Новые публикации

A 10 GHz Monolithic Filter Based on Stripline Resonators with a Split Conductor

Govorun, I.V., Belyaev, B.A., Zav’yalov, Y.B., (...), Ugryumov, A.V., Galeev, R.G.// Doklady Physics//

https://doi.org/10.1134/S1028335823120030

The monolithic design of a compact bandpass filter X-band is made on the technology of multilayered printed circuit boards. Quarter-wave stripline resonators of the filter have two conductors divided by a layer of prepreg having low parameters that bond together the design. This eliminates the influence of the prepreg on the characteristics of the devices, ensuring good repeatability of filters in mass production. To increase the high-frequency stopband of the filter, one of the conductors of each resonator is cut in half by a transverse slit. The constructive sizes of the device were obtained by parametric synthesis using the electrodynamic analysis of its 3D model. The experimental data of the five-order filter are in good agreement with the electromagnetic simulation of filter of the 3D model. The experimental device has a central frequency of the passband of 10 GHz and a fractional bandwidth of 5.7%, and its dimensions and weight are 18.0 × 5.4 × 2.1 mm3 and 0.5 g. The important advantage of the developed design is the possibility of its installation on the board using the surface mounting method.

Revolutionizing physics: a comprehensive survey of machine learning applications

Suresh, R., Bishnoi, H., Kuklin, A.V., (...), Gharat, S., Hiba, P.// Frontiers in Physics//

https://doi.org/10.3389/fphy.2024.1322162

In the context of the 21st century and the fourth industrial revolution, the substantial proliferation of data has established it as a valuable resource, fostering enhanced computational capabilities across scientific disciplines, including physics. The integration of Machine Learning stands as a prominent solution to unravel the intricacies inherent to scientific data. While diverse machine learning algorithms find utility in various branches of physics, there exists a need for a systematic framework for the application of Machine Learning to the field. This review offers a comprehensive exploration of the fundamental principles and algorithms of Machine Learning, with a focus on their implementation within distinct domains of physics. The review delves into the contemporary trends of Machine Learning application in condensed matter physics, biophysics, astrophysics, material science, and addresses emerging challenges. The potential for Machine Learning to revolutionize the comprehension of intricate physical phenomena is underscored. Nevertheless, persisting challenges in the form of more efficient and precise algorithm development are acknowledged within this review.

Intense charge transfer plasmons in golden nanoparticle dimers connected by conductive molecular linkers

Fedorov, A.S., Visotin, M.A., Lukyanenko, A.V., Gerasimov, V.S., Aleksandrovsky, A.S.// Journal of Chemical Physics//

https://doi.org/10.1063/5.0183334

Golden nanoparticle dimers connected by conjugated molecular linkers 1,2-bis(2-pyridyl)ethylene are produced. The formation of stable dimers with 22 nm diameter nanoparticles is confirmed by transmission electron microphotography. The possibility of charge transfer through the linkers between the particles in the dimers is shown by the density functional theory calculations. In addition to localized plasmon resonance of solitary nanoparticles with a wavelength of 530 nm, the optical spectra exhibit a new intense absorption peak in the near-infrared range with a wavelength of ∼780 nm. The emergent absorption peak is attributed to the charge-transfer plasmon (CTP) mode; the spectra simulated within the CTP developed model agree with the experimental ones. This resonant absorption may be of interest to biomedical applications due to its position in the so-called transmission window of biological tissues. The in vitro heating of CTP dimer solution by a laser diode with a wavelength of 792 nm proved the efficiency of CTP dimers for achieving a temperature increase of ΔT = 6 °C, which is sufficient for hyperthermia treatment of malignant tumors. This indicates the possibility of using hyperthermia to treat malignant tumors using the material we synthesized.

Quantum SU(3)-ferrimagnet on triangular lattice

Martynov, A.S., Dzebisashvili, D.M.// Journal of Magnetism and Magnetic Materials//

https://doi.org/10.1016/j.jmmm.2024.171906

Manifestations of quantum effects in the macroscopic properties of frustrated magnets keep attracting considerable interest. We have formulated and studied a simple model of a three-sublattice mixed-spin (�=1,1/2,1/2��(3)-ferrimagnet on triangular lattice in which the strong quantum fluctuations are developed due to combined effect of frustrated exchange bonds, reduced dimensionality and a single-ion easy-plane anisotropy in the spin-1 sublattice. To account correctly for the ��(3) algebra, the Hubbard operators representation of generators is used. Dependencies of the magnetic moments  and �� (for spin-1/2 and spin-1 sublattices respectively), the total magnetic moment , as well as the quadrupole moment, on the anisotropy parameter  are calculated at zero temperature and different ratios �/� of exchange integrals from different sublattices. It is established that for �/�≪1 the critical value ��, at which the system enters the quadrupole antiferromagnetic phase, can be much smaller than both  and . Besides, with an increase in  from zero to �� the total moment  can change its direction several times via taking zero value. Classification of four branches of the spin-wave excitation spectrum of the ��(3)-ferrimagnet is carried out and modification of the spectrum with change in the single-ion anisotropy is analyzed.

