New Publications

Structural, thermal and electrical studies of thallium-scandium-hafnium(zirconium) molybdates

Victoria G.Grossman, Maxim S.Molokeev, Jibzema G.Bazarov, Bair G.Bazarova, Nikolay I.Sorokin// Journal of Solid State Chemistry//

https://doi.org/10.1016/j.jssc.2021.122832

Thallium scandium hafnium molybdate Tl5ScHf(MoO4)6 and thallium scandium zirconium molybdate Tl5ScZr(MoO4)6 crystallize in trigonal symmetry with the space group R3¯c. The compounds are synthesized by sintering the finely powdered simple molybdates mixture in a muffle furnace at 723–823 K for 100 h. The crystal structures of Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 are obtained by Rietveld method. The following unit cell parameters are calculated for Tl5ScHf(MoO4)6: a = 10.62338 (5), c = 38.0579 (2) Å, V = 3719.64 (4) Å3, Z = 6 and for Tl5ScZr(MoO4)6: a = 10.63216 (7), c = 38.0716 (3) Å, V = 3727.14 (5) Å3, Z = 6. The conductivity of the Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 are measured between 293 and 860 K. The ionic conductivity of Tl5ScHf(MoO4)6 and Tl5ScZr(MoO4)6 molybdates are 8 × 10−4 S/cm and 8 × 10−3 S/cm (at 773 K); the activation energy of ionic transfer are 0.8 eV and 0.3 eV respectively.

Raman scattering study of the rare-earth binary ferroborate Nd0.75Dy0.25Fe3(BO3)(4) single crystal

Glamazda, AY, Gnezdilov, VP, Lemmens, P, Zvyagina, GA , Gudim, IA // LOW TEMPERATURE PHYSICS//

Doi:10.1063/10.0007074

We report comprehensive Raman scattering measurements on a single crystal of binary ferroborate Nd0.75Dy0.25Fe3(BO3)(4) in the temperature range of 7-295 K with 532 nm (18797 cm(-1)) laser excitation. The performed analysis of the polarized Raman spectra revealed the bands assigned to phonon, magnetic, and electronic excitations. The temperature evolution of these quasiparticle excitations has allowed us to ascertain the intricate coupling and interplay between lattice, magnetic, and electronic degrees of freedom. Analysis of the measured Raman spectra made it possible to identify all A(1) and E phonon modes predicted by the group-theoretical analysis. The splitting energies between the LO and TO components of the polar E phonons were determined. Below the magnetic ordering temperature of the Fe sublattice, T-N, we have revealed a multiple peaked two-magnon excitation. Analyzing the temperature evolution of low-frequency modes in the spectra, we also identified modes that are associated with electronic transitions between the crystal field levels of the Nd3+ ions with ground-state I-4(9/2) and of the Dy3+ ions with ground-state H-6(15/2) multiplets. In addition to the already known temperatures of magnetic transitions, analysis of the temperature behavior of low-frequency phonon and electronic excitations made it possible to establish a temperature T* = 100 K, presumably associated with local distortions of the crystal lattice. The presence of this temperature is confirmed by our ultrasonic study. A group of intense bands observed in the frequency range 1700-2200 cm(-1) has been associated with the mixed low-lying electronic Raman transitions I-4(9/2)& RARR;I-4(11/2) and the high-energy luminescence ones (4)G(5/2)+(2)G(7/2)& RARR;I-4(9/2) for the Nd3+ ion.

Desulfovibrio desulfuricans AY5 Isolated from a Patient with Autism Spectrum Disorder Binds Iron in Low-Soluble Greigite and Pyrite

Olga V. Karnachuk, Olga P. Ikkert, Marat R. Avakyan, Yurii V. Knyazev, Mikhail N.Volochaev, Viacheslav S. Zyusman, Vasily L. Panov, Vitaly V. Kadnikov ,Andrey V. Mardanov and Nikolai V. Ravin// MICROORGANISMS//

 https://doi.org/10.3390/microorganisms9122558

The sulphate-reducing bacteria (SRB) of genus Desulfovibrio are a group of prokaryotes associated with autism spectrum disorders (ASD). The connection between the elevated numbers of Desulfovibrio in the gut of children with ASD compared with healthy children remains unresolved. A conceivable consequence of SRB overgrowth in the gut is the conversion of bioavailable iron into low-soluble crystalline iron sulphides, causing iron deficiency in the organism. In this study, we report the draft genome sequence and physiological features of the first cultivable isolate from a patient with ASD, Desulfovibrio desulfuricans strain AY5.The capability of the strain to produce crystalline iron sulphides was studied under different pH conditions. The most notable greigite(Fe3S4) and pyrite (FeS2) formation was revealed at pH 6.0, which suggests that the iron loss due to insoluble sulphide formation may occur in the proximal part of the gastrointestinal tract. Strain AY5 was adapted to grow under nitrogen-limiting conditions by N2 fixation. The urease found in the strain’s genome may play a role in resistance to acidic pH.

