WorldWideScience

Sample records for strong magnetized double

  1. Strong double layer in the downward current region.

    Science.gov (United States)

    Andersson, L.; Ergun, R. E.; Newman, D.; McFadden, J. P.; Carlson, C. W.

    2001-12-01

    A direct observation of a strong double layer has been recorded in detail by the FAST satellite in the downward current region of the aurora. This presentation concentrates on a particular compelling example in which both the electric field and particle measurements clearly illustrate the detail characteristics of the double layer. Electrons with initial energies of about 50 eV are observed to be accelerated through the double layer into a beam of more than 750 eV. This beam is rapidly plateaued by intense wave turbulence into a extended power law distribution. This process forms accelerated `flat-top' electron distributions, which are represented of energized distributions in the downward current region. Ions are also observed to be accelerated by the double layer in the opposite direction of the electron beam. Ion conics on the low potential side of the double layer are trapped between the double layer and their mirror points. The double layer is observed to move up the magnetic field line, in the direction of the electron beam. In front of it, an ion population moves with the speed of the double layer suggesting an overshoot in the potential ramp. The intense wave turbulence on the high potential side is seen to transform into electron phase-space holes far away from the double layer.

  2. Strong Double Higgs Production at the LHC

    CERN Document Server

    Contino, Roberto; Moretti, Mauro; Piccinini, Fulvio; Rattazzi, Riccardo

    2010-01-01

    The hierarchy problem and the electroweak data, together, provide a plausible motivation for considering a light Higgs emerging as a pseudo-Goldstone boson from a strongly-coupled sector. In that scenario, the rates for Higgs production and decay differ significantly from those in the Standard Model. However, one genuine strong coupling signature is the growth with energy of the scattering amplitudes among the Goldstone bosons, the longitudinally polarized vector bosons as well as the Higgs boson itself. The rate for double Higgs production in vector boson fusion is thus enhanced with respect to its negligible rate in the SM. We study that reaction in pp collisions, where the production of two Higgs bosons at high pT is associated with the emission of two forward jets. We concentrate on the decay mode hh -> WW^(*)WW^(*) and study the semi-leptonic decay chains of the W's with 2, 3 or 4 leptons in the final states. While the 3 lepton final states are the most relevant and can lead to a 3 sigma signal significa...

  3. Double perovskites with strong spin-orbit coupling

    Science.gov (United States)

    Cook, Ashley M.

    We first present theoretical analysis of powder inelastic neutron scattering experiments in Ba2FeReO6 performed by our experimental collaborators. Ba2FeReO6, a member of the double perovskite family of materials, exhibits half-metallic behavior and high Curie temperatures Tc, making it of interest for spintronics applications. To interpret the experimental data, we develop a local moment model, which incorporates the interaction of Fe spins with spin-orbital locked magnetic moments on Re, and show that it captures the experimental observations. We then develop a tight-binding model of the double perovskite Ba 2FeReO6, a room temperature ferrimagnet with correlated and spin-orbit coupled Re t2g electrons moving in the background of Fe moments stabilized by Hund's coupling. We show that for such 3d/5d double perovskites, strong correlations on the 5d-element (Re) are essential in driving a half-metallic ground state. Incorporating both strong spin-orbit coupling and the Hubbard repulsion on Re leads to a band structure consistent with ab initio calculations. The uncovered interplay of strong correlations and spin-orbit coupling lends partial support to our previous work, which used a local moment description to capture the spin wave dispersion found in neutron scattering measurements. We then adapt this tight-binding model to study {111}-grown bilayers of half-metallic double perovskites such as Sr2FeMoO6. The combination of spin-orbit coupling, inter-orbital hybridization and symmetry-allowed trigonal distortion leads to a rich phase diagram with tunable ferromagnetic order, topological C= +/-1, +/-2 Chern bands, and a C = +/-2 quantum anomalous Hall insulator regime. We have also performed theoretical analysis of inelastic neutron scattering (INS) experiments to investigate the magnetic excitations in the weakly distorted face-centered-cubic (fcc) iridate double perovskites La2ZnIrO 6 and La2MgIrO6. Models with dominant Kitaev exchange seem to most naturally

  4. Strong and superstrong pulsed magnetic fields generation

    CERN Document Server

    Shneerson, German A; Krivosheev, Sergey I

    2014-01-01

    Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

  5. Thermodynamical instabilities under strong magnetic fields

    Science.gov (United States)

    Chen, Y. J.

    2017-03-01

    The thermodynamical instabilities of low densities in the n p matter and n p e matter are studied within several relativistic nuclear models under some values of magnetic fields. The results are compared between each other and the effects of the symmetry energy slope at saturation density on the instability are investigated. The instability regions can exhibit bands due to the presence of Landau levels for very strong magnetic fields of the order of 1017 G, while for weaker magnetic fields, the bands are replaced by many diffused or scattered pieces. It also shows that the proton fraction in the inner crust of neutron stars may be complex under strong magnetic fields.

  6. Hydrogen atoms in a strong magnetic field

    International Nuclear Information System (INIS)

    Santos, R.R. dos.

    1975-07-01

    The energies and wave functions of the 14 lowest states of a Hydrogen atom in a strong magnetic field are calculated, using a variational scheme. The equivalence between the atomic problem and the problems related with excitons and impurities in semiconductors in the presence of a strong magnetic field are shown. The calculations of the energies and wave functions have been divided in two regions: the first, for the magnetic field ranging between zero and 10 9 G; in the second the magnetic field ranges between 10 9 and 10 11 G. The results have been compared with those obtained by previous authors. The computation time necessary for the calculations is small. Therefore this is a convenient scheme to obtain the energies and wave functions for the problem. Transition probabilities, wavelengths and oscillator strengths for some allowed transitions are also calculated. (Author) [pt

  7. Bound states in a strong magnetic field

    International Nuclear Information System (INIS)

    Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G.; Ferreira Filho, L. G.

    2013-01-01

    We expect a strong magnetic field to be produced in the perpendicular direction to the reaction plane, in a noncentral heavy-ion collision . The strength of the magnetic field is estimated to be eB∼m 2 π ∼ 0.02 GeV 2 at the RHIC and eB∼ 15m 2 π ∼ 0.3 GeV 2 at the LHC. We investigate the effects of the magnetic field on B 0 and D 0 mesons, focusing on the changes of the energy levels and of the mass of the bound states.

  8. Three Dimensional Double Layers in Magnetized Plasmas

    DEFF Research Database (Denmark)

    Jovanovic, D.; Lynov, Jens-Peter; Michelsen, Poul

    1982-01-01

    Experimental results are presented which demonstrate the formation of fully three dimensional double layers in a magnetized plasma. The measurements are performed in a magnetized stationary plasma column with radius 1.5 cm. Double layers are produced by introducing an electron beam with radius 0.......4 cm along the magnetic field from one end of the column. The voltage drop across the double layer is found to be determined by the energy of the incoming electron beam. In general we find that the width of the double layer along the external magnetic field is determined by plasma density and beam...

  9. Nonlinear Electron Waves in Strongly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens

    1980-01-01

    Weakly nonlinear dispersive electron waves in strongly magnetized plasma are considered. A modified nonlinear Schrodinger equation is derived taking into account the effect of particles resonating with the group velocity of the waves (nonlinear Landau damping). The possibility of including the ion...

  10. Weak and strong nonlinearities in magnetic bearings

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav

    2004-01-01

    Roč. 39, č. 7 (2004), s. 779-795 ISSN 0094-114X R&D Projects: GA ČR GA101/00/1471; GA AV ČR IBS2076301 Institutional research plan: CEZ:AV0Z2076919 Keywords : weak nonlinearitiy * strong nonlinearity * magnetics bearings Subject RIV: BI - Acoustics Impact factor: 0.605, year: 2004

  11. Mechanics of magnetic fluid column in strong magnetic fields

    International Nuclear Information System (INIS)

    Polunin, V.M.; Ryapolov, P.A.; Platonov, V.B.

    2017-01-01

    Elastic-and magnetic properties of magnetic fluid confined by ponderomotive force in a tube fixed in horizontal position are considered. The system is placed in a strong magnetic field under the influence of external static and dynamic perturbations. An experimental setup has been developed. A theoretical basis of the processes of magnetic colloid elastic deformation has been proposed. The values of the static ponderomotive elasticity coefficient and the elasticity coefficient under dynamic action are experimentally determined. The calculations of the saturation magnetization for two magnetic fluid samples, carried out according to the equation containing the dynamic elasticity coefficient, are in good agreement with the experimental magnetization curve. The described method is of interest when studying magnetophoresis and aggregation of nanoparticles in magnetic colloids.

  12. Neutrino oscillations in strong magnetic fields

    International Nuclear Information System (INIS)

    Likhachev, G.G.; Studenikin, A.I.

    1994-07-01

    Neutrino conversion processes between two neutrino species and the corresponding oscillations induced by strong magnetic fields are considered. The value of the critical strength of magnetic field B cr as a function of characteristics of neutrinos in vacuum (Δm 2 ν , mixing angle θ), effective particle density of matter n eff , neutrino (transition) magnetic moment μ-tilde and energy E is introduced. It is shown that the neutrino conversion and oscillations effects induced by magnetic fields B ≥ B cr are important and may result in the depletion of the initial type of ν's in the bunch. A possible increase of these effects in the case when neutrinos pass through a sudden decrease of density of matter (''cross-boundary effect'') and applications to neutrinos from neutron stars and supernova are discussed. (author). 25 refs

  13. Frictional Coulomb drag in strong magnetic fields

    DEFF Research Database (Denmark)

    Bønsager, Martin Christian; Flensberg, Karsten; Hu, Ben Yu-Kuang

    1997-01-01

    A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21) is eval......A treatment of frictional Coulomb drag between two two-dimensional electron layers in a strong perpendicular magnetic field, within the independent electron picture, is presented. Assuming fully resolved Landau levels, the linear response theory expression for the transresistivity rho(21......) is evaluated using diagrammatic techniques. The transresistivity is given by an integral over energy and momentum transfer weighted by the product of the screened interlayer interaction and the phase space for scattering events. We demonstrate, by a numerical analysis of the transresistivity, that for well...

  14. Magnetic properties of strongly asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Kutschera, M.; Wojcik, W.

    1988-01-01

    We investigate stability of neutron matter containing a small proton admixture with respect to spin fluctuations. We establish conditions under which strongly asymmetric nuclear matter could acquire a permanent magnetization. It is shown that if the protons are localized, the system becomes unstable to spin fluctuations for arbitrarily weak proton-neutron spin interactions. For non-localized protons there exists a threshold value of the spin interaction above which the system can develop a spontaneous polarization. 12 refs., 2 figs. (author)

  15. Super-strong Magnetic Field in Sunspots

    Science.gov (United States)

    Okamoto, Takenori J.; Sakurai, Takashi

    2018-01-01

    Sunspots are the most notable structure on the solar surface with strong magnetic fields. The field is generally strongest in a dark area (umbra), but sometimes stronger fields are found in non-dark regions, such as a penumbra and a light bridge. The formation mechanism of such strong fields outside umbrae is still puzzling. Here we report clear evidence of the magnetic field of 6250 G, which is the strongest field among Stokes I profiles with clear Zeeman splitting ever observed on the Sun. The field was almost parallel to the solar surface and located in a bright region sandwiched by two opposite-polarity umbrae. Using a time series of spectral data sets, we discuss the formation process of the super-strong field and suggest that this strong field region was generated as a result of compression of one umbra pushed by the horizontal flow from the other umbra, such as the subduction of the Earth’s crust in plate tectonics.

  16. Strongly Interacting Matter in Magnetic Field

    Science.gov (United States)

    Mao, Shijun; Wu, Youjia; Zhuang, Pengfei

    Inverse magnetic catalysis effect on the chiral phase transition is investigated in the frame of SU(2) NJL model with Pauli-Villars regularization scheme. We consider two scenarios, the chiral chemical potential μ5 caused by sphalerons and magnetic inhibition of mesons π0. With different chiral chemical potential, we always obtain magnetic catalysis in the mean field calculation, due to the enhancement of Fermi surface of the pairing fermions by μ5. On the other hand, when going beyond the mean field approximation by including the feed-down from mesons to quarks, the competition between the magnetic catalysis effect of quarks and magnetic inhibition effect of mesons leads to the transition from inverse magnetic catalysis to delayed magnetic catalysis with increasing magnetic field.

  17. Mechanism and Simulation of Generating Pulsed Strong Magnetic Field

    Science.gov (United States)

    Yang, Xian-Jun; Wang, Shuai-Chuang; Deng, Ai-Dong; Gu, Zhuo-Wei; Luo, Hao

    2014-10-01

    A strong magnetic field (over 1000 T) was recently experimentally produced at the Academy of Engineering Physics in China. The theoretical methods, which include a simple model and MHD code, are discussed to investigate the physical mechanism and dynamics of generating the strong magnetic field. The analysis and simulation results show that nonlinear magnetic diffusion contributes less as compared to the linear magnetic diffusion. This indicates that the compressible hydrodynamic effect and solid imploding compression may have a large influence on strong magnetic field generation.

  18. Effective magnetic moment of neutrinos in strong magnetic fields

    CERN Document Server

    Pérez, A; Masood, S S; Gaitan, R; Rodríguez, S

    2002-01-01

    In this paper we compute the effective magnetic moment of neutrinos propagating in dense high magnetized medium. Taking typical values of magnetic field and densities of astrophysical objects (such as the cores of supernovae and neutron stars) we obtain an effective type of dipole magnetic moment in agreement with astrophysical and cosmological bounds. (Author)

  19. Activity of Strongly Magnetized Neutron Stars

    Science.gov (United States)

    Beloborodov, Andrei

    This proposal is the continuation of a previous 3-year project that focused on modeling the nonthermal emission from magnetars and pulsars and testing the models against new observations, in particular by NuSTAR. The proposed project develops in two directions: (1) First-principle simulations of the magnetospheric electron-positron discharge using our code APERTURE (based on the particle-in-cell method), which is specifically designed for this purpose. Its performance is demonstrated by the first application to rotation-powered pulsars, and it can significantly advance our understanding of the magnetospheric activity of magnetars and pulsars. Our simulations involve a detailed implementation of radiative processes, tracking the emission and propagation of gammarays and production of electron-positron pairs. The results will provide new theoretical foundation for interpreting emission from the twisted magnetospheres of neutron stars. They will clarify, in particular, the radiative mechanism of magnetar bursts and persistent emission. (2) Investigation of magnetic field evolution inside neutron stars, which is ultimately responsible for driving the magnetospheric activity of magnetars and their surface heating. Our recent results suggest two novel phenomena in the solid crust of an active magnetar: thermoplastic waves and Hall-mediated avalanches. We propose to investigate scenarios for the global magnetic field evolution in the core and the crust, and its observables including (a) twisting of the external magnetosphere and the resulting nonthermal activity, (b) subsurface heating, and (c) sudden changes of the rotation rate. We will use our models and the rich accumulated data to disentangle the key dynamic processes inside magnetars. This analysis can constrain the magnetic fields hidden inside magnetars, the state of their core matter and its possible superfluidity.

  20. Strong permanent magnet-assisted electromagnetic undulator

    Science.gov (United States)

    Halbach, Klaus

    1988-01-01

    This invention discloses an improved undulator comprising a plurality of electromagnet poles located along opposite sides of a particle beam axis with alternate north and south poles on each side of the beam to cause the beam to wiggle or undulate as it travels generally along the beam axis and permanent magnets spaced adjacent the electromagnetic poles on each side of the axis of said particle beam in an orientation sufficient to reduce the saturation of the electromagnet poles whereby the field strength of the electromagnet poles can be increased beyond the normal saturation levels of the electromagnetic poles.

  1. Enhanced thermal photon and dilepton production in strongly coupled = 4 SYM plasma in strong magnetic field

    Science.gov (United States)

    Mamo, Kiminad A.

    2013-08-01

    We calculate the DC conductivity tensor of strongly coupled = 4 super-Yang-Mills (SYM) plasma in a presence of a strong external magnetic field B ≫ T 2 by using its gravity dual and employing both the RG flow approach and membrane paradigm which give the same results. We find that, since the magnetic field B induces anisotropy in the plasma, different components of the DC conductivity tensor have different magnitudes depending on whether its components are in the direction of the magnetic field B. In particular, we find that a component of the DC conductivity tensor in the direction of the magnetic field B increases linearly with B while the other components (which are not in the direction of the magnetic field B) are independent of it. These results are consistent with the lattice computations of the DC conductivity tensor of the QCD plasma in an external magnetic field B. Using the DC conductivity tensor, we calculate the soft or low-frequency thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in the presence of the strong external magnetic field B ≫ T 2. We find that the strong magnetic field B enhances both the thermal photon and dilepton production rates of the strongly coupled = 4 SYM plasma in a qualitative agreement with the experimentally observed enhancements at the heavy-ion collision experiments.

  2. Electrostatic turbulence in strongly magnetized plasmas

    International Nuclear Information System (INIS)

    Nielsen, A.H.

    1993-01-01

    Turbulence in plasmas has been investigated experimentally and numerically. On the experimental side the turbulent nature of the Kelvin-Helmholtz instability has been studied in a single-ended Q-machine. The development of coherent structures in the background of the turbulent flow has been demonstrated and the capability of structures of transporting plasma across the magnetic field-lines is explained in detail. The numerical investigations are divided into two parts: Numerical simulations of the dynamics from the Q-machine experiments using spectral methods to solve the two-dimensional Navier-Stokes equations in a cylindrical geometry. A numerical study of the Eulerian-Lagrangian transformation in a two-dimensional flow. Here the flow is made up by a large number of structures, where each individual structure is convected by the superposed flow field of all the others. (au) (33 ills., 67 refs.)

  3. Operating a magnetic nozzle helicon thruster with strong magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Kazunori, E-mail: kazunori@ecei.tohoku.ac.jp; Komuro, Atsushi; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2016-03-15

    A pulsed axial magnetic field up to ∼2.8 kG is applied to a 26-mm-inner-diameter helicon plasma thruster immersed in a vacuum chamber, and the thrust is measured using a pendulum target. The pendulum is located 30-cm-downstream of the thruster, and the thruster rf power and argon flow rate are fixed at 1 kW and 70 sccm (which gives a chamber pressure of 0.7 mTorr). The imparted thrust increases as the applied magnetic field is increased and saturates at a maximum value of ∼9.5 mN for magnetic field above ∼2 kG. At the maximum magnetic field, it is demonstrated that the normalized plasma density, and the ion flow energy in the magnetic nozzle, agree within ∼50% and of 10%, respectively, with a one-dimensional model that ignores radial losses from the nozzle. This magnetic nozzle model is combined with a simple global model of the thruster source that incorporates an artificially controlled factor α, to account for radial plasma losses to the walls, where α = 0 and 1 correspond to zero losses and no magnetic field, respectively. Comparison between the experiments and the model implies that the radial losses in the thruster source are experimentally reduced by the applied magnetic field to about 10% of that obtained from the no magnetic field model.

  4. Electromagnetic modes in cold magnetized strongly coupled plasmas

    OpenAIRE

    Tkachenko, I. M.; Ortner, J.; Rylyuk, V. M.

    1999-01-01

    The spectrum of electromagnetic waves propagating in a strongly coupled magnetized fully ionized hydrogen plasma is found. The ion motion and damping being neglected, the influence of the Coulomb coupling on the electromagnetic spectrum is analyzed.

  5. Spectral confinement and current for atoms in strong magnetic fields

    DEFF Research Database (Denmark)

    Fournais, Søren

    2007-01-01

    e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B<3......e study confinement of the ground state of atoms in strong magnetic fields to different subspaces related to the lowest Landau band. Using the results on confinement we can calculate the quantum current in the entire semiclassical region B

  6. Transport Theory for Plasmas that are Strongly Magnetized and Strongly Coupled

    Science.gov (United States)

    Baalrud, Scott; Daligault, Jerome

    2016-10-01

    Plasmas with components that are magnetized, strongly coupled, or both arise in a variety of frontier plasma physics experiments including magnetized dusty plasmas, nonneutral plasmas, magnetized ICF concepts, as well as from self-generated fields in ICF. Here, a species is considered strongly magnetized if the gyroradius is smaller than the spatial scale over which Coulomb interactions occur. A theory for transport properties is described that treats a wide range of both coupling and magnetization strengths. The approach is based on an extension of the recent effective potential transport theory to include a strong magnetic field. The underlying kinetic theory is based on an extension of the Boltzmann equation to include a strong magnetic field in the dynamics of binary scattering events. Corresponding magnetohydrodynamic equations are derived by solving the kinetic equation using a Chapman-Enskog like spectral method. Results are compared with classical molecular dynamics simulations of self-diffusion of the one component plasmas, and with simulations of parallel to perpendicular temperature equilibration of an initially anisotropic distribution. This material is based upon work supported by AFOSR Award FA9550-16-1-0221 and DOE OFES Award DE-SC0016159.

  7. Radial oscillations of neutron stars in strong magnetic fields

    Indian Academy of Sciences (India)

    The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to ...

  8. Radial oscillations of neutron stars in strong magnetic fields

    Indian Academy of Sciences (India)

    Abstract. The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and ...

  9. Magnetic separation technique for environmental water purification by strong magnetic field generator loading HTS bulk magnets

    International Nuclear Information System (INIS)

    Oka, T.; Tanaka, K.; Kimura, T.; Mimura, D.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Yokoyama, K.; Yamaguchi, M.

    2010-01-01

    The magnetic separation technique in combination with high temperature superconducting bulk magnets has been investigated to purify the ground water which has been used in the coolant system for the incinerator furnace to cool the burning gas. The experiment has been operated by means of the newly-built alternating channel type magnetic separating device. The separation ratios of ferromagnetic flocks including fine magnetite powder have been estimated by means of the high gradient magnetic separation method with small iron balls filled in the water channels. As the magnetic force acting on the magnetic particle is given by the product of a magnetization of the material and a gradient of magnetic field, and as the ferromagnetic stainless steel balls yield the steep gradient of magnetic field around them in a strong magnetic field, the system has exhibited a quite excellent performance with respect to the separation ratios. The separation ratios of the flocks which contain the magnetite powder with the values more than 50 ppm have remained over 80% for under the flow rates less than 5 L/min.

  10. Magnetic separation technique for environmental water purification by strong magnetic field generator loading HTS bulk magnets

    Science.gov (United States)

    Oka, T.; Tanaka, K.; Kimura, T.; Mimura, D.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Yokoyama, K.; Yamaguchi, M.

    2010-11-01

    The magnetic separation technique in combination with high temperature superconducting bulk magnets has been investigated to purify the ground water which has been used in the coolant system for the incinerator furnace to cool the burning gas. The experiment has been operated by means of the newly-built alternating channel type magnetic separating device. The separation ratios of ferromagnetic flocks including fine magnetite powder have been estimated by means of the high gradient magnetic separation method with small iron balls filled in the water channels. As the magnetic force acting on the magnetic particle is given by the product of a magnetization of the material and a gradient of magnetic field, and as the ferromagnetic stainless steel balls yield the steep gradient of magnetic field around them in a strong magnetic field, the system has exhibited a quite excellent performance with respect to the separation ratios. The separation ratios of the flocks which contain the magnetite powder with the values more than 50 ppm have remained over 80% for under the flow rates less than 5 L/min.

  11. LDA+DMFT Approach to Magnetocrystalline Anisotropy of Strong Magnets

    Directory of Open Access Journals (Sweden)

    Jian-Xin Zhu

    2014-05-01

    Full Text Available The new challenges posed by the need of finding strong rare-earth-free magnets demand methods that can predict magnetization and magnetocrystalline anisotropy energy (MAE. We argue that correlated electron effects, which are normally underestimated in band-structure calculations, play a crucial role in the development of the orbital component of the magnetic moments. Because magnetic anisotropy arises from this orbital component, the ability to include correlation effects has profound consequences on our predictive power of the MAE of strong magnets. Here, we show that incorporating the local effects of electronic correlations with dynamical mean-field theory provides reliable estimates of the orbital moment, the mass enhancement, and the MAE of YCo_{5}.

  12. THE EXTRAORDINARY COMPLEX MAGNETIC FIELD OF THE HELIUM-STRONG STAR HD 37776

    International Nuclear Information System (INIS)

    Kochukhov, Oleg; Lundin, Andreas; Romanyuk, Iosif; Kudryavtsev, Dmitry

    2011-01-01

    The early-type chemically peculiar stars often show strong magnetic fields on their surfaces. These magnetic topologies are organized on large scales and are believed to be close to an oblique dipole for most of the stars. In a striking exception to this general trend, the helium-strong star HD 37776 shows an extraordinary double-wave rotational modulation of the longitudinal magnetic field measurements, indicating a topologically complex and, possibly, record-strong magnetic field. Here we present a new investigation of the magnetic field structure of HD 37776, using both simple geometrical interpretation of the longitudinal field curve and detailed modeling of the time-resolved circular polarization line profiles with the help of a magnetic Doppler imaging technique. We derive a model of the magnetic field structure of HD 37776, which reconciles for the first time all magnetic observations available for this star. We find that the local surface field strength does not exceed ∼30 kG, while the overall field topology of HD 37776 is dominated by a non-axisymmetric component and represents by far the most complex magnetic field configuration found among early-type stars.

  13. Ion Motion in a Plasma Interacting with Strong Magnetic Fields

    International Nuclear Information System (INIS)

    Weingarten, A.; Grabowski, C.; Chakrabarti, N.; Maron, Y.; Fruchtmant, A.

    1999-01-01

    The interaction of a plasma with strong magnetic fields takes place in many laboratory experiments and astrophysical plasmas. Applying a strong magnetic field to the plasma may result in plasma displacement, magnetization, or the formation of instabilities. Important phenomena in plasma, such as the energy transport and the momentum balance, take a different form in each case. We study this interaction in a plasma that carries a short-duration (80-ns) current pulse, generating a magnetic field of up to 17 kG. The evolution of the magnetic field, plasma density, ion velocities, and electric fields are determined before and during the current pulse. The dependence of the plasma limiting current on the plasma density and composition are studied and compared to theoretical models based on the different phenomena. When the plasma collisionality is low, three typical velocities should be taken into consideration: the proton and heavier-ion Alfven velocities (v A p and v A h , respectively) and the EMHD magnetic-field penetration velocity into the plasma (v EMHD ). If both Alfven velocities are larger than v EMHD the plasma is pushed ahead of the magnetic piston and the magnetic field energy is dissipated into ion kinetic energy. If v EMHD is the largest of three velocities, the plasma become magnetized and the ions acquire a small axial momentum only. Different ion species may drift in different directions along the current lines. In this case, the magnetic field energy is probably dissipated into electron thermal energy. When vs > V EMHD > vi, as in the case of one of our experiments, ion mass separation occurs. The protons are pushed ahead of the piston while the heavier-ions become magnetized. Since the plasma electrons are unmagnetized they cannot cross the piston, and the heavy ions are probably charge-neutralized by electrons originating from the cathode that are 'born' magnetized

  14. Vortex-lattice states at strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Akera, H.; MacDonald, A.H.; Girvin, S.M. (Department of Physics, Indiana University, Bloomington, Indiana (USA)); Norman, M.R. (Materials Science Division, Argonne National Laboratory, Argonne, Illinois (USA))

    1991-10-21

    At strong magnetic fields, Landau quantization invalidates the semiclassical approximations which underly the Ginzburg-Landau (GL) theory of the mixed states of type-II superconductors. We have solved the {ital microscopic} mean-field equations for the case of a two-dimensional electron system in the strong magnetic-field limit. For delta-function attractive interactions there exist {ital n}+1 pairing channels in the {ital n}th Landau level. For {ital n}{gt}0, two channels share the maximum {ital T}{sub {ital c}}, and the order parameter differs markedly from expectations based on GL theory.

  15. Confinining properties of QCD in strong magnetic backgrounds

    Directory of Open Access Journals (Sweden)

    Bonati Claudio

    2017-01-01

    Full Text Available Strong magnetic backgrounds are known to modify QCD properties at a nonperturbative level. We discuss recent lattice results, obtained for Nf = 2 + 1 QCD with physical quark masses, concerning in particular the modifications and the anisotropies induced at the level of the static quark-antiquark potential, both at zero and finite temperature.

  16. Theory of Spin Waves in Strongly Anisotropic Magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Cooke, J. F.

    1976-01-01

    A new infinite-order perturbation approach to the theory of spin waves in strongly anisotropic magnets is introduced. The system is transformed into one with effective two-ion anisotropy and considerably reduced ground-state corrections. A general expression for the spin-wave energy, valid to any...

  17. Resonances of the helium atom in a strong magnetic field

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Al-Hujaj, Omar-Alexander; Schmelcher, Peter

    2007-01-01

    We present an investigation of the resonances of a doubly excited helium atom in a strong magnetic field covering the regime B=0–100  a.u. A full-interaction approach which is based on an anisotropic Gaussian basis set of one-particle functions being nonlinearly optimized for each field strength...

  18. Observation of strong magnetic effects in visible-infrared sum frequency generation from magnetic structures

    NARCIS (Netherlands)

    Kirilyuk, A.; Knippels, G.M.H.; van der Meer, A. F. G.; Renard, S.; Rasing, T.; Heskamp, I. R.; Lodder, J. C.

    2000-01-01

    We have observed very strong magnetization-induced changes of the infrared-visible sum-frequency generation (SFG) intensity from thin magnetic films using a free electron laser as a tunable infrared source. With the help of a magnetic grating a clear resonance is observed due to the excitation of

  19. Neutrino-electron processes in a strongly magnetized thermal plasma

    CERN Document Server

    Hardy, S J; Hardy, Stephen J.; Thoma, Markus H.

    2001-01-01

    We present a new method of calculating the rate of neutrino-electron interactions in a strong magnetic field based on finite temperature field theory. Using this method, in which the effect of the magnetic field on the electron states is taken into account exactly, we calculate the rates of all of the lowest order neutrino-electron interactions in a plasma. As an example of the use of this technique, we explicitly calculate the rate at which neutrinos and antineutrinos annihilate in a highly magnetized plasma, and compare that to the rate in an unmagnetized plasma. The most important channel for energy deposition is the gyromagnetic absorption of a neutrino-antineutrino pair on an electron or positron in the plasma ($\

  20. Magnetic properties of metallic impurities with strongly correlated electrons

    Czech Academy of Sciences Publication Activity Database

    Janiš, Václav; Ringel, Matouš

    2009-01-01

    Roč. 115, č. 1 (2009), s. 30-35 ISSN 0587-4246 R&D Projects: GA ČR GA202/07/0644 Institutional research plan: CEZ:AV0Z10100520 Keywords : And erson impurity * strong electron correlations * spin-polarized solution * three-channel parquet equations * magnetic field Subject RIV: BE - Theoretical Physics Impact factor: 0.433, year: 2009 http://przyrbwn.icm.edu.pl/APP/ABSTR/115/a115-1-5.html

  1. Semicalssical quantization of interacting anyons in a strong magnetic field

    International Nuclear Information System (INIS)

    Levit, S.; Sivan, N.

    1992-01-01

    We represent a semiclassical theory of charged interacting anyons in strong magnetic fields. We apply this theory to a number of few anyons systems including two interacting anyons in the presence of an impurity and three interacting anyons. We discuss the dependence of their energy levels on the statistical parameter and find regions in which this dependence follows very different patterns. The semiclassical arguments allow to correlate these patterns with the change in the character of the classical motion of the system. (author)

  2. Double-impulse magnetic focusing of launched cold atoms

    Science.gov (United States)

    Arnold, Aidan S.; Pritchard, Matthew J.; Smith, David A.; Hughes, Ifan G.

    2006-04-01

    We have theoretically investigated three-dimensional focusing of a launched cloud of cold atoms using a pair of magnetic lens pulses (the alternate-gradient method). Individual lenses focus radially and defocus axially or vice versa. The performance of the two possible pulse sequences are compared and found to be ideal for loading both 'pancake' and 'sausage' shaped magnetic/optical microtraps. It is shown that focusing aberrations are considerably smaller for double-impulse magnetic lenses compared to single-impulse magnetic lenses. An analysis of clouds focused by the double-impulse technique is presented.

  3. Strongly Coupled Magnetic and Electronic Transitions in Multivalent Strontium Cobaltites.

    Science.gov (United States)

    Lee, J H; Choi, Woo Seok; Jeen, H; Lee, H-J; Seo, J H; Nam, J; Yeom, M S; Lee, H N

    2017-11-22

    The topotactic phase transition in SrCoO x (x = 2.5-3.0) makes it possible to reversibly transit between the two distinct phases, i.e. the brownmillerite SrCoO 2.5 that is a room-temperature antiferromagnetic insulator (AFM-I) and the perovskite SrCoO 3 that is a ferromagnetic metal (FM-M), owing to their multiple valence states. For the intermediate x values, the two distinct phases are expected to strongly compete with each other. With oxidation of SrCoO 2.5 , however, it has been conjectured that the magnetic transition is decoupled to the electronic phase transition, i.e., the AFM-to-FM transition occurs before the insulator-to-metal transition (IMT), which is still controversial. Here, we bridge the gap between the two-phase transitions by density-functional theory calculations combined with optical spectroscopy. We confirm that the IMT actually occurs concomitantly with the FM transition near the oxygen content x = 2.75. Strong charge-spin coupling drives the concurrent IMT and AFM-to-FM transition, which fosters the near room-T magnetic transition characteristic. Ultimately, our study demonstrates that SrCoO x is an intriguingly rare candidate for inducing coupled magnetic and electronic transition via fast and reversible redox reactions.

  4. Helium atoms and molecules in strong magnetic fields

    Science.gov (United States)

    Mori, K.

    Recent theoretical studies have shown that the neutron star surface may be composed of helium or heavier elements as hydrogen may be quickly depleted by diffuse nuclear burning Chang Bildsten However while Hydrogen atmospheres have been studied in great details atomic data for helium is available only for He ion Pavlov Bezchastnov 2005 We performed Hartree-Fock type calculation for Helium atom and molecules and computed their binding ionization and dissociation energies in strong magnetic fields B sim10 12 -- 10 15 G We will present ionization balance of Helium atmospheres at typical magnetic field strengths and temperatures to radio-quiet neutron stars and AXPs We will also discuss several implications of helium atmosphere to X-ray data of isolated neutron stars focusing on the detected spectral features

  5. Electric-Field-Induced Superconductivity Detected by Magnetization Measurements of an Electric-Double-Layer Capacitor

    NARCIS (Netherlands)

    Kasahara, Yuichi; Nishijima, Takahiro; Sato, Tatsuya; Takeuchi, Yuki; Ye, Jianting; Yuan, Hongtao; Shimotani, Hidekazu; Iwasa, Yoshihiro

    We report evidence for superconductivity induced by the application of strong electric fields onto the surface of a band insulator, ZrNCl, provided by the observation of a shielding diamagnetic signal. We introduced an electric-double-layer capacitor configuration and in situ magnetization

  6. Magnetoresistance and magnetic properties of the double perovskites

    International Nuclear Information System (INIS)

    Philipp, J.B.; Majewski, P.; Resinger, D.; Gepraegs, S; Opel, M.; Reb, A.; Alff, L.; Gross, R.

    2004-01-01

    The magnetic double perovskite materials of composition A 2 BB'O 6 with A an alkaline earth ion and B and B' a magnetic and non-magnetic transition metal or lanthanide ions, respectively, have attracted considerable attention due to their interesting magnetic properties ranging from antiferromagnetism to geometrically frustrated spin systems and ferromagnetism. With respect to application in spin electronics, the ferromagnetic double perovskites with BB' = CrW, CrRe, FeMo or FeRe and A = Ca, Ba, Sr are highly interesting due to their in most cases high Curie temperatures well above room temperature and their half-magnetic behaviour. Here, we summarize the structural, magnetotransport, magnetic and optical properties of the ferromagnetic double perovskites and discuss the underlying physics. In particular, we discuss the impact of the steric effects resulting in a distorted perovskite structure, doping effects obtained by a partial replacing of the divalent alkaline earth ions on the A site by a trivalent lanthanide as well as B/B' cationic disorder on the Curie temperature T C , the saturation magnetization and the magnetotransport properties. Our results support the presence of a kinetic energy driven mechanism in the ferromagnetic double perovskites, where ferromagnetism is stabilised by a hybridization of states of the non-magnetic B'- site positioned in between the high spin B-sites. (author)

  7. On the possibility of excitonic magnetism in Ir double perovskites

    Czech Academy of Sciences Publication Activity Database

    Pajskr, K.; Novák, Pavel; Pokorný, Vladislav; Kolorenč, Jindřich; Arita, R.; Kuneš, Jan

    2016-01-01

    Roč. 93, č. 3 (2016), 1-6, č. článku 035129. ISSN 1098-0121 R&D Projects: GA ČR GA13-25251S Institutional support: RVO:68378271 Keywords : spin-orbit coupling * double perovskite * excitonic magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  8. Temperature dependence of shot noise in double barrier magnetic tunnel junctions

    Science.gov (United States)

    Niu, Jiasen; Liu, Liang; Feng, J. F.; Han, X. F.; Coey, J. M. D.; Zhang, X.-G.; Wei, Jian

    2018-03-01

    Shot noise reveals spin dependent transport properties in a magnetic tunnel junction. We report measurement of shot noise in CoFeB/MgO/CoFeB/MgO/CoFeB double barrier magnetic tunnel junctions, which shows a strong temperature dependence. The Fano factor used to characterize shot noise increases with decreasing temperature. A sequential tunneling model can be used to account for these results, in which a larger Fano factor results from larger spin relaxation length at lower temperatures.

  9. Confinement and αs in a strong magnetic field

    Directory of Open Access Journals (Sweden)

    Yu.A. Simonov

    2015-07-01

    Full Text Available Hadron decay widths are shown to increase in strong magnetic fields as Γ(eB∼eBκΓ(0. The same mechanism is shown to be present in the production of the sea quark pair inside the confining string, which decreases the string tension with the growing eB parallel to the string. On the other hand, the average energy of the qq¯ holes in the string world sheet increases, when the direction of B is perpendicular to the sheet. These two effects stipulate the spectacular picture of the B dependent confinement and αs, discovered on the lattice.

  10. Bound states in strongly correlated magnetic and electronic systems

    International Nuclear Information System (INIS)

    Trebst, S.

    2002-02-01

    A novel strong coupling expansion method to calculate two-particle spectra of quantum lattice models is developed. The technique can be used to study bosonic and fermionic models and in principle it can be applied to systems in any dimension. A number of strongly correlated magnetic and electronic systems are examined including the two-leg spin-half Heisenberg ladder, the dimerized Heisenberg chain with a frustrating next-nearest neighbor interaction, coupled Heisenberg ladders, and the one-dimensional Kondo lattice model. In the various models distinct bound states are found below the two-particle continuum. Quantitative calculations of the dispersion, coherence length and binding energy of these bound states are used to describe spectroscopic experiments on (Ca,La) 14 Cu 24 O 41 and NaV 2 O 5 . (orig.)

  11. Magnetic and transport properties of single and double perpendicular magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Cuchet, Lea

    2015-01-01

    Due to their advantageous properties in terms of data retention, storage density and critical current density for Spin Transfer Torque (STT) switching, the magnetic tunnel junctions with perpendicular anisotropy have become predominant in the developments for MRAM applications. The aim of this thesis is to improve the anisotropy and transport properties of such structures and to realize even more complex stacks such as perpendicular double junctions. Studies on the magnetic properties and Tunnel Magnetoresistance (TMR) measurements showed that to optimize the performances of the junctions, all the thicknesses of the different layers constituting the stack have to be adapted. To guaranty both a large TMR as well a strong perpendicular anisotropy, compromises are most of the time needed. Studies as a function of magnetic thickness enabled to extract the saturation magnetization, the critical thickness and the magnetic dead layer thickness both in the bottom reference and the top storage layer in structures capped with Ta. This type of junction could be tested electrically after patterning the sample into nano-pillars. Knowing that perpendicular anisotropy mostly arises at the metal/oxide interface, the Ta capping layer was replaced by a MgO one, leading to a huge increase in the anisotropy of the free layer. A second top reference was then added on such a stack to create functional perpendicular double junctions. CoFeB/insertion/CoFeB synthetic antiferromagnetic storage layers could be developed and were proved to be stable enough to replace the standard Co/Pt-based reference layers. (author) [fr

  12. Quark-gluon plasma in strong magnetic fields

    International Nuclear Information System (INIS)

    Kalaydzhyan, Tigran

    2013-04-01

    One of the fundamental problems in subatomic physics is the determination of properties of matter at extreme temperatures, densities and electromagnetic fields. The modern ultrarelativistic heavy-ion experiments are able to study such states (the quark-gluon plasma) and indicate that the physics at extreme conditions differs drastically from what is known from the conventional observations. Also the theoretical methods developed mostly within the perturbative framework face various conceptual problems and need to be replaced by a nonperturbative approach. In this thesis we study the physics of the strongly-coupled quark-gluon plasma in external magnetic fields as well as general electromagnetic and topological properties of the QCD and QCD-like systems. We develop and apply various nonperturbative techniques, based on e.g. gauge-gravity correspondence, lattice QCD simulations, relativistic hydrodynamics and condensed-matter-inspired models.

