Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl

Refine search results

Journals help

  1. 54 Acta Physica Polonica A

  2. 1 Archives of Acoustics

Years help

  1. 6 2018

  2. 10 2017

  3. 4 2015

  4. 8 2014

  5. 9 2012

More...
Authors help

  1. 55 Timko M.

  2. 41 Kopčanský P.

  3. 16 Rajňák M.

  4. 14 Kováč J.

  5. 13 Koneracká M.

More...
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 55

Number of results on page
first rewind previous Page / 3 next fast forward last

Search results

help Sort By:

help Limit search:
first rewind previous Page / 3 next fast forward last
1
Content available remote

Thermoelectric Properties of CeCu_4Ag Compound

100%
Kowalczyk A., Toliński T., Falkowski M., Timko M.
|
|
issue 5
936-937
EN
The magnetic and electronic properties including electrical resistivity, thermal conductivity and thermopower are discussed for the heavy fermion CeCu_4Ag compound. The electrical resistivity shows a Kondo-like logarithmic increase up to a maximum at T = 75 K. Thermopower is positive over the whole temperature range and below T_max = 25 K falls rapidly. The measured thermal conductivity of the CeCu_4Ag compound increases with increasing temperature.
2
Content available remote

Study of Structural Changes of Water-Based Magnetic-Fluid by Acoustic Spectroscopy

88%
Kúdelčík J., Hardoň Š., Bury P., Timko M., Kopčanský P.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
919-921
EN
The effect of an external magnetic field on the changes in structural arrangement of magnetic nanoparticles in water based magnetic fluid was studied by acoustic spectroscopy. When a magnetic field is increased, the interaction between the magnetic field and the magnetic moments of nanoparticles leads to the orientation of magnetic nanoparticles and their following aggregation to long chains that cause the increase of acoustic attenuation. The attenuation of acoustic waves measured for jump changes of the magnetic field to 100, 200, and 300 mT at temperature 20°C showed that the changes of acoustic attenuation increased slowly to a stabilized state that after switching off the magnetic field decreased immediately to initial value. The dependence of attenuation of acoustic waves at constant magnetic field on angle between the wave vector and direction of the applied magnetic field (attenuation anisotropy) has been measured, too. The measured anisotropy of acoustic attenuation attested structural changes of magnetic fluid in the magnetic field.
3
Content available remote

The Effect of Polymer Immobilization on Magnetic Properties of Magnetosomes

88%
Timko M., Džarová A., Kovač J., Kopčanský P., Gojzewski H.
|
|
issue 5
995-997
EN
The anisotropy of several PVA/magnetosomes magnetically textured films has been investigated from the point of view of magnetic properties. The thin film synthesized under the influence of a magnetic field (99 mT) shows the typical behavior of an anisotropic material. On sample textured in magnetic field the magnetisation loop measurements were performed in dependence on the direction of the external magnetic field with respect to the texture axis. The results of hysteresis measurements show that the magnetic field applied during the synthesis promotes an orientation of the chains of magnetosomes and permanently textured film is obtained after solidification. The obtained values for magnetic remanence and coercivity were dependent on the external magnetic field orientation and the alignment effect of particle moments may be clearly seen which is in agreement with the theoretical model of magnetic particle chains.
4
Content available remote

Anisotropy of Susceptibility and Optical investigation of the Antiferromagnetic phase Transition in U_{1-x}Ce_{x}Ru_{2}Si_{2}

88%
Mihalik M., Maťaš S., Macko D., Timko M., Menovsky A. A.
Acta Physica Polonica A
|
1997
|
vol. 91
|
issue 2
351-354
EN
Temperature dependence of magnetic susceptibility of U_{1-x}Ce_{x}Ru _{2}Si_{2} single crystals (x=0, 0.025, 0.05, 0.075) has been studied at temperatures from 4.2 K up to room temperature and in magnetic fields applied along and perpendicular to the c-axis. The attention was paid to anomalies connected with the antiferromagnetic phase transition, which are present in crystals with x≤0.05. Far-infrared measurements of U_{0.99}Ce_{0.01} Ru_{2}Si_{2} single crystal have been studied for the first time. The measurements support the assumption that the origin of magnetic ordering in U_{0.99}Ce_{0.01}Ru_{2}Si_{2} is the same as in heavy-fermion superconductor URu_{2}Si_{2} and can be interpreted as being due to a spin-density-wave gap.
5
Content available remote

