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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
Content available remote

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
Content available remote

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
Content available remote

Thermal Stability and Mechanism of Thermally Induced Crystallization of Fe_{73.5}Cu₁Nb₃Si_{15.5}B₇ Amorphous Alloy

76%
Vasić M., Minić D., Blagojević V., Žák T., Pizúrová N., David B., Minić D.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
657-660
EN
Investigation of thermal stability of the alloy revealed stepwise crystallization process, manifested by two distinct complex exothermic peaks in differential scanning calorimetry curves. Kinetic parameters of individual crystallization steps were found using the Kissinger and Vyazovkin methods. Structural characterization of thermally treated samples showed formation of different iron-based phases including α-Fe(Si), Fe₂B, Fe₁₆Nb₆Si₇ and Fe₂Si and some metastable intermediary species. Morphology characterization of the surface and cross-section of the thermally treated samples showed granulated structure composed of several different phases and indicated occurrence of impingement effects during crystal growth. Value of estimated lifetime suggested very high stability against crystallization at room temperature and abrupt decrease of lifetime with temperature increase.
7
Content available remote

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

Structure and Magnetic Properties of Nanocrystalline NiFe_{2}O_{4} Prepared via Precipitation Route

76%
Žák T., David B., Ćosović A., Ćosović V., Živković D., Talijan N.
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vol. 126
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issue 1
142-143
EN
Nanocrystalline Ni-ferrite was synthesized by modified precipitation method in which soluble starch is used as dispersing agent and Na_{2}CO_{3} as a precipitating agent. NiSO_{4}·6H_{2}O and Fe(NO_{3})_{3}·9H_{2}O were used as precursors for nickel and ferric oxide, respectively. The obtained nanocrystalline Ni-ferrite was analysed and discussed through structural, compositional and magnetic characterization. Formation of pure NiFe_{2}O_{4} phase with average crystallite size of 21 nm has been confirmed by X-ray diffraction analysis (XRD). The determined phase composition was additionally supported by results of ^{57}Fe Mössbauer phase (MS) analysis and material's nanocrystalline structure by field emission scanning electron microscopy (FE-SEM). Thermomagnetic behaviour was studied up to 800 °C. The obtained room temperature magnetic hysteresis loop, recorded by means of a vibrating sample magnetometer (VSM), exhibits characteristic "S" shape of the soft magnetic material with the measured coercivity of about 10 kA/m and the specific moment up to 40 Am^{2}/kg.
9
Content available remote

Growth, Morphology and Superconductivity of Epitaxial (RE)_{1}Ba_{2}Cu_{3}O_{7-δ} Films on SrTiO_{3} and NdGaO_{3} Substrates

76%
Krumme J.-P., David B., Doormann V., Eckart R., Rabe G., Dössel O.
Acta Physica Polonica A
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1997
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vol. 92
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issue 1
55-68
EN
The growth of (RE)_{1} Ba_{2}Cu_{3}O_{7-δ} (RE: Y, Nd) films on NdGaO_{3} and SrTiO_{3} substrates by ion-beam and dc-/rf-magnetron sputter deposition is discussed in the framework of growth kinetics, oxygen exchange, epitaxial relations, substrate crystal orientation, in-plane coherence, vicinal substrate cuts, overgrowth on steps, superconductor/insulator combinations, and patterning by ion-beam etching. The process conditions for ion-beam and magnetron sputter deposition are briefly outlined.
10
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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