  13. Strong enhancement of magnetic anisotropy energy in alloyed nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Negulyaev, Nikolay; Niebergall, Larissa; Stepanyuk, Valeri [Max-Planck-Institut fuer Mikrostrukturphysik, D-06120 Halle (Germany); Juarez Reyes, Lucila; Pastor, Gustavo [Institut fuer Theoretische Physik, Universitaet Kassel, D-34132 Kassel (Germany); Dorantes-Davila, Jesus [Instituto de Fisica, Universidad Autonoma de San Luis Potosi, 78000 San Luis Potosi (Mexico)

    2011-07-01

    One-dimensional atomic structures (monatomic wires and chains) are believed to be likely candidates for creation of nanostructures with large atomic orbital moments and hence with giant magnetic anisotropy energy (MAE) per atom. We investigate the possibility of tuning the MAE of 3d transition metal monowires alloyed with 5d elements (Ir, Pt). Our ab initio studies give clear evidence that in mixed 3d-5d atomic wires MAE is one and even two orders of magnitude more than in pure wires constructed of the corresponding 5d and 3d elements, respectively. Mechanisms responsible for the formation of such a strong MAE are revealed. The interplay between the structure of a monowire and its MAE is demonstrated. The contribution of both types of species (3d and 5d) into the MAE is discussed.

  14. Quark-gluon plasma in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Kalaydzhyan, Tigran

    2013-04-15

    One of the fundamental problems in subatomic physics is the determination of properties of matter at extreme temperatures, densities and electromagnetic fields. The modern ultrarelativistic heavy-ion experiments are able to study such states (the quark-gluon plasma) and indicate that the physics at extreme conditions differs drastically from what is known from the conventional observations. Also the theoretical methods developed mostly within the perturbative framework face various conceptual problems and need to be replaced by a nonperturbative approach. In this thesis we study the physics of the strongly-coupled quark-gluon plasma in external magnetic fields as well as general electromagnetic and topological properties of the QCD and QCD-like systems. We develop and apply various nonperturbative techniques, based on e.g. gauge-gravity correspondence, lattice QCD simulations, relativistic hydrodynamics and condensed-matter-inspired models.

  15. Anomalous electrodynamics of neutral pion matter in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Brauner, Tomáš [Department of Mathematics and Natural Sciences, University of Stavanger,N-4036 Stavanger (Norway); Kadam, Saurabh V. [Indian Institute of Science Education and Research (IISER),Pune 411008 (India)

    2017-03-03

    The ground state of quantum chromodynamics in sufficiently strong external magnetic fields and at moderate baryon chemical potential is a chiral soliton lattice (CSL) of neutral pions https://arxiv.org/abs/1609.05213. We investigate the interplay between the CSL structure and dynamical electromagnetic fields. Our main result is that in presence of the CSL background, the two physical photon polarizations and the neutral pion mix, giving rise to two gapped excitations and one gapless mode with a nonrelativistic dispersion relation. The nature of this mode depends on the direction of its propagation, interpolating between a circularly polarized electromagnetic wave https://www.doi.org/10.1103/PhysRevD.93.085036 and a neutral pion surface wave, which in turn arises from the spontaneously broken translation invariance. Quite remarkably, there is a neutral-pion-like mode that remains gapped even in the chiral limit, in seeming contradiction to the Goldstone theorem. Finally, we have a first look at the effect of thermal fluctuations of the CSL, showing that even the soft nonrelativistic excitation does not lead to the Landau-Peierls instability. However, it leads to an anomalous contribution to pressure that scales with temperature and magnetic field as T{sup 5/2}(B/f{sub π}){sup 3/2}.

  16. Resonant tunnel magnetoresistance in a double magnetic tunnel junction

    KAUST Repository

    Useinov, Arthur

    2011-08-09

    We present quasi-classical approach to calculate a spin-dependent current and tunnel magnetoresistance (TMR) in double magnetic tunnel junctions (DMTJ) FML/I/FMW/I/FMR, where the magnetization of the middle ferromagnetic metal layer FMW can be aligned parallel or antiparallel with respect to the fixed magnetizations of the left FML and right FMR ferromagnetic electrodes. The transmission coefficients for components of the spin-dependent current, and TMR are calculated as a function of the applied voltage. As a result, we found a high resonant TMR. Thus, DMTJ can serve as highly effective magnetic nanosensor for biological applications, or as magnetic memory cells by switching the magnetization of the inner ferromagnetic layer FMW.© Springer Science+Business Media, LLC 2011.

  17. Cobalt double-ring and double-dot structures: Magnetic properties

    International Nuclear Information System (INIS)

    López-Urías, F.; Torres-Heredia, J.J.; Muñoz-Sandoval, E.

    2016-01-01

    The magnetization reversal mechanism of nanostructures of cobalt double-rings (D-rings) and double-dots (D-dots) is investigated in the framework of micromagnetic simulations. The arrays contain two identical coupled rings (wide and narrow) or dots with outer diameter of 200 nm and thicknesses ranging from 2–20 nm. Hysteresis loops, dipole–dipole and exchange energies are systematically calculated for the cases of the structures touching and the structures with a 50-nm inter-magnet separation; moreover, magnetization states along the hysteresis curve are analyzed. The results of both dot and ring D-magnets are compared with the corresponding individual magnets. Our results reveal that all D-ring (in contact and separated) arrays containing narrow rings exhibit non-null remanent magnetization; furthermore, higher coercive fields are promoted when the magnet thickness is increased. It is observed that the magnetization reversal is driven mainly by a clockwise rotation of onion-states, followed by states of frustrated vortices. Our results could help improve the understanding of the magnetic interactions in nanomagnet arrays.

  18. Cobalt double-ring and double-dot structures: Magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    López-Urías, F., E-mail: flo@ipicyt.edu.mx [Advanced Materials Department, IPICYT, Camino a la presa San José 2055, Col. Lomas 4a sección, 78216, San Luis Potosí S.L.P., México (Mexico); Torres-Heredia, J.J. [Instituto Tecnológico Superior de Las Choapas, Col. J. M. Rosa do, 96980, Las Choapas, Veracruz (Mexico); Muñoz-Sandoval, E. [Advanced Materials Department, IPICYT, Camino a la presa San José 2055, Col. Lomas 4a sección, 78216, San Luis Potosí S.L.P., México (Mexico)

    2016-02-15

    The magnetization reversal mechanism of nanostructures of cobalt double-rings (D-rings) and double-dots (D-dots) is investigated in the framework of micromagnetic simulations. The arrays contain two identical coupled rings (wide and narrow) or dots with outer diameter of 200 nm and thicknesses ranging from 2–20 nm. Hysteresis loops, dipole–dipole and exchange energies are systematically calculated for the cases of the structures touching and the structures with a 50-nm inter-magnet separation; moreover, magnetization states along the hysteresis curve are analyzed. The results of both dot and ring D-magnets are compared with the corresponding individual magnets. Our results reveal that all D-ring (in contact and separated) arrays containing narrow rings exhibit non-null remanent magnetization; furthermore, higher coercive fields are promoted when the magnet thickness is increased. It is observed that the magnetization reversal is driven mainly by a clockwise rotation of onion-states, followed by states of frustrated vortices. Our results could help improve the understanding of the magnetic interactions in nanomagnet arrays.

  19. Concentric Titled Double-Helix Dipole Magnets

    International Nuclear Information System (INIS)

    Rainer Meinke, Ph.D; Carl Goodzeit; Millicent Ball, Ph.D

    2003-01-01

    The high magnetic fields required for future accelerator magnets can only be achieved with Nb3Sn, other A15 or HTS type conductors, which are brittle and sensitive to mechanical strain. The traditional ''cosine-theta'' dipole configuration has intrinsic drawbacks that make it difficult and expensive to employ such conductors in these designs. Some of these problems involve (1) difficulty in applying enough pre-stress to counteract Lorentz forces without compromising conductor performance; (2) small minimum bend radii of the conductor necessitating the intricate wind-and-react coil fabrication; (3) complex spacers in particular for coil ends and expensive tooling for coil fabrication; (4) typically only 2/3 of the coil aperture can be used with achievable field uniformity

  20. Experimental observations of strong double layers. [in triple plasma device for lower magnetospheric simulation

    Science.gov (United States)

    Coakley, P.; Hershkowitz, N.; Hubbard, R.; Joyce, G.

    1978-01-01

    A computer simulation is applied to the production of strong electric potential double layers (DL) in a triple plasma device. The simulation is intended to represent DL in the low magnetosphere above the auroral zones. The DL are described as standing electrostatic shocks with different energy coefficients in their strong and weak forms. The strong DL was generally found to be unstable, but stability could be imparted if a population of trapped electrons was presented. Stability increased with the length of the system. A schematic for the system is presented, and a phase-space plot of electrons (indicating system stability) is graphed.

  1. Anomalous transport phenomena in Fermi liquids with strong magnetic fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Kontani, Hiroshi [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

    2008-02-15

    In this paper, we present recent developments in the theory of transport phenomena based on the Fermi liquid theory. In conventional metals, various transport coefficients are scaled according to the quasiparticles relaxation time, {tau}, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems. The most famous example would be high-T{sub c} superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. This issue has been one of the most significant unresolved problems in HTSCs for a long time. Similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). The main goal of this study is to demonstrate whether the anomalous transport phenomena in HTSC is evidence of a non-Fermi liquid ground state, or just RTA violation in strongly correlated Fermi liquids. Another goal is to establish a unified theory of anomalous transport phenomena in metals with strong magnetic fluctuations. For these purposes, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. In a Fermi liquid, an excited quasiparticle induces other excited quasiparticles by collision, and current due to these excitations is called a current vertex correction (CVC). Landau noticed the existence of CVC first, which is indispensable for calculating transport coefficients in accord with the conservation laws. Here, we develop a transport theory involving resistivity and the Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the CVC. In nearly AF Fermi liquids, we find that the strong backward scattering due to AF fluctuations induces the CVC with prominent momentum dependence. This feature of the CVC can account for the significant enhancement in the Hall coefficient

  2. Anomalous transport phenomena in Fermi liquids with strong magnetic fluctuations

    International Nuclear Information System (INIS)

    Kontani, Hiroshi

    2008-01-01

    In this paper, we present recent developments in the theory of transport phenomena based on the Fermi liquid theory. In conventional metals, various transport coefficients are scaled according to the quasiparticles relaxation time, τ, which implies that the relaxation time approximation (RTA) holds well. However, such a simple scaling does not hold in many strongly correlated electron systems. The most famous example would be high-T c superconductors (HTSCs), where almost all the transport coefficients exhibit a significant deviation from the RTA results. This issue has been one of the most significant unresolved problems in HTSCs for a long time. Similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). The main goal of this study is to demonstrate whether the anomalous transport phenomena in HTSC is evidence of a non-Fermi liquid ground state, or just RTA violation in strongly correlated Fermi liquids. Another goal is to establish a unified theory of anomalous transport phenomena in metals with strong magnetic fluctuations. For these purposes, we develop a method for calculating various transport coefficients beyond the RTA by employing field theoretical techniques. In a Fermi liquid, an excited quasiparticle induces other excited quasiparticles by collision, and current due to these excitations is called a current vertex correction (CVC). Landau noticed the existence of CVC first, which is indispensable for calculating transport coefficients in accord with the conservation laws. Here, we develop a transport theory involving resistivity and the Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the CVC. In nearly AF Fermi liquids, we find that the strong backward scattering due to AF fluctuations induces the CVC with prominent momentum dependence. This feature of the CVC can account for the significant enhancement in the Hall coefficient, magnetoresistance

  3. The realization of strong, stray static magnetic fields

    Czech Academy of Sciences Publication Activity Database

    Žežulka, Václav; Straka, Pavel

    2012-01-01

    Roč. 9, č. 1 (2012), s. 71-77 ISSN 1214-9705 Institutional research plan: CEZ:AV0Z30460519 Keywords : magnetic fields * magnetic circuits * permanent NdFeB magnets Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.530, year: 2011 http://www.irsm.cas.cz/materialy/acta_content/2012_01/7_Zezulka.pdf

  4. Tunnel magnetoresistance and linear conductance of double quantum dots strongly coupled to ferromagnetic leads

    Energy Technology Data Exchange (ETDEWEB)

    Weymann, Ireneusz, E-mail: weymann@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań (Poland)

    2015-05-07

    We analyze the spin-dependent linear-response transport properties of double quantum dots strongly coupled to external ferromagnetic leads. By using the numerical renormalization group method, we determine the dependence of the linear conductance and tunnel magnetoresistance on the degree of spin polarization of the leads and the position of the double dot levels. We focus on the transport regime where the system exhibits the SU(4) Kondo effect. It is shown that the presence of ferromagnets generally leads the suppression of the linear conductance due to the presence of an exchange field. Moreover, the exchange field gives rise to a transition from the SU(4) to the orbital SU(2) Kondo effect. We also analyze the dependence of the tunnel magnetoresistance on the double dot levels' positions and show that it exhibits a very nontrivial behavior.

  5. Application of orbital strong magnet in the extraction of deep orbital magnetic foreign bodies

    Directory of Open Access Journals (Sweden)

    Jin-Chen Jia

    2017-12-01

    Full Text Available AIM: To investigate the surgical method and efficacy of extraction of deep orbital magnetic foreign bodies by mean of an orbital strong magnet. METHODS: A retrospective analysis of clinical data of patients with deep orbital magnetic foreign bodies(OMFBin Hebei Eye Hospital from June 2014 to May 2017 was processed. A total of 23 eyes were enrolled, among them, 14 eyes of extraorbital OMFB, 9 eyes of intraorbital OMFB. The rate of extraction of foreign bodies and the postoperative complications were observed. RESULTS: All eyes of intraorbital foreign bodies were successfully extracted with 100% success rate. Twelve of 14 eyes of extraorbital foreign bodies were extracted with 86% success rate. Mild orbital hemorrhage were found in 2 eyes. There was no other obvious complication such as visual loss, orbital massive hemorrhage or limited ocular movement. CONCLUSION: It's an ideal surgical method to extract the deep orbital magnetic foreign bodies by mean of an orbital strong magnet, with mini-injury, high success rate, short duration and few complications.

  6. Ion H2+ can dissociate in a strong magnetic field

    International Nuclear Information System (INIS)

    Turbiner, A.V.; Lopez, J.C.; Flores-Riveros, A.

    2001-01-01

    In framework of a variational method the molecular ion H 2 + in a magnetic field is studied. An optimal form of the vector potential corresponding to a given magnetic field is chosen. It is shown that for any magnetic field strength as well as for any orientation of the molecular axis the system (ppe) possesses a minimum in the potential energy. The stable configuration always corresponds to elongation along the magnetic line. However, for magnetic fields B ≥ 5 x 10 11 G and some orientations the ion H 2 + becomes instable decaying to H-atom + p [ru

  7. Mott-insulating phases and magnetism of fermions in a double-well optical lattice

    International Nuclear Information System (INIS)

    Wang, Xin; Zhou, Qi; Das Sarma, S.

    2011-01-01

    We theoretically investigate, using nonperturbative strong correlation techniques, Mott-insulating phases and magnetic ordering of two-component fermions in a two-dimensional double-well optical lattice. At filling of two fermions per site, there are two types of Mott insulators, one of which is characterized by spin-1 antiferromagnetism below the Neel temperature. The superexchange interaction in this system is induced by the interplay between the interband interaction and the spin degree of freedom. A great advantage of the double-well optical lattice is that the magnetic quantum phase diagram and the Neel temperature can be easily controlled by tuning the orbital energy splitting of the two-level system. Particularly, the Neel temperature can be one order of magnitude larger than that in standard optical lattices, facilitating the experimental search for magnetic ordering in optical lattice systems.

  8. Magnetic transition in double perovskite systems

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, O., E-mail: navarro@servidor.unam.m [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apdo. Postal 70-360, 04510 Mexico DF (Mexico); Aguilar, B. [Laboratorio Interinstitucional de Magnetismo Natural, Instituto de Geofisica, Sede Michoacan, Universidad Nacional Autonoma de Mexico, Morelia (Mexico); Avignon, M. [Institut Neel, CNRS and Universite Joseph Fourier, BP 166, 38042 Grenoble Cedex 9 (France)

    2010-05-15

    The search for materials having complete spin polarization and high Curie temperature have received a lot of attention in view of spintronics applications, especially the ferromagnetic (F) Sr{sub 2}FeMoO{sub 6}, because of its fairly high Curie temperature (T{sub C}= 450 K), half-metallic character, large magnetoresistance and potential applications. On the other hand, Sr{sub 2}FeWO{sub 6} is insulating and antiferromagnetic (AF) with T{sub N}=37K. With a double exchange type model it has been shown that F-AF transition can be driven by super-exchange interactions with increasing Fe-M (M=Mo, W) charge transfer energy. So, the charge transfer energy is expected to be larger in FeW than in FeMo compounds. Using a tight-binding model with the renormalized perturbation expansion technique, we determine the density of states for the AF phase and the electronic energy difference for the F- and AF-phases as a function of the Fe-M charge transfer energy. The F-AF transition in the ordered system Sr{sub 2}FeMo{sub x}W{sub 1-x}O{sub 6} occurs for xapprox0.3, in good agreement with the experimental value. We also studied the effect of the diagonal disorder in the variation of the number of conduction electrons on Fe and M sites. Finally, the behavior of the Curie temperature as a function of the Mo/W concentration is determined.

  9. Magnetic studies of Co2+, Ni2+, and Zn2+-modified DNA double-crossover lattices

    Science.gov (United States)

    Dugasani, Sreekantha Reddy; Oh, Young Hoon; Gnapareddy, Bramaramba; Park, Tuson; Kang, Won Nam; Park, Sung Ha

    2018-01-01

    We fabricated divalent-metal-ion-modified DNA double-crossover (DX) lattices on a glass substrate and studied their magnetic characteristics as a function of ion concentrations [Co2+], [Ni2+] and [Zn2+]. Up to certain critical concentrations, the DNA DX lattices with ions revealed discrete S-shaped hysteresis, i.e. characteristics of strong ferromagnetism, with significant changes in the coercive field, remanent magnetization, and susceptibility. Induced magnetic dipoles formed by metal ions in DNA duplex in the presence of a magnetic field imparted ferromagnetic behaviour. By considering hysteresis and the magnitude of magnetization in a magnetization-magnetic field curve, Co2+-modified DNA DX lattices showed a relatively strong ferromagnetic nature with an increasing (decreasing) trend of coercive field and remanent magnetization when [Co2+] ≤ 1 mM ([Co2+] > 1 mM). In contrast, Ni2+ and Zn2+-modified DNA DX lattices exhibited strong and weak ferromagnetic behaviours at lower (≤1 mM for Ni2+ and ≤0.5 mM for Zn2+) and higher (>1 mM for Ni2+ and >0.5 mM for Zn2+) concentrations of ions, respectively. About 1 mM of [Co2+], [Ni2+] and [Zn2+] in DNA DX lattices was of special interest with regard to physical characteristics and was identified to be an optimum concentration of each ion. Finally, we measured the temperature-dependent magnetic characteristics of the metal-ion-modified DNA DX lattices. Nonzero magnetization and inverse susceptibility with almost constant values were observed between 25 and 300 K, with no indication of a magnetic transition. This indicated that the magnetic Curie temperatures of Co2+, Ni2+ and Zn2+-modified DNA DX lattices were above 300 K.

  10. The collinear ↑↑↓↓ magnetism driven ferroelectricity in double-perovskite multiferroics

    International Nuclear Information System (INIS)

    Jia, Ting; Zeng, Zhi; Lin, H. Q.

    2017-01-01

    The multiferroics of collinear ↑↑↓↓ magnetism driven ferroelectricity is one type of the magnetically driven ferroelectrics, which attracts much attentions due to their strong magnetoelectric coupling. Here, we summarize the recent progress in this multiferroics with double-perovskite crystal structure, besides Y_2CoMnO_6, Lu_2CoMnO_6, Y_2NiMnO_6 and In_2NiMnO_6 etc.. It is revealed that there are also many uncertainties in present research, making this field fulling of challenges and opportunities. (paper)

  11. Chiral spiral induced by a strong magnetic field

    Directory of Open Access Journals (Sweden)

    Abuki Hiroaki

    2016-01-01

    Full Text Available We study the modification of the chiral phase structure of QCD due to an external magnetic field. We first demonstrate how the effect of magnetic field can systematically be incorporated into a generalized Ginzburg-Landau framework. We then analyze the phase structure in the vicinity of the chiral critical point. In the chiral limit, the effect is found to be so drastic that it brings a “continent” of chiral spiral in the phase diagram, by which the chiral tricritical point is totally washed out. This is the case no matter how small the intensity of magnetic field is. On the other hand, the current quark mass protects the chiral critical point from a weak magnetic field. However, the critical point will eventually be covered by the chiral spiral phase as the magnetic field grows.

  12. The permanent magnet systems generating strong stray fields with large localization region

    International Nuclear Information System (INIS)

    Samofalov, V.N.; Belozorov, D.P.; Ravlik, A.G.

    2008-01-01

    Three systems of permanent magnets, which produce strong magnetic stray fields (SFs) with H>B r =4πM r were studied in this work. Remarkable feature of the developed systems is localization of the strong fields in large region with linear dimension Δr comparable to characteristic magnet dimension a. The first system composed of uniformly magnetized magnets generates sufficiently homogeneous strong SFs, which amounts up to 1.5 of magnets induction B r . The second system with nonuniform magnetization is represented by cylindrical and hemispheric magnets their magnetization vector directed at every point along the radius. Such distribution of magnetization is assumed to be the consequence of magnet radial crystal texture resulting in a high uniaxial anisotropy field H K . It is shown that maximal SFs can exist on the flat surface of cylindrical magnet at the distance r from its axis and their limiting value equals to 4πM r ln(2a/r). Here, the localization region of the fields is comparable to diameter of cylindrical magnet Δr∼2R. As for the hemisphere its SFs are less than corresponding SFs for the cylinder. The third so-called quasi-nonuniform system consists of uniformly magnetized cylindrical sectors their magnetization vector is directed along the sector bisectrix. The strong SFs and their localization region are calculated in details for this case. The passage to radial magnetized cylinder is considered

  13. Magnetic dynamics of weakly and strongly interacting hematite nanoparticles

    DEFF Research Database (Denmark)

    Hansen, Mikkel Fougt; Bender Koch, Christian; Mørup, Steen

    2000-01-01

    The magnetic dynamics of two differently treated samples of hematite nanoparticles from the same batch with a particle size of about 20 nm have been studied by Mossbauer spectroscopy. The dynamics of the first sample, in which the particles are coated and dispersed in water, is in accordance.......3(-0.8)(+1.0) x 10(-10) s for a rotation of the sublattice magnetization directions in the rhombohedral (111) plane. The corresponding median superparamagnetic blocking temperature is about 150 K. The dynamics of the second, dry sample, in which the particles are uncoated and thus allowed to aggregate, is slowed...... down by interparticle interactions and a magnetically split spectrum is retained at room temperature. The temperature variation or the magnetic hyperfine field, corresponding to different quantiles in the hyperfine field distribution, can be consistently described by a mean field model...

  14. System for generating double-pulsed magnetic fields in a kicker magnet

    International Nuclear Information System (INIS)

    Kawakubo, Tadamichi; Tazawa, Sichiro; Arakida, Yosio; Murasugi, Sigeru

    1991-01-01

    Two bunched beams are accelerated in the 1A ring of JHF. They are extracted for meson experiments and for neutron experiments successively. Therefore, the extraction kicker magnet should generate double-pulsed magnetic fields at intervals of about 100 μsec, with a repetition rate of 50 Hz. In order to test the feasibility of generating double pulses, we used two sets of thyratron housings and a kicker magnet for the KEK-PS-extraction system, which has an impedance of 25 Ω. Using a thyratron cathode-loaded system, the first firing induces a second misfire by a rapid voltage drop of the second thyratron cathode. A thyratron anode-loaded system does not have the above-mentioned trouble, and has succeeded in generating the desired double pulses with half of the voltage required for the usual operation of JHF (∼ 80kV). (author)

  15. Neutron star in the presence of strong magnetic field

    Indian Academy of Sciences (India)

    Stars: neutron stars; magnetic fields; equation of state. PACS Nos 26.60.Kp; 52.35.Tc; 97.10.Cv. 1. Introduction. The central density of neutron stars (NS) exceeds the nuclear saturation density (n0 ∼. 0.15 fm. −3. ), thereby giving the idea that compact stars might contain deconfined and chirally restored quark matter in them.

  16. How strongly are the magnetic anisotropy and coordination numbers ...

    Indian Academy of Sciences (India)

    Coordination number around the lanthanide ion is found to alter the magnetic behaviour of all the lanthanide complexes studied and this is contrary to the general belief that the lanthanide ions are inert and exert small ligand field interaction.High symmetric low-coordinate LnIII complexes are found to yield large Ueff values ...

  17. Cigar-shaped quarkonia under strong magnetic field

    Science.gov (United States)

    Suzuki, Kei; Yoshida, Tetsuya

    2016-03-01

    Heavy quarkonia in a homogeneous magnetic field are analyzed by using a potential model with constituent quarks. To obtain anisotropic wave functions and corresponding eigenvalues, the cylindrical Gaussian expansion method is applied, where the anisotropic wave functions are expanded by a Gaussian basis in the cylindrical coordinates. Deformation of the wave functions and the mass shifts of the S-wave heavy quarkonia (ηc, J /ψ , ηc(2 S ), ψ (2 S ) and bottomonia) are examined for the wide range of external magnetic field. The spatial structure of the wave functions changes drastically as adjacent energy levels cross each other. Possible observables in heavy-ion collision experiments and future lattice QCD simulations are also discussed.

  18. Surfactant double layer stabilized magnetic nanofluids for biomedical application

    Energy Technology Data Exchange (ETDEWEB)

    Tombacz, E; Hajdu, A; Illes, E; Majzik, A [Department of Colloid Chemistry, University of Szeged (Hungary); Bica, D; Vekas, L [Center of Fundamental and Advanced Technical Research, Romanian Academy-Timisoara Division (Romania)], E-mail: tombacz@chem.u-szeged.hu

    2008-05-21

    Magnetite nanoparticles were coated with surfactant double layers in order to prepare water based magnetic fluids (MFs). The effects of head group (sulfonate, carboxylate) and alkyl chain length (11-17 C atoms) and the combination of surfactants were studied. Adsorption, dynamic light scattering (DLS) and electrophoretic mobility measurements were performed. The quantity of surfactant varied between 0.3 and 0.5 g, i.e. their specific amount ranges over 1.5-2 mmol g{sup -1} magnetite in MFs. The adsorption isotherm of Na oleate on magnetite proved the double layer formation with 2 mmol g{sup -1} saturation value in good harmony with the empirical doses. The effect of diluting MFs, pH and salt concentration was studied. The pH-dependent stability and the salt tolerance of MFs were different owing to the dissociation of the outermost hydrophilic groups and the hydrophobic interactions scaling with the alkyl chain length of surfactant. The hydrophobic interactions are favored only for oleic and myristic acid double layers. In these MFs, aggregation cannot be observed even in fairly dilute systems up to the physiological salt concentration around neutral pH 6-8 favored in biomedical application. The stable oleic and myristic acid double layers can hinder effectively the aggregation of magnetite particles due to the combined steric and electrostatic stabilization.

  19. Strong magnetic field induces superconductivity in a Weyl semimetal

    Science.gov (United States)

    Rosenstein, Baruch; Shapiro, B. Ya.; Li, Dingping; Shapiro, I.

    2017-12-01

    Microscopic theory of the normal-to-superconductor coexistence line of a multiband Weyl superconductor subjected to magnetic field is constructed. It is shown that the Weyl semimetal that is nonsuperconducting or having a small critical temperature Tc at zero field might become a superconductor at higher temperatures when the magnetic field is tuned to a series of quantized values Hn. The pairing occurs on Landau levels. It is argued that the phenomenon is detectable much easier in Weyl semimetals than in parabolic band metals since the quantum limit already has been approached in several Weyl materials. The effect of Zeeman coupling leading to splitting of the reentrant superconducting regions on the magnetic phase diagram is considered. An experimental signature of the superconductivity on Landau levels is the reduction of magnetoresistivity. This has been observed already in Cd3As2 and several other compounds. The novel kind of quantum oscillations of magnetoresistance detected in ZrTe5 is discussed along these lines.

  20. Sensitivity Analysis and Simulation of Theoretical Response of Ceramics to Strong Magnetic Fields

    Science.gov (United States)

    2016-09-01

    448. 23. Song Q, Zhang ZJ. Shape control and associated magnetic properties of spinel cobalt ferrite nanocrystals. Journal of the American Chemical...Strong Magnetic Fields by Carli A Moorehead, Michael M Kornecki, Victoria L Blair, Raymond E Brennan Approved for... Magnetic Fields by Carli A Moorehead Drexel University, Philadelphia, Pennsylvannia Michael M Kornecki, Victoria L Blair, and Raymond E Brennan

  1. A strong angular dependence of magnetic properties of magnetosome chains: Implications for rock magnetism and paleomagnetism

    Science.gov (United States)

    Li, Jinhua; Ge, Kunpeng; Pan, Yongxin; Williams, Wyn; Liu, Qingsong; Qin, Huafeng

    2013-10-01

    Single-domain magnetite particles produced by magnetotactic bacteria (magnetosomes) and aligned in chains are of great interest in the biosciences and geosciences. Here, we investigated angular variation of magnetic properties of aligned Magnetospirillum magneticum AMB-1 cells, each of which contains one single fragmental chain of magnetosomes. With measurements at increasing angles from the chain direction, we observed that (i) the hysteresis loop gradually changes from nearly rectangular to a ramp-like shape (e.g., Bc and remanence decrease), (ii) the acquisition and demagnetization curves of IRM shift toward higher fields (e.g., Bcr increases), and (iii) the FORC diagram shifts toward higher coercivity fields (e.g., Bc,FORC increases). For low-temperature results, compared to unoriented samples, the samples containing aligned chains have a much lower remanence loss of field-cooled (δFC) and zero-field-cooled (δZFC) remanence upon warming through the Verwey transition, higher δ-ratio (δ = δFC/δZFC) for the measurement parallel to the chain direction, and lower δ-ratio, larger δFC and δZFC values for the perpendicular measurement. Micromagnetic simulations confirm the experimental observations and reveal that the magnetization reversal of magnetosome chain appears to be noncoherent at low angles and coherent at high angles. The simulations also demonstrate that the angular dependence of magnetic properties is related to the dispersion degree of individual chains, indicating that effects of anisotropy need to be accounted for when using rock magnetism to identify magnetosomes or magnetofossils once they have been preserved in aligned chains. Additionally, this study experimentally demonstrates an empirical correspondence of the parameter Bc,FORC to Bcr rather than Bc, at least for magnetite chains with strong shape anisotropy. This suggests FORC analysis is a good discriminant of magnetofossils in sediments and rocks.

  2. Period doubling on a non-neutral magnetized electron beam

    International Nuclear Information System (INIS)

    Boswell, R.W.

    1984-01-01

    Low frequency oscillations on a non-neutral magnetized electron beam of very low density are investigated. A perturbation analysis of the slow mode of the rigid rotator equilibrium is developed to illustrate the nature of large amplitude fundamental mode oscillations. The results of this theoretical analysis show two important characteristics: firstly, as the perturbation amplitude is increasedthe waveform ceases to be purely sinusoidal and shows period doubling. Secondly, above a certain threshold, all harmonics of the wave grow and the wave breaks. The results of the former are compared with a simple electron beam experiment and are found to be in good qualitative agreement

  3. A strong permanent magnet-assisted electromagnetic undulator

    Science.gov (United States)

    Halbach, K.

    1987-01-30

    This invention discloses an improved undulator comprising a plurality of electromagnet poles located along opposite sides of a particle beam axis with alternate north and south poles on each side of the beam to cause the beam to wiggle or undulate as it travels generally along the beam axis and permanent magnets spaced adjacent the electromagnetic poles on each side of the axis of said particle beam in an orientation sufficient to reduce the saturation of the electromagnet poles whereby the field strength of the electromagnet poles can be increased beyond the normal saturation levels of the electromagnetic poles. 4 figs.

  4. Mechanically strong dual responsive nanocomposite double network hydrogel for controlled drug release of asprin.

    Science.gov (United States)

    Chen, Yang; Song, Guocheng; Yu, Junrong; Wang, Yan; Zhu, Jing; Hu, Zuming

    2018-03-08

    Mechanically strong dual/multi-stimuli-responsive smart hydrogels have attracted extensive attention in recent years. A novel tough, mechanical strong and biocompatible dual pH- and temperature- responsive poly (N-isopropylacrylamide) /clay (laponite XLG)/carboxymethyl chitosan (CMCTs) /genipin nanocomposite double network hydrogel was synthesized through a facile, one-pot free radical polymerization initiated by the ultraviolet light, using clay and the natural molecular-genipin as the cross-linkers instead of toxic organic molecules. Crucial factors, the content of CMCTs, clay and genipin, for synthesizing the mechanical strong hydrogels were investigated. When the content of CMCTs, clay and genipin were 5 wt%, 33.3 wt% and 0.175 wt%, respectively (to the weight of N-isopropylacrylamide), these prepared hydrogels exhibited a high tensile strength of 137.9 kPa at the failure strain of 446.1%. Furthermore, the relationship between swelling and deswelling rate of the synthesized hydrogels and the above crucial factors were also studied. Besides, the synthesized hydrogels displayed a considerable controlled release property of asprin by tuning their inner crosslink density. Owing to this property, they may have great potential in the drug delivery systems. Copyright © 2018 Elsevier Ltd. All rights reserved.

  5. Sharp-front wave of strong magnetic field diffusion in solid metal

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Bo; Gu, Zhuo-wei; Kan, Ming-xian; Wang, Gang-hua; Zhao, Jian-heng [Institute of Fluid Physics, CAEP, P.O. Box 919-105, Mianyang 621900 (China)

    2016-08-15

    When a strong magnetic field diffuses into a solid metal, if the metal's resistance possesses an abrupt rise at some critical temperature and the magnetic field strength is above some critical value, the magnetic field will diffuse into the metal in the form of a sharp-front wave. Formulas for the critical conditions under which a sharp-front magnetic diffusion wave emerges and a formula for the wave-front velocity are derived in this work.

  6. One-loop QCD thermodynamics in a strong homogeneous and static magnetic field

    Science.gov (United States)

    Rath, Shubhalaxmi; Patra, Binoy Krishna

    2017-12-01

    We have studied how the equation of state of thermal QCD with two light flavors is modified in a strong magnetic field. We calculate the thermodynamic observables of hot QCD matter up to one-loop, where the magnetic field affects mainly the quark contribution and the gluon part is largely unaffected except for the softening of the screening mass. We have first calculated the pressure of a thermal QCD medium in a strong magnetic field, where the pressure at fixed temperature increases with the magnetic field faster than the increase with the temperature at constant magnetic field. This can be understood from the dominant scale of thermal medium in the strong magnetic field, being the magnetic field, in the same way that the temperature dominates in a thermal medium in the absence of magnetic field. Thus although the presence of a strong magnetic field makes the pressure of hot QCD medium larger, the dependence of pressure on the temperature becomes less steep. Consistent with the above observations, the entropy density is found to decrease with the temperature in the presence of a strong magnetic field which is again consistent with the fact that the strong magnetic field restricts the dynamics of quarks to two dimensions, hence the phase space becomes squeezed resulting in the reduction of number of microstates. Moreover the energy density is seen to decrease and the speed of sound of thermal QCD medium increases in the presence of a strong magnetic field. These findings could have phenomenological implications in heavy ion collisions because the expansion dynamics of the medium produced in non-central ultra-relativistic heavy ion collisions is effectively controlled by both the energy density and the speed of sound.

  7. Strongly Coupled Magnetic and Electronic Transitions in Multivalent Strontium Cobaltites

    OpenAIRE

    Lee, J. H.; Choi, Woo Seok; Jeen, H.; Lee, H.-J.; Seo, J. H.; Nam, J.; Yeom, M. S.; Lee, H. N.

    2017-01-01

    The topotactic phase transition in SrCoO x (x = 2.5–3.0) makes it possible to reversibly transit between the two distinct phases, i.e. the brownmillerite SrCoO2.5 that is a room-temperature antiferromagnetic insulator (AFM-I) and the perovskite SrCoO3 that is a ferromagnetic metal (FM-M), owing to their multiple valence states. For the intermediate x values, the two distinct phases are expected to strongly compete with each other. With oxidation of SrCoO2.5, however, it has been conjectured t...

  8. Torque characteristics of double-stator permanent magnet synchronous machines

    Directory of Open Access Journals (Sweden)

    Awah Chukwuemeka Chijioke

    2017-12-01

    Full Text Available The torque profile of a double-stator permanent magnet (PM synchronous machine of 90 mm stator diameter having different rotor pole numbers as well as dual excitation is investigated in this paper. The analysis includes a comparative study of the machine’s torque and power-speed curves, static torque and inductance characteristics, losses and unbalanced magnetic force. The most promising flux-weakening potential is revealed in 13- and 7-rotor pole machines. Moreover, the machines having different rotor/stator (Nr/Ns pole combinations of the form Nr = Ns ± 1 have balanced and symmetric static torque waveforms variation with the rotor position in contrast to the machines having Nr = Ns ± 2. Further, the inductance results of the analyzed machines reveal that the machines with odd rotor pole numbers have better fault-tolerant capability than their even rotor pole equivalents. A prototype of the developed double-stator machine having a 13-pole rotor is manufactured and tested for verification.

  9. Solitons and double-layers of electron-acoustic waves in magnetized plasma; an application to auroral zone plasma

    Science.gov (United States)

    El-Labany, S. K.; Shalaby, M.; Sabry, R.; El-Sherif, L. S.

    2012-07-01

    A theoretical investigation is carried out for understanding the properties of electron-acoustic potential structures (i.e., solitary waves and double-layers) in a magnetized plasma whose constituents are a cold magnetized electron fluid, hot electrons obeying a nonthermal distribution, and stationary ions. For this purpose, the hydrodynamic equations for the cold magnetized electron fluid, nonthermal electron density distribution, and the Poisson equation are used to derive the corresponding nonlinear evolution equation; modified Zakharov-Kuznetsov (MZK) equation, in the small amplitude regime. The MZK equation is analyzed to examine the existence regions of the solitary pulses and double-layers. It is found that rarefactive electron-acoustic solitary waves and double-layers strongly depend on the density and temperature ratios of the hot-to-cold electron species as well as the nonthermal electron parameter.

  10. Double-contrast magnetic resonance examination of ulcerative colitis

    Energy Technology Data Exchange (ETDEWEB)

    Sardanelli, F.; De Cicco, E.; Renzetti, P.; Parodi, R.C.; Calabrese, M. [Department of Radiology, University of Genoa (Italy)

    1999-06-01

    The aim of our work was to propose a double-contrast magnetic resonance examination (DCMRE) in the follow-up of ulcerative colitis (UC), comparing this new technique with X-ray double-contrast barium enema (DCBE). After preparation with colon-cleansing regimen used for DCBE, six UC patients and six control subjects underwent a 1.5-T examination: supine position, coronal and axial fat-spectral-saturation breath-hold gradient-echo T1-weighted sequences after intravenous hypotonization and 1500-2000 cc air insufflation. Without evacuating the primarily insufflated air, the same images were acquired after endorectal administration of negative superparamagnetic contrast agent (600 cc) and intravenous administration of positive paramagnetic contrast agent (0.2 mmol/kg). All patients had undergone DCBE in the four preceding weeks. We found significant increase in wall thickness of UC affected vs apparently unaffected segments (p = 0.0425) and vs CG (p = 0.0447), significant increase in enhancement percent of UC affected vs apparently unaffected segments (p = 0.0161) and vs CG (p = 0.0185), and no significant difference for enhancement percent of UC unaffected segments vs CG. DCMRE and DCBE localized the UC extension at the same sites in all patients. Double-contrast MR examination time was 20-30 min. This new method could be used in follow-up of UC patients. (orig.) With 4 figs., 14 refs.