Synthesis and properties of the NdSF compound, phase diagram of the NdF3–Nd2S3 system

Grigorchenko, V.M., Molokeev, M.S., Oreshonkov, A.S., (...), Elyshev, A.V., Andreev, O.V.// Journal of Solid State Chemistry//

https://doi.org/10.1016/j.jssc.2024.124640

The NdF3–Nd2S3 system attracts attention of researchers due to the possibility of using LnSF compounds (Ln = rare earth element) as possible new p- and n-type materials. The samples of this system were synthesized from NdF3 and Nd2S3. The NdSF compound belongs to the PbFCl structural type, P4/nmm space group, unit cell parameters: a = 3.9331(20) Å, c = 6.9081(38) Å. The experimentally determined direct and indirect NdSF bandgaps are equal to 2.68 eV and 2.24 eV. The electronic band structure was calculated via DFT simulation. The NdSF compound melts congruently at T = 1385 ± 10°С, ΔНm = 40.5 ± 10 kJ/mol, ΔS = 24.4 ± 10 J/mol. The NdSF microhardness is 455 ± 10 HV. Five phase transformations in the NdF3–Nd2S3 system were recorded by DSC; their balance equations were derived. The liquidus of the system calculated from the Redlich–Kister equation is fully consistent with the DSC data.

Highly-Efficiency Far-Red Emission in Cr3+ Activated Ca1.8Mg1.2Al2Ge3O12 toward Plant Precise Lighting

Yang, C., Zheng, D., Zou, X., (...), Liu, Y., Lei, B.// Advanced Optical Materials//

 https://doi.org/10.1002/adom.202303235

Far-red (FR) region (beyond 700 nm) lighting sources possess special potential for plant lighting. However, it remains a challenge to obtain high-performance Cr3+-doped FR phosphors. This study developed a FR phosphor, Ca1.8Mg1.2Al2Ge3O12:Cr3+ (CMAGG: Cr3+), using the cation substitution strategy. Under 438 nm blue light excitation, the phosphors display FR emission centered at 720 nm with a full width at half maximum (FWHM) of 91 nm. Benefit from the favorable match with the FR phytochrome (Pfr), the phosphor is combined with InGaN blue light chips to create a FR phosphor-converted light-emitting diode (pc-LED), which is used in Italian lettuce growth experiments and it results shown in a 15% increase in fresh weight and a 6.5% increase in dry weight. Notably, supplemental FR light modulated its growth morphology. The results of this study will be useful for further research on novel Cr3+-doped FR phosphors to meet the precise spectral requirements for plant growth.

Characterizing Aptamer Interaction with the Oncolytic Virus VV-GMCSF-Lact

Dymova, M.A., Malysheva, D.O., Popova, V.K., (...), Richter, V.A., Kuligina, E.V.// Molecules//

https://doi.org/10.3390/molecules29040848

Aptamers are currently being investigated for their potential to improve virotherapy. They offer several advantages, including the ability to prevent the aggregation of viral particles, enhance target specificity, and protect against the neutralizing effects of antibodies. The purpose of this study was to comprehensively investigate an aptamer capable of enhancing virotherapy. This involved characterizing the previously selected aptamer for vaccinia virus (VACV), evaluating the aggregation and molecular interaction of the optimized aptamers with the recombinant oncolytic virus VV-GMCSF-Lact, and estimating their immunoshielding properties in the presence of human blood serum. We chose one optimized aptamer, NV14t_56, with the highest affinity to the virus from the pool of several truncated aptamers and built its 3D model. The NV14t_56 remained stable in human blood serum for 1 h and bound to VV-GMCSF-Lact in the micromolar range (Kd ≈ 0.35 μM). Based on dynamic light scattering data, it has been demonstrated that aptamers surround viral particles and inhibit aggregate formation. In the presence of serum, the hydrodynamic diameter (by intensity) of the aptamer–virus complex did not change. Microscale thermophoresis (MST) experiments showed that NV14t_56 binds with virus (EC50 = 1.487 × 109 PFU/mL). The analysis of the amplitudes of MST curves reveals that the components of the serum bind to the aptamer–virus complex without disrupting it. In vitro experiments demonstrated the efficacy of VV-GMCSF-Lact in conjunction with the aptamer when exposed to human blood serum in the absence of neutralizing antibodies (Nabs). Thus, NV14t_56 has the ability to inhibit virus aggregation, allowing VV-GMCSF-Lact to maintain its effectiveness throughout the storage period and subsequent use. When employing aptamers as protective agents for oncolytic viruses, the presence of neutralizing antibodies should be taken into account.

