New Publications

Electrical Properties of Thin In2O3/C Films

Babkina, I. V.; Volochaev, M. N.; Zhilova, O. V.; Kalinin, Yu. E.; Makagonov, V. A.; et al. Inorganic Materials. DOI: 10.1134/S0020168520040019

We have studied the structure and electrical properties of thin films based on the In2O3 semiconductor and carbon, grown by atomic layer deposition using ion-beam sputtering. The structure of the resultant materials, formed during layer-by-layer growth of island layers, is made up of nanocrystalline In2O3 granules distributed at random over amorphous carbon. The electrical transport properties of the In2O3/C thin films depend on their thickness. In the temperature range 80–300 K, the dominant electrical transport mechanism in the In2O3/C thin films of thickness h < 70 nm sequentially changes from variable range hopping between localized states in a narrow energy band near the Fermi level (between 80 and 120 K) to nearest neighbor hopping (between 120 and 250 K) and then to variable range hopping between localized states in the conduction band tail (between 250 and 300 K). The films of thickness h > 70 nm undergo a change from conduction associated with strong carrier localization to that due to the presence of percolation clusters formed by In2O3 nanocrystals, which shows up as a linear temperature dependence of conductivity, with a negative temperature coefficient.

Magnetoresistive effect in the cobalt-doped bismuth ferrite films

Romanova, O. B.; Aplesnin, S. S.; Sitnikov, M. N.; Udod, L., V; Begisheva, O. B.; et al. Journal Of Materials Science-materials In Electronics. https://doi.org/10.1007/s10854-020-03333-7

Bismuth ferrite flms have been synthesized by the burst-mode deposition of the BiFe0.8Co0.2O3 solid solutions onto object glasses. The surface morphology of the BiFe0.8Co0.2O3 flms has been examined. The efect of electron doping implemented by substitution of cobalt for iron in the BiFe0.8Co0.2O3 flms on their magnetic, electrical, and galvanomagnetic properties has been investigated at temperatures of 77‒600 K in magnetic felds of up to 12 kOe. The negative magnetoresistance has been observed, which changes its sign in the region of formation of magnetically heterogeneous states and attain its maximum value above room temperature. It has been established that the magnetoresistance is caused by the competition of electron hoppings and localization of electrons in a magnetic feld. Using the Hall measurements, the carrier type has been determined. A model of the change in the curriers sign upon heating due to the shift of the chemical potential relative to the impurity subband has been proposed.

Effect of Multiplicity Fluctuation in Cobalt Ions on Crystal Structure, Magnetic and Electrical Properties of NdCoO3 and SmCoO3

Dudnikov, Vyacheslav A.; Orlov, Yuri S.; Solovyov, Leonid A.; Vereshchagin, Sergey N.; Gavrilkin, Sergey Yu.; et al. Molecules. doi:10.3390/molecules25061301

The structural, magnetic, electrical, and dilatation properties of the rare-earth NdCoO3 and SmCoO3 cobaltites were investigated. Their comparative analysis was carried out and the effect of multiplicity fluctuations on physical properties of the studied cobaltites was considered. Correlations between the spin state change of cobalt ions and the temperature dependence anomalies of the lattice parameters, magnetic susceptibility, volume thermal expansion coefficient, and electrical resistance have been revealed. A comparison of the results with well-studied GdCoO3 allows one to single out both the general tendencies inherent in all rare-earth cobaltites taking into account the lanthanide contraction and peculiar properties of the samples containing Nd and Sm.

Antiferromagnetism of the cation-ordered warwickite system Mn2-xMgxBO4 (x=0.5, 0.6 and 0.7)

Kazak, N., V; Belskaya, N. A.; Moshkina, E. M.; Bezmaternykh, L. N.; Vasiliev, A. D.; et al. Journal Of Magnetism And Magnetic Materials. https://doi.org/10.1016/j.jmmm.2020.166820

X-ray diffraction, heat capacity and magnetic measurements are performed on single crystals of Mn2-xMgxBO4 (x = 0.5, 0.6 and 0.7) with the warwickite structure. The monoclinic symmetry is found for all samples with the space group P21/n. The M1 site is occupied by trivalent Mn ions while the M2 site is occupied by a mixture of divalent Mg and Mn ions. Regular cation and charge distributions are observed, which is unusual for heterometallic warwickites. The local octahedral distortions of M1O6 show the monotonic dependence on the Mg content and are in accordance with the Jahn-Teller distortion. All samples are found to undergo long-range antiferromagnetic ordering with rather low transition temperatures of TN = 16, 14 and 13 K for x = 0.5, 0.6, and 0.7, respectively. The ordering of local octahedral distortions, caused by the strong electron-phonon interaction of the trivalent Mn ions, is proposed to stabilise the cationic ordering and, as a result, the long-range magnetic ordering in the material.

