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The specific luminescence behavior of crystalline oxide particles doped with rare earth ions strongly depends on the initial composition of the host material and synthesis conditions. This issue is especially significant for non-isovalent doping in the crystal lattice. In this case, the formation of the structure is accompanied by the formation of point defects serving as charge compensators. The work is devoted to the synthesis of CaWO4:Nd3+ particles in the salt melt (modified Pechini method) and the study of structural and luminescent properties under varying synthesis conditions. It was found that temperature and duration of heat treatment in the salt melt (KCl) affected the crystal structure, the size of coherent scattering regions, luminescence intensity, and lifetime. An increase of heat treatment temperature led to a reduction of luminescence intensity and lifetime due to the formation of point defects. The optimal synthesis conditions for obtaining the highest luminescence intensity of CaWO4:Nd3+ crystalline particles in salt melt were found to be the following Т1= 600 °C; t1=2 h (the stage of polymer gel thermal treatment), Т2= 800 °C; t2=1 h (the stage of thermal treatment in KCl salt melt). As-synthesized CaWO4:Nd3+ powders contain both coarse and fine fractions. However weak particle agglomeration allowed obtaining a water dispersion with individual nanoparticles (up to 200 nm) after ultrasonic treatment. According to the obtained results, the synthesized material is characterized by high luminescence intensity and high dispersion, and promising as fluorescent thermometers and biological labels.

The closest environment of Al3+ cations was analyzed in detail in solutions of aluminum nitrate in the prototypical protic ionic liquid ethyl ammonium nitrate (EAN) using 1 H and 14 N nuclear magnetic resonance (NMR) spectra. For Al (NO3 )3 -EAN mixtures with different water content, a quantitative analysis of the integral intensities of the 1 H and 14 N signals was carried out and the composition of the first solvation shell of the aluminum cation was refined.

The dielectric and magnetic properties of ceramics based on barium titanate and solid solutions of barium strontium titanate doped with iron and gadolinium ions at concentrations below 5 mol.% have...

The magnetic and magnetotransport properties of thin Heusler alloy Ni49.7Fe17.4Co4.2Ga28.7 films deposited onto MgO(100) substrates are studied over a wide temperature range, which includes a martensitic transition (MT). For this composition, the MT is not accompanied by a magnetic phase transition, since the martensitic and austenitic phases are ferromagnets with similar magnetizations. The electrical resistivity does not undergo sharp changes during the MT. The magnetoresistance is negative, decreases in magnitude with increasing temperature in the range 100–250 K corresponding to the MT, and then increases to –1%. The field dependences of the Hall effect resistivity have the shape that is characteristic of homogeneous ferromagnetic alloys. The coefficients of the normal and anomalous Hall effects are determined. The anomalous Hall effect coefficient is shown to be described by the relation Rs = αρ + βρ2, where ρ is the electrical resistivity and the second term is lower than the first, which indicates an important role of the interference impurity–phonon scattering mechanism.

Contactless optical thermometry is successfully applied for accurate local temperature sensing in many scientific and technological areas. The majority of optical thermometers utilize a ratiometric...

Biopolymer sodium alginate (SA) is actively used as a green membrane material. To improve the pervaporation properties of the SA membrane in the isopropanol dehydration, different water-soluble fullerene derivatives with L-amino acids (threonine, hydroxyproline, and arginine) were used. In this study, fullerene–arginine derivative (C60-Arg) was shown to be an optimal filler acting both as a modifier and a cross-linking agent for SA. Different cross-linking agents (phosphoric and citric acids, calcium chloride) were tested for dense membrane cross-linking to reinforce the membranes for the separation of diluted solutions. Two types of membranes based on SA and SA/C60-Arg (5%) were developed: dense and supported on polyacrylonitrile substrate. The structural features of obtained membranes were investigated by the following methods: FTIR spectroscopy, scanning electron (SEM), and atomic force (AFM) microscopies. The optimal transport properties in dehydration of isopropanol (12–100 wt.% water) were found for the cross-linked SA/C60-Arg (5%) membrane supported on PAN substrate. The following parameters were obtained: 0.5–4.7 kg/(m2h) permeation flux and constant 99.99 wt.% water content in the permeate.