Unveiling White Light Emission of a One-Dimensional Cu(I)-Based Organometallic Halide toward Single-Phase Light-Emitting Diode Applications

Jinglong Huang, Yinhui Peng, Jiance Jin, Maxim S. Molokeev, Xiaobao Yang, and Zhiguo Xia// JOURNAL OF PHYSICAL CHEMISTRY LETTERS//

https://doi.org/10.1021/acs.jpclett.1c03767

Luminescent organometallic halide crystals, especially with single-component white emission, are urgently needed for light-emitting diode (LED) applications. Barriers for the applications, however, lie in their lead toxicity, poor stability, and low photoluminescence quantum yield (PLQY). Here, a one-dimensional Cu(I)-based hybrid metal halide (C12H24O6)CsCu2Br3 is designed and prepared via a simple solution method. Upon 365 nm excitation, a broad-band white light emission centered at 535 nm with a full width at half maximum of 186 nm and a PLQY of 78.3% is monitored. The experimental results together with calculation data indicate that the existence of the split peaks at 486 and 570 nm at a low temperature is attributed to the decrease of energy level degeneracy by virtue of the lattice distortion. Moreover, the stability along with the good device performance of the as-fabricated white LED was also discussed. The results demonstrate that (C12H24O6)CsCu2Br3 is highly competitive in lighting application, and it can further enable breakthrough material design for new luminescent organometallic halides.

Antimicrobial properties of nanofiltration membranes modified with silver nanoparticles

Renat Khaydarov, Olga Gapurova, Murodjon Abdukhakimov, Ilkham Sadikov, Ilnur Garipov, Praveen Thaggikuppe Krishnamurthy, Sergey M. Zharkov, Galina M. Zeer, Polina A. Abolentseva, Svetlana V. Prudnikova & Svetlana Y. Evgrafova // JOURNAL OF PHYSICAL CHEMISTRY LETTERS//

DOI: 10.1021/acs.jpclett.1c03767

Luminescent organometallic halide crystals, especially with single-component white emission, are urgently needed for light-emitting diode (LED) applications. Barriers for the applications, however, lie in their lead toxicity, poor stability, and low photoluminescence quantum yield (PLQY). Here, a one-dimensional Cu(I)-based hybrid metal halide (C12H24O6)CsCu2Br3 is designed and prepared via a simple solution method. Upon 365 nm excitation, a broad-band white light emission centered at 535 nm with a full width at half maximum of 186 nm and a PLQY of 78.3% is monitored. The experimental results together with calculation data indicate that the existence of the split peaks at 486 and 570 nm at a low temperature is attributed to the decrease of energy level degeneracy by virtue of the lattice distortion. Moreover, the stability along with the good device performance of the as-fabricated white LED was also discussed. The results demonstrate that (C12H24O6)CsCu2Br3 is highly competitive in lighting application, and it can further enable breakthrough material design for new luminescent organometallic halides

Field test of the surface soil moisture mapping using Sentinel-1 radar data

Zeyliger, A. M.; Muzalevskiy, K., V; Zinchenko, E., V; Ermolaeva, O. S. // Science Of The Total Environment//

https://doi.org/10.1016/j.scitotenv.2021.151121

Soil surface moisture is one of the key parameters for describing the hydrological state and assessing the potential availability of water for irrigated plants. Because the radar backscattering coefficient is sensitive to soil moisture, the application of Sentinel-1 data may support soil surface moisture mapping at high spatial resolution by detecting spatial and temporal changes at the field scale for precision irrigation management. This mapping is required to control soil water erosion and preferential water flow to improve irrigation water efficiency and minimise negative impacts on surface and ground water bodies.

EPR Study of the Single-Ion Magnetic Anisotropy of the Fe3+ Ion in a Diamagnetic PbGaBO4 Crystal

Vorotynov, A. M.; Pankrats, A., I; Kolkov, M., I // Journal Of Experimental And Theoretical Physics//

https://doi.org/10.1134/S1063776121110054

Crystals of a diamagnetic PbGaBO4 analog containing a small amount (about 0.5 at %) of Fe3+ ions are grown. The single-ion EPR spectra of Fe3+ in PbGa1 – xFexBO4 single crystals are analyzed with allowance for a crystal structure. The existence of four magnetically nonequivalent positions of Fe3+ ions with different local anisotropy axis directions has been confirmed. The parameters of the spin Hamiltonian written in the approximation of the local orthorhombic symmetry of a paramagnetic center are determined. The values of single-ion anisotropy constants, which are unusually high for S ions, is shown to be caused by a strong distortion of the ligand environment of Fe3+ ions. The single-ion contribution to the energy of the total magnetic anisotropy of a magnetically concentrated PbGaBO4 crystal is estimated. Two-ion mechanisms of the Fe–Fe interaction anisotropy are assumed to play a dominant role in the formation of magnetic anisotropy in a magnetically concentrated crystal.

