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Using the methods of X-ray diffraction, Mössbauer spectroscopy, and temperature-programmed reduction with hydrogen, the relationship between the phase composition, structural characteristics of the phases, and the reactivity with respect to hydrogen was investigated for calcium ferrites-based catalysts. The catalyst samples were prepared via solid-state synthesis from CaO and Fe2O3 at 900 and 1000°C by varying the Fe2O3 content in the CaO–Fe2O3 system. The phase composition of the resultant samples corresponds to the CaO‒Ca2Fe2O5, Ca2Fe2O5‒CaFe2O4, and CaFe2O4‒α-Fe2O3 regions. In the CaO–Ca2Fe2O5 samples the lattice parameters of Ca2Fe2O5 and its activity with respect to hydrogen depend on the phase ratio. The activity of CaFe2O4 is higher in Ca2Fe2O5‒CaFe2O4 compared to CaFe2O4‒α-Fe2O3 catalysts. [ABSTRACT FROM AUTHOR]

Studies of the electronic structure and optical properties of the GdNiSb half-Heusler alloy have been performed. Calculations of the total and partial densities of electronic states were carried out on the basis of the GGA + U method, taking into account the correction for strong interactions in the f-electron system of gadolinium ions. By the method of spectral ellipsometry in the range of 0.078–5.64 eV, the dielectric functions of the alloy are investigated, their dispersion features are revealed. The anomalous behavior of optical conductivity in the infrared region of the spectrum for metals was found, confirming the presence of an energy gap at the Fermi level in the electronic spectrum, predicted in the calculation. A comparative analysis of the experimental and theoretical frequency dependences of optical conductivity is carried out, the features of interband light absorption are identified. The plasma frequency of conduction electrons is determined. [ABSTRACT FROM AUTHOR]

The paper examines the impact of interparticle interactions on the superparamagnetic relaxation of ultrasmall nanoparticle ensembles, using Fe2O3∙nH2O iron oxyhydroxide (ferrihydrite) nanoparticles as an example. Two samples were analyzed: ferrihydrite of biogenic origin (with an average particle size of ≈ 2.7 nm) with a natural organic shell, and a sample (with ≈ 3.5 nm) that underwent low-temperature annealing, during which the organic shell was partially removed. The DC and AC magnetic susceptibilities (χ′(T), χ′′(T)) in a small magnetic field in the superparamagnetic (SPM) blocking region of the nanoparticles were measured. The results show that an increase in interparticle interactions leads to an increase in the SPM blocking temperature from 28 to 52 K according to DC magnetization data. It is shown that below the SPM blocking temperature, magnetic interactions of nanoparticles lead to the formation of a collective state similar to spin glass in bulk materials. The scaling approach reveals that the dynamics of correlated magnetic moments on the particle surface slow down with increasing interparticle interactions. Simulation of χ′′(T) dependence has shown that the dissipation of magnetic energy occurs in two stages. The first stage is directly related to the blocking of the magnetic moment of nanoparticles, while the second stage reflects the spin-glass behavior of surface spins and strongly depends on the strength of interparticle interactions. [ABSTRACT FROM AUTHOR]

Powders of maghemite γ-Fe2O3 with an average diameter of 8 nm, γ-Fe2O3/SiO2 composites with an agglomerate diameter of about 50 nm and a size of interspersed γ-Fe2O3 particles of 6 nm, and γ‑Fe2O3/SiO2/aptamer(FAS9) composites were synthesized by chemical deposition. Mössbauer spectra were measured, the static and dynamic magnetic properties of the powders were studied, and the coercive force was determined, which decreases from 14 Oe for γ-Fe2O3 powders to 3 Oe for the γ-Fe2O3/SiO2 composite. It is shown that the particle blocking temperature is close to room temperature. The increment of temperature of the powders was measured in the ferromagnetic resonance mode; the temperature of the Fe2O3/SiO2 composite (ΔT ≈ 16°C) turned out to be higher than that of the pure γ-Fe2O3 powder (ΔT ≈ 10°C). It has been experimentally shown that temperature increment ΔT is proportional to the square of the microwave field amplitude. It has been shown that the composition γ-Fe2O3/SiO2/aptamer FAS9 is able to effectively bind to tumor cells, and FMR hyperthermia leads to a decrease in the viability of tumor cells. [ABSTRACT FROM AUTHOR]

