The crystal structures and hyperfine magnetic parameters of EuFe3(BO3)4 and mixed Eu0.82La0.18Fe3(BO3)4 were studied over a wide temperature range in order to analyze correlations of the structural and magnetic features and the phase transitions in multiferroic compounds of the rare-earth iron borate family. The chemical compositions of the crystals are reported from X-ray fluorescence analysis. The crystal structures of EuFe3(BO3)4 and Eu0.82La0.18Fe3(BO3)4 were determined using single-crystal X-ray diffraction in the temperature range 25-500 K. A structural phase transition is observed in EuFe3(BO3)4 below 89 K which is related to distortions in the interatomic distances and angles. The most significant of which are for R-O, R-B, R-Fe, Fe-O and Fe-Fe distances, and the angles between the BO3 triangles and the ab plane. There is no structural phase transition in lanthanum-doped EuFe3(BO3)4 based on specific heat measurements (2.2-101.3 K) and structure analysis (25-500 K), and the temperature dependences of the interatomic distances and angles are smooth. The lengths of the superexchange paths needed for the appearance of a structural phase transition in RFe3(BO3)4 have been proposed. Negative thermal expansion is observed for both compounds below 90 K, resulting from a growth of the interatomic Fe-Fe distances in the iron chains during cooling. The largest atomic displacement parameters are observed for O atoms (O2), indicating that they have the highest mobility. The magnetic properties of EuFe3(BO3)4 and Eu0.82La0.18Fe3(BO3)4 were analyzed using Mössbauer spectroscopy in the temperature range 4.5-298 K. Néel temperatures (TN) of 34.57 (1) and 32.22 (1) K are obtained based on Mössbauer spectroscopy for the pure and doped crystals, respectively. The maximum specific heat capacity temperature dependence related to the magnetic phase transition for the doped crystal is observed at 31.2 K. A violation of the strict arrangement of antiferromagnetic ordering in the ab plane in the La-doped crystals at low temperatures is suggested. The magnetic contributions of the two structural positions of the iron ions to the Mössbauer spectra could not be distinguished in either pure and doped compounds, regardless of whether they are in the paramagnetic and antiferromagnetic regions.

One of the problems in the use of closed-cycle cryostats for applied and basic scientific research is the transmission of mechanical vibrations to the sample. This is particularly relevant for Mössbauer spectroscopy and optical research methods since vibrations lead to broadening of spectral lines. This paper presents various engineering approaches to reducing mechanical vibrations on a sample in closed-cycle cryostats, in particular for Mössbauer spectroscopy. The broadening of the spectral lines of the reference absorber, α-Fe foil, was analyzed and a comparison of the spectra of a FeBO 3 single crystal of high structural quality before and after updating the cryostat was made. The obtained results can be used to develop new cryostats or improve existing ones.

Nanowires from iron were investigated. Samples in the form of arrays of parallel threads (wires) were obtained by matrix synthesis using track membranes. Matrices with parallel pores of 100 nm were used, and the growth voltage was varied --- 0.8 V, 1 V and 1.2 V. Electron microscopic studies of the growth matrix and samples were carried out. The obtained data of Mossbauer spectroscopy and magnetometry correlate well. Thus, a comparison of the results obtained by these methods showed that with an increase in the deposition potential during the synthesis of nanowires, the misorientation angle of the magnetic moments of domains increases. It is also shown that as the deposition potential increases, the coercive force decreases. Keywords: magnetic nanowires, matrix synthesis, structure, Mossbauer spectroscopy, magnetic properties.

Iron oxide nanopowders are synthesized via chemical precipitation. It is shown that synthesis produces an iron oxide phase with a magnetite structure (either a magnetite–maghemite solid solution or a mixture of this solid solution and goethite). The sizes of the CSR and particles for the main phase are 10–20 nm. The synthesized iron oxide powders have developed surfaces, specific surface area SBET ≈ 92 and 117 m2/g, and identical fairly large specific pore volumes ( V_P_/P_0→ 0.99_ = 0.35 cm3/g). It is shown that additional in situ ultrasonic treatment of the magnetic iron oxide nanoparticles in the mother liquor results in abrupt oxidation of iron(II) ions and creates a nonmagnetic impurity phase of goethite.