β-NaYF4:Eu3+ microparticles co-doped with Gd3+ ions were obtained by hydrothermal synthesis at 180 °C using citric acid as a stabilizing agent. All synthesized materials have a β-NaYF4 crystalline phase, where the unit cell volume increases upon the addition of Eu3+ and Gd3+ ions. The particles have a hexagonal prism shape and a size of 40–714 nm, where Eu3+ and Gd3+ doping results in size reduction. Upon 393 nm excitation, phosphors exhibit distinct emission peaks centered at 591, 615, and 695 nm and a weak band at 650 nm attributed to 5D0–7FJ transitions (J = 1–4). The optimum Eu3+ doping concentration was found to be 30% in the NaYF4 host. Concentration quenching was realized through dipole–dipole interactions. Kinetic measurements showed a gradual decline of the 5D0 lifetime from 6.7 ms to 2.2 ms along with an increase in Eu3+ doping concentration. Co-doping of the small Gd3+ number led to an increase of emission intensity and 5D0 lifetime. The effects of Eu3+ doping and Gd3+ co-doping on radiative and nonradiative decay rates were studied using 4f–4f intensity theory.

We present results of magneto-optical investigations of (CoFeB) x -(Al-O)100- x film nanocomposites in transverse Kerr effect (TKE) geometry in the spectral range 0.5–4.0 eV and magnetic field up to 3.1 kOe. Nanocomposites were deposited onto a glass-ceramic substrate by ion-beam sputtering. According to the data obtained from resistivity measurements, the percolation threshold is about x per a 57 at.%, and the critical concentration for metal–insulator transition is about x c a 48 at.%. The TKE response at room temperature strongly depends on the wavelength of light, applied magnetic field H , and the volume metallic fraction. The TKE field dependence is almost linear to H = 3.1 kOe and identical for 1.57 and 3.06 eV at x ≤ 30 at.%. It means that at x ≤ 30 at.%, nanocomposites consist of only superparamagnetic granules. With increasing concentration x , the TKE field dependence at 3.06 eV becomes more and more similar to the field dependence of ferromagnetic material, but it is not the case at 1.57 eV. For example, the TKE signal for x = 43 at.% measured at 3.06 eV saturates at H = 100 Oe, which indicates the presence of large ferromagnetic regions below x c. For the same composition, the TKE field dependence measured at 1.57 eV does not saturate and resembles more a superparamagnetic response. The same difference is observed also at x = 49 at.%. The presence of large ferromagnetic regions in completely insulating samples together with separate superparamagnetic granules can be considered as an evidence of superferromagnetic ordering in the vicinity of x c.

The development of new contactless thermal nanosensors based on a ratiometric approach is of significant interest. To overcome the intrinsic limitations of thermally coupled levels, a dual activation strategy was applied. Dual activation was performed using co-doped single nanoparticles and a binary mixture of single-doped nanoparticles. Co-doped and mixed YVO4:Nd3+/Eu3+ nanoparticles were successfully demonstrated as luminescent nanothermometers and their thermometric performance, in terms of thermal sensitivity, temperature resolution and repeatability, was studied and compared.

Magnetic Heusler alloys X2BZ (where X and B are 3d elements and Z belongs to the sp group) exhibit diverse magnetic and structural properties, which are important for designing multifunctional smart materials. Electronic band structure calculations demonstrate that, if the valence of element B is higher than that of element X, such alloys (so-called inverse Heusler alloys) can behave differently as compared to traditional Heusler alloys. The growth, the crystal structure, and the magnetic properties of thin films of a new Mn2FeSi Heusler alloy deposited under various conditions (including various substrates and annealing temperatures) are studied in this work. A temperature-induced structural transition into a low-magnetization martensitic phase and a thermally stable austenitic phase are detected. A magnetic field of 500 Oe applied to some samples at a temperature of 380 K is found to cause a large exchange bias (about 1 kOe) at T = 10 K. The influence of the type of substrate and the annealing temperature on the magnetic and structural properties of the films is discussed.