The magnetic-field dependence of the superparamagnetic-blocking temperature TB of systems of antiferromagnetically ordered ferrihydrite nanoparticles has been investigated and analyzed. We studied two powder systems of nanoparticles: particles of "biogenic" ferrihydrite (with an average size of 2.7 nm), released as a result of vital functions of bacteria and coated with a thin organic shell, and particles of biogenic ferrihydrite subjected to low-temperature annealing, which cause an increase in the average particle size (to 3.8 nm) and burning out of the organic shell. The character of the temperature dependences of magnetization, measured after cooling in a weak field, as well as the shape of the obtained dependences TB(H), demonstrate peculiar features, indicating the influence of magnetic interparticle interactions. A detailed analysis of the dependences TB(H) within the random magnetic anisotropy model made it possible to estimate quantitatively the intensity of magnetic particle–particle interactions and determine the magnetic anisotropy constants of individual ferrihydrite particles. [ABSTRACT FROM AUTHOR]

Cu2FeBO5 ludwigite single crystals have been grown from a solution–melt by spontaneous crystallization. Using the X-ray diffraction method, the crystal structure has been resolved in detail. Cations in sites M2, M3, and M4 have turned out to be structurally disordered. It has been found that oxygen atoms are disordered in one of five nonequivalent sites (O4). As can be seen from Mössbauer spectroscopy data, Fe3+ ions occupy four nonequivalent sites with different distortions of coordination octahedra. In the temperature range 40 K ≤ T ≤ 300 K, the spectra represent a superposition of quadrupole doublets. Static susceptibility measurements have revealed two magnetic features at T1 = 35 K and T2 = 20 K and spin-glass effects. Specific heat measurements in the interval 4–300 K have not discovered magnetic-transition-related anomalies. [ABSTRACT FROM AUTHOR]

A mixture of the Al2Au intermetallic compound and copper powders was compacted and then melted in an argon atmosphere to form an Al2Au + Cu ingot. Study of the structure of the alloy showed the formation of areas of the Al2Au intermetallic phase, which are brightly colored and are present in the AlAu intermetallic matrix. Thin Cu-enriched streaks occur inside the AlAu matrix. The optical characteristics of the prepared ternary compound have been measured. The microindentation of the intermetallic phases has been performed; the microhardness and contact elastic modulus have been determined. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of nonstoichiometric ErNi2Mnx compounds (with х = 0, 0.5, 1) have been studied. Spin-polarization calculations of the total and partial densities of electron states have been performed in terms of DFT + U method with a correction for strong electronic correlations in the 4f shell of Er in the approximation of ErNi2 –xMnx solid-solution. The peculiarities of transformations of the densities of electron states Have been determined depending on the manganese content. The optical properties of these compounds have been studied over a wide wave length range. The calculated interband optical conductivity spectra have been compared with the dependences obtained experimentally. The origin of the quantum absorption of light is discussed. The plasma and relaxation frequencies of current carriers have been determined. [ABSTRACT FROM AUTHOR]

Nickel and cobalt ferrite nanoparticles have been synthesized using the chemical precipitation method; the nanoparticle sizes were found to be 63 ± 22 and 26 ± 4 nm, respectively. The static hysteresis loops and Mössbauer spectra have been measured. It is shown that cobalt ferrite powders are magnetically harder than nickel ferrite powders. Ferromagnetic resonance (FMR) curves have been studied. It is found that the FMR absorption for cobalt ferrite is observed at room temperature and above. The time dependences of the nanoparticle warm-up under FMR conditions have been measured. The maximum temperature changes for nickel ferrite and cobalt ferrite particles are 8 and 11 K, respectively. Using the example of cobalt ferrite powder, the possibility of effectively heating of particles in the FMR mode in their own field without using a DC magnetic field source is shown. The observed effect can be used in magnetic hyperthermia. [ABSTRACT FROM AUTHOR]

This paper presents electronic spectrum calculations and a study of the optical properties of the binary compounds Mn70Al30 and Mn80Al20 with the β-Mn structure. The energy dependences of the calculated density of states, with high values at the Fermi level, are determined by broad bands formed by manganese 3d states. The calculated electronic structures are used to analyze measured optical conductivity spectra of the alloys in the quantum light absorption range. From their optical properties in the infrared spectral region, we evaluate a number of characteristics of conduction electrons. [ABSTRACT FROM AUTHOR]