Spontaneous imbibition experiments for enhanced oil recovery with silica nanosols

Pryazhnikov, M.I., Zhigarev, V.A., Minakov, A.V., Nemtsev, I.V.// Capillarity//

https://doi.org/10.46690/capi.2024.03.02

Experimental oil displacement as a result of spontaneous imbibition of silica nanosols has been carried out using two types of sandstone as the reservoir rock. The permeability of the cores ranged from 0.34 to 333 mD, while the porosity was 11% and 22%, respectively. During the research, the influence of the concentration and nanoparticle size, as well as the permeability of the rock, on the process of spontaneous imbibition, was studied. Silica nanosols were considered as an object of study. The nanoparticle size ranged from 10 to 35 nm. The mass concentration of nanoparticles varied from 0.01% to 0.25%. It was found that the use of silica nanosols significantly increases the rate of the spontaneous imbibition process. It was established that a silica nanosol with a nanoparticle size of 10 nm and a concentration of 0.25% allows to displace more than six times oil compared to the reservoir water model in the same time. As a result, it was shown that the oil displacement efficiency and the efficiency of spontaneous imbibition increase along with an increase in the nanoparticle concentration and a decrease in the nanoparticle size.

Corrigendum to “Properties of degradable polyhydroxyalkanoates with different monomer compositions”

Volova, T., Kiselev, E., Nemtsev, I., (...), Ryltseva, G., Shishatskaya, E.// International Journal of Biological Macromolecules//

On the use of dual-polarized multi-angular observations of P-band brightness temperature for soil moisture profile retrieval in thawed mineral soil

Muzalevskiy, K.V., Walker, J.P., Brakhasi, F., (...), Wu, X., Shen, X.// International Journal of Remote Sensing//

https://doi.org/10.1080/01431161.2024.2313993

This article investigated the possibility of remotely sensing the soil moisture profile in thawed soil from multi-angular dual-polarized brightness temperature (TB) observations at P-band frequencies of 750 MHz and 409 MHz using a modified Burke model. Moreover, it was found that an excellent agreement (coefficient of determination R2 = 0.999 and root-mean-square error (RMSE) no more than RMSE = 0.6 K) could be achieved between the Njoku coherent brightness temperature model and the modified Burke model by introducing a reflectivity from the air-soil interface that takes into account the phases of the multiple re-reflected waves in the underlying layers. Based on the modified Burke model, the depths from which apparent moisture and temperature could be retrieved in a dielectrically-inhomogeneous, non-isothermal soil were investigated, being approximately ten times less than the depth for which apparent soil temperature could be retrieved. In general, the thickness of the emitting layer depends on the TB look angle and polarization, along with the moisture and temperature profiles of the soil. It was also shown that due to the effect of the Brewster angle, the H-polarization of TB was twice as sensitive (4 K/1%) to changes in volumetric soil moisture than V-polarization (1.9 K/1%). Based on multi-angular (10°-50°) observations of TB at H- and V-polarizations, a method of moisture profile retrieval in the top 5–15 cm soil (depending on surface moisture) was proposed using an exponential fitting function, the parameters of which are found in the course of solving the inverse problem. A decrease in the sensing frequency from 750 MHz to 409 MHz makes it possible to increase the accuracy of soil moisture profiles retrieval by a factor of two, being from RMSE = 1.6% (R2 = 0.946) to RMSE = 0.85% (R2 = 0.982) in the top 15 cm layer of soil. The conducted investigation shows the promise of using P-band observations of TB for soil moisture profile retrieval.

Magnetic structure and pressure-induced spin-crossover in Me3B2O6 (Me = Mn, Fe, Co, Ni) kotoites: Representation analysis and DFT calculations

Zhandun, V.S., Draganyuk, O.N., Zamkova, N.G.// Computational Materials Science//

https://doi.org/10.1016/j.commatsci.2024.112859

The magnetic and electronic properties of transition metal borates Me3B2O6 (Me = Mn, Fe, Co, Ni) with kotoite structure have been investigated at ambient and high pressures via a combination of representation analysis and density functional theory (DFT + U) calculations. Several magnetic configurations corresponding to the different irreducible representations have been considered. The total-energy calculations reveal that the magnetic ground state of Me3B2O6 kotoites is composition-dependent. The lowest energy magnetic phase of manganese and nickel kotoites is characterized by the antiferromagnetic ordering of the transition metal magnetic moments along the c- axis and along the b-axis for cobalt and iron kotoites. The magnetic cell of Ni3B2O6 kotoite corresponds to k = (1/2, 0, 1/2) vector and four time larger than the unit cell. The calculated exchange constants indicate the competition between ferromagnetic and antiferromagnetic interactions. At a critical pressure, Me ions undergo a high-spin to low-spin state crossover. This magnetic moments collapse is analyzed in terms of change in electronic structure under pressure.