  11. On function classes related pertaining to strong approximation of double Fourier series

    Science.gov (United States)

    Baituyakova, Zhuldyz

    2015-09-01

    The investigation of embedding of function classes began a long time ago. After Alexits [1], Leindler [2], and Gogoladze[3] investigated estimates of strong approximation by Fourier series in 1965, G. Freud[4] raised the corresponding saturation problem in 1969. The list of the authors dealing with embedding problems partly is also very long. It suffices to mention some names: V. G. Krotov, W. Lenski, S. M. Mazhar, J. Nemeth, E. M. Nikisin, K. I. Oskolkov, G. Sunouchi, J. Szabados, R. Taberski and V. Totik. Study on this topic has since been carried on over a decade, but it seems that most of the results obtained are limited to the case of one dimension. In this paper, embedding results are considered which arise in the strong approximation by double Fourier series. We prove theorem on the interrelation between the classes Wr1,r2HS,M ω and H(λ, p, r1, r2, ω(δ1, δ2)), in the one-dimensional case proved by L. Leindler.

  12. Pion Production from Proton Synchrotron Radiation under Strong Magnetic Field in a Relativistic Quantum Approach

    Directory of Open Access Journals (Sweden)

    Maruyama Tomoyuki

    2016-01-01

    Full Text Available We study pion production from proton synchrotron radiation in the presence of strong magnetic fields by using the exact proton propagator in a strong magnetic field and explicitly including the anomalous magnetic moment. Results in this exact quantum approach do not agree with those obtained in the semi-classical approach. Then, we find that the anomalous magnetic moment of the proton greatly enhances the production rate by about two orders magnitude, and that the decay width satisfies a robust scaling law.

  13. Pion Production from Proton Synchrotron Radiation under Strong Magnetic Field in Relativistic Quantum Approach

    Directory of Open Access Journals (Sweden)

    Maruyama Tomoyuki

    2016-01-01

    Full Text Available We study pion production from proton synchrotron radiation in the presence of strong magnetic fields by using the exact proton propagator in a strong magnetic field and explicitly including the anomalous magnetic moment. Results in this exact quantum-field approach do not agree with those obtained in the semi-classical approach. Furthermore, we also find that the anomalous magnetic moment of the proton greatly enhances the production rate about by two orders of magnitude, and that the polar angle of an emitted pion is the same as that of an initial proton.

  14. Imaginary potential in strongly coupled N = 4 SYM plasma in a magnetic field

    Science.gov (United States)

    Zhang, Zi-qiang; Hou, De-fu

    2018-03-01

    We study the effect of a constant magnetic field on the imaginary part of a quarkonia potential in a strongly-coupled N = 4 SYM plasma. We consider the pair axis to be aligned perpendicularly and parallel to the magnetic field, respectively. For both cases, we find that the presence of the magnetic field tends to enhance the imaginary potential thus decreasing the thermal width. In addition, the magnetic field has a stronger effect on the imaginary potential when the pair axis is perpendicular to the magnetic field rather than parallel.

  15. Experimental demonstration of the equivalence of inductive and strongly coupled magnetic resonance wireless power transfer

    Science.gov (United States)

    Ricketts, David S.; Chabalko, Matthew J.; Hillenius, Andrew

    2013-02-01

    In this work, we show experimentally that wireless power transfer (WPT) using strongly coupled magnetic resonance (SCMR) and traditional induction are equivalent. We demonstrate that for a given coil separation, and to within 4%, strongly coupled magnetic resonance and traditional induction produce the same theoretical efficiency of wireless power transfer versus distance. Moreover, we show that the difference between traditional induction and strongly coupled magnetic resonance is in the implementation of the impedance matching network where strongly coupled magnetic resonance uses the mini-loop impedance match. The mini-loop impedance mach provides a low-loss, high-ratio impedance transformation that makes it desirable for longer distance wireless power transfer, where large impedance transformations are needed to maximize power transfer.

  16. Regularity and Chaos in the Hydrogen Atom Highly Excited with a Strong Magnetic Field

    Directory of Open Access Journals (Sweden)

    M. Amdouni

    2014-01-01

    Full Text Available The effects of the relativistic corrections on the energy spectra are analyzed. Effective simulations based on manipulations of operators in the Sturmian basis are developed. Discrete and continuous energy spectra of a hydrogen atom with realistic nucleus mass in a strong magnetic field are computed. The transition from regularity to chaos in diamagnetic problem with the effect of the nucleus recoil energy is explored. Anticrossing of energy levels is observed for strong magnetic field.

  17. Direct URCA-processes in neutron star quark core with strong magnetic field.

    Directory of Open Access Journals (Sweden)

    Belyaev Vasily

    2017-01-01

    In evaluations, the strength of magnetic field corresponds to the case, where the quarks of medium occupy a lot of Landau levels, while the electrons are in ground Landau level. The analytical dependence of neutrino emissivity on chemical potentials of quarks and electrons, temperature and magnetic field strength is obtained and briefly discussed. The result could be important in application to a massive strongly magnetized neutron star with quark core.

  18. Working with MRI: An investigation of occupational exposure to strong static magnetic fields and associated symptoms

    NARCIS (Netherlands)

    Schaap, K.

    2015-01-01

    Magnetic resonance imaging (MRI) makes use of electromagnetic fields in the non-ionizing radiation frequency ranges. One of them is a continuously present strong static magnetic field (SMF), which extends up to several meters around the scanner. Each time an MRI worker performs tasks near the

  19. A magnetic resonance imaging study of double elevator palsy.

    Science.gov (United States)

    Cadera, W; Bloom, J N; Karlik, S; Viirre, E

    1997-06-01

    The pathophysiology of double elevator palsy is poorly understood. We assessed two patients with this condition using magnetic resonance imaging (MRI) to evaluate the appearance of the extraocular muscles. Cross-sectional study. Radiology department of a university-affiliated hospital in London, Ont. Two patients from a private ophthalmology practice who had undergone complete transpositions of the horizontal rectus muscles to treat hypotropia associated with double elevator palsy. MRI. A volume scanning technique was used to obtain maximum information about the muscles. Appearance of the extraocular muscles. In both patients MRI showed decreased volume of the superior rectus muscle on the affected side. The other rectus muscles were normal. This suggested either congenital hypoplasia or paresis of the involved superior rectus muscle. In addition, the full tendon transpositions of the medial and lateral recti did not appreciably change the middle and deep orbital pathways of the transposed horizontal rectus muscles. MRI may be a useful adjunct to saccadic velocity assessments in differentiating between primary inferior rectus restriction, primary superior rectus paresis and congenital supranuclear elevator deficiency.

  20. Correlation between magnetic properties and nuclear magnetic resonance observations in Sr2FeMoO6 double perovskite

    International Nuclear Information System (INIS)

    Colis, S.; Pourroy, G.; Panissod, P.; Meny, C.; Dinia, A.

    2004-01-01

    We present the influence of the sintering temperature on the magnetic properties of Sr 2 FeMoO 6 double perovskite, on the basis of magnetization and nuclear magnetic resonance (NMR) measurements. Interestingly, the saturation magnetization originating mainly from the Fe moments is correlated with the amount of Mo magnetic moments observed by NMR measurements. We show that there is an optimum temperature of 1000 deg. C for which the reaction leading to the double perovskite becomes more advanced and/or the number of antisite defects is minimum

  1. Buoyant convection during Czochralski silicon growth with a strong, non-uniform, axisymmetric magnetic field

    Science.gov (United States)

    Khine, Y. Y.; Walker, J. S.

    1995-02-01

    This paper treats the buoyant convection during the Czochralski growth of silicon crystals with a steady, strong, non-uniform, axisymmetric magnetic field. We consider a family of magnetic fields which includes a uniform axial magnetic field and a "cusp" field which is produced by identical solenoids placed symmetrically above and below the plane of the crystal-melt interface and free surface. We investigate the evolution of the buoyant convection as the magnetic field is changed continuously from a uniform axial field to a cusp field, with a constant value of the root-mean-squared magnetic flux density in the melt. We also investigate changes as the magnetic flux density is increased. While the cusp field appears very promising, perfect alignment between the local magnetic field vector and the crystal-melt interface or free surface is not possible, so the effects of a slight misalignment are also investigated.

  2. New nontoxic double information magnetic and fluorescent MRI agent

    Energy Technology Data Exchange (ETDEWEB)

    Kublickas, Augustinas; Rastenien, Loreta; Bloznelytė-Plėšnienė, Laima; Karalius, Nerijus [Liquid Crystals Laboratory, Institute of Science and Technology, Lithuanian University of Educational Sciences (Lithuania); Franckevinius, Marius [Institute of Physics, Center for Physical Sciences and Technology (Lithuania); Loudos, George [Technological Educational Institute of Athens (Greece); Fahmi, Amir [Materials Science, Rhein-Waal University of Applied Sciences (Germany); Vaisnoras, Rimas [Liquid Crystals Laboratory, Institute of Science and Technology, Lithuanian University of Educational Sciences (Lithuania)

    2015-05-18

    Today sensitivity of the MRI is not enough compared to the nuclear methods, such as positron emission tomography and single photon emission computed tomography. Challenging its extension to the nanometre scale could provide a powerful new tool for the nanosciences and nanomedicine. To achieve this potential, innovative new detection strategies are required to overcome the severe sensitivity limitations of conventional inductive detection techniques. In this regard, we perform embodiment of nanodiamonds in dendrimer matrix as additional fluorescent optical and magnetic (together with Gd (III)) imaging modalities of the MRI. New hybrid system composed of dendrimer-gadolinium Gd (III) - nanodiamond as a new contrast agent for MRI was studied. Poly(propilene-imine) PPI and poly(amidoamine) PAMAM dendrimers with fixed size of nanocavities will be used as host material to protect organism against the toxicity and also to increase relaxivity of contrast agent (resulting in the increases MRI resolution). Nanodiamond as biocompatible platform to functionalize the contrast agent will be used. This bimodal hybrid system enables to use smaller amount of the contrast agent and could permit the decrease of the lateral toxicity. This bimodal hybrid system as MRI agent is providing double information (magnetic and fluorescent) about the damaged cell.

  3. New nontoxic double information magnetic and fluorescent MRI agent

    International Nuclear Information System (INIS)

    Kublickas, Augustinas; Rastenien, Loreta; Bloznelytė-Plėšnienė, Laima; Karalius, Nerijus; Franckevinius, Marius; Loudos, George; Fahmi, Amir; Vaisnoras, Rimas

    2015-01-01

    Today sensitivity of the MRI is not enough compared to the nuclear methods, such as positron emission tomography and single photon emission computed tomography. Challenging its extension to the nanometre scale could provide a powerful new tool for the nanosciences and nanomedicine. To achieve this potential, innovative new detection strategies are required to overcome the severe sensitivity limitations of conventional inductive detection techniques. In this regard, we perform embodiment of nanodiamonds in dendrimer matrix as additional fluorescent optical and magnetic (together with Gd (III)) imaging modalities of the MRI. New hybrid system composed of dendrimer-gadolinium Gd (III) - nanodiamond as a new contrast agent for MRI was studied. Poly(propilene-imine) PPI and poly(amidoamine) PAMAM dendrimers with fixed size of nanocavities will be used as host material to protect organism against the toxicity and also to increase relaxivity of contrast agent (resulting in the increases MRI resolution). Nanodiamond as biocompatible platform to functionalize the contrast agent will be used. This bimodal hybrid system enables to use smaller amount of the contrast agent and could permit the decrease of the lateral toxicity. This bimodal hybrid system as MRI agent is providing double information (magnetic and fluorescent) about the damaged cell.

  4. Abnormally big magnetic resistance in a strongly compensated silicon doped with manganese

    International Nuclear Information System (INIS)

    Sadullaev, A.B.

    2004-01-01

    The work is devoted to study of an influence of compensating impurities electro-active atoms concentration on galvanomagnetic properties of strongly compensated silicon doped with manganese. It was shown, the possibility for magnetic resistance control of the strongly compensated Si samples by manganese electro-active impurity atoms concentration regulation

  5. Light bending by nonlinear electrodynamics under strong electric and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Young; Lee, Taekoon, E-mail: jykim@kunsan.ac.kr, E-mail: tlee@kunsan.ac.kr [Department of Physics, Kunsan National University, Daihakro 558, Kunsan 573-701 (Korea, Republic of)

    2011-11-01

    We calculate the bending angles of light under the strong electric and magnetic fields by a charged black hole and a magnetized neutron star according to the nonlinear electrodynamics of Euler-Heisenberg interaction. The bending angle of light by the electric field of charged black hole is computed from geometric optics and a general formula is derived for light bending valid for any orientation of the magnetic dipole. The astronomical significance of the light bending by magnetic field of a neutron star is discussed.

  6. Investigating short-range magnetism in strongly correlated materials via magnetic pair distribution function analysis and ab initio theory

    Science.gov (United States)

    Frandsen, Benjamin; Page, Katharine; Brunelli, Michela; Staunton, Julie; Billinge, Simon

    Short-range magnetic correlations are known to exist in a variety of strongly correlated electron systems, but our understanding of the role they play is challenged by the difficulty of experimentally probing such correlations. Magnetic pair distribution function (mPDF) analysis is a newly developed neutron total scattering method that can reveal short-range magnetic correlations directly in real space, and may therefore help ameliorate this difficulty. We present temperature-dependent mPDF measurements of the short-range magnetic correlations in the paramagnetic phase of antiferromagnetic MnO, an archetypal strongly correlated transition-metal oxide. We observe significant correlations on a ~1 nm length scale that differ substantially from the low-temperature long-range-ordered spin arrangement. With no free parameters, ab initio calculations using the self-interaction-corrected local spin density approximation of density functional theory quantitatively reproduce the magnetic correlations to a high degree of accuracy. These results yield valuable insight into the magnetic exchange in MnO and showcase the utility of the mPDF technique for studying magnetic properties of strongly correlated electron systems.

  7. Strong suppression of the positronium channel in double ionization of noble gases by positron impact

    DEFF Research Database (Denmark)

    Bluhme, H.; Knudsen, H.; Merrison, J.P.

    1998-01-01

    Positron-induced double ionization of helium and neon has been studied at energies from threshold to 900 eV. A remarkable difference between the near-threshold behavior of the single and double ionization cross sections is found: Single ionization is dominated by positronium (Ps) formation, while...

  8. STRONG SOLAR WIND DYNAMIC PRESSURE PULSES: INTERPLANETARY SOURCES AND THEIR IMPACTS ON GEOSYNCHRONOUS MAGNETIC FIELDS

    International Nuclear Information System (INIS)

    Zuo, Pingbing; Feng, Xueshang; Wang, Yi; Xie, Yanqiong; Xu, Xiaojun

    2015-01-01

    In this investigation, we first present a statistical result of the interplanetary sources of very strong solar wind dynamic pressure pulses (DPPs) detected by WIND during solar cycle 23. It is found that the vast majority of strong DPPs reside within solar wind disturbances. Although the variabilities of geosynchronous magnetic fields (GMFs) due to the impact of positive DPPs have been well established, there appears to be no systematic investigations on the response of GMFs to negative DPPs. Here, we study both the decompression effects of very strong negative DPPs and the compression from strong positive DPPs on GMFs at different magnetic local time sectors. In response to the decompression of strong negative DPPs, GMFs on the dayside near dawn and near dusk on the nightside, are generally depressed. But near the midnight region, the responses of GMF are very diverse, being either positive or negative. For part of the events when GOES is located at the midnight sector, the GMF is found to abnormally increase as the result of magnetospheric decompression caused by negative DPPs. It is known that under certain conditions magnetic depression of nightside GMFs can be caused by the impact of positive DPPs. Here, we find that a stronger pressure enhancement may have a higher probability of producing the exceptional depression of GMF at the midnight region. Statistically, both the decompression effect of strong negative DPPs and the compression effect of strong positive DPPs depend on the magnetic local time, which are stronger at the noon sector

  9. Do strong, static magnetic fields act on living beings and chemical reactions

    International Nuclear Information System (INIS)

    Demmer, W.

    1986-01-01

    In general, magnetic fields are said to have no direct influence on living beings or simple chemical reactions. There is, however, evidence to confirm that changes in the earth's magnetic field or of artificially produced magnetic fields can alter the activity of different neuronal enzyme systems. An effect on the synthesis of β-galactosidase in the bacterium Escherichia coli by a feeble magnetic field (0.2 to 0.8 mT) and disturbances of the embryogenesis of frogs by a strong magnetic field (1.0 T) have been described. These and similar investigations with whole cells raise the question as to what the effect of magnetic fields on isolated and purified enzymes will be. (orig./SHA) [de

  10. Monte Carlo solutions of Schroedinger's equation for H2+ ion in strong magnetic fields

    International Nuclear Information System (INIS)

    Ozaki, Jiro; Tomishima, Yasuo

    1980-01-01

    The analytical expressions suitable for the Monte Carlo calculation to obtain the solution of Schroedinger's equation of hydrogen molecular ion in a strong magnetic field are derived. The wave functions, the energy values and the equilibrium internuclear distances of 1σsub(g) state of H 2 + are obtained numerically through the Monte Carlo simulation and compared with other results based on the variational method. The agreement between them is fairly good over a wide range of magnetic field. The calculation of the energy values of 1πsub(g) state of H 2 + for various internuclear distances taking a constant magnetic field as a parameter, shows that the antibonding 1πsub(g) state in the absence of the external magnetic field changes to a bonding state with an increasing magnetic field. The lowest energy values and the equilibrium internuclear distances of 1πsub(g) state are also calculated for various magnetic field. (author)

  11. Anisotropic shear viscosity of a strongly coupled non-Abelian plasma from magnetic branes

    Science.gov (United States)

    Critelli, R.; Finazzo, S. I.; Zaniboni, M.; Noronha, J.

    2014-09-01

    Recent estimates for the electromagnetic fields produced in the early stages of noncentral ultrarelativistic heavy ion collisions indicate the presence of magnetic fields B ˜O(0.1-15mπ2), where mπ is the pion mass. It is then of special interest to study the effects of strong (Abelian) magnetic fields on the transport coefficients of strongly coupled non-Abelian plasmas, such as the quark-gluon plasma formed in heavy ion collisions. In this paper we study the anisotropy in the shear viscosity induced by an external magnetic field in a strongly coupled N =4 super Yang-Mills (SYM) plasma. Due to the spatial anisotropy created by the magnetic field, the most general viscosity tensor of a magnetized plasma has five shear viscosity coefficients and two bulk viscosities. We use the holographic correspondence to evaluate two of the shear viscosities, η⊥≡ηxyxy (perpendicular to the magnetic field) and η∥≡ηxzxz=ηyzyz (parallel to the field). When B ≠0 the shear viscosity perpendicular to the field saturates the viscosity bound η⊥/s=1/(4π), while in the direction parallel to the field the bound is violated since η∥/s<1/(4π). However, the violation of the bound in the case of strongly coupled SYM is minimal even for the largest value of B that can be reached in heavy ion collisions.

  12. Magnetization dynamics and frustration in the multiferroic double perovskite Lu2MnCoO6.

    OpenAIRE

    Zapf, V. S.; Ueland, B. G.; Laver, M.; Lonsky, M.; Pohlit, M.; Muller, J.; Lancaster, T.; Moller, J.S.; Blundell, S.J.; Singleton, J.; Mira, J.; Yanez-Vilar, S.; Senarıs-Rodrıguez, M. A.

    2016-01-01

    We investigate the magnetic ordering and the magnetization dynamics (from kHz to THz time scales) of the double perovskite Lu2MnCoO6 using elastic neutron diffraction, muon spin relaxation, and micro-Hall magnetization measurements. This compound is known to be a type II multiferroic with the interesting feature that a ferromagneticlike magnetization hysteresis loop couples to an equally hysteretic electric polarization in the bulk of the material despite a zero-field magnetic ordering of the...

  13. In-medium covariant propagator of baryons under a strong magnetic field: Effect of the intrinsic magnetic moments

    Energy Technology Data Exchange (ETDEWEB)

    Aguirre, R.M.; Paoli, A.L. de [Universidad Nacional de La Plata, and IFLP, Departamento de Fisica, Facultad de Ciencias Exactas, La Plata (Argentina)

    2016-11-15

    We obtain the covariant propagator at finite temperature for interacting baryons immersed in a strong magnetic field. The effect of the intrinsic magnetic moments on the Green function are fully taken into account. We make an expansion in terms of eigenfunctions of a Dirac field, which leads us to a compact form of its propagator. We present some simple applications of these propagators, where the statistical averages of nuclear currents and energy density are evaluated. (orig.)

  14. Strong magnetic enhancement in self-assembled multiferroic-ferrimagnetic nanostructures

    Science.gov (United States)

    Chen, Ying-Jiun; Hsieh, Ying-Hui; Liao, Sheng-Chieh; Hu, Zhiwei; Huang, Meng-Jie; Kuo, Wei-Cheng; Chin, Yi-Ying; Uen, Tzeng-Ming; Juang, Jenh-Yih; Lai, Chih-Huang; Lin, Hong-Ji; Chen, Chien-Te; Chu, Ying-Hao

    2013-05-01

    In the past decade, self-assembled vertical nano-heterostructures have drawn considerable attention because a high interface-to-volume ratio can be used to tailor or create functionalities. We have systematically investigated the magnetic properties of oxide heterostructures consisting of the CoFe2O4 nanopillars embedded in the BiFeO3 matrix using macroscopic magnetization measurements and element-selective soft X-ray absorption magnetic circular dichroism (XMCD) at the Co- and Fe-L2,3 edge. The magnetization and XMCD data show that the total ordered magnetic moment of Co2+ in CoFe2O4-BiFeO3 nano-heterostructures is strongly enhanced. This study clearly indicates that the high interface-to-volume ratio vertical nanostructure creates a strong ferromagnetic and antiferromagnetic magnetic coupling via an interface. Furthermore, the magnetic coupling can be tuned in the multiferroic-ferrimagnetic self-assembled heterostructures by controlling the spacing between nanopillars.In the past decade, self-assembled vertical nano-heterostructures have drawn considerable attention because a high interface-to-volume ratio can be used to tailor or create functionalities. We have systematically investigated the magnetic properties of oxide heterostructures consisting of the CoFe2O4 nanopillars embedded in the BiFeO3 matrix using macroscopic magnetization measurements and element-selective soft X-ray absorption magnetic circular dichroism (XMCD) at the Co- and Fe-L2,3 edge. The magnetization and XMCD data show that the total ordered magnetic moment of Co2+ in CoFe2O4-BiFeO3 nano-heterostructures is strongly enhanced. This study clearly indicates that the high interface-to-volume ratio vertical nanostructure creates a strong ferromagnetic and antiferromagnetic magnetic coupling via an interface. Furthermore, the magnetic coupling can be tuned in the multiferroic-ferrimagnetic self-assembled heterostructures by controlling the spacing between nanopillars. Electronic supplementary

  15. Heavy quark potential in a static and strong homogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Hasan, Mujeeb; Chatterjee, Bhaswar; Patra, Binoy Krishna [Indian Institute of Technology Roorkee, Department of Physics, Roorkee (India)

    2017-11-15

    We have investigated the properties of quarkonia in a thermal QCD medium in the background of strong magnetic field. For that purpose, we employ the Schwinger proper-time quark propagator in the lowest Landau level to calculate the one-loop gluon self-energy, which in the sequel gives the effective gluon propagator. As an artifact of strong magnetic field approximation (eB >> T{sup 2} and eB >> m{sup 2}), the Debye mass for massless flavors is found to depend only on the magnetic field which is the dominant scale in comparison to the scales prevalent in the thermal medium. However, for physical quark masses, it depends on both magnetic field and temperature in a low temperature and high magnetic field but the temperature dependence is very meager and becomes independent of the temperature beyond a certain temperature and magnetic field. With the above mentioned ingredients, the potential between heavy quark (Q) and anti-quark (anti Q) is obtained in a hot QCD medium in the presence of a strong magnetic field by correcting both short- and long-range components of the potential in the real-time formalism. It is found that the long-range part of the quarkonium potential is affected much more by magnetic field as compared to the short-range part. This observation facilitates us to estimate the magnetic field beyond which the potential will be too weak to bind Q anti Q together. For example, the J/ψ is dissociated at eB ∝ 10 m{sub π}{sup 2} and Υ is dissociated at eB ∝ 100 m{sub π}{sup 2} whereas its excited states, ψ{sup '} and Υ{sup '} are dissociated at smaller magnetic field eB = m{sub π}{sup 2}, 13 m{sub π}{sup 2}, respectively. (orig.)

  16. Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum

    Science.gov (United States)

    Fujiwara, Yoshihisa; Tomishige, Masahiko; Itoh, Yasuhiro; Fujiwara, Masao; Shibata, Naho; Kosaka, Toshikazu; Hosoya, Hiroshi; Tanimoto, Yoshifumi

    2006-05-01

    Effect of horizontal strong static magnetic field on swimming behaviour of Paramecium caudatum was studied by using a superconducting magnet. Around a centre of a round vessel, random swimming at 0 T and aligned swimming parallel to the magnetic field (MF) of 8 T were observed. Near a wall of the vessel, however, swimming round and round along the wall at 0 T and aligned swimming of turning at right angles upon collision with the wall, which was remarkable around 1-4 T, were detected. It was experimentally revealed that the former MF-induced parallel swimming at the vessel centre was caused physicochemically by the parallel magnetic orientation of the cell itself. From magnetic field dependence of the extent of the orientation, the magnetic susceptibility anisotropy (χ ∥-χ ⊥) was first obtained to be 3.4× 10-23 emu cell-1 at 298 K for Paramecium caudatum. The orientation of the cell was considered to result from the magnetic orientation of the cell membrane. On the other hand, although mechanisms of the latter swimming near the vessel wall regardless of the absence and presence of the magnetic field are unclear at present, these experimental results indicate that whether the cell exists near the wall alters the magnetic field effect on the swimming in the horizontal magnetic field.

  17. Superconductivity from magnetic fluctuations in FeTe{sub 1-x}Se{sub x}-feedback of double stripe magnetism on itinerant spin excitations

    Energy Technology Data Exchange (ETDEWEB)

    Mardani, Masoud; Moessner, Roderich [Max Planck Institute for the Physics of Complex Systems, Dresden (Germany); Knolle, Johannes [TCM Group, Cavendish Laboratory, University of Cambridge (United Kingdom); Eremin, Ilya [Institute for Theoretical Physics III, Ruhr-Universitaet Bochum (Germany)

    2015-07-01

    Iron-chalcogenide superconductors exhibit an unusual double stripe antiferromagnetic parent phase with ordering vector Q{sub AF} = (π/2,π/2) (in the one iron unit cell). In addition, magnetic excitations in optimally doped systems are peaked at momenta Q{sub SF} = (π,0)/(0,π), which is in contrast to most other families of iron-based superconductors. There, both the magnetic order of the parent compounds and the magnetic fluctuations in the superconducting state have the same momentum Q{sub SF}, which is taken as a strong argument in favor of spin-fluctuation induced superconductivity. Here, we model iron-chalcogenides as a system of itinerant electrons coupled to localized electrons responsible for the double stripe magnetism. We study the feedback of this unusual magnetic order on the itinerant spin excitations at Q{sub SF} and show that they increase with decreasing magnetism. We make connection to recent INS experiments and reproduce qualitatively the behavior of magnetic excitations in FeTe{sub 1-x}Se{sub x} from x=0 towards x=0.4.

  18. One-electron atomic-molecular ions containing lithium in a strong magnetic field

    International Nuclear Information System (INIS)

    Olivares-Pilon, H; Turbiner, A V; Vieyra, J C Lopez; Baye, D

    2010-01-01

    The one-electron lithium-containing Coulomb systems of atomic type Li 2+ and molecular type Li 5+ 2 , LiHe 4+ and LiH 3+ are studied in the presence of a strong magnetic field B ≤ 10 7 au in a non-relativistic framework. They are considered at the Born-Oppenheimer approximation of zero order (infinitely massive centres) within the parallel configuration (molecular axis parallel to the magnetic field). The variational and Lagrange-mesh methods are employed, complementing each other. It is demonstrated that the molecular systems LiH 3+ , LiHe 4+ and Li 5+ 2 can exist for sufficiently strong magnetic fields B ∼> 10 4 au and that Li 5+ 2 can even be stable at magnetic fields typical of magnetars.

  19. Viscosity of two-dimensional strongly coupled dusty plasma modified by a perpendicular magnetic field.

    Science.gov (United States)

    Feng, Yan; Lin, Wei; Murillo, M S

    2017-11-01

    Transport properties of two-dimensional (2D) strongly coupled dusty plasmas have been investigated in detail, but never for viscosity with a strong perpendicular magnetic field; here, we examine this scenario using Langevin dynamics simulations of 2D liquids with a binary Yukawa interparticle interaction. The shear viscosity η of 2D liquid dusty plasma is estimated from the simulation data using the Green-Kubo relation, which is the integration of the shear stress autocorrelation function. It is found that, when a perpendicular magnetic field is applied, the shear viscosity of 2D liquid dusty plasma is modified substantially. When the magnetic field is increased, its viscosity increases at low temperatures, while at high temperatures its viscosity diminishes. It is determined that these different variational trends of η arise from the different behaviors of the kinetic and potential parts of the shear stress under external magnetic fields.

  20. The thermodynamic spin magnetization of strongly correlated 2d electrons in a silicon inversion layer

    OpenAIRE

    Prus, O.; Yaish, Y.; Reznikov, M.; Sivan, U.; Pudalov, V.

    2002-01-01

    A novel method invented to measure the minute thermodynamic spin magnetization of dilute two dimensional fermions is applied to electrons in a silicon inversion layer. Interplay between the ferromagnetic interaction and disorder enhances the low temperature susceptibility up to 7.5 folds compared with the Pauli susceptibility of non-interacting electrons. The magnetization peaks in the vicinity of the density where transition to strong localization takes place. At the same density, the suscep...

  1. Axion production from Landau quantization in the strong magnetic field of magnetars

    Science.gov (United States)

    Maruyama, Tomoyuki; Balantekin, A. Baha; Cheoun, Myung-Ki; Kajino, Toshitaka; Mathews, Grant J.

    2018-04-01

    We utilize an exact quantum calculation to explore axion emission from electrons and protons in the presence of the strong magnetic field of magnetars. The axion is emitted via transitions between the Landau levels generated by the strong magnetic field. The luminosity of axions emitted by protons is shown to be much larger than that of electrons and becomes stronger with increasing matter density. Cooling by axion emission is shown to be much larger than neutrino cooling by the Urca processes. Consequently, axion emission in the crust may significantly contribute to the cooling of magnetars. In the high-density core, however, it may cause heating of the magnetar.

  2. Chiral soliton lattice and charged pion condensation in strong magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Brauner, Tomáš [Faculty of Science and Technology, University of Stavanger,N-4036 Stavanger (Norway); Yamamoto, Naoki [Department of Physics, Keio University,Yokohama 223-8522 (Japan)

    2017-04-21

    The Chiral Soliton Lattice (CSL) is a state with a periodic array of topological solitons that spontaneously breaks parity and translational symmetries. Such a state is known to appear in chiral magnets. We show that CSL also appears as a ground state of quantum chromodynamics at nonzero chemical potential in a magnetic field. By analyzing the fluctuations of the CSL, we furthermore demonstrate that in strong but achievable magnetic fields, charged pions undergo Bose-Einstein condensation. Our results, based on a systematic low-energy effective theory, are model-independent and fully analytic.

  3. Off-specular polarized neutron reflectometry study of magnetic dots with a strong shape anisotropy

    CERN Document Server

    Temst, K; Moshchalkov, V V; Bruynseraede, Y; Fritzsche, H; Jonckheere, R

    2002-01-01

    We have measured the off-specular polarized neutron reflectivity of a regular array of rectangular magnetic polycrystalline Co dots, which were prepared by a combination of electron-beam lithography, molecular beam deposition, and lift-off processes. The dots have a length-to-width ratio of 4:1 imposing a strong shape anisotropy. The intensity of the off-specular satellite reflection was monitored as a function of the magnetic field applied parallel to the rows of dots and in the plane of the sample, allowing us to analyze the magnetization-reversal process using the four spin-polarized cross sections. (orig.)

  4. Study of Strong Magnetic Fields Using Parametric Instability in a Magnetised Plasma

    Science.gov (United States)

    Ivanov, V. V.; Maximov, A. V.; Anderson, A. A.; Bauer, B. S.; Yates, K.

    2014-10-01

    Generation of strong magnetic fields with a strength of 10--50 MG plays a key role in some recent conceptions for controlled fusion. We suggest a laser method for measuring the local magnetic field, B > 10 MG, based on the parametric decay of the laser radiation to ω/2 and 3/2 ω harmonics which are generated in the area with the electron density of a quarter of the critical plasma density. Spectral components of parametric harmonics carry a signature of both the plasma temperature and strong magnetic field. A two-plasmon decay of laser radiation was studied in a magnetized plasma at the 1 MA pulsed power Zebra facility at the University of Nevada, Reno. Dense magnetized plasma with a magnetic field of 1--3 MG was created by the 1MA current flowing in the metal rod 0.7--2 mm in diameter. Radiation from the narrowband laser with intensity >1014 W/cm2 was focused on the surface plasma. Spectrum of the backscattering 3/2 ω harmonic included ``red'' and ``blue'' shifted components. Large 2-3 nm shifts of spectral components was identified with laser heating of plasma. Components with a small 0.1 nm spectral shift of may be linked to the magnetic field. Work was supported by the DOE Grant DE-SC0008824 and DOE/NNSA UNR Grant DE-FC52-06NA27616.

  5. Structure of dysprosium monotartrate in aqueous solution according to magnetic double refraction and molecular mechanics data

    International Nuclear Information System (INIS)

    Vul'fson, S.G.; Chevela, V.V.; Matveev, S.N.; Sal'nikov, Yu.I.; Sarvarova, N.N.; Semenov, V.Eh.

    1992-01-01

    The molar constant of magnetic double refraction of disprosium monotartrate DyH 2 L + (H 4 L - tartric acid) had been determined by pH-metry and magnetic double refraction methods. The structures of ligand and hydrate environments of dysprosium in DyH 2 L + were modelated by the method of molecular mechanics (the model of Dashevskii-Plyamovatov). The theoretical molar constants of magnetic double refraction calculated using the molecular mechanics data had been compared with experimental ones, the most probable models of dysprosium environment have been determined

  6. The determination of the rotation period and magnetic field geometry of the strongly magnetic roAp star HD 154708

    NARCIS (Netherlands)

    Hubrig, S.; Mathys, G.; Kurtz, D.W.; Schöller, M.; Elkin, V.G.; Henrichs, H.F.

    2009-01-01

    We obtained 13 spectropolarimetric observations of the strongly magnetic rapidly oscillating Ap star HD 154708 over 3 months with the multimode instrument FORS 1, installed at the 8-m Kueyen telescope of the Very Large Telescope. These observations have been used for the determination of the

  7. Description of the magnetic properties of strongly correlated disordered solid solutions in the coherent potential approximation

    Science.gov (United States)

    Korotin, M. A.; Skorikov, N. A.

    2015-06-01

    A method for electronic structure calculations of strongly correlated materials based on the coherent potential approximation is formulated and implemented. Method is applied for investigation of the electronic structure and local magnetic moments of the strongly correlated systems with d- and f-electrons: NiO-ZnO solid solution, nonstoichiometric perovskite LaMnO3-x, doped compound TiO2:Fe, and rare-earth transition-metal intermetallic compound GdNi2:Mn.

  8. Atomic structure dependence of nonsequential double ionization of He, Ne and Ar in strong laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Jesus, V L B de; Feuerstein, B; Zrost, K; Fischer, D; Rudenko, A; Afaneh, F; Schroeter, C D; Moshammer, R; Ullrich, J [Max-Planck-Institut fuer Kernphysik, D-69029 Heidelberg (Germany)

    2004-04-28

    The ion momentum spectra for nonsequential double ionization of rare gases (He, Ne and Ar) in 23 fs 795 nm laser pulses were measured in the intensity range 0.075-1.25 PW cm{sup -2}. In the studies published, confusing differences in the shape of momentum distributions among different targets are consistently explained within a recollision scenario: excitation during recollision plus subsequent field ionization, not implemented in most theoretical approaches, evidently plays a decisive role for He and Ar nonsequential double ionization whereas it plays only a minor role for Ne. (letter to the editor)

  9. Double atom ionization by multicharged ions and strong electromagnetic field: correlation effects in a continuous spectrum

    International Nuclear Information System (INIS)

    Presnyakov, L.P.; Uskov, D.B.

    1997-01-01

    The nonstationary theory of double ionization of two-electron atoms in collisions with multicharged ions or under the impact of intensive electromagnetic field is developed. The approach, making it possible to study both problems by uniform method, is formulated. The two-electron wave function of continuous spectrum, accounting for interaction of electrons with atomic nucleus, external ionizer and between themselves is obtained. The calculation results on the helium atoms double ionization by multicharged ions is a good quantitative agreement with available experimental data

  10. Exotic magnetism and spin-orbit-assisted Mott insulating state in a 3 d -5 d double perovskite

    Science.gov (United States)

    Cavichini, A. S.; Orlando, M. T.; Depianti, J. B.; Passamai, J. L.; Damay, F.; Porcher, F.; Granado, E.

    2018-02-01

    The magnetic structure of Ca2MnReO6 double perovskite is investigated by neutron powder diffraction and bulk magnetization, showing dominant noncollinear Mn magnetic moments [4.35 (7 ) μB] that are orthogonally aligned with the small Re moments [0.22 (4 ) μB] . Ab initio electronic structure calculations show that the strong spin-orbit coupling for Re 5 d electrons combined with a relatively modest on-site Coulomb repulsion (UeffR e≳0.6 eV) is sufficient to render this material insulating. This is a rare example of spin-orbit-assisted Mott insulator outside the realm of iridates, with remarkable magnetic properties.

  11. Luminosity and cooling of highly magnetized white dwarfs: suppression of luminosity by strong magnetic fields

    Science.gov (United States)

    Bhattacharya, Mukul; Mukhopadhyay, Banibrata; Mukerjee, Subroto

    2018-03-01

    We investigate the luminosity and cooling of highly magnetized white dwarfs with electron-degenerate cores and non-degenerate surface layers where cooling occurs by diffusion of photons. We find the temperature and density profiles in the surface layers or envelope of white dwarfs by solving the magnetostatic equilibrium and photon diffusion equations in a Newtonian framework. We also obtain the properties of white dwarfs at the core-envelope interface, when the core is assumed to be practically isothermal. With the increase in magnetic field, the interface temperature increases whereas the interface radius decreases. For a given age of the white dwarf and for fixed interface radius or interface temperature, we find that the luminosity decreases significantly from about 10-6 L⊙ to 10-9 L⊙ as the magnetic field strength increases from about 109 G to 1012 G at the interface and hence the envelope. This is remarkable because it argues that magnetized white dwarfs are fainter and can be practically hidden in an observed H-R diagram. We also find the cooling rates corresponding to these luminosities. Interestingly, the decrease in temperature with time, for the fields under consideration, is not found to be appreciable.

  12. Critical point in the QCD phase diagram for extremely strong background magnetic fields

    International Nuclear Information System (INIS)

    Endrödi, Gergely

    2015-01-01

    Lattice simulations have demonstrated that a background (electro)magnetic field reduces the chiral/deconfinement transition temperature of quantum chromodynamics for eB<1 GeV 2 . On the level of observables, this reduction manifests itself in an enhancement of the Polyakov loop and in a suppression of the light quark condensates (inverse magnetic catalysis) in the transition region. In this paper, we report on lattice simulations of 1+1+1-flavor QCD at an unprecedentedly high value of the magnetic field eB=3.25 GeV 2 . Based on the behavior of various observables, it is shown that even at this extremely strong field, inverse magnetic catalysis prevails and the transition, albeit becoming sharper, remains an analytic crossover. In addition, we develop an algorithm to directly simulate the asymptotically strong magnetic field limit of QCD. We find strong evidence for a first-order deconfinement phase transition in this limiting theory, implying the presence of a critical point in the QCD phase diagram. Based on the available lattice data, we estimate the location of the critical point.

  13. Consequence of total lepton number violation in strongly magnetized iron white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Belyaev, V.B. [Bogolyubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Ricci, P. [Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, I-50019 Sesto Fiorentino (Firenze) (Italy); Šimkovic, F. [Department of Nuclear Physics and Biophysics, Comenius University, Mlynská dolina F1, SK-842 15, Bratislava (Slovakia); Bogolyubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, Dubna 141980 (Russian Federation); Adam, J.; Tater, M. [Institute of Nuclear Physics ASCR, CZ-250 68 Řež (Czech Republic); Truhlík, E., E-mail: truhlik@ujf.cas.cz [Institute of Nuclear Physics ASCR, CZ-250 68 Řež (Czech Republic)

    2015-05-15

    The influence of a neutrinoless electron to positron conversion on a cooling of strongly magnetized iron white dwarfs is studied. It is shown that they can be good candidates for soft gamma-ray repeaters and anomalous X-ray pulsars.

