spins.

2

Andreev Reflection Study of the Superconductor Mo_3Sb_7

100%

Dmitriev V., Rybaltchenko L., Khristenko E., Ishchenko L., Bukowski Z., Troć R.

Acta Physica Polonica A

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2008

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vol. 114

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issue 1

263-267

EN

The point-contact Andreev-reflection measurements on the new paramagnetic superconductor Mo_3Sb_7 were carried out. It was found that the order parameter ∆ is strongly anisotropic varying over a very wide range depending on the contact orientation when the maximum ∆_{max} exceeds at least 40 times the minimum ∆_{min} in spite of the invariable T_c that cannot be typical of conventional superconductors. For these and other reasons we suggest that Mo_3Sb_7 is not a trivial BCS (s-wave) superconductor but rather has some unconventional pairing symmetry.

3

On Superconducting Transition Temperature in Amorphous Alloys of Simple Metals

63%

Krasny Y., Kovalenko N., Krawczyk J., Gurnitskaja E.

Acta Physica Polonica A

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1999

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vol. 96

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issue 3-4

457-466

EN

The Eliashberg equations are generalised to describe amorphous binary alloys. Equations for the electron-phonon coupling constant λ are obtained. An additional term caused by topological disorder appears in the expression for λ-constant. The features of amorphous state and their influence on λ-constant and superconducting transition temperature are emphasised and analysed. Theoretical results are illustrated by numerical calculations performed for some binary amorphous alloys of simple metals.

4

The Influence of Magnetic History on the Stability of Critical State and the Dynamics of Flux Jumps in Conventional NbTi Superconductor

63%

Nabiałek A., Vasiliev S., Chabanenko V., Perez-Rodriguez F., Piechota S., Szymczak H.

Acta Physica Polonica A

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2010

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vol. 118

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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.

5

Effect of Nano-SiC Doping on the Superconducting Critical Parameters in MgB_2/Fe Wires and Tapes

63%

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.

6

The Influence of the Magnetic Field on the Dynamics of the Flux Jumps in the Flux Flow Model

63%

Vasiliev S., Nabiałek A., Rusakov V., Belevtsov L., Chabanenko V., Szymczak H.

Acta Physica Polonica A

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2010

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vol. 118

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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

AC Microcalorimetry of Superconducting MgCNi_3 Single Crystals

63%

Kačmarčík J., Pribulová Z., Samuely P., Marcenat C., Klein T., Jang D., Lee H., Lee H., Lee S.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

363-366

EN

The low-temperature specific heat of single-crystal samples of superconducting MgCNi_3 with typical dimensions 200 μm were measured for the first time. A computer controlled ac microcalorimeter using an optical fiber and an infrared light-emitting diode as the heat source was used down to 2 K at magnetic fields up to 8 T. The specific heat data suggest a moderate coupling in MgCNi_3.

8

Oscillating Dynamics and Trajectory of the Single Vortex Line

63%

Rusakov V., Vasiliev S., Chabanenko V., Yurov A., Nabiałek A., Piechota S., Szymczak H.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

641-646

EN

The De Gennes and Matricon problem of finding the spectrum of oscillations of massive vortex line under the action of pinning and viscosity forces is solved. The obtained vibration spectrum of the vortex is discussed and the role of each contributing force is elucidated. The trajectory of the vortex motion is calculated and illustrated.

9

Size Effect in Impedance of Nb_3Al Superconductor

63%

Aleksyeyev P., Nabiałek A., Vasiliev S., Rusakov V., Chabanenko V., Zalutskii M., Piechota S., Szymczak H., Kodess B.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

555-559

EN

We present the results of the impedance measurements in Nb_3Al superconducting polycrystalline alloy vs. temperature and magnetic field. Using these results and applying the size effect model we calculate the flux-flow conductivity of the Nb_3Al superconducting alloy near its critical temperature.