Magnetic anisotropy and ferromagnetic resonance in inhomogeneous demagnetizing fields near edges of thin magnetic films

Solovev, P.N., Belyaev, B.A., Boev, N.M., Skomorokhov, G.V., Izotov, A.V.// Journal of Physics Condensed Matter//

DOI 10.1088/1361-648X/ad258c

Using local ferromagnetic resonance spectroscopy, we have studied the magnetic properties near edges of thin tangentially magnetized permalloy films, in which a well-defined uniaxial magnetic anisotropy was induced perpendicular to one of the edges. In the experiment, two samples with thicknesses of 90 and 300 nm and with slightly different compositions were examined. To explain the magnetization dynamics near edges, we propose a simple yet effective model of a film in the form of a rectangular prism, which yields the modified Kittel formula for the resonance frequency. In this formula, the locally averaged distance-dependent demagnetizing field that emerges near the edges is included as an additional uniaxial anisotropy term. The measurements reveal that at a certain distance from the edge, the resulting (apparent) anisotropy, determined from the angular dependencies of the resonance field, almost vanishes. Moreover, its easy axis reorients to become parallel to the edge. The model predictions agree well with these results, proving that the main resonance mode behavior near the film edges can be accurately described by introducing additional effective uniaxial anisotropy, provided the measuring area is relatively large. However, for the thick (300 nm) sample, additional precession modes are also observed. These modes distort the angular dependence of the main mode, thus demonstrating the limitations of the model.

Application of DUT-4 MOF structure switching for optical and electrical humidity sensing

Krylov, Alexander S; Shipilovskikh, Sergei A; Krylova, Svetlana N; Slyusarenko, Nina V; Timofeeva, Maria; Kenzhebayeva, Yuliya A; Bachinin, Semyon V; Yushina, Irina D; Cherepakhin, Aleksandr V; Shestakov, Nikolai P; et al// Dalton transactions //

DOI: https://doi.org/10.1039/D4DT00038B

The threshold structural transformation of the DUT-4 metal–organic framework (MOF) from an ordered to distorted phase during exposure to ambient conditions has been revealed. The in situ X-ray diffraction analysis, in situ Raman and FTIR spectroscopy, scanning electron microscopy and synchronous thermal analysis have been used for investigation. The reversible effect of exposure time and humidity on such a phase transition has been confirmed. We also demonstrated that the observed phase transition correlated well with changes in the optical and electronic properties of DUT-4, paving the way to a new family of MOF-based phase change materials for optoelectronic applications.

 

Two-Dimensional Hybrid Perovskite with High-Sensitivity Optical Thermometry Sensors

Guan, Mengyu; Hao, Jiarui; Qiu, Lei; Molokeev, Maxim S; Ning, Lixin; Dai, Zhigao; Li, Guogang// Inorganic chemistry//

https://doi.org/10.1021/acs.inorgchem.3c04140

Optical thermometry has gained significant attention due to its remarkable sensitivity and noninvasive, rapid response to temperature changes. However, achieving both high absolute and relative temperature sensitivity in two-dimensional perovskites presents a substantial challenge. Here, we propose a novel approach to address this issue by designing and synthesizing a new narrow-band blue light-emitting two-dimensional perovskite named (C8H12NO2)2PbBr4 using a straightforward solution-based method. Under excitation of near-ultraviolet light, (C8H12NO2)2PbBr4 shows an ultranarrow emission band with the full width at half-maximum (FWHM) of only 19 nm. Furthermore, its luminescence property can be efficiently tuned by incorporating energy transfer from host excitons to Mn2+. This energy transfer leads to dual emission, encompassing both blue and orange emissions, with an impressive energy transfer efficiency of 38.3%. Additionally, we investigated the temperature-dependent fluorescence intensity ratio between blue emission of (C8H12NO2)2PbBr4 and orange emission of Mn2+. Remarkably, (C8H12NO2)2PbBr4:Mn2+ exhibited maximum absolute sensitivity and relative sensitivity values of 0.055 K–1 and 3.207% K–1, respectively, within the temperature range of 80–360 K. This work highlights the potential of (C8H12NO2)2PbBr4:Mn2+ as a promising candidate for optical thermometry sensor application. Moreover, our findings provide valuable insights into the design of narrow-band blue light-emitting perovskites, enabling the achievement of single-component dual emission in optical thermometry sensors.

