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1

Magnetic Properties of Bismuth Ferrite Nanopowder Obtained by Mechanochemical Synthesis

100%

Szafraniak-Wiza I., Andrzejewski B., Hilczer B.

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vol. 126

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issue 4

1029-1031

EN

Multiferroic bismuth ferrite (BiFeO_{3}) nanopowders have been obtained at room temperature by mechanochemical synthesis. Depending on the post-synthesis processing the nanopowders exhibited differences in the mean sizes, presence of amorphous layer and/or secondary phases. Extended magnetic study performed for fresh, annealed and hot-pressed nanopowders revealed substantial improvement of the magnetic properties in the as-prepared powder.

2

Upper Critical Field for Cobalt Oxide Superconductors

100%

Mierzejewski M., Maśka M., Andrzejewski B.

Acta Physica Polonica A

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2004

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vol. 106

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issue 5

603-608

EN

Motivated by the recent discovery of the cobalt oxide superconductors, we calculate the temperature dependence of the upper critical field on a triangular lattice. Using the lattice version of the Gor'kov equations we investigate how the applied magnetic field affects singlet and triplet types of superconductivity. We show that in a wide range of model parameters not only Zeeman coupling, but also the diamagnetic pair breaking mechanism favors the triplet pairing. In the cobalt oxide superconductors the symmetry of the order parameter remains an open problem and both singlet and triplet superconductivity should be taken into account. We show that in such a case, an external magnetic field may induce a transition from singlet to triplet superconductivity. We discuss experimental results which may confirm this tempting hypothesis.

3

Negative Magnetisation and Absence of Superconductivity in RFe_4Al_8 (R=Lu, Yb) Compounds

100%

Andrzejewski B., Kowalczyk A., Toliński T.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

561-564

EN

We report researches for superconductivity and the effect of negative magnetisation in the RFe_4Al_8 (R = Lu, Yb) compounds by means of magnetic measurements and microwave absorption. Contrary to the earlier reports we do not confirm the existence of any traces of superconductivity in these compounds. Instead of the superconductivity and the Meissner effect, the YbFe_4Al_8 compound exhibits the effect of negative magnetisation, whereas the LuFe_4Al_8 compound shows an exact antiferromagnetic behaviour.

4

Superconducting Properties of Mo_2Re_3B_x-Mo_3Re_2B_x Eutectic

100%

Andrzejewski B., Guilmeau E., Kowalczyk A., Jurga W.

Acta Physica Polonica A

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2007

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vol. 111

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issue 5

727-735

EN

We synthesized, for the first time, superconducting eutectic composed of two new superconducting phases, namely of Mo_2Re_3B_x and of Mo_3Re_2B_x (where x≈1) and investigated its basic transport, magnetic, and microwave properties. The transition temperatures T_c were equal to 6.6 K and to 8.7 K for Mo_3Re_2B_x and Mo_2Re_3B_x compound, respectively. The phases present in the eutectic were identified by means of energy dispersion spectroscopy analyses. It was also shown that the two phases in the eutectic were separated by thin boron interface and formed regular network of the Josephson junctions which very effectively absorbed microwave energy.

5

Relation between Structure and Magnetic Properties of Microstructured PrAlO_3

100%

Andrzejewski B., Pawlak D., Klimczuk T., Turczyński S.

Acta Physica Polonica A

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2012

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vol. 121

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issue 5-6

1315-1317

EN

The magnetic properties of both the praseodymium-aluminium perovskite PrAlO_3 crystal and its microstructured version in the form of a PrAlO_3-PrAl_{11}O_{18} eutectic have been investigated. It is shown that R\overline{3}c → Imma 205 K first-order and Imma → C 2/m near 150 K second-order phase transitions in a PrAlO_3 single crystal are suppressed after structuring the material and embedding it in a PrAl_{11}O_{18} matrix. This behavior is related to the PrAl_{11}O_{18} matrix, which mechanically hinders expansion of the microrods and in this way suppresses the phase transitions.

6

Effect of Nd³⁺ Doping on Magnetic and Dielectric Properties of SrFe₁₂O₁₉ Hexaferrite Synthesized by Coprecipitation Method

88%

Hilczer A., Pasińska K., Markiewicz E., Pietraszko A., Andrzejewski B.

Acta Physica Polonica A

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2018

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vol. 133

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issue 3

669-672

EN

Magnetic and dielectric properties of hexagonal ferrites important for applications in microwave absorbers are strongly determined by the processing conditions. We studied dielectric and magnetic response of Sr_{1-x}Nd_{x}Fe₁₂O₁₉ (x=0, 0.03, 0.05, 0.07, 0.09) solid solutions obtained by coprecipitation method. The structure of the samples was controlled by X-ray diffraction and scanning electron microscope images revealed that the powder is a mixture of small nanograins and crystallites of 500 nm-1 μm in size. Nd³⁺ doping was found to result in an increase in the coercive field which we would like to relate to the domain wall pinning. The doping-induced changes are monotonous with x up to 0.07. The observed dispersion of permittivity was found to be correlated with the frequency behaviour of electric conductivity of the samples.

