Polymer-derived SiCNFe ceramics is a prospective material that can be used as soft magnets in MEM... more Polymer-derived SiCNFe ceramics is a prospective material that can be used as soft magnets in MEMS magnetic applications. The optimal synthesis process and low-cost appropriate microfabrication should be developed for best result. Homogeneous and uniform magnetic material is required for developing such MEMS devices. Therefore, the knowledge of exact composition of SiCNFe ceramics is very important for the microfabrication of magnetic MEMS devices. The Mössbauer spectrum of SiCN ceramics, doped with Fe (III) ions, and annealed at 1100 °C, was investigated at room temperature to accurately establish the phase composition of Fe-containing magnetic nanoparticles, which were formed in this material at pyrolysis and which determine their magnetic properties. The analysis of Mössbauer data shows the formation of several Fe-containing magnetic nanoparticles in SiCN/Fe ceramics, such as α-Fe, FexSiyCz, traces of Fe-N and paramagnetic Fe3+ with octahedral oxygen environment. The presence of ...
This article shows the success of using the chemical reduction method, the polyol thermolytic pro... more This article shows the success of using the chemical reduction method, the polyol thermolytic process, the sonochemistry method, and the hybrid sonochemistry/polyol process method to design iron-based magnetically active composite nanomaterials in a hyperbranched polyester polyol matrix. Four samples were obtained and characterized by transmission and scanning electron microscopy, infrared spectroscopy and thermogravimetry. In all cases, the hyperbranched polymer is an excellent stabilizer of the iron and iron oxides nanophase. In addition, during the thermolytic process and hybrid method, the branched polyol exhibits the properties of a good reducing agent. The use of various approaches to the synthesis of iron nanoparticles in a branched polyester polyol matrix makes it possible to control the composition, geometry, dispersity, and size of the iron-based nanophase and to create new promising materials with colloidal stability, low hemolytic activity, and good magnetic properties. ...
Ternary potassium-iron sulfide, KFeS2, belongs to the family of highly anisotropic quasi-one-dime... more Ternary potassium-iron sulfide, KFeS2, belongs to the family of highly anisotropic quasi-one-dimensional antiferromagnets with unusual “anti-Curie–Weiss” susceptibility, quasi-linearly growing with a rising temperature up to 700 K, an almost vanishing magnetic contribution to the specific heat, drastically reduced magnetic moment, etc. While some of the measurements can be satisfactorily described, the deficiency of the entropy changes upon the magnetic transition and the spin state of the iron ion remains a challenge for the further understanding of magnetism. In this work, high-quality single-crystalline samples of KFeS2 were grown by the Bridgman method, and their stoichiometry, crystal structure, and absence of alien magnetic phases were checked, utilizing wave-length dispersive X-ray electron-probe microanalysis, powder X-ray diffraction, and 57Fe Mössbauer spectroscopy, respectively. An ab initio approach was developed to calculate the thermodynamic properties of KFeS2. The el...
Chalcogenide minerals exhibit a fascinating variety of crystal-chemistry and physical properties ... more Chalcogenide minerals exhibit a fascinating variety of crystal-chemistry and physical properties that is of both scientific interest and potential practical application value. The role of ternary chalcogenide CuFeS2 (referred to as chalcopyrite) should be specially emphasized. On the one hand, chalcopyrite is known as a very important commercial source of copper ore. On the other hand, chalcopyrite-based chalcogenide group of minerals is considered as a perspective generation of solar cells. This is due to their high optical absorption coefficient when compared with known materials, with their energy band gap varied within the range of 0.8-3.5 eV by controlling chemical composition. This is also the reason for these materials finding wider application in optoelectronic devices. From scientific point of view, CuFeS2 has drawn strong interest as an antiferromagnetic semiconductor. One of known specific features of CuFeS2 is the occurrence of polymer-like structure consisting of –Cu–S–...
Single photon, emitted in a transition between two states, has a frequency distribution of intens... more Single photon, emitted in a transition between two states, has a frequency distribution of intensity, which is given by Lorentzian if the transition is only naturally broadened and the period of observation T is long compared to the lifetime T 1 of the excited state. However, when the observation time T is short or comparable to T 1 , the frequency spectrum is appreciably broadened. If only the delayed part of the emitted radiation field is detected, then the radiation spectrum does not change. However, if the radiation field is transmitted through a resonant absorber and then detected, the absorption/transmission spectrum of the delayed radiation field is narrowed. We show that this narrowing is due to the interference of the spectral components of the field. Experimental spectra of absorption of Mössbauer radiation, obtained by coincidence technique, confirm this conclusion.