Theoretical Insights into the Mechanical Properties of DUT-8(Ni) MOF in the Open and Closed Pore Phases

Yushina, I.D., Matveychuk, Y.V., Krylov, A.S.// Crystal Growth and Design//

https://doi.org/10.1021/acs.cgd.3c01154

nsights into the mechanical properties of DUT-8(Ni) MOF crystals capable of structural phase transitions are presented. The open and closed pore phases of DUT-8(Ni) are drastically different in their mechanical behavior. For the open-pore phase, a huge anisotropy of compressibility and shear modulus is observed, caused by the presence of two orthogonal motives formed by aromatic linkers bound with Ni atoms via Ni–O bonds. The possibility of easy shifting of linkers with breaking and formation of new Ni–O and Ni–N bonds at the application of shear stress, which is at the same time more stable at uniaxial stress, is shown on the basis of the stiffness tensor analysis. This fact assumes the flexibility of the open-pore phase crystals and their ability for structural transformation. The less prominent anisotropy of elastic moduli and the increased values of these moduli for the closed-pore phase crystals indicate the predominantly hardness and absence of flexibility of this phase.

Highly efficient and thermostable far-red phosphor for promoting root growth in plants

Ouyang, S., Yin, J., Su, L., (...), Zhang, S., Xia, M.// Journal of Materials Chemistry C//

DOI https://doi.org/10.1039/D3TC02823B

Phytochrome PFR plays a key role in plant photomorphogenesis, and its perception of far-red light is essential, but how to obtain an efficient far-red phosphor to achieve accurate light filling remains a huge challenge. In this study, Gd1−yzAl3−x(BO3)4:xCr3+,yLu3+,zSm3+ (GAB:xCr3+,yLu3+,zSm3+) series phosphors were synthesized by a high-temperature solid-state method. By doping Lu3+, the emission intensity of Cr3+ could increase as high as 20%. With the introduction of Sm3+, the emission intensity of Cr3+ was further increased by 29%. Particularly, the emission spectra can be tuned by varying the concentration ratio of Sm3+ and Cr3+, more suitable for the absorption spectrum of PFR. Moreover, the internal quantum yield and external quantum yield of GL0.1AB:0.03Cr3+ and GL0.1AB:0.03Cr3+,0.003Sm3+ were 83.1% and 24.7% and 78.1% and 26.3%, respectively. There were high anti-thermal quenching properties in the prepared phosphors at 423 K, with 107.6% (GAB:0.03Cr3+), 103.1% (GL0.1AB:0.03Cr3+), and 102.7% (GL0.1AB:0.003Sm3+,0.03Cr3+). Finally, the phosphors were made into pc-LED devices, which can realize the adjustable orange-red and far-red luminescence and meet the needs of plant lighting applications. In the light-regulated plant growth experiment, compared with the control group, far-red light promoted root growth in plants, confirming the application potential of the prepared phosphors in indoor plant cultivation.

Superconducting Order Parameter Structure in the Nematic Phase of Iron-based Materials

Korshunov, M.M., Togushova, Y.N.// JETP Letters//

https://doi.org/10.1134/S0021364024600046

We consider the effect of the nematic order on the formation of the superconducting state in iron pnictides and chalcogenides. Nematic order with the B2g symmetry is modelled as the d-type Pomeranchuk instability and treated within the mean-field approach. Calculated nematic order parameter depends on the nematic interaction coefficient and abruptly changes with the coefficient’s increase. The superconducting solution is obtained within the spin-fluctuation pairing theory. We show that the leading solution in the nematic phase has a sπ± structure. From the critical temperature Tc estimations, we conclude that the nematic superconducting state of the sπ± type is more favorable than the usual s± and ��2−�2 type states appearing in the absence of the nematicity

MODULATION OF LIGHT TRANSMISSION IN SELF-ORGANIZED ENSEMBLES OF NEMATIC DOMAINS

Parshin, A.M.// Zhidkie Kristally i Ikh Prakticheskoe Ispol'zovanie

Zhidkie Kristally i Ikh Prakticheskoe Ispol'zovanie, 23(4), pp. 49-57.

 

Preparation and Properties of Magnetic Composites γ-Fe2O3/SiO2/Aptamer(FAS9) for Magnetic Resonance Hyperthermia

Stolyar, S.V., Li, O.A., Nikolaeva, E.D., (...), Volochaev, M.N., Mokhov, A.A.// Physics of Metals and Metallography//

https://doi.org/10.1134/S0031918X23601439

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.

