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1
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The Low Temperature Study of Ln[Fe(CN)_6]·xH_2O Rare-Earth Ferricyanides, Ln=Pr,La

100%
Maťaš S., Mitróová Z., Kiefer K., Ryll H., Prokeš K.
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issue 5
962-964
EN
We present magnetic and structural properties of Ln[Fe(CN)_6]·xH_2O, Ln = Pr, La single crystals investigated by means of elastic neutron diffraction and heat capacity down to 0.03 K and susceptibility and magnetization measurements. The susceptibility data were taken on the commercial SQUID magnetometer (Quantum Design) in the range between 2 K and 30 K and in fields up to 5 T. Our low temperature neutron diffraction data taken in a zero field rules out some of antiferromagnetic models suggested in the literature.
2
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Synthesis and Characterization of Magnetoferritin

100%
Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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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.
3
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Magnetic Birefringence Study of the Magnetic Core Structure of Ferritin

86%
Koralewski M., Pochylski M., Mitróová Z., Melníková L., Kováč J., Timko M., Kopčanský P.
Acta Physica Polonica A
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2012
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vol. 121
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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.
4
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Lysozyme Amyloid Fibrils Doped by Carbon Nanotubes

86%
Majorošová J., Tomašovičová N., Mitróová Z., Rajňák M., Girman V., Kopčanský P.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
588-590
EN
Production of new composites for the creation of modern materials with desired properties is the key feature of nanotechnology. Despite the well known advantages of magnetic nanoparticles, the aim of the present study was to synthesize lysozyme amyloid fibrils from hen egg white and subsequently doped this solution with single walled carbon nanotubes and with the magnetite Fe₃O₄ labelled single walled carbon nanotubes. Transmission electron microscopy and polarization optical microscopy were used to obtain the structural and dimensional information about samples. Measurements of magnetic properties indicate the considerable increase of the saturation magnetization for solutions included the magnetite nanoparticles.
5
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AC Magnetic Susceptibility of Ferrofluids Exposed to an External Electric Field

73%
Rajňák M., Dolník B., Kováč J., Paulovičová K., Mitróová Z., Kurimský J., Cimbala R., Kopčanský P., Timko M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 4
887-889
EN
It is known that ferrofluid superparamagnetic nanoparticles response to external magnetic fields, often resulting in the formation of elongated clusters along the field. This has a notable impact on dielectric properties of ferrofluids. Here we report on indications of a contrary effect when the magnetic susceptibility of ferrofluids based on transformer oil is influenced by an external electric field. This effect is associated with structural changes in the ferrofluids induced by the external electric fields. Particularly, we focus on a steady state electric field effect, which gives rise to forces acting on the magnetite nanoparticles, leading to the formation of aggregates. In this condition we have measured the ferrofluid AC magnetic susceptibility in parallel and perpendicular configuration of magnetic and electric fields at room temperature. The measurements in both configurations yielded a noticeable decrease in the real susceptibility values with increasing electric field intensity. The result is believed to be caused by the reduction in the total magnetic moment of the ferrofluid. This can be a consequence of the superspin interactions in the aggregates, minimizing the aggregate's energy. Finally, we highlight the necessity of NMR and small angle scattering of polarized neutrons investigations in order to obtain exact information on the magnetic structure induced by the electric forces.
6
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Magnetic Relaxation and Memory Effect in Nickel-Chromium Cyanide Nanoparticles

73%
Zentko A., Kavečanský V., Mihalik M., Maťaš S., Mitróová Z., Zentková M., Maryško M., Jagličić Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
511-514
EN
The low temperature dynamics of a magnetic nanoparticle system Ni_3[Cr(CN)_6]_2 with an average nanoparticles size of 4 nm was studied. Using different temperature and field protocols memory phenomena were studied by the DC magnetization and magnetic relaxation measurements of the system at temperatures below T_m = 19 K. Aging experiments show an absence of any waiting time dependence in the magnetization relaxation due to a field change after zero field and field cooling. This observation discriminates the dynamics of the system from the behaviour of a classical spin-glass.
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Effect of Pressure on Magnetic Properties of TM_3[Cr(CN)_6]_2 · nH_2O Nanoparticles