Spectroscopic Multirelaxation Dielectric Model of Thawed and Frozen Arctic Soils Considering the Dependence on Temperature and Organic Matter Content

Mironov, V. L.; Savin, I. V. Izvestiya Atmospheric And Oceanic Physics. DOI: 10.1134/S0001433819090305

A temperature spectroscopic dielectric model of moist soils developed on the basis of measurements of six samples of thawed and frozen Arctic soils with different contents of organic matter, from 30 to 90%, is presented. This model allows predicting complex permittivity values of moist soil that are in a good agreement with dielectric measurements. It is applicable in a frequency range from 0.05 to 15 GHz, a temperature range from ‒30° to +25°C, and a moisture range from 0.009 to 1.001 g/g. It can be recommended for use in remote sensing algorithms of moisture and temperature of soil using space radiometric and radar data.

Fine Structure of the Crossing Resonance Spectrum of Wavefields in an Inhomogeneous Medium

Ignatchenko, V. A.; Polukhin, D. S. Journal Of Experimental And Theoretical Physics. DOI: 10.1134/S1063776120010033

The crossing resonance of two wavefields m(x, t) and u(x, t) of different natures in an inhomogeneous medium with zero mean value of the coupling parameter eta between fields has been studied. ThThe crossing resonance of two wavefields m(x, t) and u(x, t) of different natures in an inhomogeneous medium with zero mean value of the coupling parameter η between fields has been studied. The stages of formation of the fine structure of the crossing resonance have been analyzed. It has been shown within the model of independent crystallites that the removal of the degeneracy of eigenfrequencies of these fields at the crossing resonance point has a threshold character in the coupling parameter and occurs under the condition η > ηc, where ηc = |Γu – Γm|/2, Γu and Γm are the relaxation parameters of the corresponding wavefields. At η > ηc, each random implementation of the Green’s functions and of wavefields has the form of two resonance peaks with the same half-width (Γu + Γm)/2 spaced by the interval 2η; this form is standard for crossing resonances. At η < ηc, the functions and are different: if Γu > Γm, the function has the form of a narrow resonance peak at ω = ωr , whereas the function has the form of a broader resonance peak split at the top by a narrow antiresonance. Averaging over regions where η > ηc leads to the formation of a broad resonance with a resonance line half-width of about η2  1/2 on the both averaged Green’s functions, which is due to the stochastic distribution of resonance frequencies. Averaging over regions where η < ηc results in the sharpening of a resonance peak on the function and an antiresonance peak on the function at the same frequency ω = ωr . As a result, a pattern of the crossing resonance in the inhomogeneous medium is formed, consisting of identical broad peaks on both functions with the narrow resonance peak of the fine structure on the function and the antiresonance peak on the function . Thus, the fine structure of the spectrum of any crossing resonance of two wavefields of different natures in the inhomogeneous medium is due to the contribution of random realizations corresponding to degenerate states of the natural oscillations of the system. In a ferromagnet with a spatially inhomogeneous coupling parameter, spin and elastic waves acquire damping parameters Γm(k) ∝ kc and Γu(k) ∝ kc proportional to the correlation wavenumber kc of inhomogeneities and to the velocities of the corresponding waves, which are summed with the homogeneous damping parameters Γm and Γu of the same waves. This situation has been considered in a new self-consisting approximation for the case where the contribution of homogeneous damping parameters is negligibly small. It has been shown that the form of the fine structure on the functions and at the second (high-frequency) crossing point of dispersion curves of spin and elastic waves changes to the opposite form: narrow resonance peaks of the fine structure appear on the function , and antiresonance peaks arise on the function because < and > at the first and second crossing points, respectively stages of formation of the fine structur...

