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  1. 37 Acta Physica Polonica A

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  1. 10 Varga R.

  2. 7 Zhukov A.

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1
Content available remote

Imaging the Surface Domain Structure of Amorphous Glass-Coated Microwires by Bitter Colloid

100%
Richter K., Varga R., Thiaville A.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
72-73
EN
The fast domain wall dynamics of amorphous glass-coated microwires can be changed drastically by properly selected annealing temperature. Here, the effect of thermal annealing on the surface domain structure of microwires is examined. Imaging the surface domain structure by Bitter colloid revealed the periodic pattern in each studied sample. Thermal annealing of microwires results in the five times increase of the domain wall velocity, as compared to the as-cast state. Influence of the surface domain structure on the fast domain wall propagation in microwires is discussed.
2
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Domain Wall Dynamics in Amorphous Microwires

100%
Richter K., Kostyk Y., Varga R., Zhukov A., Larin V.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
7-10
EN
Here we present the domain wall dynamics in FeNi-based microwires with positive magnetostriction. Two different ranges were found which differs by the measured domain wall mobility. At low fields, the domain wall dynamics exhibit small mobility, whereas at higher field the domain wall mobility increases. The difference in the two regimes of the domain wall dynamics is treated in terms of the different domain wall structure. At low fields, the transversal domain wall is expected, with low domain wall mobility. At high field, the vortex-type domain wall with high domain wall mobility is created.
3
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Susceptibility Spectroscopy in FeNiSiB Microwires

100%
Olivera J., Gamcova J., Varga R., Santos J., Prida V., Sanchez M., Hernando B., Zhukov A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
155-158
EN
Here, we present the study on the influence of the Ni content on the magnetization processes of the amorphous glass-coated Fe_{77.5-x}Ni_xSi_{7.5}B_{15} (x = 0-40) microwires. Measurement of the amplitude dependence of the complex susceptibility was used to observe the magnetization process. It is shown that the magnetization process in the presented samples runs mainly through the domain wall motion.
4
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Fast Magnetization Switching in Amorphous Microwires

100%
Zhukov A., Ipatov M., Blanco J., Chizhik A., Talaat A., Zhukova V.
Acta Physica Polonica A
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2014
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vol. 126
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issue 1
7-11
EN
We studied the magnetization switching in magnetically bistable amorphous ferromagnetic microwires. We observed quite fast domain wall propagation along the microwires and a correlation between the magnetoelastic anisotropy, distribution of the local nucleation field along the length of microwire and the domain wall dynamics. We observed that both DW velocity and the range of fields, limiting single DW dynamics, can be manipulated by internal or applied stresses and by annealing. We also observed that under certain conditions a controllable domain wall (DW) collision can be realized in different parts of the wire, and that it is possible to manipulate the DW dynamics in a field-driven regime.
5
Content available remote

Negative Mobility of Single Domain Wall in Magnetic Microwires

100%
Varga R., Richter K., Zhukov A.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
747-748
EN
Here, we present the domain wall dynamics in thin magnetic wires that exhibit even negative mobility regime. Such a regime is well below the Walker limit and is a result of structural relaxation. It disappears at high frequencies and it can be enhanced by application of mechanical stress. Moreover, the domain wall velocity was found to be almost field-independent at certain measuring conditions. Anyway, the domain wall velocity remains quite high (> 450 m/s) in this regime.
6
Content available remote

