Spatial inversion of gyrotropy parameter in conductivity tensor and charge transport peculiarities

Charge transfer is discussed for the case when gyrotropy parameter (Hall coefficient) varies along transport л-direction and inverses its sign. This situation takes place in contacts of the serially joined materials having electron and hole types of conductivity. Spatial inhomogeneity of conductivity and inversion of Hall coefficient sign are analyzed in terms of electric potential and current density distribution. It is shown that under inhomogeneous magnetic field the steady current skinning takes place in plate sample

Magnetostimulated inhomogeneity of electric field in aluminum

The results of low temperature experimental and theoretical study of potential distribution of stationary electric field in Al under the action of inhomogeneous magnetic field are presented

Momentum-resolved lattice dynamics of parent and electron-doped Sr2_{2}IrO4_{4}

The mixing of orbital and spin character in the wave functions of the $5d$ iridates has led to predictions of strong couplings among their lattice, electronic and magnetic degrees of freedom. As well as realizing a novel spin-orbit assisted Mott-insulating ground state, the perovskite iridate Sr$_{2}$IrO$_{4}$ has strong similarities with the cuprate La$_{2}$CuO$_{4}$, which on doping hosts a charge-density wave that appears intimately connected to high-temperature superconductivity. These phenomena can be sensitively probed through momentum-resolved measurements of the lattice dynamics, made possible by meV-resolution inelastic x-ray scattering. Here we report the first such measurements for both parent and electron-doped Sr$_{2}$IrO$_{4}$. We find that the low-energy phonon dispersions and intensities in both compounds are well described by the same nonmagnetic density functional theory calculation. In the parent compound, no changes of the phonons on magnetic ordering are discernible within the experimental resolution, and in the doped compound no anomalies are apparent due to charge-density waves. These measurements extend our knowledge of the lattice properties of (Sr$_{1-x}$La$_{x}$)$_{2}$IrO$_{4}$ and constrain the couplings of the phonons to magnetic and charge order.Comment: 8 pages, 6 figures (+ 12 pages, 6 figures of supplemental material

First-order transition between a small-gap semiconductor and a ferromagnetic metal in the isoelectronic alloys FeSi1−x_{1-x}Gex_x

The contrasting groundstates of isoelectronic and isostructural FeSi and FeGe can be explained within an extended local density approximation scheme (LDA+U) by an appropriate choice of the onsite Coulomb repulsion, $U$ on the Fe-sites. A minimal two-band model with interband interactions allows us to obtain a phase diagram for the alloys FeSi$_{1-x}$Ge$_{x}$. Treating the model in a mean field approximation, gives a first order transition between a small-gap semiconductor and a ferromagnetic metal as a function of magnetic field, temperature, and concentration, $x$. Unusually the transition from metal to insulator is driven by broadening, not narrowing, the bands and it is the metallic state that shows magnetic order.Comment: 4 pages, 5 figure

On the appearance of space temperature electric structures in hyperconductors under high magnetic fields

As part of the study of low temperature galvanomagnetic properties of high purity A1 in the Corbino geometry the voltage-current characteristics (IV) under external transverse magnetic field in the regime of given current revealed the effects of voltage stabilization. Here we attempt to ascribe these phenomena to appearance in the sample of bulk temperature structures characteristic of highly nonequilibrium systems. Joule’s heat of flowing electric current gives rise to disk warming. We also discuss the problems of the influence of warming in disks on the phenomena of electric transport with allowance for own magnetic fields being generated in disk

The temperature fields in electrically heated wires at crisis of boiling

The self-organization processes take place in several phenomena and physical objects and in particular they arise in metals in conditions of charge transfer. At liquid helium temperature in conditions of the increase of direct current flowing through bismuth, indium and tungsten there arise unstabilities of charge carries flux and this process exhibits itself in electromagnetic oscillations generation. This instability the authors refer to the mutual influence of the current flowing through the sample and magnetic field of the current. With this heat flux density through the sample’s surfaces didn’t exceed 0.1 W/sm2. Such a value of heat flux is сlose to the first boiling crisis but the author state that the nature of these phenomena is no case is connected with the heat removal specific features

Reactive rimming flow of non-Newtonian fluids

The steady and non-steady flows of a liquid polymer treated as a non-Newtonian fluid on the inner surface of a horizontal rotating cylinder are investigated. Since the Reynolds number is small and the liquid film is thin, a simple lubrication approximation is applied. Governing equations for non-steady Power-Law and Ellis fluids are solved numerically and the time of transition from non-steady to steady-state mode for various model parameters and flow conditions are defined. The stabilization effect of a chemical reaction within the polymeric fluid (reactive flow) is examined.© 2013 Elsevier Inc. All rights reserved

Novel concept of hyperconducting concentrator of magnetic energy

The properties of Hall drift of electrons and generation of respective self magnetic field are examined. The problem of design of high effective cryogenic generator of magnetic field advances the requirement of optimization of magnetic system geometry for the most magnitude of field to be obtained in the same volume at the same energy supply. Besides an electron drift along electric field there is a transverse drift of carriers stimulated by Lorentz force if magnetic field is applied. Generally transverse Hall drift as a source of magnetic field is ignored. A paper is represented here to indicate a novel way of improvement of magnetic system arrangement and efficiency. It is based on validity of use the energy concentrator made from high purity aluminum. Such concentrator may be installed into traditional solenoid and as a consequence the magnitude of magnetic field will increase. An experiment on A1 disk conductors having inner and outer concentric current leads is made in coaxial magnetic field of 8T. Current density is sufficient to achieve a boiling crisis of helium. It is shown that magnetic field of solenoid will be increased in volume of concentrator in accordance with power type law instead of summation taking place in many layer solenoid system. The benefits and advantages of application of magnetic field of Hall drift arc discussed. Parameters together with all necessary requirement for operation are represented for cryogenic range of temperature 4.2–30 K. Research is supported by Fund of Fundamental Investigations of the Republic of Belarus

Barium vanadium silicate BaVSi2O7: A t2g counterpart of the Han purple compound

By means of thermodynamic and magnetic resonance measurements the S = 1/2 dimer system BaVSi2O7 is characterized. A broad maximum in the temperature dependence of the magnetic susceptibility and a Schottky-type anomaly in the specific heat allows estimating the main exchange interaction within V4+-V4+ dimers as J=37±1 K. This estimation is confirmed by pulsed magnetic field measurements of the magnetization, which is evidenced by the field-induced singlet-triplet transition at about 27 T. Both X-band and high-field terahertz electron spin resonance data qualitatively agree with the results of the specific heat and magnetization measurements. The electronic structure calculations, by using local density approximation, indicate that the magnetic properties of BaVSi2O7 can be interpreted within the weakly interacting dimer model. © 2013 American Physical Society