Ab Initio Study of the Relation between the Structural, Magnetic, and Optical Properties of Normal and Inverse MnGa2O4 Spinels

Zhandun, V. S.; Nemtsev, A. V. Journal Of Experimental And Theoretical Physics. DOI: 10.1134/S106377612002017X

—The electronic, magnetic, and optical properties of MnGa2O4 in the structure of the normal and inverse spinels are subjected to an ab initio investigation and comparison. The generalized gradient approximation (GGA) predicts that the normal MnGa2O4 spinel is a semiconductor with a bandgap of about 0.7 eV, and a bandgap in the structure of the inverse spinel appears only in terms of the GGA + U approach. A simple exchange interaction model is used to calculate exchange integrals. In both structure types, MnGa2O4 exhibits antiferromagnetic behavior, and the normal structure is energetically favorable. The inverse spinel becomes energetically favorable only when a negative pressure is applied. The absorption spectra of the normal spinel are found to have a spectral window at a wavelength larger than 450 nm.

Effect of the Structural Properties on the Electrical Resistivity of the Al/Ag Thin Films during the Solid-State Reaction

Altunin, R. R.; Moiseenko, E. T.; Zharkov, S. M. Physics Of The Solid State. DOI: 10.1134/S1063783420040034

Based on the results of in situ electron diffraction study of the solid-state reaction and electrical resistivity measurements on the Al/Ag thin films with an atomic ratio of Al : Ag = 1 : 3, the temperature of the reaction onset has been established and a model of the structural phase transitions has been proposed. The solid-state reaction begins at 70°C with the formation of the Al–Ag solid solution at the interface between the aluminum and silver nanolayers. It has been found that, in the course of the reaction, the intermetallic compounds γ-Ag2Al → μ-Ag3Al are successively formed. It is shown that the possibility of the formation of the μ-Ag3Al phase during the solid-state reaction in the Al/Ag thin films depends on the aluminum-to-silver ratio, while the formation of the μ-Ag3Al phase begins only after all fcc aluminum has reacted.

Exchange Interactions in the Cr3+-Cr3+ Ion Pair in the ABO(3) (A = Ga, In, Sc) Diamagnetic Matrix

Vorotynov, A. M.; Rudenko, V. V.; Vorotynova, O. V. Physics Of The Solid State. DOI: 10.1134/S1063783420030257

The exchange interactions in the Cr3+–Cr3+ ion pairs in the isostructural ABO3 (A = Ga, In, Sc) diamagnetic compounds have been examined using the magnetic resonance technique. The values of bilinear and biquadratic exchange interactions have been determined. It is shown that the biquadratic exchange in the Cr3+–Cr3+ pair in these compounds is caused by the exchange striction.

HoFeTi2O7: Synthesis, Peculiarities of the Crystal Structure, and Magnetic Properties

Drokina, T. V.; Molokeev, M. S.; Velikanov, D. A.; Petrakovskii, G. A.; Bayukov, O. A. Physics Of The Solid State. DOI: 10.1134/S1063783420030075

Polycrystalline samples of HoFeTi2O7 were obtained by solid-phase synthesis and investigated using X-ray diffraction, gamma resonance, and SQUID measurements. Characteristics of the structural properties are presented, which give an evidence of the distribution of iron atoms among nonequivalent crystallographic positions and of the nonuniform populating of positions mixed with titanium by the iron atoms. Spin disorder caused by mixing of magnetic and nonmagnetic ions, spatial nonuniformity of the interactions defining the magnetic structure in the crystal lead to formation of concurrent magnetic exchange interactions between the nearest neighbors, frustration of magnetic couplings, and loss of the long-range magnetic ordering. The temperature dependence of the magnetic susceptibility at low temperatures was shown to have some peculiarities typical of the magnetic state of spin glass.

Glass-ceramics with thermally stable blue-red emission for high-power horticultural LED applications

W. Chen, X. Zhang, J. zhou, H. Zhang, J. Zhuang, Z. Xia, Y. Liu, M. S. Molokeev, G. Xie and B. Lei, J. Mater. Chem. C. 2020, DOI: 10.1039/D0TC00061B.

