ZnCoO:H and ZnCoAlO:H films were synthesized by radio frequency magnetron sputtering in a (1 - x)Ar + xH
mixed atmosphere with x = 0.2-0.5. The films contain different amounts of metallic Co ...particles (from 7.6% and higher) ~4-7 nm in size. The magnetic and magneto-optical (MO) behavior of the films was analyzed in combination with their structural data. The samples exhibit high values of magnetization (up to 377 emu/cm
) and MO response at room temperature. Two situations are considered: (1) the film magnetism is associated only with isolated metal particles and (2) magnetism is present both in the oxide matrix and in metal inclusions. It has been established that the formation mechanism of the magnetic structure of ZnO:Co
is due to the spin-polarized conduction electrons of metal particles and zinc vacancies. It was also found that in the presence of two magnetic components in the films, these components are exchange-coupled. In this case, the exchange coupling generates a high spin polarization of the films. The spin-dependent transport properties of the samples have been studied. A high value of the negative magnetoresistance of the films at room temperature (~4%) was found. This behavior was explained in terms of the giant magnetoresistance model. Thus, the ZnCoO:H and ZnCoAlO:H films with high spin polarization can be considered as sources of spin injection.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Fe3O4 nanoparticles modified with Ag were synthesized with thermal decomposition method.•Nanoparticles morphology and size do not depend on Ag concentration.•The Ag effect on nanoparticles magnetic ...properties was studied.•Strong influence of Ag on visible magnetic circular dichroism was revealed and discussed.
Effect of Ag inclusions on magnetic properties and magnetic circular dichroism (MCD) of Fe3O4 nanoparticles (NPs) in the mixed system of Fe3O4 and Ag NPs in dependence on the relative concentration of the components is presented. The samples were synthesized by the thermal decomposition of the mixture of constant concentration of Fe(NO3)3·9H2O and varied concentration of AgNO3. The synthesized powdered samples consisted of Fe3O4 and Ag NPs located very close with each other, and in the most cases the Fe3O4 NPs were bordered with the Ag nanocrystals. The Ag introducing in the samples does not effect, practically, in the Fe3O4 NPs morphology and size distribution. At the same time, Ag NPs in the powdered samples cause a decrease in the Fe3O4 NPs magnetization and shift of the blocking temperature to lower temperatures, both approximately proportional to the Ag concentration. Most significant changes are revealed in the MCD spectra in the energy region of 1.2–2.2 eV. We have discussed the influence of the Ag NPs on the MCD spectra features in terms of the charge-transfer electron transitions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The features of electronic structure of La0.7Sr0.3MnO3, Pr0.8Sr0.2MnO3, and Pr0.6Sr0.4MnO3 polycrystalline films of different thickness have been investigated using magnetic circular dichroism (MCD) ...in the range of 1.1–4.2 eV. The temperature behavior of the samples electrical resistance were also has been studied. It was found that films with high Sr content (0.3 and 0.4) act as high-temperature semiconductors, while the maximum in the temperature dependences of resistivity these films indicates the transition of the samples to the metallic state at some temperature TM-S, which is different for different sample thickness. The films with the lower Sr content (0.2) act as insulators in the used temperature range. The MCD spectra have been decomposed to the Gaussian-shaped lines, and the temperature dependence of intensity of each line has been analyzed in comparison with temperature dependence of the films magnetization and with their electric conductivity type. Different temperature behavior of the intensity of four specified Gaussian-lines was revealed for semiconductor films. In the case of insulating Pr0.8Sr0.2MnO3 samples, the intensity of three specified Gaussian lines changes with the temperature in the same way as the magnetization changed. It was established that the lanthanide (La, Pr) type does not affect the MCD spectra shape for the films with the same electrical conductivity type. Besides, the correlation between the MCD data of the films and their conductivity type was revealed. Due to the detailed analysis of the specified Gaussian lines with taking into account the well-known in the literature absorption bands, lying outside the studied spectral region, the MCD bands for the studied manganite films have been identified with electronic transitions of a different nature.