  14. Numerical analysis of blood flow in realistic arteries subjected to strong non-uniform magnetic fields

    NARCIS (Netherlands)

    Kenjeres, S.

    2008-01-01

    The paper reports on a comprehensive mathematical model for simulations of blood flow under the presence of strong non-uniform magnetic fields. The model consists of a set of Navier–Stokes equations accounting for the Lorentz and magnetisation forces, and a simplified set of Maxwell’s equations

  15. Quantum magnetism in strongly interacting one-dimensional spinor Bose systems

    DEFF Research Database (Denmark)

    Salami Dehkharghani, Amin; Volosniev, A. G.; Lindgren, E. J.

    2015-01-01

    -range inter-species interactions much larger than their intra-species interactions and show that they have novel energetic and magnetic properties. In the strongly interacting regime, these systems have energies that are fractions of the basic harmonic oscillator trap quantum and have spatially separated...

  16. Study of rare earth local moment magnetism and strongly correlated phenomena in various crystal structures

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Tai [Iowa State Univ., Ames, IA (United States)

    2016-12-17

    Benefiting from unique properties of 4f electrons, rare earth based compounds are known for offering a versatile playground for condensed matter physics research as well as industrial applications. This thesis focuses on three specific examples that further explore the rare earth local moment magnetism and strongly correlated phenomena in various crystal structures.

  17. Equation of state of strange quark matter in a strong magnetic field

    International Nuclear Information System (INIS)

    Isayev, A.A.; Yang, J.

    2012-01-01

    Thermodynamic properties of strange quark matter (SQM) in strong magnetic fields H up to 10 20 G are considered at zero temperature within the MIT bag model. The effects of the pressure anisotropy, exhibiting in the difference between the pressures along and perpendicular to the field direction, become essential at H>H t h , with the estimate 10 17 t h 18 G. The longitudinal pressure vanishes in the critical field H c , which can be somewhat less or larger than 10 18 G, depending on the total baryon number density and bag pressure. As a result, the longitudinal instability occurs in strongly magnetized SQM. The appearance of such instability sets the upper bound on the magnetic field strength which can be reached in the interior of a neutron star with the quark core. The longitudinal and transverse pressures as well as the anisotropic equation of state of SQM are determined under the conditions relevant for the cores of magnetars

  18. Probing spin correlations with phonons in the strongly frustrated magnet ZnCr2O4.

    Science.gov (United States)

    Sushkov, A B; Tchernyshyov, O; Ratcliff, W; Cheong, S W; Drew, H D

    2005-04-08

    The spin-lattice coupling plays an important role in strongly frustrated magnets. In ZnCr2O4, an excellent realization of the Heisenberg antiferromagnet on the pyrochlore network, a lattice distortion relieves the geometrical frustration through a spin-Peierls-like phase transition at T(c)=12.5 K. Conversely, spin correlations strongly influence the elastic properties of a frustrated magnet. By using infrared spectroscopy and published data on magnetic specific heat, we demonstrate that the frequency of an optical phonon triplet in ZnCr2O4 tracks the nearest-neighbor spin correlations above T(c). The splitting of the phonon triplet below T(c) provides a way to measure the spin-Peierls order parameter.

  19. Spin polarization in high density quark matter under a strong external magnetic field

    DEFF Research Database (Denmark)

    Tsue, Yasuhiko; Da Providência, João; Providência, Constança

    2016-01-01

    In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor-type interact......In high density quark matter under a strong external magnetic field, possible phases are investigated by using the two-flavor Nambu-Jona-Lasinio (NJL) model with tensor-type four-point interaction between quarks, as well as the axial-vector-type four-point interaction. In the tensor...... phase appears in the wide range of the quark chemical potential. In both the interactions, the quark mass in zero and small chemical potential regions increases which indicates that the chiral symmetry breaking is enhanced, namely the magnetic catalysis occurs....

  20. Optical investigation of the strong spin-orbit-coupled magnetic semimetal YbMnBi2

    Science.gov (United States)

    Chaudhuri, Dipanjan; Cheng, Bing; Yaresko, Alexander; Gibson, Quinn D.; Cava, R. J.; Armitage, N. P.

    2017-08-01

    Strong spin-orbit coupling (SOC) can result in ground states with nontrivial topological properties. The situation is even richer in magnetic systems where the magnetic ordering can potentially have strong influence over the electronic band structure. The class of A MnBi2 (A = Sr, Ca) compounds are important in this context as they are known to host massive Dirac fermions with strongly anisotropic dispersion, which is believed to be due to the interplay between strong SOC and magnetic degrees of freedom. We report the optical conductivity of YbMnBi2, a newly discovered member of this family and a proposed Weyl semimetal (WSM) candidate with broken time reversal symmetry. Together with density functional theory (DFT) band-structure calculations, we show that the complex conductivity can be interpreted as the sum of an intraband Drude response and interband transitions. We argue that the canting of the magnetic moments that has been proposed to be essential for the realization of the WSM in an otherwise antiferromagnetically ordered system is not necessary to explain the optical conductivity. We believe our data is explained qualitatively by the uncanted magnetic structure with a small offset of the chemical potential from strict stochiometry. We find no definitive evidence of a bulk Weyl nodes. Instead, we see signatures of a gapped Dirac dispersion, common in other members of A MnBi2 family or compounds with similar 2D network of Bi atoms. We speculate that the evidence for a WSM seen in ARPES arises through a surface magnetic phase. Such an assumption reconciles all known experimental data.

  1. First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

    Science.gov (United States)

    Berdyugina, S. V.; Harrington, D. M.; Kuzmychov, O.; Kuhn, J. R.; Hallinan, G.; Kowalski, A. F.; Hawley, S. L.

    2017-09-01

    We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have detected the surface magnetic field as circularly polarized signatures in the 819 nm sodium lines when an active emission region faced the Earth. Modeling Stokes profiles of these lines reveals the effective temperature of 2800 K and log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on evolutionary tracks as a young brown dwarf with the mass of 55+/- 4{M}{{J}} and age of 22 ± 4 Myr. Its magnetic field is at least 5.1 kG and covers at least 11% of the visible hemisphere. The active region topology recovered using line profile inversions comprises hot plasma loops with a vertical stratification of optical and radio emission sources. These loops rotate with the dwarf in and out of view causing periodic emission bursts. The magnetic field is detected at the base of the loops. This is the first time that we can quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG surface magnetic field and solve the puzzle of their driving mechanism. This is also the coolest known dwarf with such a strong surface magnetic field. The young age of LSR J1835+3259 implies that it may still maintain a disk, which may facilitate bursts via magnetospheric accretion, like in higher-mass T Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs and hot Jupiters.

  2. Centrifugal pumping during Czochralski silicon growth with a strong, non-uniform, axisymmetric magnetic field

    Science.gov (United States)

    Khine, Y. Y.; Walker, J. S.

    1996-08-01

    Centrifugal pumping flows are produced in the melt by the rotations of crystal and crucible during the Czochralski growth of silicon crystals. This paper treats the centrifugal pumping effects with a steady, strong, non-uniform axisymmetric magnetic field. We consider a family of magnetic fields ranging from a uniform axial field to a "cusp" field, which has a purely radial field at the crystal-melt interface and free surface. We present the numerical solutions for the centrifugal pumping flows as the magnetic field is changed continuously from a uniform axial field to a cusp one, and for arbitrary Hartmann number. Since the perfect alignment between the local magnetic field vector and the crystal-melt interface or free surface is not likely, we also investigate the effects of a slight misalignment.

  3. Sound absorption in a field of a strong electromagnetic wave in a quantizied magnetic field

    International Nuclear Information System (INIS)

    Chajkovskij, I.A.

    1974-01-01

    A coefficient of sound absorption GAMMA in a semiconductor and semi-metal in the quantized magnetic field is calculated for a system exposed to a field of strong electromagnetic radiation. The cases E parallel H and E orthogonal H are considered. Along with the already known strong oscillations of sound absorption in magnetic fields, the absorption spectrum GAMMAsub(par) and GAMMAsub(orth) shows new oscillations representing a manifestation of the quasi-energetic electron spectrum in the field of a strong electromagnetic wave. The oscillation height at E parallel H is modulated by the electromagnetic field. It is shown that the ratio GAMMAsub(par)/GAMMAsub(orth) allows the determination of the effective mass of the carriers

  4. Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Tao-Chung; Lai, Shih-Ping [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Zhang, Qizhou; Girart, Josep M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States); Qiu, Keping [School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023 (China); Liu, Hauyu B., E-mail: chingtaochung@gmail.com [European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany)

    2017-04-01

    We present Submillimeter Array 880 μ m dust polarization observations of six massive dense cores in the DR21 filament. The dust polarization shows complex magnetic field structures in the massive dense cores with sizes of 0.1 pc, in contrast to the ordered magnetic fields of the parsec-scale filament. The major axes of the massive dense cores appear to be aligned either parallel or perpendicular to the magnetic fields of the filament, indicating that the parsec-scale magnetic fields play an important role in the formation of the massive dense cores. However, the correlation between the major axes of the cores and the magnetic fields of the cores is less significant, suggesting that during the core formation, the magnetic fields below 0.1 pc scales become less important than the magnetic fields above 0.1 pc scales in supporting a core against gravity. Our analysis of the angular dispersion functions of the observed polarization segments yields a plane-of-sky magnetic field strength of 0.4–1.7 mG for the massive dense cores. We estimate the kinematic, magnetic, and gravitational virial parameters of the filament and the cores. The virial parameters show that the gravitational energy in the filament dominates magnetic and kinematic energies, while the kinematic energy dominates in the cores. Our work suggests that although magnetic fields may play an important role in a collapsing filament, the kinematics arising from gravitational collapse must become more important than magnetic fields during the evolution from filaments to massive dense cores.

  5. ON MULTIPLE RECONNECTION X-LINES AND TRIPOLAR PERTURBATIONS OF STRONG GUIDE MAGNETIC FIELDS

    International Nuclear Information System (INIS)

    Eriksson, S.; Gosling, J. T.; Lapenta, G.; Newman, D. L.; Goldman, M. V.; Phan, T. D.; Lavraud, B.; Khotyaintsev, Yu. V.; Carr, C. M.; Markidis, S.

    2015-01-01

    We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field B M   which is almost four times as strong as the reversing field B L . The novel tripolar field consists of two narrow regions of depressed B M , with an observed 7%–14% ΔB M magnitude relative to the external field, which are found adjacent to a wide region of enhanced B M within the exhaust. A stronger reversing field is associated with each B M depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated ΔB M /ΔX N over the normal width ΔX N between a B M minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field

  6. Bound-state β decay of a neutron in a strong magnetic field

    International Nuclear Information System (INIS)

    Kouzakov, Konstantin A.; Studenikin, Alexander I.

    2005-01-01

    The β decay of a neutron into a bound (pe - ) state and an antineutrino in the presence of a strong uniform magnetic field (B > or approx. 10 13 G) is considered. The β decay process is treated within the framework of the standard model of weak interactions. A Bethe-Salpeter formalism is employed for description of the bound (pe - ) system in a strong magnetic field. For the field strengths 10 13 18 G the estimate for the ratio of the bound-state decay rate w b and the usual (continuum-state) decay rate w c is derived. It is found that in such strong magnetic fields w b /w c ∼0.1-0.4. This is in contrast to the field-free case, where w b /w c ≅4.2x10 -6 [J. N. Bahcall, Phys. Rev. 124, 495 (1961); L. L. Nemenov, Sov. J. Nucl. Phys. 15, 582 (1972); X. Song, J. Phys. G: Nucl. Phys. 13, 1023 (1987)]. The dependence of the ratio w b /w c on the magnetic field strength B exhibits a logarithmiclike behavior. The obtained results can be important for applications in astrophysics and cosmology

  7. Experimental study of transport of relativistic electron beams in strong magnetic mirror field

    Science.gov (United States)

    Sakata, Shohei; Kondo, Kotaro; Bailly-Grandvaux, Mathiu; Bellei, Claudio; Santos, Joao; Firex Project Team

    2015-11-01

    Relativistic electron beams REB produced by ultra high intense laser pulses have generally a large divergence angle that results in degradation of energy coupling between the REB and a fuel core in the fast ignition scheme. Guiding and focusing of the REB by a strong external magnetic field was proposed to achieve high efficiency. We investigated REB transport through 50 μm or 250 μm thick plastic foils CuI doped under external magnetic fields, in magnetic mirror configurations of 1.2 or 4 mirror ratio. The experiment was carried out at the GEKKO XII and LFEX laser facility. Spatial pattern of the REB was measured by coherent transition radiation and/or Cu Ka x ray emission from the rear surface of the foil targets. Strong collimation of the REB by the external magnetic field was observed with 50 μm thick plastic targets, while the REB scattered in 250 μm thick targets. The experimental results are compared with computer simulations to understand the physical mechanisms of the REB transport in the external magnetic field. This work is supported by NIFS (Japan), MEXT/JSPS KAKENHI (Japan), JSPS Fellowship (Japan), ANR (France) and COST (Europe).

  8. Quantum Femtosecond Magnetism: Phase Transition in Step with Light in a Strongly Correlated Manganese Oxide

    Science.gov (United States)

    Wang, Jigang

    2014-03-01

    Research of non-equilibrium phase transitions of strongly correlated electrons is built around addressing an outstanding challenge: how to achieve ultrafast manipulation of competing magnetic/electronic phases and reveal thermodynamically hidden orders at highly non-thermal, femtosecond timescales? Recently we reveal a new paradigm called quantum femtosecond magnetism-photoinduced femtosecond magnetic phase transitions driven by quantum spin flip fluctuations correlated with laser-excited inter-atomic coherent bonding. We demonstrate an antiferromagnetic (AFM) to ferromagnetic (FM) switching during about 100 fs laser pulses in a colossal magneto-resistive manganese oxide. Our results show a huge photoinduced femtosecond spin generation, measured by magnetic circular dichroism, with photo-excitation threshold behavior absent in the picosecond dynamics. This reveals an initial quantum coherent regime of magnetism, while the optical polarization/coherence still interacts with the spins to initiate local FM correlations that compete with the surrounding AFM matrix. Our results thus provide a framework that explores quantum non-equilibrium kinetics to drive phase transitions between exotic ground states in strongly correlated elecrons, and raise fundamental questions regarding some accepted rules, such as free energy and adiabatic potential surface. This work is in collaboration with Tianqi Li, Aaron Patz, Leonidas Mouchliadis, Jiaqiang Yan, Thomas A. Lograsso, Ilias E. Perakis. This work was supported by the National Science Foundation (contract no. DMR-1055352). Material synthesis at the Ames Laboratory was supported by the US Department of Energy-Basic Energy Sciences (contract no. DE-AC02-7CH11358).

  9. Linear theory of a cold relativistic beam in a strongly magnetized finite-geometry plasma

    International Nuclear Information System (INIS)

    Gagne, R.R.J.; Shoucri, M.M.

    1976-01-01

    The linear theory of a finite-geometry cold relativistic beam propagating in a cold homogeneous finite-geometry plasma, is investigated in the case of a strongly magnetized plasma. The beam is assumed to propagate parallel to the external magnetic field. It is shown that the instability which takes place at the Cherenkov resonance ωapprox. =k/subz/v/subb/ is of the convective type. The effect of the finite geometry on the instability growth rate is studied and is shown to decrease the growth rate, with respect to the infinite geometry, by a factor depending on the ratio of the beam-to-plasma radius

  10. Transport coefficients of InSb in a strong magnetic field

    International Nuclear Information System (INIS)

    Nakamura, Hiroaki; Ikeda, Kazuaki; Yamaguchi, Satarou

    1998-02-01

    Improvement of a superconducting magnet system makes induction of a strong magnetic field easier. This fact gives us a possibility of energy conversion by the Nernst effect. As the first step to study the Nernst element, we measured the conductivity, the Hall coefficient, the thermoelectric power and the Nernst coefficient of the InSb, which is one of candidates of the Nernst elements. From this experiment, it is concluded that the Nernst coefficient is smaller than the theoretical values. On the other hand, the conductivity, the Hall coefficient and the thermoelectric power has the values expected by the theory. (author)

  11. Magnetic and resonant X-ray scattering investigations of strongly correlated electron systems

    International Nuclear Information System (INIS)

    Paolasini, L.; Bergevin, F. de

    2008-01-01

    Resonant X-ray scattering is a method which combines high-Q resolution X-ray elastic diffraction and atomic core-hole spectroscopy for investigating electronic and magnetic long-range ordered structures in condensed matter. During recent years the development of theoretical models to describe resonant X-ray scattering amplitudes and the evolution of experimental techniques, which include the control and analysis of linear photon polarization and the introduction of extreme environment conditions such as low temperatures, high magnetic field and high pressures, have opened a new field of investigation in the domain of strongly correlated electron systems. (authors)

  12. Transmesocolic double gastro-enteric fistulas due to ingestion of 28 magnets

    Directory of Open Access Journals (Sweden)

    Adrian Surd

    2018-05-01

    Full Text Available Introduction: Accidental ingestion of magnetic foreign bodies has become more common due to increased availability of objects and toys with magnetic elements. The majority of them traverse the gastrointestinal system spontaneously without complication. However, ingestion of multiple magnets may require surgical resolution. Magnet ingestion usually does not cause serious complications, but in case of multiple magnet ingestion or ingestion of magnet and a metal object, it could cause intestinal obstruction, fistula formation or even perforation. Case report: We report case of a transmesocolic double gastro-enteric fistula formation following ingestion of 28 small magnets in a 17 months old boy. No history of foreign body ingestion could be obtained from parents therefore the patient was treated conservatively in a pediatric clinic for vomiting, dehydration, upper respiratory tract infection and suspicion of upper digestive tract bleeding. After 48 h he was sent in our clinic for surgical evaluation. Intraoperatively double transmesocolic gastro-enteric fistula was found. After separation of de gastric and enteral walls, resection of gastric wall and intestinal segment containing the two perforations was performed, followed by gastric suture in two layers and entero-enteric anastomosis. A total of 28 magnets were removed from the stomach and small intestine. Conclusion: Single magnet ingestion is treated as non-magnetic foreign body. Multiple magnet ingestion should be closely monitored and surgical approach could be the best option to prevent or to cure its complications. Keywords: Ingestion, Magnetic foreign body, Multiple magnets, Intestinal fistula, Children

  13. Binary and Recoil Collisions in Strong Field Double Ionization of Helium

    International Nuclear Information System (INIS)

    Staudte, A.; Villeneuve, D. M.; Corkum, P. B.; Ruiz, C.; Becker, A.; Schoeffler, M.; Schoessler, S.; Meckel, M.; Doerner, R.; Zeidler, D.; Weber, Th.

    2007-01-01

    We have investigated the correlated momentum distribution of both electrons from nonsequential double ionization of helium in a 800 nm, 4.5x10 14 W/cm 2 laser field. Using very high resolution coincidence techniques, we find a so-far unobserved fingerlike structure in the correlated electron momentum distribution. The structure can be interpreted as a signature of the microscopic dynamics in the recollision process. We identify features corresponding to the binary and recoil lobe in field-free (e,2e) collisions. This interpretation is supported by analyzing ab initio solutions of a fully correlated three-dimensional helium model

  14. Strong double K-K transfer channel in near symmetric collision of Si+Ar at intermediate velocity range

    Energy Technology Data Exchange (ETDEWEB)

    Dhal, B.B.; Tiwari, U.; Tandon, P.N. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Bombay 400 005 (India); Tribedi, L.C. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Bombay 400 005 (India). E-mail: lokesh at tifr.res.in; Lee, T.G.; Lin, C.D. [J R Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506 (United States); Gulyas, L. [Nuclear Data Center, Japan Atomic Energy Research Institute, Tokai, Naka, Ibaraki 319-1195 (Japan)

    2000-03-14

    We present a combined study of single and double K-K electron transfer cross sections along with the single and double K-shell ionization of Ar induced by Si projectiles in the energy range 0.9-4.0 MeV u{sup -1}. The charge-state dependence of the normal and hypersatellite x-rays was used to derive the cross sections for the one- and two-electron processes, respectively. The enhancement in the fluorescence yields due to multiple vacancies was measured from the energy shifts and intensity ratios of the characteristic x-ray lines to derive K-shell vacancy production cross sections from x-ray production cross sections. The ratio of double to single K-K transfer cross sections is found to be quite large for this nearly symmetric collision system, whereas the ratio of double to single ionization cross sections is quite small. The measured single K-K transfer cross sections are reproduced very well by the two-centre close-coupling calculations whereas the double K-K transfer data are underestimated by the theory based on the independent-electron approximation (IEA). The K-shell ionization cross sections are found to deviate strongly from the calculations based on the continuum distorted wave eikonal initial state (CDW-EIS) and ECPSSR models. The CDW-EIS calculations along with the IEA model grossly underestimate the double ionization cross sections. It is stressed that in the case of two-electron processes the independent-electron model breaks down and the possible role of correlations between K-electrons is discussed. (author)

  15. Abnormal pulmonary vein drainage in upper right lobe associated with double aortic arch : magnetic resonance angiography

    International Nuclear Information System (INIS)

    Busto, M.; Dolz, J.L.; Capdevilla, A.; Castanon, M.; Mulet, J.

    1997-01-01

    We present the magnetic resonance (MR) and magnetic resonance angiography (MRA) findings in a case of abnormal pulmonary vein drainage from upper right lobe to superior vena cava, associated with double aortic arch, in a six-month-old boy. (Author) 9 refs

  16. Formation of a double-decker magnetic flux rope in the sigmoidal solar active region 11520

    International Nuclear Information System (INIS)

    Cheng, X.; Ding, M. D.; Zhang, J.; Guo, Y.; Sun, X. D.; Wang, Y. M.; Kliem, B.; Deng, Y. Y.

    2014-01-01

    In this paper, we address the formation of a magnetic flux rope (MFR) that erupted on 2012 July 12 and caused a strong geomagnetic storm event on July 15. Through analyzing the long-term evolution of the associated active region observed by the Atmospheric Imaging Assembly and the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, it is found that the twisted field of an MFR, indicated by a continuous S-shaped sigmoid, is built up from two groups of sheared arcades near the main polarity inversion line a half day before the eruption. The temperature within the twisted field and sheared arcades is higher than that of the ambient volume, suggesting that magnetic reconnection most likely works there. The driver behind the reconnection is attributed to shearing and converging motions at magnetic footpoints with velocities in the range of 0.1-0.6 km s –1 . The rotation of the preceding sunspot also contributes to the MFR buildup. Extrapolated three-dimensional non-linear force-free field structures further reveal the locations of the reconnection to be in a bald-patch region and in a hyperbolic flux tube. About 2 hr before the eruption, indications of a second MFR in the form of an S-shaped hot channel are seen. It lies above the original MFR that continuously exists and includes a filament. The whole structure thus makes up a stable double-decker MFR system for hours prior to the eruption. Eventually, after entering the domain of instability, the high-lying MFR impulsively erupts to generate a fast coronal mass ejection and X-class flare; while the low-lying MFR remains behind and continuously maintains the sigmoidicity of the active region.

  17. The D sup - centre in a quantum well in the presence of parallel electric and strong magnetic fields

    CERN Document Server

    Monozon, B S

    2003-01-01

    An analytical approach to the problem of a negatively charged donor in an infinitely deep quantum well (QW) in the presence of parallel electric and strong magnetic external fields both directed perpendicular to the heteroplanes is developed. The double adiabatic approximation is employed. The dependences of the binding energy on the field strengths, the width of the well and the position of the impurity within the well are derived in explicit form. The effect of the inversion of the electric field is investigated. It is shown that the combined potential acting on the 'outer' electron resembles that of a double QW. When the levels associated with the two effective QWs anticross, a resonant structure arises. The explicit dependence of the resonant splitting on the width of the QW, the strength of the electric field and the position of the impurity are obtained. Using the parameters associated with the GaAs QW, estimates of the inversion shift of the binding energy and the frequency of the emitted resonant radi...

  18. Drag force in strongly coupled { N }=4 supersymmetric Yang–Mills plasma in a magnetic field

    Science.gov (United States)

    Zhang, Zi-qiang; Ma, Ke; Hou, De-fu

    2018-02-01

    Applying AdS/CFT correspondence, we study the effect of a constant magnetic field { B } on the drag force associated with a heavy quark moving through a strongly-coupled { N }=4 supersymmetric Yang–Mills plasma. The quark is considered moving transverse and parallel to { B }. It is shown that for transverse case, the drag force is linearly dependent on { B } in all regions, while for parallel case, the drag force increases monotonously with increasing { B } and also reveals a linear behavior in the regions of strong { B }. In addition, we find that { B } has a more important effect in the transverse case than for the parallel.

  19. Thermal conductivity of magnetic insulators with strong spin-orbit coupling

    Science.gov (United States)

    Stamokostas, Georgios; Lapas, Panteleimon; Fiete, Gregory A.

    We study the influence of spin-orbit coupling on the thermal conductivity of various types of magnetic insulators. In the absence of spin-orbit coupling and orbital-degeneracy, the strong-coupling limit of Hubbard interactions at half filling can often be adequately described in terms of a pure spin Hamiltonian of the Heisenberg form. However, in the presence of spin-orbit coupling the resulting exchange interaction can become highly anisotropic. The effect of the atomic spin-orbit coupling, taken into account through the effect of magnon-phonon interactions and the magnetic order and excitations, on the lattice thermal conductivity of various insulating magnetic systems is studied. We focus on the regime of low temperatures where the dominant source of scattering is two-magnon scattering to one-phonon processes. The thermal current is calculated within the Boltzmann transport theory. We are grateful for financial support from NSF Grant DMR-0955778.

  20. Analysis and Design of Double-sided Air core Linear Servo Motor with Trapezoidal Permanent Magnets

    DEFF Research Database (Denmark)

    Zhang, Yuqiu; Yang, Zilong; Yu, Minghu

    2011-01-01

    In order to reduce the thrust ripple of linear servo system, a double-sided air core permanent magnet linear servo motor with trapezoidal shape permanent magnets (TDAPMLSM) is proposed in this paper. An analytical model of the motor for predicting the magnetic field in the air-gap at no......-load is introduced. This model is derived based on the equivalent magnetization intensity method, and its accuracy is validated by using the results obtained from the finite-element method. The key dimensions that affect the air-gap magnetic field are analyzed based on the analytical model, and the design...

  1. Threshold for strong thermal dephasing in periodically poled KTP in external cavity frequency doubling

    DEFF Research Database (Denmark)

    Lundeman, Jesper Holm; Jensen, Ole Bjarlin; Andersen, Peter E.

    2009-01-01

    We present a measurement series of the efficiency of periodically poled KTP used for second-harmonic generation in an external phase-locked cavity. Due to the high absorption (0.01 cm^−1) in the PPKTP crystal at the pump wavelength a strong thermal dephasing of the periodically poled grating...

  2. Ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a hot strongly magnetized plasma

    OpenAIRE

    Liu, Wei; Hsu, Scott C.

    2010-01-01

    We present results from three-dimensional ideal magnetohydrodynamic simulations of unmagnetized dense plasma jet injection into a uniform hot strongly magnetized plasma, with the aim of providing insight into core fueling of a tokamak with parameters relevant for ITER and NSTX (National Spherical Torus Experiment). Unmagnetized dense plasma jet injection is similar to compact toroid injection but with much higher plasma density and total mass, and consequently lower required injection velocit...

  3. Limiting and Fedosov's Currents of a Strongly Magnetized Electron Beam in Asymmetric Transportation Channels

    Science.gov (United States)

    Goikhman, M. B.; Gromov, A. V.; Kovalev, N. F.; V. Palitsin, A.

    2016-12-01

    We consider the properties of thin-walled, strongly magnetized electron beams in closed evacuated transportation channels with arbitrary cross sections of the channel and the electron beam. Explicit precise formulas are obtained for the limiting and Fedosov's currents of such electron beams. The found relationships allow one to explain many observed phenomena and can serve as a basis for verification of the results of more complicated calculations.

  4. Nanosized helical magnetic domains in strongly frustrated Fe3PO4O3

    Science.gov (United States)

    Ross, K. A.; Bordelon, M. M.; Terho, G.; Neilson, J. R.

    2015-10-01

    Fe3PO4O3 forms a noncentrosymmetric lattice structure (space group R 3 m ) comprising triangular motifs of Fe3 + coupled by strong antiferromagnetic interactions (| ΘC W|>900 K). Neutron diffraction from polycrystalline samples shows that strong frustration eventually gives way to an ordered helical incommensurate structure below TN = 163 K, with the helical axis in the hexagonal a b plane and a modulation length to ˜86 Å. The magnetic structure consists of an unusual needlelike correlation volume that extends past 900 Å along the hexagonal c axis but is limited to ˜70 Å in the a b plane, despite the three-dimensional nature of the magnetic sublattice topology. The small in-plane correlation length, which persists to at least T =TN/40 , indicates a robust blocking of long-range order of the helical magnetic structure, and therefore stable domain walls, or other defect spin textures, must be abundant in Fe3PO4O3 . Temperature-dependent neutron powder diffraction reveals small negative thermal expansion below TN. No change in lattice symmetry is observed on cooling through TN, as revealed by high-resolution synchrotron x-ray diffraction. The previously reported reduced moment of the Fe3 + ions (S =5 /2 ), μ ˜4.2 μB , is confirmed here through magnetization studies of a magnetically diluted solid solution series of compounds, Fe(3 -x )GaxPO4O3 , and is consistent with the refined magnetic moment from neutron diffraction 4.14(2) μB. We attribute the reduced moment to a modified spin density distribution arising from ligand charge transfer in this insulating oxide.

  5. Unexpected strong magnetism of Cu doped single-layer MoS₂ and its origin.

    Science.gov (United States)

    Yun, Won Seok; Lee, J D

    2014-05-21

    The magnetism of the 3d transition-metal (TM) doped single-layer (1L) MoS2, where the Mo atom is partially replaced by the 3d TM atom, is investigated using the first-principles density functional calculations. In a series of 3d TM doped 1L-MoS2's, the induced spin polarizations are negligible for Sc, Ti, and Cr dopings, while the induced spin polarizations are confirmed for V, Mn, Fe, Co, Ni, Cu, and Zn dopings and the systems become magnetic. Especially, the Cu doped system shows unexpectedly strong magnetism although Cu is nonmagnetic in its bulk state. The driving force is found to be a strong hybridization between Cu 3d states and 3p states of neighboring S, which results in an extreme unbalanced spin-population in the spin-split impurity bands near the Fermi level. Finally, we also discuss further issues of the Cu induced magnetism of 1L-MoS2 such as investigation of additional charge states, the Cu doping at the S site instead of the Mo site, and the Cu adatom on the layer (i.e., 1L-MoS2).

  6. Numerical analysis of blood flow in realistic arteries subjected to strong non-uniform magnetic fields

    International Nuclear Information System (INIS)

    Kenjeres, Sasa

    2008-01-01

    The paper reports on a comprehensive mathematical model for simulations of blood flow under the presence of strong non-uniform magnetic fields. The model consists of a set of Navier-Stokes equations accounting for the Lorentz and magnetisation forces, and a simplified set of Maxwell's equations (Biot-Savart/Ampere's law) for treating the imposed magnetic fields. The relevant hydrodynamic and electromagnetic properties of human blood were taken from the literature. The model is then validated for different test cases ranging from a simple cylindrical geometry to real-life right-coronary arteries in humans. The time-dependency of the wall-shear-stress for different stenosis growth rates and the effects of the imposed strong non-uniform magnetic fields on the blood flow pattern are presented and analysed. It is concluded that an imposed non-uniform magnetic field can create significant changes in the secondary flow patterns, thus making it possible to use this technique for optimisations of targeted drug delivery

  7. [DNA extraction from decomposed tissue by double-digest and magnetic beads methods].

    Science.gov (United States)

    Yang, Dian; Liu, Chao; Liu, Hong

    2011-12-01

    To study the effect of the double-digest and magnetic beads method for DNA extraction from 3 types of decomposed tissues. DNA of cartilages, nails and joint capsule in 91 highly decomposed corpses which had not been extracted by common magnetic beads method, were prepared with the double-digest and magnetic beads methods, and quantified with Quantifiler kit, followed by amplification with Sinofiler kit or Minifiler kit. DNA concentration extracted from the 91 highly decomposed cartilages, nails and joint capsule samples was 0-0.225 ng/microL. Sixty-two samples whose DNA concentration were more than 0.020 ng/microL had obtained 9 or more STR loci successfully. The detection rate was 68.13%. The successful rate of STR genotyping for the 3 types of decomposed tissues can be significantly improved by the double-digest and magnetic beads methods.

  8. Anomaly disturbances of the magnetic fields before the strong earthquake in Japan on March 11, 2011

    Directory of Open Access Journals (Sweden)

    Masashi Hayakawa

    2012-04-01

    Full Text Available

    One of the strongest earthquakes, with magnitude M 8.9, occurred at the sea bottom near to the east coast of Japan on March 11, 2011. This study is devoted to the investigation of anomaly disturbances in the main magnetic field of the Earth and in ultra-low frequency magnetic variations (F <10 Hz observed before this earthquake. Secular variations of the main geomagnetic field were investigated using three-component 1-h data from three magnetic observatories over the 11-year period of January 1, 2000, to January 31, 2011. The Esashi and Mizusawa magnetic stations are situated northwest of the earthquake epicenter, at distances of around 170 km to 200 km, and the Kakioka observatory is situated southwest of the earthquake epicenter, at a distance of about 300 km. During this period, there were four local anomalies in the secular variations. The last anomaly was the biggest, which began around 3 years prior to the earthquake moment. All of the anomalies can be most distinctly recognized, in the form of differences in the corresponding magnetic components at these remote magnetic stations. For investigations of the ultra-low frequency magnetic field disturbances, three-component 1-s data at two magnetic stations (Kakioka and Uchiura were used. The Uchiura station is situated 119 km south of Kakioka, at a distance of about 420 km from the earthquake epicenter. Data from the time interval of February 18, 2011 to March 10, 2011 (only at night-time: 01:00 to 04:00 local time were investigated in a wide frequency range. In the frequency range of 0.033 Hz to 0.01 Hz, there was the clearest anomaly, seen as a decrease in the correlation coefficients of the corresponding magnetic components at these two stations, from February 22, 2011. Differences in the Z components showed an increase, and became positive after this date. This might suggest that the ultra-low frequency lithospheric source appeared north of the Kakioka station. Outside this specified

  9. Two regimes in conductivity and the Hall coefficient of underdoped cuprates in strong magnetic fields.

    Science.gov (United States)

    Gor'kov, L P; Teitel'baum, G B

    2014-01-29

    We address recent experiments shedding light on the energy spectrum of under and optimally doped cuprates at temperatures above the superconducting transition. Angle resolved photoemission reveals coherent excitation only near nodal points on parts of the 'bare' Fermi surface known as the Fermi arcs. The question debated in the literature is whether the small normal pocket, seen via quantum oscillations, exists at higher temperatures or forms below a charge order transition in strong magnetic fields. Assuming the former case as a possibility, expressions are derived for the resistivity and the Hall coefficient (in weak and strong magnetic fields) with both types of carriers participating in the transport. There are two regimes. At higher temperatures (at a fixed field) electrons are dragged by the Fermi arcs' holes. The pocket being small, its contribution to conductivity and the Hall coefficient is negligible. At lower temperatures electrons decouple from holes behaving as a Fermi gas in the magnetic field. As the mobility of holes on the arcs decreases in strong fields with a decrease of temperature, below a crossover point the pocket electrons prevail, changing the sign of the Hall coefficient in the low temperature limit. Such behavior finds its confirmation in recent high-field experiments.

  10. Improvement of Energy Density in Single Stator Interior Permanent Magnet Using Double Stator Topology

    Directory of Open Access Journals (Sweden)

    Raja Nor Firdaus

    2014-01-01

    Full Text Available The paper presents the energy density improvement using magnetic circuit analysis of the interior permanent magnet motor. The leakage flux from the conventional structure is improved with modified magnetic circuit to improve the energy and thereby the torque value. This is approached with a double stator structure design. The proposed structure is investigated with two design variations, namely, the double stator with thin pole shoe and the double stator with thick pole shoe motors. Variations in the mechanical parameters of the all the developed models are analyzed through the finite element analysis tool. In all investigations the magnetic source is fixed in both the permanent magnet volume and coil magnetomotive force, respectively, as 400 mm3 per each pole and 480 Ampere turns per pole. From the analysis the best fit magnetic structure based on the torque characteristics is derived and is fabricated for the same volume as that of the conventional structure for performance evaluations. It is found out that there is improvement on the motor constant square density for the proposed improved magnetic circuit through the best fit double stator with thick pole shoe by about 83.66% greater than that of the conventional structure.

  11. A strong magnetic field around the supermassive black hole at the centre of the Galaxy.

    Science.gov (United States)

    Eatough, R P; Falcke, H; Karuppusamy, R; Lee, K J; Champion, D J; Keane, E F; Desvignes, G; Schnitzeler, D H F M; Spitler, L G; Kramer, M; Klein, B; Bassa, C; Bower, G C; Brunthaler, A; Cognard, I; Deller, A T; Demorest, P B; Freire, P C C; Kraus, A; Lyne, A G; Noutsos, A; Stappers, B; Wex, N

    2013-09-19

    Earth's nearest candidate supermassive black hole lies at the centre of the Milky Way. Its electromagnetic emission is thought to be powered by radiatively inefficient accretion of gas from its environment, which is a standard mode of energy supply for most galactic nuclei. X-ray measurements have already resolved a tenuous hot gas component from which the black hole can be fed. The magnetization of the gas, however, which is a crucial parameter determining the structure of the accretion flow, remains unknown. Strong magnetic fields can influence the dynamics of accretion, remove angular momentum from the infalling gas, expel matter through relativistic jets and lead to synchrotron emission such as that previously observed. Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre and show that the pulsar's unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission--from radio to X-ray wavelengths--from the black hole.

  12. Strong uniaxial magnetic anisotropy in Co films on highly ordered grating-like nanopatterned Ge surfaces

    Science.gov (United States)

    Alam Mollick, Safiul; Singh, Ranveer; Kumar, Mohit; Bhattacharyya, Satyaranjan; Som, Tapobrata

    2018-03-01

    We present a systematic investigation on uniaxial magnetic anisotropy (UMA) in Co thin films induced by high aspect ratio nanopatterned anisotropic substrates. Self-organized long grating-like nanostructures, with extreme regularities, are fabricated on Ge surfaces using Au-ion implantation at room temperature. Subsequently deposition of Co films are carried out on the same at two different angles. Magneto-optical Kerr effect measurements show strong UMA in Co films grown on ion-patterned Ge substrates, fabricated under different ion fluences, along and perpendicular to the direction of the patterns (long grating-like nanostructures). Magnetic force microscopy measurements under different externally applied magnetic fields reveal an easy domain wall motion when the field is applied along the grating-like nanostructures. On the other hand, high amplitude grating-like nanostructures hinder the spin rotation when the field is applied along the hard axis. The present study will be useful for magnetic recording media and ultra-small magnetic field sensors.

  13. Two-photon annihilation of thermal pairs in strong magnetic fields

    Science.gov (United States)

    Baring, Matthew G.; Harding, Alice K.

    1992-01-01

    The annihilation spectrum of pairs with 1-D thermal distributions in the presence of a strong magnetic field is calculated. Numerical analysis of the spectrum are performed for mildly relativistic temperatures and for different angles of emission with respect to field lines. Teragauss magnetic fields are assumed so that conditions are typical of gamma ray burst and pulsar environments. The spectra at each viewing angle reveal asymmetric line profiles that are signatures of the magnetic broadening and red shifting of the line: these asymmetries are more prominent for small viewing angles. Thermal Doppler broadening tends to dominate in the right wing of the line and obscures the magnetic broadening more at high temperatures and smaller viewing angles. This angular dependence of the line asymmetry may prove a valuable diagnostic tool. For low temperatures and magnetic field strengths, useful analytic expressions are presented for the line width, and also for the annihilation spectrum at zero viewing angle. The results presented find application in gamma ray burst and pulsar models, and may prove very helpful in deducing field strengths and temperatures of the emission regions of these objects from line observations made by Compton GRO and future missions.

  14. Strong post-midnight Equatorial Ionospheric Anomaly and Equatorial spread F Observations during magnetically quiet period

    Science.gov (United States)

    Moldwin, M. B.; Yizengaw, E.; Sahai, Y.