Changes in the magnetic properties of FeBO3 single crystals in the course of spin crossover occurring with increasing pressure up to 63 GPa are studied both experimentally and theoretically. Simultaneous measurements of the nuclear diffraction and nuclear forward scattering spectra make it possible to detect the antiferromagnetic high-spin state at low pressures up to 48 GPa and to reveal the antiferromagnetic state within the range characterized by the coexistence of Fe3+ ions in the high-spin and low-spin states, which occurs at pressures from 48 to 54 GPa, where the hysteresis takes place. Above 58 GPa, only the low-spin state is observed, whereas the magnetic order is absent down to 9 K. An analysis of changes in the exchange interactions manifesting themselves at spin crossover suggests that there exist competing ferromagnetic and antiferromagnetic contributions nearly compensating each other. A possible Néel temperature in the low-spin state does not exceed 7 K; thus, an ordered state cannot be observed in our experiments. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles coated with polyethylene glycol were synthesized by coprecipitation for use in the magnetic separation of DNA (deoxyribonucleic acid). The blocking temperature of nanoparticles was studied by the methods of Mössbauer spectroscopy, ferromagnetic resonance, and using magnetometric measurements. The blocking temperature calculated from the temperature dependence of the coercive force was ~ 200 K. The calculation of the blocking temperature from the relaxation time obtained using Mössbauer spectroscopy gave a value of ~ 450 K. The blocking temperature obtained using ferromagnetic resonance was ~ 910 K. The relationship between the obtained blocking temperatures is in good agreement with the Néel-Brown formula. The constants of effective and surface anisotropy were determined by the method of ferromagnetic resonance. Isolation of DNA from blood using prepared particles and separation in a permanent magnet field revealed sufficient productivity, high speed, and the "chemical delicacy" of this approach. [ABSTRACT FROM AUTHOR]

Results of calculations of the electronic structure and studies of the optical properties of the Mn3Al compound in the two-phase crystalline state are reported. The calculated densities of electron states are determined by the wide (~8 eV) 3d band of Mn atoms; the Fermi level is localized within the range of high densities of states. The nature of quantum light absorption is discussed based on the comparison of experimental and theoretical spectra of the interband optical conductivity. It is shown that the calculated structure of energy bands of the compound allows us to qualitatively interpret the frequency dispersion of this spectral parameter. [ABSTRACT FROM AUTHOR]

Magnetic iron oxide nanoparticles for separating DNA from blood cells are synthesized. Magnetic nanoparticles with a silicate coating are obtained, and their physical and chemical properties are studied. The possibility of using the nanocomposites to isolate DNA from leukocytes for hematological studies is confirmed experimentally. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of intermetallic compounds GdTi0.05MnxFe0.95 –xSi (x = 0, 0.4, 0.6, 0.95) have been investigated in this work. Spin-polarized densities of electronic states and optical conductivity spectra have been calculated by the DFT + U method, taking strong electron correlations in the 4f shell of Gd into account. The optical properties of these materials in the energy range 0.078–4.6 eV have been measured by the ellipsometric method. The nature of the quantized light absorption has been discussed, and a comparison of the experimental and theoretical spectra of the interband optical conductivity has been used. It has been shown that the change in the optical properties of the compounds when iron is substituted for manganese can be interpreted qualitatively based on the calculations of the densities of electronic states. [ABSTRACT FROM AUTHOR]

Mössbauer spectroscopy is used to study the characteristic features of the crystal lattice dynamics in powdered single crystals of Fe1.75V0.25BO4 warwickite in the temperature range of 4.2–505 K. The Debye temperature (ΘD = 260 K) is determined from the temperature dependence of the probability of the Mössbauer effect in the thin absorber approximation. It is found that the electron delocalization related to the fast electronic transfer between neighboring Fe3+ and Fe2+ cations takes place in the temperature range of 260−505 K. As a result, iron cations exhibiting the mixed valence (Fe2.5+) arise. This process correlates with a change in the elastic properties of the lattice. Such correlation leads to a sharp decrease in the recoil-free absorption of γ‑ray photons by the crystal lattice in the range of 260–400 K. [ABSTRACT FROM AUTHOR]