•La0.7Sr0.3MnO3, Pr0.8Sr0.2MnO3, and Pr0.6Sr0.4MnO3 films act as objects of research.•Magnetic circular dichroism (MCD) and electrical resistance of the films are studied.•Lanthanide type does not affect the MCD spectra shape for the films with the same electrical conductivity type.•MCD band of the positive sign near 2.3–2.4 eV is typical for the metallic films only.•Revealed MCD bands are identified with electronic transitions of a different nature.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Core-shell FexOy@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer spectroscopy, static ...magnetic measurements, and optical magnetic circular dichroism (MCD). FexOy@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO3)3 · 9H2O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe3O4 and γ-Fe2O3. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid FexOy@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe3O4@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the FexOy@C-Ag NPs is discussed.
Iron sulfide nanoparticles Fe
3
S
4
with the spinel-type crystal structure were synthesized by the polyol mediated process. The particle size depends on preparation conditions and varies from 9 to ...20 nm. Mössbauer data have revealed that the dominating fraction of iron ions in the 9-nm sample is in the high-spin ferric state. This implies an occurrence of the cation vacancies in nonstoichiometric greigite. The stoichiometric phase of greigite Fe
3
S
4
dominates in the 18-nm-size nanoparticles. Magnetic measurements have shown a ferrimagnetic behavior of all samples at temperatures between 78 and 300 K. The estimated value of magnetic moment of the stoichiometric greigite nanoparticles is about 3.5 μ
B
per Fe
3
S
4
unit. The Mössbauer spectra indicate a superparamagnetic behavior of small particles, and some fraction of superparamagnetic phase is observed in all samples synthesized which may be caused by the particle size distribution. The blocking temperatures of
T
B
≈ 230 and 250 K are estimated for the 9 and 14 nm particles, respectively. The Mössbauer parameters indicate a great degree of covalency in the Fe–S bonds and support the fast electron Fe
3+
⇆ Fe
2+
exchange in the B-sites of greigite. An absence of the Verwey transition at temperatures between 90 and 295 K is established supporting a semimetal type of conductivity. The temperature and magnetic field dependences of the magnetic circular dichroism (MCD) of optical spectra were measured in Fe
3
S
4
for the first time. The spectra differ substantially from that of the isostructural oxide Fe
3
O
4
. It is supposed that the MCD spectra of greigite nanoparticles result from the collective electron excitations in a wide band with superimposed peaks of the
d
–
d
transitions in Fe ions.
•ZnO and Co doped ZnO films were synthesized with RF magnetron sputtering at high H2 (≥20%) concentration in a chamber.•The Zn:Co ratio in the films was several times lower comparing to that in a ...target.•The deposited film characteristics depend strongly on the H2 concentration in a chamber.•Magnetic circular dichroism spectrum demonstrates strong changes in dependence on the H2 concentration.