10

The Influence of the Sample Shape on the Flux Jumps Dynamics in Conventional NbTi Superconductor

63%

Nabiałek A., Piechota S., Szymczak H., Vasiliev S., Chabanenko V., Rusakov V.

Acta Physica Polonica A

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2008

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vol. 114

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issue 1

235-241

EN

We investigated giant flux jumps, caused by thermomagnetic avalanches, in two cylindrical samples of conventional NbTi-50% superconductor of the same diameter -- 14 mm, but of different heights -- 4 mm and 20 mm. We studied the influence of demagnetizing effects on the flux jumps occurrence, the amount of the magnetic flux entering the sample during the following jumps and on the flux jumps dynamics. The dynamics of the magnetic flux entering the sample is compared with the dynamics of the stray field.

11

The Low-Field Ac Impedance of YBa_2Cu_3O_{7-δ} Superconducting Slab

63%

Aleksyeyev P., Reusenblatt E.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

99-104

EN

Using results of surface impedance measurements, the penetration of ac field into a melt-textured YBa_2Cu_3 O_{7-δ} slab was investigated. We obtained a linear correlation between the surface impedance and ac frequency. The impedance curve shifts towards higher temperatures - 0.9 K per decade of the frequency increase, for dc magnetic fieldμ_0H_{dc}≤8×10^{-3} T. This is an evidence of thermally activated flux creep. A plateau in the temperature dependence of the real impedance part was observed at approximately 88 K.

12

Two-Gap Superconductivity in 2H-NbS_2

63%

Pribulová Z., Leroux M., Kačmarčík J., Marcenat C., Klein T., Rodière P., Cario L., Samuely P.

Acta Physica Polonica A

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2010

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vol. 118

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issue 5

1024-1025

EN

We performed specific heat measurements of the superconducting single crystal of 2H-NbS_2 in the temperature range down to 0.6 K and magnetic fields up to 14 T. The temperature and magnetic field dependence of the electronic specific heat consistently indicate existence of two superconducting energy gaps in the system. The superconducting anisotropy depends on both temperature and magnetic field. Moreover, the angular dependence of the upper critical field deviates from the Ginzburg-Landau behavior and rather reminds that of MgB_2. All these features point to a multigap superconductivity in 2H-NbS_2. Our measurements are in a perfect agreement with the previous scanning tunneling spectroscopy of Guillamón et al.

13

Specific Heat of the Tb_{1-x}La_xNi_2 Solid Solutions

51%

Ćwik J., Palewski T., Nenkov K.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

343-346

EN

Specific heat measurements have been performed on the polycrystalline TbNi_2, LaNi_2 and their solid solutions Tb_{1-x}La_xNi_2 (x=0.2, 0.3). The Debye temperatures, phonon and conduction electron contributions as well as the magnetic part of the heat capacity were determined and discussed. The magnetocaloric effect was estimated from measurements performed in a magnetic field of 0.42 T for TbNi_2, Tb_{0.8}La_{0.2}Ni_2 and Tb_{0.7}La_{0.3}Ni_2.

14

Superconductivity in Lu_xZr_{1-x}B_{12} Dodecaborides with Cage-Glass Crystal Structure

51%

Sluchanko N., Azarevich A., Bogach A., Gavrilkin S., Glushkov V., Demishev S., Mitsen K., Shitsevalova N., Filippov V., Gabani S., Flachbart K.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

1036-1038

EN

We probed the evolution of the superconducting transition temperature T_c and the normal state parameters of Lu_xZr_{1-x}B_{12} solid solutions employing resistivity, heat capacity and magnetization measurements. In these studies of high-quality single crystals it was found that there are two types of samples with different magnetic characteristics. An unusually strong suppression of superconductivity in Lu_xZr_{1-x}B_{12} with a rate dT_c/dx=0.21 K/at.% of Lu was observed previously on the first "magnetic" set of crystals, and it was argued to be caused by the emergence of static spin polarization in the vicinity of non-magnetic lutetium ions. On the contrary, the second (current) set of "nonmagnetic" crystals demonstrates a conventional T_c(x) dependence with a rate dT_c/dx=0.12 K/at.% of Lu which is typical for BCS-type superconductors doped by nonmagnetic impurities. The reason for this difference is yet unclear. Moreover, the H-T phase diagram of the superconducting state of Lu_xZr_{1-x}B_{12} (0 ≤ x ≤ 1) solid solutions has been deduced from magnetization measurements.

