Structural and transport properties of GaAs/delta<Mn>/GaAs/InxGa1-xAs/GaAs quantum wells

We report results of investigations of structural and transport properties of GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn layer, separated from the QW by a 3 nm thick spacer. The structure has hole mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher than in known ferromagnetic two-dimensional structures. The analysis of the electro-physical properties of these systems is based on detailed study of their structure by means of high-resolution X-ray diffractometry and glancing-incidence reflection, which allow us to restore the depth profiles of structural characteristics of the QWs and thin Mn containing layers. These investigations show absence of Mn atoms inside the QWs. The quality of the structures was also characterized by photoluminescence spectra from the QWs. Transport properties reveal features inherent to ferromagnetic systems: a specific maximum in the temperature dependence of the resistance and the anomalous Hall effect (AHE) observed in samples with both "metallic" and activated types of conductivity up to ~100 K. AHE is most pronounced in the temperature range where the resistance maximum is observed, and decreases with decreasing temperature. The results are discussed in terms of interaction of 2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations related to random distribution of Mn atoms. The AHE values are compared with calculations taking into account its "intrinsic" mechanism in ferromagnetic systems.Comment: 15 pages, 9 figure

Pecularities of Hall effect in GaAs/{\delta}<Mn>/GaAs/In\timesGa1-\timesAs/GaAs (\times {\approx} 0.2) heterostructures with high Mn content

Transport properties of GaAs/{\delta}/GaAs/In\timesGa1-\timesAs/GaAs structures containing InxGa1-xAs (\times {\approx} 0.2) quantum well (QW) and Mn delta layer (DL) with relatively high, about one Mn monolayer (ML) content, are studied. In these structures DL is separated from QW by GaAs spacer with the thickness ds = 2-5 nm. All structures possess a dielectric character of conductivity and demonstrate a maximum in the resistance temperature dependence Rxx(T) at the temperature {\approx} 46K which is usually associated with the Curie temperature Tc of ferromagnetic (FM) transition in DL. However, it is found that the Hall effect concentration of holes pH in QW does not decrease below TC as one ordinary expects in similar systems. On the contrary, the dependence pH(T) experiences a minimum at T = 80-100 K depending on the spacer thickness, then increases at low temperatures more strongly than ds is smaller and reaches a giant value pH = (1-2)\cdot10^13 cm^(-2). Obtained results are interpreted in the terms of magnetic proximity effect of DL on QW, leading to induce spin polarization of the holes in QW. Strong structural and magnetic disorder in DL and QW, leading to the phase segregation in them is taken into consideration. The high pH value is explained as a result of compensation of the positive sign normal Hall effect component by the negative sign anomalous Hall effect component.Comment: 19 pages, 6 figure

Curing of epoxy resin DER-331by Hexakis (4-acetamidophenoxy) cyclotriphosphazene and properties of the prepared composition

The method of optical wedge revealed that the optimum temperature for compatibility of hexakis(4-acetamidophenoxy)cyclotriphosphazene (ACP) and DER-331 epoxy resin is in the range of 220–260◦C. The interdiffusion time of components at these temperatures is about 30 min. The TGA and differential scanning calorimetry (DSC) methods revealed the curing temperature of 280◦C for thiscomposition. IRspectroscopyconfirmedthatthereactionbetweentheresinandACPiscompleted within 10 mi

THE ANALYSIS OF PHYSICAL AND MECHANICAL CHARACTERISTICS OF FACING COMPOSITE MATERIALS CERAMAGE («SHOFU») AND ULTRAGLASS («VLADMIVA»)

According to the Ministry of Industry and Trade, the degree of dependence of the medical industry and practical medicine on imports is 81%. Critical dependence causes a shortage of inexpensive consumables, medicines and medical devices, and as a consequence of the increase in the cost of medical services, which is estimated as a threat to national security. In various regions of the Russian Federation in the general structure of dental care for patients in all age groups, dental arch defects range from 40 to 75%. Non-removable prosthetics for socially unprotected segments of the population are carried out mainly by bridges with lining the metal frame with hot-curing plastic, short-lived due to low strength characteristics, significant abrasion, and hygroscopicity. To a large extent, the service life of fixed prostheses is determined by the combination of the physicomechanical properties of the facing material, such as flexural strength, modulus of elasticity, and hardness. Flexural strength characterizes the ability of a material to resist unaxial occlusal loading, the modulus of elasticity determines the stiffness of a material and its ability to withstand applied loads without significant deformations, and the hardness characterizes the wear resistance of a material and its ability to withstand abrasion by antagonists. This paper presents the results of a study of the physicomechanical properties of facing composite materials: Ceramage (Shofu, Japan) and Ultra Glass (VladMiVa, Russia). The revealed differences in flexural strength, modulus of elasticity and Vickers microhardness of the material “UltraGlass” allow us to recommend it for widespread clinical use. Expanding the range of domestic materials for orthopedic dentistry by developing a coating composite material UltraGlass helps to improve the quality of dental care to the population with social benefits