Engineering of Magnetic Properties of Magnetic Microwires

100%
Zhukov A., Ipatov M., Blanco J., Corte-León P., Olivera J., Gonzalez J., Zhukova V.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
321-328
EN
We present an overview of the factors affecting soft magnetic properties, fast domain wall propagation and giant magnetoimpedance (GMI) effect in thin amorphous wires. The magnetoelastic anisotropy is one of the most important parameters that determine the magnetic properties of glass-coated microwires and therefore annealing can be very effective for manipulation the magnetic properties of amorphous ferromagnetic glass-coated microwires. Increasing of DW velocity in Fe-rich and Fe-Ni based (low Ni content) microwires is achieved after annealing. After heat treatment of Co-rich microwires we can observe transformation of inclined hysteresis loops to rectangular and coexistence of fast magnetization switching and GMI effect in the same sample. On the other hand stress annealing of Fe- and Co-rich microwires allows achievement of considerable magnetic softening and GMI effect enhancement.
7
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Novel Applications of Bistable Magnetic Microwires

100%
Sabol R., Klein P., Ryba T., Hvizdos L., Varga R., Rovnak M., Sulla I., Mudronova D., Galik J., Polacek I., Zivcak J., Hudak R.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
1150-1152
EN
Few examples of technical and biomedical applications of bistable magnetic microwires are shown. Particularly, application of microwires in civil engineering are shown for sensing the mechanical stress in concrete, steel structure or steel cable by simple gluing it on the surface of studied structure. On the other hand, biomedical applications for sensing the stress, temperature, and position inside the human or animal body are shown. Experiments with pig intestine cells points to the biocompatibility of glass coated microwires.
8
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Influence of Thermal Treatment on Domain Wall Dynamics in Glass-Coated Microwires

100%
Richter K., Varga R., Zhukov A.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
738-739
EN
We have studied the effect of thermal treatment on amorphous glass-coated Fe_{40}Si_{7.5}B_{15} microwires. This microwire is characterized by transverse domain wall regime only, with maximum domain wall velocity of about 1500 m/s. Annealing at 200°C slightly increases its transverse domain wall velocity, probably due to the reduction of mechanical stresses during the thermal annealing. Annealing at 300°C leads to drastical increase of domain wall mobility and domain wall velocity of the transverse domain wall up to 2500 m/s. Moreover, vortex regime appears in this case. Thanks to it, maximum domain wall velocity of around 5000 m/s was observed.
9
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Influence of Pulse Heating on Rayleigh Area of Amorphous FINEMET-Type Alloy

80%
Novák L., Kováč J., Hubač L.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
753-755
EN
The effect of pulse annealing on magnetization processes in FINEMET-type alloy in weak magnetic fields (the Rayleigh area) is studied in this paper. Rapidly quenched FINEMET ribbon in the original amorphous state was chosen for the study. The significant differences in behavior of studied materials are ascribed to the differences in internal mechanical stresses, which bring about the changes in total magnetic anisotropy and consequently also changes in domain walls thickness.
10
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The Study of Magnetization Process in Amorphous FeNiSiB Microwires

80%
Gamcova J., Varga R., Hernando B., Zhukov A.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
807-808
EN
We have studied the magnetization process in amorphous Fe_{49.6}Ni_{27.9}Si_{7.5}B_{15} microwire. It was found that the hysteresis mechanism consists of two contributions: magnetoelastic and structural relaxation. It was shown that at low frequencies, the magnetization process is controlled mainly by the structural relaxation. At higher frequencies (above 50 Hz), the relaxation effect disappears and switching field is determined mainly by the magnetoelastic contribution. Moreover, the effect of thermal treatment at temperature 300°C has been studied. As-cast microwire is almost unsensible to the applied tensile stress since the applied stresses are lower than that induced during production. After annealing, the stresses relax and stress sensibility of microwires increases.
11
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Temperature Dependence of Magnetization Process in Bistable Amorphous and Nanocrystalline FeCoMoB Microwires

80%
Klein P., Varga R., Vazquez M.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
809-810
EN
We have studied the effect of thermal treatment on the magnetic properties of amorphous and nanocrystalline Fe_{40}Co_{38}Mo_4B_{18} microwires. The magnetization process was measured within the temperature interval from 80 to 425 K. Microwires shows complex temperature dependence of the switching field in amorphous state due to the presence of complex stress distribution induced during production. After nanocrystallization, the switching field depends linearly on the measuring temperature that makes such microwires ideal for sensing applications.
12
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Determination of Exchange and Rotatable Anisotropies in Co₂FeSi/IrMn Exchange Coupled Structures using Broadband Ferromagnetic Resonance