Magneto-Optical Parameter Q for Structures with Uniaxial Optical Anisotropy

Maximova, O. A.; Lyaschenko, S. A.; Varnakov, S. N.; Ovchinnikov, S. G. // Journal Of Experimental And Theoretical Physics//

DOI: https://doi.org/10.1134/S1063776121110030

This paper is devoted to the development of reflection magneto-optical ellipsometry. We have solved the inverse problem for structures with uniaxial optical anisotropy: have determined the reflection coefficients for the ambient–sample interface, and have derived an analytic expression for magneto-optical parameter Q proportional to the magnetization. This expression makes it possible to determine parameter Q exclusively from experimental data obtained using magneto-optical ellipsometry. We present a detailed algorithm for performing experiment on determining the dielectric tensor in the transverse geometry.

Mechanisms of the Magnetoresistance Hysteresis in a Granular HTS with the Paramagnetic Contribution by the Example of HoBa2Cu3O7-delta

Semenov, S., V; Gokhfel'd, D. M.; Terent'ev, K. Yu; Balaev, D. A. // Physics Of The Solid State/

DOI: https://doi.org/10.1134/S1063783421100334

The hysteretic behavior of magnetoresistance R(H) of the granular high-temperature superconductor (HTS) HoBa2Cu3O7 – δ has been investigated. The YBCO superconductors with a rare-earth element (Nd, Ho, Er, Sm, Yb, or Dy) with the magnetic moment in the yttrium site are characterized by a significant paramagnetic contribution to the total magnetization. The main goal of this study has been to establish the possible effect of this paramagnetic contribution on the magnetotransport properties, which are determined by tunneling of superconducting current carriers through the grain boundaries. An analysis of the results obtained basing on the concept of an effective field in the intergrain medium showed that the distribution of the magnetic induction lines from the paramagnetic moments is fundamentally different from that of the Meissner currents and Abrikosov vortices. The magnetic induction lines from the paramagnetic moments are not concentrated in the region of grain boundaries and therefore insignificantly affect the magnetotransport properties of a granular HTS. At the same time, the magnetic induction lines are strongly concentrated in the grain boundaries, which is caused by the Meissner currents and Abrikosov vortices, due to the features of their properties. Specifically, the magnetic flux compression determines the magnetotransport (in particular, the R(H) hysteresis) properties of granular HTSs, including 1–2–3 ones, with a rare-earth ion with the magnetic moment.

Enhanced luminescence properties of Li2MgTiO4: Mn4+, Ge4+ phosphor via single cation substitution for indoor plant cultivation

Zhang, Sijin; Gai, Shujie; Zhang, Xiaojuan; Xia, Mao; Zhou, Zhi; et al. // Ceramics International/

https://doi.org/10.1016/j.ceramint.2021.10.082

Red and far-red emitting phosphors have been widely used in phosphor-converted light emitting diode (pc-LED) devices to provide lighting for indoor plant growth, thus achieving desired product qualities. Among the many ways to optimize phosphors’ optical performance, cationic substitution is one of the most effective methods. In this study, red phosphors (Li2MgTi1-x-yO4: xMn4+, yGe4+) were synthesized by high temperature solid state method and the optical performance of phosphors were improved with increasing Ge4+ constituents. In particular, luminescence intensity of Li2MgTiO4: 0.002Mn4+, 0.1Ge4+ increased by 152% under 468 nm excitation, and the thermostability of emission intensity increases from 22% (y = 0) to 43% (y = 0.1), which is about twice as much. Finally, pc-LED device was fabricated via the red phosphor Li2MgTiO4: 0.002Mn4+,0.1Ge4+ coated on a 470 nm ultraviolet chip. By changing the proportion of the phosphor, the electroluminescence spectra of pc-LED device could match well with the absorption regions of plant pigments. Therefore, Li2MgTiO4: 0.002Mn4+, 0.1Ge4+ phosphor has potential application in plant lighting. Furthermore, this work can offer some helpful references for improving luminescent efficiency by simply modulating the chemical composition.

