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1
Content available remote

EPR and Impedance Measurements of Graphene Oxide and Reduced Graphene Oxide

100%
Kempiński M., Łoś S., Florczak P., Kempiński W., Jurga S.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
81-85
EN
We report the observations of electron paramagnetic resonance and impedance measurements of graphene oxide and reduced graphene oxide performed in the wide temperature range in order to get insight into the electronic properties of graphene-based materials and the role of oxygen functionalities in the charge carrier transport phenomena. In such systems the strong spin localization, hopping charge carrier transport as well as the formation of adsorption layers are observed, all the phenomena changing significantly after the heavily oxidized graphene is reduced.
2
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EMR Spectra Thin Films Doped with High Concentration of Co and Cr on Quartz and Sapphire Substrates

76%
Cieniek B., Stefaniuk I., Virt I.
Acta Physica Polonica A
|
2017
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vol. 132
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issue 1
30-34
EN
We have studied magnetic properties of zinc-oxide composite doped with high concentration (up to 20%) of Co and Cr ions. The pulsed laser deposition method was used to obtain samples on quartz glass and sapphire substrates. Samples were annealed at 100-250°C for ZnO on quartz substrate, and 300-700°C on sapphire substrate. EMR measurements were carried out and temperature dependence of the EMR spectra was obtained. The angular dependence in two samples orientation, vertical and horizontal, were also obtained. Analysis of the temperature dependences of the integral intensity of EMR spectra was carried out using the Curie-Weiss law.
3
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Anisotropy of g_{eff} Factor for Ni_{50}Mn_{35.5}In_{14.5} Heusler Alloy

76%
Dubiel Ł., Wal A., Stefaniuk I.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
91-93
EN
In this work electron magnetic resonance (EMR) spectra of off-stoichiometric Ni_{50}Mn_{35.5}In_{14.5} Heusler alloy ribbons obtained by melt-spinning method were measured. The EMR measurements were performed on the X-band (9.36 GHz) spectrometer. Angle dependences were registered for three orientations of sample, with the use of uniaxial goniometer at 300. The results exhibited magnetic anisotropy and were used for calculating the principal values of g tensor.
4
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Conversions of the Second-Rank Zero Field Splitting Parameters Measured Assuming the Fictitious Spin S'=1 to those for the Effective Spin S̃=2

64%
Kozanecki M., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
11-14
EN
We investigate feasibility of comparison between the zero field splitting parameters obtained experimentally based on the spin Hamiltonian with the fictitious spin S'=1 and those with the effective spin S̃=2. The former zero field splitting parameters have recently been measured for Fe²⁺ ions in forsterite Mg₂SiO₄, whereas the latter zero field splitting parameters are available in literature, e.g. for Fe²⁺ and Cr²⁺ (S̃=2) ions. It turns out that no unique direct comparison is feasible and hence appropriate conversion relations need to be derived. Methodology for such conversions is outlined. Various combinations of the possible energy level schemes for the spin S̃=2 and S'=1 are briefly described. Illustrative preliminary results concerning appropriate conversions of the second-rank zero field splitting parameters measured by high-frequency EMR for Fe²⁺ in natural and synthetic forsterite are presented. Detailed results and full analysis will be given elsewhere.
5
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EPR Study of Dealuminated HY Zeolite and Silica Containing Cu-Mn-Zn Spinels: The Effect of Support

64%
Decyk P., Więckowski A., Najder-Kozdrowska L., Bilkova I., Ziółek M.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
38-44
EN
A mixture of antiferromagnetic Cu_{1.4}Mn_{1.6}O₄ and Cu_{0.5}Zn_{0.5}Mn₂O₄ or/and ZnMn₂O₄ spinels was prepared. Dealuminated HY zeolite and silica were doped by these Cu-Mn-Zn spinels. The materials were investigated by X-ray diffraction, the Fourier transform infrared spectroscopy and EPR spectroscopy. Additionally, all the samples were tested for their activity for isopropyl alcohol dehydration/dehydrogenation. Three EPR signals were observed for Cu-Mn-Zn/dealuminated HY and Cu-Mn-Zn/SiO₂ samples at 293 K. In contrast to the spectra recorded at 293 K, only one broad line attributed to Cu-Mn-Zn spinels was visible at 77 K. The EPR signal from pure Cu-Mn-Zn spinels consists only of a single broad line when recorded at 293 K, whereas at 77 K the line is narrower. For all samples subjected to evacuation at high vacuum up to 573 K, the Cu-Mn-Zn spinels were stable. The evacuation at 673 K resulted in a rapid lowering of the intensity of EPR spectrum.
6
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Magnetic Study of Nanocrystalline TiB₂, TiC, B₄C Powders Doped to AISI 316L Austenitic Steel

64%
Bodziony T., Kaczmarek S., Biedunkiewicz A., Leniec G., Figiel P.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
62-68
EN
The investigations into ferromagnetic resonance and magnetic susceptibility of nanocrystalline TiB₂, TiC, and B₄C powders (Ti-B-C system) doped to AISI 316L austenitic steel with different amounts (3 vol.%, 5 vol.% and 7 vol.%) have been carried out. The ferromagnetic resonance spectra were recorded in the temperature range from helium up to room temperature. The three tested composite samples contain a number of magnetic phases in different proportions. They reveal a structure originating from several different complex magnetic centers. The composites revealed such magnetic phenomena as paramagnetism, (anti)ferromagnetism, and superparamagnetism. Magnetic susceptibility investigations supported the ferromagnetic resonance studies and their analysis. Magnetic properties of the TiB₂, TiC, B₄C powders doped to AISI steel may play important role in further possible applications of these composite systems.
7
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EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

