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1
Content available Effect of Sc substitution for Y on structural properties and hyperfine interactions in Y1-xScxFe2 compounds
100%
Budzyński M. , Sarzyński J. , Wiertel M. , Surowiec Z.
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tom Vol. 48,suppl.1
79-83
EN
Measurements of X-ray diffraction and Mössbauer effect were made on a series of Y1-xScxFe2 polycrystalline samples (x = 0.0, 0.2, 0.5, 0.7, 0.8, 1.0). It was found that the system has the cubic MgCu2 structure except for x = 1.0 where hexagonal MgZn2 structure type is stable. The lattice constant decreases with increasing x. The results of Mössbauer effect study at room temperature show that the easy axes of magnetization remain in the <111> direction for the cubic samples and <100> for the hexagonal one. Curie temperatures TC were determined from temperature dependence of the hyperfine magnetic fields. The concentration dependence of the hyperfine fields and TC show similar trends, exhibiting a maximum at x = 0.8. The magnetic and structural behaviour show that, in spite of being isoelectronic, the substitution of Y by Sc induces clear changes in the structural and magnetic properties of the compounds under investigation.
2
Content available Study on the effect of atmospheric gases adsorbed in MnFe2O4/MCM-41 nanocomposite on ortho-positronium annihilation
100%
Wiertel M. , Surowiec Z. , Budzyński M. , Gac W.
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tom Vol. 60, No. 4, part 1
783--787
EN
In this paper, results of positron annihilation lifetime spectroscopy (PALS) studies of MnFe2O4/MCM- -41 nanocomposites in N2 and O2 atmosphere have been presented. In particular, the influence of manganese ferrite loading and gas filling on pick-off ortho-positronium (o-Ps) annihilation processes in the investigated samples was a point of interest. Disappearance of the longest-lived o-Ps component with τ5 present in the PAL spectrum of initial MCM-41 mesoporous material in the PAL spectra of MnFe2O4-impregnated MCM-41 measured in vacuum is a result of either a strong chemical o-Ps quenching or the Ps inhibition effects. The intensity I4 of the medium-lived component initially increases, reaching a maximum value for the sample with minimum manganese ferrite content, and then decreases monotonically. Analogous dependence for the intensity I3 of the shortest-lived component shows a maximum at higher MnFe2O4 content. Filling of open pores present in the studied nanocomposites by N2 or O2 at ambient pressure causes partial reappearance of the τ4 and τ5 components, except a sample with maximum ferrite content. The lifetimes of these components measured in O2 are shortened in comparison to that observed in N2 because of paramagnetic quenching. Anti-inhibition and anti-quenching effects of atmospheric gases observed in the MnFe2O4/MCM-41 samples are a result of neutralization of some surface active centers acting as inhibitors and weakening of pick-off annihilation mechanism, respectively.
3
Content available remote Microstructure and electrical conductivity of titanium irradiated with swift heavy ions
100%
Budzyński P. , Kamiński M. , Surowiec Z.
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tom R. 92, nr 8
155--157
EN
Radiation damage caused by heavy ions may induce changes in the surface topography, crystalline structure, and electrical conductivity of irradiated materials. Titanium was irradiated with 130 MeV xenon ions and 260 MeV krypton ions at a fluence of 1, 3, and 5×1014 ions/cm2. The irradiation altered the surface topography of the sample, caused transformation of the α phase into the fcc phase, and reduced electrical conductivity with the increasing irradiation fluence.
PL
Uszkodzenia radiacyjne wywołane ciężkimi jonami mogą powodować zmiany topografii powierzchni oraz zmiany w strukturze krystalicznej i przewodności elektrycznej napromieniowanych materiałów. Tytan napromieniowano jonami Xe o energii 130 MeV i jonami kryptonu o energii 260 MeV. Doza napromieniowanych jonów była równa 1, 3 i 5×1014 jonów/cm2. Napromieniowanie zmienia: topografię powierzchni próbki, powoduje transformacje fazy α w fazę fcc oraz obniża przewodność elektryczną wraz ze wzrostem dozy napromieniowania.
4
Content available Synthesis and characterization of iron oxide magnetic nanoparticles
100%
Surowiec Z. , Budzyński M. , Durak K. , Czernel G.