Valence Band and Core Levels of Ce_5Ni_2Si_3 Crystal Studied by X-ray Photoemission Spectroscopy

88%
Toliński T., Kowalczyk A., Chełkowska G., Mihalik M., Timko M.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
327-330
EN
The crystal of Ce_5Ni_2Si_3 was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value of the hybridization parameter of the f-states with the conduction electrons Δ=4 meV and the f-occupancy n_f close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of the Ce(4f) states are also visible close to the Fermi level.
6
Content available remote

Synthesis and Characterization of Magnetoferritin

88%
Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 5-6
1318-1320
EN
The paper presents detailed experimental study of synthesis and characterization a bioinorganic magnetic molecule - magnetoferritin. Magnetoferritin with loading of iron ions per protein molecule in the range from 300 to 3000 was prepared. Size distribution analysis (transmission electron microscopy, dynamic light scattering) shows spherical nanoparticles with particle size distribution from 2 to 12 nm, and hydrodynamic diameter from 12 to 25 nm. The thermomagnetic curves measured after cooling the sample in zero field (zero-field cooling) and under the presence of the measurement field (field cooling) show superparamagnetic behavior with the blocking temperature T_{b} from 22 to 60 K and the magnetization loops measured below T_{b} (at 2 K) show the hysteresis with coercive field from 20 to 30 kA/m depending on the concentration of the magnetic nanoparticles.
7
Content available remote

Study of Composites Consisting of High-T_{c} Superconductor and Fine Magnetic Particles

88%
Timko M., Kopčanský P., Kováč J., Koneracká M., Plecháček V.
Acta Physica Polonica A
|
2000
|
vol. 97
|
issue 3
389-392
EN
The composite systems as a mixture of fine magnetic particles of Fe_{3}O_{4} and superconducting powder such as Bi_{1.8}Pb_{0.2}Sr_{2}Ca_{2}Cu_{3}O_{10+x} were prepared. The influence of internal magnetic field (generated by magnetic particles) on the superconducting properties of prepared composites were studied as a function of concentration of magnetic particles and their magnetic state. The observed data both of the shielding and the Meissner effect were compared with corresponding linear combination of pure signals of magnetite and superconductor, respectively. The large differences were observed for demagnetized samples. It means that result must be discussed in the frame of the distribution of internal magnetic field created by the magnetic particles.
8
Content available remote

Influence of Temperature on the Magneto-Dielectrics Effect of Oil-Based Ferrofluid

88%
Kúdelčík J., Hardoň Š., Bury P., Timko M., Kopčanský P.
|
EN
The effect of temperature on the magneto-dielectrics behavior was studied by dielectric spectroscopy in the transformer oil-based ferrofluid with magnetic nanoparticles upon the effect of an external magnetic field. The frequency dependence of complex permittivity and dissipation factor were measured within the frequency range from 1 mHz to 10 kHz at different temperatures by a capacitance method. The dielectrics parameters were measured as a function of the external magnetic field in the range of 0-200 mT, parallel to the direction of the electric field as a function of temperature in the range of 15-35°C. The interaction between magnetic field and magnetic moments of nanoparticles led to the aggregation of magnetic nanoparticles to new structures which had influence on dielectric parameters. The dependence of these parameters at constant magnetic field on angle between the direction of the electric and magnetic fields (anisotropy) has been measured, too.
9
Content available remote

