Anisotropy of the paramagnetic susceptibility in LaTiO3_{3}: The electron-distribution picture in the ground state

The energy-level scheme and wave functions of the titanium ions in LaTiO$_{3}$ are calculated using crystal-field theory and spin-orbit coupling. The theoretically derived temperature dependence and anisotropy of the magnetic susceptibility agree well with experimental data obtained in an untwinned single crystal. The refined fitting procedure reveals an almost isotropic molecular field and a temperature dependence of the van Vleck susceptibility. The charge distribution of the 3d--electron on the Ti positions and the principle values of the quadrupole moments are derived and agree with NMR data and recent measurements of orbital momentum $$ and crystal-field splitting. The low value of the ordered moment in the antiferromagnetic phase is discussed.Comment: 6 pages, 2 figures, 3 table

Synthesis and luminescence of lead(II)-activated cadmium sulfide in poly(methyl methacrylate)

Optically transparent polymeric materials PMMA: Cd(Pb)S have been synthesized by polymerization of methyl methacrylate, which concurrently acts as a reaction medium for synthesis of metal sulfides, dispersion medium for the resulting colloidal solution forming during synthesis, and the base of compositions. Dependences of cadmium sulfide luminescence on the concentrations, concentration ratios of the initial compounds, reaction medium composition, and temperature have been established. The observed changes in the spectra are related to the introduction of lead(II) into compositions, complex formation on the surface of colloidal particles, and the effect of polar acetonitrile

Anisotropic Exchange in LiCuVO4_4 probed by ESR

We investigated the paramagnetic resonance in single crystals of LiCuVO$_4$ with special attention to the angular variation of the absorption spectrum. To explain the large resonance linewidth of the order of 1 kOe, we analyzed the anisotropic exchange interaction in the chains of edge-sharing CuO$_6$ octahedra, taking into account the ring-exchange geometry of the nearest-neighbor coupling via two symmetric rectangular Cu-O bonds. The exchange parameters, which can be estimated from theoretical considerations, nicely agree with the parameters obtained from the angular dependence of the linewidth. The anisotropy of this magnetic ring exchange is found to be much larger than it is usually expected from conventional estimations which neglect the bonding geometry. Hence, the data yield the evidence that in copper oxides with edge-sharing structures the role of the orbital degrees of freedom is strongly enhanced. These findings establish LiCuVO$_4$ as one-dimensional compound at high temperatures. PACS: 76.30.-v, 76.30.Fc, 75.30.EtComment: 18 pages, 6 figure

Synthesis and luminescence spectra of poly(methyl methacrylate)/CdS:Ln(III) composites

Cadmium sulfide was prepared by colloidal synthesis in methyl methacrylate (MMA). Europium and terbium salts were added to the colloidal solutions. Using MMA radical polymerization, we synthesized PMMA/CdS:Eu(III), PMMA/CdS:Tb(III), and PMMA/CdS:Eu(III):Tb(III) luminescent composites. Their luminescence is due to defects in the CdS crystals and the 5Dо → 7Fj and 5D4 → 7Fj electronic transitions of the Eu3+ and Tb3+ ions, respectively. It depends on the composition of the materials, complexation on the surface of the colloidal particles, heat treatment time during synthesis, excitation wavelength, and other factors

Synthesis and absorption and luminescence spectra of poly(methyl methacrylate):Cd(Mn,Pb)S composites

The reaction of cadmium, manganese, and lead trifluoroacetates with thioacetamide in methyl methacrylate yielded colloidal solutions of metal sulfides with different Cd(II): Mn(II): Pb(II) molar ratios. The colloidal particles were separated from solutions and examined by electron microscopy. Glassy polymer composites poly(methyl methacrylate):Cd(Mn)S and poly(methyl methacrylate):Cd(Mn,Pb)S were prepared by thermal polymerization of methyl methacrylate in the bulk. The transmittance of the composites at wavelengths larger than 480 nm is 92% at the sample thickness of 0.40 cm. The luminescence of the composites in the visible range is associated with cadmium sulfide. The corresponding absorption bands were recorded in the luminescence excitation spectra in the wavelength interval 300–450 nm. The effect of the matrix, Mn(II) and Pb(II) ions, and synthesis conditions on the absorption and luminescence properties of the composites was determined

Spin correlations and Dzyaloshinskii-Moriya interaction in Cs2_2CuCl4_4

We report on electron spin resonance (ESR) studies of the spin relaxation in Cs$_2$CuCl$_4$. The main source of the ESR linewidth at temperatures $T \leq 150$ K is attributed to the uniform Dzyaloshinskii-Moriya interaction. The vector components of the Dzyaloshinskii-Moriya interaction are determined from the angular dependence of the ESR spectra using a high-temperature approximation. Both the angular and temperature dependence of the ESR linewidth have been analyzed using a self-consistent quantum-mechanical approach. In addition analytical expressions based on a quasi-classical picture for spin fluctuations are derived, which show good agreement with the quantum-approach for temperatures $T \geq 2J/k_{\rm B} \approx 15$ K. A small modulation of the ESR linewidth observed in the $ac$-plane is attributed to the anisotropic Zeeman interaction, which reflects the two magnetically nonequivalent Cu positions

The Concept of Democracy in U.S. Foreign Policy in a Post-Bipolar System

ntroduction. Democracy nowadays means not only specific parameters of domestic political, social and economic development, but has also become a tool for identifying “friends” and “strangers” for the USA and a number of other states of the so-called Western world. In addition, international law, calling the problem of human rights the most important one for the democratization of the world, denotes the possibility of interference of the states concerned in the internal affairs of other countries. Methods and materials. The study was conducted in accordance with the epistemological orientations of social constructivism using the case-study ethod. Analysis. The logic of analysis assumes considering a concept of democracy from the position of the theory of the democratic world with its verification on USA political practice including their participation in contemporary local and regional conflicts. Results. Thus, democracy becomes a complex tool that allows the USA to solve several problems at once: to divide between states, to influence the domestic politics of other states, to change its position in the international arena, to spread its values, to conceal its foreign policy goals by dressing them up in “democratic” clothes. The U.S., considering itself a model democratic state, identifying other countries as its allies or enemies, at the same time gives them the status of “democratic” or “non-democratic”, or, if necessary, avoiding such a designation (in the case of Saudi Arabia)

The innovative organizational forms of the educational process as a way to implement professional standards

This article analyzes innovative organizational forms of educational process in the preparation of college teachers. Under the new conditions the development of the educational program associated with the job functions of professional standards and complement the competences list of the federal state educational standard of college’s profile-specialized competencies. Innovative organizational forms of educational process of college teachers training, which was built with the professional standards, are network education and modular training.Анализируются инновационные формы организации образовательного процесса в подготовке педагогов профессионального обучения. В новых условиях разработка образовательной программы связана с учетом трудовых функций профессионального стандарта и дополнением перечня компетенций Федерального государственного образовательного стандарта высшего образования профильно-специализированными компетенциями. Инновационными формами организации образовательного процесса подготовки педагога профессионального обучения, построенного с учетом профессионального стандарта, являются сетевая форма и модульное обучение

Features of Financial and Economic Development in the Period of Coronavirus: Experience of the Baltic States as Members of the European Union

The combination of two types of crisis: epidemiological and economic creates a fundamentally new and difficult situation for European integration. The authors do not share a view suggesting a qualitative weakening or even a complete disintegration of the European Union. However, the processes taking place are not indicative of the ordinary nature of the problems. In these circumstances, contradictions are escalating not only between North and South, which has been much written about recently, but also between West and East of the EU. “East’ includes the Baltic states in dire need of financial resources right now