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2017
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tom Vol. 62, No. 2
73--77
EN
Small particles of magnetite, i.e. 7.5, 13.4 and 14.1 nm in diameter, were obtained by the method of co-precipitation. The crystal structure and size distributions were determined by means of transmission electron microscopy and X-ray diffraction. The magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy within the temperature range from 3 K to room temperature (RT). The Mössbauer study of magnetic nanoparticles reveals relaxation behaviour related to the existence of the superparamagnetic phase. The blocking temperature depends on the sizes of the nanoparticles and the ammonia concentration.
5
Content available Positron annihilation studies of mesoporous iron modified MCM-41 silica
100%
Wiertel M. , Surowiec Z. , Budzyński M. , Gac W.
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2013
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tom Vol. 58, No. 1
245-250
EN
MCM-41 silica materials modified by iron incorporation in the stage of its synthesis were investigated. The aim of the studies was determination of the nature of iron species and the influence of its content on the structural changes of materials and following the changes of their properties. For this purpose, the N2 sorption/desorption method and positron annihilation lifetime spectroscopy (PALS) were used. Disappearance of the longest-lived ortho-positronium (o-Ps) component (tau5) present in the PALS spectra of the initial MCM-41 material in the spectra of Fe-modified MCM-41 measured in vacuum is a result of a strong chemical o-Ps quenching and/or the Ps inhibition mechanism. Filling of pores by air or N2 at ambient pressure causes reappearance of the (tau5) component with lifetime shortened in comparison to that observed in vacuum for pure MCM-41 to the extent which can be explained by usual paramagnetic quenching in air. In contrary to the tendency observed for (tau5) lifetime which is practically independent of Fe content, the relevant intensity I5 monotonically decreases. This fact suggests that only inhibition of Ps formation occurs for the samples in air. Observed anti-quenching effect of air seems to be a result of competition of two processes : neutralization of surface active centres acting as inhibitors and considerably weaker paramagnetic quenching by O2 molecules.
6
Content available Synthesis and characterization of iron - cobalt nanoparticles embedded in mesoporous silica MCM - 41
100%
Surowiec Z. , Wiertel M. , Budzyński M. , Gac W.
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2013
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tom Vol. 58, No. 1
87-92
EN
Fe1.xCox/MCM-41 nanocomposite materials were prepared by wet impregnation of the silica mesoporous support with aqueous solution of iron and cobalt salt mixtures. Samples, after calcination, were reduced at 573 K in order to obtain homogeneous distribution of (Fe-Co)3O4 oxide species over the MCM-41 support. Bimetallic systems were achieved through high temperature reduction, carried out at 1073 K. The temperature-programmed reduction studies indicated complex nature of the oxide species. The phase analysis of the obtained samples after low temperature reduction process carried out by means of X-ray diffraction method and using 57Fe Mossbauer spectroscopy revealed the presence of nanostructured magnetite- and maghemite-like phases. The samples with higher cobalt contents (x . 0.2) contained additionally bimetallic phases. The complete transformation of oxide phases to bimetallic Fe-Co systems occurred during reduction process in hydrogen at 1073 K. It was observed that high temperature processing caused partial transformation of highly dispersed iron oxide nanocrystallites into fayalite species embedded in the silica walls.
7
Content available Structural and magnetic properties of Sc(Fe1-xCux)2 compounds studied by means of Mössbauer effect and neutron diffraction
100%
Wiertel M. , Surowiec Z. , Budzyński M. , Sarzyński J.
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2013
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tom Vol. 58, No. 1
173-178
EN
The subject of the investigations were quasibinary Sc(Fe1-xCux)2 Laves phases in which structural and magnetic properties depend on replacement of Fe atoms by Cu atoms. Powder X-ray diffraction and neutron diffraction measurements carried out at room temperature revealed that samples were a mixture of two phases: the quasibinary Sc(Fe1-xCux)2 compounds with cubic C15 structure and ScCu2 with tetragonal structure. 57Fe Mossbauer spectroscopy revealed that the Sc(Fe1-xCux)2 compounds are ferrimagnetic up to an actual concentration xact less than 0.30. A decreasing of mean values of hyperfine magnetic fields was observed. On the basis of analysis of the neutron diffraction spectra the mean values of Fe magnetic moments were determined, considering the component connected with the quasibinary Sc(Fe1-xCux)2 phases. These moments change from 1.45(29) �ĘB in the Sc(Fe0.92Cu0.08)2 to 1.18(32)mi B in Sc(Fe0.72Cu0.28)2 phase at 8 K. From the results of independent hyperfine magnetic field on 57Fe probes and magnetic Fe moments measurements, the hyperfine coupling constant in quasibinary ferrimagnetic Sc(Fe1.xCux)2 phases is estimated as equal to 13 T/mi B at room temperature.