[FeCl_{4}]¯ Ionic Liquid Based Ferrofluids

88%
Parnica J., Kesa P., Kovac J., Timko M., Antalik M.
|
|
vol. 126
|
issue 1
276-277
EN
Magnetic ionic liquids derived from hydrochloride methyl ester alanine amino acids (AA) and FeCl_{3} were synthesized in ethanol and their magnetic properties were investigated. Iron (III) chloride forms ionic liquid in ethanol at saturated concentrations by the transfer of Cl¯ anion from one molecule of FeCl_{3} to the other molecule with the creation of tetrachloro ferrate anion [FeCl_{4}]¯ as well as dimer [Fe_{2}Cl_{7}]¯. Raman scattering indicates that after addition of hydrochloride methyl ester alanine to ethanol solutions of FeCl_{3} increase the intensities of signal at the frequencies at 318 cm^{-1} and 380 cm^{-1} as markers for the presence of [FeCl_{4}]¯ and [Fe_{2}Cl_{7}]¯ complexes. The magnetization at room temperature showed in both samples a linear dependence on the applied magnetic field. On the other hand, in the Raman scattering experiments the magnetization is smaller for FeCl_{3} sample in the presence of methyl ester alanine.
10
Content available remote

Dependence of Ultrasonic and Magnetic Hyperthermia on the Concentration of Magnetic Nanoparticles

76%
Kaczmarek K., Hornowski T., Bielas R., Żak D., Timko M., Józefczak A.
Acta Physica Polonica A
|
2018
|
vol. 133
|
issue 3
716-718
EN
Hyperthermia treatment is the heating of tumor tissue up to temperatures between 41°C and 45°C, which trigger several physiological reactions in the body. Hyperthermia within tissue can be applied through various mechanisms. One of them is magnetic hyperthermia which uses superparamagnetic iron oxide nanoparticles (SPIONs) heated by an externally applied magnetic field. SPIONs can also be used as sonosensitizers in ultrasound hyperthermia increasing acoustic wave attenuation. The impact of SPION concentration on thermal effect during ultrasonic and magnetic hyperthermia was investigated in agar-gel phantom with added magnetite nanoparticles. The presence of nanoparticles in the tissue-mimicking phantom increases the thermal losses of ultrasound energy and temperature of the phantom.
11
Content available remote

Electro-Rheological Properties of Transformer Oil-Based Magnetic Fluids

76%
Paulovičová K., Tóthová J., Rajňák M., Timko M., Kopčanský P., Lisý V.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
1141-1143
EN
The aim of this work was to study rheological behavior of nanofluids affected by electric field and temperature. We used transformer oil-based magnetic fluids, the suspensions of permanently magnetized colloidal particles (Fe_3O_4) coated by a stabilizing surfactant and immersed in transformer oil. The rheological characterization of transformer oil-based magnetic fluid was performed using the rotational rheometer MCR 502 in the shear rate from 10 to 1000 s¯¹.The strength of electric field was changed in the interval 0-6 kV cm¯¹. The flow curves and viscosity functions detected at three different temperatures 25, 50, and 75°C disclose rheological characteristics of samples, first of all the viscosity growth under increasing strength of electric field.
12
Content available remote

Temperature Dependence of a Dielectric Relaxation in Weakly Polar Ferrofluids

76%
Rajňák M., Kurimský J., Dolník B., Cimbala R., Paulovičová K., Kopčanský P., Timko M.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
943-945
EN
In this paper, we report on the temperature dependent broadband dielectric response of a ferrofluid based on transformer oil and magnetite nanoparticles covered with oleic acid molecules. For that purpose the method of dielectric spectroscopy has been chosen in the frequency range from 20 Hz up to 100 kHz. The experiments were carried out on thin film ferrofluid samples confined in a glass plate capacitor containing indium tin oxide (ITO) plate electrodes. The obtained complex permittivity spectrum shows a pronounced dielectric dispersion in the low frequency range. Taking into account the ferrofluid composition we associate this relaxation with ion impurity polarization at the nanoparticle-oil interface. The strong temperature dependence of the relaxation process has been found when conducting the experiments in the temperature range from 298 K to 358 K. The relaxation time of the revealed process exhibits a typical Arrhenius behavior. Based on the conducted experiments and analysis, we propose some reasonable practical applications of the studied ferrofluid in the field of electrical engineering.
13
Content available remote