Accurate thermal sensing with good spatial resolution is currently required in a variety of scientific and technological areas. Luminescence nanothermometry has shown competitive superiority in contactless temperature sensing, especially at the nanoscale. To broaden the use of such thermometers, development of a novel sensor type with high sensitivity and resolution is highly demanded. Herein, we report single-phase Ln3+-doped YVO4 nanophosphors synthesized using a modified Pechini method as multimode optical thermometers for wide-range temperature probing (299–466 K). The observed temperature-induced red shift of the charge transfer band was utilized to provide thermal sensing. Temperature sensing was based on the luminescence intensity ratio using emission intensities obtained upon charge transfer and direct lanthanide excitation, the spectral position of the charge transfer band and its bandwidth. The suggested probing strategies provided a high relative thermal sensitivity (up to 3.09% K−1) and a precise temperature resolution (up to 0.1 K). The obtained results can be useful for the design of novel contactless luminescence thermometers.

Introduction. The distinctive feature of a coplanar transmission line with thin ferrite and ferroelectric films is the absence of undesirable irregularities in dispersion for relatively low frequencies when the wavelength approaches the thickness of ferroelectric layer, in contrast to the open ferrite-ferroelectric wave-guiding structure without metallization. Aim. The purpose of this paper is twofold: (i) to develop a theory of the wave spectra in the multiferroic structures based on the coplanar lines; (ii) using this theory to find ways to enhance the electric tuning range. Materials and methods . The dispersion relation for spin-electromagnetic waves was derived through analytical solution of the full set of the Maxwell's equations utilizing a method of approximate boundary conditions. Results. A theory of spin-electromagnetic wave spectrum has been developed for the thin-film ferrite-ferroelectric structure based on a coplanar transmission line. According to this theory, dispersion characteristics of the spin-electromagnetic waves were described and analyzed for different parameters of the structure. The obtained results show that the investigated structure demonstrates a dual electric and magnetic field tunability of wave spectra. Its efficiency increases with an increase in the thicknesses of the ferrite and ferroelectric films and with a decrease in the width of the central metal strip. Conclusion. The distinctive features of the proposed coplanar waveguides are the thin-film planar topology and dual tunability of the wave spectra. All these advantages make the proposed structures perspective for development of new microwave devices.

Functionalizing the internal structure of classical dendrimers is a new way of tailoring their properties. Using atomistic molecular dynamics simulations, we investigate the rheological behavior of functionalized dendrimers (FD) melts obtained by modifying the branching of carbosilane dendrimers (CSD). The time (relaxation modulus G(t)) and frequency (storage G' and loss G" moduli) dependencies of the dynamic modulus are obtained. Fourth generation FD melts present a region where G' > G". In contrast, their non-functionalized counterparts (i.e., classical dendrimers with a regular branching) do not show such a region. The comparative analysis of FD and CSD suggests that the internal densification due to functionalization prevents the penetration of branches and causes FD to behave like colloidal particles in a crowded environment. Since CSD have no special interactions, we expect that this effect will be common for other dendrimer macromolecules.

Functionalized dendrimers are a novel type of dendritic macromolecules that contain functionalized groups that do not take part in the dendrimer’s synthetic cycle. Focusing on the local dynamics of...