15

Thermoelectric Power of MgB_2 Single Crystals Doped with Holes and Electrons

51%

Oganisian K., Rogacki K., Sulkowski C., Zhigadlo N., Katrych S., Karpinski J.

Acta Physica Polonica A

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2008

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vol. 114

|

issue 1

191-195

EN

The thermoelectric power of MgB_2 single crystals, non-substituted, single-substituted with C, and co-substituted with C and Li, was investigated in the temperature range from 10 to 300 K. Both the in-plane (S_ab) and the out-of-plane (S_c) thermoelectric powers are positive for non-substituted crystals and both S_ab and S_c change a sign for crystals doped with electrons when C is substituted for B in the amount larger than 6 at.%. The substitution of C, which supplies electrons mainly into the σ band, reduces the thermoelectric power anisotropy, most likely by increasing the interband scattering. When Li is additionally co-substituted for Mg, S_ab remains unchanged but S_c increases substantially. The Li substitution donates holes into the π band rather than into the σ band and in this way modifies the π band properties, including the possible increase in the intraband scattering.

16

DC NanoSQUID from Nb Thin Films

51%

Štrbík V., Pisarčík M., Gaži Š., Španková M.

Acta Physica Polonica A

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2017

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vol. 131

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issue 4

1054-1056

EN

We have prepared Nb thin film (thickness 80-100 nm) nanoSQUID with two symmetrically placed nanosized constrictions in superconducting loop. The nanoSQUID was prepared in two steps: at first a microsized SQUID was prepared and in the second step nanosized constrictions of the width of 120 nm in the SQUID loop were created by a focused ion beam technique. We studied the electrical and magnetic properties. From the obtained results, SQUID and constriction dimensions, the spin sensitivity was estimated to be about 50 μ_{B} Hz^{-1/2}. Further improvement of spin sensitivity is possible by lowering the SQUID and constriction dimensions.

17

Giant Magnetostriction Jumps in Conventional NbTi Superconductor

51%

Nabiałek A., Vasiliev S., Chabanenko V., Aleksyeyev P., Rusakov V., Piechota S., Szymczak H.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

633-639

EN

Magnetostriction of a large slab of conventional NbTi superconductor, with a diameter of about 6 mm, was investigated by the strain gauge technique. At the temperature of 4.2 K and in the external magnetic field of several T we found irreversible magnetostriction of an order of 10^{-5}, where the number means the relative changes of the slab diameter. This large magnetostriction is accompanied by giant magnetostriction jumps, caused by thermomagnetic avalanches. These thermomagnetic avalanches also cause giant jumps of the surface magnetization, which can be observed by using the Hall probes. The results were analyzed in the framework of the pinning induced magnetostriction model.

18

Superconducting Properties of NbN-SiO_2 Sol-Gel Derived Thin Films

51%

Kościelska B., Yuzephovich O., Bengus S., Witkowska A.