Magnetic Birefringence Study of the Magnetic Core Structure of Ferritin

76%
Koralewski M., Pochylski M., Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
|
2012
|
vol. 121
|
issue 5-6
1237-1239
EN
Magnetically induced optical birefringence (Δ n) was measured for magnetoferritin and horse spleen ferritin aqueous suspensions. The Δ n for magnetoferritin was described in the frame of the Langevin formalism taking into account distribution of core diameter. The established average magnetic dipole moment and core diameter is equal to about 460 μ_{B} and 3 nm, respectively. It was shown that magnetic birefringence and the Cotton-Mouton constant can be powerful parameters in identification of the magnetic core structure of ferritin, especially useful in biomedicine.
14
Content available remote

The Structural Phase Transitions in 6CB-Based Ferronematics

76%
Tomašovičová N., Koneracká M., Kopčanský P., Timko M., Závišová V., Tomčo L., Jadżyn J.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
336-338
EN
The structural transitions in ferronematics based on the thermotropic nematic liquid crystal 4-cyano-4'-hexylbiphenyl were studied. The ferronematic samples were prepared by doping with magnetic suspension consisting of Fe_3O_4 particles (10 nm in diameter) coated with oleic acid as a surfactant with different volume concentrations of magnetic particles (from 10^{-5} to 10^{-3}). Freedericksz transitions were studied in combined electric and magnetic fields. The experimental results indicated soft anchoring with perpendicular initial orientation between the magnetic moment of the magnetic particles and director.
15
Content available remote

Magnetic Properties of Encapsulated Magnetite in PLGA Nanospheres

76%
Koneracká M., Závišová V., Timko M., Kopčanský P., Tomašovičová N., Csach K.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
595-598
EN
In this study, the biocompatible magnetic fluid was encapsulated in biodegradable polymer PLGA (poly D, L/lactide-co-glycolide acid) by the nanoprecipitation method. We characterized these spheres in terms of morphology, magnetite content and magnetic properties. The results showed good encapsulation with magnetite content 22wt% and magnetization 3.4 mT. The transmission electron microscopy and scanning electron microscopy images showed that magnetic particles have almost a spherical shape with approximate size 250 nm. Infrared spectroscopy and thermogravimetric analysis measurements were used to confirm incorporation of magnetic particles into the PLGA polymer.
16
Content available remote

Dielectric Properties of Magnetic Liquids in High Electric Fields

76%
Herchl F., Kopčanský P., Timko M., Koneracká M., Marton K., Kolcunová I., Tomčo L.
Acta Physica Polonica A
|
2008
|
vol. 113
|
issue 1
569-572
EN
In this work, dielectric properties of magnetic fluids composed of magnetite particles dispersed in transformer oil and subjected to a uniform magnetic field were investigated at the high alternating electric field intensities in the range of 0.5-2.5 MV/m. Dielectric stability of the magnetic fluid with the particle volume concentrationΦ= 0.0019 was observed. The magnetic fluid with the concentrationΦ= 0.019 showed the significant changes of permittivity and dielectric losses, too.
17
Content available remote

Structural Changes in Liquid Crystals Doped with Rod-Like Magnetic Particles Studied by Surface Acoustic Waves