Structural and Spectroscopic Effects of Li+ Substitution for Na+ in LixNa1-xCaGd0.5Ho0.05Yb0.45(MoO4)(3) Scheelite-Type Upconversion Phosphors

Lim, Chang-Sung; Aleksandrovsky, Aleksandr; Molokeev, Maxim; Oreshonkov, Aleksandr; Atuchin, Victor // Molecules/

 https://doi.org/10.3390/molecules26237357

A set of new triple molybdates, LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45, was successfully manufactured by the microwave-accompanied sol–gel-based process (MAS). Yellow molybdate phosphors LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45 with variation of the LixNa1-x (x = 0, 0.05, 0.1, 0.2, 0.3) ratio under constant doping amounts of Ho3+ = 0.05 and Yb3+ = 0.45 were obtained, and the effect of Li+ on their spectroscopic features was investigated. The crystal structures of LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) at room temperature were determined in space group I41/a by Rietveld analysis. Pure NaCaGd0.5Ho0.05Yb0.45(MoO4)3 has a scheelite-type structure with cell parameters a = 5.2077 (2) and c = 11.3657 (5) Å, V = 308.24 (3) Å3, Z = 4. In Li-doped samples, big cation sites are occupied by a mixture of (Li,Na,Gd,Ho,Yb) ions, and this provides a linear cell volume decrease with increasing Li doping level. The evaluated upconversion (UC) behavior and Raman spectroscopic results of the phosphors are discussed in detail. Under excitation at 980 nm, the phosphors provide yellow color emission based on the 5S2/5F4 → 5I8 green emission and the 5F5 → 5I8 red emission. The incorporated Li+ ions gave rise to local symmetry distortion (LSD) around the cations in the substituted crystalline structure by the Ho3+ and Yb3+ ions, and they further affected the UC transition probabilities in triple molybdates LixNa1-xCaGd0.5(MoO4)3:Ho3+0.05/Yb3+0.45. The complex UC intensity dependence on the Li content is explained by the specificity of unit cell distortion in a disordered large ion system within the scheelite crystal structure. The Raman spectra of LixNa1-xCaGd0.5(MoO4)3 doped with Ho3+ and Yb3+ ions were totally superimposed with the luminescence signal of Ho3+ ions in the range of Mo–O stretching vibrations, and increasing the Li+ content resulted in a change in the Ho3+ multiplet intensity. The individual chromaticity points (ICP) for the LiNaCaGd(MoO4)3:Ho3+,Yb3+ phosphors correspond to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates

Why the Magnetite-Gold Core-Shell Nanoparticles Are Not Quite Good and How to Improve Them

Sokolov, A. E.; Ivanova, O. S.; Fedorov, A. S.; Kovaleva, E. A.; Vysotin, M. A.; et al.// Physics Of The Solid State/

DOI: https://doi.org/10.1134/S1063783421090365

The nature of the formation of a chemical bond at the magnetite–gold interface has been studied. The geometric structure and the electronic and magnetic properties of plane layers consisting of magnetite Fe3O4 and gold have been investigated using the DFT-GGA calculation. It has been found that the specific energy and the wetting parameter of the magnetite–gold interface are negative, which leads to the island growth of small Au particles on the Fe3O4 surface. The role of an intermediate thin titanium layer between magnetite and gold has been discussed. The specific energy and wetting parameter of the magnetite–titanium (for thin Ti layers) and magnetite–titanium–gold interfaces are positive. It has been suggested that an intermediate thin titanium layer at the interface between the magnetite nanoparticle surface and the gold layer will make it possible to obtain magnetite nanoparticles with a continuous gold coating.

The Magneto-Optical Voigt Parameter from Magneto-Optical Ellipsometry Data for Multilayer Samples with Single Ferromagnetic Layer

Maximova, O.; Lyaschenko, S.; Tarasov, I; Yakovlev, I; Mikhlin, Y.; et al. // Physics Of The Solid State/

https://link.springer.com/article/10.1134%2FS1063783421090274

Calculations of the magneto-optical Voigt parameter Q were carried out using various models of reflecting media for thin films Fe|SiO2|Si(100) samples using the data of the in situ magneto-ellipsometry. The obtained spectral dependences of Q make it possible to choose the algorithm for the analysis of experimental magneto-ellipsometry data and demonstrate that magneto-optical parameter Q of iron is thickness-dependent.

Ground State of a Two-Sublattice Anisotropic Ferromagnet in a Magnetic Field

Martynov, S. N. // Physics Of The Solid State/

https://doi.org/10.1134/S1063783421080199

The ground state of a classical two-sublattice ferromagnet with the noncollinear single-ion anisotropy axes of the sublattices and the antisymmetric and anisotropic symmetric exchanges between them has been investigated in a magnetic field applied along the hard magnetization directions in the crystal. The threshold relations for the parameters of the anisotropic interactions have been obtained, which determine the choice of the ground state among the three possible magnetic phases. Depending on the ground state type and the field direction, the transition between the phases is a first- or second-order phase transition. The antisymmetric exchange value above which the reorientation between the noncollinear phases ends with a second-order transition depends on the angle between the local easy axes and the single-ion anisotropy value. Field dependences of the magnetization and susceptibility for different ground states have been calculated. A comparison with the results of the magnetic measurements in the highly anisotropic PbMnBO4 ferromagnet has been made.