ZnO and Co-doped ZnO films were synthesized by the radio frequency magnetron sputtering in mixed atmosphere of Ar + 20% O2 and Ar + 20–50% H2. The morphology, chemical composition, crystal structure, optical transmission, electrical resistance, and magnetic circular dichroism of the films were investigated. It was established that the films thickness decreased several times when Ar was partly replaced by hydrogen in the sputtering chamber. At the same time, for the Co-doped ZnO films, the increase in the relative Co content with the increasing hydrogen concentration was observed. These phenomena are explained by the formation of gaseous ZnH2 because of the hydrogen reaction with the growing films under the conditions of the high substrate temperature (450 °C) and, respectively, the decrease in the Zn component in the films. The hydrogenated Co-doped ZnO films exhibit an increase in electric conductivity and ferromagnetic behavior at room temperature. The magnetic nature of the films is explained by a combination of the intrinsic ferromagnetism (due to the formation of the Co-H-Co complex) with the inclusion of metallic Co clusters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The genome of the Kaposi sarcoma-associated herpesvirus (KSHV or HHV8) was mapped with cosmid and phage genomic libraries from the BC-1 cell line. Its nucleotide sequence was determined except for a ...3-kb region at the right end of the genome that was refractory to cloning. The BC-1 KSHV genome consists of a 140.5-kb-long unique coding region flanked by multiple G+C-rich 801-bp terminal repeat sequences. A genomic duplication that apparently arose in the parental tumor is present in this cell culture-derived strain. At least 81 ORFs, including 66 with homology to herpesvirus saimiri ORFs, and 5 internal repeat regions are present in the long unique region. The virus encodes homologs to complement-binding proteins, three cytokines (two macrophage inflammatory proteins and interleukin 6), dihydrofolate reductase, bcl-2, interferon regulatory factors, interleukin 8 receptor, neural cell adhesion molecule-like adhesin, and a D-type cyclin, as well as viral structural and metabolic proteins. Terminal repeat analysis of virus DNA from a KS lesion suggests a monoclonal expansion of KSHV in the KS tumor.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Nanoparticles of Co
1 –
x
Mg
x
Fe
2
O
4
with
x
equal to 0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been synthesized. For all values of
x
, they are nanocrystals with a cobalt ferrite structure and an ...average linear size (
nm. Based on the analysis of the Mössbauer effect spectra, the Co
2+
ions were shown to occupy only octahedral positions at all values of
x
. The experimentally obtained dependence of the nanoparticles magnetization on
x
corresponds to the dependence calculated using the Mössbauer effect data, except for the sample with
. The effective magnetic anisotropy constant estimated for 0 K from the analysis of the coercive force temperature dependences decreases from
at
to
erg/cm
3
at
and drops sharply to
erg/cm
3
at
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The simple lattice and magnetic structure, the high Néel temperature, the narrow antiferromagnetic resonance line of FeBO
3
, and the narrow electron paramagnetic resonance line of its isostructural ...diamagnetic analogs MBO
3
:Fe
3+
(M = Ga, In, Sc, Lu) make iron borate unique for investigations and applications. Iron borate is a model crystal for numerous experimental and theoretical studies, including spin crossovers and metallization at megabar pressures and many-electron effects in optics and X-ray spectroscopy. The recent works dealing with the investigation of the properties of FeBO
3
are reviewed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Fe3O4-Ag nanoparticles were synthesized by solvothermal method using different duration of the thermolysis process.•The nanoparticles morphology depends on the thermolysis ...duration.•Correlations between morphology and adsorption properties have been found.•Nanoparticles demonstrate high catalytic activity for degradation of organic dyes.
The morphology and magnetic properties as well as adsorption capacity and catalytic activity of Fe3O4-Ag nanoparticles synthesized by the solvothermal method were studied in dependence on the duration of the thermolysis process (3, 6, and 8 h). X-ray diffraction, transmission electron microscopy, and energy-dispersive spectroscopy measurements showed that the morphology of nanoparticles changed strongly as the duration of thermolysis increased. At 6 and 8 h duration, Fe3O4 nanocrystals grow and assemble into porous spherical globules with an Ag core (samples 2 and 3). These samples demonstrate high magnetization value and very low coercivity. The adsorption capacity of nanoparticles was studied with respect to two organic dyes: cationic methylene blue (MB) and anionic Congo red (CR). The particles showed preferential adsorption of the cationic dye. High catalytic activity towards four dyes: MB, methyl orange (MO), CR, and Rhodamine C (RhC) at the presence of NaBH4 is the remarkable property of these samples. The rate constant of the catalytic reaction was 1.4 min−1. Simultaneous exposure of CR and MO dyes to nanoparticles and NaBH4 caused their irreversible 100 % degradation while in the case of MB and RhC, a transition to their leuco form occurred.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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