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Dive into the research topics where B. Butvinová is active.

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Featured researches published by B. Butvinová.


Journal of Magnetism and Magnetic Materials | 2000

Magnetic response of FeNbCuBSi RQ ribbons to bi-axial strain

Pavol Butvin; B. Butvinová; Z Frait; Jozef Sitek; P. Švec

Abstract Nanocrystalline strip samples of the FeNbCuBSi class that are macroscopically heterogeneous due to surface /volume differences have been investigated. This heterogeneity is found to be a general property of the class. It represents a base for mutual force influence between the surface and the majority volume beneath. The bi-axial in-plane stress exerted by the ribbon surfaces on the volume is demonstrated first of all by a magnetoelastic anisotropy. The contribution of the creep-induced anisotropy, which can build up under the surface stress at post-treatment temperature, is also found possible.


Sensors and Actuators A-physical | 2003

Influence of heterogeneity on magnetic response of nanocrystalline ribbons

B. Butvinová; Pavol Butvin; Rudolf Schäfer

FeNbCuBSi nanocrystalline ribbons are known to show heterogeneities influencing their magnetic properties. To search for a heterogeneity-specific response, the incremental permeability μΔ method was used and domain structure observations served related arguments. Such a response can be found in the hysteresis shown by a plateau observed in the μΔ field variation. Domain structure observation confirmed the existence of an off-plane anisotropy due to the heterogeneity as well as the participation of wall movement when μΔ shows the plateau. Nanocrystalline ribbons, being two-phase materials, show different macroscopic heterogeneity (MH) if compared to a metallic glass.


Sensors and Actuators A-physical | 2003

A relax type wide range field sensor using Finemet

Pavol Butvin; D Praslička; J Blažek; B. Butvinová

The task to extend the range and dynamic resolution of a proven digital magnetic field sensor is solved. The specific sensor-type requirements are followed when selecting the suitable material from among nanocrystalline ribbons of the FeNbCuBSi Finemet family. The materials are tested by measuring the hysteresis loops, the longitudinal incremental permeability and by the domain structure observation. The macroscopic heterogeneity and the magnetostriction of the ribbons show to be the key issues. Laboratory and field tests show that the best choice is the low-magnetostrictive nanocrystalline Finemet containing 16 at.% Si. The dynamic resolution attains 100 dB, the basic range of the sensor increases by 50% to 120 μT and higher service temperature is enabled if compared to the use of a Co-based metallic glass.


IEEE Transactions on Magnetics | 2012

Indication of Intrinsic Macroscopic Forces Affecting Magnetic Properties of Fe-Nb/Mo-Cu-B-Si Ribbons

B. Butvinová; Pavol Butvin; Marek Kuzminski; Magdaléna Kadlečíková; Anna Slawska-Waniewska

Si-rich (at.% Si >; 12) Fe-Nb/Mo-Cu-B-Si nanocrystalline ribbons are already successfully used in industry. Still the impact of intrinsic macroscopic stresses on magnetic anisotropy is not known in enough detail. Domain structure, hysteresis loops and surface chemistry have been studied in the as-annealed (nanocrystalline) state as well as the response to surface removal by etching. Creep-induced anisotropy established during annealing was found to be the essential source of the observed anisotropy. Apparently smooth gradient of transversal to longitudinal creep-induced anisotropy was identified from air-side center across the ribbon width as well as across the ribbon thickness. The relative rise of transversal anisotropy due to surface removal points to different surface etching efficiency. Raman spectroscopy confirmed the presence of ferrous oxides on both the ribbon surfaces. The existence of a defined oxide layer generating the macroscopic stress was not indicated.


Journal of Magnetism and Magnetic Materials | 1992

As-cast anisotropy of amorphous CoFeCrBSi and FeNbCuSiB

Pavol Butvin; M. Hlásnik; P. Duhaj; B. Butvinová; K. Závĕta; L. Kraus; K. Jurek

Abstract The anelastic polarization (AP) is recognized as the principal source of features common to many rapidly quenched metallic ribbons. To elucidate the role of nonuniform as-cast AP in the behaviour of two rather different magnetic materials, a simple idea is proposed. It assumes and the experiments point to, the presence of AP compressive strain accompanying the obvious tensile one.