Temperature dependent structural, dielectric, Raman, piezoresponse and photoluminescence investigations in sol-gel derived BCZT ceramics

Indrani Coondoo, Alexander Krylov, Dhananjay K.Sharma, Svetlana Krylova, Denis Alikin, J. Suresh Kumar, A.Mirzorakhimov, Nina Melnikova, Manuel J.Soares, Andrei L. Kholkin/ MATERIALS CHEMISTRY AND PHYSICS/

https://doi.org/10.1016/j.matchemphys.2021.125526

0.5Ba(Ti0.8Zr0.2)O3-0.5(Ba0.7Ca0.3)TiO3 [50BZT-50BCT or BCZT] based compounds have been the focus of a lot of research, particularly motivated by their high piezoelectric effect. However, the literature lacks an elaborate investigation of the phase transition behavior in BCZT ceramics obtained by wet chemistry processing. Here, we present an in-depth study on the temperature dependence of x-ray diffraction (XRD), Raman scatteringdielectric properties, local piezoresponse and photoluminescence (PL) to investigate the sequence of phase transitions in the BCZT ceramic synthesized via a chemical route. Phase formation was determined by Rietveld analysis of XRD data, while compositional homogeneity and elemental quantification of the compound was validated using energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS) studies. Detailed fitting of XPS data indicated the existence of Ti3+ species (∼6%) in the prepared BCZT. Phase transitions were examined by analyzing the modifications in the XRD profile of Bragg reflection {200} and anomalies observed in the temperature variation of dielectric and Raman spectra studied over a wide temperature range starting from 10K to beyond Curie temperature. Crystallographic transformation temperatures obtained from dielectric measurement agreed well with those assessed from the temperature evolution of Raman spectra. In addition to other transitions, Raman scattering results revealed the existence of a transition from R3c to R3m phase near −175 °C, a transition that has not been interpreted in BCZT (and generally not observed in parent BaTiO3 compound). The luminescence response was studied by photoluminescence (PL) spectroscopy in the temperature range 15–300 K. The position of the PL peak was observed to shift with temperature and discontinuities in the wavelength shift were noted near phase transitions. Evolution of domain morphology with temperature was examined by piezoresponse force microscopy technique.

Solid-State NMR Free Induction Decay, Simulated by the System of Classical Magnetic Moments and Quantum Correlations

Lundin, AA and Zobov, VE/ RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY/

DOI: https://doi.org/10.1134/S1990793121050079

In the past decade, nuclear magnetic resonance (NMR) has been actively used to study the basic principles of quantum computers. It is assumed that quantum correlations play a significant role in their performance. They exist at both low and high temperatures. At the same time, the time correlation functions of nuclear spin systems of solids determine the observed signals in traditional NMR implementations. The separation of such signals into quantum and classical components has not previously been carried out and will be performed in this study for the most important of the correlational functions observed in magnetic resonance: the free induction decay (FID).

Heat Capacity and Thermodynamic Functions of GdGaTi2O7 in the Temperature Range of 320-1000 K

L. T. Denisova, M. S. Molokeev, L. G. Chumilina, V. V. Ryabov & V. M. Denisov Physics of the Solid State

DOI: https://doi.org/10.1134/S1063783421040065

Titanate GdGaTi2O7 has been obtained from the initial oxides Gd2O3, Ga2O3, and TiO2 by the solid-state synthesis via annealing in air at temperatures of 1273 and 1573 K. The crystal structure of the titanate has been refined by X-ray diffraction. The high-temperature (320–1000 K) heat capacity of the compound has been measured by differential scanning calorimetry. Based on the experimental dependence Cp = f(T), the main thermodynamic functions of the titanate have been calculated.

Synthesis and Structural, Magnetic, and Thermal Properties of the Titanium-Doped Pb3Mn7O15 Compound

Sofronova, SN, Eremin, EV, Molokeev, MS, Mikhashenok, NV, Kartashev, AV PHYSICS OF THE SOLID STATE

DOI: https://doi.org/10.1134/S1063783421040223

The Pb3Mn7O15 crystals doped with titanium ions have been synthesized. The study of the structural properties has shown that titanium ions occupy positions in the interplane columns, which weakens the exchange coupling between the planes. Two anomalies in the temperature dependences of magnetization and heat capacity at 62 and 35 K have been found. It has been supposed that, at 62 K, the long-range magnetic order arises and, at 35 K, a spin-reorientation transition, as in the Pb3Mn7O15 compound, occurs.