Novel membranes based on polyphenylene isophthalamide (PA) modified by fullerene derivatives (5 wt% with respect to PA weight) (polyhydroxylated fullerene (fullerenol), carboxyfullerene and fullerene derivative with L-arginine) were developed. The presence of PA/fullerene and PA/fullerene derivative composites and distribution of carbon nanoparticles after ultrasonic treatment in polymer solution was investigated by dynamic light scattering. The influence of carbon modifier on structural characteristics of PA was examined by nuclear magnetic resonance, small-angle X-ray scattering, scanning electron microscopy, atomic force microscopy, sorption experiments, density investigation and contact angle measurements of water. The transport properties were examined by pervaporation separation of industrially important methanol/toluene mixtures in two regimes (1. a series of experiments of different concentrations including azeotropic mixture and 2. only azeotropic mixture) to assess the effect of residual solvent in the PA membranes on their parameters. It was found that all membranes containing fullerene derivatives possessed improved permeation flux compared to pristine PA membrane. The optimal transport characteristics for the separation of methanol/toluene mixtures containing 10–72 wt% methanol were noticed for PA membrane modified by 5 wt% fullerenol due to the highest permeation fluxes (0.084–0.214 kg/(m2h)) and high level of selectivity (95.9 wt% methanol content in the permeate).

During last decade luminescence thermometry has become a widely studied research field due to its potential applications for real time contactless temperature sensing where usual thermometers cannot be used. Special attention is paid to the development of accurate and reliable thermal sensors with simple reading. To address existing problems of ratiometric thermometers based on thermally-coupled levels, LuVO

The electronic structure and metallicity of Si-doped Mn2VGe Heusler alloys within the first-principles density-functional theory framework are discussed. Mn2VGe is found to assume two stable structures at (cubic) lattice constants of 5.7 and 6.05 Å, which are well-separated in energy and correspond to half-metallic (low-spin) and metallic (high-spin) phases, respectively. Substitution of Ge by Si reduces the energy difference between these two phases, which become nearly degenerate at an Si concentration of ≈3.125 at% at zero temperature. The analysis shows that the switching between the high- and low-spin phases for this composition can be triggered via a pressure of 2.8 GPa at 300 K. Si-doped Mn2VGe can thus provide an ultrafast, low power, cost-effective materials platform for spintronics applications. Post-print / Final draft

The closest environment of Al

For the first time, the 3(X + M)LCT origin of both the lowest excited triplet states of dual-emissive tetranuclear copper(I)-iodide complexes with the octahedral Cu4I4 core has been revealed using quantum chemical computations in contrast to the conventional assignment of the lowest-energy emission to the 3CC state. The unusual thermochromic behavior shown for dual emission from these states of Cu4I4 clusters stabilized by P,N-ligands allows optical ratiometric thermal sensing in a broad temperature range.

Eu3+-doped MgAl2O4 nanoparticles were prepared by modified Pechini method. X-ray diffraction analysis shows pure tetragonal spinel phase without any impurities. The average size of synthesized nanoparticles was determined to be about 50–60 nm using scanning electron microscopy and static light scattering techniques. Emission and excitation spectra as well as lifetimes of MgAl2O4:Eu3+ nanophosphors were explored in surrounding media with different refractive indexes. Surrounding medium does not affect luminescence bands position, whereas 5D0 lifetime monotonically decreases along with increase of medium refractive index. Effect of surrounding media on radiative and nonradiative decay rates, which were calculated using 4f–4f intensity theory, was studied and discussed. Filling factor of prepared nanoparticles is defined using both radiative and observed lifetimes.

Two metamagnetic Heusler alloys based on Ni45Cr5Mn37In13 with differing Mn concentrations (by 0.2 at. %) were studied using magnetization, resistivity, and Hall resistivity measurements. It is shown that this small variation in composition leads to fundamental changes in magnetic properties. Near the martensitic phase transitions, the anomalous Hall coefficient (RS) was found to increase with temperature while the resistivity (ρ) decreases. Thus, in the case of Ni45Cr5Mn37In13, the general correlation between RS and ρ, considered as applicable for all crystalline and amorphous ferromagnetic alloys, breaks down completely. We explain this behavior in the framework of an s-d model where it is assumed that the resistivity and anomalous Hall effect are determined by different groups of current carriers.