We report on the results of analysis of magnetic properties and electronic structure, which were obtained by self-consistent ab initio spin-polarized calculations, as well as experimentally determined optical properties of cobalt-based intermetallic compounds YCo3, Y2Co7, and LaCo5. Optical characteristics were measured using ellipsometry in a wide spectral interval. The mechanism of quantum absorption of light in these materials is considered based on comparative analysis of experimental and theoretical spectra of interband optical conduction. Analysis of the crystalline structure and the resultant magnetic, electronic, and optical characteristics revealed peculiarities in the variation of physical properties. which appeared upon an increase in the cobalt content in the intermetallides. [ABSTRACT FROM AUTHOR]

We report on the results of analysis of magnetic properties and electronic structure, which were obtained by self-consistent ab initio spin-polarized calculations, as well as experimentally determined optical properties of cobalt-based intermetallic compounds YCo3, Y2Co7, and LaCo5. Optical characteristics were measured using ellipsometry in a wide spectral interval. The mechanism of quantum absorption of light in these materials is considered based on comparative analysis of experimental and theoretical spectra of interband optical conduction. Analysis of the crystalline structure and the resultant magnetic, electronic, and optical characteristics revealed peculiarities in the variation of physical properties. which appeared upon an increase in the cobalt content in the intermetallides. [ABSTRACT FROM AUTHOR]

Dependences of relative saturation magnetization on temperature are measured for amorphous nanocrystalline ribbons of Finemet-type FeCu1Nb3Si13.5B8, FeCu1Nb3Si13B6, and FeCu1Nb3Si13B13 compositions. The character of the structural relaxation of amorphous alloys is established by means of Mössbauer spectroscopy, and the main magnetic characteristics are determined. It is found that the structural relaxation of amorphous ribbon proceeds in several stages upon annealing. [ABSTRACT FROM AUTHOR]

Results are presented from investigating the electronic structure and optical properties of DyCuGe and HoCuGe compounds. Spin-polarized calculations of the band structure are made using the local spin density approximation that allows for strong electronic correlations in the 4f-shells of rare earth ions. The optical properties of these alloys are studied in a broad range of wavelengths via ellipsometry. The calculated electron densities of states are used to interpret the experimental energy dependences of optical conductivities in the region of interband light absorption. [ABSTRACT FROM AUTHOR]

The spin-polarized electronic structure, magnetic moments, and spectra of optical conductivity of the ternary ErSn1.1Ge0.9 and TmSn1.1Ge0.9 compounds have been calculated within the GGA+U method, taking into account strong electron correlations in the 4f-shell of Er and Tm, as well as non-stoichiometry of compositions. The calculation results pointed to antiferromagnetic ordering for both intermetallics with effective magnetic moments that precisely reproduce the published experimental values. Optical properties of these compounds were measured using the ellipsometric method in the energy range of 0.078–5.64 eV. It has been shown that the main peculiarities of experimental curves are described by calculated densities of electronic states. The good agreement of magnetic moments and interband optical conductivities, which are calculated from first principles, with the experimental data indicates the importance of accounting for the strong electron correlations and non-stoichiometry of compositions in calculations of electronic structure of the RSn1.1Ge0.9-type compounds containing heavy rare-earth metals. [ABSTRACT FROM AUTHOR]

Nuclear γ-resonance experiments with energy and time resolved detection are carried out with ϵ-F2O3 nanoparticles and a 57Co(Rh) laboratory Mössbauer source of γ radiation and a 14.4125 keV synchrotron radiation source on the ID18 beamline (ESRF) in the temperature range of 4–300 K. Both methods show a tremendous increase in the hyperfine field in tetrahedrally coordinated iron positions during the magnetic transition in the range of 80–150 K. As a result, the splitting of the quantum beat peaks in the nuclear scattering spectra is observed in the time interval of 20–170 ns with a periodicity of ∼ 30 ns. In addition, the first quantum beat is slightly shifted to shorter times. A correlation between the quadrupole shift and the orbital angular momentum of iron in ϵ-F2O3 nanoparticles is found. The magnetic transition leads to the rotation of the magnetic moment in the tetrahedral positions of iron around the axis of the electric field gradient by an angle of 44°. [ABSTRACT FROM AUTHOR]