 

Auger Electron Spectroscopy of Thin Cr2GeC Films

Andryushchenko, T.A., Lyaschenko, S.A., Varnakov, S.N., (...), Maximova, O.A., Ovchinnikov, S.G.// Physics of Metals and Metallography//

https://doi.org/10.1134/S0031918X2360135X

Auger electron spectroscopy was used to determine the phase composition of Cr2GeC MAX phase thin films. A distinctive feature of the formation of carbon-containing MAX phases is the shape of carbon Auger peaks, which is characteristic of metal carbides spectra. Features of the Auger spectra in the presence of secondary phases of chromium germanides are found. Their presence can manifest itself in an increase in the energy of the germanium peaks, which is caused by a chemical shift during the formation of the Cr–Ge bond. Moreover, we have detected the accumulation of electronic charge, which can be explained by the features of the surface morphology.

Magneto-Optical Ellipsometry of Thin Films with Optical Uniaxial Anisotropy

Maximova, O.A., Lyaschenko, S.A., Varnakov, S.N., (...), Shevtsov, D.V., Andryushchenko, T.A.// Physics of Metals and Metallography//

https://doi.org/10.1134/S0031918X23601385

In this paper, we solve the inverse problem of magneto-optical ellipsometry for thin ferromagnetic films with optical uniaxial anisotropy. We work within the framework of the approach we developed earlier analyzing magnetoellipsometric data without using fourth-order M-matrices. We work with ellipsometric relations, in which we take into account the magneto-optical contribution as perturbations, and ellipsometric measurements are carried out on a setup with a simple dipole scheme based on the transverse magneto-optical Kerr effect. We add the magneto-optical response to the expressions known in the literature for the reflection coefficients of anisotropic thin films, which are related to the parameters measured by magneto-optical ellipsometry. As a result, by analyzing the obtained expressions for the reflection coefficients, we obtain information on the total permittivity tensor of a thin film.

 

Dielectric Model of the Upper Organic Layer of Forest Soils for a Frequency of 435 MHz

Karavaiskii, A.Y., Lukin, Y.I.// Izvestiya - Atmospheric and Ocean Physics//

https://doi.org/10.31857/S0205961423020021

Создана диэлектрическая модель, основанная на рефракционной диэлектрической модели смеси талых и мерзлых лесных органических почв корневой зоны для частоты 435 МГц. Модель разработана на основе диэлектрических измерений четырех почв, в которых содержание органического вещества варьировалось от 15 до 31%. Диэлектрические измерения были проведены в диапазоне массовой влажности от 0 до 0.6 г/г и диапазоне температур от –30 до 25°С. Коэффициент детерминации (R2) между рассчитанными с использованием модели и измеренными значениями действительной (ε') и мнимой (ε") частями комплексной диэлектрической проницаемости составил 0.97. Нормированное среднеквадратическое отклонение составило 16 и 21% для действительной и мнимой частей комплексной диэлектрической проницаемости соответственно. Разработанная диэлектрическая модель может быть применена в алгоритмах дистанционного зондирования при восстановлении значения влажности лесных почв корневой зоны из данных радарного и радиометрического зондирования.

Hidden magnetic instability in the substituted multiferroics (Nd,Tb)Fe3(BO3)4

Golosovsky, I.V., Mukhin, A.A., Skumryev, V., (...), Ivanov, V.Y., Gudim, I.A.// Physical Review B//

https://doi.org/10.1103/PhysRevB.109.014421

In the substituted Nd1xTbxFe3(BO3)4 (x=0.1 and x=0.2), possessing almost easy-axis magnetic structure at low temperatures, an unusual two-step transition in fields along the trigonal c axis was observed by magnetization and single-crystal neutron diffraction studies. At the first step, only part of the Tb Ising-type moments flip to the c axis, which is accompanied by a significant deviation of the antiferromagnetic Fe spins from the c axis. At the second step, the remaining Tb moments flip and the Fe moments flop into the basal plane. The ob- served evolution is qualitatively explained by a model assuming small deviations of Tb moments from the trigonal axis due to local environment distortions, which leads to nonequivalence of the Tb ions with respect to effective Tb-Fe exchange and external field. Thus, an intrinsic “hidden” instability of the magnetic system in the magnetic field occurs.

Application of DUT-4 MOF structure switching for optical and electrical humidity sensing

Krylov, A.S., Shipilovskikh, S.A., Krylova, S.N., (...), Vtyurin, A.N., Milichko, V.A.// Dalton Transactions//

DOI https://doi.org/10.1039/D4DT00038B

The threshold structural transformation of the DUT-4 metal–organic framework (MOF) from an ordered to distorted phase during exposure to ambient conditions has been revealed. The in situ X-ray diffraction analysis, in situ Raman and FTIR spectroscopy, scanning electron microscopy and synchronous thermal analysis have been used for investigation. The reversible effect of exposure time and humidity on such a phase transition has been confirmed. We also demonstrated that the observed phase transition correlated well with changes in the optical and electronic properties of DUT-4, paving the way to a new family of MOF-based phase change materials for optoelectronic applications.

