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1
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Ab Initio Study of the ^{57}Fe Electric Field Gradient in (FeAl)_{1-x}T_x (T = 3d Element) Dilute Alloys with B2-Type Structure

100%
Michalecki T., Hanc A., Deniszczyk J., Borgieł W.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1483-1491
EN
We present an ab initio study of the electric field gradient at Fe nuclei in the series of (FeAl)_{1-x}T_x dilute alloys with B2-type crystal structure. The ternary additions T, of concentration x ≈ 0.06, from the group of 3d-type transition metals (Ti, V, Cr, Mn, Co, Ni, Cu) are considered. Lattice, local valence electron (3d, 4p) and weakly bound 3p core electron contributions to electric field gradient are separated out and discussed in the context of the T-atom site preference and changes of the electronic structure upon alloying. Contrary to earlier reports, we found that for most Fe nuclei the dominant contribution comes from the d-type valence electrons cancelled partially by the 3p and 4p electric field gradients which are both of opposite sign to that of the 3d one. The shielding effect of 3p semicore electrons is found and related to the electric field gradient contributed by the local valence electrons.
2
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Hyperfine Interaction Parameters in Fe_{28}Al_{72}: ^{57}Fe Mössbauer Spectroscopy and Ab Initio Study

100%
Hanc A., Deniszczyk J., Kansy J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1154-1155
EN
The paper discusses a theoretical model that associates the shape of the Mössbauer spectrum with the configuration of atoms in local surroundings of the Mössbauer nuclide. Using the model we analyse the Mössbauer spectra of Fe_{72}Al_{28} alloys after various heat treatments. Basing on the model calculations the hyperfine structure parameters describing an effect of an Al atom in the first and the second coordination shell of ^{57}Fe atom are evaluated. Using these parameters the values of hyperfine magnetic field and isomers shift for the atomic configurations present in stoichiometric Fe_3Al are estimated and compared with the results of ab initio calculations.
3
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Mössbauer Spectroscopy, X-Ray Diffraction and SEM Studies on Multiferroic Bi_5Ti_3FeO_{15} Ceramics

100%
Rymarczyk J., Hanc A., Dercz G., Ilczuk J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1579-1584
EN
Magnetoelectric multiferroics are materials which exhibit both magnetic order and ferroelectricity in the same phase. Multiferroic materials, where ferroelectricity and magnetism coexist, were extensively studied. This class of materials offers a large application potential for new devices due to the two coupled degrees of freedom based on the local off-centered distortion and the electron spin. The studied Bi_5Ti_3FeO_{15} ceramics was prepared by conventional synthesis and hot uniaxial pressing reaction applying the conventional mixture of TiO_2, Fe_2O_3 and Bi_2O_3 oxides as precursor materials. The present work focuses on the structure analysis of multiferroic Bi_5Ti_3FeO_{15} ceramics performed by X-ray diffraction method, scanning electron microscopy and the Mössbauer spectroscopy methods.
4
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Influence of Heat Treatment on Ordering Process in Fe_{72}Al_{28} Alloy Studied by Mössbauer Spectroscopy

100%
Kansy J., Hanc A., Giebel D.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
44-47
EN
The paper discusses a theoretical model that associates the shape of Mössbauer spectrum with the configuration of atoms in local surroundings of the Mössbauer nuclide. The model has been implemented to a computer program which was used to analyse the Mössbauer spectra of Fe_{72}Al_{28} alloys after various heat treatments. Basing on the determined configuration of atoms, the long range ordering parameter was estimated.
5
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The Mössbauer Spectroscopy Studies of ϵ to Cementite Carbides Transformation during Isothermal Heating from As-Quenched State οf High Carbon Tool Steel