The crystal growth and characterization of novel tourmaline compounds are important in fundamental and applied fields as new tourmaline species and promising piezoelectric materials. Single crystals of Ga,Ge-rich tourmalines (up to 12.43 wt % GeO2 and 11.03 wt % Ga2O3) were grown on a seed as a newly formed, up to 1.2 mm thick layer in hydrothermal solution at 650 degrees C and 100 MPa. Two crystallizing schemes were developed with quartz and corundum nutrients in the condition of a normal temperature solubility factor and with topaz and quartz nutrients using a reverse temperature solubility factor. The chemical composition and crystal structure of grown tourmalines as well as the distribution of gallium and germanium between crystallographic sites were studied by electron microprobe analysis (EMPA), single-crystal X-ray analysis (SCXRD), and Mo''ssbauer and Raman spectroscopy. The unit cell parameters and refined crystal-chemical formulae of two high-quality single-crystal samples are as follows: a = 16.0518(7) angstrom, c = 7.1874(4) angstrom, V = 1603.80(13), and X(Na0.660.34) Y(Fe1.782+Al0.5Fe0.363+Ni0.19Ti0.17) Z(Al4.91Ga1.09) T(Si4.78Ge0.94Al0.28O18) (BO3)3 V(OH)3 W[(OH)0.42O0.58]; a = 16.0083(8), c = 7.1508(4) angstrom, V = 1587.00(14), and X(Na0.170.83) Y(Fe1.312+Al1.35Fe0.273+Ni0.07) Z(Al5.43Ga0.57) T(Si5.15Ge0.55Al0.30O18) (BO3)3 V(OH)3 W[(OH)0.51O0.49]. Based on the Raman spectroscopy data, it is now possible to indicate the predominance of either divalent or trivalent cations in the Y site for tourmalines, whereas the Z site is fully occupied by trivalent cations.

Nanowires from iron were investigated. Samples in the form of arrays of parallel threads (wires) were obtained by matrix synthesis using track membranes. Matrices with parallel pores of 100 nm were used, and the growth voltage was varied - 0.8 V, 1 V and 1.2 V. Electron microscopic studies of the growth matrix and samples were carried out. The obtained data of Mössbauer spectroscopy and magnetometry correlate well. Thus, a comparison of the results obtained by these methods showed that with an increase in the deposition potential during the synthesis of nanowires, the misorientation angle of the magnetic moments of domains increases. It is also shown that as the deposition potential increases, the coercive force decreases.

Приведена общая методика оценки эффективности сложных технических объектов в области информационных технологий применительно к аудиту государственных информационных ресурсов и систем (далее — методология ИТаудита). Данная методология предназначена для использования профессиональными аудиторами, в том числе в рамках внешнего государственного аудита, контрольно-надзорной деятельности, технологического аудита, а также операторами государственных информационных систем (ГИС). Предлагаемая онтология ИТ-аудита позволяет сформировать базу знаний для подбора показателей и индикаторов эффективности из рекомендуемого набора с учетом имеющихся организационных, правовых, технологических ограничений, связанных с организацией сбора исходных данных для их оценки, а также провести аудит соответствия требованиям нормативной правовой базы по типовому набору нарушений с учетом предварительной оценки вероятности их выявления и уровня значимости. A general methodology for assessing the effectiveness of complex technical objects in the field of information technology, as applied to the audit of state information resources and systems is presented. The methodology is intended for use by professional auditors, including in the framework of external state audit, control and supervision activities, technological audits, as well as operators of state information systems. The proposed IT audit ontology allows to form a knowledge base for the selection of indicators and performance indicators from the recommended set, taking into account the existing organizational, legal, technological constraints associated with the organization of baseline data collection for their evaluation, as well as to audit compliance with the requirements of the regulatory framework for a typical set of violations, taking into account a preliminary assessment of the probability of detection and the level of significance.