7

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

76%

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.

8

Superconductivity and Electronic Structure of the W_7Re_{13}B Compound

76%

Kowalczyk A., Andrzejewski B., Jezierski A., Toliński T., Szlaferek A., Falkowski M., Chełkowska G.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

597-600

EN

The superconductor W_7Re_{13}B has been studied by the magnetic measurements and microwave absorption. The crystal structure of W_7Re_{13}B is cubic (β-Mn type). This compound exhibits a sharp superconducting transition at a temperature of T_c=7.2 K. The electronic structure of W_7Re_{13}B has been studied by X-ray photoelectron spectroscopy and the band structure has been calculated by the full-potential local-orbital minimum-basis method using the scalar-relativistic mode. The main contribution to the density of states at the Fermi level is from 5d electrons of W and Re. The W and Re bands are similar and substituting W by Re does not change the total density of states.

9

Magnetic Properties of YBCO-PST Composites

76%

Andrzejewski B., Kaczmarek A., Stankowski J., Hilczer B., Marfaing J., Régnier S., Caranoni C.

Acta Physica Polonica A

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2000

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vol. 98

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issue 6

739-746

EN

The magnetic properties of granular superconductor-insulator composites were investigated. The composites were random composition of the YBa_{2}Cu_{3}O_{7-δ} (YBCO) high-temperature superconductor and Pb(Sc_{0.5}Ta_{0.5})O_{3} (PST) ferroelectric insulator. The composites exhibited lower superconducting volume ratio than the YBCO content. For samples with YBCO content low enough no global (the whole sample) and local (separated grains) superconductivity was observed. The observed decay of the superconductivity, lowering of the critical temperature, and the increase in number of paramagnetic centres as PST content increases are explained assuming reaction among YBCO and PST phases and possible formation of an additional ones, which did not exist in the initial powders.

10

Superconducting Regions and Kondo Effect of MgB_2 Formed by Implantation of Magnesium Ions into Boron Substrate

64%

Trybuła Z., Kempiński W., Andrzejewski B., Piekara-Sady L., Kaszyński J., Trybuła M., Piekoszewski J., Stanisławski J., Barlak M., Richter E.

Acta Physica Polonica A

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2006

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vol. 109

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issue 4-5

657-660

EN

The results of investigation of the polycrystalline boron implanted by magnesium and argon plasma pulse treatment are presented. The four-probe electric conductivity measurements and magnetically modulated microwave absorption showed the presence of superconducting islands below the temperature of 25 K. Below T=23 K we detected the Kondo effect, a logarithmic increase in the resistivity as the temperature is lowered, due to iron impurity.

11

Heat Capacity and Susceptibility of CeCu_4Al

64%

Reiffers M., Gažo E., Timko M., Kowalczyk A., Toliński T., Andrzejewski B., Šebek J., Šantavá E.

Acta Physica Polonica A

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2008

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vol. 113

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issue 1

425-428

EN

The heat capacity in the applied magnetic field up to 9 T, susceptibility and magnetization of polycrystalline CeCu_4Al are presented. The determined electronic heat capacity coefficient γ= 210 mJ mol^{-1} K^{-2} confirmed heavy fermion character of this compound. Magnetic ordering was not observed down to 0.5 K. Magnetic properties confirm these observations.

12

High-Pressure Microwave Study of YBa_{2}Cu_{3}O_{7-δ}-Pb(Sc_{0.5}Ta_{0.5})O_{3} Composite

64%

Czyżak B., Stankowski J., Hilczer B., Krupski M., Morawski P., Andrzejewski B., Marfaing J., Régnier S., Caranoni C.

Acta Physica Polonica A

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1997

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vol. 91

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issue 6

1103-1109

EN

The ferroelectric relaxor Pb(Sc_{0.5}Ta_{0.5})O_{3}-superconductor YBa_{2}Cu_{3}O_{7-δ} 50% in weight composite exhibits the onset critical temperature T_{c}=95 K. High pressure studies yield the factor dT_{c}/dp of 1.0 K/GPa, close to the value observed for a pure YBa_{2}Cu_{3}O_{7-δ} compound. The microwave absorption studies show the significant role of the intergrain weak links.

13

Magnetic Properties of YBa_{2}Cu_{3}O_{7-δ} Melt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

64%

Plesch G., Cígaň A., Maňka J., Bučkuliaková A., Hanic F., Buchta Š., Andrzejewski B., Stankowski J.