We present investigation of microwave permeability of thin supermalloy films deposited on a flexible substrate. The permeability measurements are performed by transmission-reflection technique in a coaxial line under external magnetic bias in the frequency range of 100 MHz–20 GHz. It is shown that demagnetization does not affect the measurements when bias is above 150 Oe. Magnetic characteristics of the films are determined by two approaches: (i) fitting of the resonant frequency dependence on magnetic bias by Kittel's equation and (ii) calculation of the parameters from the Landau–Lifshitz–Gilbert dispersion law. Both approaches give close results for values of magnetoelastic field, anisotropy field, saturation magnetization, and damping factor.

The contactless real-time temperature sensing technique with high temporal and spatial resolution is in high demand for the countless applications. Here, the Yb3+/Er3+−codoped GeO2–PbO–PbF2 glass ceramics synthesized via the melt-quenching technique has been presented as an optical thermometer. The thermal sensing was designed based on the temperature dependent fluorescence intensity ratios of thermally (2H11/2 and 4S3/2) and non-thermally (2H11/2 and 4F9/2) coupled Er3+ levels. The ratiometric techniques provide the thermal sensing within the temperature range of 300–466 K. The absolute and relative thermal sensitivities as well as the temperature resolution were calculated and compared with other Yb3+/Er3+-doped materials. The temperature of the microelectronic component on the printed circuit board was defined using the optical thermometry as a proof of concept revealing Yb3+/Er3+−codoped GeO2–PbO–PbF2 phosphor to be a promising candidate for precise non-contact thermal sensor.

With the aim to analyze the microstructure of the polar nanoregions of mixtures of ionic liquids and inorganic salts and the single particle dynamics of metal cations in these densely ionic environments, solutions of inorganic nitrate salts (lithium, magnesium, calcium and aluminium nitrates) in the protic ionic liquid ethylammonium nitrate have been characterized by means of nuclear magnetic resonance. The measured spectra reveal that, despite being dried under vacuum, all the studied mixtures contained variable amounts of water, but, while in those with the salt cations of lower ionic potentials (Li+, Ca2+) only bulk free water that can be almost completely removed from the mixture is found, mixtures with the cations of higher ionic potentials (Mg2+, Al3+) contain only hydration water structurally anchored in the primary solvation shells of the metal cations forming coordination complexes inside the polar nanoregions of the densely ionic solvent and, thus, non-removable under vacuum. This hydration water is not properly detected by common Karl Fisher methods and these solutions are sometimes mistakenly considered anhydrous. Moreover, our NMR measurements confirm the nanostructured solvation paradigm, since they show that the influence of the addition of salt on the chemical shifts of the signals associated to hydrogen atoms in the apolar regions of the protic ionic liquid is negligible. Single-particle dynamics of cations of low and high ionic potentials was also studied, and our observations for the diffusion coefficients of lithium and aluminium cations support the conclusion that Li+ diffusion takes place inside anhydrous [Li(NO3)4]3− complexes, while kinetic complexes with Al3+ gather around [Al(H2O)6]3+) aqua ions.

Development of new approaches to the noncontact optical thermometry is of great importance for modern science and technology. In the current work, single-phase YVO4:Eu3+ nanoparticles prepared via ...

We report systematic study of Dy3+-doped YVO4 nanophosphors synthesized via modified Pechini technique. Effect of calcination temperature and doping concentration on structure and luminescence has been investigated. XRD and Raman spectroscopy revealed preparation of single phase nanoparticles without any impurities. Synthesized nanopowders consisted of weakly agglomerated nanoparticles with average size about 50 nm. Photoluminescence spectra of YVO4:Dy3+ nanoparticles consisted of the characteristic narrow lines attributed to the intra-configurational 4f-4f transitions dominating by the hypersensitive 4F9/2–6H13/2 transition. The calcination temperature variation did not affect 4F9/2 lifetime, whereas increase of doping concentration resulted in its gradual decline. Potential application of YVO4:Dy3+ 1 at.% and 2 at.% nanopowders as ratiometric luminescence thermometers within 298–673 K temperature range was tested. The main performances of thermometer including absolute and relative thermal sensitivities and temperature uncertainty were calculated. The maximum relative thermal sensitivity was determined to be 1.8% K−1@298 K, whereas the minimum temperature uncertainty was 2 K.

