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1
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Structure and Magnetic Properties of Three-Dimensional Gadolinium-Based Hybrid Framework

100%
Almáši M., Zeleňáková A., Císařová I., Bednarčík J., Zeleňák V.
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vol. 126
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issue 1
308-309
EN
In the present work we have focused on the preparation and magnetic study of coordination polymer formed by Gd(III) cations as nodes and formate (HCOO¯; FOR) anions as charge compensating linkers. The prepared complex with formula {[Gd(μ_{3}-FOR)_{3}]}_{n} was characterized by single-crystal X-ray diffraction, and high-energy powder X-ray diffraction. The structural study showed that complex is formed by 3D polymeric network with the shortest Gd-Gd, distances of 3.998 Å. The magnetic properties of the complex were studied by magnetic susceptibility χ_{M}(T) and magnetization M(H) measurements. The results show on the weak antiferromagnetic coupling at low temperatures represented by the Weiss constant θ=-0.468 K. The value of effective magnetic moment μ_{eff}=7.57μ_{B}, which was estimated from the experimental data is close to the theoretical value for systems with S=7/2. Correlation between crystal structure of complexes and magnetic properties is presented.
2
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Isobaric Thermal Expansion and Isothermal Compression of Powdered NiFe Based Alloys Studied by In-Situ EDXRD

100%
Olekšáková D., Füzer J., Kollár P., Bednarčík J., Lathe C.
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vol. 126
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issue 1
128-129
EN
The aim of the present work was to study the isothermal compression and isobaric thermal expansion behaviour of ball-milled NiFe (81 wt.% of Ni) and NiFeMo (79 wt.% of Ni, 16 wt.% of Fe) alloy and follow its phase evolution when exposed to high pressure and temperature. In-situ pressure-temperature energy dispersive X-ray (EDXRD) diffraction experiments were performed at the MAX80 instrument (beamline F2.1). The compressibility of NiFe alloy at 400 °C was evaluated for pressure values of up to 3.5 GPa. The EDXRD spectra revealed the presence of cubic FeNi_{3} phase as determined from the shift of (111), (200) and (220) reflection lines in corresponding EDXRD spectra.
3
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Magnetic Properties of Crystalline NiFe Alloy Prepared by High-Energy Ball Milling and Compacting

100%
Olekšáková D., Kollár P., Füzer J., Bednarčík J., Roth S.
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issue 5
797-799
EN
The structure and magnetic properties of compacted microcrystalline NiFe (81 wt% of Ni) powder is investigated. The powder of NiFe alloy prepared by ball milling of ribbon (prepared by melt spinning) remains single phase material suitable for compaction in order to prepare soft magnetic material. The bulk samples were consolidated by uniaxial compaction of the powder in vacuum. By measuring of AC and DC magnetic properties it was found out that in bulk samples the displacement of domain walls is the dominant magnetization process, while rotation of magnetization vectors prevails in powder material.
4
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Magnetic Properties of Fe@Pt Nanoparticles with Core/Shell Morphology

100%
Zeleňáková A., Zeleňák V., Bednarčík J., Lauda M., Kováč J.
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issue 5
1002-1004
EN
We have investigated the magnetic properties of iron nanoparticles coated by platinum shell prepared by chemical procedure. Magnetic measurements using SQUID magnetometer confirm the behaviour typical for a superparamagnetic system. From the M(H) loop at 300 K the magnetic moment of each particle m_{P} ≈ 250 μ_{B} was calculated. The magnetic relaxation study by the in-phase χ' and out-of-phase χ" ac susceptibilities in frequency range 0.1-1000 Hz suggests the existence of two magnetic layers with different magnetic spin's dynamics and strong dipolar interactions between nanoparticles. The observed magnetic behaviour is caused by the blocking process of interacting superparamagnetic particles with magnetic iron core, diamagnetic platinum shell and spin-glass like behaviour magnetic interlayer between them.
5
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The Soft Magnetic Properties and Temperature Stability of Co-Fe-Zr-B Metallic Glasses