Structural features of new mixed bismuth-containing samarium iron–aluminium borate single crystals Sm1−xBixFe3−yAly(BO3)4 (x = 0.05–0.07, y = 0–0.28) were studied using X-ray diffraction analysis based on aluminium content and temperature in the range 25–500 K. The crystals were grown using the solution-in-melt technique with Bi2Mo3O12 in a flux. The composition of the single crystals was analyzed using energy-dispersive X-ray fluorescence and energy-dispersive X-ray elemental analysis. Temperature dependencies of Sm1−xBixFe3−yAly(BO3)4 unit-cell parameters were studied. Negative thermal expansion was identified below 100 K and represented by characteristic surfaces of the thermal expansion tensor. (Sm,Bi)–O, (Sm,Bi)–(Fe,Al), (Fe,Al)–(Fe,Al), and (Fe,Al)–O interatomic distances decreased with the addition of aluminium atoms. An increase in the (Fe,Al)–(Fe,Al) intrachain bond length at low temperatures in the magnetically ordered state weakened this bond, whereas a decrease in the (Fe,Al)–(Fe,Al) interchain distance strengthened super-exchange paths between different chains. It was found that the addition of aluminium atoms influenced interatomic distances in Sm1−xBixFe3−yAly(BO3)4 much more than lowering the temperature from 293 K to 25 K. The effect of aluminium doping on magnetoelectric properties and structural symmetry of rare-earth iron borates is also discussed.

The crystal structure of samarium iron borate was analyzed with regard to growth conditions and temperature. The inclusion of about 7% Bi atoms in the crystals grown using the Bi2Mo3O12-based flux was discovered and there were no impurities in the crystals grown using the Li2WO4-based flux. No pronounced structural features associated with Bi inclusion were observed. The different absolute configurations of the samples grown using both fluxes were demonstrated. Below 80 K, a negative thermal expansion of the c unit-cell parameter was found. The structure of (Sm0.93Bi0.07)Fe3(BO3)4 belongs to the trigonal space group R32 in the temperature range 90-400 K. A decrease in the (Sm,Bi)-O, Sm-B, Sm-Fe, Fe-O, Fe-B and Fe-Fe distances is observed with a lowering of the temperature, B1-O does not change, B2-O increases slightly and the B2O3 triangles deviate from the ab plane. The strongest decrease in the equivalent isotropic atomic displacement parameters (Ueq) with decreasing temperature is observed for atoms Sm and O2, and the weakest is observed for B1. The O2 atoms have the highest Ueq values, the most elongated atomic displacement ellipsoids of all the atoms and the smallest number of allowed vibrational modes of all the O atoms. The largest number of allowed vibrational modes and the strongest interactions with neighbouring atoms is seen for the B atoms, and the opposite is seen for the Sm atoms. The quadrupole splitting Δ(T) of the paramagnetic Mössbauer spectra increases linearly with cooling. The Néel temperature [TN = 31.93 (5) K] was determined from the temperature dependence of the hyperfine magnetic field Bhf(T), which has a non-Brillouin character. The easy-plane long-range magnetic ordering below TN was confirmed.

The results of studies of the NdFe3(BO3)(4) by Fe-57 Mossbauer spectroscopy in comparison with the data of single crystal X-ray diffraction measurements are presented. Scanning of the crystal cell parameters in a wide temperature range T = 15-500 K revealed a negative thermal expansion along the c axis and structural anomalies. The temperature dependences of the Mossbauer parameters of hyperfine interaction in the paramagnetic state of NdFe3(BO3)(4) correlate well with the behavior of crystal cell parameters obtained by X-ray diffraction data. The temperature of the magnetic phase transition T-N = 32.54(4) K is established, below which the iron ions form a 3D magnetic order of the Izing type. The magnetic transition of the iron subsystem from a commensurate to an incommensurate structure at a temperature of about T # 15 K is discussed. The "Mossbauer " Debye temperature Theta(M) was estimated to be 485(2) K. (C) 2022 Elsevier B.V. All rights reserved.

4,6,10-Trihydroxy-1,4,6,10-tetraazaadamantane (TAAD) has been shown to form a stable Fe(IV) complex having a diamantane cage structure, in which the metal center is coordinated by three oxygen atoms of the deprotonated ligand. The complex was characterized by X-ray diffraction analysis, HRMS, NMR, FT-IR, Mössbauer spectroscopy and DFT calculations, which supported the d4 configuration of iron. The Fe(IV)-TAAD complex showed excellent performance in dioxygen activation under mild conditions serving as a mimetic of the thiol oxidase enzyme. The nucleophilicity of the bridgehead nitrogen atom in TAAD provides a straightforward way for the conjugation of Fe(IV)-TAAD complexes to various functional molecules. Using this approach, steroidal and peptide molecules having an iron(IV) label have been prepared for the first time. In addition, the Fe(IV)-TAAD complex was covalently bound to a polystyrene matrix and the resulting material was shown to serve as a heterogeneous catalyst for aerobic oxidation of thiols to disulfides.