The methods of X-ray diffraction analysis and transmission electron microscopy were used to study the structure of coatings based on the Al2Au intermetallic compound. It has been shown that after the deposition, the coating is in an amorphous state. The annealing of the coating at 500°C for 15 min results in initial stages of crystallization. In the annealed coating, signs of a retained amorphous structure and grains of the Al2Au intermetallic compound with a size of 30–100 nm are observed. In addition, a small amount of the intermetallic phase AlAu is fixed in the coating after annealing. Optical characteristics of the annealed sample have been measured; a comparison with literature data on the structure and optical properties of coatings obtained by different methods was performed. [ABSTRACT FROM AUTHOR]

Structured composite materials CaFe2O4-α-Fe2O3 (α-Fe2O3 content is 2–82 wt.%) are obtained with the method of solid-phase synthesis at 1000 °C. The phase composition of the samples is studied using powder X-ray diffraction. It is shown that the content of CaFe2O4 and α-Fe2O3 phases changes linearly, depending on the composition of the starting material. The scanning electron microscopy data indicate the formation of a two-phase system α-Fe2O3-CaFe2O4. The Mössbauer spectroscopy data at room temperature testify the formation of cationic iron vacancies in the CaFe2O4 crystal structure in the absence of α-Fe2O3 structural defects. Cationic vacancies can be formed during the synthesis in the atmosphere of air. [ABSTRACT FROM AUTHOR]

The stability of a catalyst for partial H2S oxidation has been studied by the ferromagnetic resonance (FMR) technique combined with transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and magnetostatic investigations. The ε-Fe2O3 iron oxide nanoparticles supported on silica have been examined for their stability under the selective H2S oxidation conditions. The combination of the physicochemical methods has been used to study the state of reacted catalysts. The ε-Fe2O3 phase has been found to remain stable under the selective H2S oxidation conditions at temperatures up to 300 °C. The active phase state during the catalytic reaction has been explored using in situ FMR experiments. It has been established that the ε-Fe2O3 nanoparticles retain their structure and magnetic properties in the presence of H2S at high temperatures. During the in situ FMR experiments, the ε-Fe2O3 sulfidation process has been studied. [ABSTRACT FROM AUTHOR]

The optical properties of binary GdFe2 and LuFe2 compounds are studied by the ellipsometric method in the 0.22–17 μm spectral range. A number of spectral and electronic characteristics are determined. The experimental dependences of optical conductivity in the light quantum absorption region are interpreted based on previously published calculations of electronic states densities. [ABSTRACT FROM AUTHOR]

The superparamagnetism of an ensemble of ϵ-Fe2O3 nanoparticles with a mean size of 3.9 nm dispersed in a xerogel SiO2 matrix is studied by the Mössbauer spectroscopy method. It is shown that most nanoparticles at room temperature are in the superparamagnetic (unblocked) state. As the temperature decreases, the progressive blocking of the magnetic moments of the particles occurs, which is manifested in the Mössbauer spectra as the transformation of the quadrupole doublet into a Zeeman sextet. The analysis of the relative intensity of the superparamagnetic (quadrupole doublet) and magnetically split (sextets) spectral components in the range of 4-300 K provides the particle size distribution, which is in agreement with the transmission electron microscopy data. The values of the effective magnetic anisotropy constants (Keff) are determined, and the contribution of surface anisotropy (KS) is estimated for particles of various sizes. It is shown that the quantity Keff is inversely proportional to the particle size, which indicates the significant contribution of the surface to the magnetic state of the ϵ-Fe2O3 nanoparticles with the size of several nanometers. [ABSTRACT FROM AUTHOR]

Ellipsometric investigations of the optical properties of Ru2Ge3 and Ru2Sn3 intermetallic compounds are carried out in the wavelength range from 0.22 to 15 μm. The nature of interband light absorption is analyzed based on a comparative analysis of the experimental and theoretical frequency dependences of an optical conductivity. The obtained results confirm the existence of energy gaps at the Fermi level in the electronic spectra of these materials predicted earlier by the band-structure calculations. [ABSTRACT FROM AUTHOR]

Nanoparticles of antiferromagnetically ordered materials acquire the uncompensated magnetic moment caused by defects and surface effects. A bright example of such a nano-antiferromagnet is nanoferrihydrite consisting of particles 2-5 nm in size, the magnetic moment of which amounts to hundreds of Bohr magnetons per particle. We present a brief review of the studies on magnetic properties of ferrihydrite produced by bacteria. Special attention is focused on the aspects of possible biomedical applications of this material, i.e., the particle elimination, toxicity, and possible use for targeted drug delivery. [ABSTRACT FROM AUTHOR]

