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Wyszukujesz frazę "Romčević, N." wg kryterium: Autor


Wyświetlanie 1-12 z 12
Tytuł:
Preparation and Characterization of Nano Ferrites
Autorzy:
Lazarević, Z.
Jovalekić, Č.
Milutinović, A.
Romčević, M.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/1489907.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.-g
81.07.Wx
81.20.Ev
74.25.nd
Opis:
Nickel ferrite $(NiFe_2O_4)$ and manganese ferrite $(MnFe_2O_4)$ have been prepared by a soft mechanochemical route from mixture of (1) $Ni(OH)_2$ and $α-Fe_2O_3$ and (2) $Mn(OH)_2$ and $α-Fe_2O_3$ powders in a planetary ball mill. The mixture was activated for varying duration. Soft mechanochemical reaction leading to formation of the $NiFe_2O_4$ and $MnFe_2O_4$ spinel phases were followed by X-ray diffraction, Raman and infrared spectroscopy, scanning and transmission microscopy. The spinel phase formation was first observed after 4 h of milling (case 1) and after 3 h (case 2) and its formation was completed after 25 h in both cases. The synthesized $NiFe_2O_4$ and $MnFe_2O_4$ ferrites have a nanocrystalline structure with a crystallite size of about 30 and 40 nm for cases (1) and (2), respectively. There are five Raman and four IR active modes. In order to understand better the whole process of phase formation, the Mössbauer measurements were done.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 682-686
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synthesis by Wet Chemical Method and Characterization of Nanocrystalline ZnO Doped with $Fe_2O_3$
Autorzy:
Narkiewicz, U.
Sibera, D.
Kuryliszyn-Kudelska, I.
Kilański, L.
Dobrowolski, W.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/1812407.pdf
Data publikacji:
2008-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.-b
75.75.+a
78.67.Bf
Opis:
Nanocrystalline samples of ZnO doped with $Fe_2O_3$ were synthetized by wet chemical method. The series of ZnO nanosized samples in the wide range of $Fe_2O_3$ concentration (from 5 wt.% to 95 wt.%) was prepared by precipitation from nitrate solutions using ammonia. The phase composition of the samples was determined using X-ray diffraction measurements. The phases of hexagonal ZnO, and/or rhombohedric $Fe_2O_3$, and/or $ZnFe_2O_4$ were identified. The mean crystalline size of nanocrystals, determined with the use of Scherrer's formula, varied from 8 to 52 nm. The preliminary micro-Raman spectroscopy measurements were performed. The observed features are typical of Fe doped ZnO nanoparticles. The magnetic measurements revealed the presence of different types of magnetic behavior. For samples with high $Fe_2O_3$ contents (above 70 wt.%) the ferromagnetic ordering was observed at room temperature. For samples with lower $Fe_2O_3$ contents we observed the phenomenon of superparamagnetism above the blocking temperature.
Źródło:
Acta Physica Polonica A; 2008, 113, 6; 1695-1700
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ellipsometric Measurements of Plastically Deformed Copper
Autorzy:
Mirić, M.
Rudolf, R.
Anžel, I.
Hadžić, B.
Romčević, M.
Trajić, J.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/1795714.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.-e
78.40.Kc
68.35.Ct
Opis:
Chemically pure copper (99.99) prepared in the sample of square cross-section (10×10 $mm^{2}$) and length about 50 mm was extremely plastically deformed with the repeated application of equal channel angular pressing. Equal channel angular pressing was applied as an effective technique for producing bulk nanoscaled structures. It is well known that severe plastic deformation of metallic materials often leads to microstructure with ultrafine grains and cross-sections which remain about equal before and after deformation. Optical properties of the sample were studied using spectroscopic ellipsometry in UV-VIS range. The parameters of the sample like copper oxide and surface roughness overlayer were calculated using two-film model together with the Bruggeman effective medium approximation.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 715-717
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Raman Spectra of CdTe/ZnTe Self Assembled Quantum Dots
Autorzy:
Romčević, N.
Romčević, M.
Kostić, R.
Stojanović, D.
Abolmasov, B.
Karczewski, G.
Galazka, R.
Powiązania:
https://bibliotekanauki.pl/articles/1807840.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.22.-m
78.30.Fs
78.55.Et
Opis:
In this paper we present Raman scattering and photoluminescence spectra measured on CdTe/ZnTe self assembled quantum dots. The photoluminescence spectrum has shown two main emission peaks, both connected with existing of quantum dots. One presents direct deexcitation to ground state and the other is optical phonon (οmega = 207.3 $cm^{-1}$)-assisted deexcitation. The registered multiphonon emission process depends on temperature. At low temperature phonon spectra shows line at 450 $cm^{-1}$ (TA + 2LO in ZnTe) and 595 $cm^{-1}$ (2LO + TO(Γ) in ZnTe).
