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

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

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

Dental composition modified with aryloxyphosphazene containing carboxyl groups

A modifier consisting of the mixture of cyclotriphosphazenes containing 4-allyl-2-methoxyphenoxy and β-carboxyethenylphenoxy moieties was developed for administration with acrylate dental restorative compositions. The synthesized compounds were characterized by 1H and 13C NMR spectroscopy and MALDI-TOF mass spectrometr

Study of analgesic activity and effects of new dipharmacophores - nebracetam and cyclooxygenase-2 inhibitors derivatives on the cognitive abilities of rats

The aim of the present study was to research the analgesic activity and effect of new dipharmacophore compounds consisting of substances with proven therapeutic activity, namely nebracetam-ibuprofen (NRIP), nebracetam-dexibuprofen (NRDIP), nebracetam-niflumic acid (NRNFA), and nebracetam-mefenamic acid (NRMFA), on the cognitive abilities of rat

Crystal structure of the non-steroidal anti-inflammatory drug (NSAID) tolmetin sodium

The asymmetric unit of the title compound, sodium 2-[1-methyl-5-(4-methylbenzoyl)- 1H-pyrrol-2-yl]acetate dihydrate, Na⁺C₁₅H₁₄NO₃⁻2H₂O, contains two sodium cations, two organic anions (A and B) and two water molecules. The coordination geometry around the sodium cations corresponds to a distorted octahedro

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

Methacrylate compositions modified by oligosilsesquioxanes with methacryl and cyclotriphosphazene substituents

Triethoxysilylphosphazenes have been synthesized via hydrosilylation of cyclotriphosphazenes with various contents of 4-allyl-2-methoxyphenoxy groups by triethoxysilane at an equimolar phosphazene - silane ratio. Hydrolytic copolycondensation of the latter compounds with γ-methacryloxypropyltrimethoxy - silane resulted in oligosiloxanes involving functional methacrylic and phosphazene fragment