Crucial role of orbital structure in formation of frustrated magnetic structure in BiMnO3

The paper presents an investigation in the field of orbital physics of strongly correlated oxides. The theoretical study of vibronic mechanism of orbital and magnetic structures forming in BiMnO3 crystal is carried out. An effect of orbital structure upon superexchange interaction is described. Nonlinear and second-neighbor terms in vibronic interaction on manganese ions play an important role in magnetic ordering of frustrated BiMnO3. It is shown that the linear vibronic interaction is insufficient to describe the experimentally detected ferromagnetic structure of bismuth manganite. The new approach to orbital structure formation, presented in the paper, could be used not only in manganite physics but also in other Jahn-Teller compounds. © 2013 American Physical Society

Motion of vortices in ferromagnetic spin-1 BEC

The paper investigates dynamics of nonsingular vortices in a ferromagnetic spin-1 BEC, where spin and mass superfluidity coexist in the presence of uniaxial anisotropy (linear and quadratic Zeeman effect). The analysis is based on hydrodynamics following from the Gross-Pitaevskii theory. Cores of nonsingular vortices are skyrmions with charge, which is tuned by uniaxial anisotropy and can have any fractal value between 0 and 1. There are circulations of mass and spin currents around these vortices. The results are compared with the equation of vortex motion derived earlier in the Landau-Lifshitz-Gilbert theory for magnetic vortices in easy-plane ferromagnetic insulators. In the both cases the transverse gyrotropic force (analog of the Magnus force in superfluid and classical hydrodynamics) is proportional to the charge of skyrmions in vortex cores.Comment: 19 pages, 2 figures, to be published in the special issue of Fizika Nizkikh Temperatur dedicated to A.M.Kosevich. arXiv admin note: substantial text overlap with arXiv:1801.0109

Specific features of magnetic structure formation in orbitally degenerate BiMnO3 manganite

The orbital structure and magnetic ordering of the Jahn-Teller multiferroic BiMnO3 manganite have been theoretically studied. It is shown that the orbital structure depends not only on the nearest-neighbor oxygen environment of manganese ions, but also on their next-to-nearest neighbors. The orbital structure significantly influences the magnetic order that forms as a result of competition between ferromagnetic and antiferromagnetic exchange interactions. © 2013 Pleiades Publishing, Ltd

Hyperfine interactions in titanates: Study of orbital ordering and local magnetic properties

Hyperfine magnetic fields induced on the nuclei of nonmagnetic ions 139La and 89Y in LaTiO3 and YTiO3, respectively, have been microscopically calculated. The dependence of the hyperfine fields on the orbital and magnetic structures of the compounds under study has been analyzed. The comparative analysis of the calculated and known experimental data confirms the existence of the static orbital structure in lanthanum and yttrium titanates. © 2013 Pleiades Publishing, Ltd

Crystal structure of mixed fluorites Ca(1-x)Sr(x)F(2) and Sr(1-x)Ba(x)F(2) and luminescence of Eu(2+) in the crystals

Within the framework of the virtual crystal method implemented in the shell model and pair potential approximation the crystal structure of mixed fluorites Ca(1-x)Sr(x)F(2) and Sr(1-x)Ba(x)F(2) has been calculated. The impurity center Eu(2+) and the distance Eu(2+)-F in this crystals have been also calculated. The low level position of excited 4f65d configuration of the Eu(2+) ion has been expressed using phenomenological dependence on distance E(2+)-F. The dependences of Stokes shift and Huang-Rhys factor on concentration x have been received for yellow luminescence in Sr(1-x)Ba(x)F(2):Eu(2+). The value x, for which the eg -level of Eu(2+) ion will be in conduction band in Sr(1-x)Ba(x)F(2):Eu(2+) has been calculated.Comment: 8 pages, 3 figures. The manuscript is sent to journal 'Physics of the solid state'. The results will be submitted on inernational conference SCINTMAT'2002 in oral session (june,20-22,2002,Ekaterinburg,Russia). Corresponding author e-mail: [email protected]

Time-resolved characterization of a pulsed discharge in a stationary bubble

In recent years, plasma generation in water has been proposed for the application of water treatment. The process efficiency is believed to be improved by the introduction of bubbles in the plasma active region. For further optimization, the initiating and developmental mechanisms of plasma inside bubbles need to be understood to a greater extent. In order to meet this necessity, we investigated pulsed electrical discharge inside a stationary bubble in water. This paper deals with the evolution of the discharge and of the bubble shape during discharge, investigated by electrical characterization and fast imaging. Only several microseconds after the application of the voltage pulse, plasma light is observed. Different phases are observed during plasma formation. The plasma is strongest at the bubble surface, causing the surrounding water to evaporate. This leads to both the formation of propagating streamers into the water and the expansion and collapse of the bubble. These observations show that plasma inside a bubble has the strongest activity at the bubble surface, making it attractive for water treatment

Features of Dynamics of Antivibration Mounts with Inertial Hydraulic Converter Subjected to Vibro-Impact Loading

Antivibration mounts with inertial hydraulic converter are widely used to protect a variety of technical systems from shock and vibration. As it follows from existing literature, models of such a mounts on the basis of mechanical and mechanical-electrical analogies instead of real hydro-mechanical system are usually used to study their dynamic properties and design. These models are not able to describe fluid dynamics in hydraulic mount, and are not suitable to study rapidly changing processes, which is especially required for effective application of the mounts at vibro-shock loading. In this work, a model of inertial hydraulic converter, which is a system of two hydraulic cylinders of unilateral operating principle, connected by a rigid hydraulic tube, is described. Dynamics of fluid in hydraulic converter is described by the Navier-Stokes equations for a compressible fluid and the equation of state of the fluid in assumption of its isentropic motion. The results of numerical simulation of antivibration mount dynamics at shock loading by using finite element package ANSYS/LS-DYNA are presented. It is found out that increasing the length of the tube and reducing the tube diameter lead to an increase in the transmitted dynamic force