Separating the contributions of the magnetic subsystems in antiferromagnetic ferrihydrite nanoparticles by analyzing the magnetization in fields of up to 250 kOe

Krasikov, A.A., Balaev, D.A., Balaev, A.D., (...), Yaroslavtsev, R.N., Iskhakov, R.S.// Journal of Magnetism and Magnetic Materials//

https://doi.org/10.1016/j.jmmm.2024.171781

Contributions of different magnetic subsystems formed in the systems of synthetic ferrihydrite nanoparticles (characterized previously) with an average size of < d> ≈ 2.7 nm coated with polysaccharide arabinogalactan in different degrees have been separated by measuring the dependences of their magnetization M on magnetic field H of up to 250 kOe on vibrating sample and pulsed magnetometers. The use of a wide measuring magnetic field range has been dictated by the ambiguity in identifying a linear M(H) portion for such antiferromagnetic nanoparticle systems within the conventional field range of 60–90 kOe. The thorough analysis of the magnetization curves in the temperature range of 100–250 K has allowed the verification of the contributions of (i) uncompensated magnetic moments µun in the superparamagnetic subsystem, (ii) the subsystem of surface spins with the paramagnetic behavior, and (iii) the antiferromagnetic susceptibility of the antiferromagnetically ordered ferrihydrite particle core. As a result, a model of the magnetic state of ferrihydrite nanoparticles has been proposed and the numbers of spins corresponding to magnetic subsystems (i)–(iii) have been estimated. An average magnetic moment μun of ∼ 145 μB (μB is the Bohr magneton) per particle corresponds approximately to 30 decompensated spins of iron atoms in a particle (about 3 % of all iron atoms), which, according to the Néel’s hypothesis μun ∼ <d>3/2, are localized both on the surface and in the bulk of an antiferromagnetically ordered particle. The fraction of free (paramagnetic) spins is minimal in the sample without arabinogalactan coating of the nanoparticle surface (7 %) and is attained 20 % of all iron atoms in the sample with the highest degree of spatial separation of particles. According to this estimation, paramagnetic spins are located mainly on the edges and protruding areas of particles. Most magnetic moments of iron atoms are ordered antiferromagnetically and the corresponding magnetic susceptibility of this subsystem behaves as in an antiferromagnet with the randomly distributed crystallographic axes, i.e., increases with temperature.

Chemical pressure as an effective tool for tuning the structural disordering and barocaloric efficiency of complex fluorides (NH4)3MF7 (M: Sn, Ti, Ge, Si)

Flerov, I.N., Gorev, M.V., Bogdanov, E.V., Laptash, N.M.// Journal of Physics D: Applied Physics//

https://iopscience.iop.org/article/10.1088/1361-6463/ad211b

Double fluoride salts (NH4)3M4+F7 (M4+: Sn, Ti, Ge, Si) demonstrate a high efficiency of using chemical pressure as a tool for control and tuning structural ordering/disordering, sensitivity to hydrostatic pressure, successions of the phase transitions, etc and, as a result, for purposeful variation within a wide range of parameters of barocaloric effect (BCE). The conventional and inverse BCEs near the triple points were found on the T − p phase diagrams, combination of which can be used to construct original cooling cycle in narrow temperature and pressure ranges. Reconstructive transformation between two cubic phases, $Pm\bar{3}m \leftrightarrow Pa\bar{3}$, realized in (NH4)3SnF7 at atmospheric pressure and in (NH4)3TiF7 at $p\gt$ 0.4 GPa are characterized by rather low thermal hysteresis, $\delta T_0$ = 1 K, and a great entropy change, $\Delta S_\textrm{BCE}$ = 110–152 J (kg · K)−1, depending on the size of the central atom. At above 300–350 K, a contribution to BCE associated with the regular thermal expansion of the crystal lattice becomes comparable to entropy and temperature changes under pressure in the region of the phase transitions. An analysis of the absolute, relative and integral barocaloric characteristics of (NH4)3M4+F7 compounds showed their high competitiveness with respect to other barocaloric materials considered as promising solid-state refrigerants.

Signatures of quantum chaos and fermionization in the incoherent transport of bosonic carriers in the Bose-Hubbard chain

Muraev, P. S.; Maksimov, D. N.; Kolovsky, A. R.// arXiv.org, e-Print Archive, Quantum Physics//

https://doi.org/10.48550/arXiv.2307.07208

We analyse the stationary current of Bose particles across the Bose-Hubbard chain connected to a battery, focusing on the effect of inter-particle interactions. It is shown that the current magnitude drastically decreases as the strength of inter-particle interactions exceeds the critical value which marks the transition to quantum chaos in the Bose-Hubbard Hamiltonian. We found that this transition is well reflected in the non-equilibrium many-body density matrix of the system. Namely, the level-spacing distribution for eigenvalues of the density matrix changes from Poisson to Wigner-Dyson distributions. With the further increase of the interaction strength, the Wigner-Dyson spectrum statistics changes back to the Poisson statistics which now marks fermionization of the bosonic particles. With respect to the stationary current, this leads to the counter-intuitive dependence of the current magnitude on the particle number.

