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  1. 17 Acta Physica Polonica A

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  1. 4 Diko P.

  2. 3 Antal V.

  3. 3 Zmorayová K.

  4. 3 Šefčiková M.

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1
Content available remote

Structural Determination of Epitaxial Formations in Layered Cuprates

100%
Leonyuk L., Maltsev V., Babonas G.-J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
143-146
EN
The fragment approximation is used for the description of the layered cuprate structures. The characteristic structural features are distinguished which genetically relate all the layered cuprates. The classification scheme for the whole family of layered cuprates is analyzed in the fragment approximation and a possible extension of the scheme is discussed.
2
Content available remote

Epitaxial Intergrowth of Isostructural Phases in Bi-2212 Single Crystals

100%
Babonas G.-J., Leonyuk L., Maltsev V.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
251-254
EN
The isostructural phases in Bi-2212-type HTSC were studied by structural and optical methods. The epitaxial intergrowth was shown to be a feature typical of single crystals composed of several isostructural phases. The physical properties of the multi-phase samples were interpreted on the basis of reference mono-phase samples. A presence of the intergrowth interface was assumed to be responsible for particular features in multi-phase samples.
3
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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.
4
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Ultrathin NbN Films for Superconducting Single-Photon Detectors

80%
Słysz W., Guziewicz M., Borysiewicz M., Domagała J., Pasternak I., Hejduk K., Rzodkiewicz W., Ratajczak J., Bar J., Węgrzecki M., Grabiec P., Grodecki R., Węgrzecka I., Sobolewski R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 1
200-203
EN
We present our research on fabrication and structural and transport characterization of ultrathin superconducting NbN layers deposited on both single-crystal Al_2O_3 and Si wafers, and SiO_2 and Si_3N_4 buffer layers grown directly on Si wafers. The thicknesses of our films varied from 6 nm to 50 nm and they were grown using reactive RF magnetron sputtering on substrates maintained at the temperature 850°C. We have performed extensive morphology characterization of our films using the X-ray diffraction method and atomic force microscopy, and related the results to the type of the substrate used for the film deposition. Our transport measurements showed that even the thinnest, 6 nm thick NbN films had the superconducting critical temperature of 10-12 K, which was increased to 14 K for thicker films.
5
Content available remote

Microstructural and Magnetic Characteristics of Divalent Zn, Cu and Co-Doped Ni Ferrites

80%
Šoka M., Dosoudil R., Ušáková M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
690-692
EN
Divalent zinc, copper and cobalt doped nickel ferrites with the chemical formula Ni_{1-x-y-z}Zn_{x}Cu_{y}Co_{z}Fe₂O₄ where x values ranging from 0.4 to 0.6, y=0.1, z=0.01 and 0.02 have been synthesized by conventional ceramic method. The effect of Zn²⁺, Cu²⁺ and Co²⁺ ions substitution on the selected microstructural and magnetic characteristics have been investigated to examine the utility of prepared ferrite materials for high-frequency applications. X-ray diffraction measurements confirmed the single-phase spinel cubic structure in all the samples and modifications in lattice parameter according to the ionic radii size of doped ions. The net magnetic moment, given by the differences between the magnetic moments of A and B sublattice, increased with raising substitution of Ni²⁺ ions. The measured frequency dispersion of complex permeability was discussed in terms of the changes in chemical composition, microstructure and the associated processes of resonance and/or relaxation due to domain wall movements and damping of spin rotations contributing to the fall of permeability and rise of magnetic losses.
6
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Content available

Oxygen Deficient YBa_2Cu_3O_{7-δ}: Two Superconducting Phases

80%
Stankowski J., Ślązak A., Kempiński W., Andrzejewski B., Reichel B., Plesch G.
Acta Physica Polonica A
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2004
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vol. 105
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issue 3
287-294
EN
A set of oxygen deficient powder and granular samples of YBa_2Cu_3O_{7-δ} ceramics was studied by means of thermogravimetric and magnetically modulated microwave absorption methods. Especially the last method has turned out to be a powerful method, which was used to determine the dependence of critical temperature T_c on the oxygen parameterδ. Using these methods it has been shown that the removing of oxygen evokes the inhomogeneous oxygen distribution in the samples and a change in carrier concentration till to the loss of superconducting properties. A superconducting phase with T_c=60 K, which occurs in oxygen deficient YBa_2Cu_3O_{7-δ} sample, is an unstable phase.
7
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Technology of Ultrathin NbN and NbTiN Films for Superconducting Photodetectors

80%
Guziewicz M., Slysz W., Borysiewicz M., Kruszka R., Sidor Z., Juchniewicz M., Golaszewska K., Domagala J., Rzodkiewicz W., Ratajczak J., Bar J., Wegrzecki M., Sobolewski R.
Acta Physica Polonica A
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2011
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vol. 120
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issue 6A
A-76-A-79
EN
We report fabrication and characterization of ultrathin NbN and NbTiN films designed for superconducting photodetectors. Our NbN and NbTiN films were deposited on Al_2O_3 and Si single-crystal wafers by a high-temperature, reactive magnetron sputtering method and, subsequently, annealed at 1000°C. The best, 18 nm thick NbN films deposited on sapphire exhibited the critical temperature of 15.0 K and the critical current density as high as ≈ 8 × 10^6 A/cm^2 at 4.8 K.
8
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Codoping Effect of Zn and Pr in YBa_2Cu_3O_{7-δ}