Effect of Electron and Hole Doping on the Transport Characteristics of Chalcogenide Systems

Romanova, O. B.; Aplesnin, S. S.; Udod, L., V/ Physics Of The Solid State/

https://doi.org/10.1134/S1063783421050152

The electrical properties of the Ag0.01Mn0.99S and Tm0.01Mn0.99S semiconductor compounds and the Hall effect in them have been investigated in the temperature range of 80–400 K in a magnetic field of 12 kOe. Using the I–V characteristics, the conductivity mechanism depending on the doping type and concentration has been established. Upon substitution of silver for manganese, the Mott-type conductivity has been found, while substitution of thulium causes the ohmic conductivity. The mobility and type of carriers have been determined from the Hall constant data.

Synthesis and Structural and Magnetic Properties of the NaNiFe2(VO4)(3) Compound

Drokina, T., V; Velikanov, D. A.; Bayukov, O. A.; Molokeev, M. S.; Petrakovskii, G. A./ Physics Of The Solid State/

https://doi.org/10.1134/S1063783421060056

A new magnetic compound NaNiFe2(VO4)3 has been obtained by the solid-phase synthesis and studied by X-ray diffractometry, nuclear gamma resonance, and magnetometry. The crystal structure of multicomponent vanadate is described by a triclinic symmetry space group P1. The unit cell contains six nonequivalent mixed cationic positions occupied by different-valence ions of transition metals, iron Fe3+ and nickel Ni2+, which facilitates the implementation of a state with the local charge neutrality violation. In addition, two types of iron atom sites have been found, which have an oxygen environment in the form of octahedra and square pyramids with their nonequiprobable population by iron and nickel. The temperature and field dependences of the magnetization have been found to be typical of a paramagnet containing ferromagnetic clusters in a wide temperature range.

Universal Behavior and Temperature Evolution of the Magnetoresistance Hysteresis in Granular High-Temperature Superconductors Y-Ba-Cu-O

Semenov, S., V; Balaev, D. A.; Petrov, M., I/ Physics Of The Solid State/

https://doi.org/10.1134/S1063783421070192

Regularities in the behavior of the magnetoresistance hysteresis R(H) in the granular yttrium high-temperature superconductors (HTSs) have been established. For this purpose, a comparative analysis of the magnetotransport properties has been carried out on the granular HTS samples, which exhibit (i) approximately the same magnetic properties and temperatures of the onset of the superconducting transition (90.5–93.5 K, which is characteristic of HTS grains) and (ii) different critical transport currents JC (which is characteristic of grain boundaries). Despite a significant (by more than an order of magnitude) spread of the JC values for the three samples, a universal behavior of the magnetoresistance hysteresis has been found, which is apparently inherent in all the granular Y–Ba–Cu–O compounds. The R(H) hysteresis is extremely broad and, in a fairly wide external field range, the dependence of the magnetoresistance hysteresis width ΔН on the field Hdec (the external field for the decreasing hysteresis branch is Н = Hdec) is almost linear: ΔH ≈ Hdec. This behavior is observed over the entire temperature range of implementation of the superconducting state (the investigations have been carried out at temperatures of 77–88 and 4.2 K). The result obtained has been explained by considering the effective field in grain boundaries, which is a superposition of the external field and the field induced by the magnetic moments of grains. The field induced by grains, in turn, significantly increases in the region of grain boundaries due to the magnetic flux compression (the grain boundary length is shorter than the HTS grain size by several orders of magnitude). The aforesaid has been confirmed by the analysis of the R(H) hysteresis for the Y–Ba–Cu–O- and CuO-based HTS composite, in which the grain boundary length is purposefully increased; as a result, the flux compression is less pronounced and the R(H) hysteresis narrows.

Magnetic and Magnetoelectric Properties of Scandoborate NdSc3(BO3)(4)

Eremin, E., V; Dubrovskii, A. A.; Gudim, I. A.; Titova, V. R.; Merkulov, M., V/ Physics Of The Solid State/

https://doi.org/10.1134/S1063783421070052

Trigonal neodymium scandoborate NdSc3(BO3)4 single crystals have been grown by the batch flux method using bismuth trimolybdate and their magnetic and magnetoelectric properties have been investigated in the temperature range of 4.2–300 K in magnetic fields of up to 9 T. Magnetically, the compound is a paramagnet and its properties are determined by the magnetic properties of the Nd3+ ion with allowance for the Van Vleck paramagnetic correction. The magnetoelectric polarization value has been found to be comparable with that of the previously investigated diluted neodymium aluminum borate Nd0.35Y0.65Al3(BO3)4. The latter circumstance opens up another subclass of compounds that should exhibit the giant magnetoelectric effect.

