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1
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Magnetization Processes of Nanoparticles Embedded into Ferromagnetic Matrix

100%
Ziółkowski G., Chrobak A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
597-599
EN
The paper refers to computer simulations of interactions between magnetically hard particle embedded into ultra-hard matrix. We used simulated annealing and Monte Carlo simulations in a frame of the 3D Heisenberg model. The performed simulations reveal that the particles show additional exchange anisotropy dependent on "frozen" spin direction in the matrix and the angle between matrix and particle easy magnetization axes. The particle-matrix coupling are responsible for multi-phase magnetic hysteresis shape and exchange-bias like effect.
2
Content available remote

Impact of Antisymmetric Anisotropy on Magnetisation of Ultra-Hard Nanocrystalline Alloys

100%
Ziółkowski G., Chrobak A.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1137-1140
EN
This paper describes an application of two-level Stoner-Wohlfarth model including antisymmetric anisotropy and two-level energetic model for simulations of magnetization processes in nanocrystalline, ultra-hard magnetic alloys. The simulation results have been compared with the experimental data obtained for the (Fe₈₀Nb₆B₁₄)_{0.88}Tb_{0.12} alloy. Moreover, the correctness of the proposed model was confirmed by the quantitative agreement with the direct Monte Carlo simulations of similar magnetic systems.
3
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Nanoscale Analysis of Superparamagnetic Systems

100%
Chrobak A., Ziółkowski G.
Acta Physica Polonica A
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2017
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vol. 131
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issue 5
1371-1374
EN
The paper refers to a kind of nanoscale characterization of superparamagnetic materials above and below the so-called blocking temperature. It is propose to apply the Stoner-Wohlfarth model of nanoparticles magnetization supplemented by the two-level kinetic model, determining behavior in T>0. This approach allows determination of distribution of magnetic moments and energetic barriers of magnetic objects based on magnetization curves. In many cases, the determined distribution of magnetic moments can be recalculated into average size of the magnetic objects giving finally a nano/microscaled picture of the material. The proposed method was successfully used in characterization of diluted magnetics, nanocomposites, powders and even for human hemoglobin. In the paper the basic theory and its application to the nanoscale characterization is discussed in detail.
4
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Magnetization Processes of Hard Magnetic Composites - Monte Carlo Studies aum

81%
Ziółkowski G., Granek K., Chrobak A.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
663-665
EN
In the present work we performed some simulated annealing plus Monte Carlo studies concerning a hard magnetic spherical particles embedded into soft ferromagnetic matrix as well as irregular branches of soft and hard magnetic phases. Magnetization process of such system depends on exchange interactions of soft and hard magnetic object and interface between them. Especially interesting is the comparison of interactions in systems with different, regular and irregular geometry.
5
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Phase Structure and Magnetic Properties of Fe-Nb-B-Pt Type of Bulk Nanocrystalline Alloys

81%
Ziółkowski G., Chrobak A., Randrianantoandro N., Klimontko J.
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vol. 126
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issue 1
174-175
EN
The paper refers to magnetic and structure properties of the (Fe_{80}Nb_{6}B_{14})_{1-x}Pt_{x} (x=0.15, 0.3, 0.4 and 0.6) bulk nanocrystalline alloys prepared using the vacuum suction casting technique. The samples were in the form of rods with diameters ranging from 0.5 mm to 1.5 mm. It was shown that the optimal Pt content is x=0.4 with the coercive field equal to 0.2 T and maximum energy product |BH|_{max}=11.2 kJ/m^{3}. The magnetic properties can be associated with Fe-Pt, Fe and Fe-B phases, depending on the alloy composition.
6
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Phase Stability of (Fe_{80}Nb_{6}B_{14})_{0.9}Tb_{0.1} Bulk Nanocrystalline Magnet