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 88-90
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization of Barium Titanate Ceramic Powders by Raman Spectroscopy
Autorzy:
Lazarević, Z.
Romčević, N.
Vijatović, M.
Paunović, N.
Romčević, M.
Stojanović, B.
Dohčević-Mitrović, Z.
Powiązania:
https://bibliotekanauki.pl/articles/1808060.pdf
Data publikacji:
2009-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.84.-s
81.07.Bc
81.20.Ev
83.85.Hf
Opis:
Barium titanate, $BaTiO_3$ ceramic powders were prepared by mechanochemical synthesis and by the Pechini method. A powder mixture of BaO and $TiO_2$ was treated in a planetary ball mill in an air atmosphere for up to 1 h, using zirconium oxide vial and zirconium oxide balls as the milling medium. After 60 min $BaTiO_3$ phase was formed. In both ways $BaTiO_3$ ceramics were sintered after 2 h on 1300°C without pre-calcinations step. The heating rate was 10°C $\text{min}^{-1}$. The formation of phase and crystal structure of $BaTiO_3$ was approved by X-ray diffraction analysis and the Raman spectroscopy. The morphology and microstructure of obtained powders were examined by scanning electron microscopy method. Sharp phase transition from ferroelectric to paraelectric state was observed. The hysteresis loop is very well performed with regular sharp characteristic of ferroelectric materials.
Źródło:
Acta Physica Polonica A; 2009, 115, 4; 808-810
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Far-Infrared Study of DX-Like Centers in Pb$\text{}_{0.95}$Mn$\text{}_{0.05}$Te(Ga)
Autorzy:
Stojanović, D.
Trajić, J.
Hadžić, B.
Romčević, M.
Ivanchik, I. I.
Khokhlov, D. R.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/2047857.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
78.20.-e
63.20.Pw
Opis:
We present far-infrared reflection spectra of Pb$\text{}_{0.95}$Mn$\text{}_{0.05}$Te single crystal doped with gallium between 10 and 300 K. The analysis of the far-infrared reflection spectra was made by a fitting procedure based on the model of coupled oscillators. Together with the strong plasmon-phonon coupling we obtain three local modes of gallium at about 122 cm$\text{}^{-1}$, 166 cm$\text{}^{-1}$, and 192 cm$\text{}^{-1}$. The position of these modes depends on impurity center charge, and their intensity depends on temperature.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 959-962
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Scattering from ZnO(Fe) Nanoparticles
Autorzy:
Romčević, N.
Kostić, R.
Romčević, M.
Hadžić, B.
Kuryliszyn-Kudelska, I.
Dobrowolski, W.
Narkiewicz, U.
Sibera, D.
Powiązania:
https://bibliotekanauki.pl/articles/1811980.pdf
Data publikacji:
2008-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.30.Fs
78.67.-n
Opis:
Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine composition of the samples (ZnO, Fe₂O₃, ZnFe₂O₄) and the mean crystalline size (8-52 nm). In this paper we report the experimental spectra of the Raman scattering (from 200 to $1600 cm^{-1}$). Main characteristics of experimental Raman spectrum in 200 to $1600 cm^{-1}$ spectral region are: sharp peak at $436 cm^{-1}$ and broad two-phonon structure at ≈ $1150 cm^{-1}, typical of ZnO;broad structure below $700 cm^{-1}$ that has different position and shape in case of ZnFe₂O₄ or Fe₂O₃ nanoparticles.
Źródło:
Acta Physica Polonica A; 2008, 114, 5; 1323-1328
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nanocrystalline ZnO Doped with Fe$\text{}_{2}$O$\text{}_{3}$ - Magnetic and Structural Properties
Autorzy:
Kuryliszyn-Kudelska, I.
Hadžić, B.
Sibera, D.
Kilanski, L.
Romčević, N.
Romčević, M.
Narkiewicz, U.
Dobrowolski, W.
Powiązania:
https://bibliotekanauki.pl/articles/2048113.pdf
Data publikacji:
2011-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Tt
81.05.Dz
75.50.Lk
75.50.Vv
Opis:
We have studied the magnetic properties of ZnO nanocrystals doped with Fe$\text{}_{2}$O$\text{}_{3}$ in the magnetic dopant range from 5 to 70 wt%. The nanocrystals were synthesized by wet chemical method. The detailed structural characterization was performed by means of X-ray diffraction and micro-Raman spectroscopy measurements. The results of systematic measurements of magnetic AC susceptibility as a function of temperature and frequency are presented. We observed different types of magnetic behavior. For ZnO samples doped with low content of Fe$\text{}_{2}$O$\text{}_{3}$, the results of low-field AC susceptibility are satisfactorily explained by superparamagnetic model including inter-particle interactions. With the increase of magnetic Fe$\text{}_{2}$O$\text{}_{3}$ content, the spin-glass-like behavior is observed.