    2008-12-01

    Post sunset equatorial ionospheric irregularities, especially during magnetically active periods, have been a subject of many studies. The most prominent irregularities often observed right after sunset are the resurgence of the equatorial ionospheric anomaly (EIA) and equatorial spread F (ESF). It is well understood and documented that pre-reversal enhancement, due to the ionospheric conductivity gradient at the dusk, is one of the prime triggering mechanisms for the post-sunset irregularities in the equatorial region. However, less attention has been given to the equatorial irregularities (EIA and ESF) that often occur in post-midnight, especially during magnetically quiet periods. It has been suggested that the primary process responsible for the dramatic post-midnight ESF during magnetically active periods is the change in magnitude and direction of the usual equatorial electric field. Earlier studies speculated that during magnetically active post-midnight periods the change in electric field direction from westward to eastward for a short intervals cause an upward E × B drift, resulting in increased h'F and decreased electron densities at the magnetic equator. Individual scans of Jicamarca vertical drift also often observe significant upward drift during post-midnight periods. We present a case of post-midnight strong equatorial ionospheric anomaly during a magnetically quiet (Kp < 3) period using TOPEX altimeter TEC data. Simultaneously, the ionosonde station at S.J. Campos (23.2°S, 45.9°W; dip lat. 17.6°S) observed strong ESF and unusual h'F height rise during post-midnight period, where TOPEX detected strong EIA. At the same time ROCSAT-1 and DMSP satellites also clearly show existence of EIA during post-midnight period at their orbiting altitude. The former satellite also detected post-midnight in situ density irregularities (such as bubbles) at the same time as strong EIA and ESF. The questions here are what triggers these post-midnight equatorial

  15. Mechanically Strong Double Network Photocrosslinked Hydrogels from N, N-Dimethylacrylamide and Glycidyl Methacrylated Hyaluronan

    Science.gov (United States)

    Weng, Lihui; Gouldstone, Andrew; Wu, Yuhong; Chen, Weiliam

    2008-01-01

    Hyaluronan (HA) is a natural polysaccharide abundant in biological tissues and it can be modified to prepare biomaterials. In this work, HA modified with glycidyl methacrylate was photocrosslinked to form the first network (PHA), and then a series of highly porous PHA/N, N-dimethylacrylamide (DAAm) hydrogels (PHA/DAAm) with high mechanical strength were obtained by incorporating a second network of photocrosslinked DAAm into PHA network. Due to synergistic effect produced by double network (DN) structure, despite containing 90% of water, the resulting PHA/DAAm hydrogel showed a compressive modulus and a fracture stress over 0.5 MPa and 5.2 MPa, respectively. Compared to the photocrosslinked hyaluronan single network hydrogel, which is generally very brittle and fractures easily, the PHA/DAAm hydrogels are ductile. Mouse dermal fibroblast was used as a model cell line to validate in vitro non-cytotoxicity of the PHA/DAAm hydrogels. Cells deposited extracellular matrix on the surface of these hydrogels and this was confirmed by positive staining of Type I collagen by Sirius Red. The PHA/DAAm hydrogels were also resistant to biodegradation and largely retained their excellent mechanical properties even after two months of co-culturing with fibroblasts. PMID:18272215

  16. Origin of neutron magnetic scattering in antisite-disordered Sr2FeMoO6 double perovskites

    International Nuclear Information System (INIS)

    Sanchez, D.; Alonso, J.A.; Garcia-Hernandez, M.; Martinez-Lope, M.J.; Martinez, J.L.; Mellerga ring rd, Anders

    2002-01-01

    Antisite disordering in Sr 2 FeMoO 6 double perovskites (containing Mo atoms at Fe positions, and vice versa) has recently been shown to have a dramatic influence in their magnetic and magnetotransport properties. In the present paper, two polycrystalline Sr 2 FeMoO 6 samples showing different degrees of antisite disorder (a nominally 'ordered' sample with ∼70% of cationic ordering and a nominally 'disordered' sample with ∼18% of cationic ordering) have been examined by magnetic measurements and neutron powder diffraction techniques in the 15-500 K temperature range. Our main finding is that the 'disordered' sample exhibits a strong magnetic scattering (noticeable even at 500 K), comparable to that displayed by the 'ordered' one below T C =415 K. For the 'disordered' sample, the magnetic scattering exhibited on low-angle Bragg positions, is not to be ascribed to a (nonexistent) ferrimagnetic ordering: our results suggest that it originates upon naturally occurring groups of Fe cations in which strong antiferromagnetic (AFM) Fe-O-Fe superexchange interactions are promoted, similar to those existing in the LaFeO 3 perovskite. These Fe groups are not magnetically isolated, but coupled by virtue of Fe-O-Mo AFM interactions, which maintain the long-range coherence of this AFM structure. Susceptibility measurements confirm the presence of AFM interactions below 770 K

  17. Electron cyclotron maser instability (ECMI in strong magnetic guide field reconnection

    Directory of Open Access Journals (Sweden)

    R. A. Treumann

    2017-08-01

    Full Text Available The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is

  18. Electron cyclotron maser instability (ECMI) in strong magnetic guide field reconnection

    Science.gov (United States)

    Treumann, Rudolf A.; Baumjohann, Wolfgang

    2017-08-01

    The ECMI model of electromagnetic radiation from electron holes is shown to be applicable to spontaneous magnetic reconnection. We apply it to reconnection in strong current-aligned magnetic guide fields. Such guide fields participate only passively in reconnection, which occurs in the antiparallel components to both sides of the guide-field-aligned current sheets with current carried by kinetic Alfvén waves. Reconnection generates long (the order of hundreds of electron inertial scales) electron exhaust regions at the reconnection site X point, which are extended perpendicular to the current and the guide fields. Exhausts contain a strongly density-depleted hot electron component and have properties similar to electron holes. Exhaust electron momentum space distributions are highly deformed, exhibiting steep gradients transverse to both the reconnecting and guide fields. Such properties suggest application of the ECMI mechanism with the fundamental ECMI X-mode emission beneath the nonrelativistic guide field cyclotron frequency in localized source regions. An outline of the mechanism and its prospects is given. Potential applications are the kilometric radiation (AKR) in auroral physics, solar radio emissions during flares, planetary emissions and astrophysical scenarios (radiation from stars and compact objects) involving the presence of strong magnetic fields and field-aligned currents. Drift of the exhausts along the guide field maps the local field and plasma properties. Escape of radiation from the exhaust and radiation source region still poses a problem. The mechanism can be studied in 2-D particle simulations of strong guide field reconnection which favours 2-D, mapping the deformation of the electron distribution perpendicular to the guide field, and using it in the numerical calculation of the ECMI growth rate. The mechanism suggests also that reconnection in general may become a source of the ECMI with or without guide fields. This is of particular

  19. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  20. Femtosecond switching of magnetism via strongly correlated spin-charge quantum excitations.

    Science.gov (United States)

    Li, Tianqi; Patz, Aaron; Mouchliadis, Leonidas; Yan, Jiaqiang; Lograsso, Thomas A; Perakis, Ilias E; Wang, Jigang

    2013-04-04

    The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.

  1. He2+ molecular ion and the He- atomic ion in strong magnetic fields

    Science.gov (United States)

    Vieyra, J. C. Lopez; Turbiner, A. V.

    2017-08-01

    We study the question of existence, i.e., stability with respect to dissociation of the spin-quartet permutation- and reflection-symmetric 4(-3) +g (Sz=-3 /2 ,M =-3 ) state of the (α α e e e ) Coulomb system: the He2 + molecular ion, placed in a magnetic field 0 ≤B ≤10 000 a.u. We assume that the α particles are infinitely massive (Born-Oppenheimer approximation of zero order) and adopt the parallel configuration, when the molecular axis and the magnetic field direction coincide, as the optimal configuration. The study of the stability is performed variationally with a physically adequate trial function. To achieve this goal, we explore several helium-containing compounds in strong magnetic fields, in particular; we study the spin-quartet ground state of the He- ion and the ground (spin-triplet) state of the helium atom, both for a magnetic field in 100 ≤B ≤10 000 a.u. The main result is that the He2 + molecular ion in the state 4(-3) +g is stable towards all possible decay modes for magnetic fields B ≳120 a .u . and with the magnetic field increase the ion becomes more tightly bound and compact with a cigar-type form of electronic cloud. At B =1000 a .u . , the dissociation energy of He2 + into He-+α is ˜702 eV and the dissociation energy for the decay channel to He +α +e is ˜729 eV , and both energies are in the energy window for one of the observed absorption features of the isolated neutron star 1E1207.4-5209.

  2. Effect of Strong Acid Functional Groups on Electrode Rise Potential in Capacitive Mixing by Double Layer Expansion

    KAUST Repository

    Hatzell, Marta C.

    2014-12-02

    © 2014 American Chemical Society. The amount of salinity-gradient energy that can be obtained through capacitive mixing based on double layer expansion depends on the extent the electric double layer (EDL) is altered in a low salt concentration (LC) electrolyte (e.g., river water). We show that the electrode-rise potential, which is a measure of the EDL perturbation process, was significantly (P = 10-5) correlated to the concentration of strong acid surface functional groups using five types of activated carbon. Electrodes with the lowest concentration of strong acids (0.05 mmol g-1) had a positive rise potential of 59 ± 4 mV in the LC solution, whereas the carbon with the highest concentration (0.36 mmol g-1) had a negative rise potential (-31 ± 5 mV). Chemical oxidation of a carbon (YP50) using nitric acid decreased the electrode rise potential from 46 ± 2 mV (unaltered) to -6 ± 0.5 mV (oxidized), producing a whole cell potential (53 ± 1.7 mV) that was 4.4 times larger than that obtained with identical electrode materials (from 12 ± 1 mV). Changes in the EDL were linked to the behavior of specific ions in a LC solution using molecular dynamics and metadynamics simulations. The EDL expanded in the LC solution when a carbon surface (pristine graphene) lacked strong acid functional groups, producing a positive-rise potential at the electrode. In contrast, the EDL was compressed for an oxidized surface (graphene oxide), producing a negative-rise electrode potential. These results established the linkage between rise potentials and specific surface functional groups (strong acids) and demonstrated on a molecular scale changes in the EDL using oxidized or pristine carbons.

  3. Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

    Science.gov (United States)

    Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

    2015-04-17

    Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole. Copyright © 2015, American Association for the Advancement of Science.

  4. Dynamics of liquid metal droplets and jets influenced by a strong axial magnetic field

    Science.gov (United States)

    Hernández, D.; Karcher, Ch

    2017-07-01

    Non-contact electromagnetic control and shaping of liquid metal free surfaces is crucial in a number of high-temperature metallurgical processes like levitation melting and electromagnetic sealing, among others. Other examples are the electromagnetic bending or stabilization of liquid metal jets that frequently occur in casting or fusion applications. Within this context, we experimentally study the influence of strong axial magnetic fields on the dynamics of falling metal droplets and liquid metal jets. GaInSn in eutectic composition is used as test melt being liquid at room temperature. In the experiments, we use a cryogen-free superconducting magnet (CFM) providing steady homogeneous fields of up to 5 T and allowing a tilt angle between the falling melt and the magnet axis. We vary the magnetic flux density, the tilt angle, the liquid metal flow rate, and the diameter and material of the nozzle (electrically conducting/insulating). Hence, the experiments cover a parameter range of Hartmann numbers Ha, Reynolds numbers Re, and Weber numbers We within 0 rotation ceases and the droplets are stretched in the field direction. Moreover, we observe that the jet breakup into droplets (spheroidization) is suppressed, and in the case of electrically conducting nozzles and tilt, the jets are bent towards the field axis.

  5. The mass limit of white dwarfs with strong magnetic fields in general relativity

    International Nuclear Information System (INIS)

    Wen De-Hua; Liu He-Lei; Zhang Xiang-Dong

    2014-01-01

    Recently, U. Das and B. Mukhopadhyay proposed that the Chandrasekhar limit of a white dwarf could reach a new high level (2.58M⊙) if a superstrong magnetic field were considered (Das U and Mukhopadhyay B 2013 Phys. Rev. Lett. 110 071102), where the structure of the strongly magnetized white dwarf (SMWD) is calculated in the framework of Newtonian theory (NT). As the SMWD has a far smaller size, in contrast with the usual expectation, we found that there is an obvious general relativistic effect (GRE) in the SMWD. For example, for the SMWD with a one Landau level system, the super-Chandrasekhar mass limit in general relativity (GR) is approximately 16.5% lower than that in NT. More interestingly, the maximal mass of the white dwarf will be first increased when the magnetic field strength keeps on increasing and reaches the maximal value M = 2.48M⊙ with B D = 391.5. Then if we further increase the magnetic fields, surprisingly, the maximal mass of the white dwarf will decrease when one takes the GRE into account. (geophysics, astronomy, and astrophysics)

  6. Photogeneration of neutrino and axions under stimulating effect of strong magnetic field

    CERN Document Server

    Skobelev, V V

    2001-01-01

    The processes of the neutrino and axions photoproduction on the gamma(Ze) -> gamma(nu nu-bar), gamma alpha nuclei, as well as the photon inelastic scattering on the gamma gamma -> gamma(nu nu-bar), gamma alpha photon are considered within the frames of the developed two-dimensional co-variant theory for calculating the matrix of the Feynman diagrams in the strong magnetic field. The contribution of the neutrino radiative photoproduction on the nuclei to the luminosity of the magnetic neutron stars on the early stages of their evolution may compete with the URCA-processes, because the matrix elements in the four-pole diagram depend linearly on the induction of B magnetic field by the B values approx 10 sup 3 -10 sup 4 B sub 0 (B sub 0 = m sub e sup 2 /|e| = 4.41 x 10 sup 1 sup 3 Gs). The evaluation of the axion mass upper boundary, compatible with other independent results, is obtained from the condition of the neutrino luminosity prevailing over the axion one at supposed temperature and magnetic field inducti...

  7. Electronic and Magnetic Properties of Double Perovskite Ca2CrSbO6

    International Nuclear Information System (INIS)

    Zhao Yuan; Ni Guangxin; Liu Huiping; Yi Lin

    2010-01-01

    First-principles calculations have been performed for the study of the electronic hand structure and ferromagnetic properties of double perovskite Ca 2 CrSbO 6 . The density of states, total energy, spin magnetic moment, and charge density were calculated and analyzed in details. It is found that Ca 2 CrSbO 6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is about 2.99μ B . The chromium contributes the most in the total magnetic moments. The results indicate that Ca 2 CrSbO 6 is half-metallic. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  8. Ideal magnetohydrodynamic simulations of low beta compact toroid injection into a hot strongly magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei [Los Alamos National Laboratory; Hsu, Scott [Los Alamos National Laboratory; Li, Hui [Los Alamos National Laboratory

    2009-01-01

    We present results from three-dimensional ideal magnetohydrodynamic simulations of low {beta} compact toroid (CT) injection into a hot strongly magnetized plasma, with the aim of providing insight into CT fueling of a tokamak with parameters relevant for ITER (International Thermonuclear Experimental Reactor). A regime is identified in terms of CT injection speed and CT-to-background magnetic field ratio that appears promising for precise core fueling. Shock-dominated regimes, which are probably unfavorable for tokamak fueling, are also identified. The CT penetration depth is proportional to the CT injection speed and density. The entire CT evolution can be divided into three stages: (1) initial penetration, (2) compression in the direction of propagation and reconnection, and (3) coming to rest and spreading in the direction perpendicular to injection. Tilting of the CT is not observed due to the fast transit time of the CT across the background plasma.

  9. Process γγ → νν-bar in a strong magnetic field

    International Nuclear Information System (INIS)

    Kuznetsov, A.V.; Mikheev, N.V.; Rumyantsev, D.A.

    2003-01-01

    The three-vertex loop amplitude in a strong magnetic field are analyzed in a general form by using the asymptotic behavior of the electron propagator in an external field. The process γγ → νν-bar is studied in terms of the scalar-vector-vector (SVV), pseudoscalar-vector-vector (PVV), vector-vector-vector (VVV), and axial-vector-vector-vector (AVV) combinations of couplings. It is shown that only in the case of the SVV combination does the amplitude grow linearly with increasing magnetic-field strength, the amplitudes evaluated with the other combinations of couplings (PVV, VVV, and AVV) featuring no linearly increasing terms. The process γγ → νν-bar is also studied within the left-right model, which is an extension of the Standard Model of electroweak interactions and which may involve an effective scalar ννee coupling. Possible astrophysical manifestations of this process are discussed

  10. Classical Spin Liquid Instability Driven By Off-Diagonal Exchange in Strong Spin-Orbit Magnets

    Science.gov (United States)

    Rousochatzakis, Ioannis; Perkins, Natalia B.

    2017-04-01

    We show that the off-diagonal exchange anisotropy drives Mott insulators with strong spin-orbit coupling to a classical spin liquid regime, characterized by an infinite number of ground states and Ising variables living on closed or open strings. Depending on the sign of the anisotropy, quantum fluctuations either fail to lift the degeneracy down to very low temperatures, or select noncoplanar magnetic states with unconventional spin correlations. The results apply to all 2D and 3D tricoordinated materials with bond-directional anisotropy and provide a consistent interpretation of the suppression of the x-ray magnetic circular dichroism signal reported recently for β -Li2IrO3 under pressure.

  11. Metal-insulator crossover in superconducting cuprates in strong magnetic fields

    International Nuclear Information System (INIS)

    Marchetti, P.A.; Su Zhaobin; Yu Lu

    2001-02-01

    The metal-insulator crossover of the in-plane resistivity upon temperature decrease, recently observed in several classes of cuprate superconductors, when a strong magnetic field suppresses the superconductivity, is explained using the U(1)xSU(2) Chern-Simons gauge field theory. The origin of this crossover is the same as that for a similar phenomenon observed in heavily underdoped cuprates without magnetic field. It is due to the interplay between the diffusive motion of the charge carriers and the 'peculiar' localization effect due to short-range antiferromagnetic order. We also calculate the in-plane transverse magnetoresistance which is in a fairly good agreement with available experimental data. (author)

  12. Resonance enhancement of two photon absorption by magnetically trapped atoms in strong rf-fields

    Science.gov (United States)

    Chakraborty, A.; Mishra, S. R.

    2018-01-01

    Applying a many mode Floquet formalism for magnetically trapped atoms interacting with a polychromatic rf-field, we predict a large two photon transition probability in the atomic system of cold 87Rb atoms. The physical origin of this enormous increase in the two photon transition probability is due to the formation of avoided crossings between eigen-energy levels originating from different Floquet sub-manifolds and redistribution of population in the resonant intermediate levels to give rise to the resonance enhancement effect. Other exquisite features of the studied atom-field composite system include the splitting of the generated avoided crossings at the strong field strength limit and a periodic variation of the single and two photon transition probabilities with the mode separation frequency of the polychromatic rf-field. This work can find applications to characterize properties of cold atom clouds in the magnetic traps using rf-spectroscopy techniques.

  13. The process γγ → νν-bar in a strong magnetic field

    International Nuclear Information System (INIS)

    Kuznetsov, A.V.; Mikheev, N.V.; Rumyantsev, D.A.

    2003-01-01

    A general analysis of the three-vertex loop amplitude in a strong magnetic field, based on the asymptotic form of the electron propagator in the field, is performed. In order to investigate the photon-neutrino process γγ → νν-bar, the vertex combinations of the scalar-vector-vector (SVV), pseudoscalar- vector-vector (PVV), 3-vector (VVV), and axial-vector-vector (AVV) types are considered. It is shown that only the SVV amplitude grows linearly with the magnetic-field strength, while in the other amplitudes, PVV, VVV, and AVV, the linearly growing terms are cancelled. The process γγ → νν-bar is investigated in the left-right-symmetric extension of the standard model of electroweak interaction, where the effective scalar ννee coupling could exist. Possible astrophysical manifestations of the considered process are discussed [ru

  14. Highly controlled orientation of CaBi4Ti4O15 using a strong magnetic field

    Science.gov (United States)

    Suzuki, Tohru S.; Kimura, Masahiko; Shiratsuyu, Kosuke; Ando, Akira; Sakka, Yoshio; Sakabe, Yukio

    2006-09-01

    The texture of feeble magnetic ceramics can be controlled by a strong magnetic field. When the magnetic susceptibility of the c axis is smaller than that of the other axes, the c axis aligns perpendicular to the magnetic field; however, the direction is randomly oriented on the plane perpendicular to the magnetic field. The authors demonstrate in this letter that a highly controlled texture in bismuth titanate, which has a c-axis susceptibility smaller than the other axes, can be achieved using a two-step magnetic field procedure. This highly controlled orientation is effective for improving the electromechanical coupling coefficient.

  15. Strong Coupling of Microwave Photons to Antiferromagnetic Fluctuations in an Organic Magnet

    Science.gov (United States)

    Mergenthaler, Matthias; Liu, Junjie; Le Roy, Jennifer J.; Ares, Natalia; Thompson, Amber L.; Bogani, Lapo; Luis, Fernando; Blundell, Stephen J.; Lancaster, Tom; Ardavan, Arzhang; Briggs, G. Andrew D.; Leek, Peter J.; Laird, Edward A.

    2017-10-01

    Coupling between a crystal of di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium radicals and a superconducting microwave resonator is investigated in a circuit quantum electrodynamics (circuit QED) architecture. The crystal exhibits paramagnetic behavior above 4 K, with antiferromagnetic correlations appearing below this temperature, and we demonstrate strong coupling at base temperature. The magnetic resonance acquires a field angle dependence as the crystal is cooled down, indicating anisotropy of the exchange interactions. These results show that multispin modes in organic crystals are suitable for circuit QED, offering a platform for their coherent manipulation. They also utilize the circuit QED architecture as a way to probe spin correlations at low temperature.

  16. An analytical method for the investigation of instability of a collisionless plasma in strong magnetic fields

    International Nuclear Information System (INIS)

    Zakharov, V.U.

    1993-01-01

    An analytical method for the investigation of special types of dispersion relations is presented. In particular, analysis of the propagation of small-amplitude hydromagnetic waves in a collisionless plasma in a strong magnetic field leads to such dispersion relations. The fifth-degree dispersion relation corresponding to a particular case is considered. The necessary stability condition for a steady state and conditions for the degeneration of small-amplitude waves are derived. A comparison with other methods for the analysis of similar dispersion relations is also presented. (author)

  17. Integrated electronic transport and thermometry at milliKelvin temperatures and in strong magnetic fields.

    Science.gov (United States)

    Samkharadze, N; Kumar, A; Manfra, M J; Pfeiffer, L N; West, K W; Csáthy, G A

    2011-05-01

    We fabricated a He-3 immersion cell for transport measurements of semiconductor nanostructures at ultra low temperatures and in strong magnetic fields. We have a new scheme of field-independent thermometry based on quartz tuning fork Helium-3 viscometry which monitors the local temperature of the sample's environment in real time. The operation and measurement circuitry of the quartz viscometer is described in detail. We provide evidence that the temperature of two-dimensional electron gas confined to a GaAs quantum well follows the temperature of the quartz viscometer down to 4 mK.

  18. Laser-driven platform for generation and characterization of strong quasi-static magnetic fields

    Czech Academy of Sciences Publication Activity Database

    Santos, J.J.; Bailly-Grandvaux, M.; Giuffrida, Lorenzo; Forestier-Colleoni, P.; Fujioka, H.; Zhang, Z.; Korneev, P.; Bouillaud, R.; Dorard, S.; Batani, D.; Chevrot, M.; Cross, J. E.; Crowston, R.; Dubois, J.L.; Gazave, J.; Gregori, G.; d'Humieres, E.; Hulin, S.; Ishihara, K.; Kojima, S.; Loyez, E.; Marqués, J.-R.; Morace, A.; Nicolaï, P.; Peyrusse, O.; Poyé, A.; Raffestin, D.; Ribolzi, J.; Roth, M.; Schaumann, G.; Serres, F.; Tikhonchuk, V.T.; Vacar, P.; Woolsey, N.

    2015-01-01

    Roč. 17, Aug (2015), s. 1-10, č. článku 083051. ISSN 1367-2630 R&D Projects: GA MŠk ED1.1.00/02.0061 Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061 Institutional support: RVO:68378271 Keywords : strong magnetic field * laser-driven coil targets * laser-plasma interaction Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.570, year: 2015

  19. Energy density and energy flow of surface waves in a strongly magnetized graphene

    Science.gov (United States)

    Moradi, Afshin

    2018-01-01

    General expressions for the energy density and energy flow of plasmonic waves in a two-dimensional massless electron gas (as a simple model of graphene) are obtained by means of the linearized magneto-hydrodynamic model and classical electromagnetic theory when a strong external magnetic field perpendicular to the system is present. Also, analytical expressions for the energy velocity, wave polarization, wave impedance, transverse and longitudinal field strength functions, and attenuation length of surface magneto-plasmon-polariton waves are derived, and numerical results are prepared.

  20. Spectrometer for external detection of magnetic and related double resonance

    International Nuclear Information System (INIS)

    Sagalyn, P.L.; Alexander, M.N.

    1977-01-01

    The patent relates to an improvement in nuclear magnetic resonance spectrometer apparatus. It consists of a spectrometer which utilizes separate materials containing, respectively, sample and detector spin systems as opposed to one in which the sample and detector spins are contained in the same single material

  1. Magnetotransport properties of Cr1−δTe thin films with strong perpendicular magnetic anisotropy

    Directory of Open Access Journals (Sweden)

    L. Zhou

    2017-12-01

    Full Text Available P-type ferromagnetic Cr1-δTe thin films with the Curie temperature of 170K were epitaxially grown on GaAs substrate. Low-temperature magnetotransport study reveals that the film has a strong perpendicular magnetic anisotropy (PMA and an anisotropic magnetoresistance (AMR ratio up to 8.1%. Furthermore, reduced anomalous Hall effect is observed at low temperatures in Cr1-δTe, suggesting the possible crossover of the contribution to AHE from the intrinsic mechanism to extrinsic skew scattering. Distinctive from conventional transition metal ferromagnets, the AMR ratio is also greatly suppressed at low temperatures. Our work demonstrates that epitaxial Cr1-δTe films are interesting platforms for studying the physics underlying the strong PMA and large AMR.

  2. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    Science.gov (United States)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-11-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular crystals for diffraction analyses has been the central focus for biochemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of the container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and sedimentation, as is achieved in "microgravity", researchers have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, formation of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. Whether this limited convection in a magnetic field will provide the environment for the growth of high quality crystals is still a matter of conjecture that our research will address. The approach exploits the variation of fluid magnetic susceptibility with concentration for this purpose and the convective damping is realized by appropriately

  3. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    Science.gov (United States)

    Clément, P.-Y.; Baraduc, C.; Ducruet, C.; Vila, L.; Chshiev, M.; Diény, B.

    2015-09-01

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  4. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Clément, P.-Y.; Baraduc, C.; Chshiev, M.; Diény, B.; Ducruet, C.; Vila, L.

    2015-01-01

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated

  5. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Clément, P.-Y.; Baraduc, C., E-mail: claire.baraduc@cea.fr; Chshiev, M.; Diény, B. [Univ. Grenoble Alpes, INAC-SPINTEC, F-38000 Grenoble (France); CNRS, INAC-SPINTEC, F-38000 Grenoble (France); CEA, INAC-SPINTEC, F-38000 Grenoble (France); Ducruet, C. [Crocus-Technology, 5, Place Robert Schuman, F-38054 Grenoble (France); Vila, L. [Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France and CEA, INAC-SP2M, F-38000 Grenoble (France)

    2015-09-07

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  6. Magnetic properties of double perovskite La2BMnO6 (B = Ni or Co) nanoparticles.

    Science.gov (United States)

    Mao, Yuanbing; Parsons, Jason; McCloy, John S

    2013-06-07

    Double perovskite La2BMnO6 (B = Ni and Co) nanoparticles with average particle size of ~50 nm were synthesized using a facile, environmentally friendly, and scalable molten-salt reaction at 700 °C in air. Their structural and morphological properties were characterized by X-ray diffraction and transmission electron microscopy. Their magnetic properties were evaluated and compared using dc magnetic M-T and M-H, and ac magnetic susceptibility versus frequency, temperature, and field for the first time. The dc magnetization curves show paramagnetic-ferromagnetic transitions at TC∼ 275 and 220 K for La2NiMnO6 (LNMO) and La2CoMnO6 (LCMO) nanoparticles, respectively. ac susceptibility revealed that the LCMO nanoparticles had a single magnetic transition indicative of Co(2+)-O(2-)-Mn(4+) ordering, whereas the LNMO nanoparticles showed more complex magnetic behaviors suggesting a re-entrant spin glass.

  7. Charge transfer of He2 + with H in a strong magnetic field

    Science.gov (United States)

    Liu, Chun-Lei; Zou, Shi-Yang; He, Bin; Wang, Jian-Guo

    2015-09-01

    By solving a time-dependent Schrödinger equation (TDSE), we studied the electron capture process in the He2 + +H collision system under a strong magnetic field in a wide projectile energy range. The strong enhancement of the total charge transfer cross section is observed for the projectile energy below 2.0 keV/u. With the projectile energy increasing, the cross sections will reduce a little and then increase again, compared with those in the field-free case. The cross sections to the states with different magnetic quantum numbers are presented and analyzed where the influence due to Zeeman splitting is obviously found, especially in the low projectile energy region. The comparison with other models is made and the tendency of the cross section varying with the projectile energy is found closer to that from other close coupling models. Project supported by the National Natural Science Foundation of China (Grants Nos. 11104017, 11025417, 11275029, and 11474032), the National Basic Research Programm of China (Grant No. 2013CB922200), and the Foundation for the Development of Science and Technology of the Chinese Academy of Engineering Physics (Grant Nos. 2014B09036 and 2013A0102005).

  8. Breakdown of the Chiral Anomaly in Weyl Semimetals in a Strong Magnetic Field

    Science.gov (United States)

    Kim, Pilkwang; Ryoo, Ji Hoon; Park, Cheol-Hwan

    2017-12-01

    The low-energy quasiparticles of Weyl semimetals are a condensed-matter realization of the Weyl fermions introduced in relativistic field theory. Chiral anomaly, the nonconservation of the chiral charge under parallel electric and magnetic fields, is arguably the most important phenomenon of Weyl semimetals and has been explained as an imbalance between the occupancies of the gapless, zeroth Landau levels with opposite chiralities. This widely accepted picture has served as the basis for subsequent studies. Here we report the breakdown of the chiral anomaly in Weyl semimetals in a strong magnetic field based on ab initio calculations. A sizable energy gap that depends sensitively on the direction of the magnetic field may open up due to the mixing of the zeroth Landau levels associated with the opposite-chirality Weyl points that are away from each other in the Brillouin zone. Our study provides a theoretical framework for understanding a wide range of phenomena closely related to the chiral anomaly in topological semimetals, such as magnetotransport, thermoelectric responses, and plasmons, to name a few.

  9. Impact of ultrafast demagnetization process on magnetization reversal in L10 FePt revealed using double laser pulse excitation

    Science.gov (United States)

    Shi, J. Y.; Tang, M.; Zhang, Z.; Ma, L.; Sun, L.; Zhou, C.; Hu, X. F.; Zheng, Z.; Shen, L. Q.; Zhou, S. M.; Wu, Y. Z.; Chen, L. Y.; Zhao, H. B.

    2018-02-01

    Ultrafast laser induced magnetization reversal in L10 FePt films with high perpendicular magnetic anisotropy was investigated using single- and double-pulse excitations. Single-pulse excitation beyond 10 mJ cm-2 caused magnetization (M) reversal at the applied fields much smaller than the static coercivity of the films. For double-pulse excitation, both coercivity reduction and reversal percentage showed a rapid and large decrease with the increasing time interval (Δt) of the two pulses in the range of 0-2 ps. In this Δt range, the maximum demagnetization (ΔMp) was also strongly attenuated, whereas the integrated demagnetization signals over more than 10 ps, corresponding to the average lattice heat effect, showed little change. These results indicate that laser induced M reversal in FePt films critically relies on ΔMp. Because ΔMp is determined by spin temperature, which is higher than lattice temperature, utilizing an ultrafast laser instead of a continuous-wave laser in laser-assisted M reversal may reduce the overall deposited energy and increase the speed of recording. The effective control of M reversal by slightly tuning the time delay of two laser pulses may also be useful for ultrafast spin manipulation.

  10. Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes

    Directory of Open Access Journals (Sweden)

    Jennifer Tang

    2015-09-01

    Full Text Available NIt was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains’ electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.

  11. Strong Static Magnetic Fields Increase the Gel Signal in Partially Hydrated DPPC/DMPC Membranes.

    Science.gov (United States)

    Tang, Jennifer; Alsop, Richard J; Schmalzl, Karin; Epand, Richard M; Rheinstädter, Maikel C

    2015-09-29

    NIt was recently reported that static magnetic fields increase lipid order in the hydrophobic membrane core of dehydrated native plant plasma membranes [Poinapen, Soft Matter 9:6804-6813, 2013]. As plasma membranes are multicomponent, highly complex structures, in order to elucidate the origin of this effect, we prepared model membranes consisting of a lipid species with low and high melting temperature. By controlling the temperature, bilayers coexisting of small gel and fluid domains were prepared as a basic model for the plasma membrane core. We studied molecular order in mixed lipid membranes made of dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) using neutron diffraction in the presence of strong static magnetic fields up to 3.5 T. The contribution of the hydrophobic membrane core was highlighted through deuterium labeling the lipid acyl chains. There was no observable effect on lipid organization in fluid or gel domains at high hydration of the membranes. However, lipid order was found to be enhanced at a reduced relative humidity of 43%: a magnetic field of 3.5 T led to an increase of the gel signal in the diffraction patterns of 5%. While all biological materials have weak diamagnetic properties, the corresponding energy is too small to compete against thermal disorder or viscous effects in the case of lipid molecules. We tentatively propose that the interaction between the fatty acid chains' electric moment and the external magnetic field is driving the lipid tails in the hydrophobic membrane core into a better ordered state.

  12. Switching behavior of double-decker single molecule magnets on a metal surface

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Yingshuang; Schwoebel, Joerg; Hoffmann, Germar; Brede, Jens; Wiesendanger, Roland [University of Hamburg, Hamburg (Germany); Dillulo, Andrew [Ohio University, Athens (United States); Klyatskaya, Svetlana [Karlsruhe Institute of Technology, Karlsruhe (Germany); Ruben, Mario [Karlsruhe Institute of Technology, Karlsruhe (Germany); Universite de Strasbourg, Strasbourg (France)

    2011-07-01

    Single molecule magnets (SMM) are most promising materials for spin based molecular electronics. Due to their large magnetic anisotropy stabilized by inside chemical bonds, SMM can potentially be used for information storage at the single molecule level. For applications, it is of importance to adsorb the SMM onto surfaces and to study their subsequent conformational, electronic and magnetic properties. We have investigated the adsorption behavior of Tb and Dy based double-decker SMM on an Ir(111) surface with low temperature scanning tunneling microscopy and spectroscopy. It is found that Tb double-decker molecules bind tightly to the Ir(111) surface. By resonantly injecting tunneling electrons into its LUMO or HOMO state, the Tb double-decker molecule can be switched from a four-lobed structure to an eight-lobed structure. After switching, energy positions of the HOMO and LUMO states both shift closer to the Fermi level. Dy double-decker molecules also exhibit the same switching properties on the Ir(111) surface. The switching behavior of the molecules is tentatively attributed to a conformational change of the double-decker molecular frame.

  13. The Double Star magnetic field investigation: instrument design, performance and highlights of the first year's observations

    Directory of Open Access Journals (Sweden)

    C. Carr

    2005-11-01

    Full Text Available One of the primary objectives of the Double Star mission is the accurate measurement of the magnetic field vector along the orbits of the two spacecraft. The magnetic field is an essential parameter for the understanding of space plasma processes and is also required for the effective interpretation of data from the other instruments on the spacecraft. We present the design of the magnetic field instrument onboard both of the Double Star spacecraft and an overview of the performance as measured first on-ground and then in-orbit. We also report the results of in-flight calibration of the magnetometers, and the processing methods employed to produce the final data products which are provided to Double Star investigators, and the wider community in general. Particular attention is paid to the techniques developed for removing magnetic interference generated by the solar arrays on the first (equatorial orbiting spacecraft. Results from the first year of operations are reviewed in the context of combined observations by Double Star and Cluster, and examples given from the different regions visited by the spacecraft to date.

  14. Tiny Stars, Strong Fields: Exploring the Origin of Intense Magnetism in M Stars

    Science.gov (United States)

    Toomre, Juri

    . We bring to this our prior experience with studying dynamo processes in the outer convective envelopes of G- (the Sun) and Ftype stars, briefly of M dwarfs, and in full convective cores within more massive A- and B-type stars. Our previous work suggests that M dwarfs could display a broad range of dynamo behavior, from cyclic reversals to more chaotic variations, and further to both weak and strong dynamo states. We will focus on the latter, exploring how superequipartition magnetic fields could be achieved by dynamo action in M dwarfs, as are likely needed to energize super-flares and huge active regions, and what limits the peak field strengths. M-type stars are distinctive in becoming fully convective with decreasing mass at about M3.5 in spectral type (or about 0.35 solar masses). At this transition, a steep rise in the fraction of magnetically active stars is observed that is accompanied by an increasing rotational velocity. Clearly how mass-loss and spin-down can lead to this is of interest in itself. However, here we propose to study the manner in which dynamos operating in fully convective M dwarf interiors beyond the transition may be able to achieve very strong magnetic fields, and how field strengths and apparent magnetic activity increases with rotation rate as suggested by observations. We believe that global connectivity of flows and fields across the core center will admit new classes of strong behavior, as revealed by our B star core dynamos, not realized when a convective envelope is bounded below by a tachocline. These ideas need to be tested in a self-consistent manner with global ASH simulations to gain theoretical insights into what is the origin of the fierce magnetic activity in some of M dwarfs that may be potential hosts to Earth-like planets. Such 3-D MHD simulations, though challenging, are now feasible and would complement the intensive observational searches under way.

  15. Permanent magnet online magnetization performance analysis of a flux mnemonic double salient motor using an improved hysteresis model

    Science.gov (United States)

    Zhu, Xiaoyong; Quan, Li; Chen, Yunyun; Liu, Guohai; Shen, Yue; Liu, Hui

    2012-04-01

    The concept of the memory motor is based on the fact that the magnetization level of the AlNiCo permanent magnet in the motor can be regulated by a temporary current pulse and memorized automatically. In this paper, a new type of memory motor is proposed, namely a flux mnemonic double salient motor drive, which is particularly attractive for electric vehicles. To accurately analyze the motor, an improved hysteresis model is employed in the time-stepping finite element method. Both simulation and experimental results are given to verify the validity of the new method.

  16. Strong impact of lattice vibrations on electronic and magnetic properties of paramagnetic Fe revealed by disordered local moments molecular dynamics

    NARCIS (Netherlands)

    Alling, B.; Kormann, F.H.W.; Grabowski, B; Glensk, A; Abrikosov, I.A.

    2016-01-01

    We study the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron at finite temperature, employing the disordered local moments molecular dynamics (DLM-MD) method. Vibrations strongly affect the distribution of local magnetic moments at finite

  17. Asymptotic behaviour of the equilibrium nuclear separation for the H{sup +}{sub 2} molecule in a strong magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Benguria, Rafael [Pontificia Universidad Catolica de Chile, Departamento de Fisica, Casilla 306, Santiago 22, Chile (Chile); Brummelhuis, Raymond [School of Economics, Mathematics and Statistics, 7-15 Gresse Street, University of London (United Kingdom); Duclos, Pierre [Centre de Physique Theorique UMR 6207-Unite Mixte de Recherche du CNRS et des Universites Aix-Marseille I, Aix-Marseille II et de l' Universite du Sud Toulon-Var-Laboratoire affilie a la FRUMAM, Luminy Case 907, F-13288 Marseille Cedex 9 (France); Perez-Oyarzun, Santiago [Instituto de Ciencias Basicas, Facultad de Ingenieria, Universidad Diego Portales, Av. Ejercito 441, Casilla 298-v, Santiago (Chile); Vytras, Petr [Katedra Matematiky, FJFI, CVUT, Trojanova 13, CZ-Prague 12000 (Czech Republic)

    2006-06-30

    We consider the hydrogen molecular ion H{sup +}{sub 2} in the fixed nuclear approximation, in the presence of a strong homogeneous magnetic field. We determine the leading asymptotic behaviour for the equilibrium distance between the nuclei of this molecule in the limit when the strength of the magnetic field goes to infinity.

  18. Strong Coupling Cavity QED with Gate-Defined Double Quantum Dots Enabled by a High Impedance Resonator

    Directory of Open Access Journals (Sweden)

    A. Stockklauser

    2017-03-01

    Full Text Available The strong coupling limit of cavity quantum electrodynamics (QED implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size 2g/2π=238  MHz at a resonator linewidth κ/2π=12  MHz and a DQD charge qubit decoherence rate of γ_{2}/2π=40  MHz extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.

  19. Semiclassical quantization of integrable systems of few interacting anyons in a strong magnetic field

    International Nuclear Information System (INIS)

    Sivan, N.; Levit, S.