As one of the key elements for indoor agriculture, horticultural light sources are developing rapidly towards high energy density, high output power and high stability, which poses a challenge to traditional phosphor conversion devices. Grasping the nettle, all-inorganic blue-red dual-emitting light convertor consisting of Ba1.3Sr1.7MgSi2O8:Eu2+, Mn2+ (BSMS) phosphor in glass (PiG) plates were prepared to improve duration lifetime for high-power light-emitting diodes (LEDs) and meet the light quality requirements of photosynthesis for indoor agriculture. These obtained samples show an external quantum efficiency of 45.3%, outstanding thermal stability and specific emission spectrum that highly matched with the absorption of chlorophyll and β-carotene. Moreover, a proof-of-concept BSMS-PiG horticultural lamp for application in indoor plant factory was successfully fabricated base on ~370 nm emitting LED chip and the blue-red ratio of its spectrum was regulated by controlling the thickness of BSMS-PiG and the concentrations of Mn2+ ions in BSMS-PiG. The BSMS-PiG horticultural LEDs were applied in indoor cultivation of Romaine lettuce. The results indicated that biomass of Romaine lettuce was 58.21% greater than those cultivated under the light sources of commercial plant lamps. Especially, the content of total chlorophyll, β-carotene and soluble protein were improved. The BSMS-PiG horticultural LEDs is a potential candidate for high-power horticultural light source.

Unveiling Mn2+ Dopant States in Two-Dimensional Halide Perovskite toward Highly Efficient Photoluminescence

Su, Binbin; Molokeev, Maxim S.; Xia, Zhiguo. Journal Of Physical Chemistry Letters. DOI: 10.1021/acs.jpclett.0c00593

Doping is able to create novel optoelectronic properties of halide perovskites, and the involved mechanism on efficient emission is still a challenge. Herein, Mn2+ substitution into two-dimensional (2D) layered perovskites (C8H20N2)PbBr4 was investigated, demonstrating broad-band orangered emission originating from 4T1→6A1 transition of Mn2+ dopant. The photoluminescence quantum yield (PLQY) of Mn2+ emission is up to 60.8% related with the energy transfer in coupled states. We verify the actual Mn2+ dopant as low as 0.476% to reach the high PLQY, whereas the nominal adding amount is 0.8 as the Mn2+/Pb2+ ratio. The small activation energy (∼6.72 meV) between the Mn2+ d state and trap state accounts for this high efficient energy transfer and photoluminescence. The proposed luminescence mechanism in Mn2+ doped 2D halide perovskites would provide unique insights into the doping designing toward high performance luminescence materials.

Ferromagnetic Resonance Study of Biogenic Ferrihydrite Nanoparticles: Spin-Glass State of Surface Spins

Stolyar, S., V; Balaev, D. A.; Ladygina, V. P.; Pankrats, A., I; Yaroslavtsev, R. N.; et al. Jetp Letters. DOI: 10.1134/S0021364020030145

Ferrihydrite nanoparticles (2–3 nm in size), which are products of the vital activity of microorganisms, are studied by the ferromagnetic resonance method. The “core” of ferrihydrite particles is ordered antiferromagnetically, and the presence of defects leads to the appearance of an uncompensated magnetic moment in nanoparticles and the characteristic superparamagnetic behavior. It is established from the ferromagnetic resonance data that the field dependence of the frequency is described by the expression = , where γ is the gyromagnetic ratio, is the resonance field, kOe, and K. The induced anisotropy is due to the spin-glass state of the near-surface regions.

Structural, Electronic and Vibrational Properties of YAl3(BO3)(4)

Oreshonkov, Aleksandr S.; Roginskii, Evgenii M.; Shestakov, Nikolai P.; Gudim, Irina A.; Temerov, Vladislav L.; et al. Materials. doi:10.3390/ma13030545

The crystal structure of YAl3(BO3)4 is obtained by Rietveld refinement analysis in the present study. The dynamical properties are studied both theoretically and experimentally. The experimental Raman and Infrared spectra are interpreted using the results of ab initio calculations within density functional theory. The phonon band gap in the Infrared spectrum is observed in both trigonal and hypothetical monoclinic structures of YAl3(BO3)4. The electronic band structure is studied theoretically, and the value of the band gap is obtained. It was found that the YAl3(BO3)4 is an indirect band gap dielectric material.