The multiferroic RFe3(BO3)4 family is characterized by diverse magnetic, magnetoelectric, and magnetoelastic properties, the fundamental aspects of which are essential for modern electronics. The present research, using single-crystal X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) in the temperature range of 25–500 K, aimed to analyze the influence of local atomic coordination on magnetoelectric properties and exchange and super-exchange interactions in RFe3(BO3)4. Low-temperature, single-crystal XRD data of the magnetically ordered phase of RFe3(BO3)4 at 25 K, which were obtained for the first time, were supplemented with data obtained at higher temperatures, making it possible to draw conclusions about the mechanism of the structural dynamics. It was shown that, in structures with R = Gd, Ho, and Y (low-temperature space group P3121), a shift in oxygen atoms (O2, second coordination sphere of R atoms) was accompanied by rotation of the B2O3 triangle toward R atoms at low temperatures, and by different rearrangements in iron chains of two types, in contrast to Nd and Sm iron borates (space group R32). These rearrangements in the structures of space group P3121 affected the exchange and super-exchange paths at low temperatures. The MS results confirm the influence of the distant environment of atoms on the magnetoelectric properties of rare-earth iron borates at low temperatures.

Neodymium iron borate NdFe3(BO3)4 is an intensively studied multiferroic with high electric polarization values controlled by a magnetic field. It is characterized by a large quadratic magnetoelectric effect, rigidity in the base plane and a rather strong piezoelectric effect. In this work, the atomic structure of (Nd0.91Bi0.09)Fe3(BO3)4 was studied by single-crystal X-ray diffraction in the temperature range 20-500 K (space group R32, Z = 3). The Bi atoms found in the composition partially substitute the Nd atoms in the 3a position; they entered the structure due to the growth conditions in the presence of Bi2Mo3O12. It was shown that in the temperature range 20-500 K there is no structural phase transition R32→P3121, which occurs in rare-earth iron borates (RE = Eu-Er, Y) with an effective rare-earth cation radius smaller than that of Nd. The temperature dependence of the unit-cell c parameter reveals a slight increase on cooling below 90 K, which is similar to the results obtained previously for iron borates of Gd, Y and Ho. The atomic distances (Nd,Bi)-O, (Nd,Bi)-B, (Nd,Bi)-Fe, Fe-O, Fe-B and Fe-Fe in the iron chains and between chains decrease steadily with decreasing temperature from 500 to 90 K, whereas the B1(3b)-O distance does not change and the average B2(9e)-O distance increases slightly. There is a uniform decrease in the atomic displacement parameters with decreasing temperature, with a more pronounced decrease for the Nd(3a) and O2(9e) atoms. The O2(9e) atoms are characterized by the maximum atomic displacement parameters and the most elongated atomic displacement ellipsoids. The characteristic Debye and Einstein temperatures, and the static component in the atomic displacements were determined for cations using multi-temperature diffraction data. It was shown that the Nd cations have the weakest bonds with the surrounding atoms and the B cations have the strongest.

The temperature dependences of the structural parameters in a HoFe 3 (BO 3 ) 4 single crystal, studied by X-ray diffraction below and above the structural phase transition at T S = 365 K, correlate well with behavior of the Mössbauer parameter quadrupole interaction. However, two structural positions Fe1 and Fe2 of iron ions formed in the phase with space group P 3 1 21, which appears at temperatures below T S , cannot be distinguished by Mössbauer spectroscopy at 57 Fe nuclei. This becomes possible only below the Néel temperature T N . It has been established that below T N , iron ions form a 3D magnetic order of the Ising type with critical parameters β = 0.283(1) and the dimension of the order parameter n = 1. The refined value of the Néel temperature is T N = 37.42(1) K. The dynamics of changes in the Mössbauer parameters of the quadrupole shift and the magnetic hyperfine field B hf , observed near the temperature T = 4.4 K for iron ions in the Fe1 and Fe2 positions, indicates a reorientation of the magnetic moments of iron. This correlates with the spin-reorientation transition of Fe and Ho ions, previously observed by neutron diffraction in HoFe 3 (BO 3 ) 4 .