Acta Physica Polonica A

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2010

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vol. 118

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issue 2

383-385

EN

This work presents results of superconducting properties studies of xNbN-(100-x)SiO_2 (where x = 80 mol%) films of the thickness from 450 to 1950 nm. The films were prepared by thermal nitridation of sol-gel derived xNb_2O_5-(100-x)SiO_2 coatings. The nitridation process of Nb_2O_5-SiO_2 coatings leads to the formation of weakly disordered structures, with NbN metallic grains dispersed in the matrix of insulating SiO_2. All the samples in the normal state exhibit negative temperature coefficient of resistivity. Superconducting transition was not observed for the sample 450 nm thick. To examine the influence of magnetic field on superconducting properties of the films, the resistance versus temperature of 1350 and 1650 nm thick samples was measured in high magnetic fields. Resistive superconducting transitions are broadened due to the magnetic flux creep. The perpendicular upper critical magnetic fields for 1350 and 1650 thick samples are about 4.4 T. The critical temperatures of the superconducting transitions are about 4.5 K. Specific features of the magnetic field induced superconductor-insulator transition are found.

19

Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

51%

Abal'osheva I., Abal'oshev A., Cieplak M., Zhu L., Chien C.

Acta Physica Polonica A

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2010

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vol. 118

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issue 2

396-398

EN

The peculiarities of magnetic field penetration in the form of fingering or dendritic instabilities are studied by magneto-optical technique in the niobium films of different thickness. It is observed that the reduction of Nb film thickness reduces the threshold field for instabilities, in agreement with the theoretical predictions. In addition, it is shown that the silver overlayer deposited on the top of Nb film leads also to the enhancement of instabilities, in marked contrast to the effect of gold or aluminum overlayers, which are known to suppress instabilities.

20

Ultrathin Niobium in the Si/Nb/Si Trilayers

51%

Zaytseva I., Abal'oshev O., Dłużewski P., Minikayev R., Cieplak M., Zhu L., Chien C.

Acta Physica Polonica A

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2014

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vol. 126

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issue 4a

A-140-A-144

EN

We study magnetotransport properties of the Si/Nb/Si trilayers, in which the thickness of niobium, d, changes from 1.1 nm to 50 nm, while the thickness of Si is fixed at 10 nm. The niobium films are amorphous for d < 4 nm, while in thicker films the alligned polycrystalline grains are formed. We observe that the Hall coefficient changes sign into negative in the films with d < 1.6 nm. We also find that in the ultrathin films the magnetic field induces a transition from the superconducting into a metallic phase with the resistance smaller than the normal-state resistance.

Refine search results

Superconductivity and Magnetism of Dy_{1-x}Y_xRh_4B_4: Candidate for Spin-Triplet Cooper Pairing

Andreev Reflection Study of the Superconductor Mo_3Sb_7

On Superconducting Transition Temperature in Amorphous Alloys of Simple Metals

The Influence of Magnetic History on the Stability of Critical State and the Dynamics of Flux Jumps in Conventional NbTi Superconductor

Effect of Nano-SiC Doping on the Superconducting Critical Parameters in MgB_2/Fe Wires and Tapes

The Influence of the Magnetic Field on the Dynamics of the Flux Jumps in the Flux Flow Model

AC Microcalorimetry of Superconducting MgCNi_3 Single Crystals

Oscillating Dynamics and Trajectory of the Single Vortex Line

Size Effect in Impedance of Nb_3Al Superconductor

The Influence of the Sample Shape on the Flux Jumps Dynamics in Conventional NbTi Superconductor

The Low-Field Ac Impedance of YBa_2Cu_3O_{7-δ} Superconducting Slab

Two-Gap Superconductivity in 2H-NbS_2

Specific Heat of the Tb_{1-x}La_xNi_2 Solid Solutions

Superconductivity in Lu_xZr_{1-x}B_{12} Dodecaborides with Cage-Glass Crystal Structure

Thermoelectric Power of MgB_2 Single Crystals Doped with Holes and Electrons

DC NanoSQUID from Nb Thin Films

Giant Magnetostriction Jumps in Conventional NbTi Superconductor

Superconducting Properties of NbN-SiO_2 Sol-Gel Derived Thin Films

Inhomogeneous Magnetic Field Penetration in Superconducting Niobium Films

Ultrathin Niobium in the Si/Nb/Si Trilayers