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1
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DC Magnetic Properties of Amorphous Vitrovac Ribbon

100%
Kollár P., Birčáková Z., Füzer J., Kuźmiński M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
675-677
EN
Soft magnetic amorphous Co-based materials prepared by rapid quenching method in the form of thin ribbon are well-known due to their excellent soft magnetic properties as high permeability, low coercivity, and low magnetic losses in kHz range. The amorphous Co-Fe-B-Si material Vitrovac® 6155 U55 produced by Vacuumschmelze GmbH & Co. KG belongs to this class of materials and was investigated in as-delivered state. The aim of this work was to study DC magnetization process by various experimental methods. We have measured magnetization curve by fluxmeter based hysteresis graph and hysteresis loops by three different fluxmeter based hysteresis graphs, exhibiting significant differences. The first and the second hysteresis graph perform the hysteresis loops measurement by the point-by-point method, either with commutative or with summing steps. The third one is AC hysteresis graph working at very low frequencies down to 7 mHz, performing the continuous method. The explanation of this result is based on the structural after effect influencing the domain wall displacement. We assumed that the domain structure consists of very small number of domain walls responsible for magnetization process, which was confirmed by the visualization of static domain structure by a computer-controlled setup based on the Kerr effect.
2
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Influence of Vitroperm Content on the Energy Losses in Composite Materials Based on the Mixture of Two Ferromagnets

88%
Birčáková Z., Kollár P., Vojtek V., Bureš R., Fáberová M.
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vol. 126
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issue 1
114-115
EN
Soft magnetic composites offer several advantages such as 3D isotropic magnetic properties and relatively small energy losses, finding use in electrical devices like electromotors, transformers or sensors. The aim of this work was to investigate the dc and ac magnetic properties of composites based on the mixture of two different ferromagnets: iron based material Somaloy® 700 and Vitroperm® 500 alloy. The analysis of total losses into dc losses, classical losses and excess losses showed that the classical and excess losses were negligibly small. The specific resistivity was increasing with the increasing fraction of Vitroperm (VPM). The coercivity exhibited maximum at 20% of VPM.
3
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Investigation of Total Losses of Non-Oriented Electrical Steels

76%
Füzer J., Birčáková Z., Zeleňáková A., Hrubovčák P., Kollár P., Predmerský M., Huňady J.
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issue 5
1018-1019
EN
The aim of this work was to investigate the influence of microstructural features on the soft magnetic properties. The materials chosen for this work were two types of the Epstein strips of commercially produced non-oriented electrical steels by U.S. Steel Košice. The AC magnetic properties in 0.2-100 Hz frequency range were obtained by measurements of AC hysteresis loops by a fluxmeter based non-standard single sheet AC hysteresisgraph. The influence of the grain size and magnetic domains structure on the partial contributions (hysteresis, eddy current and anomalous) to the total losses is also discussed. The results of the frequency dependence of the total losses, measured by a single sheet loop tracer along the rolling direction and perpendicular to the rolling direction, show different contribution of partial components.
4
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Investigation of Magnetization Processes from the Energy Losses in Soft Magnetic Composite Materials

76%
Birčáková Z., Kollár P., Weidenfeller B., Füzer J., Fáberová M., Bureš R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
684-686
EN
Soft magnetic composite materials are composed of small ferromagnetic particles insulated from each other. It gives them some very good properties e.g. the magnetic isotropy and low total energy losses at medium to higher frequencies. On the other hand, their structure gives rise to the negative aspects as the inner demagnetizing fields, resulting in some specifics in magnetization processes leading to the worsening of soft magnetic properties, particularly the excess losses increase and a lowering of permeability. The frequency dependence of excess losses, the low and high induction loss components and the inner demagnetization factors of soft magnetic composites were investigated in order to reveal the proportions of the reversible and irreversible magnetization processes. Higher excess losses were observed in samples with smaller particles or higher non-ferromagnetic content (resin+pores), in which the inner demagnetizing fields were higher. It was explained by lower effective number of movable domain walls in those samples, thus less irreversible magnetization processes. This was confirmed by low and high induction loss analysis, where total losses were divided into low and high induction loss components and plotted vs. frequency.
5
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Wide Frequency Range AC Magnetic Properties of Fe-Based Composite Materials

76%
Kollár P., Birčáková Z., Füzer J., Füzerová J., Bureš R., Fáberová M.
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issue 5
759-761
EN
The aim of this work was to analyze the influence of resin content on contribution of the hysteresis, eddy current and anomalous losses to the total losses in the frequency range from DC to 150 kHz. The samples of composite material were prepared in the form of the ring with outer diameter of 25 mm, inner diameter of 17 mm and height approximately 3 mm and in the form of cylinder with diameter of 25 mm and height approximately 3 mm by a compaction of mixture of iron powder ASC100.29 (90 vol.%) and commercial termoset resins. The DC hysteresis losses were obtained by the measurements of DC hysteresis loops and the total power losses in the frequency range 0.4 Hz-150 kHz from AC hysteresis loops, both at maximum induction 0.05, 0.1 and 0.2 T. The magnetic properties of the composite rings were compared with the properties of the material prepared from the powder supported by Höganäs AB Sweden. By analyzing the frequency dependence of total losses of the Fe-based SMC we found out that hysteresis losses contribute to the total losses as a majority component.
6
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Structure and Properties of Composites Based on Mixed Morphology of Ferromagnetic Particles

76%
Bureš R., Fáberová M., Strečková M., Birčáková Z., Kollár P., Füzer J.
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vol. 126
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issue 1
140-141
EN
Application potential of the soft magnetic composites increases with improvement of their functional properties. In addition to the magnetic properties, the mechanical properties of these materials are essential. The aim of this work was to investigate mechanical properties and their dependence on morphology of the ferromagnetic particles. Model composite based on Somaloy® and Vitroperm® powder was prepared using conventional powder metallurgy. The DC magnetic properties of composites based on two types of ferromagnetic particles with different shapes and structures are discussed in the relation with mechanical properties.
7
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DC Magnetic Properties and Complex Permeability of Ni-Fe Based Composites

64%
Onderko F., Jakubčin M., Dobák S., Olekšáková D., Birčáková Z., Kollár P., Füzer J., Fáberová M., Bureš R., Kurek P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
792-794
EN
We have investigated soft magnetic composite materials to better understand the influence of binder (resin) content on the DC magnetic properties and the complex permeability. Soft magnetic composite samples were composed from NiFe powder with phenol formaldehyde resin (ATM). Ferromagnetic magnetic powder for ring-shaped samples was obtained by milling of small pieces cut of NiFe sheets. The obtained powder was annealed to partially remove structural defects. The prepared powder was mixed with phenol-formaldehyde resin in different vol.%. The mixtures were pressed into the ring-shape samples. Complex permeability and DC magnetic properties (initial magnetization curves, anhysteretic curves and hysteresis loops) were measured. Higher inner demagnetizing fields in the resin containing samples were responsible for higher coercivity and hysteresis losses, but the permeability was stable up to much higher frequencies, compared to the sample without the resin.
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