80%
Naik M., Sarode P., Prabhu R., Priolkar K., Vasanthacharya N.
Acta Physica Polonica A
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2009
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vol. 115
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issue 3
742-744
EN
In this paper we present the resistivity data for Pr and Zn codoped compound Y_{1-x}Pr_xBa_2[Cu_{1- y}Zn_y]_3O_{7-δ} with 0 & y & 0.1 and x=0.0, 0.1 and 0.2. The data is analysed in terms of the superconducting critical temperature T_c, residual resistivity ρ_0 and the resistivity slope dρ/dT corresponding to the linear ρ-T region. It is found that for x=0.1 Pr has a minimal influence on the in-plane processes for Zn impurity alone affecting slightly T_c and ρ_0. The slope dρ/dT becomes larger for 0.03 & y & 0.06 leading to larger depining effect and hence slower fall of T_c as a function of y. For x = 0.2 there is a drastic change, ρ_0 becomes abnormally large, dρ/dT becomes negative implying absence of depinning and a totally pinned charge stripes. Superconductivity vanishes at y=0.03. It is concluded that for x = 0.2 Pr converts the system from overdoped to underdoped region leading to the universal superconductor-insulator transition.
9
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Superconductivity in Lu_xZr_{1-x}B_{12} Dodecaborides with Cage-Glass Crystal Structure

80%
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.
10
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Effects of Europium-Barium Nonstoichiometry in EBCO123 Systems on Transition and Magnetization Properties

80%
Cigáň A., Maňka J., Kopčok M., Polovková J., Jurdák P., Koňakovský A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
219-222
EN
We studied the effects of Eu-Ba nonstoichiometry in two series of Eu_{1+x}Ba_{2-x}Cu_3O_{7-δ} and Eu_{1-x}Ba_{2+x}Cu_3O_{7-δ} samples on transition, structural, and magnetic properties. The samples with the nominal composition of 0≤x≤0.07 were synthesized by the solid-state reaction method from Eu_2O_3, BaCO_3, and CuO precursors and sintered at 1050°C for 72 h in flowing oxygen. All the samples show the values of critical temperature T_c, volume density ρ, and maximum volume magnetization M_{max} higher than 90 K, 6.3 g cm^{-3} and 10^4 Am^{-1}, respectively, except for x = 0.07 samples. The Eu-Ba nonstoichiometry in the two series shows different effects on transport, magnetization hystereses, and intergrain properties of the samples.
11
Content available remote

The Superconducting and Magnetic States in RuSr_2GdCu_2O_8, Based on the Magnetic, Transport and Magneto-Caloric Characteristics

70%
Klamut P., Plackowski T.
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issue 2
254-260
EN
The article discusses selected properties of the non- and superconducting polycrystalline samples of RuSr_2GdCu_2O_8 and comments on the consequences of introducing insignificant sub-stoichiometry of Ru into the nominal formula. The magneto-resistive and the magnetic characteristics are interpreted in favour of the formation of intrinsically inhomogeneous superconducting phase, which seems stabilized along with the structural modifications enhanced with the modification of starting stoichiometry. The specific heat data reveals the small shift of the temperature of magnetic ordering T_{m}, which may suggest dilution of the magnetic sublattice of the Ru moments. The measurements of the magnetic field dependences of the isothermal magnetocaloric coefficient M_{T} reveal no gain in the system magnetic entropy in a broad range of accessed fields and temperature. Whereas the multi-component character of the compound's magnetsm precludes from concluding on the magnetic ground state, the maximum in M_T (H), which occurs at comparably weak magnetic field for temperatures in a vicinity of T_{m} may reflect dominance of the ferromagnetic type interactions with a constrained correlation range. The literature explored models for the Ru magnetic ordering and also possible phase separation are brought into the discussion.
12
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Time Dependent Changes in Ag Doped YBCO Superconductors

70%
Volochová D., Antal V., Diko P., Šefčiková M., Zmorayová K., Kováč J., Weber H., Chaud X.
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issue 5
1047-1048
EN
Magnetization measurements at 77 K were conducted on the single-crystalline samples of YBCO superconductor doped with Ag prepared by the top-seeded melt-growth process. The single-grain samples had a nominal composition Y_{1.5}Ba_2(Cu,Ag)_3O_{y}. Magnetization measurements on the samples, oxygenated by two different processes: by standard oxygenation and by high pressure oxygenation, repeated after 24 months, revealed time dependent changes in magnetization behaviour and critical transition temperatures, T_{c}, which could be associated with redistribution of oxygen vacancies and their interaction with Ag dopant atoms.
13
Content available remote