Chemical Papers | 2017

Differentiation of selected blue writing inks by surface-enhanced Raman spectroscopy

L’ubomír Vančo; Magdaléna Kadlečíková; Juraj Breza; Pavol Michniak; Michal Čeppan; Milena Reháková; Eva Belányiová; B. Butvinová

Raman spectroscopy and surface enhanced Raman spectroscopy were used to examine 14 blue inks obtained from commercially available stationery. Standard colouring agents in the inks: β-phase of phtalocyanine blue PB15 and some homologues of the methyl violet class, were identified. Surface enhanced Raman spectra were recorded on a firm heterostructure of silver/nanocrystalline diamond/silicon constituting an active substrate providing the possibility to write directly on the surface. Based on the differences in traditional and surface enhanced Raman spectra, two inks were identified unambiguously, the remaining inks were categorised into three groups exhibiting common spectral features. Despite their similarity, surface enhanced Raman spectra exhibited soft variations enabling discrimination of the inks, thus proving the usefulness of the method.


IEEE Transactions on Magnetics | 2014

Magnetic and Surface Properties of High-Induction Nanocrystalline Fe-Nb-Cu-B/P-Si Ribbons

B. Butvinová; Pavol Butvin; Igor Matko; P. Švec; Maria Chromcikova; Jozef Sitek; Július Dekan

High-induction Si-poor Fe-Nb-Cu-B-Si Finemet ribbons annealed in inert gas ambience are known to build oxides and prefer surface crystallization. Phosphorus-3 at% of P instead of B was substituted to see how it can influence these surface effects. The off-axis magnetic anisotropy caused by surfaces squeezing the ribbon interior was reduced and it was found out that the major source of the squeeze is the surface crystallization and not the oxides. Phosphorus appears to hamper preferentially the surface crystallization. The substitution also improves the magnetic softness of vacuum-annealed ribbons by grain size reduction. Slight reduction of saturation induction is a minor sacrifice to the improvements.


Materials Science and Engineering A-structural Materials Properties Microstructure and Processing | 1997

Distinctive annealing behaviour of Si-poor FeNbCuBSi alloys

Pavol Butvin; B. Butvinová; P. Duhaj; Gabriel Vlasák; P. Švec; D. Janičkovič

Abstract Unlike more Si-rich FeNb 3 Cu 1 B y − x Si x (where y = 18–22.5) alloys, for x ⩽ 10 at.% the building of hard-ribbon-axis magnetic anisotropy is observed after isothermal annealing of toroids at about 540 °C. The hysteresis loops increase their tilting with annealing time while the sense of the variation crosses over after a period depending on the Si contents. Primary increase of a.c. initial permeability is reverted after a short annealing period. Tiny ( d ⩽ 20 nm) α-Fe(Si) crystalline grains are formed in the initial stages of crystallization; their volume share is about 50% after 30 min annealing. Using transmission electron microscopy (TEM), it has been observed that after continued annealing a new crystalline phase is formed on the boundaries of the α-Fe(Si) grains. X-ray diffraction then shows extra reflections, indicating the presence of Fe borides. Several effects that could give rise to the observed behaviour are discussed.


IEEE Transactions on Magnetics | 1994

Using metallic glasses for choke cores

Pavol Butvin; B. Butvinová; J. Novak

The paper reviews major topics which concern the design of most common choke types from the point of view of materials research. Measurements of permeability (/spl mu/) frequency- and field-dependence as well as measurements on model chokes prove advantageous properties of metallic glasses. Preference of rotational processes in core magnetization is pointed out. Limitations in the use of high /spl mu/, of higher induction and in the feasibility of core-dimensions reduction are analysed too. >


Journal of Magnetism and Magnetic Materials | 2000

Susceptibility and its disaccommodation in nanocrystalline FeNb-based materials

B. Butvinová; Pavol Butvin; V. Ocelı́k

Disaccommodation of permeability and/or susceptibility (DAS) on toroidal and strip samples of diverse nanocrystalline FeNb-based materials is investigated. Usually low DAS is enhanced by low crystalline share. Strip samples are less advantageous than toroids; however, at strong and homogeneuous anisotropy, as the creep-induced one, the possibility to exploit DAS opens up.

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Pavol Butvin

Slovak Academy of Sciences

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P. Švec

Slovak Academy of Sciences

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Gabriel Vlasák

Slovak Academy of Sciences

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Marek Kuzminski

Polish Academy of Sciences

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D. Janičkovič

Slovak Academy of Sciences

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Jozef Sitek

Slovak University of Technology in Bratislava

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Magdaléna Kadlečíková

Slovak University of Technology in Bratislava

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Igor Maťko

Slovak Academy of Sciences

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P. Duhaj

Slovak Academy of Sciences

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