76%
Bury P., Veveričík M., Kúdelčík J., Kopčanský P., Timko M., Závišová V.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 4
913-915
EN
The effect of rod-like magnetic particles on liquid crystal (6CHBT) structural changes in electric and weak magnetic fields were studied by means of the attenuation of surface acoustic wave of frequency 30 MHz propagating along ferronematic liquid crystals. Three low volume concentrations (Φ=1×10¯⁵, 1×10¯⁴ and 1×10¯³) of rod-like magnetic particles were added to liquid crystal during its isotropic phase. Several measurements including the investigation of the effects of electrical and magnetic fields applied both separately and in conjunction as well as the influence of temperature on the surface acoustic wave attenuation were performed. The distinctive surface acoustic wave attenuation responses induced by both electric and magnetic fields in studied ferronematic liquid crystals have been observed suggesting both structural changes and the orientational coupling between magnetic moments of magnetic particles and the director of the liquid crystal. Obtained results confirmed the significant influence of the presence of magnetic particles on the structural properties and resulting behavior of 6CHBT liquid crystal.
18
Content available remote

Magnetic Properties of Bacterial Nanoparticles

76%
Timko M., Džarová A., Kováč J., Kopčanský P., Gojzewski H., Szlaferek A.
Acta Physica Polonica A
|
2009
|
vol. 115
|
issue 1
381-383
EN
The objective of this study is to prepare and study magnetic properties of biological magnetic nanoparticles (magnetosomes) as a product of biomineralization process of magnetotactic bacteria Magnetospirillum sp. AMB-1. From temperature dependence of remanent magnetization and coercive field the Verwey transition is clearly seen at 105 K as a consequence of the large anisotropy along the chains of magnetosomes.
19
Content available remote

Magnetic Properties and Sorption Activity of Mechanically Activated Magnetite Fe_3O_4

76%
Baláž P., Timko M., Kováč J., Bujňáková Z., Ďurišin J., Myndyk M., Šepelák V.
|
|
issue 5
1005-1007
EN
It is known that the action of mechanical forces on solids (mechanical activation and/or mechanochemistry) leads to changes of their properties and reactivity. We have studied the physico-chemical and sorption properties of magnetite Fe_3O_4 (Kiruna, Sweden) mechanically activated in a planetary mill. Several methods such as X-ray diffractometry, Mössbauer spectroscopy, magnetometry, specific surface area measurement as well as arsenic sorption tests have been applied. By X-ray diffractometry strong amorphisation of magnetite has been evidenced. In parallel, specific surface area increased from 0.1 m^2/g for the reference (non-milled) sample to the values 0.5-6.1 m^2/g for milled samples. The Mössbauer spectrum of the reference sample is well fitted with two subspectra corresponding to tetrahedrally (A) and octahedrally (B) coordinated iron cations in the spinel structure of Fe_3O_4. In mechanically activated samples (B)-site subspectrum becomes asymmetric, while (A)-site spectrum remains more or less unchanged. The more covalent character of the Fe(A)-O bond compared to the Fe(B)-O bond can explain qualitatively why the spin-density transfer from (A) to (B) in the spinel structure is more effective than vice versa. The value of the saturation magnetization at room temperature was 67.4 ≈ 43.6 emu/g which is significantly lower than that of the bulk particles 92 emu/g. This reduction may be attributed to the surface disorder or spin canting at the particle surface. During the milling process the coercivity value increases from 150 Oe up to 460 Oe with milling time. This increase can be related to the fact that magnetic anisotropy may increase when particle size decreases. The sorption activity of Fe_3O_4 was enhanced as a consequence of its disordering: 88% of As^{3+} was captured for the mechanically activated sample in comparison with 0% for the non-milled one.
20
Content available remote

Magnetic Charcoal Supporting Silver as a Water Disinfectant

76%
Valušová E., Antalík M., Pristaš P., Javorský P., Kováč J., Timko M.
|
|
vol. 126
|
issue 1
226-227
EN
We investigated the magnetic behavior of charcoal composite with incorporated magnetite and silver ions. The magnetization curve measured at 282 K showed saturation magnetization of 8 emu/g. By benefiting from a mechanical process, the magnetic activated carbon, supporting silver ions (MCAG), acts as a magnetic filter uptaking the bacteria. This idea was confirmed by the DGGE analysis in which the bacterial DNA was detectable in the sediment after the treatment.
first rewind previous Page / 3 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.