C-11-radiolabeled aptamer for imaging of tumors and metastases using positron emission tomography- computed tomography

Ozerskaya, Anastasia, V; Zamay, Tatiana N.; Kolovskaya, Olga S.; Tokarev, Nikolay A.; Belugin, Kirill, V; et al./ Molecular Therapy-nucleic Acids/

https://doi.org/10.1016/j.omtn.2021.10.020

Identification of primary tumors and metastasis sites is an essential step in cancer diagnostics and the following treatment. Positron emission tomography-computed tomography (PET/CT) is one of the most reliable methods for scanning the whole organism for malignancies. In this work, we synthesized an 11C-labeled oligonucleotide primer and hybridized it to an anti-cancer DNA aptamer. The 11C-aptamer was applied for in vivo imaging of Ehrlich ascites carcinoma and its metastases in mice using PET/CT. The imaging experiments with the 11C-aptamer determined very small primary and secondary tumors of 3 mm2 and less. We also compared 11C imaging with the standard radiotracer, 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG), and found better selectivity of the 11C-aptamer to metastatic lesions in the metabolically active organs than 18F-FDG. 11C radionuclide with an ultra-short (20.38 min) half-life is considered safest for PET/CT imaging and does not cause false-positive results in heart imaging. Its combination with aptamers gives us high-specificity and high-contrast imaging of cancer cells and can be applied for PET/CT-guided drug delivery in cancer therapies.

Understanding the Energy Barriers of the Reversible Ion Exchange Process in CsPbBr1.5Cl1.5@Y2O3:Eu3+ Macroporous Composites and Their Application in Anti-Counterfeiting Codes

Li, M; Zhao, YF; (...); Ye, S et. all/ ACS APPLIED MATERIALS & INTERFACES/

https://doi.org/10.1021/acsami.1c18030

The photoinduced reversible ion exchanges in mixed halide perovskites and the resulting luminescent variations make them promising for constructing anti-counterfeiting patterns; however, its understanding in an interfacial view is lacking. In this work, nominal CsPbBr1.5Cl1.5 (CPBC) nanocrystals (NCs) were introduced into macroporous Y2O3:Eu3+ (MYE) to realize emission color variations from red emission of MYE to green emission of halide NCs. The large surface area of MYE helps the formation of Y–Cl/Br bonds which induces fluctuation in the halide composition, while water and intrinsic halogen defects have also been proved to be essential in the reversible ion segregation process. The PL variations of several samples with different pore sizes were investigated upon irradiation of light with different photon energies and excitation power at certain temperatures. According to combined results of density functional theory calculation, the research reveals the presence of two energy barriers that would be overcome correspondingly by the excitation photon and the concentration difference in the ion exchange and recovery process. A photochromic anti-counterfeiting quick response (QR) code was constructed facilely with the perovskite composites. This work provides a deeper understanding from the interfacial aspect and also proposes a feasible strategy to realize reversible PL variation for anti-counterfeiting applications.

Exploration of the structural, spectroscopic and thermal properties of double sulfate monohydrate NaSm(SO4)(2)center dot H2O and its thermal decomposition product NaSm(SO4)(2)

Denisenko, YG; Sedykh, AE; (...); Muller-Buschbaum, K et. all./ ADVANCED POWDER TECHNOLOGY/

https://doi.org/10.1016/j.apt.2021.08.009

Samarium-sodium double sulfate crystalline hydrate NaSm(SO4)2·H2O was obtained by the crystallization from an aqueous solution containing equimolar amounts of ions. The anhydrous salt of NaSm(SO4)2 was formed by a thermally induced release of the equivalent of water from NaSm(SO4)2·H2O. The kinetic parameters of thermal decomposition were determined (Ea = 102 kJ/mol, A = 9·106). The crystal structures of both compounds were refined from the X-ray powder diffraction data. Sulfate hydrate NaSm(SO4)2·H2O crystallizes in the trigonal symmetry, space group P3121 (a = 6.91820(3) and c = 12.8100(1) Å, V = 530.963(7) Å3). The anhydrous salt crystallizes in the triclinic symmetry, space group P-1 (a = 6.8816(2), b = 6.2968(2) and c = 7.0607(2) Å, α = 96.035(1), β = 99.191(1) and γ = 90.986(1)°, V = 300.17(1) Å3). The vibrational properties of compounds are mainly determined by the sulfate group deformations. The luminescence spectra of both sulfates are similar and are governed by the transitions of samarium ions 4G5/2 → 6HJ (J = 5/2, 7/2, 9/2 and 11/2). The anhydrous sulfate is stable up to 1100 K and undergoes an almost isotropic expansion when heated. After 1100 K, the compound decomposes into Sm2(SO4)3 and Na2SO4.

Implanted gallium impurity detection in silicon by impedance spectroscopy

Tetelbaum, David; Nikolskaya, Alena; Dorokhin, Mikhail; Vasiliev, Valery; Smolyakov, Dmitriy; et al. Materials Letters

https://doi.org/10.1016/j.matlet.2021.131244

The results of determining the energy levels of boron-doped silicon implanted with gallium ions by impedance spectroscopy are reported. In the as-implanted sample the boron level remains the same and a second level appears close to the Ga-level reported in literature. In the sample annealed at 1000 °C, two levels are observed neither of which corresponds to the literature values for boron and gallium. It is assumed that in the as-implanted sample this method detects levels of gallium atoms located at a depth where ions penetrate due to the channeling effect, since a large concentration of defects at shallower depths does not allow detection of energy levels due to the Fermi level pinning. Explaining the results for the sample annealed after implantation requires additional research. The main result of this work is to establish the possibility of detecting impurity levels in ion-implanted silicon by impedance spectroscopy even in the absence of subsequent annealing.