52%
Tadyszak K., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
15-19
EN
The electron magnetic resonance data on high-spin (S =2) manganese(III) 3d⁴ ion in tetraphenylporphyrinato chloride complex (MnTPPCl) obtained by high-frequency techniques are reanalysed. Preliminary results of semiempirical modeling of the spin Hamiltonian parameters for Mn(III) in MnTPPCl are presented. The microscopic spin Hamiltonian approach is utilized to predict the zero-field splitting and the Zeeman electronic parameters. It is found that for Mn(III) ions in MnTPPCl matching the experimental spin Hamiltonian parameters and the theoretical ones based on the ligand-field energy levels (Δ_{i}) within the ⁵D multiplet only may not be suitable for this system. Contributions due to the levels arising from the higher-lying ³H multiplet need to be taken into account in order to determine the reasonable values of microscopic parameters describing Mn(III) ions in MnTPPCl.
8
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Comparative Analysis of Experimental and Theoretical Zero-Field Splitting and Zeeman Electronic Parameters for Fe²⁺ Ions in FeX₂·4H₂O (X = F, Cl, Br, I) and [Fe(H₂O)₆](NH₄)₂(SO₄)₂

52%
Zając M., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
19-23
EN
Spectroscopic and magnetic properties of Fe²⁺ (3d⁶; S=2) ions at orthorhombic sites in FeX₂·4H₂O (X = F, Cl, Br, I) crystals are compared with those in [Fe(H₂O)₆](NH₄)₂(SO₄)₂ (FASH). The microscopic spin Hamiltonian modeling utilizing the package MSH/VBA enables prediction of the zero-field splitting parameters and the Zeeman electronic ones. Wide ranges of values of the microscopic parameters, i.e. the spin-orbit (λ), spin-spin (ρ) coupling constants, and the crystal-field (ligand-field) energy levels (Δp_{i}) within the ⁵D multiplet are considered to establish the dependence of the zero-field splitting parameters b_{k}^{q} (in the Stevens notation) and the Zeeman factors g_{i} on λ, ρ, and Δp_{i}. By matching the theoretical spin Hamiltonian parameters and the experimental ones measured by EMR, the suitable values of λ, ρ, and Δp_{i} are determined. The novel aspect is prediction of the fourth-rank zero-field splitting parameters and the ρ (spin-spin)-related contributions, not considered in previous studies. The MSH predictions provide guidance for high-magnetic field and high-frequency EMR measurements.
9
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Optimization of Antioxidant Properties of Creams with Berry Extracts by Artificial Neural Networks

52%
Makarova K., Zawada K., Wagner D., Skowyra J.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
44-51
EN
Oxidative stress and the excess of free radicals accelerate the ageing process of human skin. The application of skin cream with antioxidant compounds could reduce the damage caused by free radicals. In this work we studied two types of skin creams with extracts from aronia (Aronia melanocarpa), elderberry (Sambucus nigra) and bilberry (Vaccinium myrtillus) because of their high content of anthocyanins, i.e. strong natural antioxidants. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability of the skin creams with berry extracts were studied with ESR spectroscopy. The artificial neural networks were applied to optimize the berry extract concentration and storage time for oil-in-water and water-in-oil creams. Based on experimental results chokeberry and elderberry extracts in oil-in-water cream base revealed higher DPPH radical scavenging ability than in the corresponding water-in-oil. Artificial neural networks predicts maxima of DPPH radical scavenging for 1-week stored elderberry (2.23 mg DPPH/g) and 1-week stored chokeberry (5.84 mg DPPH/g) and bilberry (5.26 mg DPPH/g) 0.76% extracts in oil-in-water creams. The maxima of DPPH radical scavenging for water-in-oil creams were predicted for 6-week stored 0.8% aronia extract, freshly prepared 0.76% bilberry extract and 1-week stored 0.56% elderberry extract. The artificial neural networks predicted values are in good agreement with the experimental values. DPPH-EPR could be combined with artificial neural networks to optimize the extract concentration, and the type of cream base as well as to predict the effect of storage based on a limited number of experiments and samples.
10
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Spin Hamiltonian Parameters for Co²⁺ Ions in PbMoO₄ Crystal - Interplay between the Fictitious Spin S'=1/2 and the Effective Spin S̃ =3/2

52%
Piwowarska D., Kaczmarek S., Gnutek P., Rudowicz C.
Acta Physica Polonica A
|
2017
|
vol. 132
|
issue 1
73-76
EN
The interplay between the fictitious spin S' = 1/2 and the effective spin S̃=3/2 for Co²⁺(3d⁷) ions is considered. The available experimental data on the Ze g_{i}' factors for the two Co²⁺ complexes in PbMoO₄ obtained using the fictitious "spin" S'=1/2 description serve for determination of the Zeeman g_{i} factors corresponding to the effective spin S̃ =3/2. The second-rank zero-field splitting parameters D and E (S̃ = 3/2) are also indirectly determined from the experimental EMR data by employing the formulas arising from projection of the g_{i}(S̃=3/2) factors onto the g_{i}'(S' = 1/2) factors. The so-determined second-rank zero-field splitting parameters and g_{i}(S̃ = 3/2) factors will enable comparison with the respective quantities obtained in a subsequent paper using a combined modeling approach.
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