The magnetic specific heat of RbFeSe 2 and the spin state of Fe 3+ ions in the compound have been... more The magnetic specific heat of RbFeSe 2 and the spin state of Fe 3+ ions in the compound have been studied. Phonon dispersion and phonon density of states (PDOS), element specific and total, were evaluated from firstprinciples calculations. It is shown that iron atoms in quasi-one-dimensional chains have dramatically different vibrational properties against Rb and Se atoms: the Fe PDOS is mostly concentrated within two Einstein-like optical phonon peaks at high frequencies. Analysis of our Mössbauer data for RbFeSe 2 , utilizing the calculated Fe PDOS as well as our optical absorption measurements, have shown full agreement with the location of the high-frequency optical-type lattice vibrations within the FeSe 4 tetrahedra. The calculated PDOS was utilized to evaluate the lattice contribution to the specific heat. The phonon heat capacity has been used to evaluate the magnetic specific heat of the quasi-one-dimensional antiferromagnetically correlated Fe 3+ ion chains in RbFeSe 2. An intermediate spin state S = 3/2 has been found most closely relevant to our magnetic entropy analysis for Fe 3+ ions in RbFeSe 2 .
An efficient technique for producing a periodic sequence of short pulses of recoilless γradiation... more An efficient technique for producing a periodic sequence of short pulses of recoilless γradiation via its transmission through an optically thick vibrating resonant absorber was demonstrated recently [Nature, 508, 80 (2014)]. In this paper we extend the theoretical analysis to a case of multiple absorbers. We analyze a simple physical model describing control of spectral content of a frequency modulated γ-radiation by adjusting the amplitudes and initial phases of spectral components, using the resonant absorption and dispersion in a set of several sequentially placed resonant absorbers. On the basis of analytical solutions, we determine the ultimate possibilities of the proposed technique.
Single crystals of the ternary iron selenide RbFeSe 2 have been investigated by means of x-ray di... more Single crystals of the ternary iron selenide RbFeSe 2 have been investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, and specific-heat measurements as well as by Mössbauer spectroscopy. Built up from linear chains of edge-sharing FeSe 4 tetrahedra, RbFeSe 2 represents a quasi-one-dimensional antiferromagnet. Below T N = 248 K three-dimensional antiferromagnetic collinear magnetic order sets in, with the magnetic moments oriented perpendicularly to the chain direction. The hyperfine fields determined from our Mössbauer studies reveal strongly reduced magnetic moments. The high-temperature susceptibility data of RbFeSe 2 suggest a one-dimensional metallic character along the chains.
We measure subnanometer displacements of thin samples vibrated by piezotransducer. Samples contai... more We measure subnanometer displacements of thin samples vibrated by piezotransducer. Samples contain 57 Fe nuclei, which are exposed to 14.4 keV γ-radiation. Vibration produces sidebands from a single absorption line of the sample. The sideband intensities depend on the vibration amplitude and its distribution along the sample. We developed a model of this distribution, which adequately describes the spectra of powder and stainless steel (SS) absorbers. We propose to filter γ-radiation through a small round hole in the lead mask, placed before the absorber. In this case only a small spot of the vibrated absorber is observed. We found for SS foil that nuclei, exposed to γ-radiation in this small spot, vibrate with almost the same amplitudes whose difference does not exceed a few picometers within the irradiated area.
The ground state band structure, magnetic moments, charges and population numbers of electronic s... more The ground state band structure, magnetic moments, charges and population numbers of electronic shells of Cu and Fe atoms have been calculated for chalcopyrite CuFeS 2 using density functional theory. The comparison between our calculation results and experimental data (X-ray photoemission, X-ray absorption and neutron diffraction spectroscopy) has been made. Our calculations predict a formal oxidation state for chalcopyrite as Cu 1+ Fe 3+ S 2 2-. However, the assignment of formal valence state to transition metal atoms appears to be oversimplified. It is anticipated that the valence state can be confirmed experimentally by nuclear magnetic and nuclear quadrupole resonance and Mössbauer spectroscopy methods.