Rare-earth iron borate RFe3(BO3)4 crystals are studied worldwide lately owing to their perspective magnetoelectric and multiferroic properties [1].A major part of these single crystals was grown by flux method using Bi2Mo3O12 as a solvent [2,3].In this work temperature-dependent structural behavior of RFe3(BO3)4 (R = Ho, Y, Sm, Nd) single crystals were studied by X-ray structure analysis.The chemical composition was verified by X-ray energy-dispersive elemental analysis.Additional structure information was obtained by Mössbauer spectroscopy on 57 Fe nuclei.Bi atoms entered the composition of all the crystals during the growth process and the final compositions of single crystals studied are Ho 0.96 Bi 0.04 Fe 3 (BO 3 ) 4 , Y 0.95 Bi 0.05 Fe 3 (BO 3 ) 4 , Sm 0.93 Bi 0.07 Fe 3 (BO 3 ) 4 , and Nd 0.91 Bi 0.09 Fe 3 (BO 3 ) 4 .Unit cell parameters for R = Ho, Y, Nd were measured over 30-500 K. Parameters a,b of the crystals with R = Ho, Y are descending with temperature lowering, whereas a,b parameters of Nd-crystal do not change strongly.A sharp jump of a,b for R = Ho and Y was registered demonstrating presence of structural phase transition.At the same time, c (T) dependence has the similar character for all three crystals (R = Ho, Y, Nd) -c parameter decreases with lowering temperature to 80-100 K and then grows smoothly down to 30 K. Structure of Ho0.96Bi0.04Fe3(BO3)4,Y0.95Bi0.05Fe3(BO3)4,Sm0.93Bi0.07Fe3(BO3)4,and Nd0.91Bi0.09Fe3(BO3)4was determined at several temperatures in 90-500 K temperature range to study temperature-dependent structure peculiarities, in particular, changes during the structural phase transition for R = Ho, Y.The temperature of the phase transition Tstr = 365 К for R = Ho and Tstr = 370 К for R = Y was stated on the basis of systematic absences analysis and temperature dependence of a,b parameters.Inclusion of Bi atoms with a larger ionic radius leads to Tstr lowering in comparison with powder samples without Bi [4].The structure of the compounds with R = Ho, Y was refined in sp.gr.R32 above Tstr and in sp.gr.P3121 below it.Structure of crystals with R = Sm, Nd belongs to sp. gr.R32 at all temperatures studied.There is a slight steady decrease of specific distanced in (R,Bi)O6 trigonal prisms, FeO6 octahedra, BO3 triangles and Fe-Fe helicoidal chains with temperature lowering in sp.gr.R32.When going to lower-symmetry sp.gr.P3121 (for R = Ho, Y) and with further temperature decreasing non-uniform changes in the bond lengths are observed.Equivalent atomic displacement parameters Ueq decrease with temperature lowering.However, Ueq of oxygen atoms O1 and O2 as well as ones of boron atoms B2 and B3 (sp.gr.P3121 labels) are highly sensitive to a structural phase transition, demonstrating fluctuations around Tstr. Debye (TD) and Einstein (TE) characteristic temperatures for cations in the crystals with R = Ho, Y, Sm, Nd were calculated.Both TD and TE values are close for the same type of cations.TD and TE for R and Fe atoms in sp.gr.R32 are close to the corresponding values in sp.gr.P3121, and there is a significant change in TD, TE values for B atoms after a phase transition.Gamma-resonance measurements on 57 Fe nuclei showed that the hyperfine parameters of the Mössbauer spectra correspond to Fe 3+ ions in an octahedral oxygen environment.Quadrupole splitting Δ temperature dependence demonstrates complex behavior and is in good agreement with X-ray diffraction results.