81%
Chrobak A., Ziółkowski G., Randrianantoandro N.
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vol. 126
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issue 1
176-177
EN
The paper refers to phase stability of the (Fe_{80}Nb_{6}B_{14})_{0.9}Tb_{0.1} bulk nanocrystalline alloys prepared using the vacuum suction casting technique. The samples were in the form of rods with diameters d=2, 1.5, 1 and 0.5 mm. Heating up to 900 K reveals structural changes that occur at temperatures above 680 K (DSC and M(T) measurements). The phase analysis, using Mössbauer spectra, indicates the decrease of Tb_{2}Fe_{14}B and increase of Fe content in the samples after the heat treatment. The most stable is the alloy with d=1 mm, where the formation of α-Fe phase was not observed. The decrease of d causes significant hardening i.e. coercive field increases from 0.57 T to 2.66 T for d=2 mm and d=0.5 mm, respectively.
7
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Influence of Cooling Rate on Magnetic Properties of (Fe_{80}Nb_{6}B_{14})_{1-x}Tb_{x} Type of Bulk Nanocrystalline Alloys

81%
Chrobak A., Ziółkowski G., Haneczok G.
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vol. 126
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issue 1
178-179
EN
The paper refers to magnetic properties of the (Fe_{80}Nb_{6}B_{14})_{1-x}Tb_{x} (x=0.06 and x=0.08) bulk nanocrystalline alloys prepared using the vacuum suction casting technique. The samples were in the form of rods with diameters of d=1.5 mm, 1 mm and 0.5 mm. It was shown that for the alloys with x=0.08 the significant magnetic hardening with the decrease of sample diameter was observed. For d=0.5 mm the coercive field equals 2.46 T and the maximum energy product |JH|_{max}=77.2 kJ/m^{3}.
8
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Content available

Ferroelectric–Ferromagnetic Composites Based on PZT Type Powder and Ferrite Powder

71%
Bochenek D., Niemiec P., Ziółkowski G., Zachariasz R., Chrobak A.
Archives of Metallurgy and Materials
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2013
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issue 4
9
Content available remote

Size Effect of Hard Magnetic Properties of Fe-Nb-B-Tb Milled Alloys

71%
Granek K., Ziółkowski G., Chrobak A., Klimontko J., Talik E.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
645-647
EN
The paper refers to magnetic and structural properties of powders made of Fe-Nb-B-Tb ultra-high coercive alloy. The initial alloy was milled in a low energy mill for 1 h and 14 h. With increasing milling time we observed gradual deterioration of hard magnetic properties i.e. the coercive field decreases from 5.51 T to 0.14 T for the bulk alloy and 14 h milled powder, respectively. However, for the 1 h milling time the micrometric powder reveals quite high coercivity of 2.77 T which is promising for possible applications in magnetic composites.
10
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Content available

Ultra-Fast Current Aided Sintering of High Coercive Magnetic Powders and Composites

62%
Granek K., Ziółkowski G., Chrobak A., Klimontko J., Rak J., Zivotsky O., Gembalova L.
Archives of Metallurgy and Materials
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2019
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vol. 64
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issue 2
11
Content available remote

Influence of Transition and Rare Earth Elements on Magnetic Properties of Fe-Nb-B-M (M~=~Ni, Ag, Gd,~Tb) Bulk Nanocrystalline Alloys

62%
Ziółkowski G., Randrianantoandro N., Chrobak A., Klimontko J., Kądziołka-Gaweł M., Haneczok G.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1266-1269
EN
In this work we present magnetic properties of the (Fe_{80}Nb_6B_{14})_{1-x}M_x (where M = Ni, Ag, Gd, Tb and x = 0.08, 0.16, 0.32) bulk nanocrystalline alloys prepared by making use of mould casting technique. The applied preparation technique is favorable to nanocrystallization of the alloys with mean diameters of crystallites ranged from about 10 nm to 30 nm. Phase identification reveals a formation of ternary RE_2Fe_{14}B and binary REFe_2 phases dependently on the alloy composition. It was found that for the alloys with Ag addition magnetic moment of Fe atom increases from 2.26 μ_{B} to 3.36 μ_{B} for x = 0.08 and x = 0.32, respectively. For Ni addition this quantity decreases with increasing x due to appearing of Fe-Ni (fcc) phases. For Gd, Tb additions the alloys are ferrimagnetic with compensation composition ranged between x = 0.08 and x = 0.16. The both rare earth alloying additions cause a significant magnetic hardening especially in the case of Tb.
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