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1
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Magnetostriction Measurements of (Fe-Co)-Mo-Cu-B Alloys with Varying Atomic Fe/Co Ratio

100%
Vlasák G., Janičkovič D., Švec P.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
107-110
EN
Amorphous rapidly quenched ribbons of (Fe-Co)_{76}Mo_8Cu_1B_{15} with the ratio Co/Fe = 0, 1/9, 1/6, 1/4, 1/3, 1/2, 1/1 and 2/1 were prepared by planar flow casting. The dependence of the Curie temperature T_C on Co/Fe ratio was determined. Due to the presence of the invar effect it was possible to measure the spontaneous volume magnetostriction in the temperature interval between 300 K and T_C. Field dependences of magnetostriction in parallel and perpendicular directions of applied magnetic field were obtained by direct measurement method. Subsequently, saturation magnetostriction and volume magnetostriction as well as forced magnetostriction were computed. Saturation magnetostriction increases with increasing Co/Fe ratio from 0 up to 17 ppm, depending both on the Co/Fe ratio and on the shift of T_C with composition. The alloy with ratio Co/Fe = 0 exhibits T_C near room temperature, thus field dependences of magnetostriction, corresponding to the dependences of a paramagnetic system are practically linear functions of applied field, corresponding to paramagnetic state.
2
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Influence of V and Cr Substitutions on Magnetic Properties of FeCoNbB Hitperms

88%
Butvinová B., Butvin P., Švec P., Vlasák G., Janičkovič D.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
111-114
EN
FeCoNbB Hitperm, where 4 at% of Fe are substituted by V or Cr show expected reduction of saturation, slightly lowered magnetostriction and slightly higher coercivity. Despite of significantly larger grain caused by Cr, the coercivity does not increase sharply. Detrimental ambient influences at non-vacuum annealing are not appreciably blocked by V or Cr.
3
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Magnetoimpedance Effect in Field Annealed (FeNi)_{78}Nb_{7}B_{15} Amorphous and Nanocrystalline Bilayer Ribbons

76%
Varga M., Marcin J., Capik M., Janičkovič D., Švec P., Škorvánek I.
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vol. 126
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issue 1
122-123
EN
The influence of the magnetic field annealing on the magnetoimpedance effect has been investigated in rapidly quenched (Fe_{0.5}Ni_{0.5})_{78}Nb_{7}B_{15} monolayer and bilayer thin ribbons. The highest impedance ratio value (ΔZ/Z)_{max}=72% and the maximum field sensitivity η_{max}=12 %/Oe was obtained in the bilayer ribbon, annealed under longitudinal magnetic field at 773 K that exhibited nanocrystalline structure. The higher values of (ΔZ/Z)_{max} in bilayer ribbons, as compared to their monolayer counterparts, are attributed to the increased ratio of their thickness to the penetration depth.
4
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Co_2FeSi Heusler Alloy Prepared by Arc Melting and Planar Flow Casting Methods: Microstructure and Magnetism

76%
Titov A., Životský O., Hendrych A., Janičkovič D., Buršík J., Jirásková Y.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
654-656
EN
This paper is devoted to studies of the structural and magnetic properties of Co_2FeSi Heusler alloy produced by arc melting resulting in samples with large grains compared to finer-grained ribbon type samples prepared by planar flow casting. The scanning electron microscopy completed by energy dispersive X-ray spectroscopy, X-ray diffraction, and magnetic methods sensitive to both bulk and surface were applied. The chemical composition inside the grains was found to be in agreement with the nominal one while at the grain boundaries enrichment on Co and Si at expense of Fe was observed. The magnetic parameters derived from the bulk hysteresis curves resulted in nearly the same values of coercivity, about 1 kA/m, for both technological procedures while magnetization was of about 15 A m²/kg higher at ribbons compared with sample prepared by arc melting, 145 A m²/kg. The surface magnetic characteristics were visibly influenced by a surface magnetic anisotropy. The smooth polished surface of the sample prepared by arc melting has allowed visualizing the magnetic domain structure inside the grains and at grain boundaries by the magneto-optical Kerr microscopy and magnetic force microscopy.
5
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Temperature Behaviour of Hyperfine Magnetic Fields in a Fe-Co-Si-B-Mo-P Metallic Glass Followed with ⁵⁷Fe Mössbauer Spectrometry

