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1

Critical Current Limitations and Irradiation Effects in High-Temperature

100%

Wiśniewski A., Puźniak R., Baran M., Szymczak H.

Acta Physica Polonica A

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1993

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vol. 84

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issue 1

139-164

EN

The discovery of high-temperature superconductors stimulated many groups of researchers to study properties of these materials. From the basic point of view the most important problem is to clarify the mechanism of high-temperature superconductivity. From the practical point of view the most challenging task is to find mechanisms of strong pinning of the vortices, and thereby to obtain materials with high critical current density. The aim of this paper is to discuss problems connected with critical current limitations and to present possibilities which offer irradiation effects with respect to critical current enhancement.

2

Comparison of Flux Pinning in Single Crystals and Melt-Textured YBa_{2}Cu_{3}O_{7-x}

100%

Puźniak R., Wiśniewski A., Baran M., Zhou L.

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EN

Flux pinning properties of single crystals and melt-textured samples of YBa_{2}Cu_{3}O_{7-x} were studied for external magnetic field oriented parallel and perpendicular to the CuO_{2} planes (ab-planes). For H ∥ ab vortex behaviour is mainly determined by a very effective intrinsic pinning mechanism. The irreversibility line is located in the region of higher fields and temperatures in comparison with the irreversibility line for H ⊥ ab. In a single crystal for H ⊥ ab, we observed an increase in the critical current density j_{c} with magnetic field - the so-called "fishtail effect" - in a very broad temperature range. For H ∥ ab, this effect is observed only at temperatures close to T_{c}, when the intrinsic pinning is much weaker.

3

Reappearance of Antiferromagnetic Order in Nd_{0.9}Ca_{0.1}BaCo_{2}O_{5+δ} for δ > 0.51

100%

Piętosa J., Kolesnik S., Puźniak R., Dabrowski B.

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EN

The absence of the antiferromagnetic order in Nd_{0.9}Ca_{0.1}BaCo_2O_{5.5} has been found to remain unchanged by applying a hydrostatic pressure of 10 kbar. In magnetic studies of polycrystalline Nd_{0.9}Ca_{0.1}BaCo_2O_{5+δ} (δ=0.07-0.69), we have found a reappearance of the antiferromagnetic phase, caused by an increase in oxygen index δ above 0.51 related to extra oxygen ions addition into the NdO_{δ} plane. For the samples with δ=0.555 and 0.59, a coexistence of well developed antiferromagnetic phase with ferrimagnetic one is evidenced.

4

Influence of Pressure on Magnetic Properties of La_{1-x} Sr_xCoO_{3-δ}(x=0.5, 0.67, 1)

76%

Piętosa J., Wiśniewski A., Puźniak R., Kolesnik S., Majjiga M., Dabrowski B.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

527-532

EN

Influence of pressure on the phase transition temperature T_C and on the spontaneous magnetisation M_{0} of highly Sr substituted and oxygen nonstoichiometric La_{1-x}Sr_xCoO_{3-δ} samples was investigated. An increase in T_C and M_0 with pressure in investigated samples was found, indicating strengthening of ferromagnetic double exchange interactions, and the expansion of volume of ferromagnetic phase as a~result of enhancement in ferromagnetic interactions in both cluster-glass and long range ferromagnetic states. We did not observe clear correlation between changes in pressure coefficient dT_C/dP and changes in the formal oxidation state of the Co ion.

5

Influence of Hydrostatic Pressure on Magnetic Properties of (Sr,La)(Ru,Cr,Mn)O_3

76%

Piętosa J., Wiśniewski A., Puźniak R., Kolesnik S., Majjiga M., Dabrowski B.

Acta Physica Polonica A

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2007

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vol. 111

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issue 1

159-163

EN

An influence of hydrostatic pressure, P, on phase transition temperature, T_C, and spontaneous magnetisation, M_0, of selected perovskite ruthenates (SrRuO_3, La_{0.2}Sr_{0.8}RuO_3, SrRu_{0.9}Mn_{0.1}O_3, and SrRu_{0.9}Cr_{0.1}O_3) was determined to 12 kbar. A decrease in T_C with pressure was found for all of the studied samples. The M_0(P) remains unchanged for most of the samples, except for the La_{0.2}Sr_{0.8}RuO_3 sample. The weakening of ferromagnetic interactions with increasing pressure is consistent with complex band structure effects related to the modulation of the Ru-O hybridisation by the change of structural distortion.

6

Anisotropic Magnetic Susceptibility of Neodymium Substituted SrLaAlO_{4} Crystals

76%

Fink-Finowicki J., Puźniak R., Baran M., Jabłoński R., Berkowski M., Pajączkowska A., Szymczak H.

Acta Physica Polonica A

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1994

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vol. 85

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issue 3

633-637

EN

The uniaxial anisotropy of magnetic properties of SrLa_{1-x}Nd_{x}AlO_{4} single crystals (x = 0.01 and 0.05) was found from the measurements of temperature dependencies of magnetic susceptibility. Results of measurements, with magnetic field along a- and c-axis, are compared with the similar data obtained for CaNdAlO_{4} crystal. The successful description of experimental data was done in frames of the crystal field approximation. The anisotropy of magnetic susceptibility appears due to crystal field acting on magnetic neodymium ions in a system without exchange interactions.

7

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

76%

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.

8

Magnetic and Structural Study of Mn_{1.15}Fe_{0.85}P_{1-x}Ge_{x} (0.25 < x < 0.32) Magnetocaloric Compounds Prepared by Arc Melting

64%

Hawelek L., Wlodarczyk P., Zackiewicz P., Polak M., Kaminska M., Puźniak R., Radelytskyi I., Kolano-Burian A.

Acta Physica Polonica A

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2015

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vol. 128

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issue 1

76-80

EN

Recently, room temperature magnetocaloric materials increasingly attracted attention in the development of magnetic refrigerators. In this paper, an effect of P/Ge substitution on the magnetic phase transition in the series of Mn_{1.15}Fe_{0.85}P_{1-x}Ge_{x} (0.25 < x < 0.32) magnetocaloric compounds prepared by the arc melting technique and subsequent homogenization process has been studied. Calorimetric and magnetization results show that the temperature of structural phase transition coincide with the Curie temperature and fall within the temperature range 270-355 K. The magnetic entropy change reaches the maximum value for the compound with x=0.28 and equals to 32 J/(kg K) for the magnetic field change of 5 T. The adiabatic temperature change for the same sample, measured using magnetocalorimeter, is equal to 1.2 K for the magnetic field change of 1.7 T. It was found that the increase of Ge content in the sample causes weakening of first order magnetic transition, which is manifested by the lowering difference in transition temperature measured in two zero-field-cooling and field-cooled-cooling regimes.

Refine search results

Critical Current Limitations and Irradiation Effects in High-Temperature

Comparison of Flux Pinning in Single Crystals and Melt-Textured YBa_{2}Cu_{3}O_{7-x}

Reappearance of Antiferromagnetic Order in Nd_{0.9}Ca_{0.1}BaCo_{2}O_{5+δ} for δ > 0.51

Influence of Pressure on Magnetic Properties of La_{1-x} Sr_xCoO_{3-δ}(x=0.5, 0.67, 1)

Influence of Hydrostatic Pressure on Magnetic Properties of (Sr,La)(Ru,Cr,Mn)O_3

Anisotropic Magnetic Susceptibility of Neodymium Substituted SrLaAlO_{4} Crystals

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

Magnetic and Structural Study of Mn_{1.15}Fe_{0.85}P_{1-x}Ge_{x} (0.25 < x < 0.32) Magnetocaloric Compounds Prepared by Arc Melting