Magnetic Properties of FeSeTe Compound Crystallized from Liquid Phase

70%
Lewandowski S., Berkowski M., Tarenkov V., D'yachenko A., Abal'oshev A., Abal'osheva I., Gawryluk D., Domukhovski V., Sidorov S., Boichenko D.
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issue 2
289-291
EN
We report on measurements of samples with nominal composition FeSe_{0.5}Te_{0.5}, crystallized by the Bridgman method. Magnetic and transport properties of the samples were examined. The measurements confirm the coexistence of ferromagnetism and superconductivity below the superconducting transition temperature. The ferromagnetic contribution to magnetization, estimated at 10%, might be caused by the presence of ferrimagnetic Fe_7Se_8, which occupies about 10% of sample volume. From the Andreev spectroscopy we found superconducting energy gap Δ = 2.6 meV at T = 4.2 K, and from magnetization measurements the critical temperature T_c = 15.8 K. The critical current density in magnetic field H = 4 kOe, determined from magnetization measurements, is j_c = (1-2) × 10^4 A/cm^2 and weakly depends on magnetic field intensity.
14
Content available remote

Structure and Superconductivity of FeSe_{1 - x} and FeTe_{1 - y}Se_{y} Crystals: Dependence on the Synthesis Methods, Starting Composition, and Growth Conditions

70%
Gawryluk D., Fink-Finowicki J., Wiśniewski A., Puźniak R., Domukhovski V., Diduszko R., Berkowski M.
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issue 2
331-335
EN
Syntheses of superconducting iron chalcogenides FeSe_{1 - x} (x = 0-0.15) and FeTe_{1 - y}Se_{y} (y = 0.3-0.55) were performed. Superconducting phase of iron selenide was obtained by the solid-state reaction and from liquid phase. The highest values of critical temperature (T_c = 8.2-8.7 K) exhibit FeSe_{1-x} obtained by the crystallization from a melt with excess of iron less than 1 mol%. The samples from a melt contain up to 78% of tetragonal phase, as estimated by the X-ray diffraction. Lattice parameters and unit cell volume for the samples exhibiting highest T_{c} and sharpest transition to superconducting state are limited to narrow range, with c/a ratio close to 1.469. The samples with excess of selenium contain higher amount of hexagonal phase than stoichiometric one. Superconducting single-crystalline samples of FeTe_{1 - y}Se_{y} (up to 100% of tetragonal phase) were obtained using Bridgman's method. When y value increases, the volume of unit cell decreases. The critical temperature T_{c} changes from ≈ 11.5 K for y ≈ 0.3 to ≈ 14.7 K for y ≈ 0.5.
15
Content available remote

Microstructure and Properties of Y-123/Y-211 Bulk Superconductors with BaCeO_{3} and BaO_{2} Addition

61%
Zmorayova K., Antal V., Radusovska M., Piovarci S., Volochova D., Diko P.
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vol. 126
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issue 1
366-367
EN
YBa_{2}Cu_{3}O_{7-δ} (YBCO) bulk single-grain superconductors were prepared by a TSMG process. CeO_{2}, BaCeO_{3} and BaO_{2} powders were added to nominal composition Y_{1.5}Ba_{2}Cu_{3}O_{7} with the aim to refine Y_{2}BaCuO_{5} (Y-211) secondary particles. Added powders were refined by milling in a friction milling and characterized by X-ray powder difractometry. Thermal properties of the systems were characterized by DTA. Microstructure of samples was studied by PLM. Successful refinement of Y-211 particles size was confirmed by IP measurements. Transition temperatures and field dependences of the magnetic moment for further determination of the critical current densities were obtained using a VSM.
16
Content available remote

Growth Rate of YBa_2Cu_3O_7 Bulk Crystals in Y_{1.5}Ba_2Cu_3 System with CeO_2 Addition

61%
Zmorayová K., Šefčiková M., Volochová D., Kalmanová M., Piovarči S., Diko P.
Acta Physica Polonica A
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2012
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vol. 122
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issue 4
725-727
EN
The growth rate of Y_1Ba_2Cu_3O_{x} bulk single grain (in fact single crystal) superconductors in the system with composition Y_{1.5}Ba_2Cu_3O_{x} and CeO_2 addition was studied in the temperature range 991-1001°C. It is shown that the growth rate of bulk crystal is different for a- and c-growth direction. Slower measured growth rate in studied system than in pure Y_1Ba_2Cu_3O_{x} is related to the composition shift to the three-phase field containing CuO.
17
Content available remote

Coexistence of Ferromagnetism and Superconductivity in Rapidly Quenched Ni_2NbSn Heusler Alloy

61%
Kanuch P., Ryba T., Gamcová J., Kanuchova M., Durisin M., Saksl K., Vargova Z., Varga R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1057-1059
EN
We present the study on production and structural, electric and magnetic properties of superconductive Ni₂NbSn Heusler alloy. The sample has been produced by melt-spinning method using tangential speed of copper wheel 20 m/s. Polycrystalline structure has been obtained showing single phase with B2 disorder with lattice constant a=6.1654 Å. Resistance measurement shows superconductive behavior with critical temperature close to 5 K. Magnetic measurements also exhibit diamagnetic contribution from superconductive phase. Additionally, the ferromagnetic state has been observed below 20 K, which points to the coexistence of magnetic and superconducting state.
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