Źródło:
Acta Physica Polonica A; 2011, 119, 5; 689-691
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Properties of Plastically Deformed Copper
Autorzy:
Trajić, J.
Rudolf, R.
Anžel, I.
Romčević, M.
Lazarević, N.
Mirić, M.
Lazarević, Z.
Hadžić, B.
Romčević, N.
Powiązania:
https://bibliotekanauki.pl/articles/1537910.pdf
Data publikacji:
2010-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.-e
78.30.j
78.40.kc
Opis:
Pure copper (99.99), prepared in the sample of square cross-section (10 × 10 $mm^{2}$) and length about 50 mm, was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing (ECAP). ECAP was applied as an effective technique for producing bulk nano-scaled structures. Optical properties of the sample were investigated using Raman spectroscopy. Two types of lines: narrow (with width of ≈ 7 $cm^{-1}$) and wide ( ≈ 40 $cm^{-1}$) are registered. Existence of two types of lines indicates that in the specimen exists nano-sized crystal structures of both Cu and CuO related with three dimensional amorphous boundary spaces, which indicates that plastic deformation of the sample did not lead to total amorphisation of the specimen.
Źródło:
Acta Physica Polonica A; 2010, 117, 5; 791-793
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical and Magnetic Properties of PbTe(Ni)
Autorzy:
Romčević, N.
Trajić, J.
Romčević, M.
Stojanović, D.
Kuznetsova, T.
Khokhlov, D.
Dobrowolski, W.
Rudolf, R.
Anžel, I.
Powiązania:
https://bibliotekanauki.pl/articles/1808059.pdf
Data publikacji:
2009-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
63.20.Kr
78.30.-j
Opis:
Far-infrared and magnetic properties of Ni doped PbTe ($Z_Ni$ = 1× $10^{19}$ at./$cm^{3}$) single crystal are investigated in a broad range of temperature and magnetic fields. Far-infrared reflection spectra were analyzed using a fitting procedure based on the modified plasmon-two phonon interaction model. Together with the strong plasmon-two longitudinal optical phonon coupling we obtained a local mode of Ni at about 180 $cm^{-1}$. This mode intensity depends on temperature. Magnetic measurements shows that PbTe alloys doped with Ni reveals weak ferromagnetic interaction between magnetic ions.
Źródło:
Acta Physica Polonica A; 2009, 115, 4; 805-807
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Low-Frequency Raman Scattering from ZnO(Fe) Nanoparticles
Autorzy:
Kostić, R.
Romčević, N.
Romčević, M.
Hadžić, B.
Rudolf, R.
Kuryliszyn-Kudelska, I.
Dobrowolski, W.
Narkiewicz, U.
Sibera, D.
Powiązania:
https://bibliotekanauki.pl/articles/1807817.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
78.67.-n
Opis:
Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine the sample composition and the mean crystalline size. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum aproximation, which considers nanoparticle as homogeneous elastic sphere.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 65-67
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Spectroscopy of Multiphonon Emission Process in Ni-Doped PbTe
Autorzy:
Romčević, N.
Trajić, J.
Hadžić, B.
Romčević, M.
Stojanović, D.
Lazarević, Z.
Kuznetsova, T.
Khokhlov, D.
Rudolf, R.
Anžel, I.
Powiązania:
https://bibliotekanauki.pl/articles/1807841.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.28.+d
63.20.-e
78.30.-j
Opis:
In this paper, we present room temperature unpolarized Raman scattering spectra of Ni doped PbTe single crystal sample. Crystal of PbTe(Ni) was grown by the Bridgman method. The Ni concentration in the sample used here was 1× $10^{19}$ at./$cm^{3}$. Well resolved peaks appear at about 126, 143, 181, 362 and 724 $cm^{-1}$. The modes at 126 and 143 $cm^{-1}$, which are also observed in other telluride compounds, originate from vibrations in $TeO_2$. We assume that the mode at about 181 $cm^{-1}$ is connected to excitations of a local phonon mode in the vicinity of an impurity atom (donor $Ni^{3+}$ state). Modes at about 362 $cm^{-1}$ and 724 $cm^{-1}$ are the second and fourth harmonic of a local phonon mode, registered here due to multiphonon emission.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 91-92
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-12 z 12

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