80%
Głowiński H., Schmidt M., Krysztofik A., Gościańska I., Dubowik J.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
531-533
EN
We determined exchange H_{ex} and rotatable H_{rot} anisotropy fields of multilayers that comprise 10 nm Co₂FeSi (CFS) layers exchange coupled to 20 nm IrMn layers by using ferromagnetic resonance with a vector network analyzer (VNA-FMR). The multilayer structures consist of IrMn/bottom (b)-CFS/IrMn/middle (m)-CFS/IrMn/top (t)-CFS/IrMn layers so that each CFS layer is surrounded by a pair of IrMn layers. In the structures, the exchange bias field propagates in such a way that H_{ex}^{t} > H_{ex}^{m} > H_{ex}^{b} for the top, middle, and bottom layer, respectively. FMR response measured along the exchange bias (EB) axis consist of only two absorptions related to the (b+m)- and (t)-CFS layers, respectively. Exchange and rotatable anisotropy determined independently from angular and dispersion measurements of the resonance fields are nearly the same. Rotatable anisotropy field scales with the exchange bias field in these complex structures.
13
Content available remote

Vortex State Suppression in a Hexagonal Array of Interacting Py Triangular Rings

80%
Spizzo F., Patrignani L., Bisero D., Vavassori P., Metlushko V.
Acta Physica Polonica A
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2013
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vol. 123
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issue 2
218-220
EN
We investigate the effect of magnetostatic interactions on the magnetization reversal process of equilateral triangular rings arranged on a hexagonal lattice. Inter-ring interactions originate as rings corners host domain-walls that produce an intense dipolar field; the effect of such interactions is studied by recording hysteresis loops for different magnetic field orientations. Rings magnetic configuration is probed via magnetic force microscopy and diffraction magneto-optic Kerr effect measurements. We observe that the effect of stray fields due to domain-walls competes with that of shape anisotropy, and that the former prevails when the magnetic field orientation is parallel to rings symmetry axes.
14
Content available remote

Domain Wall Dynamics in Amorphous Ferromagnetic Wire with Small Helical Anisotropy

80%
Ziman J., Kladivová M., Onufer J., Zagyi B.
Acta Physica Polonica A
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2010
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vol. 118
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issue 5
778-779
EN
Dynamics of the domain wall between circular magnetic domains in amorphous ferromagnetic Co_{68.2}Fe_{4.3}Si_{12.5}B_{15} wire was studied in a small region around the domain wall equilibrium position in an inhomogeneous magnetic field. The wire was prepared using the in-rotating-water-quenching technique. Small helical anisotropy was induced in the wire by current annealing and simultaneous application of tensile stress and torsion. The inhomogeneous magnetic field acted on domain wall by restoring force directly proportional to the displacement of the domain wall from its equilibrium position. Domain wall position was monitored by circular magnetic flux measurements from which it results that domain wall motion can be modeled by the motion of a very strongly damped pendulum. The value of domain wall mobility obtained from these experiments is in good agreement with the values calculated and measured for domain wall driven by a constant magnetic field.
15
Content available remote

DC Magnetic Properties and Complex Permeability of Ni-Fe Based Composites

80%
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.
16
Content available remote

Temperature Dependence of the Switching Field in Nanocrystalline FeNiMoB Microwires

80%
Klein P., Varga R., Vazquez M.
Acta Physica Polonica A
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2014
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vol. 126
|
issue 1
64-65
EN
We have studied temperature dependencies of the switching field in as-cast and nanocrystalline glass-coated Fe_{40}Ni_{38}Mo_{4}B_{18} microwires. The switching field shows complex temperature dependence in the as-cast state reflecting the complex stress distribution induced during annealing. The temperature dependence of the switching field depends strongly on the stage of nanocrystallization being negative for low temperatures of annealing and positive for annealing at 700 K.
17
Content available remote