Thermal degradation of optical resonances in plasmonic nanoparticles

Sorensen, Lasse K.; Khrennikov, Daniil E.; Gerasimov, Valeriy S.; Ershov, Alexander E.; Vysotin, Maxim A.; et al. / Nanoscale

DOI: https://doi.org/10.1039/D1NR06444D

The dependence of plasmon resonance excitations in ultrafine (3–7 nm) gold nanoparticles on heating and melting is investigated. An integrated approach is adopted, where molecular dynamics simulations of the spatial and temporal development of the atoms constituting the nanoparticles generate trajectories out of which system conformations are sampled and extracted for calculations of plasmonic excitation cross sections which then are averaged over the sample configurations for the final result. The calculations of the plasmonic excitations, which take into account the temperature- and size-dependent relaxation of the plasmons, are carried out with a newly developed Extended Discrete Interaction Model (Ex-DIM) and complemented by multilayered Mie theory. The integrated approach clearly demonstrates the conditions for suppression of the plasmons starting at temperatures well below the melting point. We have found a strong inhomogeneous dependence of the atom mobility in the particle crystal lattice increasing from the center to its surface upon the temperature growth. The plasmon resonance suppression is associated with an increase of the mobility and in the amplitude of phonon vibrations of the lattice atoms accompanied by electron–phonon scattering. This leads to an increase in the relaxation constant impeding the plasmon excitation as the major source of the suppression, while the direct contribution from the increase in the lattice constant and its chaotization at melting is found to be minor. Experimental verification of the suppression of surface plasmon resonance is demonstrated for gold nanoparticles on a quartz substrate heated up to the melting temperature and above.

Synthesis, Crystal Structure, and Thermodynamic Properties of CuSm2Ge2O8

Denisova, L. T.; Molokeev, M. S.; Kargin, Yu F.; Irtyugo, L. A.; Belousova, N., V; et al. / Russian Journal Of Inorganic Chemistry/

DOI: https://doi.org/10.1134/S0036023621120020

Copper samarium germanate CuSm2Ge2O8 have been synthesized by the ceramic method from CuO, Sm2O3, and GeO2 in air at the final calcination temperature 1273 K (200 h), and its crystal structure has been determined (space group Cm; a = 9.7592(2) Å, b = 15.2608(4) Å, c = 8.2502(2) Å, β = 148.2566(8)°, V = 646.46(3) Å3). The temperature dependence of the molar heat capacity Cp = f(T) measured in the temperature range 350–1000 K shows a maximum at Tmax = 498.5 K caused by the phase transition. Thermodynamic properties have been calculated from experimental data.

Phonon-assisted insulator-metal transitions in correlated systems driven by doping

Shneyder, E., I; Zotova, M., V; Nikolaev, S., V; Ovchinnikov, S. G. / Physical Review B/

DOI:https://doi.org/10.1103/PhysRevB.104.155153

We consider how electron-phonon interaction influences the insulator-metal transitions driven by doping in a strongly correlated system. Using the polaronic version of the generalized tight-binding method, we investigate a multiband two-dimensional model taking into account both charge density displacement and transitive types of electron-lattice contributions. For adiabatic ratio tω0, we analyze a wide electron-phonon parameter range and demonstrate the relationship between transition features and such properties of the system as polaron and bipolaron crossovers, the redistribution of the spectral weight due to the multiparticle effects of Coulomb and electron-phonon interactions, orbital selectivity, flat-band formation, and pseudogap behavior of various origins.

Protein biosensor based on Schottky barrier nanowire field effect transistor

Smolyarova, Tatyana E.; Shanidze, Lev, V; Lukyanenko, Anna, V; Baron, Filipp A.; Krasitskaya, Vasilisa V.; et al. Talanta

https://doi.org/10.1016/j.talanta.2021.123092

A top-down nanofabrication approach involving molecular beam epitaxy and electron beam lithography was used to obtain silicon nanowire-based back gate field-effect transistors with Schottky contacts on silicon-on-insulator (SOI) wafers. The resulting device is applied in biomolecular detection based on the changes in the drain-source current (IDS). In this context, we have explained the physical mechanisms of charge carrier transport in the nanowire using energy band diagrams and numerical 2D simulations in TCAD. The results of the experiment and numerical modeling matched well and may be used to develop novel types of nanowire-based biosensors.

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