    1992-01-01

    We present a semiclassical theory of charged interacting anyons in a strong magnetic field. We derive the appropriate generalization of the WKB quantization conditions and determine the corresponding wave functions for non separable integrable anyonic systems. This theory is applies to a system of two interacting anyons, two interacting anyons in the presence of an impurity and three interacting anyons. We calculate the dependence of the semiclassical energy levels on the statistical parameter and find regions in which dependence follows very different patterns. The semiclassical treatment allows to find the correlation between these patterns and the change in the character of the classical motion of the system. We also test the accuracy of the mean field approximation for low and high energy states of the three anyons. (author)

  20. Influence of strong magnetic fields on laser pulse propagation in underdense plasma

    Science.gov (United States)

    Wilson, T. C.; Li, F. Y.; Weikum, M.; Sheng, Z. M.

    2017-06-01

    We examine the interaction between intense laser pulses and strongly magnetised plasmas in the weakly relativistic regime. An expression for the electron Lorentz factor coupling both relativistic and cyclotron motion nonlinearities is derived for static magnetic fields along the laser propagation axis. This is applied to predict modifications to the refractive index, critical density, group velocity dispersion and power threshold for relativistic self-focusing. It is found that electron quiver response is enhanced under right circularly-polarised light, decreasing the power threshold for various instabilities, while a dampening effect occurs under left circularly-polarised light, increasing the power thresholds. Derived theoretical predictions are tested by one- and three-dimensional particle-in-cell simulations.

  1. Hot electromagnetic outflows. III. Displaced fireball in a strong magnetic field

    International Nuclear Information System (INIS)

    Thompson, Christopher; Gill, Ramandeep

    2014-01-01

    The evolution of a dilute electron-positron fireball is calculated in the regime of strong magnetization and high compactness (ℓ ∼ 10 3 -10 8 ). Heating is applied at a low effective temperature (<25 keV), appropriate to breakout from a confining medium, so that relaxation to a blackbody is inhibited by pair annihilation. The diffusion equation for Compton scattering by thermal pairs is coupled to a trans-relativistic cyclo-synchrotron source. We find that the photon spectrum develops a quasi-thermal peak at energy ∼0.1 m e c 2 in the comoving frame, with a power-law slope below it that is characteristic of gamma-ray bursts (GRBs; F ω ∼ const). The formation of a thermal high-energy spectrum is checked using the full kinetic equations. Calculations for a baryon-dominated photosphere reveal a lower spectral peak energy, and a harder low-energy spectrum, unless ion rest mass carries ≲ 10 –5 of the energy flux. We infer that (1) the GRB spectrum is inconsistent with the neutron-rich wind emitted by a young magnetar or neutron torus, and points to an event horizon in the engine; (2) neutrons play a negligible role in prompt gamma-ray emission; (3) the relation between observed peak frequency and burst energy is bounded below by the observed Amati relation if the Lorentz factor ∼(opening angle) –1 at breakout, and the jet is surrounded by a broader sheath that interacts with a collapsing stellar core; (4) X-ray flashes are consistent with magnetized jets with ion-dominated photospheres; (5) high-frequency Alfvén waves may become charge starved in the dilute pair gas; (6) limitations on magnetic reconnection from plasma collisionality have been overestimated.

  2. Global Pc5 pulsations during strong magnetic storms: excitation mechanisms and equatorward expansion

    Science.gov (United States)

    Marin, J. A.; Pilipenko, V.; Vega, P.; Zesta, E.; Stepanova, M. V.; Uozumi, T.

    2012-12-01

    The spatial structure of Pc5 waves during the recovery phases of strong magnetic storms is important not only for the identification of possible physical mechanisms of its excitation, but as an important parameter of the ULF driver of relativistic electrons. The dynamics of global Pc5 waves during the magnetic storms on October 29-31, 2003 and May 15, 2005 is studied, using the data from the trans-American network of magnetometers comprising SAMBA, MAGDAS, CARISMA, and MACCS arrays. We study the behavior of Pc5 wave properties and spectral characteristics with respect to latitude. One of the accepted sources of Pc5 wave activity is Kelvin-Helmholtz instability in the flanks of the magnetosphere. In our study we examine whether the KH instability is sufficient as an excitation mechanism for the observed waves? More specifically, we attempt to determine, what is the Pc5 wave generation type: self-excitation, resonant response, trigger? While the KH instability generation takes place at the outer flanks of the magnetosphere, Pc5 waves are observed at all latitudes. We determine how deep into the magnetosphere these Pc5 waves activity can extend and what is the wave energy transmission mechanism: surface mode, cavity mode, Alfven field-line resonance, magnetospheric MHD waveguide?

  3. Disorder effects on helical edge transport in graphene under a strong tilted magnetic field

    Science.gov (United States)

    Huang, Chunli; Cazalilla, Miguel A.

    2015-10-01

    In a recent experiment, Young et al. [Nature (London) 505, 528 (2014), 10.1038/nature12800] observed a metal to insulator transition as well as transport through helical edge states in monolayer graphene under a strong, tilted magnetic field. Under such conditions, the bulk is a magnetic insulator which can exhibit metallic conduction through helical edges. It was found that the two-terminal conductance of the helical channels deviates from the expected quantized value (=e2/h per edge, at zero temperature). Motivated by this observation, we study the effect of disorder on the conduction through the edge channels. We show that, unlike for helical edges of topological insulators in semiconducting quantum wells, a disorder Rashba spin-orbit coupling does not lead to backscattering, at least to leading order. Instead, we find that the lack of perfect antialignment of the electron spins in the helical channels to be the most likely cause for backscattering arising from scalar (i.e., spin-independent) impurities. The intrinsic spin-orbit coupling and other time-reversal symmetry-breaking and/or sublattice parity-breaking potentials also lead to (subleading) corrections to the channel conductance.

  4. The Design of a Device for the Generation of a Strong Magnetic Field in an Air Gap Using Permanent Magnets

    Czech Academy of Sciences Publication Activity Database

    Žežulka, Václav; Straka, Pavel

    2017-01-01

    Roč. 22, č. 2 (2017), s. 250-256 ISSN 1226-1750 Institutional support: RVO:67985891 Keywords : magnet ic field * permanent magnet s * NdFeB magnet s * Halbach arrays Subject RIV: BM - Solid Matter Physics ; Magnet ism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.) Impact factor: 0.713, year: 2016

  5. Study of magnetic properties for co double-nanorings: Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Qingying, E-mail: qyye@fjnu.edu.cn [College of Physics and Energy, Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, Fujian Normal University, Fuzhou, 350007 (China); Chen, Shuiyuan [College of Physics and Energy, Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, Fujian Normal University, Fuzhou, 350007 (China); Electrical and Computer Engineering, Northeastern University, Boston, 02115 (United States); Liu, Jingyao; Huang, Chao; Huang, Shengkai [College of Physics and Energy, Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, Fujian Normal University, Fuzhou, 350007 (China); Huang, Zhigao, E-mail: zghuang@fjnu.edu.cn [College of Physics and Energy, Fujian Provincial Key Laboratory of Quantum Manipulation and New Energy Materials, Fujian Normal University, Fuzhou, 350007 (China)

    2016-06-15

    In this paper, cobalt double-nanorings (Co D-N-rings) structure model was constructed. Based on Monte-Carlo simulation (MC) method combining with Fast Fourier Transformation and Micromagnetism (FFTM) method, the magnetic properties of Co D-N-rings with different geometric dimensions have been studied. The simulated results indicate that, the magnetization steps in hysteresis loops is the result of the special spin configurations (SCs), i.e., onion-type state and vortex-type state, which are very different from that in many other nanostructures, such as nanometer thin-films, nanotubes, etc. Besides, Co D-N-rings with different geometric dimensions present interesting magnetization behavior, which is determined by the change of both SCs and exchange interaction in Co D-N-rings. - Highlights: • A double-nanorings structure (named as D-N-rings) was proposed to construct cobalt nanometer thin film. • Monte Carlo method combining with FFTM method was used to simulate magnetic properties of the Co D-N-rings. • Magnetization dynamic processes of the Co D-N-rings were obtained and interpreted through the evolutionary process of spin configurations. • Geometric dimensions deeply influence the magnetization behavior of the Co D-N-rings, which is determined by the change of both SCs and exchange interaction.

  6. The mean energy loss by neutrino with magnetic moment in strong magnetic field with consideration of positronium contribution to photon dispersion

    Science.gov (United States)

    Mosichkin, A. F.

    2017-11-01

    The process of radiative decay of the neutrino with a magnetic moment in a strong magnetic field with consideration of positronium influence on photon dispersion has been studied. Positronium contribution to the photon polarization operator induces significant modifications of the photon dispersion law and neutrino radiative decay amplitude. It has been shown that the mean energy loss of a neutrino with magnetic a moment significantly increases, when the positronium contribution to photon dispersion is taken into account.

  7. Behavior of Particle Depots in Molten Silicon During Float-Zone Growth in Strong Magnetic Fields

    Science.gov (United States)

    Jauss, T.; Croell, A.; SorgenFrei, T.; Azizi, M.; Reimann, C.; Friedrich, J.; Volz, M. P.

    2014-01-01

    Solar cells made from directionally solidified silicon cover 57% of the photovoltaic industry's market [1]. One major issue during directional solidification of silicon is the precipitation of foreign phase particles. These particles, mainly SiC and Si3N4, are precipitated from the dissolved crucible coating, which is made of silicon nitride, and the dissolution of carbon monoxide from the furnace atmosphere. Due to their hardness and size of several hundred micrometers, those particles can lead to severe problems during the wire sawing process for wafering the ingots. Additionally, SiC particles can act as a shunt, short circuiting the solar cell. Even if the particles are too small to disturb the wafering process, they can lead to a grit structure of silicon micro grains and serve as sources for dislocations. All of this lowers the yield of solar cells and reduces the performance of cells and modules. We studied the behaviour of SiC particle depots during float-zone growth under an oxide skin, and strong static magnetic fields. For high field strengths of 3T and above and an oxide layer on the sample surface, convection is sufficiently suppressed to create a diffusive like regime, with strongly dampened convection [2, 3]. To investigate the difference between atomically rough phase boundaries and facetted growth, samples with [100] and [111] orientation were processed.

  8. COMPRESSIBLE RELATIVISTIC MAGNETOHYDRODYNAMIC TURBULENCE IN MAGNETICALLY DOMINATED PLASMAS AND IMPLICATIONS FOR A STRONG-COUPLING REGIME

    Energy Technology Data Exchange (ETDEWEB)

    Takamoto, Makoto [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, 113-0033 (Japan); Lazarian, Alexandre, E-mail: mtakamoto@eps.s.u-tokyo.ac.jp, E-mail: alazarian@facstaff.wisc.edu [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States)

    2016-11-10

    In this Letter, we report compressible mode effects on relativistic magnetohydrodynamic (RMHD) turbulence in Poynting-dominated plasmas using three-dimensional numerical simulations. We decomposed fluctuations in the turbulence into 3 MHD modes (fast, slow, and Alfvén) following the procedure of mode decomposition in Cho and Lazarian, and analyzed their energy spectra and structure functions separately. We also analyzed the ratio of compressible mode to Alfvén mode energy with respect to its Mach number. We found the ratio of compressible mode increases not only with the Alfvén Mach number, but also with the background magnetization, which indicates a strong coupling between the fast and Alfvén modes. It also signifies the appearance of a new regime of RMHD turbulence in Poynting-dominated plasmas where the fast and Alfvén modes are strongly coupled and, unlike the non-relativistic MHD regime, cannot be treated separately. This finding will affect particle acceleration efficiency obtained by assuming Alfvénic critical-balance turbulence and can change the resulting photon spectra emitted by non-thermal electrons.

  9. Local Magnetism in Strongly Correlated Electron Systems with Orbital Degrees of Freedom

    Science.gov (United States)

    Ducatman, Samuel Charles

    The central aim of my research is to explain the connection between the macroscopic behavior and the microscopic physics of strongly correlated electron systems with orbital degrees of freedom through the use of effective models. My dissertation focuses on the sub-class of these materials where electrons appear to be localized by interactions, and magnetic ions have well measured magnetic moments. This suggests that we can capture the low-energy physics of the material by employing a minimal model featuring localized spins which interact with each other through exchange couplings. I describe Fe1+y Te and beta-Li2IrO3 with effective models primarily focusing on the spins of the magnetic ions, in this case Fe and Ir, respectively. The goal with both materials is to gain insight and make predictions for experimentalists. In chapter 2, I focus on Fe1+yTe. I describe why we believe the magnetic ground state of this material, with an observed Bragg peak at Q +/- pi/2, pi/2), can be described by a Heisenberg model with 1st, 2nd, and 3rd neighbor interactions. I present two possible ground states of this model in the small J1 limit, the bicollinear and plaquette states. In order to predict which ground state the model prefers, I calculate the spin wave spectrum with 1/S corrections, and I find the model naturally selects the "plaquette state." I give a brief description of the ways this result could be tested using experimental techniques such as polarized neutron scattering. In chapter 3, I extend the model used in chapter 2. This is necessary because the Heisenberg model we employed cannot explain why Fe1+yTe undergoes a phase transition as y is increased. We add an additional elements to our calculation; we assume that electrons in some of the Fe 3D orbitals have selectively localized while others remain itinerant. We write a new Hamiltonian, where localized moments acquire a new long-range RKKY-like interaction from interactions with the itinerant electrons. We are

  10. Phase transitions and magnetization of the mixed-spin Ising–Heisenberg double sawtooth frustrated ladder

    Science.gov (United States)

    Arian Zad, Hamid; Ananikian, Nerses

    2018-04-01

    The mixed spin-(1,1/2) Ising–Heisenberg double sawtooth ladder containing a mixture of both spin-1 and spin-1/2 nodal atoms, and the spin-1/2 interstitial dimers are approximately solved by the transfer-matrix method. Here, we study in detail the ground-state phase diagrams, also influences of the bilinear exchange coupling on the rungs and cyclic four-spin exchange interaction in square plaquette of each block on the magnetization and magnetic susceptibility of the suggested ladder at low temperature. Such a double sawtooth ladder may be found in a Shastry-Sutherland lattice-type. In spite of the spin ordering of odd and even blocks being different from each other, due to the commutation relation between all different block Hamiltonians, phase diagrams, magnetization behavior and thermodynamic properties of the model are the same for odd and even blocks. We show that at low temperature, both exchange couplings can change the quality and quantity of the magnetization plateaus versus the magnetic field changes. Specially, we find a new magnetization plateau M/Ms= 5/6 for this model. Besides, we examine the magnetic susceptibility and specific heat of the model in detail. It is proven that behaviors of the magnetization and the magnetic susceptibility coincide at low temperature. The specific heat displays diverse temperature dependencies, which include a Schottky-type peak at a special temperature interval. We observe that with increase of the bilinear exchange coupling on the rungs, second peak temperature dependence grows.

  11. The contribution of Diamond Light Source to the study of strongly correlated electron systems and complex magnetic structures.

    Science.gov (United States)

    Radaelli, P G; Dhesi, S S

    2015-03-06

    We review some of the significant contributions to the field of strongly correlated materials and complex magnets, arising from experiments performed at the Diamond Light Source (Harwell Science and Innovation Campus, Didcot, UK) during the first few years of operation (2007-2014). We provide a comprehensive overview of Diamond research on topological insulators, multiferroics, complex oxides and magnetic nanostructures. Several experiments on ultrafast dynamics, magnetic imaging, photoemission electron microscopy, soft X-ray holography and resonant magnetic hard and soft X-ray scattering are described. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  12. Numerical simulations of a cylinder wake under a strong axial magnetic field

    Science.gov (United States)

    Dousset, Vincent; Pothérat, Alban

    2008-01-01

    We study the flow of a liquid metal in a square duct past a circular cylinder in a strong externally imposed magnetic field. In these conditions, the flow is quasi-two-dimensional, which allows us to model it using a two-dimensional (2D) model. We perform a parametric study by varying the two control parameters Re and Ha (Ha2 is the ratio of Lorentz to viscous forces) in the ranges [0…6000] and [0…2160], respectively. The flow is found to exhibit a sequence of four regimes. The first three regimes are similar to those of the non-magnetohydrodynamic (non-MHD) 2D circular wake, with transitions controlled by the friction parameter Re /Ha. The fourth one is characterized by vortices raising from boundary layer separations at the duct side walls, which strongly disturbs the Kármán vortex street. This provides the first explanation for the breakup of the 2D Kármán vortex street first observed experimentally by Frank, Barleon, and Müller [Phys. Fluids 13, 2287 (2001)]. We also show that, for high values of Ha (Ha⩾1120), the transition to the fourth regime occurs for Re ∝0.56Ha, and that it is accompanied by a sudden drop in the Strouhal number. In the first three regimes, we show that the drag coefficient and the length of the steady recirculation regions located behind the cylinder are controlled by the parameter Re /Ha4/5. Also, the free shear layer that separates the recirculation region from the free stream is similar to a free MHD parallel layer, with a thickness of the order of Ha-1/2 that is quite different to that of the non-MHD case, and therefore strongly influences the dynamics of this region. We also present one case at Re =3×104 and Ha =1120, where this layer undergoes an instability of the Kelvin-Helmholtz-type.

  13. Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

    OpenAIRE

    Abraimov D; Ballarino A; Barth C; Bottura L; Dietrich R; Francis A; Jaroszynski J; Majkic G S; McCallister J; Polyanskii A; Rossi L; Rutt A; Santos M; Schlenga K; Selvamanickam V

    2015-01-01

    A significant increase of critical current in high magnetic field up to 31 T was recorded in long tapes manufactured by employing a double disorder route. In a double disordered high temperature superconductor (HTS) a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa2Cu3O x-d matrix and (ii) the extrinsic disorder is in...

  14. Magnetic structure of RPdSn (R=Tb, Ho) single crystal compounds under strong magnetic field

    International Nuclear Information System (INIS)

    Andoh, Y.; Kurisu, M.; Nakamoto, G.; Tsutaoka, T.; Kawano, S.

    2003-01-01

    Rare earth compounds RTX, where R stands for rare earth elements, T for Ni, Pd or Rh, and X for Sn or Ge, crystallize to a rhombic ε-TiNiSi structure. Only rare earth elements R contribute to magnetic properties since T and X atoms are nonmagnetic. The competition between RKKY indirect interaction and large magnetic anisotropy generates many complicated magnetic phases. At a low temperature phase, complicated magnetisms such as meta-magnetism were observed in magnetization curves with many steps. In previous experiments dealing with RPdSn where R means Tb or Ho, some characteristics of magnetic properties of these compounds were deduced from magnetization measurements and neutron diffraction without external magnetic field. In this report, the change of magnetic scattering of neutron diffraction was studied under external magnetic fields in order to reveal the mechanism of the phase transformations of the compounds. The difference between TbPdSn and HoPdSn compounds was observed in magnetic field dependence of the wave vectors of the magnetic scattering. Two independent wave vectors in magnetic scattering existed in HoPdSn compound. (Y. Kazumata)

  15. Static magnetic therapy does not decrease pain or opioid requirements: a randomized double-blind trial.

    Science.gov (United States)

    Cepeda, M Soledad; Carr, Daniel B; Sarquis, Tony; Miranda, Nelcy; Garcia, Ricardo J; Zarate, Camilo

    2007-02-01

    A growing multibillion dollar industry markets magnetic necklaces, bracelets, bands, insoles, back braces, mattresses, etc., for pain relief, although there is little evidence for their efficacy. We sought to evaluate the effect of magnetic therapy on pain intensity and opioid requirements in patients with postoperative pain. We designed a randomized, double-blind, controlled trial. One-hundred-sixty-five patients older than 12 yr of age were randomized to magnetic (n = 81) or sham therapy (n = 84) upon reporting moderate-to-severe pain in the postanesthesia care unit. Devices were placed over the surgical incision and left in place for 2 h. Patients rated their pain intensity on a 0-10 scale every 10 min and received incremental doses of morphine until pain intensity was Magnetic therapy lacks efficacy in controlling acute postoperative pain intensity levels or opioid requirements and should not be recommended for pain relief in this setting.

  16. Magnetic, electronic, and optical properties of double perovskite Bi2FeMnO6

    Science.gov (United States)

    Ahmed, Towfiq; Chen, Aiping; Yarotski, Dmitry A.; Trugman, Stuart A.; Jia, Quanxi; Zhu, Jian-Xin

    2017-03-01

    Double perovskite Bi2FeMnO6 is a potential candidate for the single-phase multiferroic system. In this work, we study the magnetic, electronic, and optical properties in BFMO by performing the density functional theory calculations and experimental measurements of magnetic moment. We also demonstrate the strain dependence of magnetization. More importantly, our calculations of electronic and optical properties reveal that the onsite local correlation on Mn and Fe sites is critical to the gap opening in BFMO, which is a prerequisite condition for the ferroelectric ordering. Finally, we calculate the x-ray magnetic circular dichroism spectra of Fe and Mn ions (L2 and L3 edges) in BFMO.

  17. Magnetic, electronic, and optical properties of double perovskite Bi2FeMnO6

    Directory of Open Access Journals (Sweden)

    Towfiq Ahmed

    2017-03-01

    Full Text Available Double perovskite Bi2FeMnO6 is a potential candidate for the single-phase multiferroic system. In this work, we study the magnetic, electronic, and optical properties in BFMO by performing the density functional theory calculations and experimental measurements of magnetic moment. We also demonstrate the strain dependence of magnetization. More importantly, our calculations of electronic and optical properties reveal that the onsite local correlation on Mn and Fe sites is critical to the gap opening in BFMO, which is a prerequisite condition for the ferroelectric ordering. Finally, we calculate the x-ray magnetic circular dichroism spectra of Fe and Mn ions (L2 and L3 edges in BFMO.

  18. Synergistic effect between strongly coupled CoAl layered double hydroxides and graphene for the electrocatalytic reduction of oxygen

    International Nuclear Information System (INIS)

    Wang, Yinling; Wang, Zhangcui; Wu, Xiaoqin; Liu, Xiaowang; Li, Maoguo

    2016-01-01

    Highlights: • CoAl-LDHs were synthesized on the surface of graphene oxide in situ. • The oxygen reduction reaction activity of the catalyst was investigated. • The synergistic effect between CoAl-LDHs and rGO is discussed in detail. • The roles of Co 2+ in the LDHs were clarified. - Abstract: Precious metal-free electrocatalysts with high efficiency and durability for the oxygen reduction reaction (ORR) are strongly desired in the field of energy technology. Herein, the CoAl layered double hydroxides (CoAl-LDHs)/reduced graphene oxide (rGO) composites were successfully prepared by growing CoAl-LDHs on the surface of GO in situ via coprecipitation and subsequently hydrothermal treatment. The structure, composition, morphology and ORR catalytic activity of the CoAl-LDHs/rGO composites were investigated as a function of mass ratios of CoAl-LDHs and GO. The results show that there is an optimum mass ratio of CoAl-LDHs and GO (w CoAl-LDHs :w GO = 1:5) for the ORR catalytic activity, where the electron transfer number for ORR at the CoAl-LDHs/rGO composites reaches to 3.5, closing to the full four-electron process. The synergistic effect between CoAl-LDHs and rGO is discussed in detail and the discussion is instructive for the construction of the better transition metal oxides/carbon composite-based ORR catalysts.

  19. Emergent Ising degrees of freedom above a double-stripe magnetic ground state

    Science.gov (United States)

    Zhang, Guanghua; Flint, Rebecca

    2017-12-01

    Double-stripe magnetism [Q =(π /2 ,π /2 )] has been proposed as the magnetic ground state for both the iron-telluride and BaTi2Sb2O families of superconductors. Double-stripe order is captured within a J1-J2-J3 Heisenberg model in the regime J3≫J2≫J1 . Intriguingly, besides breaking spin-rotational symmetry, the ground-state manifold has three additional Ising degrees of freedom associated with bond ordering. Via their coupling to the lattice, they give rise to an orthorhombic distortion and to two nonuniform lattice distortions with wave vector (π ,π ) . Because the ground state is fourfold degenerate, modulo rotations in spin space, only two of these Ising bond order parameters are independent. Here, we introduce an effective field theory to treat all Ising order parameters, as well as magnetic order, and solve it within a large-N limit. All three transitions, corresponding to the condensations of two Ising bond order parameters and one magnetic order parameter are simultaneous and first order in three dimensions, but lower dimensionality, or equivalently weaker interlayer coupling, and weaker magnetoelastic coupling can split the three transitions, and in some cases allows for two separate Ising phase transitions above the magnetic one.

  20. Neutrinoless double beta decay experiment DCBA using a magnetic momentum-analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Ishihara, N., E-mail: nobuhiro.ishihara@kek.jp [High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801 (Japan); Kato, Y.; Inagaki, T.; Ohama, T.; Takeda, S.; Yamada, Y. [High Energy Accelerator Research Organization (KEK), Tsukuba, 305-0801 Japan (Japan); Ukishima, N.; Teramoto, Y. [Osaka City University, Sumiyoshi, Osaka, 558-8585 (Japan); Morishima, Y.; Nakano, I. [Okayama University, Okayama, 700-8530 (Japan); Kitamura, S. [Tokyo Metropolitan University, Arakawa, Tokyo, 116-8551 (Japan); Sakamoto, Y. [Tohoku Gakuin University, Izumi, Sendai, 981-3193 (Japan); Nagasaka, Y. [Hiroshima Institute of Technology, Saeki, Hiroshima, 731-5193 (Japan); Tamura, N. [Niigata University, Niigata, 950-2181 (Japan); Tanaka, K. [BTE, Minato, Tokyo, 105-0011 (Japan); Ito, R. [ZTJ, Chiyoda, Tokyo, 101-0047 (Japan)

    2011-12-15

    A magnetic momentum-analyzer is being developed at KEK for neutrinoless double beta decay experiment called DCBA (Drift Chamber Beta-ray Analyzer, inverted ABCD). A lot of thin plates of {sup 150}Nd compound are installed in tracking detectors located in a uniform magnetic field. The three-dimensional position information is obtained for the helical track of a beta ray. More R and D will be studied using the second test apparatus DCBA-T2, which is now under construction.

  1. Electromagnetic properties of inner double walled carbon nanotubes investigated by nuclear magnetic resonance

    KAUST Repository

    Bouhrara, M.

    2013-01-01

    The nuclear magnetic resonance (NMR) analytical technique was used to investigate the double walled carbon nanotubes (DWNTs) electromagnetic properties of inner walls. The local magnetic and electronic properties of inner nanotubes in DWNTs were analyzed using 25% 13C enriched C 60 by which the effect of dipolar coupling could be minimized. The diamagnetic shielding was determined due to the ring currents on outer nanotubes in DWNTs. The NMR chemical shift anisotropy (CSA) spectra and spin-lattice relaxation studies reveal the metallic properties of the inner nanotubes with a signature of the spin-gap opening below 70 K.

  2. Electromagnetic Properties of Inner Double Walled Carbon Nanotubes Investigated by Nuclear Magnetic Resonance

    Directory of Open Access Journals (Sweden)

    M. Bouhrara

    2013-01-01

    Full Text Available The nuclear magnetic resonance (NMR analytical technique was used to investigate the double walled carbon nanotubes (DWNTs electromagnetic properties of inner walls. The local magnetic and electronic properties of inner nanotubes in DWNTs were analyzed using 25% 13C enriched C60 by which the effect of dipolar coupling could be minimized. The diamagnetic shielding was determined due to the ring currents on outer nanotubes in DWNTs. The NMR chemical shift anisotropy (CSA spectra and spin-lattice relaxation studies reveal the metallic properties of the inner nanotubes with a signature of the spin-gap opening below 70 K.

  3. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields

    Science.gov (United States)

    Zhu, Wuming; Trickey, S. B.

    2017-12-01

    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li+, Be+, and B+, in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B field.

  4. Accurate and balanced anisotropic Gaussian type orbital basis sets for atoms in strong magnetic fields.

    Science.gov (United States)

    Zhu, Wuming; Trickey, S B

    2017-12-28

    In high magnetic field calculations, anisotropic Gaussian type orbital (AGTO) basis functions are capable of reconciling the competing demands of the spherically symmetric Coulombic interaction and cylindrical magnetic (B field) confinement. However, the best available a priori procedure for composing highly accurate AGTO sets for atoms in a strong B field [W. Zhu et al., Phys. Rev. A 90, 022504 (2014)] yields very large basis sets. Their size is problematical for use in any calculation with unfavorable computational cost scaling. Here we provide an alternative constructive procedure. It is based upon analysis of the underlying physics of atoms in B fields that allow identification of several principles for the construction of AGTO basis sets. Aided by numerical optimization and parameter fitting, followed by fine tuning of fitting parameters, we devise formulae for generating accurate AGTO basis sets in an arbitrary B field. For the hydrogen iso-electronic sequence, a set depends on B field strength, nuclear charge, and orbital quantum numbers. For multi-electron systems, the basis set formulae also include adjustment to account for orbital occupations. Tests of the new basis sets for atoms H through C (1 ≤ Z ≤ 6) and ions Li + , Be + , and B + , in a wide B field range (0 ≤ B ≤ 2000 a.u.), show an accuracy better than a few μhartree for single-electron systems and a few hundredths to a few mHs for multi-electron atoms. The relative errors are similar for different atoms and ions in a large B field range, from a few to a couple of tens of millionths, thereby confirming rather uniform accuracy across the nuclear charge Z and B field strength values. Residual basis set errors are two to three orders of magnitude smaller than the electronic correlation energies in multi-electron atoms, a signal of the usefulness of the new AGTO basis sets in correlated wavefunction or density functional calculations for atomic and molecular systems in an external strong B

  5. In-plane magnetic field-dependent magnetoresistance of gated asymmetric double quantum wells

    Czech Academy of Sciences Publication Activity Database

    Krupko, Yuriy; Smrčka, Ludvík; Vašek, Petr; Svoboda, Pavel; Cukr, Miroslav; Jansen, L.

    2004-01-01

    Roč. 22, - (2004), s. 44-47 ISSN 1386-9477. [International Conference on Electronic Properties of Two-Dimensional Systems /15./. Nara, 14.07.2003-18.07.2003] R&D Projects: GA ČR GA202/01/0754 Institutional research plan: CEZ:AV0Z1010914 Keywords : double - layer two-dimensional electron system * magnetotransport * gate voltage Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.898, year: 2004

  6. Magnetic behavior of Mg-Al-Zn-Fe mixed oxides from precursors layered double hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Oliva, M.I., E-mail: marcosivanoliva@gmail.com [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); IFFAM AF (CONICET - FaMAF UNC), M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina); Heredia, A. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Zandalazini, C.I. [Centro Laser de Ciencias Moleculares. INFIQC-FCQ-Grupo de Ciencia de Materiales-FaMAF-Universidad Nacional de Cordoba, Ciudad Universitaria, CP5000 Cordoba, Argentina CONICET (Argentina); Crivello, M. [CITeQ - Facultad R. Cordoba, Universidad Tecnologica Nacional Maestro Lopez esq. Cruz Roja Argentina, CP 5016 Cordoba (Argentina); Corchero, E. [Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, M. Allende y H. de la Torre Ciudad Universitaria, 5000 Cordoba (Argentina)

    2012-08-15

    Mixed oxides of Mg-Al-Zn-Fe were obtained by calcination of layered double hydroxides (LDH) prepared by coprecipitation reaction with hydrothermal treatment. The structural characterization of precursors and oxides was carried out by X rays diffraction, showing increases of ZnO phase with the increase of the zinc content. Magnetic behavior was studied by vibrating sample magnetometer (VSM) and by a superconducting quantum interference device (SQUID) showing both paramagnetic and super paramagnetic behavior depending on both particles size and composition.

  7. Lattice-induced double-valley degeneracy lifting in graphene by a magnetic field.

    Science.gov (United States)

    Luk'yanchuk, Igor A; Bratkovsky, Alexander M

    2008-05-02

    We show that the recently discovered double-valley splitting of the Landau levels in the quantum Hall effect in graphene can be explained as the perturbative orbital interaction of intravalley and intervalley microscopic orbital currents with a magnetic field. This effect is facilitated by the translationally noninvariant terms that correspond to graphene's crystallographic honeycomb symmetry but do not exist in the relativistic theory of massless Dirac fermions in quantum electrodynamics. We discuss recent data in view of these findings.

  8. Interlayer Hall effect in double quantum wells subject to in-plane magnetic fields

    Czech Academy of Sciences Publication Activity Database

    Kolorenč, Jindřich; Smrčka, Ludvík; Středa, Pavel

    2002-01-01

    Roč. 66, č. 8 (2002), s. 085301-1 - 085301-7 ISSN 0163-1829 R&D Projects: GA ČR GA202/01/0754; GA ČR GA202/01/0764 Institutional research plan: CEZ:AV0Z1010914 Keywords : double - layer two-dimensional electron system * magnetotransport * Hall effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.327, year: 2002

  9. SU-E-T-227: Could the Alpha/Beta Ratio Change in a Strong Magnetic Field?

    Energy Technology Data Exchange (ETDEWEB)

    Pang, G [Odette Cancer Centre, 2075 Bayview Avenue, Toronto M4N 3M5, Canada and Sunnybrook Research Institute and Departments of Radiation Oncology and Medical Biophysics, University of Toronto, Toronto (Canada)

    2015-06-15

    Purpose: Magnetic resonance imaging (MRI) is being integrated into radiotherapy delivery for MRI-guided radiotherapy. The presence of a strong magnetic field from a MRI machine during radiotherapy delivery presents a new challenge since the trajectories of electrons liberated by ionizing radiation in patients are strongly dependent on the applied magnetic field. The purpose of this work is to explore the potential effect of a strong magnetic field on the α/β ratio, an important radiobiological parameter in radiotherapy. Methods: Based on the theory of dual radiation action, the α/β ratio can be expressed by an integral of the product of two microdosimetry quantities γ(x) and t(x), where γ(x) is the probability that two energy transfers, a distance x apart, results in a lesion, and t(x) is the proximity function, which is the energy-weighted point-pair distribution of distances between energy transfer points in a track. The quantity t(x) depends on the applied magnetic field. An analytical approach has been used to derive a formula that can be used to calculate the α/β ratio in an extremely strong magnetic field. Results: The α/β ratio has been evaluated in the special case when the applied magnetic field approaches infinity, which gives the upper limit of the potential change of the α/β ratio due to the presence of a strong magnetic field. For V79 Chinese hamster cells it has been shown that the α/β ratio could be increased by 2.90 times for Pd-103, 2.97 times for I-125 and about 2.3 times for Co-60 sources when the applied magnetic field approaches infinity. Conclusion: It has been shown theoretically that the α/β ratio can change in a strong magnetic field, and there could be up to a nearly three-fold increase in the α/β ratio, depending on the strength of the applied magnetic field, the cell type and the radiation used.

  10. Biological effects of electromagnetic fields and recently updated safety guidelines for strong static magnetic fields

    International Nuclear Information System (INIS)

    Yamaguchi-Sekino, Sachiko; Sekino, Masaki; Ueno, Shoogo

    2011-01-01

    Humans are exposed daily to artificial and naturally occurring magnetic fields that originate from many different sources. We review recent studies that examine the biological effects of and medical applications involving electromagnetic fields, review the properties of static and pulsed electromagnetic fields that affect biological systems, describe the use of a pulsed electromagnetic field in combination with an anticancer agent as an example of a medical application that incorporates an electromagnetic field, and discuss the recently updated safety guidelines for static electromagnetic fields. The most notable modifications to the 2009 International Commission on Non-Ionizing Radiation Protection guidelines are the increased exposure limits, especially for those who work with or near electromagnetic fields (occupational exposure limits). The recommended increases in exposure were determined using recent scientific evidence obtained from animal and human studies. Several studies since the 1994 publication of the guidelines have examined the effects on humans after exposure to high static electromagnetic fields (up to 9.4 tesla), but additional research is needed to ascertain further the safety of strong electromagnetic fields. (author)

  11. Biological effects of electromagnetic fields and recently updated safety guidelines for strong static magnetic fields.

    Science.gov (United States)

    Yamaguchi-Sekino, Sachiko; Sekino, Masaki; Ueno, Shoogo

    2011-01-01

    Humans are exposed daily to artificial and naturally occurring magnetic fields that originate from many different sources. We review recent studies that examine the biological effects of and medical applications involving electromagnetic fields, review the properties of static and pulsed electromagnetic fields that affect biological systems, describe the use of a pulsed electromagnetic field in combination with an anticancer agent as an example of a medical application that incorporates an electromagnetic field, and discuss the recently updated safety guidelines for static electromagnetic fields. The most notable modifications to the 2009 International Commission on Non-Ionizing Radiation Protection guidelines are the increased exposure limits, especially for those who work with or near electromagnetic fields (occupational exposure limits). The recommended increases in exposure were determined using recent scientific evidence obtained from animal and human studies. Several studies since the 1994 publication of the guidelines have examined the effects on humans after exposure to high static electromagnetic fields (up to 9.4 tesla), but additional research is needed to ascertain further the safety of strong electromagnetic fields.

  12. Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity

    Science.gov (United States)

    Davis, J. C. Séamus; Lee, Dung-Hai

    2013-01-01

    Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron–electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron–electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electron–electron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs. PMID:24114268

  13. Orientation of glutaraldehyde-fixed erythrocytes in strong static magnetic fields.

    Science.gov (United States)

    Higashi, T; Sagawa, S; Ashida, N; Takeuchi, T

    1996-01-01

    In a uniform static magnetic field up to 8 Telsa, glutaraldehyde-fixed erythrocytes showed an orientation in which their disk plane was perpendicular to the magnetic field. The paramagnetism of membrane-bound hemoglobin was through to contribute significantly to this orientation. The observation of magnetic orientation is directed toward understanding the fundamental microstructural aspects of the erythrocyte.

  14. Clustering of magnetic nanoparticles using a double hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid)

    Energy Technology Data Exchange (ETDEWEB)

    Sondjaja, Ronny [Singapore-MIT Alliance, 4 Engineering Drive 3, National University of Singapore 117576 (Singapore); Alan Hatton, T. [Singapore-MIT Alliance, 4 Engineering Drive 3, National University of Singapore 117576 (Singapore); Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)], E-mail: tahatton@mit.edu; Tam, Michael K.C. [Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario, N2L3G1 (Canada)], E-mail: mkctam@cape.uwaterloo.ca

    2009-08-15

    The use of a double hydrophilic block copolymer (DHBC), poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) to prepare magnetic nanoparticle (MNP) clusters was investigated. In this one-pot synthesis method, the DHBC controlled the particle growth and served as both stabilizer and clustering agent. Depending on the iron-to-polymer ratio, the synthesized particles can be in the form of colonies of small iron oxide particles or clusters of these particles with size larger than 100 nm. Compared to the previous reported result using random copolymers, the clusters prepared with DHBC were more compact and homogeneous. The yield of clusters increased when the amount of polymer added was limiting. Insufficient amounts of polymer resulted in the formation of bare patches on the magnetite surface, and the strong van der Waals attraction induced cluster formation.

  15. MULTI-WAVELENGTH STUDY OF A DELTA-SPOT. I. A REGION OF VERY STRONG, HORIZONTAL MAGNETIC FIELD

    International Nuclear Information System (INIS)

    Jaeggli, S. A.

    2016-01-01

    Active region NOAA 11035 appeared in 2009 December, early in the new solar activity cycle. This region achieved a delta sunspot (δ spot) configuration when parasitic flux emerged near the rotationally leading magnetic polarity and traveled through the penumbra of the largest sunspot in the group. Both visible and infrared imaging spectropolarimetry of the magnetically sensitive Fe i line pairs at 6302 and 15650 Å show large Zeeman splitting in the penumbra between the parasitic umbra and the main sunspot umbra. The polarized Stokes spectra in the strongest field region display anomalous profiles, and strong blueshifts are seen in an adjacent region. Analysis of the profiles is carried out using a Milne–Eddington inversion code capable of fitting either a single magnetic component with stray light or two independent magnetic components to verify the field strength. The inversion results show that the anomalous profiles cannot be produced by the combination of two profiles with moderate magnetic fields. The largest field strengths are 3500–3800 G in close proximity to blueshifts as strong as 3.8 km s −1 . The strong, nearly horizontal magnetic field seen near the polarity inversion line in this region is difficult to understand in the context of a standard model of sunspot magnetohydrostatic equilibrium

  16. MULTI-WAVELENGTH STUDY OF A DELTA-SPOT. I. A REGION OF VERY STRONG, HORIZONTAL MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Jaeggli, S. A., E-mail: sarah.jaeggli@nasa.gov [NASA Goddard Space Flight Center, Solar Physics Laboratory, Code 671, Greenbelt, MD 20771 (United States)

    2016-02-10

    Active region NOAA 11035 appeared in 2009 December, early in the new solar activity cycle. This region achieved a delta sunspot (δ spot) configuration when parasitic flux emerged near the rotationally leading magnetic polarity and traveled through the penumbra of the largest sunspot in the group. Both visible and infrared imaging spectropolarimetry of the magnetically sensitive Fe i line pairs at 6302 and 15650 Å show large Zeeman splitting in the penumbra between the parasitic umbra and the main sunspot umbra. The polarized Stokes spectra in the strongest field region display anomalous profiles, and strong blueshifts are seen in an adjacent region. Analysis of the profiles is carried out using a Milne–Eddington inversion code capable of fitting either a single magnetic component with stray light or two independent magnetic components to verify the field strength. The inversion results show that the anomalous profiles cannot be produced by the combination of two profiles with moderate magnetic fields. The largest field strengths are 3500–3800 G in close proximity to blueshifts as strong as 3.8 km s{sup −1}. The strong, nearly horizontal magnetic field seen near the polarity inversion line in this region is difficult to understand in the context of a standard model of sunspot magnetohydrostatic equilibrium.