Polymer-derived SiCNFe ceramics is a prospective material that can be used as soft magnets in MEM... more Polymer-derived SiCNFe ceramics is a prospective material that can be used as soft magnets in MEMS magnetic applications. The optimal synthesis process and low-cost appropriate microfabrication should be developed for best result. Homogeneous and uniform magnetic material is required for developing such MEMS devices. Therefore, the knowledge of exact composition of SiCNFe ceramics is very important for the microfabrication of magnetic MEMS devices. The Mössbauer spectrum of SiCN ceramics, doped with Fe (III) ions, and annealed at 1100 °C, was investigated at room temperature to accurately establish the phase composition of Fe-containing magnetic nanoparticles, which were formed in this material at pyrolysis and which determine their magnetic properties. The analysis of Mössbauer data shows the formation of several Fe-containing magnetic nanoparticles in SiCN/Fe ceramics, such as α-Fe, FexSiyCz, traces of Fe-N and paramagnetic Fe3+ with octahedral oxygen environment. The presence of ...
This article shows the success of using the chemical reduction method, the polyol thermolytic pro... more This article shows the success of using the chemical reduction method, the polyol thermolytic process, the sonochemistry method, and the hybrid sonochemistry/polyol process method to design iron-based magnetically active composite nanomaterials in a hyperbranched polyester polyol matrix. Four samples were obtained and characterized by transmission and scanning electron microscopy, infrared spectroscopy and thermogravimetry. In all cases, the hyperbranched polymer is an excellent stabilizer of the iron and iron oxides nanophase. In addition, during the thermolytic process and hybrid method, the branched polyol exhibits the properties of a good reducing agent. The use of various approaches to the synthesis of iron nanoparticles in a branched polyester polyol matrix makes it possible to control the composition, geometry, dispersity, and size of the iron-based nanophase and to create new promising materials with colloidal stability, low hemolytic activity, and good magnetic properties. ...
Ternary potassium-iron sulfide, KFeS2, belongs to the family of highly anisotropic quasi-one-dime... more Ternary potassium-iron sulfide, KFeS2, belongs to the family of highly anisotropic quasi-one-dimensional antiferromagnets with unusual “anti-Curie–Weiss” susceptibility, quasi-linearly growing with a rising temperature up to 700 K, an almost vanishing magnetic contribution to the specific heat, drastically reduced magnetic moment, etc. While some of the measurements can be satisfactorily described, the deficiency of the entropy changes upon the magnetic transition and the spin state of the iron ion remains a challenge for the further understanding of magnetism. In this work, high-quality single-crystalline samples of KFeS2 were grown by the Bridgman method, and their stoichiometry, crystal structure, and absence of alien magnetic phases were checked, utilizing wave-length dispersive X-ray electron-probe microanalysis, powder X-ray diffraction, and 57Fe Mössbauer spectroscopy, respectively. An ab initio approach was developed to calculate the thermodynamic properties of KFeS2. The el...
Chalcogenide minerals exhibit a fascinating variety of crystal-chemistry and physical properties ... more Chalcogenide minerals exhibit a fascinating variety of crystal-chemistry and physical properties that is of both scientific interest and potential practical application value. The role of ternary chalcogenide CuFeS2 (referred to as chalcopyrite) should be specially emphasized. On the one hand, chalcopyrite is known as a very important commercial source of copper ore. On the other hand, chalcopyrite-based chalcogenide group of minerals is considered as a perspective generation of solar cells. This is due to their high optical absorption coefficient when compared with known materials, with their energy band gap varied within the range of 0.8-3.5 eV by controlling chemical composition. This is also the reason for these materials finding wider application in optoelectronic devices. From scientific point of view, CuFeS2 has drawn strong interest as an antiferromagnetic semiconductor. One of known specific features of CuFeS2 is the occurrence of polymer-like structure consisting of –Cu–S–...
Single photon, emitted in a transition between two states, has a frequency distribution of intens... more Single photon, emitted in a transition between two states, has a frequency distribution of intensity, which is given by Lorentzian if the transition is only naturally broadened and the period of observation T is long compared to the lifetime T 1 of the excited state. However, when the observation time T is short or comparable to T 1 , the frequency spectrum is appreciably broadened. If only the delayed part of the emitted radiation field is detected, then the radiation spectrum does not change. However, if the radiation field is transmitted through a resonant absorber and then detected, the absorption/transmission spectrum of the delayed radiation field is narrowed. We show that this narrowing is due to the interference of the spectral components of the field. Experimental spectra of absorption of Mössbauer radiation, obtained by coincidence technique, confirm this conclusion.