A hybrid quantum-classical theory for predicting terahertz charge-transfer plasmons in metal nanoparticles on graphene

Fedorov, A S; Eremkin, E V; Krasnov, P O; Gerasimov, V S; Ågren, H; Polyutov, S P// Journal of chemical physics//

https://doi.org/10.1063/5.0178247

Metal nanoparticle (NP) complexes lying on a single-layer graphene surface are studied with a developed original hybrid quantum–classical theory using the Finite Element Method (FEM) that is computationally cheap. Our theory is based on the motivated assumption that the carrier charge density in the doped graphene does not vary significantly during the plasmon oscillations. Charge transfer plasmon (CTP) frequencies, eigenvectors, quality factors, energy loss in the NPs and in graphene, and the absorption power are aspects that are theoretically studied and numerically calculated. It is shown the CTP frequencies reside in the terahertz range and can be represented as a product of two factors: the Fermi level of graphene and the geometry of the NP complex. The energy losses in the NPs are predicted to be inversely dependent on the radius R of the nanoparticle, while the loss in graphene is proportional to R and the interparticle distance. The CTP quality factors are predicted to be in the range ∼10−100⁠. The absorption power under CTP excitation is proportional to the scalar product of the CTP dipole moment and the external electromagnetic field. The developed theory makes it possible to simulate different properties of CTPs 3–4 orders of magnitude faster compared to the original FEM or the finite-difference time domain method, providing possibilities for predicting the plasmonic properties of very large systems for different applications.

Elucidating elusive quaternary selenide EuCeCuSe3: Synthesis, crystal structure, properties and theoretical studies

Maxim V. Grigoriev a, Anna V. Ruseikina a, Maxim S. Molokeev a b c, Vladimir А. Chernyshev d, Aleksandr S. Aleksandrovsky b e, Alexander S. Krylov b, Svetlana N. Krylova b, Nikolai P. Shestakov b, Dmitriy А. Velikanov c, Alexander A. Garmonov f, Alexey V. Matigorov a, Evgeny A. Ostapchuk a, Thomas Schleid g, Damir A. Safin// Journal Of Rare Earths//

https://doi.org/10.1016/j.jre.2022.11.004

We report on the novel heterometallic quaternary selenide EuCeCuSe3, the fabrication of which has been a challenge until this work. The structure of the reported selenide was elucidated from the powder X-ray diffraction data, which revealed the formation of EuCeCuSe3 with excellent yield (96.7%) accompanied with a minor fraction of CeSe2 (3.3%), and was best solved in orthorhombic space group Pnma with the BaLaCuS3 structural type. Thus, the crystal structure of the title compound completes the row of the heterometallic quaternary selenides EuRECuSe3 (RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y), of which the cerium-based derivative exclusively belongs to the BaLaCuS3 structural type. The distortion of the CuSe4 polyhedron was compared for the whole series of EuRECuSe3 compounds using the τ4-descriptor for four coordinated ions, which revealed the highest degree of distortion for the Ce3+-containing selenide, followed by the La3+-based derivative. Furthermore, the crystallographic and geometrical parameters of the reported selenide were discussed in comparison to the Ce3+-based sulfides SrCeCuS3 and EuCeCuS3Ab initio calculations of the crystal structure, a phonon spectrum and elastic constants for the crystal of EuСeCuSe3 were also performed. The types and wavenumbers of fundamental modes were determined and the involvement of ions participating in the phonon modes was assessed. The experimental IR spectrum of the reported selenide was interpreted and found to be in agreement with the calculated spectrum. The experimental direct band gap of EuCeCuSe3 was measured to be 1.36 eV that is consistent with the concept of its origin due to interband transitions between orbitals emerging mainly from 4f (valence band) and 5d (conduction band) levels of the Eu2+ cation. The dependence of the Young's modulus on the direction demonstrates the anisotropy of the elastic properties, while the Vickers hardness for EuCeCuSe3 was calculated to be 5.2 GPa. Finally, the title compound is paramagnetic above 4 K.

Magnetic Interparticle Interactions and Superparamagnetic Blocking of Powder Systems of Biogenic Ferrihydrite Nanoparticles

A. A. Krasikov, Yu. V. Knyazev, D. A. Balaev, S. V. Stolyar, V. P. Ladygina, A. D. Balaev & R. S. Iskhakov // Journal of Experimental and Theoretical Physics//

https://doi.org/10.1134/S1063776123120075

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.

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