  17. Multiple magnetic resonance and microwave absorption of metamaterial absorbers composed of double split ring resonators on grounded carbonyl iron composites

    Science.gov (United States)

    Lim, Jun-Hee; Kim, Sung-Soo

    2017-12-01

    This study investigates the triple-band absorption properties of metamaterial absorbers composed of a double split ring resonator (DSRR) on a grounded magnetic substrate of carbonyl iron powders. Computational tools are used to model the interaction between electromagnetic waves and the metamaterial structure. For perpendicular polarization with the electric field perpendicular to the SRR gap, triple-band absorption peaks are predicted in the simulation result of reflection loss. Magnetic resonance resulting from antiparallel currents between the upper DSRR and the lower ground plane is identified at the frequencies of the absorption peaks. The orientation of the two resonators influences the absorption characteristics, especially in the second and third peaks where the coupling between the inner SRR and outer SRR is strong. The current density distribution indicates that the two resonators oriented in the same direction achieve reduced coupling between them, which results in two absorption frequencies close to each other. For parallel polarization with the electric field parallel to the SRR gap, this study predicts dual-band absorption peaks corresponding to the magnetic resonance at the SRR wire.

  18. Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

    Science.gov (United States)

    Nair, Harikrishnan S.; Pradheesh, R.; Xiao, Yinguo; Cherian, Dona; Elizabeth, Suja; Hansen, Thomas; Chatterji, Tapan; Brückel, Th.

    2014-09-01

    Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite Y2CoMnO6 which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at Tc ≈ 75 K. At 2 K, it displays a strong ferromagnetic hysteresis with a significant coercive field of Hc ≈ 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8 K. In the temperature range 2 K ≤ T ≤ 5 K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y2CoMnO6 consists of 62% of monoclinic P21/n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots.

  19. Magnetization-steps in Y2CoMnO6 double perovskite: The role of antisite disorder

    International Nuclear Information System (INIS)

    Nair, Harikrishnan S.; Xiao, Yinguo; Brückel, Th.; Pradheesh, R.; Cherian, Dona; Elizabeth, Suja; Hansen, Thomas; Chatterji, Tapan

    2014-01-01

    Antisite disorder is observed to have significant impact on the magnetic properties of the double perovskite Y 2 CoMnO 6 which has been recently identified as a multiferroic. A paramagnetic-ferromagnetic phase transition occurs in this material at T c ≈ 75 K. At 2 K, it displays a strong ferromagnetic hysteresis with a significant coercive field of H c ≈ 15 kOe. Sharp steps are observed in the hysteresis curves recorded below 8 K. In the temperature range 2 K ≤ T ≤ 5 K, the hysteresis loops are anomalous as the virgin curve lies outside the main loop. The field-cooling conditions as well as the rate of field-sweep are found to influence the steps. Quantitative analysis of the neutron diffraction data shows that at room temperature, Y 2 CoMnO 6 consists of 62% of monoclinic P2 1 /n with nearly 70% antisite disorder and 38% Pnma. The bond valence sums indicate the presence of other valence states for Co and Mn which arise from disorder. We explain the origin of steps by using a model for pinning of magnetization at the antiphase boundaries created by antisite disorder. The steps in magnetization closely resemble the martensitic transformations found in intermetallics and display first-order characteristics as revealed in the Arrott's plots.

  20. Magnetic properties of the strongly correlated chain antiferromagnet KTb(WO4)2

    International Nuclear Information System (INIS)

    Khatsko, E.; Loginov, A.; Cherny, A.; Rykova, A.

    2006-01-01

    The susceptibility and magnetization of a single crystal of KTb(WO 4 ) 2 has been measured in the temperature range 0.5-80 K in magnetic fields up to 6 T. It is shown that KTb(WO 4 ) 2 is an Ising magnet with only one component of the magnetic moment. The three-dimensional phase transition to the antiferromagnetically ordered state has been found below 0.7 K. This transition can be described in the molecular field two-level approximation. The principal exchange constant has been estimated. By using experimental data the magnetic structure of KTb(WO 4 ) 2 is proposed

  1. The effect of structural ordering on the magnetic, electronic, and optical properties of the LaPbMnSbO6 double perovskite

    International Nuclear Information System (INIS)

    Zhandun, V.S.; Zinenko, V.I.

    2016-01-01

    The interplay between the magnetic, electronic, and optical properties and the cation structural ordering in the LaPbMnSbO 6 double perovskite is studied using the Vienna Ab Initio Simulation Package (VASP). The layer and rock-salt cation ordering types are investigated. Both of them are of great importance. The rock-salt ordering of B-site cations is one of the most frequently met cation ordering types in double perovskites; the layer ordering of both cations, which can be considered as a heterostructure, is interesting for fundamental research and experimental synthesis. It was established that the properties of the two investigated structures are strongly different. The compound with the layered structure exhibits the behavior typical of a semimetal with the ferromagnetic configuration of magnetic moments, which is unusual for a double perovskite. The rock-salt structure behaves as an antiferromagnetic insulator. Another surprising feature of the structure with the layer ordering is the coexistence of a polar phase and the metal-type conductivity. The calculated optical characteristics of the two ordered structures are compared with the experimental dates. - Highlights: • The dependence of LaPbMnSbO 6 properties on the structural ordering. • The unusual behavior of electronic and magnetic properties of LL ordered compound. • Weyl-like features in the band structure of LL ordered double perovskite. • The presence of polar phase along with metal conductivity in LL ordered compound.

  2. First Principles Study of Electronic and Magnetic Structures in Double Perovskites

    Science.gov (United States)

    Ball, Molly

    At present, electronic devices are reaching their storage and processing limit causing a major push to find materials that can be used in the next generation of devices. Double perovskites with A2BB'O 6 stoichiometry form one of the leading classes of materials currently being studied as a potential candidate because of their extremely wide range and tunability of functional properties, along with economic and highly scalable synthesis routes. Having a thorough understanding of their electronic and magnetic structure and their dependence on composition and local structure is the basis for targeted development of novel and optimized double perovskites. While the body of knowledge and rules within the field of materials chemistry has enabled many previous discoveries, recent developments within density functional theory (DFT) allow by now a rather realistic description of the electronic and magnetic properties of materials and especially identification of their origin from geometry and orbital structure. This thesis details computational work based on DFT within several collaborative studies to better understand the electronic and magnetic properties of double perovskites and related materials that show promise for future use in multifunctional devices. First, we will begin with a general introduction to the double perovskite structure, their properties, and the computational methods used to study them. In the next section, we will look at the case of the antiferromagnetic, insulating double perovskite Sr2CoOsO6, where measurements showed that the transition metal ions in the two sublattices undergo magnetic ordering independently of each other, indicating weak magnetic short-range coupling and a dominance of longer-range interactions, which has previously not been observed. Here, we performed DFT calculations to extract the exchange strengths between the ions and explain this unique dominance of the long-range interactions. Then, we will look at studies done on thin

  3. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.

    2011-08-24

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  4. Double-Layer Magnetic Nanoparticle-Embedded Silica Particles for Efficient Bio-Separation.

    Directory of Open Access Journals (Sweden)

    San Kyeong

    Full Text Available Superparamagnetic Fe3O4 nanoparticles (NPs based nanomaterials have been exploited in various biotechnology fields including biomolecule separation. However, slow accumulation of Fe3O4 NPs by magnets may limit broad applications of Fe3O4 NP-based nanomaterials. In this study, we report fabrication of Fe3O4 NPs double-layered silica nanoparticles (DL MNPs with a silica core and highly packed Fe3O4 NPs layers. The DL MNPs had a superparamagnetic property and efficient accumulation kinetics under an external magnetic field. Moreover, the magnetic field-exposed DL MNPs show quantitative accumulation, whereas Fe3O4 NPs single-layered silica nanoparticles (SL MNPs and silica-coated Fe3O4 NPs produced a saturated plateau under full recovery of the NPs. DL MNPs are promising nanomaterials with great potential to separate and analyze biomolecules.

  5. Reduction of a Double Supply Frequency Pressure Pulsation in an Electro-Magnetic Pump

    International Nuclear Information System (INIS)

    Seong, Seung-Hwan; Park, Rae-Young; Lee, Tae-Ho; Kim, Seong-O

    2007-01-01

    Fast breeder reactors using sodium coolant have adopted the AC induction electro-magnetic (EM) pump as a coolant pump for a liquid metal flow. The EM pumps have some disadvantages such as a double supply frequency (DSF) pressure pulsation and so on. The DSF pressure pulsation occurs in the induction EM pump, when an alternating current is supplied to the coils. The magnetic field produced by the coils reacts with the alternating current being passed through the sodium, and then the pressure developed pulsates at twice the input frequency. The DSF pressure pulsation is dominantly affected by the disturbances of the electromagnetic force near the stator or core ends. The disturbance of the electromagnetic force can be derived the Lenz's Law which means that the opposite forces are generated when the magnetic field abruptly changed by the liquid metal flows near the stator ends. This phenomenon is called as the end effect

  6. Magnetic entropy change and critical exponents in double perovskite Y2NiMnO6

    Science.gov (United States)

    Sharma, G.; Tripathi, T. S.; Saha, J.; Patnaik, S.

    2014-11-01

    We report the magnetic entropy change (ΔSM) and the critical exponents in the double perovskite manganite Y2NiMnO6 with a ferromagnetic to paramagnetic transition TC~85 K. For a magnetic field change ΔH=80 kOe, a maximum magnetic entropy change ΔSM=-6.57 J/kg K is recorded around TC. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization MS(T) and the inverse initial susceptibility χ0-1(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at TC. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel-Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ɛ)=ɛβf±(H/ɛ) according to which the magnetization-field-temperature data around TC should collapse into two curves for temperatures below and above TC.

  7. Strong soft X-ray emission from a double-stream gas puff target irradiated with a nanosecond Nd:YAG laser

    Energy Technology Data Exchange (ETDEWEB)

    Fiedorowicz, H.; Bartnik, A.; Rakowski, R.; Szczurek, M. [Military Univ. of Technology, Warsaw (Poland). Inst. of Optoelectronics; Daido, H.; Suzuki, M.; Yamagami, S.; Choi, I.W.; Tang, H.J. [Osaka Univ., Suita (Japan). Inst. of Laser Engineering

    2001-07-01

    Soft X-ray emission from a new double-stream gas puff target irradiated with a nanosecond, high-power Nd:YAG laser pulse has been studied. The target was formed by pulsed injection of gas into a hollow gas stream made from helium by using a double-nozzle setup. Strong X-ray emissions near 10 nm from the double-stream krypton/helium, near 11 nm from the xenon/helium, and at 13 nm from the oxygen/helium targets were observed. The emission from the double-stream gas puff target was several times higher as compared to the ordinary gas puff targets, and comparable to the emission from the solid targets irradiated in the same conditions. (orig.)

  8. Characterization of Magnetic Field Immersed Photomultipliers from Double Chooz Experiment. Design and Construction of their Magnetic Shields

    International Nuclear Information System (INIS)

    Valdivia Valero, F. J.

    2007-01-01

    Flavour oscillations of neutrinos are a quantum-mechanical effect widely demonstrated. It is explained through interferences of their mass eigenstates, therefore, belonging to the physical area beyond the Standard Model. This work deals with the CIEMAT collaboration in the neutrino experiment Double Chooz. Such an experiment aims to measure the mixture angle θ 1 3, one of the PMNS leptonic mixture matrix, with a un reached-before sensibility by decrease of systematic errors. For this, two identical scintillator detectors, equipped with PMT's, will be sited at different distances from two reactors located in the nuclear power plant CHOOZ B (France). The electronic neutrino flux from these reactors will be compared, explaining its deficit by flavour oscillations of these particles. The identity of both detectors will be diminished by the magnetic field effects on the PMT's response. Therefore, this study serves as for quantifying such an effects as for fitting the magnetic shields design that minimize them. Shielding measurements and final design of magnetic shields as much as the effect these ones cause in the PMT's response immersed in a monitored magnetic field are presented. (Author) 85 refs

  9. Strongly magnetic soil developed on a non-magnetic rock basement: A case study from NW Bulgaria

    Czech Academy of Sciences Publication Activity Database

    Grison, Hana; Petrovský, Eduard; Jordanova, N.; Kapička, Aleš

    2011-01-01

    Roč. 55, č. 4 (2011), s. 697-716 ISSN 0039-3169 R&D Projects: GA AV ČR(CZ) KJB300120604 Institutional research plan: CEZ:AV0Z30120515 Keywords : magnetic susceptibility * magnetite * soil * pollution * climate * limestone Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.700, year: 2011

  10. Light-induced changes of cubic and uniaxial magnetic aniosotropy in a magnet doped by strongly anisotropic ions

    Czech Academy of Sciences Publication Activity Database

    Zaytseva, I.; Stupakiewicz, A.; Maziewski, A.; Zablotskyy, Vitaliy A.

    254-255, - (2003), s. 118-120 ISSN 0304-8853. [Soft Magnetic Material Conference ( SMM 15). Bilbao, 05.09.2001-07.09.2001] Institutional research plan: CEZ:AV0Z1010914 Keywords : photomagnetic effects * light-induced anisotropy * garnets Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.910, year: 2003

  11. New magnetic rails with double-layer Halbach structure by employing NdFeB and ferrite magnets for HTS maglev

    Science.gov (United States)

    Sun, Ruixue; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Jipeng; Deng, Zigang

    2018-01-01

    In the high temperature superconducting (HTS) maglev system, the magnetic rail as an essential infrastructure is needed all along the route to carry passengers and goods to the destinations. Thus, large amount of rare earth magnetic materials are required in the magnetic rail construction. In order to decrease the dependence of magnetic rails on rare earth elements, the ferrite magnet is employed to replace part of the NdFeB magnets containing rare earth elements. Consequently, a new type rail with double-layer Halbach structure is presented, which is consisted of NdFeB and ferrite magnets. In this paper, we designed and fabricated the proposed rail, and further measured its magnetic flux density distribution and electromagnetic force interacting with HTS bulks. Experimental results indicate that, this new type rail, in double-layer Halbach structure, can achieve an equivalent distribution of magnetic flux density and levitation performance as the pure NdFeB Halbach rail, while a 10% reduction in NdFeB magnet consumption can be realized at the same time. In addition this work explores another magnetic material selection for HTS maglev applications. The dependence on rare earth element and the cost of magnetic rails can be further reduced, as the coercive force of ferrite magnets improved.

  12. Molecular quantum magnetism with strong spin-orbit coupling in inorganic solid Ba3Yb2Zn5O11

    Science.gov (United States)

    Park, Sang-Youn; Ji, Sungdae; Park, Jae-Hoon; Do, Seunghwan; Choi, Kwang-Yong; Jang, Dongjin; Schmidt, Burkhard; Brando, Manuel; Butch, Nicholas

    The molecular magnet, assembly of finite number of spins which are isolated from environment, is a model system to study the quantum information process such as the qubit or spintronic devices. In past decades, the molecular magnet has been mostly realized in organic material, however, it has difficulty synthesizing materials or controlling their properties, meanwhile tremendous endeavors to search inorganic molecular magnet are continuing. Here, we propose Ba3Yb2Zn5O11 as a candidate of inorganic molecular magnet. This material consists of an alternating 3D-array of small and large tetrahedron containing antiferromagnetically coupled four pseudospin-1/2 Yb ions, and magnetic properties are described by an isolated tetrahedron without long-range magnetic ordering. Inelastic neutron scattering measurement with external magnetic field reveals that extraordinarily huge Dzyaloshinsky-Moriya (DM) interaction originating from strong spin-orbit coupling in Yb isospin is the key to explain energy level of tetrahedron in addition to Heisenberg exchange interaction and Zeeman effect. Magnetization measurement shows the Landau-Zener transition between avoided crossing levels caused by DM interaction.

  13. Method for Transformation of Weakly Magnetic Minerals (Hematite, Goethite into Strongly Magnetic Mineral (Magnetite to Improve the Efficiency of Technologies for Oxidized Iron Ores Benefication

    Directory of Open Access Journals (Sweden)

    Ponomarenko, O.

    2015-03-01

    Full Text Available A new method for relatively simple transformation of weakly magnetic minerals (goethite (α-FeOOH and hematite (α-Fe2O3 into strongly magnetic mineral (magnetite (Fe3O4 was developed. It was shown, that transformation of structure and magnetic characteristics of go ethite and hematite are realized in the presence of starch at relatively low temperatures (in the range of 300—600 °С. Obtained results open up new possibilities for development of effective technologies for oxidized iron ore beneficiation.

  14. The sharp-front magnetic diffusion wave of a strong magnetic field diffusing into a solid metal

    Science.gov (United States)

    Xiao, Bo; Gu, Zhuo-Wei; Kan, Ming-Xian; Wang, Gang-Hua; Zhao, Jian-Heng; Computational Physics Team

    2016-10-01

    When a mega-gauss magnetic field diffuses into a solid metal, the Joule heat would rise rapidly the temperature of the metal, and the rise of temperature leads to an increase of the metal's resistance, which in turn accelerates the magnetic field diffusion. Those positive feedbacks acting iteratively would lead to an interesting sharp-front magnetic diffusion wave. By assuming that the metal's resistance has an abrupt change from a small value ηS to larger value ηL at some critical temperature Tc, the sharp-front magnetic diffusion wave can be solved analytically. The conditions for the emerging of the sharp-front magnetic diffusion wave are B0 >Bc , ηL /ηS >> 1 , and ηL/ηSB0/-Bc Bc >> 1 , where Bc =√{ 2μ0Jc } , B0 is the vacuum magnetic field strength, and Jc is the critical Joule heat density. The wave-front velocity of the diffusion wave is Vc =ηL/μ0B0/-Bc Bc1/xc , where xc is the depth the wave have propagated in the metal. In this presentation we would like to discuss the derivation of the formulas and its impact to magnetically driven experiments. The work is supported by the Foundation of China Academy of Engineering Physics (No. 2015B0201023).

  15. STRONG MAGNETIC-X-RAY DICHROISM IN 2P ABSORPTION-SPECTRA OF 3D TRANSITION-METAL IONS

    NARCIS (Netherlands)

    VANDERLAAN, G; THOLE, BT

    1991-01-01

    From atomic calculations in crystal-field symmetry we find a very strong circular and linear dichroism in the 2p x-ray absorption edges of magnetically ordered 3d transition-metal ions. The spectral shape changes drastically with the character of the ground state, which is determined by the presence

  16. Study of muon triggers and momentum reconstruction in a strong magnetic field for a muon detector at LHC

    CERN Document Server

    Della Negra, Michel; Eggert, Karsten; Hervé, A; Wittgenstein, F; Karimäki, V; Kinnunen, Ritva; Pimiä, M; Tuominiemi, Jorma; Dau, D; Ferrando, A; Torrente-Lujan, E; Bettini, A; Centro, Sandro; Martinelli, R; Meneguzzo, Anna Teresa; Zotto, P L; Bacci, Cesare; Ceradini, F; Ciapetti, G; Lacava, F; Nisati, A; Petrolo, E; Pontecorvo, L; Veneziano, Stefano; Zanello, L; Cardarelli, R; Di Ciaccio, Anna; Santonico, R; Cline, D; Lazic, S; Mohammadi, M; Park, J; Szoncsó, F; Walzel, G; Wulz, Claudia Elisabeth; CERN. Geneva. Detector Research and Development Committee

    1990-01-01

    We propose to construct a small fraction of a muon detector in a strong magnetic field, for possible use in an LHC experiment, and to test it in a beam containing hadrons and muons. Properties of muons from hadron decays and of hadron punch-through, i.e. angle, momentum and timing distributions of the outgoing particles, will be measured for various absorber thicknesses, including the effect of strong magnetization of the absorber. The efficiency of different muon triggers and the rejection against hadron punch-through and decay muons will be studied. Reconstruction of muons and their momentum measurement in magnetized iron will be investigated, including the effect of catastrophic energy losses of high momentum muons. The performance of resistive plate chambers (RPC) as fast trigger hodoscopes will be studied.

  17. Aversive responses of captive sandbar sharks Carcharhinus plumbeus to strong magnetic fields

    NARCIS (Netherlands)

    Siegenthaler, A.; Niemantsverdriet, P.R.W.; Laterveer, M.; Heitkönig, I.M.A.

    2016-01-01

    This experimental study focused on the possible deterrent effect of permanent magnets on adult sandbar sharks Carcharhinus plumbeus. Results showed that the presence of a magnetic field significantly reduced the number of approaches of conditioned C. plumbeus towards a target indicating that

  18. Effect of angular momentum alignment and strong magnetic fields on the formation of protostellar discs

    Science.gov (United States)

    Gray, William J.; McKee, Christopher F.; Klein, Richard I.

    2018-01-01

    Star-forming molecular clouds are observed to be both highly magnetized and turbulent. Consequently, the formation of protostellar discs is largely dependent on the complex interaction between gravity, magnetic fields, and turbulence. Studies of non-turbulent protostellar disc formation with realistic magnetic fields have shown that these fields are efficient in removing angular momentum from the forming discs, preventing their formation. However, once turbulence is included, discs can form in even highly magnetized clouds, although the precise mechanism remains uncertain. Here, we present several high-resolution simulations of turbulent, realistically magnetized, high-mass molecular clouds with both aligned and random turbulence to study the role that turbulence, misalignment, and magnetic fields have on the formation of protostellar discs. We find that when the turbulence is artificially aligned so that the angular momentum is parallel to the initial uniform field, no rotationally supported discs are formed, regardless of the initial turbulent energy. We conclude that turbulence and the associated misalignment between the angular momentum and the magnetic field are crucial in the formation of protostellar discs in the presence of realistic magnetic fields.

  19. Cycloidal magnetism driven ferroelectricity in double tungstate LiFe (WO4)2

    Science.gov (United States)

    Liu, Meifeng; Lin, Lingfang; Zhang, Yang; Li, Shaozhen; Huang, Qingzhen; Garlea, V. Ovidiu; Zou, Tao; Xie, Yunlong; Wang, Yu; Lu, Chengliang; Yang, Lin; Yan, Zhibo; Wang, Xiuzhang; Dong, Shuai; Liu, Jun-Ming

    2017-05-01

    Tungstates A WO4 with the wolframite structure characterized by the A O6 octahedral zigzag chains along the c axis can be magnetic if A =Mn , Fe, Co, Cu, Ni. Among them, MnWO4 is a unique member with a cycloid Mn2 + spin order developed at low temperature, leading to an interesting type-II multiferroic behavior. However, so far no other multiferroic material in the tungstate family has been found. In this work, we present the synthesis and the systematic study of the double tungstate LiFe (WO4)2 . Experimental characterizations including structural, thermodynamic, magnetic, neutron powder diffraction, and pyroelectric measurements unambiguously confirm that LiFe (WO4)2 is the secondly found multiferroic system in the tungstate family. The cycloidal magnetism driven ferroelectricity is also verified by density functional theory calculations. Although here the magnetic couplings between Fe ions are indirect, namely via the so-called super-super-exchanges, the temperatures of magnetic and ferroelectric transitions are surprisingly much higher than those of MnWO4.

  20. Double-peaked core field of flux ropes during magnetic reconnection

    Science.gov (United States)

    Liu, Chaoxu; Feng, Xueshang; Nakamura, Rumi; Guo, Jianpeng; Wang, Rongsheng

    2017-06-01

    A flux rope event observed in the magnetotail exhibits a double-peaked core field feature. The generation of such double-peaked feature within the flux rope is explored with Hall-MHD simulations and theoretical analysis based on multiple X line reconnection. Simulations with a guide field produce flux ropes bounded by two active X lines in the thin current sheet. The guide field, combined with Hall-generated field, leads to a donut-shaped core field (having a double-peaked profile) near the magnetic separatrix. Subsequently, it rotates into the central region of the flux rope, which tends to be the force-free configuration. The analysis shows that there are three major factors affecting the evolution of the core field, including the guide field, convective, and Hall terms originating from the generalized Ohm's law. The convective term can become stronger near the central region of flux rope, and the Hall term dominates the region next to the separatrix during the early stages of the flux rope evolution. It implies that several different factors contribute to the generation of the double-peaked core field. The results may help explain a variety of core fields available in magnetotail flux ropes.

  1. A Solar Eruption from a Weak Magnetic Field Region with Relatively Strong Geo-Effectiveness

    Science.gov (United States)

    Wang, R.

    2017-12-01

    A moderate flare eruption giving rise to a series of geo-effectiveness on 2015 November 4 caught our attentions, which originated from a relatively weak magnetic field region. The associated characteristics near the Earth are presented, which indicates that the southward magnetic field in the sheath and the ICME induced a geomagnetic storm sequence with a Dst global minimum of 90 nT. The ICME is indicated to have a small inclination angle by using a Grad-Shafranov technique, and corresponds to the flux rope (FR) structure horizontally lying on the solar surface. A small-scale magnetic cancelling feature was detected which is beneath the FR and is co-aligned with the Atmospheric Imaging Assembly (AIA) EUV brightening prior to the eruption. Various magnetic features for space-weather forecasting are computed by using a data product from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) called Space-weather HMI Active Region Patches (SHARPs), which help us identify the changes of the photospheric magnetic fields during the magnetic cancellation process and prove that the magnetic reconnection associated with the flux cancellation is driven by the magnetic shearing motion on the photosphere. An analysis on the distributions at different heights of decay index is carried out. Combining with a filament height estimation method, the configurations of the FR is identified and a decay index critical value n = 1 is considered to be more appropriate for such a weak magnetic field region. Through a comprehensive analysis to the trigger mechanisms and conditions of the eruption, a clearer scenario of a CME from a relatively weak region is presented.

  2. Spin excitations in systems with hopping electron transport and strong position disorder in a large magnetic field

    Science.gov (United States)

    Shumilin, A. V.

    2016-10-01

    We discuss the spin excitations in systems with hopping electron conduction and strong position disorder. We focus on the problem in a strong magnetic field when the spin Hamiltonian can be reduced to the effective single-particle Hamiltonian and treated with conventional numerical technics. It is shown that in a 3D system with Heisenberg exchange interaction the spin excitations have a delocalized part of the spectrum even in the limit of strong disorder, thus leading to the possibility of the coherent spin transport. The spin transport provided by the delocalized excitations can be described by a diffusion coefficient. Non-homogenous magnetic fields lead to the Anderson localization of spin excitations while anisotropy of the exchange interaction results in the Lifshitz localization of excitations. We discuss the possible effect of the additional exchange-driven spin diffusion on the organic spin-valve devices.

  3. Strong compression of a magnetic field with a laser-accelerated foil.

    Science.gov (United States)

    Yoneda, Hitoki; Namiki, Tomonori; Nishida, Akinori; Kodama, Ryosuke; Sakawa, Youichi; Kuramitsu, Yasuhiro; Morita, Taichi; Nishio, Kento; Ide, Takao

    2012-09-21

    We demonstrate the generation of high magnetic fields for condensed matter research using a high-power laser system. A cavity in which a seed magnetic field is applied is compressed by a kJ ns laser pulse. The time history of the compressed magnetic field is monitored by observing the Faraday effect rotation of polarization of a probe pulse in a glass fiber. To maintain a low-temperature condition in the final high-field region, we put a high-resistance foil around the final compression area. If we assume the length of the compression region is equal to the laser spot size, a magnetic field of more than 800 T is observed by Faraday rotation. Because of the large mass of the compression foil, this high magnetic field is sustained during almost 2 ns. During compression, a rarefaction wave from the backside of the accelerated foil and expanding material from the inner protection foil affect the magnetic field compression history, but the final compressed magnetic field strength agrees with the ratio between the initial sample area and the compressed cavity area.

  4. Crystal structure and magnetic properties of double perovskite Mn2FeSbO6

    International Nuclear Information System (INIS)

    Tyutyunnik, A.P.; Bazuev, G.V.; Kuznetsov, M.V.; Zainulin, Yu.G.

    2011-01-01

    Graphical abstract: Projection along the cubic perovskite axes [0 0 1] of the double perovskite Mn 2 FeSbO 6 . Highlights: → Mn 2 FeSbO 6 is prepared from Mn 2 O 3 , Fe 2 O 3 and Sb 2 O 3 at 6 GPa and 1000 o C. → According to XPS measurements, manganese is present as Mn 2+ , the iron - as Fe 3+ . → This compound has the smallest unit cell among double perovskites. → It was suppose that Mn 2 FeSbO 6 exhibited antiferromagnetism below 19.5 K. -- Abstract: The double perovskite Mn 2 FeSbO 6 has been synthesized under pressure 6 GPa and temperature 1000 o C. The crystal structure refinement of Mn 2 FeSbO 6 was carried out with the GSAS program suite using X-ray diffraction data. XRD pattern of Mn 2 FeSbO 6 was indexed with a monoclinic unit cell (space group P2 1 /n) with parameters: a = 5.2431(3) A, b = 5.3935(3) A, c = 7.6358(5) A, β = 89.693(2) o , V = 215.927 A 3 , Z = 2. It found that Fe and Sb atoms are completely ordered in 2d and 2c positions of double perovskite structure respectively. According to XPS measurements, manganese in this compound is present as Mn 2+ , whiles the iron - as Fe 3+ . Magnetization measurements revealed the presence about 3 mass% of ferromagnetic impurity in the sample. Dependence of AC susceptibility χ'' from temperature showed that magnetic properties compound are determined probably by transformation in antiferromagnetic state below 19.5 K.

  5. Double-coronal X-Ray and Microwave Sources Associated with a Magnetic Breakout Solar Eruption

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yao; Wu, Zhao; Zhao, Di; Wang, Bing; Du, Guohui [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China); Liu, Wei [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States); Schwartz, Richard A., E-mail: yaochen@sdu.edu.cn [NASA Goddard Space Flight Center and American University, Greenbelt, MD 20771 (United States)

    2017-07-01

    Double-coronal hard X-ray (HXR) sources are believed to be critical observational evidence of bi-directional energy release through magnetic reconnection in large-scale current sheets in solar flares. Here, we present a study on double-coronal sources observed in both HXR and microwave regimes, revealing new characteristics distinct from earlier reports. This event is associated with a footpoint-occulted X1.3-class flare (2014 April 25, starting at 00:17 UT) and a coronal mass ejection that were likely triggered by the magnetic breakout process, with the lower source extending upward from the top of the partially occulted flare loops and the upper source co-incident with rapidly squeezing-in side lobes (at a speed of ∼250 km s{sup −1} on both sides). The upper source can be identified at energies as high as 70–100 keV. The X-ray upper source is characterized by flux curves that differ from those of the lower source, a weak energy dependence of projected centroid altitude above 20 keV, a shorter duration, and an HXR photon spectrum slightly harder than those of the lower source. In addition, the microwave emission at 34 GHz also exhibits a similar double-source structure and the microwave spectra at both sources are in line with gyrosynchrotron emission given by non-thermal energetic electrons. These observations, especially the co-incidence of the very-fast squeezing-in motion of side lobes and the upper source, indicate that the upper source is associated with (and possibly caused by) this fast motion of arcades. This sheds new light on the origin of the corona double-source structure observed in both HXRs and microwaves.

  6. Magnetic-field dependence of strongly anisotropic spin reorientation transition in NdFeO3: a terahertz study.

    Science.gov (United States)

    Jiang, Junjie; Song, Gaibei; Wang, Dongyang; Jin, Zuanming; Tian, Zhen; Lin, Xian; Han, Jiaguang; Ma, Guohong; Cao, Shixun; Cheng, Zhenxiang

    2016-03-23

    One of the biggest challenges in spintronics is finding how to switch the magnetization of a material. One way of the spin switching is the spin reorientation transition (SRT), a switching of macroscopic magnetization rotated by 90°. The macroscopic magnetization in a NdFeO3 single crystal rotates from Γ4 to Γ2 via Γ24 as the temperature is decreased from 170 to 100 K, while it can be switched back to Γ4 again by increasing the temperature. However, the precise roles of the magnetic-field induced SRT are still unclear. By using terahertz time-domain spectroscopy (THz-TDS), here, we show that the magnetic-field induced SRT between Γ4 and Γ2 is strongly anisotropic, depending on the direction of the applied magnetic field. Our experimental results are well interpreted by the anisotropy of rare-earth Nd(3+) ion. Furthermore, we find that the critical magnetic-field required for SRT can be modified by changing the temperature. Our study suggests that the anisotropic SRT in NdFeO3 single crystal provides a platform to facilitate the potential applications in robust spin memory devices.

  7. Electronic bond structure of the H2+ ion in a strong magnetic field: A study of the parallel configuration

    International Nuclear Information System (INIS)

    Kappes, U.; Schmelcher, P.

    1995-01-01

    A large number of magnetically dressed states of the hydrogen molecular ion for parallel internuclear and magnetic field axes are investigated. The numerical calculations of the molecular states and potential-energy curves in the fixed-nuclei approximation are based on a recently established and optimized atomic orbital basis set. We study electronic states within the range 0≤|m|≤10 of magnetic quantum numbers and for several field strengths. In particular, we also investigate many excited states within a subspace for fixed magnetic quantum number and parity. In order to understand the influence of the magnetic field on theof excited molecular states, we perform a detailed comparison of the electronic probability distributions and potential-energy curves in the field-free space with those in the presence of a magnetic field. As a major result we observe the existence of two different classes of strongly bound, i.e., stable, magnetically dressed states whose corresponding counterparts in the field-free space exhibit purely repulsive potential-energy curves, i.e., are unstable. Corrections which are going beyond the fixed-nuclei approach, i.e., the coupling of the center of mass to the electronic motion, as well as the mass corrections are investigated in order to ensure the physical validity of our results

  8. Influence of calculation error of total field anomaly in strongly magnetic environments

    Science.gov (United States)

    Yuan, Xiaoyu; Yao, Changli; Zheng, Yuanman; Li, Zelin

    2016-04-01

    An assumption made in many magnetic interpretation techniques is that ΔTact (total field anomaly - the measurement given by total field magnetometers, after we remove the main geomagnetic field, T0) can be approximated mathematically by ΔTpro (the projection of anomalous field vector in the direction of the earth's normal field). In order to meet the demand for high-precision processing of magnetic prospecting, the approximate error E between ΔTact and ΔTpro is studied in this research. Generally speaking, the error E is extremely small when anomalies not greater than about 0.2T0. However, the errorE may be large in highly magnetic environments. This leads to significant effects on subsequent quantitative inference. Therefore, we investigate the error E through numerical experiments of high-susceptibility bodies. A systematic error analysis was made by using a 2-D elliptic cylinder model. Error analysis show that the magnitude of ΔTact is usually larger than that of ΔTpro. This imply that a theoretical anomaly computed without accounting for the error E overestimate the anomaly associated with the body. It is demonstrated through numerical experiments that the error E is obvious and should not be ignored. It is also shown that the curves of ΔTpro and the error E had a certain symmetry when the directions of magnetization and geomagnetic field changed. To be more specific, the Emax (the maximum of the error E) appeared above the center of the magnetic body when the magnetic parameters are determined. Some other characteristics about the error Eare discovered. For instance, the curve of Emax with respect to the latitude was symmetrical on both sides of magnetic equator, and the extremum of the Emax can always be found in the mid-latitudes, and so on. It is also demonstrated that the error Ehas great influence on magnetic processing transformation and inversion results. It is conclude that when the bodies have highly magnetic susceptibilities, the error E can

  9. Shannon entropy as an indicator of atomic avoided crossings in strong parallel magnetic and electric fields.

    Science.gov (United States)

    González-Férez, R; Dehesa, J S

    2003-09-12

    Avoided crossings are the most distinctive atomic spectroscopic features in the presence of magnetic and electric fields. We point out the role of Shannon's information entropy as an indicator or predictor of these phenomena by studying the dynamics of some excited states of hydrogen in the presence of parallel magnetic and electric fields. Moreover, in addition to the well-known energy level repulsion, it is found that Shannon's entropy manifests the informational exchange of the involved states as the magnetic field strength is varied across the narrow region where an avoided crossing occurs.

  10. A variational study of the self-trapped magnetic polaron formation in double-exchange model

    International Nuclear Information System (INIS)

    Liu Tao; Feng Mang; Wang Kelin

    2005-01-01

    We study the formation of self-trapped magnetic polaron (STMP) in an antiferro/ferromagnetic double-exchange model semi-analytically by variational solutions. It is shown that the Jahn-Teller effect is not essential to the STMP formation and the STMP forms in the antiferromagnetic material within the region of the order of the lattice constant. We also confirm that no ground state STMP exists in the ferromagnetic background, but the ground state bound MP could appear due to the impurity potential

  11. Low-coupling impedance double-helix structure for use in a ferrite kicker magnet

    International Nuclear Information System (INIS)

    Giordano, S.

    1983-01-01

    In a machine such as the CBA, the ejection ferrite kicker magnet has a very large longitudinal and transverse coupling impedance which could destroy the beam. Using a double-helix structure that surrounds the beam, the beam-induced fields are confined within the helix and, therefore, decoupled from the kicker; but at the same time the helix is transparent to the external fields of the kicker. At first, this may seem paradoxical that the helix is opaque to the fields generated inside the structure by the beam and simultaneously transparent to the external fields generated by the kicker

  12. Generic mechanisms of decoherence of quantum oscillations in magnetic double-well systems

    International Nuclear Information System (INIS)

    Chudnovsky, Eugene M.

    2004-01-01

    Fundamental conservation laws mandate parameter-free generic mechanisms of decoherence of quantum oscillations in double-well systems. We consider two examples: tunneling of the magnetic moment in nanomagnets and tunneling between macroscopic current states in SQUIDs. In both cases the decoherence occurs via emission of phonons and photons at the oscillation frequency. We also show that in a system of identical qubits the decoherence greatly increases due to the superradiance of electromagnetic and sound waves. Our findings have important implications for building elements of quantum computers based upon nanomagnets and SQUIDs

  13. Generic mechanisms of decoherence of quantum oscillations in magnetic double-well systems

    Energy Technology Data Exchange (ETDEWEB)

    Chudnovsky, Eugene M. E-mail: chudnov@lehman.cuny.edu

    2004-05-01

    Fundamental conservation laws mandate parameter-free generic mechanisms of decoherence of quantum oscillations in double-well systems. We consider two examples: tunneling of the magnetic moment in nanomagnets and tunneling between macroscopic current states in SQUIDs. In both cases the decoherence occurs via emission of phonons and photons at the oscillation frequency. We also show that in a system of identical qubits the decoherence greatly increases due to the superradiance of electromagnetic and sound waves. Our findings have important implications for building elements of quantum computers based upon nanomagnets and SQUIDs.

  14. Period doubling of azimuthal oscillations on a non-neutral magnetized electron column

    International Nuclear Information System (INIS)

    Boswell, R.W.

    1985-01-01

    The low-frequency azimuthal oscillations on a non-neutral magnetized electron column of very low density are investigated. A perturbation analysis of the slow mode of the rigid rotator equilibrium is developed to illustrate the nature of large-amplitude fundamental-mode oscillations. The results of this theoretical analysis show two important characteristics: firstly, as the perturbation amplitude is increased the wave form ceases to be purely sinusoidal and shows period doubling. Secondly, above a certain threshold, all harmonics of the wave grow and the wave breaks. The results of the former are compared with a simple electron beam experiment and are found to be in good qualitative agreement. (author)

  15. Transport of energetic electrons in a magnetically expanding helicon double layer plasma

    International Nuclear Information System (INIS)

    Takahashi, Kazunori; Charles, Christine; Boswell, Rod; Cox, Wes; Hatakeyama, Rikizo

    2009-01-01

    Peripheral magnetic field lines extending from the plasma source into the diffusion chamber are found to separate two regions of Maxwellian electron energy probability functions: the central, ion-beam containing region with an electron temperature of 5 eV, and region near the chamber walls with electrons at 3 eV. Along the peripheral field lines a bi-Maxwellian population with a hot tail at 9 eV is shown to both originate from electrons in the source traveling downstream across the double layer and correspond to a local maximum in ion and electron densities.