The adiabatic temperature change (ATad) in Ni 45 Mn 43 CoSn 11 has been measured by a direct method in magnetic field changes up to 14 T. Large reversible magnetocaloric effects resulting in AT ad of about = -11 and 5 K have been observed for magnetic field changes of 14 T at the magnetostructural (T A ~ 260 K) and magnetic transitions (T C ~ 320 K), respectively. The impact of the thermomagnetic history on AT ad at high magnetic fields has been reported. The significant observed changes in the relaxation time of AT ad , depending on the type of the phase transitions, magnetization, and demagnetization cycle are discussed.

We present density functional theory calculations to study the interplay between magnetic and structural properties in Ni-Co-Mn-Sn. The relative stability of austenite (cubic) and martensite (tetragonal) phases depends critically on the magnetic interactions between Mn atoms. While the standard generalized gradient approximation (GGA) stabilizes the latter phase, correlation effects beyond GGA tend to suppress this effect. Mn atoms treated as magnetic impurities can explain our results, where a delicate balance between magnetic interactions mediated by Ni d and Sn p orbitals determines the equilibrium structure of the crystal. Finally, we discuss the role of Co doping in stabilizing ferromagnetic austenite phases.

Due to their well-defined structure, multivalency, biocompatibility, and low toxicity, lysine dendrimers can be used as safe and efficient nanocarriers for drug and gene delivery. One useful strategy for improving the gene delivery properties of dendrimers is modification with arginine amino acid (Arg) residues. Incorporation of Arg residues could be favorable for the enhancement in transfection efficiency of lysine based dendrimers. In this work, we have synthesized a new second-generation poly-L-lysine dendrimer with repeating units containing two linear Arg residues between neighboring lysine branching points (Lys-2Arg dendrimer) and studied its physicochemical properties. We confirmed the structure of Lys-2Arg dendrimer using various one- and two-dimensional 1H and 13C NMR spectroscopy methods. Comparison of T1H relaxation data for Lys-2Arg and Lys-2Lys dendrimers showed that the replacement of double Lys residues with double Arg residues resulted in a sharp decrease in the mobility of methylene groups in side segments and in the main chain of e-Lys inner segments. We suggest that this unexpected effect is caused by a guanidine–guanidine pairing effect in water, which leads to entanglements between dendrimer branches.

A nonlinear spin-wave (magnonic) logic gate based on the ferrite-film Mach-Zehnder interferometer was realized. The gate has two inputs and one output. The principle of operation of the device is based on the power-dependent phase shift of spin waves propagating in an yttrium iron garnet film. A XOR logic functionality for two digital data streams supplied to the gate inputs is shown. No control signal is needed for the gate operation. The performance characteristics of the device are discussed. Reliable functionality in the pulsed regime at 50 and 250 kb/s is demonstrated.

Development of new contactless thermometers with improved characteristics is highly demanded for science and technology. In this work, we present upconverting Tm3+/Yb3+-doped GeO2–PbO–PbF2 glass ceramics as optical temperature sensor. Upon 973 nm laser excitation, sample generates intense emission bands from blue to NIR regions due to ladder-like energy levels of Tm3+ ion. A ratiometric technique involving the Tm3+ thermally and non-thermally coupled levels (1G4(a), 1G4(b), 3F2,3, 3H4) and spectral line position of 3H4–3H6 transition was used to provide thermal sensing in the 300–466 K temperature range. The performance of suggested sensing parameters was compared and discussed in terms of relative thermal sensitivity. The maximal thermal resolution, which can be achieved using Tm3+/Yb3+-doped GeO2–PbO–PbF2 thermometers, is better than 1 K at both 303 and 465 K. The obtained results show the potential use of GeO2–PbO–PbF2: Tm3+,Yb3+ phosphor for optical sub-degree temperature sensing.