Ion Exchange Recovery of Platinum(IV) from Hydrochloric Acid Solutions in the Presence of Silver(I)

Kononova, O. N.; Duba, E. V.; Efimova, A. S.; Ivanov, A. I.; Krylov, A. S. Russian Journal of Physical Chemistry A, 2020, Vol. 94, No. 4, pp. 828–834. DOI: 10.1134/S003602442004007X

The ion exchange sorption of the platinum(IV) chloride complexes in the presence of silver(I) chloro complexes from 2 and 4 M aqueous solutions of hydrochloric acid is studied on Purolite anion exchangers with different functional groups. The high selectivity of the investigated sorbents with respect to platinum during its recovery from individual hydrochloric acid solutions and in the presence of silver chloride complexes is determined. Since the latter are in this case virtually not sorbed in the presence of platinum(IV), they can be separated at the stage of sorption. The excellent kinetic properties of the investigated anion exchangers are revealed, allowing platinum to be eluted after its separation from silver chloro complexes in a dynamic mode.

Soft modes in HoFe2.5Ga0.5(BO3)(4) solid solution

Alexander Krylov, Svetlana Krylova, Irina Gudim & Alexander Vtyurin. Ferroelectrics. 2020, VOL. 556, 16–22 https://doi.org/10.1080/00150193.2020.1713334

The condensation of two soft modes has been found when studying the Raman spectra of the solid solution HoFe2.5Ga0.5(BO3)4 in the temperature range from 7 to 350 K. The first high-temperature soft mode is associated with the structural phase transition from the R32 phase to the P3121 phase. The second soft mode is related to the reveal of the phonon-magnon interaction during magnetic ordering in the crystal. The temperatures of the structural phase transition T1 ¼ 266 K and the magnetic phase transition T2 ¼ 28 K are established. Experimentally interaction between the structural phase transition order parameter fluctuations and the magnetic order parameter fluctuations was found.

Solvent effect in the theoretical absorption and emission spectra of fluorescein dyes

F. N. Tomilin; A. V. Rogova; E. V. Kaufman; A. S. Drevolsky; M. A. Gerasimova; E. A. Slyusareva. "Solvent effect in the theoretical absorption and emission spectra of fluorescein dyes", Proc. SPIE 11322, XIV International Conference on Pulsed Lasers and Laser Applications, 113220O (11 December 2019); https://doi.org/10.1117/12.2548739. Proceedings Volume 11322, XIV International Conference on Pulsed Lasers and Laser Applications; 113220O (2019) https://doi.org/10.1117/12.2548739 Event: XIV International Conference on Pulsed Lasers and Laser Applications (AMPL-2019), 2019, Tomsk, Russian Federation
Fluorescein and its halogenated derivatives representing a family of homologous dyes with the gradual substitution of halogen atoms for hydrogen ones are widely used in biomedicine as fluorescent probes. This stimulates the intense experimental and theoretical studies of their fluorescent properties in aqueous solutions. However, the theoretical calculations are complicated by the necessity of taking into account the effect of a solvent (water) in the explicit form and the need for effective basic sets. This is especially important for the dyes that contain heavy atoms. In this study, the quantum-chemical investigations of the dianionic form of fluorescein and its Br- and I-substituted derivatives (eosin Y and erythrosin B) have been carried out using the time-dependent density functional theory (B3LYP functional) implemented in the GAMESS software suite. The effect of a solvent has been considered in the framework of the modified Thomas polarizable continuum model. The calculations have been made for vertical (absorption and emission) excitations in the adiabatic approximation and at the nonequilibrium solvation. The results obtained for the nonequilibrium solvation are in excellent agreement with the experimental data for fluorescein and its halogenated derivatives.
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Aptamer-Conjugated Superparamagnetic Ferroarabinogalactan Nanoparticles for Targeted Magnetodynamic Therapy of Cancer

Kolovskaya, O. S., Zamay, T. N., Zamay, G. S., Babkin, V. A., Medvedeva, E. N., Neverova, N. A., … Kichkailo, A. S. Cancers, 12(1), 216. doi:10.3390/cancers12010216