The magnetic specific heat of RbFeSe 2 and the spin state of Fe 3+ ions in the compound have been... more The magnetic specific heat of RbFeSe 2 and the spin state of Fe 3+ ions in the compound have been studied. Phonon dispersion and phonon density of states (PDOS), element specific and total, were evaluated from firstprinciples calculations. It is shown that iron atoms in quasi-one-dimensional chains have dramatically different vibrational properties against Rb and Se atoms: the Fe PDOS is mostly concentrated within two Einstein-like optical phonon peaks at high frequencies. Analysis of our Mössbauer data for RbFeSe 2 , utilizing the calculated Fe PDOS as well as our optical absorption measurements, have shown full agreement with the location of the high-frequency optical-type lattice vibrations within the FeSe 4 tetrahedra. The calculated PDOS was utilized to evaluate the lattice contribution to the specific heat. The phonon heat capacity has been used to evaluate the magnetic specific heat of the quasi-one-dimensional antiferromagnetically correlated Fe 3+ ion chains in RbFeSe 2. An intermediate spin state S = 3/2 has been found most closely relevant to our magnetic entropy analysis for Fe 3+ ions in RbFeSe 2 .
An efficient technique for producing a periodic sequence of short pulses of recoilless γradiation... more An efficient technique for producing a periodic sequence of short pulses of recoilless γradiation via its transmission through an optically thick vibrating resonant absorber was demonstrated recently [Nature, 508, 80 (2014)]. In this paper we extend the theoretical analysis to a case of multiple absorbers. We analyze a simple physical model describing control of spectral content of a frequency modulated γ-radiation by adjusting the amplitudes and initial phases of spectral components, using the resonant absorption and dispersion in a set of several sequentially placed resonant absorbers. On the basis of analytical solutions, we determine the ultimate possibilities of the proposed technique.
Single crystals of the ternary iron selenide RbFeSe 2 have been investigated by means of x-ray di... more Single crystals of the ternary iron selenide RbFeSe 2 have been investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, and specific-heat measurements as well as by Mössbauer spectroscopy. Built up from linear chains of edge-sharing FeSe 4 tetrahedra, RbFeSe 2 represents a quasi-one-dimensional antiferromagnet. Below T N = 248 K three-dimensional antiferromagnetic collinear magnetic order sets in, with the magnetic moments oriented perpendicularly to the chain direction. The hyperfine fields determined from our Mössbauer studies reveal strongly reduced magnetic moments. The high-temperature susceptibility data of RbFeSe 2 suggest a one-dimensional metallic character along the chains.
We measure subnanometer displacements of thin samples vibrated by piezotransducer. Samples contai... more We measure subnanometer displacements of thin samples vibrated by piezotransducer. Samples contain 57 Fe nuclei, which are exposed to 14.4 keV γ-radiation. Vibration produces sidebands from a single absorption line of the sample. The sideband intensities depend on the vibration amplitude and its distribution along the sample. We developed a model of this distribution, which adequately describes the spectra of powder and stainless steel (SS) absorbers. We propose to filter γ-radiation through a small round hole in the lead mask, placed before the absorber. In this case only a small spot of the vibrated absorber is observed. We found for SS foil that nuclei, exposed to γ-radiation in this small spot, vibrate with almost the same amplitudes whose difference does not exceed a few picometers within the irradiated area.
The ground state band structure, magnetic moments, charges and population numbers of electronic s... more The ground state band structure, magnetic moments, charges and population numbers of electronic shells of Cu and Fe atoms have been calculated for chalcopyrite CuFeS 2 using density functional theory. The comparison between our calculation results and experimental data (X-ray photoemission, X-ray absorption and neutron diffraction spectroscopy) has been made. Our calculations predict a formal oxidation state for chalcopyrite as Cu 1+ Fe 3+ S 2 2-. However, the assignment of formal valence state to transition metal atoms appears to be oversimplified. It is anticipated that the valence state can be confirmed experimentally by nuclear magnetic and nuclear quadrupole resonance and Mössbauer spectroscopy methods.
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