8
Content available Mössbauer investigations of Mn2-xFexP0.5As0.5
88%
Mitsiuk V. I. , Tkachenka T. M. , Budzyński M. , Surowiec Z. , Valkov V. I.
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2013
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tom Vol. 58, No. 1
169-172
EN
Magnetic and Mossbauer measurements were performed for Mn2.xFexP0.5As0.5, 0.5 less-than or equal to x less-than or equal to 1.0. It was shown that with decreasing Fe content magnetic interaction significantly weakens. Low temperature magnetic structure could be explained as a superposition of ferromagnetic and antiferromagnetic contributions to the whole magnetic moment of the alloy.
9
Content available An application of Mössbauer spectroscopy in the studies of iron - molybdenum silica mesoporous materials
88%
Surowiec Z. , Wiertel M. , Marynowska A. , Gac W. , Zawadzki W.
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2013
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tom Vol. 58, No. 1
137-141
EN
Iron-molybdenum silica mesoporous materials were obtained by the application of direct hydrothermal method. Four samples with different metal contents relative to silica were investigated. Incorporation of iron and molybdenum ions in the synthesis stage led to structural changes of the MCM-41 support. With an increasing metals content, cylindrical pores of silica initially transformed into bottle-ink type pores, and then into the slit-like ones. Mössbauer spectroscopy investigations indicated that Fe ions were embedded in the silica walls and then formed nanosized crystallites in the pores. Superparamagnetic phase was observed at liquid nitrogen temperature.
10
Content available Study of B8 - type solid solutions of Al and Si in manganese antimonide
88%
Budzyński M. , Mitsiuk V. I. , Ryzhkovskii V. M. , Surowiec Z. , Tkachenka T. M.
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2013
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tom Vol. 58, No. 1
149-152
EN
The Mn1.1Sb1.yAly (0 less-than or equal to y less-than or equal to 0.2) and Mn1.1Sb1-ySiy (0 less-than or equal to y less-than or equal to 0.1) solid solutions with the B8-type of crystal structure were obtained. The magnetic measurement revealed that the partial substitution of Sb atoms by Al or Si practically do not affect the specific magnetization and Curie temperatures. Mossbauer data showed the local redistribution of atoms in solid solutions by comparison with that in the parent Mn1.10Sb.
11
Content available Hyperfine interactions and irreversible magnetic behavior in multiferroic Aurivillius compounds
75%
Jartych E. , Gąska K. , Przewoźnik J. , Kapusta C. , Lisińska-Czekaj A. , Czekaj D. , Surowiec Z.
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2013
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tom Vol. 58, No. 1
47-51
EN
In this work investigations of structure and magnetic properties of conventionally sintered Bim+1Ti3Fem.3O3m+3 compounds with 4 less-than or equal to m less-than or equal to 8 were performed using X-ray diffraction, Mossbauer spectroscopy and vibrating sample magnetometry. Room-temperature Mossbauer spectra of the compounds correspond to a paramagnetic state, however, low temperature measurements (80 K) reveal the antiferromagnetic state with a residual paramagnetic phase. Temperature dependencies of magnetic susceptibility,chi sigma(T), provided magnetic ordering temperatures and revealed an irreversibility in Aurivillius compounds with m greater-than or equal to 5. In the case of Bi5Ti3FeO15 compound the chi sigma(T) dependence shows a paramagnetic behavior down to 2 K. The Bi6Ti3Fe2O18 compound reveals a magnetic ordering at 11 K. The compounds with m = 6-8 show a magnetic ordering at temperatures higher than 200 K. Highly irreversible character of their temperature dependencies of chi sigma indicates a spin-glass type disordered magnetism with frustration due to a random distribution of Fe on Ti at their sites.
12
Content available Structure and Magnetic Properties of Bi5Ti3FeO15 Ceramics Prepared by Sintering, Mechanical Activation and Edamm Process. A Comparative Study
63%
Jartych E. , Pikula T. , Mazurek M. , Franus W. , Lisińska-Czekaj A. , Czekaj D. , Oleszak D. , Surowiec Z. , Aksenczuk A. , Calka A.
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nr 2
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