Nanotechnologies involving physical methods of tumor destruction using functional oligonucleotides are promising for targeted cancer therapy. Our study presents magnetodynamic therapy for selective elimination of tumor cells in vivo using DNA aptamer-functionalized magnetic nanoparticles exposed to a low frequency alternating magnetic field. We developed an enhanced targeting approach of cancer cells with aptamers and arabinogalactan. Aptamers to fibronectin (AS-14) and heat shock cognate 71 kDa protein (AS-42) facilitated the delivery of the nanoparticles to Ehrlich carcinoma cells, and arabinogalactan (AG) promoted internalization through asialoglycoprotein receptors. Specific delivery of the aptamer-modified FeAG nanoparticles to the tumor site was confirmed by magnetic resonance imaging (MRI). After the following treatment with a low frequency

Synthesis of NdSc3(BO3)(4) single crystals and study of its structure properties

Evgeniy V. Eremin, Maxim S. Pavlovskiy, Irina A. Gudim, Vladislav Temerov, Maxim Molokeev, Nikita D. Andryushin, Evgeniy V. Bogdanov. Journal Of Alloys And Compounds. DOI: https://doi.org/10.1016/j.jallcom.2020.154355

Using the group method, single crystals of NdSc3(BO3)4 are grown from a melt solution and X-ray structural studies are performed. It is shown that at room temperature the NdSc3(BO3)4 crystal has a huntite-type structure with space group P3121. The temperature dependence of the heat capacity shows anomalous behaviour at Т = 504 ± 1 K. This anomaly corresponds to a structural phase transition from R32 to P3121. It is known that a similar transition occurs in RFe3(BO3)4 crystals; an anomaly in the specific heat is also observed. Theoretical calculations are carried out from the first principles of the lattice dynamics of the crystal under study in a high-symmetry phase with the R32 space group. An unstable (soft) mode in the boundary point of Brillouin zone was found. It was determined that this structural instability is responsible for the structural displacement-type phase transition R32 → P3121.

Melt-Solution Synthesis and Magnetic Properties of SmFe2.8Sc0.2(BO3)(4) Ferroborate

Gudim, I. A.; Eremin, E. V.; Temerov, V. L. Crystallography Reports. DOI: 10.1134/S1063774520020108

Single crystals of SmFe2.8Sc0.2(BO3)4 ferroborates are grown in melt‒solutions based on bismuth trimolybdate. The magnetic properties of grown single crystals are studied. The presence of long-range magnetic order in these crystals is found.

Polar anchoring energy and tilt angle measured by magneto-optical technique in nematic doped with ionic surfactant

Parshin, Alexander M.; Sutormin, Vitaly S.; Zyryanov, Victor Ya.; Shabanov, Vasily F. Liquid Crystals. DOI: 10.1080/02678292.2020.1733683

The surface anchoring of a nematic doped with the ionic surfactant has been investigated and compared with the one in the undoped sample. The director tilt angle at the substrates coated with the orienting polymer film has been determined by the null method in a rotating magnetic field. The Frederiks transition in a magnetic field has been chosen as a convenient technique to measure the polar anchoring energy Wθ. The temperature dependences of anchoring energy have been obtained for the various nematic cells. The Wθ values for nematic doped with the ionic surfactant are less than for the undoped one. The factors affecting the measurement accuracy have been discussed. The accuracy is higher for the thinner nematic layers and weaker anchoring energy

Spin-wave resonance in gradient ferromagnets with concave and convex variations of magnetic parameters

Ignatchenko, V. A.; Tsikalov, D. S. Journal Of Applied Physics. https://doi.org/10.1063/1.5143499

The theory of spin-wave resonance in gradient ferromagnetic films with magnetic parameters varying in space described by both concave and convex quadratic functions is developed. Gradient structures such as a potential well, a potential barrier, and a monotonic change in potential between the film surfaces for both quadratic functions are considered. The waveforms of oscillations mn(z), the laws of the dependence of discrete frequencies ωn, and relative susceptibilities χn=χ0 1 of spin-wave resonances on the resonance number n are studied. It is shown that the law ωn / n for n , nc, where nc is the resonance level near the upper edge of the gradient inhomogeneity, which is well known for a parabolic potential well, is also valid for the potential barrier and for the monotonic change in potential, if these structures are formed by a concave quadratic function. It is shown that the law ωn / (n 1=2)1=2 , which we numerically derived and approximated by the analytical formula, is valid for all three structures formed by a convex quadratic function. It is shown that the magnetic susceptibility χn of spin-wave resonances for n , nc is much greater than the susceptibility of resonances in a uniform film. An experimental study of both laws ωn(n) and χn(n) would allow one to determine the type of quadratic function that formed the gradient structure and the form of this structure. The possibility of creating gradient films with different laws ωn(n) and the high magnitude of the high-frequency magnetic susceptibility χn(n) at n , nc make these metamaterials promising for practical applications.