Acta Physica Polonica A

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2000

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vol. 98

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issue 4

327-334

EN

The microstructure and magnetic properties of the melt textured YBa_{2}Cu_{3}O_{7-δ} samples prepared by the powder melting process, in which Y_{2}Cu_{2}O_{5} and BaCuO_{2} were used as precursors, and those prepared by the quench and melt growth method are described and compared. The lattice parameters and T_{c} values for the samples prepared by the both techniques were similar. The penetration and the spatial distribution of the magnetic flux in the superconducting samples was imaged by means of a field-mapping device using a Hall probe. In the range of low magnetic fields up to 820Am^{-1} no significant differences in penetration of magnetic flux between the samples prepared by the powder melting process and the quench and melt growth were observed. The mapping could not resolve any grain boundaries, single grains and structural defects. By the ac and virgin volume magnetisation characteristics, which were measured in the zero-field cooled condition by a 2nd order SQUID gradiometer, no weak links were identified. Better magnetic properties of the quench and melt growth samples in high magnetic fields can be explained by the differences in microstructure and/or by the risen content of the finely dispersed 211 and Pt containing phases. The increase factor in magnetisation is about 2.5. Some aspects of the Bean model for textured YBa_{2}Cu_{3}O_{7-δ} samples are discussed.

14

The Evolution of Superconducting Phase MgB_x

64%

Łoś S., Kempiński W., Piekara-Sady L., Andrzejewski B., Jurga W., Kaszyńska K., Piekoszewski J., Werner Z., Barlak M.

Acta Physica Polonica A

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2008

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vol. 114

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issue 1

179-184

EN

Thin layers of MgB_x were studied in order to define evolution of superconducting phase after Mg ions implantation into boron substrate. Three fluencies of energies 140, 80, and 40 keV were used to establish proper stoichiometry to synthesize homogeneous MgB_2 film. Additionally, the annealing processes were carried out at temperatures 400, 500, and 600°C in a furnace in an atmosphere of flowing Ar-4%H_2 gas mixture. The quality of the superconducting material was examined by magnetically modulated microwave absorption, and magnetic and resistivity measurements. The results showed that T_c becomes higher with increasing annealing temperature. However, the fraction of superconducting phase decreases, due to partial evaporation of Mg ions and their deeper migration into boron substrate.

15

Formation of Superconducting Regions of MgB_2 by Implantation of Boron Ions into Magnesium Substrate

52%

Trybuła Z., Kempiński W., Andrzejewski B., Piekara-Sady L., Kaszyński J., Piekoszewski J., Werner Z., Richter E., Prokert F., Stanisławski J., Barlak M.

Acta Physica Polonica A

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2005

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vol. 108

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issue 1

165-170

EN

The results of investigation of the MgB_2 inter-metallic compound with the use of boron ions implantation and plasma pulse treatment are presented. The samples were characterized by: four-probe electric conductivity measurements, magnetically modulated microwave absorption, and magnetic measurements. For hydrogen and argon pulsed plasma treatment the samples with T_c ranging from 10 K to 32 K were obtained. The superconducting phase does not form a continuous layer since the resistivity does not fall down to zero. Apparently, separate islands of superconducting phase are connected through metallic Mg paths. All samples are still below the percolation threshold.

Refine search results

Magnetic Properties of Bismuth Ferrite Nanopowder Obtained by Mechanochemical Synthesis

Upper Critical Field for Cobalt Oxide Superconductors

Negative Magnetisation and Absence of Superconductivity in RFe_4Al_8 (R=Lu, Yb) Compounds

Superconducting Properties of Mo_2Re_3B_x-Mo_3Re_2B_x Eutectic

Relation between Structure and Magnetic Properties of Microstructured PrAlO_3

Effect of Nd³⁺ Doping on Magnetic and Dielectric Properties of SrFe₁₂O₁₉ Hexaferrite Synthesized by Coprecipitation Method

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

Superconductivity and Electronic Structure of the W_7Re_{13}B Compound

Magnetic Properties of YBCO-PST Composites

Superconducting Regions and Kondo Effect of MgB_2 Formed by Implantation of Magnesium Ions into Boron Substrate

Heat Capacity and Susceptibility of CeCu_4Al

High-Pressure Microwave Study of YBa_{2}Cu_{3}O_{7-δ}-Pb(Sc_{0.5}Ta_{0.5})O_{3} Composite

Magnetic Properties of YBa_{2}Cu_{3}O_{7-δ} Melt Textured Samples Prepared by Powder Melting Process and Quench and Melt Growth Techniques

The Evolution of Superconducting Phase MgB_x

Formation of Superconducting Regions of MgB_2 by Implantation of Boron Ions into Magnesium Substrate