Exchange Bias Effect in NdFeO₃ System of Nanoparticles

80%
Vavra M., Zentková M., Mihalik M., Mihalik Jr. M., Lazúrová J., Girman V., Perovic M., Kusigerski V., Roupcova P., Jaglicic Z.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
869-871
EN
We study the effect of nanometric size on the crystal structure, magnetic environment of iron and magnetization in NdFeO₃ system of nanoparticles. The average particle size of NdFeO₃ nanoparticles increases with annealing at 600°C from about 15 nm to 40 nm. The smallest particles on annealed sample have size approximately 30 nm and typically have character of single crystalline samples. All samples adopt orthorhombic crystal structure, space group Pnma with lattice parameters a =5.5817 Å, b=7.7663 Å and c =5.456 Å for as prepared sample. The presence of superparamagnetic particles was indicated by the Mössbauer measurements. The reduction of dimensionality induces a decrease of T_{N1} from 691 K to 544 K. The shift of magnetic hysteresis loop in vertical and horizontal direction was observed at low temperatures after cooling in magnetic field. We attribute such behaviour to exchange bias effect and discuss in the frame of core-shell model.
18
Content available remote

Micromagnetic Approach to Exchange Bias

80%
Dubowik J., Gościańska I.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
147-152
EN
We present a micromagnetic approach to the exchange bias in ferromagnetic/antiferromagnetic thin film systems with a small number of irreversible interfacial magnetic moments. We express the exchange bias field H_{EB} in terms of the fundamental micromagnetic length scale of ferromagnetic - the exchange length l_{ex}. The benefit from this approach is a better separation of the factor related to the ferromagnetic layer from the factor related to the ferromagnetic/antiferromagnetic coupling at interfaces. Using this approach we estimate the upper limit of H_{EB} in real ferromagnetic/antiferromagnetic systems.
19
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Micromagnetic Structures near a Second Order Phase Transition in Monocrystalline Ferrite Garnet Plates

80%
Pamyatnykh L., Belskii I., Shmatov G.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
421-423
EN
The main parameters of micromagnetic structure formation in a vicinity of a second order phase transition were determined experimentally and theoretically. The theoretical study was performed using micromagnetic approach. External magnetic field H_{c} of appearance of micromagnetic structure and micromagnetic structure period L_{c} were determined for (001)-oriented plate with uniaxial K_{u} and cubic K₁ magnetic anisotropy. The plate was saturated by the field applied in its plane. In the model we assumed that magnetization vector undergoes small deviations from equilibrium if magnetic field is slightly reduced. These deviations are periodic in nature: micromagnetic structure has a form of a plane wave. Dependences of H_{c} and L_{c} on an azimuthal angle of external magnetic field and on anisotropy constants K_{u} and K₁ were derived analytically in this work. Experimental studies of micromagnetic structure near the second order phase transition were conducted on (EuEr)₃(FeGa)₅O₁₂ (001)-oriented 50 μm thick ferrite-garnet plate with K_{u} = 5700 erg/cm³ and K₁=-3700 erg/cm³. Micromagnetic structure was revealed by means of magnetooptic Faraday effect. The in-plane field was increased up to 2000 Oe. Experimentally determined values of H_{c} and L_{c} were compared with theoretical estimates.
20
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Modeling the Hysteresis Loop of the Nanocomposite Material Using Modified Hyperbolic T(x) Model

80%
Dośpiał M.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
415-417
EN
The paper presents possibilities of hysteresis loop decomposition onto the magnetization components. The reversible and irreversible magnetization changes describe processes, which are influencing reversal magnetization in studied permanent magnets. Further, these components are used for modelling the recoil curves using modified hyperbolic T(x) model.
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