Comparative analysis of two methods for synthesis of fullerenes at different helium pressures

Alexander I. Dudnik, Irina V. Osipova, Nikita S. Nikolaev & Grigory N. Churilov. Fullerenes, Nanotubes and Carbon Nanostructures. DOI: 10.1080/1536383X.2020.1746281

The results of the effect of helium pressure in the chamber on the amount and composition of the produced fullerenes (C60, C70, etc.) synthesized in the arc plasma with graphite electrodes are presented. The findings obtained when the arc is powered by a direct (DC) and alternating (AC) currents of low frequency were compared in the same chamber with the electrodes located at the same angle to each other. These two methods are drastically different. The complete conversion of graphite into fullerene soot in AC occurs, but a part of the graphite is converted into a cathode deposit that does not contain fullerenes in DC, the relative amount of which increases when decreasing the helium pressure in the chamber. The highest fullerene content in fullerene soot of 10.2 wt.% is produced at a pressure of 127.5 kPa in AC arc, but in DC arc, the highest content of fullerenes in fullerene soot of 8.3 wt.% is produced at a pressure of 33.3 kPa.

Gapless Chiral Superconducting (d plus id)-Wave Phase in Strongly Correlated Layered Material with a Triangular Lattice

Val'kov, V. V.; Val'kova, T. A.; Mitskan, V. A. Journal of Experimental and Theoretical Physics volume 130, pages235–246(2020). DOI: https://doi.org/10.1134/S1063776120010197

It is shown that interlayer electron tunneling in the quasi-two-dimensional ensemble of Hubbard fermions leads to the realization of the gapless superconducting phase with the chiral (d + id)-wave order parameter symmetry, not for a single value of sodium ion concentration, but in a wide range of concentrations. Precisely this situation corresponds to experimental data on the layered sodium cobaltite intercalated by water (NaxCoO2 ⋅ yH2O). Intra-atomic electron repulsion that determines the strong electron correlation regime leads to the representation of Hubbard fermions, the interaction of which ensures Cooper instability. Intersite intralayer interactions between fermions considerably affect the positions of nodal points of the chiral order parameter and change the critical concentration at which a topological transition occurs in the 2D system of Hubbard fermions.

Effect of the Deposition Conditions on the Anion Resin Exchange Precipitation of Indium(III) Hydroxide

Evsevskaya, Natalia; Pikurova, Elena; Saikova, Svetlana, V; Nemtsev, Ivan Vasilievich. Acs Omega. https://dx.doi.org/10.1021/acsomega.9b03877

A new patented method for the synthesis of nanosized powders of indium(III) hydroxide and oxide using the strong base anion exchange resin AV-17-8 as a precipitate agent was proposed. The effect of anions of the initial indium salt and the influence of the process duration, temperature, and counterions of resin such as hydroxide or carbonate on the yield of indium(III) hydroxide during the anion resin exchange precipitation were investigated by scanning electron microscopy, electrical conductivity measurement method, and atomic absorption analysis. Based on the obtained data, the mechanism of the anion resin exchange precipitation of indium(III) hydroxide was suggested. The products were characterized by X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, elemental analysis, Brunauer−Emmett−Teller, and transmission electron microscopy. It was found that impurity-free monophasic In2O3 powders with an average particle size of 10−15 nm and specific surface area of 62−73 m2 /g were formed after heat treatment of as-prepared products at 400 °C.