76%
Cesnek M., Miglierini M., Kmječ T., Kohout T., Amini N., Janičkovič D., Matúš P.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
744-746
EN
Amorphous glass with nominal chemical composition Fe₅₁Co₁₂Si₁₆B₈Mo₅P₈ was studied by combination of the Mössbauer spectroscopy and magnetic measurements in order to characterize magnetic and structural features. Temperature evolution of the Mössbauer spectra revealed presence of broad distribution of hyperfine magnetic field at lower temperatures which vanishes with increase of temperature. The Curie temperature estimated from the Mössbauer spectroscopy experiments is T_{C} ≈ 392 K. This value is in a good agreement with that obtained by magnetic measurements (T_{C}=397 K). The Mössbauer spectroscopy spectra of the sample annealed at 823 K revealed a presence of crystalline components. This temperature is notably lower than the expected temperature of the onset of crystallization observed by differential scanning calorimetry ( ≈ 835 K).
6
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Structure and Properties of Soft-Magnetic Amorphous Bilayer Ribbons

64%
Švec P., Mat'ko I., Marcin J., Kováč J., Vlasák G., Janičkovič D., Škorvánek I., Švec P.
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issue 5
832-834
EN
Rapidly quenched bilayers consisting of Fe-Si-B and Co-Si-B layers have been prepared by planar flow casting from a single crucible with two nozzles. Temperature dependences of electrical resistivity, dilatation and magnetization have been investigated in the amorphous state and during crystallization of both layers. Preliminary studies of the structure of the layers and of the interlayer have been performed by X-ray diffraction, cross-sectional electron microscopy and microanalysis. From the results it seems evident that the process of connection of the two layers during preparation takes place by solidification with only a small extent of mutual interdiffusion of component atoms localized to a narrow well-defined interface, leading to mechanically solid connection between the two layers. The effect of combined presence of two different soft magnetic alloys on the overall magnetic properties is discussed with respect to potential applications of such materials.
7
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Ellipsometric Selective Sensitivity to Magnetic Nanostructures

64%
Hamrlová J., Postava K., Životský O., Hrabovský D., Pištora J., Švec P., Janičkovič D., Maziewski A.
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issue 5
837-839
EN
Recently, we have shown that the approach of depth sensitivity of magneto-optic ellipsometry can be generalized to selectivity from different materials in nanostructures. We use the condition number as the figure of merit to quantify the magneto-optic selectivity to two different magnetic contributions in magnetic nanostructure. The method is demonstrated on nanostructures containing magnetically hard Fe particles in surface layer of soft FeNbB amorphous ribbon. We separated both magnetic contributions from measurement of hysteresis loops using magneto-optic Kerr effect in longitudinal configuration. Magneto-optic selectivity is discussed and theoretical model on the basis of effective medium is compared with experimental data of longitudinal magneto-optic Kerr effect depending on angle of incidence.
8
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Effect of Temperature on Magnetization Processes in Amorphous Rapidly Solidified FeSiB/CoSiB Bilayer Ribbons

64%
Capik M., Švec P., Marcin J., Kováč J., Sopko M., Janičkovič D., Švec P., Škorvánek I.
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vol. 126
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issue 1
120-121
EN
Amorphous bilayers consisting of Fe-Si-B and Co-Si-B layers have been prepared by planar flow casting from a single crucible using a double-nozzle technique. Temperature dependencies of magnetization and hysteresis loops have been investigated in a wide temperature range. At room temperature, the effects of interlayer stresses, induced in material due to different thermal expansion coefficients of two mechanically interconnected soft magnetic layers, resulted in rounded hysteresis loops with flattened central part, indicating a dominant role of magnetization rotational processes. With an increase of measurement temperature, the interlayer stresses are relieved and the hysteresis loops became more squared.
9
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Accents in Modern High Saturation Nanocrystalline Fe-Rich Alloys

64%
Butvinová B., Butvin P., Maťko I., Janičkovič D., Kuzminski M., Ślawska-Waniewska A., Švec P., Chromčíková M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
711-713
EN
Post processing limits for iron-rich Fe-Cu-Si-B-P high-induction rapidly-quenched ribbons have been tested. 530°C/20 min is already too much, formed borides being the essential culprit of magnetic properties deterioration. Unlike standard Si-poor Fe-Nb-Cu-B-Si Finemets, these alloys annealed even in "technical" Ar below the upper limit do not create significant squeezing surfaces.
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