The influence of intergranular interaction on the magnetization of the ensemble of oriented Stoner-Wohlfarth nanoparticles

We consider the influence of interparticle interaction on the magnetization reversal in the oriented Stoner-Wohlfarth nanoparticles ensemble. To do so, we solve a kinetic equation for the relaxation of the overall ensemble magnetization to its equilibrium value in some effective mean field. Latter field consists of external magnetic field and interaction mean field proportional to the instantaneous value of above magnetization. We show that the interparticle interaction influences the temperature dependence of a coercive field. This influence manifests itself in the noticeable coercivity at $T>T_{b}$ ($T_{b}$ is so-called blocking temperature). The above interaction can also lead to a formation of the "superferromagnetic" state with correlated directions of particle magnetic moments at $T>T_{b}$. This state possesses coercivity if the overall magnetization has a component directed along the easy axis of each particle. We have shown that the coercive field in the "superferromagnetic" state does not depend on measuring time. This time influences both $T_{b}$ and the temperature dependence of coercive field at $T<T_{b}$. We corroborate our theoretical results by measurements on nanogranular films (CoFeB)$_{x}$-(SiO$_{2}$)$_{1-x}$ with concentration of ferromagnetic particles close, but below percolation threshold

Wavelet treatment of the intra-chain correlation functions of homopolymers in dilute solutions

Discrete wavelets are applied to parametrization of the intra-chain two-point correlation functions of homopolymers in dilute solutions obtained from Monte Carlo simulation. Several orthogonal and biorthogonal basis sets have been investigated for use in the truncated wavelet approximation. Quality of the approximation has been assessed by calculation of the scaling exponents obtained from des Cloizeaux ansatz for the correlation functions of homopolymers with different connectivities in a good solvent. The resulting exponents are in a better agreement with those from the recent renormalisation group calculations as compared to the data without the wavelet denoising. We also discuss how the wavelet treatment improves the quality of data for correlation functions from simulations of homopolymers at varied solvent conditions and of heteropolymers.Comment: RevTeX, 19 pages, 7 PS figures. Accepted for publication in PR

CREATING OF THE HOT CELL FOR RESEARCHINGS OF THE BN-800 REACTOR’S ASSEMBLIES ON THE 4-TH POWER UNIT OF BELOYARSKAYA NPP

A hot cell of nuclear power plant’s power unit is a researching laboratory, where reactor assemblies are investigating for safety after work in the nuclear reactor. The 4-th power unit of Beloyarskaya NPP is still under construction. Creating of the hot cell within the power unit is critically important in case of modifying of the power core with new reactor assemblies filled by MOX-fuel

Fast calculation of thermodynamic and structural parameters of solutions using the 3DRISM model and the multi-grid method

In the paper a new method to solve the tree-dimensional reference interaction site model (3DRISM) integral equations is proposed. The algorithm uses the multi-grid technique which allows to decrease the computational expanses. 3DRISM calculations for aqueous solutions of four compounds (argon, water, methane, methanol) on the different grids are performed in order to determine a dependence of the computational error on the parameters of the grid. It is shown that calculations on the grid with the step 0.05\Angstr and buffer 8\Angstr give the error of solvation free energy calculations less than 0.3 kcal/mol which is comparable to the accuracy of the experimental measurements. The performance of the algorithm is tested. It is shown that the proposed algorithm is in average more than 12 times faster than the standard Picard direct iteration method.Comment: the information in this preprint is not up to date. Since the first publication of the preprint (9 Nov 2011) the algorithm was modified which allowed to achieve better results. For the new algorithm see the JCTC paper: DOI: 10.1021/ct200815v, http://pubs.acs.org/doi/abs/10.1021/ct200815

HYPERFINE INTERACTIONS IN IRON BORATE FeBO3

For the FeBO3 single crystal, the values of isomer shift, quadrupole constant and magnetic hyperfine field were determined for over a wide temperature range.Исследования выполнены при финансовой поддержке РФФИ, проект № 19-29-12016-мк, в части мёссбауэровских исследований и теоретического анализа. Рентгеновские измерения проведены при поддержке Министерства науки и высшего образования РФ в рамках выполнения работ по Государственному заданию ФНИЦ «Кристаллография и фотоника» с использованием оборудования ЦКП (проект RFMEFI62119X0035)