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1
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Magnetic Properties of γ-Fe₂O₃ Nanopowder Synthesized by Atmospheric Microwave Torch Dischargie. Acta Physica Polonica A 122, 9 (2012), ERRATUM

100%
David B., Schneeweiss O., Šantavá E., Jašek O.
Acta Physica Polonica A
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2016
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vol. 129
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issue 1
168
EN
A nanopowder containing γ-Fe₂O₃ particles was synthesized by adding a gas mixture of H₂/Fe(CO)₅ into a microwave torch discharge at 1 bar. The presence of γ-Fe₂O₃ phase was confirmed by powder X-ray diffraction (mean crystallite size d_{XRD}=24 nm). The dominating characteristic sextets of γ-Fe₂O₃ were identified in the Mössbauer spectrum taken at 5 K. The presence of pure Fe₃O_4 in the nanopowder was excluded. The Mössbauer spectrum taken at 5 K exhibited six times larger total spectrum area than the Mössbauer spectrum taken at 293 K. Zero field cooled/field cooled curves measured down to 4 K in the magnetic field of 7.9 kA/m are reported.
2
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Properties of Ni_3Fe Nanoparticles Prepared by Chemical Method

100%
Zábranský K., Schneeweiss O., Pizůrová N., David B.
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issue 5
785-786
EN
Ni_3Fe nanoparticles prepared by calcination of the iron-nickel oxalate were investigated by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. The high temperature X-ray diffraction shows two stages of transformation of oxalate: (i) amorphization and (ii) formation of nanocrystalline Ni_3Fe particles. The development of coercivity, magnetization and mean coherence length ( ≈ particle size) is discussed.
3
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Low-Temperature Magnetic Properties of Nanocomposites Containing Superparamagnetic Fe_3C Particles

100%
David B., Schneeweiss O., Šantavá E., Morjan I.
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issue 5
766-767
EN
Two nanopowders containing superparamagnetic Fe_3C particles, superparamagnetic Fe_3O_4/γ-Fe_2O_3 particles and carbon black phase were synthesised by the method of laser-induced homogeneous pyrolysis of gaseous precursors. Both were characterised by X-ray diffraction, Mössbauer spectrometry and standard magnetic measurements. The mean crystallite size of Fe_3C was 3 nm for the first sample and 10 nm for the second sample. Mössbauer spectra measured at 27 K and zero-field cooled/field cooled curves measured down to 4 K are reported.
4
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Magnetic Properties of γ-Fe_2O_3 Nanopowder Synthesized by Atmospheric Microwave Torch Discharge

100%
David B., Schneeweiss O., Šantavá E., Jašek O.
Acta Physica Polonica A
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2012
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vol. 122
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issue 1
9-11
EN
A nanopowder containing γ-Fe_2O_3 particles was synthesized by adding a gas mixture of H_2/Fe(CO)_5 into a microwave torch discharge at 1 bar. The presence of γ-Fe_2O_3 phase was confirmed by powder X-ray diffraction (mean crystallite size d_{XRD}=24 nm). The dominating characteristic sextets of γ-Fe_2O_3 were identified in the Mössbauer spectrum taken at 5 K. The presence of pure Fe_3O_4 in the nanopowder was excluded. The Mössbauer spectrum taken at 5 K exhibited six times larger total spectrum area than the Mössbauer spectrum taken at 293 K. Zero field cooled/field cooled curves measured down to 4 K in the magnetic field of 7.9 kA/m are reported.
5
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Low-Temperature Magnetic Properties of Nanometric Fe-Based Particles

88%
David B., Schneeweiss O., Šantavá E., Alexandrescu R., Morjan I.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
561-564
EN
Fe-based nanoparticles were prepared by laser-driven pyrolysis. The as-synthesised powder consists ofα-Fe and Fe_3O_4/γ-Fe_2O_3 nanoparticles embedded in a pyrolytic carbon matrix. The crystallite size of 1.8 nm forα-Fe was calculated using the Scherrer formula. The as-synthesised nanopowder was superparamagnetic. The maximum of the zero-field cooling curve was observed at 32 K and the distribution of blocking temperatures g(T_B) peaked at 11 K. As a result of small particle sizes and the soft matrix, the Lamb-Mössbauer factor f was significantly higher at 4 K than at 293 K.
6
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Magnetic Properties and Structure of Non-Oriented Electrical Steel Sheets after Different Shape Processing

88%
Bulín T., Švábenská E., Hapla M., Ondrůšek Č., Schneeweiss O.
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EN
Non-oriented electrical steel sheets are the most often used materials in electrical rotary machines. Raw sheets must be formatted by various methods, e.g., punching, laser, spark or water stream cutting. Basic parameters of magnetic, electrical, and mechanical properties of the sheets are usually obtained from the producer, but namely magnetic properties are changed in dependence on additional machining processes. The aim of this study is to describe changes in magnetic properties after punching, laser or spark cutting of the original sheets M470-50A. The basic information about the structure of the cut edges of samples was obtained by optical microscopy and scanning electron microscopy. For the magnetic measurements toroidal samples were prepared by the mentioned technologies. The magnetic parameters were yielded from the measuring of magnetic hysteresis loops in dependence on saturation fields. The results are discussed from the point of view of applied cutting methods with the aim to obtain the best magnetic parameters and consequently determining the depth of the influenced material. After laser cutting, important decrease in remanence and increase in total losses were observed in comparison with the punched samples.
7
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Magnetic Interactions between Nanoparticles Formed during Calcination of Ferrihydrite

76%
Schneeweiss O., David B., Žák T., Filip J., Tuček J., Zbořil R., Mašláň M.
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issue 5
749-750
EN
Magnetic interactions between nanoparticles of magnetite Fe_3O_4 and α-Fe formed during calcination of ferrihydrite in H_2 at temperatures 533 ÷ 713 K were studied. The detailed phase analysis describes evolution of contents of magnetite and α-Fe. Explanation of an anomalous course of magnetic moment characterized by a local maximum at an early stage of formation of nanoparticles is discussed.
8
Content available remote

Nanocrystalline α-Fe Layer Examined by Mössbauer Spectrometry

76%
David B., Schneeweiss O., Pizúrová N., Rek A., Kudrle V., Jašek O.
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vol. 126
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issue 1
94-95
EN
A few micrometers thick nanocrystalline α-Fe layer with the mean crystallite size d_{XRD}=14 nm was deposited in low-pressure microwave plasma, using Fe(CO)_{5} vapour. Its nanocrystalline character was proved on its surface under SEM (surface was formed of deposited nanoparticles) and in its volume using TEM (deposited nanoparticles were stacked up, creating columns). No significant iron oxide phases were observed in the transmission ^{57}Fe Mössbauer spectrum measured at 5 K nor in the surface-sensitive ^{57}Fe conversion electron Mössbauer spectrum measured at 293 K.
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