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1
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Influence of annealing temperature on structural and magnetic properties of MnFe2O4nanoparticles

100%
Surowiec Z., Wiertel M., Gac W., Budzyński M.
Nukleonika
|
2015
|
vol. 60
|
issue 1
137-141
EN
Nanoparticles of manganese ferrite were obtained by the impregnation of highly ordered mesoporous MCM-41 silica support. The investigated sample contained 20% wt. Fe. The obtained nanocrystallites were strongly dispersed in silica matrix and their size was about 2 nm. The sample annealing at 500°C led to increase of particle size to about 5 nm. The Mössbauer spectroscopy investigations performed at room temperature show on occurrence of MnFe2O4 nanoparticle in superparamagnetic state for the sample annealed in all temperatures. The coexistence of superparamagnetic and ferromagnetic phase was observed at liquid nitrogen temperature. The sample annealed at 400°C and 500°C has bigger manganese ferrite particle and better crystallized structure. One can assign them the discrete hyperfine magnetic field components.
2
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Magnetic and structural properties of Sc(Fe1−xSix)2Laves phases studied by Mössbauer spectroscopy and neutron diffraction

88%
Wiertel M., Surowiec Z., Budzyński M., Sarzyński J., Beskrovnyi A. I.
Nukleonika
|
2015
|
vol. 60
|
issue 1
155-160
EN
The aim of the presented paper is to study an influence of replacement of Fe atoms by Si atoms in quasibinary Sc(Fe1−xSix)2 Laves phases on their structural and magnetic properties. Powder X-ray diffraction (XRD) and neutron diffraction (ND) measurements carried out at different temperatures from 4.3 K up to about 700 K revealed that samples were single phase with cubic C15 structure for Si concentration x from 0.05 to 0.20 and hexagonal C14 structure for higher concentration. The results of 57Fe Mössbauer measurements showed that the Sc(Fe1−xSix)2 compounds with x ≤ 0.30 are ferrimagnetic at 4.3 K. At temperature 80 K in the samples with x = 0.20 and 0.30, a magnetic cluster spin-glass state has been observed, as ferrimagnetic long-range order disappears. Such picture was supported by the results of ND measurements carried out at 8 K, which confirmed the lack of long-range order for x above 0.10 and an occurrence of hyperfine field distributions in the corresponding Mössbauer spectra. At room temperature, samples with x ≥ 0.20 became paramagnetic. A substitution of Si atoms for Fe ones leads to a decreasing of mean values of hyperfine magnetic fields in samples under investigation. From the neutron diffraction pattern analysis of Sc(Fe0.90Si0.10)2Fe magnetic moment was determined as to be equal to 1.5 μB at 8 K. Combining this result with a value of hyperfine magnetic field on 57Fe probes, the hyperfine coupling constant A in Sc(Fe0.90Cu0.10)2 phases is estimated at about 11.6 T/μB at 8 K.
3
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The study of crystal and magnetic properties of MnNi0.85Fe0.15Ge

76%
Budzyński M., Valkov V. I., Golovchan A. V., Mitsiuk V. I., Sivachenko A. P., Surowiec Z., Tkachenka T. M.
Nukleonika
|
2015
|
vol. 60
|
issue 1
11-14
EN
Magnetic and Mössbauer measurements were performed for MnNi0.85Fe0.15Ge. The Mössbauer data indicate that Fe atoms in MnNi0.85Fe0.15Ge are randomly distributed over two types of metal sites in hexagonal structure. At 77 K, the hyperfine magnetic fields at Fe located in different crystal sites have similar values of about 12.7 and 12.3 T. The random site distribution of the iron atoms in the non-magnetic hexagonal phase at high temperatures is confirmed by the theoretical calculations in fully relativistic Korringa –Kohn –Rostoker (KKR) method.
4
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Mössbauer study of treated Nd2Fe14B

76%
Budzyński M., Constantin V. C., Popescu A.-M. J., Surowiec Z., Tkachenka T. M., Yanushkevich K. I.
Nukleonika
|
2015
|
vol. 60
|
issue 1
7-10
EN
The Nd2Fe14B cylindrical magnets were treated with water solutions of alkali, acid, and salt. Mössbauer spectroscopy was applied to study the composition and properties of the surface material of the treated magnets. It is shown that the main phase of the permanent Nd2Fe14B magnet partly decomposes. The released α-Nd at the grain boundaries interacts with water and forms neodymium hydroxide matrix, and the released Fe diffuses into it. The presence of Fe-Nd(OH)3 is reflected in the paramagnet doublet in the Mössbauer spectra of treated neodymium magnets.
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