86%
Bednarčík J., Kováč J., Roth S., Fűzer J., Kollár P., Varga L., Franz H.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
83-86
EN
In the present work multicomponent Co-based alloys with nominal composition Co_{72-x}Fe_xZr_8B_{20} (x=10, 15, and 20 at. %) were synthesized by single-roller melt-spinning. The measurement of coercivity, H_c, reveals the soft magnetic behavior of investigated alloys. The value of H_c increases from 23 A/m for alloy with x=10 at. % up to 32 A/m for alloy with x=20 at. %. Further it was found that crystallization temperature of as-quenched alloys slightly varies with iron content and lays between 605 and 625°C. From the temperature dependence of magnetization it follows that partial substitution of cobalt by iron has positive influence on the Curie temperature of amorphous phase, T^{am}_c, which increases from 300°C up to 462°C for alloy with x=10 at. % and x=2 0 at. %, respectively.
6
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In Situ Energy Dispersive X-Ray Diffraction Analysis of the Temperature-Pressure Stability of Co-Fe-(Ta,W)-B Alloys

86%
Kanász R., Bednarčík J., Saksl K., Nicula R., Stir M., Lathe C.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
79-82
EN
In this work two Co_{53.5}Fe_{10}X_{5.5}B_{31} (X = Ta, W) alloys were synthesized from high purity (≥99.9%) powder elements by means of mechanical alloying. In case of Ta-addition, mechanical alloying resulted in formation of two component material with nanocrystalline phase embedded in amorphous matrix. On the other hand, substitution of Ta by W retards partial amorphization induced by mechanical alloying. High pressure-temperature stability of both alloys was monitored using in situ energy dispersive X-rays.
7
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Investigation of Mixed Valence State of Sm_{1-x}B_{6} and Sm_{1-x}La_{x}B_{6} by XANES

86%
Gabáni S., Flachbart K., Bednarčík J., Welter E., Filipov V., Shitsevalova N.
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vol. 126
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issue 1
338-339
EN
We investigated the valence states of samarium ions in Sm deficient Sm_{1-x}B_{6} (x=0.03, 0.05, 0.08, 0.1 and 0.2) sintered samples, in single crystalline solid solutions Sm_{1-x}La_{x}B_{6} (x=0.16, 0.28, 0.4, 0.55 and 0.7) as well as in a SmB_{6} single crystal by X-ray absorption near edge structure (XANES) between 4.2 and 300 K. It was shown that the mixed valence state v_{Sm} of Sm-ions (v_{Sm} ≈ 2.51 for SmB_{6} at 4.2 K) in deficient samples is changed but maintained up to a concentration of 20% of vacancies and up to a concentration of 70% in samples doped with trivalent La-ions, and that in both cases it increases with temperature. On the other hand, the value of v_{Sm} increases with increasing vacancy level, whereas it decreases with increasing La^{3+} substitution. The obtained dependences of Sm-valence in SmB_{6} on vacancy as well as on La^{3+} ion concentration are in good agreement with susceptibility measurements and exact numerical calculation of the spinless Falicov-Kimball model in two dimensions.
8
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Effect of Annealing Time on Structure of Fe_{72.5}Cu_{1}Nb_{2}Mo_{2}Si_{15.5}B_{7} Alloy

86%
Nemcová V., Girman V., Hrabčáková V., Michalik Š., Bednarčík J., Almáši M., Sovák P.
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vol. 126
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issue 1
116-117
EN
The process of a primary crystallization of the Fe_{72.5}Cu_{1}Nb_{2}Mo_{2}Si_{15.5}B_{7} alloys was investigated by differential thermal analysis (DTA), x-ray diffraction (XRD) and transmission electron microscopy (TEM). Amorphous ribbons were isothermally annealed for 0.5, 2, 6, 30 and 150 minutes at 520 °C. Both, the XRD and TEM study showed that the level of devitrification of the sample increases with the annealing time. The above mentioned techniques confirmed the presence of the nanocrystalline grains of the Fe_{3}Si phase and enable us to study the evolution of the identified phase.
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