Here, we report Nd3+-doped Y2O3 nanoparticles suitable for luminescence thermal sensing in the first and second biological windows. The nanoparticles were synthesized via the combined Pechini-foaming method. A ratiometric approach, based on the relative changes in the intensities of different emission bands corresponding to the Stark sublevels or excited levels, was applied to determine local temperature. The evaluated thermal sensitivities differed 5-fold times depending on the choice of transitions for the luminescence intensity ratio calculation. The temperature uncertainty was determined to be below 1 °C, which allows to perform sub-degree thermal sensing. The results of ex vivo experiment indicate that Nd3+-doped Y2O3 nanoparticles are promising candidates for real biological applications.

In this work we present the study of electrochemical properties of the composites based on cellulose nanofibers and a conductive polypyrrole that can be used as an electrode in supercapacitors. Samples have been prepared by two methods: in situ polymerization of pyrrole in the presence of cellulose nanofibers directly on the graphite plate used as a current collector and by precipitation of the dispersion of polypyrrole-cellulose nanofibers prepared ex situ onto the graphite electrode. Higher specific capacitance up to 4.08 F/cm2 (810 F/g) for in situ prepared sample in comparison with 1.87 F/cm2 (371 F/g) for ex situ sample was measured. Investigation with galvanostatic charge-discharge and electrochemical impedance spectroscopy revealed that the sample prepared by precipitation of dispersion demonstrate higher double-layer capacitance, electrode prepared via in situ polymerization demonstrates higher pseudocapacitance. Analysis of electrochemical data with equivalent circuit allows to propose that deviation from ideal capacitance behavior is caused by chemical inhomogeneity of surface of prepared materials rather than by their porous structure.

It is shown that the transport properties of graphitized silicon carbide are controlled by a surface graphene layer heavily doped with electrons. In weak magnetic fields and at low temperatures, a negative magnetoresistance is observed due to weak localization. A crossover in the magnetoresistance from weak localization to weak antilocalization (the latter is the manifestation of the isospin in graphene) is observed for the first time in samples of this kind at elevated temperatures. A pronounced pattern of Shubnikov–de Haas oscillations is observed in strong magnetic fields (up to 30 T). This pattern demonstrated fourfold carrier spectrum degeneracy due to the double spin and double valley degeneracies. Also, the manifestation of the Berry phase is observed. The effective electron mass is estimated to be m* = 0.08m0, which is characteristic of graphene with a high carrier concentration.

A theory of spin-electromagnetic wave spectrum has been developed for the thin-film ferrite-ferroelectric structure based on a coplanar transmission line (TL). The dispersion relation was derived through analytical solution of the full set of Maxwell’s equations utilizing a method of approximate boundary conditions. The theory was used for numerical simulation of the transmission characteristics of the periodic multiferroic heterostructures containing the coplanar TL with a periodic variation of its width. We named these heterostructures “electromagnonic crystals.” The transmission characteristics of the electromagnonic crystals were calculated by the transfer-matrix method. The obtained results show that a high microwave signal rejection of more than 30 dB appears in the electromagnonic crystals due to the Bragg reflections. The distinctive features of the proposed electromagnonic crystals are the thin-film planar topology and dual tunability of the electromagnonic band-gap positions.

