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1
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Magnetic Study of Phases in FeVO₄-Co₃V₂O₈ System

100%
Guskos N., Zolnierkiewicz G., Pilarska M., Typek J., Blonska-Tabero A., Aidinis C.
Acta Physica Polonica A
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2017
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vol. 132
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issue 1
24-30
EN
Magnetic properties of four nFeVO₄/(1-n)Co₃V₂O₈ samples obtained in reactions between FeVO₄ and Co₃V₂O₈ (n = 0.96, 0.86, 0.84 and 0.83, samples designated S1, S3, S4, S5, respectively) have been investigated by DC magnetisation in field cooling and zero-field-cooling modes and EPR. DC magnetic susceptibility showed paramagnetic behavior of all samples in high-temperature range (T > 20 K) and transition to antiferromagnetic state at 16-18 K (depending on sample iron content). Additional magnetic freezing at 8 K was registered for S3-S5 samples containing larger amount of cobalt. The Curie-Weiss law in 100-300 K temperature range indicates that Co²⁺ is in the high-spin state (S = 3/2). From the parameters of the hysteresis loop observed for the samples it was calculated that 0.58% of all magnetic (Fe³⁺, Co²⁺) ions were involved in the ferromagnetic states. EPR spectra of the samples were recorded in high temperature range (T > 90 K). The temperature dependence of the spectral parameters (resonance field, linewidth, integrated intensity) suggested the Fe³⁺ high-spin ions coupled by antiferromagnetic interaction and clusters of ions play major role in EPR spectra.
2
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Magnetic properties of co-modified Fe,N-TiO2nanocomposites

100%
Zolnierkiewicz G., Glenis S., Guskos N., Guskos A., Typek J., Berczynski P., Dolat D., Mozia S., Morawski A. W.
Open Physics
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2015
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vol. 13
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issue 1
EN
Iron and nitrogen co-modified titanium dioxide nanocomposites, nFe,N-TiO2 (where n = 1, 5 and 10 wt% of Fe), were investigated by detailed dc susceptibility and magnetization measurements. Different kinds of magnetic interactions were evidenced depending essentially on iron loading of TiO2. The coexistence of superparamagnetic, paramagnetic and ferromagnetic phases was identified at high temperatures. Strong antiferromagnetic interactions were observed below 50 K, where some part of the nanocomposite entered into a long range antiferromagnetic ordering. Antiferromagnetic interactions were attributed to the magnetic agglomerates of iron-based and trivalent iron ions in FeTiO3 phase,whereas ferromagnetic interactions stemmed from the F-center mediated bound magnetic polarons.
3
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Microwave X-Band Resonances in Doped Cd₂Nb₂O₇ Monocrystals

84%
Waplak S., Ostrowski A., Wencka M., Bednarski W.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
7-11
EN
Cadmium pyroniobiate (CNO) is the ferroic material with unusual diffuse phase diagram which includes both relaxor and nanocluster domains. We present the data for CNO crystals with several admixtures of paramagnetic ions studied on X and S microwave bands at zero-external magnetic field and classical EPR conditions. Our results lead to an assertion of a ferroelectric resonance effect due to "electronic ferroelectricity". The data fit well to the Falicov-Kimball theoretical model applicable to strongly-correlated-electron or mixed-valence systems.
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

84%
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

84%
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
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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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EMR Data on Mn(III; S=2) Ions in MnTPPCl Complex Modelled by Microscopic Spin Hamiltonian Approach

68%
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.
7
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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

68%
Zając M., Rudowicz C.
Acta Physica Polonica A
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2017
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vol. 132
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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.
8
Content available remote

Spin Hamiltonian Parameters for Co²⁺ Ions in PbMoO₄ Crystal - Interplay between the Fictitious Spin S'=1/2 and the Effective Spin S̃ =3/2

68%
Piwowarska D., Kaczmarek S., Gnutek P., Rudowicz C.
Acta Physica Polonica A
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2017
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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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