Doping and temperature evolution of pseudogap and spin-spin correlations in the two-dimensional Hubbard model

Kuz’min, V. I., Visotin, M. A., Nikolaev, S. V., & Ovchinnikov, S. G. PHYSICAL REVIEW B 101, 115141 (2020). DOI: 10.1103/PhysRevB.101.115141

Cluster perturbation theory is applied to the two-dimensional Hubbard t − t − t − U model to obtain doping and temperature-dependent electronic spectral function with 4 × 4 and 12-site clusters. It is shown that evolution of the pseudogap and electronic dispersion with doping and temperature is similar and in both cases it is significantly influenced by spin-spin short-range correlations. When short-range magnetic order is weakened by doping or temperature and Hubbard-I-like electronic dispersion becomes more pronounced, the Fermi arc turns into a large Fermi surface and the pseudogap closes. It is demonstrated how static spin correlations impact the overall dispersion’s shape and how accounting for dynamic contributions leads to momentum-dependent spectral weight at the Fermi surface and broadening effects.

Ferromagnetic and Spin-Wave Resonance in the [CoFe/Cu](N) Superlattice Thin (30-nm) Film

Vazhenina, I. G., Iskhakov, R. S., Rautskii, M. V., Milyaev, M. A., & Naumova, L. I. Physics of the Solid State. DOI: 10.1134/S1063783420010357

Angular dependences of the microwave absorption spectra of a (CoFe/Cu)N multilayer film have been studied by the ferromagnetic and spin-wave resonance techniques. The critical angle θc indicating the ranges of excitation of uniform and nonuniform spin modes, type of the boundary conditions, and surface anisotropy and exchange coupling constants have been established. It is shown that the accuracy of identification of individual modes in the spectra plays a key role in the analysis of the detected curves.

Structural Phase Transformations during a Solid-State Reaction in a Bilayer Al/Fe Thin-Film Nanosystem

Altunin, R. R., Moiseenko, E. T., & Zharkov, S. M. Physics of the Solid State, 2020, Vol. 62, No. 1, pp. 200–205. DOI: 10.1134/S1063783420010059

The processes of phase formation during a solid-state reaction between Fe and Al nanolayers have been investigated by the in situ electron diffraction method. It is established that the solid-state reaction at the interface between iron and aluminum nanolayers begins at ≈100°C with the formation of a disordered Al solid solution in α-Fe. It is shown that intermetallic phases (FeAl6 and/or Fe2Al5, FeAl, and Fe3Al) are successively formed upon further heating.

Processes underlying the laser photochromic effect in colloidal plasmonic nanoparticle aggregates

Ershov, A. E., Gerasimov, V. S., Isaev, I. L., Gavrilyuk, A. P., & Karpov, S. V. Chinese Phys. B. https://doi.org/10.1088/1674-1056/ab6551

We have studied the dynamic and static processes occurring in disordered multiparticle colloidal Ag aggregates with natural structure and affecting their plasmonic absorption spectra under pico- and nanosecond pulsed laser radiations, as well as the physical origin responsible for these processes. We have shown that depending on the duration of the laser pulse, the mechanisms of laser modification of such aggregates can be associated both with changes in the resonant properties of the particles due to their heating and melting (picosecond irradiation mode) and with the particle shifts in the resonant domains of the aggregates (nanosecond pulses) which depend on the wavelength, intensity, and polarization of the radiation. These mechanisms result in formation of a narrow dip in the plasmonic absorption spectrum of the aggregates near the laser radiation wavelength and affect the shape and position of the dip. The effect of polydispersity of nanoparticle aggregates on laser photochromic reaction has been studied.

CoPt-Al2O3 Nanocomposite Films: Synthesis, Structure, and Magnetic Properties

Zhigalov, V. S., Bykova, L. E., Myagkov, V. G., Pavlova, A. N., Volochaev, M. N., Matsynin, A. A., & Patrin, G. S. Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques. DOI: 10.1134/S102745102001022X

―The structure and magnetic properties of CoPt–Al2O3 nanocomposite films synthesized by the annealing of Al/(Co3O4 + Pt) bilayers on a MgO(001) substrate at 650°C in vacuum are investigated. The synthesized composite films contain ferromagnetic CoPt grains with an average size of 25–45 nm enclosed in a nonconducting Al2O3 matrix. The saturation magnetization (Ms ~ 330 G) and coercivity (Hc ≈ 6 kOe) of the films are measured in the film plane and perpendicular to it. The obtained films are characterized by a spatial rotational magnetic anisotropy, which makes it possible to arbitrarily set the easy magnetization axis in the film plane or perpendicular to it using a magnetic field stronger than the coercivity (H > Hc).

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