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Clean Bulk YBaCuO Superconductors Doped by Paramagnetic Ions of Sm and Yb

100%
Jirsa M., Volochová D., Kováč J., Diko P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1027-1029
EN
The recently developed clean cuprate technology was employed to study the effect of tiny amounts of paramagnetic Yb and Sm ions on electromagnetic properties of bulk YBaCuO. Small samples of about 1.5×1.5×0.5 mm³ were measured by vibrating sample magnetometer in the field range ±9 T and temperatures 30 K to 10 K in the non-superconducting tetragonal state and 300 K to 70 K in the orthorhombic, superconducting state. In the latter case, we observed the reversible paramagnetic moment above T_{C}, similar as in the tetragonal state. Below T_{C} an irreversible magnetic moment was observed from which critical current density, J_c, was evaluated using the extended Bean model. The effect of doping by Yb and Sm ions on J_c was studied and a correlation between J_c and the total paramagnetic moment was found. Both J_c(B) and the normalized pinning force density as a function of the reduced magnetic field were analyzed in terms of the classical model and discussed with respect to the material anisotropy, giving us at least a rough idea on the type of the effective pinning type and mechanism.
2
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Magnetic Properties of a Melt-Textured Pellet of (Nd_{0.33}Eu_{0.38}Gd_{190.28})Ba_2Cu_3O_y + 0.035 mol% Zn

100%
Jirsa M., Rameš M., Muralidhar M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
223-226
EN
Recently, a striking positive effect of tiny Zn doping on crystal growth quality has been found in melt-textured (Nd, Eu, Gd)Ba_2Cu_3O_y pellets. The material could be easily grown from MgO seed, possessing a rather high lattice mismatch to the superconducting compound. In the present work we study spatial distribution of local magnetic properties and chemical composition of a (Nd_{0.33}Eu_{0.38}Gd_{0.28})Ba_2Cu_3O_y + 0.035 mol% Zn pellet. The plane cutting the pellet into two halves along the symmetry axes of the opposite a-axis growth sectors is investigated. While the chemical composition only slightly fluctuates, magnetic properties show quite an interesting spatial variation.
3
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Reversible Magnetization of Melt-Processed NEG-123 Superconductor

88%
Jirsa M., Rameš M., Muralidhar M., Kacmarcik J., Marcenat C.
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issue 5
1022-1023
EN
Specific heat of superconducting electrons was measured in a melt-processed (Nd_{0.33}Eu_{0.38}Gd_{0.28})Ba_2Cu_3O_{y} superconductor (NEG-123) with 5 mol% of Gd-211, 1 wt% Ag, and 0.035 mol% of Zn. The thermodynamic characteristics of this compound are still not well known. From calorimetric measurements the reversible magnetization, critical fields, penetration depth, and coherence length were deduced. In the vicinity of T_{c}, the reversible magnetic moment was additionally measured by means of SQUID.
4
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Electromagnetic Properties of Melt-Grown YBaCuO Superconductors Doped by Gd and Sm

88%
Jirsa M., Rameš M., Volochová D., Radušovská M., Diko P.
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vol. 126
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issue 1
326-327
EN
Electromagnetic properties of YBa_{2}Cu_{3}O_{y} samples melt-grown in air and doped with small amounts of light rare earth (LRE) ions Gd and Sm were studied. The LRE doping creates a point-like disorder contributing to the second peak on the magnetization curve. In the field range of the second peak the average magnetic moment, M_{av}, deduced from the magnetization curves exhibited strong fluctuations. M_{av} is commonly regarded as an equilibrium moment close to the thermodynamic reversible one, obeying in intermediate fields a logarithmic field dependence. However, in our experiments M_{av}(B) curves failed to follow such a dependence below irreversibility line. M_{av}(B) curves deduced from rather static measurements, done by SQUID magnetometer still showed the disturbance but significantly weaker. It indicates that this feature reflects the vortex dynamics in the second peak region. Its scaling with temperature was found to coincide with that of the pinning force.
5
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The Effect of Sm Addition on the Microstructure and Superconducting Properties of YBCO Bulk Superconductors

76%
Volochová D., Diko P., Piovarči S., Antal V., Kováč J., Jirsa M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1009-1011
EN
The effect of Sm addition on the microstructure and superconducting properties of Y-Ba-Cu-O (YBCO) bulk superconductors has been studied. Nominal composition: 1 mol YBa₂Cu₃O_{7-δ} + 0.25 mol Y₂O₃ + 1 wt% CeO₂ was enriched with different amounts of SmBa₂Cu₃O_y powder with the aim to increase critical current density, J_c, especially in higher magnetic fields by introducing additional pinning centers. Single grain YBCO bulk superconductors with SmBa₂Cu₃O_y (Y123-Sm) addition were prepared by the optimized top seeded melt growth process. Microstructure analysis, performed by polarized light microscope, revealed that SmBa₂Cu₃O_y addition leads to a higher amount of slightly coarser Y₂BaCuO₅ particles, which is related to lower critical current densities (J_c ≈ 6×10⁴ A/cm²) of the YBCO samples with SmBa₂Cu₃O_y addition in low magnetic fields. On the other hand, an enhancement of critical current density, J_c, in higher magnetic fields was observed for Y123-Sm samples. Moreover, a maximum trapped magnetic field, B_{tmax}, of 564 mT at 77 K in Y123-Sm, x=0.0025 sample (Ø 17.2 mm) was 43% higher than that for YBCO sample without any addition.
6
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Electron Behaviour of (Nd_{0.33}Eu_{0.2}Gd_{0.47})Ba_2Cu_3O_{y} Studied by Infrared Measurements

76%
Rameš M., Železný V., Phuoc V., Gervais F., Wolf T., Jirsa M.
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issue 5
938-939
EN
Optical properties of a are (Nd_{0.33}Eu_{0.2}Gd_{0.47})Ba_2 Cu_3O_y (NEG-123) single crystal interpreted in terms of the extended Drude model.
7
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Influence of Sm and Yb Pollution on Superconducting Properties of YBCO Bulk Superconductors

64%
Volochová D., Jurek K., Radušovská M., Piovarči S., Antal V., Kováč J., Jirsa M., Diko P.
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vol. 126
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issue 1
358-359
EN
YBa_{2}Cu_{3}O_{7-δ } (YBCO, Y-123) bulk superconductors with a nominal composition Y_{1.5}Ba_{2}Cu_{3}O_{x} and 1 wt% CeO_{2} addition were prepared by the Top Seeded Melt Growth (TSMG) process. Small single-crystalline pieces, cut from the SmBa_{2}Cu_{3}O_{y} (Sm-123) bulk, were used for seeding of epitaxial growth. Wavelength-dispersive spectrometry (WDS) confirmed the presence of 0.1 wt% Sm from the seed and 0.25 wt% Yb from the substrate, practically in the whole sample volume. The influence of this Sm and Yb contamination on superconducting properties of grown bulk materials is reported.
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