73%
Zentko A., Zentková M., Kavečanský V., Mihalik M., Mitróová Z., Arnold Z., Kamarád J., Cieslar M., Zeleňák V.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
489-493
EN
Effect of pressure on magnetic properties of magnetic nanoparticles, based on Prussian blue analogues, were studied in pressures up to 1.2 GPa. The Mn_3[Cr(CN)_6]_2·nH_2O and Ni_3[Cr(CN)_6]_2·nH_2O nanoparticles were prepared by reverse micelle technique. Transmission electron microscopy images show nanoparticles with average diameter of about 3.5 nm embedded in an organic matrix. The characteristic X-ray peaks of nanoparticles are more diffused and broader. Systems of nanoparticles behave as systems of interacting magnetic particles. The Curie temperature T_C is reduced from T_C = 56 K for Ni-Prussian blue analogues to T_C = 21 K for Ni-nanoparticles system and from T_C = 65 K for Mn-Prussian blue analogues to T_C = 38 K for Mn-nanoparticles system. One can explain this reduction of the Curie temperature and of the saturated magnetizationμ_s by dispersion of nanoparticles in an organic matrix i.e. by a dilution effect. Applied pressure leads to a remarkable increase in T_C for system of Mn-nanoparticles (ΔT_C/Δp = +13 K/GPa) and to only slight decrease in T_C for system of Ni-nanoparticles (ΔT_C/Δp = -3 K/GPa). The pressure effect follows behavior of the mother Prussian blue analogues under pressure. The increase in saturated magnetization, attributed to compression of the organic matrix, is very small.
8
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^1H NMR on (Ni_xMn_{1-x})_3[Cr(CN)_6]_2 · nH_2O

73%
Bokor M., Tompa K., Kiss L., Zentková M., Zentko A., Mihalik M., Maťaš S., Mitróová Z.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
485-488
EN
We report on ^1H NMR of (Ni_xMn_{1-x})3[Cr(CN)_6]_2·15H_2O hexacyanochromates, where x changes from 0 to 1. The decay time constants of the free induction decay signals described by an effective spin-spin relaxation time T_{2eff} obtained from M(t) = M_0 exp(t/T_{2eff}) decrease as the local magnetic moments increase produced by the magnetic transition metal ions at the sites of the resonant ^1H nuclei. The recovery of the magnetization in the spin-lattice relaxation time (T_1) experiments was single-exponential.
9
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Magnetic-Field Induced Isotropic-Nematic Phase Transition in PDLC Doped with Magnetic Nanoparticles

73%
Mitróová Z., Tomašovičová N., Timko M., Koneracká M., Tomčo L., Jadżyn J., Palewski, T., Kopčanský P., Kovalchuk O.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1299-1301
EN
The paper presents a study of the polymer dispersed liquid crystals that consist of liquid crystal 4-trans-4'-n-hexyl-cyclohexyl-isothiocyanatobenzene (6CHBT) microdroplets dispersed in polyvinyl alcohol and doped with various kinds of magnetic particles. As magnetic nanoparticles there were used single walled carbon nanotubes and magnetite labeled single walled carbon nanotubes. The volume concentration of the particles was 2 × 10^{-3}. Magnetic properties were investigated by a SQUID magnetometer. The higher saturation magnetization has been achieved in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes. The phase transition temperature from isotropic to nematic phase at the external magnetic field 0 T and 12 T was monitored by precise capacitance measurements in the capacitance cell filled with prepared sample. The significant shift of the phase transition temperature (0.2°C) at the external magnetic field 12 T has been observed in sample polymer dispersed liquid crystal doped with magnetite labeled single walled carbon nanotubes.
10
Content available remote

Thermal Stability of Bent-Core Liquid Crystals Doped with Magnetic Nanoparticles

59%
Juríková A., Csach K., Miškuf J., Tomašovičová N., Mitróová Z., Závišová V., Koneracká M., Kopčanský P., Timko M., Éber N., Fodor-Csorba K., Vajda A.
Acta Physica Polonica A
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2015
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vol. 127
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issue 2
638-640
EN
In the work phase transitions in bent-core liquid crystals were studied using differential scanning calorimetry. For the binary mixture of bent-core molecules with 50 wt% of rod-shaped compound, the nematic to smectic transition occured below 40°C and the crystallization temperature shifted to sub-ambient temperatures. The influence of doping of the bent-core liquid crystals with magnetic nanoparticles on the kinetics of observed phase transitions was studied. The phase transition temperatures were shifted depending on the nanoparticle type and changed with varying cooling rate for all studied liquid crystal samples.
11
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Structural Phase Transition in Liquid Crystal Doped with Gold Nanoparticles

59%
Kopčanský P., Tomašovičová N., Koneracká M., Timko M., Mitróová Z., Závišová V., Éber N., Fodor-Csorba K., Tóth-Katona T., Vajda A., Jadzyn J., Beaugnon E., Chaud X.
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issue 5
988-989
EN
The influence of the inclusion of the dodecanethiol functionalized gold particles (with diameter 3-5 nm) on the structural transitions was investigated. The studied samples were based on the nematic liquid crystal 4-(trans-4'-n-hexylcyclohexyl)-isothiocyanatobenzene (6CHBT). The volume concentration of the gold particles was ϕ_1 = 2 × 10^{-4} and ϕ_2 = 10^{-3}. The obtained results showed that the inclusion of the gold particles in the 6CHBT liquid crystal increases the sensitivity of such system on the external magnetic field.
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