100%
Bała P., Krawczyk J., Hanc A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1641-1650
EN
This work presents results of investigations using the Mössbauer spectroscopy technique and their interpretation concerning transformation of ϵ to cementite carbides during tempering in relation to the previously conducted dilatometric, microscopic and mechanical investigations. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The influence of the tempering time on nucleation and solubility of ϵ carbides, and on cementite nucleation and growth, was determined. The analysis of phase transformations during various periods of tempering using the Mössbauer spectroscopy technique made possible to reveal fine details connected with the processes.
6
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The Mössbauer Spectroscopy Studies οf Cementite Precipitations during Continuous Heating from As-Quenched State of High Carbon Cr-Mn-Mo Steel

100%
Krawczyk J., Bała P., Hanc A.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1651-1657
EN
This work complements the knowledge concerning the kinetics of cementite precipitation during tempering. Investigations were performed on 120MnCrMoV8-6-4-2 steel. The samples of investigated steel were austenitized at the temperature of 900°C and quenched in oil. Then four of five samples were tempered. Tempering consisted of heating the samples up to chosen temperatures at the heating rate of 0.05°C/s and fast cooling after reaching desired temperature. This work presents the results of investigations performed carried out using the Mössbauer spectroscopy technique and their interpretation concerning cementite nucleation and growth during tempering. The values of hyperfine magnetic field on ^{57}Fe atomic nuclei, determined for the third component of the Mössbauer spectrum as regards to its intensity, indicate that these are the components coming from ferromagnetic carbides. Big differences in hyperfine magnetic fields coming from Fe atoms existing in the structure of carbides, measured on samples heated up to the temperatures of 80°C and 210°C, in comparison with values for ^{57}Fe atoms precipitated from carbides during heating up to the temperature of 350°C and 470°C, allow to state that these are the carbides of different crystal structure. The influence of hardened steel heating temperature on cementite precipitation was determined. The Mössbauer spectroscopy was applied not only for magnetic hyperfine fileld studies, but also to analyze the values of quadrupole splitting and isomeric shift, which resulted in significant conclusions concerning the changes in cementite precipitations morphology, chemical composition and the level of stresses being present in this research.
7
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Vacancy Formation in Fe-Al of B2 and DO_3 Alloys

100%
Kansy J., Hanc A., Giebel D., Jabłońska M.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1409-1415
EN
The positron lifetime spectroscopy is employed to study vacancy formation in intermetallic phases of DO_3 and B2 structures from Fe-Al system as a function of Al concentration, ternary additive (Cr) and their thermal treatment. Lifetime spectra were fitted en block by a simple trapping model encoded directly to the software (computer program LT-9). In the investigated range of Al concentration (28, 38, 42, and 45 at%) only two types of defects are found. In DO_3 region a single type of defects (characterized by positron lifetime τ_1=170±2 ps) is detected and indicated as vacancies in the Fe sublattice (V_{Fe}). In B2 region a small amount of an additional type of defects (characterized by positron lifetime τ_2=214±13 ps) appears. Supposedly, these are vacancies in Al sublattice (V_{Al}). For Fe28Al and Fe28Al5Cr samples changes in V_{Fe} concentration are determined as a function of the sample composition, annealing time at 1000°C and quenching the samples to air and oil. The defect concentration increases with increase in Al content. For FeAl with Al above 38 at%, the total concentration of defects is so high that positrons are exclusively trapped by defects. Therefore the concentrations V_{Al} and V_{Fe} cannot be determined separately. However, the ratio of V_{Al} concentration to V_{Fe} concentration is estimated as a function of Al content.
8
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Structural Studies with the Use of XRD and Mössbauer Spectroscopy οf Bi_5Ti_3FeO_{15} Ceramic Powders Obtained by Mechanical Synthesis

76%
Dercz G., Rymarczyk J., Hanc A., Prusik K., Babilas R., Pająk L., Ilczuk J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1623-1629
EN
In this paper the structural and Mössbauer spectral properties of multiferroic ceramic Bi_5Ti_3FeO_{15} powders prepared by high-energy ball milling of polycrystalline precursor material (mixture of Bi_2O_3, TiO_2 and Fe_2O_3 powders) are presented. Mechanical synthesis was performed by high-energy vibratory mill. The X-ray diffraction methods were applied for the structure characterization of the studied samples. The parameters of diffraction line profiles were determined by PRO-FIT Toraya procedure. The crystallite sizes and lattice distortions were analyzed using the Williamson-Hall method. Investigations of hyperfine interactions in the studied materials were carried out by the Mössbauer spectroscopy. The powder morphology was analyzed by scanning electron microscopy and transmission electron microscopy techniques. It was found that during high-energy milling phase transitions, a decrease in crystallite size and amorphization process are observed.
9
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The Mössbauer Spectroscopy and Analytical Investigations οf the Polycrystalline Compounds with General Formula Zn_xSn_yCr_zSe_4