A new metamaterial is obtained on the basis of ε-Fe2O3 nanoparticles immobilized in a xerogel matrix. Samples are synthesized by impregnating SiO2 hydrogel with iron (II) salts with subsequent drying and calcination. The structure and magnetic properties of the composites are probed using transmission electron microscopy, X-ray diffraction, Mössbauer spectroscopy, and static magnetic measurements. [ABSTRACT FROM AUTHOR]

The optical properties of the compounds HoNi 5 − xAl x ( x = 0, 1, 2) have been investigated using the ellipsometric method in the wavelength range from 0.22 to 16 μm. The electronic structure of these intermetallic compounds has been calculated in the local electron-spin density approximation with the correction for strong electronic interactions in the 4 f shell of the holmium ions. The experimental dispersion dependences of optical conductivity in the region of interband light absorption have been interpreted based on the results of the calculation of the electron density of states. The plasma and relaxation frequencies of electrons have been determined. [ABSTRACT FROM AUTHOR]

The effect of atomic disordering on the optical properties of PtFe alloy, whose stoichiometry is close to that of PtFe, has been investigated. The optical constants of ordered and plastically deformed alloys, which are, respectively, in the paramagnetic and ferromagnetic states, have been measured by the polarimetric method. The frequency dispersions of the permittivity, optical conductivity, and reflectivity, as well as the microscopic characteristics of conduction electrons (plasma and relaxation frequencies), have been calculated. The energy dependences of the optical conductivity are compared to the calculated energy-band structure of atomically ordered and disordered PtFe compounds. [ABSTRACT FROM AUTHOR]

The optical properties of Fe78Si10B12 ferromagnetic alloy in amorphous, crystalline, and intermediate structural states have been investigated by ellipsometry in the spectral range of 0.22–18 µm. It is established that alloy crystallization leads to a significant change in the optical constants and the frequency dependences of the dielectric functions calculated based on these optical constants. The structural reconstruction under heat treatment leads to an increase in the intensity and shift of interband absorption bands. The plasma and relaxation frequencies of conduction electrons are determined; their numerical values also depend on the degree of atomic ordering. [ABSTRACT FROM AUTHOR]

The optical properties of the TbNi5 − x Cu x intermetallic compounds have been investigated in the spectral range 0.08–5.64 eV by the ellipsometric method. It is shown that substitution of nickel for copper atoms leads to a significant change in the frequency dependence of the optical conductivity; this change is related to modification of the electronic spectrum. The formation of a new interband absorption band has been revealed, whose intensity increases with an increase in the copper content. The concentration dependences of the plasma and relaxation frequencies of conduction electrons in the compounds under study are determined. Self-consistent calculation of the electronic structure of the TbNi5 binary compound has been performed in the approximation of local electron spin density. The electron density of states for two spin projections and the optical conductivity of this compound have been calculated. [ABSTRACT FROM AUTHOR]

The optical constants of the color intermetallic compounds PdGd and Pd3Gd are measured by the polarimetric method. Frequency dispersions of the complex permittivity, optical conductivity, and reflectivity, and also the microcharacteristics of the conduction electrons — plasma and relaxation frequencies — are calculated. The energy dependences of these parameters are compared with similar characteristics obtained for this type of compound of palladium with scandium, terbium, and lutecium. [ABSTRACT FROM AUTHOR]

Cu2FeBO5 ludwigite single crystals have been grown from a solution–melt by spontaneous crystallization. Using the X-ray diffraction method, the crystal structure has been resolved in detail. Cations in sites M2, M3, and M4 have turned out to be structurally disordered. It has been found that oxygen atoms are disordered in one of five nonequivalent sites (O4). As can be seen from Mössbauer spectroscopy data, Fe3+ ions occupy four nonequivalent sites with different distortions of coordination octahedra. In the temperature range 40 K ≤ T ≤ 300 K, the spectra represent a superposition of quadrupole doublets. Static susceptibility measurements have revealed two magnetic features at T1 = 35 K and T2 = 20 K and spin-glass effects. Specific heat measurements in the interval 4–300 K have not discovered magnetic-transition-related anomalies. [ABSTRACT FROM AUTHOR]