We report on the structural phase transitions in the S doped FeSe superconductor by powder synchrotron X ray diffraction at high pressures up to 18.5 GPa under compression and decompression modes. In order to create high quasi hydrostatic pressures, diamond anvil cells filled with helium as a pressure transmitting medium were used. It was found that at ambient pressure and room temperature, S doped FeSe has a tetragonal structure. Under compression, in the region of 10 GPa, a phase transition from the tetragonal into the orthorhombic structure is observed, which persists up to 18.5 GPa. Our results strongly suggest that, at decompression, as the applied pressure decreases to 6 GPa and then is completely removed, most of the sample recrystallizes into the hexagonal phase of the structural type NiAs. However, the other part of the sample remains in the high pressure orthorhombic phase, while the tetragonal phase is not restored. These observations illustrate a strong hysteresis of the structural properties of S doped FeSe during a phase transition under pressure.

Aerobic reactions of iron(III), nickel(II), and manganese(II) chlorides with formaldoxime cyclotrimer (tfoH3) and 1,4,7-triazacyclononane (tacn) produce indefinitely stable complexes of general formula [M(tacn)(tfo)]Cl. Although the formation of formaldoxime complexes has been known since the end of 19th century and applied in spectrophotometric determination of d-metals (formaldoxime method), the structure of these coordination compounds remained elusive until now. According to the X-ray analysis, [M(tacn)(tfo)]+ cation has a distorted adamantane-like structure with the metal ion being coordinated by three oxygen atoms of deprotonated tfoH3 ligand. The metal has a formal +4 oxidation state, which is atypical for organic complexes of iron and nickel. Electronic structure of [M(tacn)(tfo)]+ cations was studied by XPS, NMR, cyclic (CV) and differential pulse (DPV) voltammetries, Mössbauer spectroscopy, and DFT calculations. Unusual stabilization of high-valent metal ion by tfo3- ligand was explained by the donation of electron density from the nitrogen atom to the antibonding orbital of the metal-oxygen bond via hyperconjugation as confirmed by the NBO analysis. All complexes [M(tacn)(tfo)]Cl exhibited high catalytic activity in the aerobic dehydrogenative dimerization of p-thiocresol under ambient conditions.

Nanowires have been formed from FeNi and FeCo alloys by the template synthesis method based on galvanic filling of pores of track membranes. A change in the nanowire elemental composition with a change in the electrolyte composition and with a change in the deposition potential has been studied. FeNi nanowires exhibit the effect of anomalous Fe codeposition: the iron content in the nanowires is much higher than that in the electrolyte. The difference increases with an increase in the initial concentration and with a decrease in the growth potential. It has also been found that the iron concentration increases in nanowire vertices. For FeCo nanowires, their composition corresponds to the electrolyte composition and changes only slightly with a change in the potential. An analysis of the X-ray diffraction data has determined the character of change in the spectra under varying growth conditions. The X-ray spectra of FeNi are found to depend on the growth potential (the intensity of phase peaks changes). Mössbauer measurements have revealed spontaneous magnetization for all samples of arrays of nanowires along their axes. The dependence of hyperfine magnetic field strength Bhf at 57Fe nuclei on the composition of nanowires of FexCo1 – x and FexNi1 – x solid solutions is obtained for the first time. It is found that the Bhf  value decreases with an increase in the electrodeposition rate (or with an increase in deposition potential U).

Nanowires (NWs) of FeNi and FeCo alloys were obtained by matrix synthesis based on galvanic filling of pores in track membranes. The change in the elemental composition of NWs when changing the composition of the electrolyte and when changing the deposition potential was studied. The effect of anomalous co-deposition of Fe is observed in the FeNi NWs: the iron content in the NWs is noticeably higher than that in the electrolyte. This difference increases when the initial concentration increases and when the growth potential decreases. An increase in the concentration of iron at the tops of the wires was also detected. For FeCo NWs, the composition corresponds to the composition of the electrolyte and did not change much when the potential changed. X-ray diffraction analysis allowed to determine the nature of changes in the spectra when the growth conditions change. The dependence of the X - ray spectra of FeNi on the growth potential is found- the intensity of the phase peaks changes. Mössbauer measurements revealed spontaneous magnetization for all samples of NW arrays along their axes. The dependence of the value of the ultrathin magnetic field Bh f on 57Fe nuclei on the composition of NWs (FexCo1−x and FexNi1−x) was obtained for the first time. It was found that the value of Bh f decreases with an increase in the speed of the electrodeposition process (or with an increase in the value of the deposition potential U).