Transport characteristics of sodium alginate (SA) membranes cross-linked with CaCl2 and modified with fullerenol and fullerene derivative with L-arginine for pervaporation dehydration were improved applying various approaches, including the selection of a porous substrate for the creation of a thin selective SA-based layer, and the deposition of nano-sized polyelectrolyte (PEL) layers through the use of a layer-by-layer (Lbl) method. The impacts of commercial porous substrates made of polyacrylonitrile (PAN), regenerated cellulose, and aromatic polysulfone amide were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), standard porosimetry method, and water filtration. The effects of PEL combinations (such as poly(sodium 4-styrene sulfonate) (PSS)/SA, PSS/chitosan, PSS/polyacrylic acid, PSS/poly(allylamine hydrochloride)) and the number of PEL bilayers deposited with the Lbl technique on the properties of the SA and SA/fullerene derivative membranes were studied by SEM, AFM, and contact angle measurements. The best characteristics were exhibited by a cross-linked PAN-supported SA/fullerenol (5%) membrane with five PSS/SA bilayers: permeation flux of 0.68–1.38 kg/(m2h), 0.18–1.55 kg/(m2h), and 0.50–1.15 kg/(m2h), and over 99.7, 99.0, and 89.0 wt.% water in the permeate for the pervaporation dehydration of isopropanol (12–70 wt.% water), ethanol (4–70 wt.% water), and tetrahydrofuran (5.7–70 wt.% water), respectively. It was demonstrated that the mutual application of bulk and surface modifications essentially improved the membrane’s characteristics in pervaporation dehydration.

We propose a ferromagnetic Heusler alloy that can switch between a metal and a half-metal. Thiseffect can provide tunable spintronics properties. Using the density functional theory (DFT) withreliable implementations of the electron correlation effects, we find Mn2ScSi total energy curvesconsisting of distinct branches with a very small energy difference. The phase at low lattice crystalvolume is a low magnetic half-metallic state while the phase at high lattice crystal volume is a highmagnetic metallic state. We suggest that the transition between half-metallic and metallic statescan be triggered by a triaxial contraction/expansion of the crystal lattice or by an external magneticfield if we assume that the lattice is cubic and remains cubic under expansion/contraction. However,the phase at high volume can also undergo an austenite-martensite phase transition because of thepresence of Jahn-Teller active3delectrons on the Mn atoms., Comment: Supplementary materials is located on https://journals.aps.org/prb/supplemental/10.1103/PhysRevB.103.054414

By combining the 3D printing, electroplating and chemical vapor deposition processes we fabricated “bubble wrap” polymer nanomembrane covered with multilayered graphene. Such a metasurface composed of array of graphene hemispheres shows extremely broadband and almost perfect absorption in terahertz (THz) 2 frequency range being robust against macroscopic structural defects including holes and volcanic-like hats on hemispherical metaatoms. The developed theory perfectly explains our experimental findings including virtual independence of the metasurface transmittivity, reflectivity and absorptivity on the angle of incidence in terms of the plasmon dark mode formation. Our approach enables the THz perfect absorber that covers a frequency range spanning from few hundreds of GHz to 1.2 THz, and even more, while the proposed fabrication technique can also be employed in numerous applications that require free standing corrugated graphene/polymer nanomembranes.

The present work focuses on the effect of vanadium dioxide (VO2) films exhibiting a metal–insulator transition (MIT) on the performance characteristics of the magnetic multilayers. It has been shown that the MIT provides a novel mechanism for controlling the microwave spin-wave dynamics in the yttrium iron garnet (YIG) films. In particular, the low and high levels of microwave attenuation of spin waves transmitted through the YIG–VO2 bilayer has been observed due to a variation of the VO2 conductivity within a narrow temperature range. This effect has been utilized to realize fully reconfigurable magnonic crystals composed of the thickness-modulated YIG and regular VO2 films. A promising functionality of the proposed waveguiding structures arises from a controllability of wave intensity, which provides an altering of the frequency response from an original band structure to a full rejection of spin waves. Numerical simulations taking into account both the YIG film saturation magnetization and the VO2 film conductivity have confirmed the experimentally observed spin-wave dynamics. An interest in ferrite–VO2 bilayers arises not only from possible practical applications but also from a variety of fundamental scientific problems devoted to the physics of wave phenomena in planar thin-film magnetic multilayers. Post-print / Final draft