76%
Jendrzejewska I., Hanc A., Zajdel P., Kita A., Goryczka T., Maciążek E., Mrzigod J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1591-1597
EN
We present combined X-ray powder diffraction and Mössbauer ^{119}Sn studies of polycrystalline compounds with a general formula Zn_xSn_yCr_zSe_4 (where x+y+z ≈3). The obtained single-phase compounds crystallize in the spinel cubic structure - Fd3m. Tin ions are found to occupy both tetrahedral and octahedral sublattices. On the contrary to the strong tetrahedral site preference energy of Sn, the presented data strongly suggest that the increase in lattice parameters with Sn doping is caused by Sn ions that incorporated into octahedral positions. A quadrupole and isomer shifts of ^{119}Sn in (SnSe_4)^{6-} and (SnSe_6)^{4-} are also reported.
10
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The Mössbauer and X-Ray Studies οf the Spinel Ferrites Cu_{0.5}Fe_{0.5}Cr_2Se_4 and Cu_{0.2}Fe_{0.8}Cr_2Se_4 Prepared by the Ceramic Method

76%
Maciążek E., Hanc A., Sitko R., Zawisza B., Jendrzejewska I., Mrzigod J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1599-1603
EN
Seleno-spinels with nominal chemical composition Cu_{0.5}Fe_{0.5}Cr_2Se_4 and Cu_{0.2}Fe_{0.8}Cr_2Se_4 were prepared as polycrystalline samples using ceramic method. The assumed composition was verified by wavelength-dispersive X-ray fluorescence spectrometry. The X-ray analysis was carried out in order to make phase analysis and to compare its results with those obtained with the Mössbauer spectroscopy.
11
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A Study of Point Defects in the B2-Phase Region of the Fe-Al System by Mössbauer Spectroscopy

76%
Hanc A., Kansy J., Dercz G., Pająk L., Oleszak D., Mrzigod J.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1555-1562
EN
In this work, we employed the Mössbauer spectroscopy and X-ray powder diffraction in a study of point defect formation in intermetallic phases of the B2 structure of the Fe-Al system as a function of Al concentration. The results are compared with the concentrations of point defect determined from positron annihilation data. In the Mössbauer effect, two types of samples are investigated: Fe-Al alloys with few additives obtained by induction melting and Al-rich metallic powders produced by the self-decomposition method and intensive grinding of high energy in the electro-magneto-mechanical mill. We present the values of the ^{57}Fe isomer shift and quadrupole splitting for the components describing the point defect in the local environment of a Mössbauer nuclide. The concentration of the Fe vacancies and Fe atoms substituting Al (Fe-AS) are determined. The results showed that an increase in Al content causes an increase in vacancy and Fe-AS concentration.
12
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Structural Relaxation in Fe_{78}Nb_{2}B_{20} Amorphous Alloy Studied by Mössbauer Spectroscopy

76%
Kansy J., Hanc A., Rasek J., Haneczok G., Pająk L., Stokłosa Z., Kwapuliński P.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
41-43
EN
It was shown that soft magnetic properties of Fe_{78}Nb_{2}B_{20} amorphous alloy can be significantly improved by applying 1-h annealing at temperature 623 K (permeability increases even about 8 times). The Mössbauer Spectroscopy technique indicated that the optimized microstructure (corresponding to the maximum magnetic permeability) is free of iron nanograins and should be attributed to annealing out of free volume and a reduction of internal stresses i.e. to the relaxed amorphous phase.
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