  16. Chemical spots on the surface of the strongly magnetic Herbig Ae star HD 101412

    DEFF Research Database (Denmark)

    Järvinen, S. P.; Hubrig, S.; Schöller, M.

    2016-01-01

    of HD 101412 were recently obtained on seven different epochs. Our study of the spectral variability over the part of the rotation cycle covered by HARPS observations reveals that the line profiles of the elements Mg, Si, Ca, Ti, Cr, Mn, Fe, and Sr are clearly variable while He exhibits variability...... that is opposite to the behaviour of the other elements studied. Since classical Ap stars usually show a relationship between the magnetic field geometry and the distribution of element spots, we used in our magnetic field measurements different line samples belonging to the three elements with the most numerous...... values determined in previous low-resolution FORS 2 measurements, where hydrogen Balmer lines are the main contributors to the magnetic field measurements, indicating the presence of concentration of the studied iron-peak elements in the region of the magnetic equator. Further, we discuss the potential...

  17. High-latitude ionospheric convection during strong interplanetary magnetic field B-y

    DEFF Research Database (Denmark)

    Huang, C.S.; Sofko, G.J.; Murr, D.

    1999-01-01

    . The interplanetary magnetic field (IMF) conditions corresponding to the occurrence of the ionospheric convection were B-x approximate to 1 nT, B-y approximate to 10 nT, and B-z ...An unusual high-latitude ionospheric pattern was observed on March 23, 1995. ionospheric convection appeared as clockwise merging convection cell focused at 84 degrees magnetic latitude around 1200 MLT. No signature of the viscous convection cell in the afternoon sector was observed...

  18. H2+ molecule in strong magnetic fields, studied by the method of linear combinations of orbitals

    International Nuclear Information System (INIS)

    de Melo, L.C.; Das, T.K.; Ferreira, R.C.; Miranda, L.C.M.; Brandi, H.S.

    1978-01-01

    We have studied the ground state of the H 2 + molecular ion in the presence of a homogeneous magnetic field, basing this study on a linear combination of atomic orbitals obtained from the hydrogen atom in a magnetic field. The calculations have shown that this scheme is adequate to describe the binding energy of the molecule at field strengths up to approximately 10 10 G

  19. Strong geomagnetic activity forecast by neural networks under dominant southern orientation of the interplanetary magnetic field

    Czech Academy of Sciences Publication Activity Database

    Valach, F.; Bochníček, Josef; Hejda, Pavel; Revallo, M.

    2014-01-01

    Roč. 53, č. 4 (2014), s. 589-598 ISSN 0273-1177 R&D Projects: GA AV ČR(CZ) IAA300120608; GA MŠk OC09070 Institutional support: RVO:67985530 Keywords : geomagnetic activity * interplanetary magnetic field * artificial neural network * ejection of coronal mass * X-ray flares Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 1.358, year: 2014

  20. Investigation of thin manganite films at strong pulsed electric and magnetic fields

    OpenAIRE

    Cimmperman, Piotras

    2006-01-01

    The main aim of this work was to investigate electrical conductivity of La-Ca(Sr)-MnO thin films at high pulsed electric and magnetic fields and to clear up the possibilities to use these materials for high pulsed magnetic field sensor and fault current limiter applications. The dissertation consists of the preface, six chapters, summary and main conclusions, references, list of publications and abstract (in Lithuanian). The main objectives of the work, scientific novelty, goals, valida...

  1. Crystal structure and magnetic properties of the double perovskite (Sr2-xCax)FeMoO6 (0≤x≤1.0)

    International Nuclear Information System (INIS)

    Liu, R.S.; Chan, T.S.; Hu, S.F.; Lin, J.G.; Huang, C.Y.

    2002-01-01

    We have investigated the crystal structure and magnetic properties of the new series of ordered double perovskite oxides (Sr 2-x Ca x )FeMoO 6 (0≤x≤1.0). A monotonous decrease of the lattice constants (a and c) has been found with increasing x. Such an effect may also give rise to a distorted structure with Fe-O-Mo angle changing from 180 deg. for x=0 to 162 deg. for x=1.0. The magnetization increases from x=0 to 0.5 and then slightly decreases from x=0.5 to 1.0. Such complex magnetic behavior is strongly correlated to the chemical size effect (corresponding to the internal pressure) in the title compounds

  2. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2012-06-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  3. Rapid Optimization of Double-Stators Switched Reluctance Motor with Equivalent Magnetic Circuit

    Directory of Open Access Journals (Sweden)

    Wu-Sung Yao

    2017-10-01

    Full Text Available The primary objective for this paper is to create a methodology to rapidly optimize double-stators switched reluctance motor (DSSRM. An analytical model of equivalent magnetic circuits for the air gap reluctances of aligned and unaligned positions is proposed and the optimal operation point of the magneto-motive force (MMF can be determined. Genetic algorithm (GA integrated of the proposed equivalent magnetic circuit is developed for rapid optimization of DSSRM to reach the maximum of the ratio of torque to volume of DSSRM. Compared to conventional switched reluctance motor (SRM, an illustrated example of a 3-KW three-phase 12-Slot-8-Pole DSSRM is used to verify the efficiency of the proposed method. Simplified 2-D electromagnetic models are analyzed and simulated. Finally, results of the analytical calculations and the finite-element analysis (FEA are validated by the proposed motor to show the accuracy of the designed strategy.

  4. Evidence for a low-temperature magnetic ground state in double-perovskite iridates with I r5 +(5 d4) ions

    Science.gov (United States)

    Terzic, J.; Zheng, H.; Ye, Feng; Zhao, H. D.; Schlottmann, P.; De Long, L. E.; Yuan, S. J.; Cao, G.

    2017-08-01

    We report an unusual magnetic ground state in single-crystal, double-perovskite B a2YIr O6 and Sr-doped B a2YIr O6 with I r5 +(5 d4) ions. Long-range magnetic order below 1.7 K is confirmed by dc magnetization, ac magnetic susceptibility, and heat-capacity measurements. The observed magnetic order is extraordinarily delicate and cannot be explained in terms of either a low-spin S =1 state, or a singlet Jeff=0 state imposed by the spin-orbit interactions (SOI). Alternatively, the magnetic ground state appears consistent with a SOI that competes with comparable Hund's rule coupling and inherently large electron hopping, which cannot stabilize the singlet Jeff=0 ground state. However, this picture is controversial, and conflicting magnetic behavior for these materials is reported in both experimental and theoretical studies, which highlights the intricate interplay of interactions that determine the ground state of materials with strong SOI.

  5. The Creation of a Strong Magnetic Field by Means of Large Magnetic Blocks from NdFeB Magnets in Opposing Linear Halbach Arrays

    Czech Academy of Sciences Publication Activity Database

    Žežulka, Václav; Straka, Pavel

    2016-01-01

    Roč. 21, č. 3 (2016), 364-373 ISSN 1226-1750 Institutional support: RVO:67985891 Keywords : magnetic field * permanent magnets * NdFeB magnets * Halbach Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.713, year: 2016 http://komag.org/journal/

  6. The double-gradient magnetic instability: Stabilizing effect of the guide field

    Energy Technology Data Exchange (ETDEWEB)

    Korovinskiy, D. B., E-mail: daniil.korovinskiy@gmail.com; Semenov, V. S.; Ivanova, V. V. [Saint Petersburg State University, 198504, Ulyanovskaya 1, Petrodvoretz (Russian Federation); Divin, A. V. [Saint Petersburg State University, 198504, Ulyanovskaya 1, Petrodvoretz (Russian Federation); Swedish Institute of Space Physics, SE-751 21 Uppsala (Sweden); Erkaev, N. V. [Institute of Computational Modelling, Russian Academy of Sciences, Siberian Branch, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Artemyev, A. V. [Space Research Institute RAS, Profsoyuznaya 84/32, Moscow 117997 (Russian Federation); Ivanov, I. B. [Saint Petersburg State University, 198504, Ulyanovskaya 1, Petrodvoretz (Russian Federation); Theoretical Physics Division, Petersburg Nuclear Physics Institute, 188300 Gatchina (Russian Federation); Lapenta, G. [Centrum voor Plasma-Astrofysica, Departement Wiskunde, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium); Markidis, S. [PDC Center for High Performance Computing, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Biernat, H. K. [Space Research Institute, Austrian Academy of Sciences, 8042 Graz (Austria); Institute of Physics, University of Graz, 8010 Graz (Austria)

    2015-01-15

    The role of the dawn-dusk magnetic field component in stabilizing of the magnetotail flapping oscillations is investigated in the double-gradient model framework (Erkaev et al., Phys. Rev. Lett. 99, 235003 (2007)), extended for the magnetotail-like configurations with non-zero guide field B{sub y}. Contribution of the guide field is examined both analytically and by means of linearized 2-dimensional (2D) and non-linear 3-dimensional (3D) MHD modeling. All three approaches demonstrate the same properties of the instability: stabilization of current sheet oscillations for short wavelength modes, appearing of the typical (fastest growing) wavelength λ{sub peak} of the order of the current sheet width, decrease of the peak growth rate with increasing B{sub y} value, and total decay of the mode for B{sub y}∼0.5 in the lobe magnetic field units. Analytical solution and 2D numerical simulations claim also the shift of λ{sub peak} toward the longer wavelengths with increasing guide field. This result is barely visible in 3D simulations. It may be accounted for the specific background magnetic configuration, the pattern of tail-like equilibrium provided by approximated solution of the conventional Grad-Shafranov equation. The configuration demonstrates drastically changing radius of curvature of magnetic field lines, R{sub c}. This, in turn, favors the “double-gradient” mode (λ > R{sub c}) in one part of the sheet and classical “ballooning” instability (λ < R{sub c}) in another part, which may result in generation of a “combined” unstable mode.

  7. Strong 3D and 1D magnetism in hexagonal Fe-chalcogenides FeS and FeSe vs. weak magnetism in hexagonal FeTe

    Energy Technology Data Exchange (ETDEWEB)

    Parker, David S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-06-13

    We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large Tc value is unlikely.

  8. Strong 3D and 1D magnetism in hexagonal Fe-chalcogenides FeS and FeSe vs. weak magnetism in hexagonal FeTe.

    Science.gov (United States)

    Parker, David S

    2017-06-13

    We present a comparative theoretical study of the hexagonal forms of the Fe-chalcogenides FeS, FeSe and FeTe with their better known tetragonal forms. While the tetragonal forms exhibit only an incipient antiferromagnetism and experimentally show superconductivity when doped, the hexagonal forms of FeS and FeSe display a robust magnetism. We show that this strong magnetism arises from a van Hove singularity associated with the direct Fe-Fe c-axis chains in the generally more three-dimensional NiAs structure. We also find that hexagonal FeTe is much less magnetic than the other two hexagonal materials, so that unconventional magnetically-mediated superconductivity is possible, although a large T c value is unlikely.

  9. Tuning the phase sensitivity of a double-lambda system with a static magnetic field.

    Science.gov (United States)

    Xu, Xiwei; Shen, Shuo; Xiao, Yanhong

    2013-05-20

    We study the effect of a DC magnetic field on the phase sensitivity of a double-lambda system coupled by two laser fields, a probe and a pump. It is demonstrated that the gain and the refractive index of the probe can be controlled by either the magnetic field or the relative phase between the two laser fields. More interestingly, when the system reduces to a single-lambda system, turning on the magnetic field transforms the system from a phase-insensitive process to a phase-sensitive one. In the pulsed-probe regime, we observed switching between slow and fast light when the magnetic field or the relative phase was adjusted. Experiments using a coated 87Rb vapor cell produced results in good agreement with our numerical simulation. This work provides a novel and simple means to manipulate phase sensitive electromagnetically-induced-transparency or four-wave mixing, and could be useful for applications in quantum optics, nonlinear optics and magnetometery based on such systems.

  10. Signatures of pairing in the magnetic excitation spectrum of strongly correlated two-leg ladders

    Science.gov (United States)

    Nocera, A.; Patel, N. D.; Dagotto, E.; Alvarez, G.

    2017-11-01

    Magnetic interactions are widely believed to play a crucial role in the microscopic mechanism leading to high critical temperature superconductivity. It is therefore important to study the signatures of pairing in the magnetic excitation spectrum of simple models known to show unconventional superconducting tendencies. Using the density matrix renormalization group technique, we calculate the dynamical spin structure factor S (k ,ω ) of a generalized t -U -J Hubbard model away from half filling in a two-leg ladder geometry. The addition of J enhances pairing tendencies. We analyze quantitatively the signatures of pairing in the magnetic excitation spectra. We found that the superconducting pair-correlation strength, that can be estimated independently from ground state properties, is closely correlated with the integrated low-energy magnetic spectral weight in the vicinity of (π ,π ) . In this wave-vector region, robust spin incommensurate features develop with increasing doping. The branch of the spectrum with rung direction wave vector krung=0 does not change substantially with doping where pairing dominates and thus plays a minor role. We discuss the implications of our results for neutron scattering experiments, where the spin excitation dynamics of hole-doped quasi-one-dimensional magnetic materials can be measured and also address implications for recent resonant inelastic x-ray scattering experiments.

  11. Layered Black Phosphorus: Strongly Anisotropic Magnetic, Electronic, and Electron-Transfer Properties.

    Science.gov (United States)

    Sofer, Zdeněk; Sedmidubský, David; Huber, Štěpán; Luxa, Jan; Bouša, Daniel; Boothroyd, Chris; Pumera, Martin

    2016-03-01

    Layered elemental materials, such as black phosphorus, exhibit unique properties originating from their highly anisotropic layered structure. The results presented herein demonstrate an anomalous anisotropy for the electrical, magnetic, and electrochemical properties of black phosphorus. It is shown that heterogeneous electron transfer from black phosphorus to outer- and inner-sphere molecular probes is highly anisotropic. The electron-transfer rates differ at the basal and edge planes. These unusual properties were interpreted by means of calculations, manifesting the metallic character of the edge planes as compared to the semiconducting properties of the basal plane. This indicates that black phosphorus belongs to a group of materials known as topological insulators. Consequently, these effects render the magnetic properties highly anisotropic, as both diamagnetic and paramagnetic behavior can be observed depending on the orientation in the magnetic field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. H32+ molecular ion in a strong magnetic field: Triangular configuration

    International Nuclear Information System (INIS)

    Lopez Vieyra, J.C.; Turbiner, A.V.

    2002-01-01

    The existence of the molecular ion H 3 2+ in a magnetic field in a triangular configuration is revised. A variational method with an optimization of the form of the vector potential (gauge fixing) is used. It is shown that in the range of magnetic fields 10 8 11 G the system (pppe), with the protons forming an equilateral triangle perpendicular to the magnetic line, has a well-pronounced minimum in the total energy. This configuration is unstable under the decays (H atom)+p+p and H 2 + +p. The triangular configuration of H 3 2+ complements H 3 2+ in the linear configuration that exists for B > or approx. 10 10 G

  13. H2+ molecular ion in a strong magnetic field: Ground state

    International Nuclear Information System (INIS)

    Turbiner, A. V.; Lopez Vieyra, J. C.

    2003-01-01

    A detailed quantitative analysis of the system of two protons and one electron (ppe) placed in magnetic field ranging from 10 9 -4.414x10 13 G is presented. The present study is focused on the question of the existence of the molecular ion H 2 + in a magnetic field. A variational method with an optimization of the form of the vector potential (optimal gauge fixing) is used as a tool. It is shown that in the domain of applicability of the nonrelativistic approximation the (ppe) system in the Born-Oppenheimer approximation has a well-pronounced minimum in the total energy at a finite interproton distance for B(less-or-similar sign)10 11 G, thus manifesting the existence of H 2 + . For B(greater-or-similar sign)10 11 G and large inclinations (of the molecular axis with respect to the magnetic line) the minimum disappears and hence the molecular ion H 2 + does not exist. It is shown that the most stable configuration of H 2 + always corresponds to protons situated along the magnetic line. With magnetic field growth the H 2 + ion becomes more and more tightly bound and compact, and the electronic distribution evolves from a two-peak to a one-peak pattern. The domain of inclinations where the H 2 + ion exists reduces with magnetic field increase and finally becomes 0 degree sign -25 degree sign at B=4.414x10 13 G. Phase-transition-type behavior of variational parameters for some interproton distances related to the beginning of the chemical reaction H 2 + ↔H+p is found

  14. Double Fano resonances in plasmonic nanocross molecules and magnetic plasmon propagation

    Science.gov (United States)

    Li, Guo-Zhou; Li, Qiang; Wu, Li-Jun

    2015-11-01

    Double Fano resonances in optical frequency are investigated in an artificial plasmonic molecule consisting of seven identical nanocrosses. These two Fano resonances are found to originate from different physical mechanisms. One is caused by the excitation of the inherent quadrupole dark mode supported by a single nanocross, and the other is attributed to the magnetic plasmon mode due to the generation of antiphase ring currents in adjacent fused tetramers. The two Fano resonances can either be tuned simultaneously or independently within a wide spectral range by adjusting the geometrical parameters of the nanocrosses. The excitation of the magnetic plasmon in a chain made of coupled nanoparticles allows for subwavelength guiding of optical energy with low radiative losses. The field decay length is as long as 2.608 μm, which is comparable to that of the magnetic plasmon waveguides and far surpasses the value achieved in electric plasmon counterparts. Because of the special shape of the nanocross, a Mach-Zehnder interferometer can be built to steer optical beams. These results show that the proposed plasmonic nanostructures have potential applications in biochemical sensing, narrow line-shape engineering and on-chip optical signal propagation in nanoscale integrated optics.Double Fano resonances in optical frequency are investigated in an artificial plasmonic molecule consisting of seven identical nanocrosses. These two Fano resonances are found to originate from different physical mechanisms. One is caused by the excitation of the inherent quadrupole dark mode supported by a single nanocross, and the other is attributed to the magnetic plasmon mode due to the generation of antiphase ring currents in adjacent fused tetramers. The two Fano resonances can either be tuned simultaneously or independently within a wide spectral range by adjusting the geometrical parameters of the nanocrosses. The excitation of the magnetic plasmon in a chain made of coupled

  15. Electromagnetic processes in pulsars under strong electric and magnetic field conditions

    International Nuclear Information System (INIS)

    Ayasli, S.; Hacinliyan, A.; Oegelman, H.B.; Daugherty, I.K.

    1977-01-01

    It is believed that pulsars possess huge electric and magnetic fields. However, the electric field is commonly neglected in calculations of the rate of pair production, a process which is thought to be greatly important in the radiation mechanisms of pulsars. To see the effect of the electric field, the pair production is calculated for arbitrary electric and magnetic field configurations. The formulae thus obtained are then applied to pulsars. It is shown that the correction to the ''polar gap'' height calculated in the Ruderman and Sutherland model is negligible, although it might be important for the spectrum of emerging photons. (author)

  16. Exchange interaction of strongly anisotropic tripodal erbium single-ion magnets with metallic surfaces

    DEFF Research Database (Denmark)

    Dreiser, Jan; Wäckerlin, Christian; Ali, Md. Ehesan

    2014-01-01

    We present a comprehensive study of Er(trensal) single-ion magnets deposited in ultrahigh vacuum onto metallic surfaces. X-ray photoelectron spectroscopy reveals that the molecular structure is preserved after sublimation, and that the molecules are physisorbed on Au(111) while they are chemisorbed....... Furthermore XMCD indicates a weak antiferromagnetic exchange coupling between the single-ion magnets and the ferromagnetic Ni/Cu(100) substrate. For the latter case, spin-Hamiltonian fits to the XMCD M(H) suggest a significant structural distortion of the molecules. Scanning tunneling microscopy reveals...

  17. Nonlinear dispersion of resonance extraordinary wave in a plasma with strong magnetic field

    International Nuclear Information System (INIS)

    Krasovitskiy, V. B.; Turikov, V. A.; Sotnikov, V. I.

    2007-01-01

    In this paper, the efficiency of electron acceleration by a short, powerful laser pulse propagating across an external magnetic field is investigated. Conditions for the decay of a laser pulse with frequency close to the upper hybrid resonance frequency are analyzed. It is also shown that a laser pulse propagating as an extraordinary wave in cold, magnetized, low-density plasma takes the form of a nonlinear wave with the modulated amplitude (envelope soliton). Finally, simulation results on the interaction of an electromagnetic pulse with a semi-infinite plasma, obtained with the help of an electromagnetic relativistic PIC code, are discussed and a comparison with the obtained theoretical results is presented

  18. Modulation of intersubband light absorption and interband photoluminescence in double GaAs/AlGaAs quantum wells under strong lateral electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Balagula, R. M., E-mail: rmbal@spbstu.ru; Vinnichenko, M. Ya., E-mail: mvin@spbstu.ru; Makhov, I. S.; Firsov, D. A.; Vorobjev, L. E. [Peter the Great Saint-Petersburg Polytechnic University (Russian Federation)

    2016-11-15

    The effect of a lateral electric field on the mid-infrared absorption and interband photoluminescence spectra in double tunnel-coupled GaAs/AlGaAs quantum wells is studied. The results obtained are explained by the redistribution of hot electrons between quantum wells and changes in the space charge in the structure. The hot carrier temperature is determined by analyzing the intersubband light absorption and interband photoluminescence modulation spectra under strong lateral electric fields.

  19. Path-integral calculation of the density of states in heavily doped strongly compensated semiconductors in a magnetic field

    International Nuclear Information System (INIS)

    Koinov, Z.G.; Yanchev, I.Y.

    1981-09-01

    The density of states in heavily doped strongly compansated semiconductors in a strong magnetic field is calculated by using the path-integral method. The case is considered when correlation exists in the impurity positions owing to the Coulomb interactions between the charged donors and acceptors during the high-temperature preparation of the samples. The semiclassical formula is rederived and corrections to it due to the long-range character of the potential and its short-range fluctuations are obtained. The density of states in the tail is studied and analytical results are given in the classical and quantum cases. (author)

  20. Onset of magnetic order in strongly-correlated systems from ab initio electronic structure calculations: application to transition metal oxides

    Science.gov (United States)

    Hughes, I. D.; Däne, M.; Ernst, A.; Hergert, W.; Lüders, M.; Staunton, J. B.; Szotek, Z.; Temmerman, W. M.

    2008-06-01

    We describe an ab initio theory of finite temperature magnetism in strongly-correlated electron systems. The formalism is based on spin density functional theory, with a self-interaction corrected local spin density approximation (SIC-LSDA). The self-interaction correction is implemented locally, within the Kohn-Korringa-Rostoker (KKR) multiple-scattering method. Thermally induced magnetic fluctuations are treated using a mean-field 'disordered local moment' (DLM) approach and at no stage is there a fitting to an effective Heisenberg model. We apply the theory to the 3d transition metal oxides, where our calculations reproduce the experimental ordering tendencies, as well as the qualitative trend in ordering temperatures. We find a large insulating gap in the paramagnetic state which hardly changes with the onset of magnetic order.

  1. Strong out-of-plane magnetic anisotropy in ion irradiated anatase TiO2 thin films

    Directory of Open Access Journals (Sweden)

    M. Stiller

    2016-12-01

    Full Text Available The temperature and field dependence of the magnetization of epitaxial, undoped anatase TiO2 thin films on SrTiO3 substrates was investigated. Low-energy ion irradiation was used to modify the surface of the films within a few nanometers, yet with high enough energy to produce oxygen and titanium vacancies. The as-prepared thin film shows ferromagnetism which increases after irradiation with low-energy ions. An optimal and clear magnetic anisotropy was observed after the first irradiation, opposite to the expected form anisotropy. Taking into account the experimental parameters, titanium vacancies as di-Frenkel pairs appear to be responsible for the enhanced ferromagnetism and the strong anisotropy observed in our films. The magnetic impurities concentrations was measured by particle-induced X-ray emission with ppm resolution. They are ruled out as a source of the observed ferromagnetism before and after irradiation.

  2. Imposed, ordered dust structures and other plasma features in a strongly magnetized plasma

    Science.gov (United States)

    Thomas, Edward; Leblanc, Spencer; Lynch, Brian; Konopka, Uwe; Merlino, Robert; Rosenberg, Marlene

    2015-11-01

    The Magnetized Dusty Plasma Experiment (MDPX) device has been in operation for just over one year. In that time, the MDPX device has been operating using a uniform magnetic field configuration up to 3.0 Tesla and has successfully produced plasmas and dusty plasmas at high magnetic fields. In these experimental studies, we have made observations of a new type of imposed, ordered structure in a dusty plasma at magnetic fields above 1 T. These dusty plasma structures are shown to scale inversely with neutral pressure and are shown to reflect the spatial structure of a wire mesh placed in the plasma. Additionally, recent measurements have been made that give insights into the effective potential that establishes the ordered structures in the plasma. In this presentation, we report on details of the imposed, ordered dusty plasma structure as well as filamentary features that also appear in the plasma and modify the confinement of the dusty plasma. This work is supported with funding from the NSF and Department of Energy.

  3. Parallel-beam correlation technique for measuring density fluctuations in plasmas with strong magnetic shear

    International Nuclear Information System (INIS)

    Jacobson, A.R.

    1981-04-01

    A laser diagnostic scheme is described which facilitates localization of density fluctuations along the line of sight. The method exploits both the generally observed anisotropy of density fluctuations in low-beta plasmas, as well as the twisting of the magnetic field which occurs across the minor diameter of reversed-field pinches, spheromaks, etc. Both interferometric and schlieren variations are discussed

  4. High-latitude ionospheric convection during strong interplanetary magnetic field B-y

    DEFF Research Database (Denmark)

    Huang, C.S.; Sofko, G.J.; Murr, D.

    1999-01-01

    . The interplanetary magnetic field (IMF) conditions corresponding to the occurrence of the ionospheric convection were B-x approximate to 1 nT, B-y approximate to 10 nT, and B-z y). We have compared our observations with statistical patterns and MHD numerical models for similar IMF...

  5. The Vlasov equation with strong magnetic field and oscillating electric field as a model for isotop resonant separation

    Directory of Open Access Journals (Sweden)

    Emmanuel Frenod

    2002-01-01

    Full Text Available We study the qualitative behavior of solutions to the Vlasov equation with strong external magnetic field and oscillating electric field. This model is relevant to the understanding of isotop resonant separation. We show that the effective equation is a kinetic equation with a memory term. This memory term involves a pseudo-differential operator whose kernel is characterized by an integral equation involving Bessel functions. The kernel is explicitly given in some particular cases.

  6. Tunable photonic crystal for THz radiation in layered superconductors: Strong magnetic-field dependence of the transmission coefficient

    International Nuclear Information System (INIS)

    Savel'ev, Sergey; Rakhmanov, A.L.; Nori, Franco

    2006-01-01

    Josephson plasma waves are scattered by the Josephson vortex lattice. This scattering results in a strong dependence, on the in-plane magnetic-field H ab , of the reflection and transmission of THz radiation propagating in layered superconductors. In particular, a tunable band-gap structure (THz photonic crystal) occurs in such a medium. These effects can be used, by varying H ab , for the selective frequency-filtering of THz radiation

  7. Current-density functional theory study of the H2 molecule evolving under a strong ultrashort magnetic field

    Science.gov (United States)

    Vikas, Hash(0xb7f6e60)

    2012-01-01

    Hydrogen molecule in a strong ultrashort magnetic field is investigated through a current-density functional theory (CDFT) and quantum fluid dynamics (QFD) based approach employing current-density dependent vector exchange-correlation potential and energy density functional derived with a vorticity variable. The numerical computations through the CDFT based approach are performed for the H2 molecule, starting initially from its field-free ground state, in a parallel internuclear axis and magnetic field-axis configuration with the internuclear separation R ranging from 0.1 a.u. to 14.0 a.u., and the strength of the time-dependent (TD) magnetic field varying between 0-1011 G over a few femtoseconds. The numerical results are compared with that obtained using an approach based on the current-density independent approximation under similar computational constraints but employing only scalar exchange-correlation potential dependent on the electronic charge-density alone. The current-density based approach yields exchange- and correlation energy as well as electronic charge-density of the H2 molecule drastically different from that obtained using current-independent approach, in particular, at TD magnetic field-strengths >109 G during a typical time-period of the field when the magnetic-field had attained maximum applied field-strength and is switched to a decreasing ramp function. This nonadiabatic behavior of the TD electronic charge-density is traced to the TD vorticity-dependent vector exchange-correlation potential of the CDFT based approach. The interesting electron dynamics of the H2 molecule in strong TD magnetic field is further elucidated by treating electronic charge-density as an `electron-fluid'. The present work also reveals interesting real-time dynamics on the attosecond time-scale in the electronic charge-density distribution of the hydrogen molecule.

  8. Hall effect in a strong magnetic field: Direct comparisons of compressible magnetohydrodynamics and the reduced Hall magnetohydrodynamic equations

    International Nuclear Information System (INIS)

    Martin, L. N.; Dmitruk, P.; Gomez, D. O.

    2010-01-01

    In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.

  9. Magnetic behavior of Ca{sub 2}NiWO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, C.A. [Area de Quimica General e Inorganica ' Dr. G.F.Puelles' , Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Curiale, J. [Centro Atomico Bariloche and Instituto Balseiro (UNCuyo), CNEA, Av. Bustillo 9500 (R8402AGP) S. C. de Bariloche, RN (Argentina); Viola, M. del C. [Area de Quimica General e Inorganica ' Dr. G.F.Puelles' , Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Pedregosa, J.C. [Area de Quimica General e Inorganica ' Dr. G.F.Puelles' , Facultad de Quimica, Bioquimica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina)]. E-mail: jpedreg@unsl.edu.ar; Sanchez, R.D. [Centro Atomico Bariloche and Instituto Balseiro (UNCuyo), CNEA, Av. Bustillo 9500 (R8402AGP) S. C. de Bariloche, RN (Argentina)]. E-mail: rodo@cab.cnea.gov.ar

    2007-09-01

    Polycrystalline Ca{sub 2}NiWO{sub 6} double perovskite has been prepared by solid-state reaction at 1150 C. The crystal structure of this material has been confirmed by X-ray powder diffraction (XRD). At room temperature, the crystal structure is monoclinic, space group P2{sub 1}/n, with a=5.4061(2) A, b=5.5389(2) A, c=7.6895(3) A, {beta}=90.232(2){sup o}. Magnetic susceptibility and electron spin resonance experiments on Ca{sub 2}NiWO{sub 6} show at high temperature a Curie-Weiss behavior with a {theta}=-75 K. From the Curie-Weiss behavior, the effective magnetic moment is 2.85{mu} {sub B}, which is in agreement with the presence of Ni{sup 2+} in the system. At low temperatures, below 52.5(0.2) K, the magnetic susceptibility shows antiferromagnetic behavior. From the experimental data and the mean field theory of antiferromagnetism we estimated the Ni interactions among the nearest Ni neighbors and the second nearest Ni neighbors.

  10. Double-magnetic-lens beta spectrometer for measurements of nucleus excited state lifetime

    International Nuclear Information System (INIS)

    Alikov, B.A.; Lizurej, G.I.; Muminov, T.M.; Ormandzhiev, S.I.; Salikhbaev, U.S.; Usmanov, R.R.; Kholbaev, I.

    1977-01-01

    Described is a design of an installation made on the basis of a double magnetic-lens beta spectrometer intended for measurement of lifetimes of nucleus excited states by the method of e-e-delayed coincidences. A system of the Hubert conic diaphragms is used in the spectrometer, and plastic scintillation detectors and photomultipliers are used as a registering system. The experimental arrangement is considered, and the main parameters of a stabilized current rectifier, developed for the supply of the spectrometer windings are given. Also presented is the lay-out of the time spectrometer of e-e-delayed coincidences which uses units of fast spectra metric electronics and the system of amplification stabilization. Besides, analytically studied were focusing characteristics of the magnetic-lens spectrometer for the case when the magnetic field shape may be considered triangular. Using the above installation obtained was the time spectrum of delayed coincidences between conversion electrons of K241 and K104 keV in a 136 E/ r nucleus, and determined was the half-life of 104 keV state (Tsub(1/2)=0.53+-0.02 ns) which is in a good agreement with the known value of Tsub(1/2)=0.52+-0.02 ns

  11. Flow of a two-dimensional liquid metal jet in a strong magnetic field

    International Nuclear Information System (INIS)

    Reed, C.B.; Molokov, S.

    2002-01-01

    Two-dimensional, steady flow of a liquid metal slender jet pouring from a nozzle in the presence of a transverse, nonuniform magnetic field is studied. The surface tension has been neglected, while gravity is shown to be not important. The main aim of the study is to evaluate the importance of the inertial effects. It has been shown that for gradually varying fields characteristic for the divertor region of a tokamak, inertial effects are negligible for N > 10, where N is the interaction parameter. Thus the inertialess flow model is expected to give good results even for relatively low magnetic fields and high jet velocity. Simple relations for the jet thickness and velocity have been derived. The results show that the jet becomes thicker if the field increases along the flow and thinner if it decreases

  12. Variational Monte Carlo calculations of lithium atom in strong magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Doma, S. B., E-mail: sbdoma@alexu.edu.eg [Alexandria University, Mathematics Department, Faculty of Science (Egypt); Shaker, M. O.; Farag, A. M. [Tanta University, Mathematics Department, Faculty of Science (Egypt); El-Gammal, F. N., E-mail: famta-elzahraa4@yahoo.com [Menofia University, Mathematics Department, Faculty of Science (Egypt)

    2017-01-15

    The variational Monte Carlo method is applied to investigate the ground state and some excited states of the lithium atom and its ions up to Z = 10 in the presence of an external magnetic field regime with γ = 0–100 arb. units. The effect of increasing field strength on the ground state energy is studied and precise values for the crossover field strengths were obtained. Our calculations are based on using accurate forms of trial wave functions, which were put forward in calculating energies in the absence of magnetic field. Furthermore, the value of Y at which ground-state energy of the lithium atom approaches to zero was calculated. The obtained results are in good agreement with the most recent values and also with the exact values.

  13. Magnetic field induced strong valley polarization in the three-dimensional topological semimetal LaBi

    Science.gov (United States)

    Kumar, Nitesh; Shekhar, Chandra; Klotz, J.; Wosnitza, J.; Felser, Claudia

    2017-10-01

    LaBi is a three-dimensional rocksalt-type material with a surprisingly quasi-two-dimensional electronic structure. It exhibits excellent electronic properties such as the existence of nontrivial Dirac cones, extremely large magnetoresistance, and high charge-carrier mobility. The cigar-shaped electron valleys make the charge transport highly anisotropic when the magnetic field is varied from one crystallographic axis to another. We show that the electrons can be polarized effectively in these electron valleys under a rotating magnetic field. We achieved a polarization of 60% at 2 K despite the coexistence of three-dimensional hole pockets. The valley polarization in LaBi is compared to the sister compound LaSb where it is found to be smaller. The performance of LaBi is comparable to the highly efficient bismuth.

  14. Magnetic susceptibility as a method of investigation of short-range order in strongly nonstoichiometric carbides

    International Nuclear Information System (INIS)

    Nazarova, S.Z.; Gusev, A.I.

    2001-01-01

    Magnetic susceptibility in disordered and ordered carbides of transition metals (M = Ti, Zr, Hf, Nb, Ta) was studied, the results are generalized. It was ascertained that the change in carbide susceptibility induced by deviation from stoichiometry stems from specific features of electronic spectra of the compounds. The use of magnetic susceptibility for determining structural disorder-order transitions is discussed. It is shown that change in the contribution made by orbital paramagnetism, resulting from short-range order formation, is the reason of decrease in susceptibility of nonstoichiometric carbides during the ordering. Experimentally obtained data on susceptibility permitted evaluating short- and far-range order parameters in NbC y , TaC y , TiC y and HfC y carbides [ru

  15. A kinetic model of retarding field analyser measurements in strongly magnetized, flowing, collisional plasmas

    Czech Academy of Sciences Publication Activity Database

    Gunn, J. P.; Fuchs, Vladimír; Kočan, M.

    2013-01-01

    Roč. 55, č. 4 (2013), 045012-045012 ISSN 0741-3335 R&D Projects: GA MŠk 7G10072 Institutional support: RVO:61389021 Keywords : plasma * collisions * magnetic field * retarding field analyzer Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.386, year: 2013 http://iopscience.iop.org/0741-3335/55/4/045012/pdf/0741-3335_55_4_045012.pdf

  16. The LACARA Vacuum Laser Accelerator Experiment: Beam Positioning and Alignment in a Strong Magnetic Field

    International Nuclear Information System (INIS)

    Shchelkunov, Sergey V.; Marshall, T. C.; Hirshfield, J. L.; Wang, Changbiao; LaPointe, M. A.

    2006-01-01

    LACARA (laser cyclotron auto-resonance accelerator) is a vacuum laser accelerator of electrons that is under construction at the Accelerator Test Facility (ATF), Brookhaven National Laboratory. It is expected that the experiment will be assembled by September 2006; this paper presents progress towards this goal. According to numerical studies, as an electron bunch moves along the LACARA solenoidal magnetic field (∼5.2 T, length ∼1 m), it will be accelerated from 50 to ∼75 MeV by interacting with a 0.8 TW Gaussian-mode circularly polarized optical pulse provided by the ATF CO2 10.6μm laser system. The LACARA laser transport optics must handle 10 J and be capable of forming a Gaussian beam inside the solenoid with a 1.4 mm waist and a Rayleigh range of 60 cm. The electron optics must transport a bunch having input emittance of 0.015 mm-mrad and 100 μm waist through the magnet. Precision alignment between the electron beam and the solenoid magnetic axis is required, and a method to achieve this is described in detail. Emittance- filtering may be necessary to yield an accelerated bunch having a narrow (∼1%) energy-spread

  17. High gain and double phase conjugation with strongly doped CO:BaTiO 3 in reflection grating configurations

    Science.gov (United States)

    Glick, Yaakov; Sternklar, Shmuel

    1997-02-01

    A study of highly doped photorefractive Co:BaTiO 3 reveals its usefulness for wave mixing through reflection grating interactions. Gain and noise figures are characterized for a counter-propagating pump-signal amplifier. Gain as high as 3 × 10 7, extraction efficiency as high as 40% and noise equivalent power as low as 0.15 pW were demonstrated. To the best of our knowledge this is the highest photorefractive gain reported to date. In addition the double phase conjugate mirror (DPCM) is operated in a reflection grating geometry. High absorption limits the DPCM reflectivity to about 1%.

  18. Structural analysis of mixed alkali borosilicate glasses containing Cs+ and Na+ using strong magnetic field magic angle spinning nuclear magnetic resonance

    Directory of Open Access Journals (Sweden)

    S. Kaneko

    2017-03-01

    Full Text Available We have investigated the local structure of alkali atoms in mixed alkali silicate, borate, and borosilicate glasses, which contain Cs+ and Na+, using strong magnetic field magic angle spinning nuclear magnetic resonance (MAS NMR spectroscopy of 133Cs and 23Na. The spectral peaks of 133Cs in borosilicate (Si:B = 1:1 and Si-rich borosilicate (Si:B = 2:1 glasses shifted to upfield with increasing Cs+/(Na+ + Cs+ ratio, which implies that the coordination number of Cs+ decreased as in the case of silicate and borate glasses. However, this trend was not observed in the 23Na spectra of either borosilicate glass. This might be because the chemical shift of 23Na in borosilicate glass is strongly affected by nearby species such as Si or B, and not by the coordination number of Na+.

  19. Magnetic ordering of divalent europium in double perovskites Eu2LnTaO6 (Ln=rare earths)

    International Nuclear Information System (INIS)

    Misawa, Yoshitaka; Doi, Yoshihiro; Hinatsu, Yukio

    2011-01-01

    Structures and magnetic properties of double perovskite-type oxides Eu 2 LnTaO 6 (Ln=Eu, Dy-Lu) were investigated. These compounds adopt a distorted double perovskite structure with space group P2 1 /n. Magnetic susceptibility, specific heat, and 151 Eu Moessbauer spectrum measurements show that the Eu 2+ ions at the 12-coordinate sites of the perovskite structure are antiferromagnetically ordered at ∼4 K, and that Ln 3+ ions at the 6-coordinate site are in the paramagnetic state down to 1.8 K. - Graphical abstract: Magnetic properties of double perovskite-type oxides Eu 2 LnTaO 6 (Ln=Eu, Dy-Lu) were investigated. Magnetic susceptibility, specific heat, and 151 Eu Moessbauer spectrum measurements show that the Eu 2+ ions at the 12-coordinate sites of the perovskite structure are antiferromagnetically ordered at ∼4 K. Highlights: → Crystal structures of double perovskites Eu 2 LnTaO 6 (Ln=rare earth) were determined. → We found that these compounds show an antiferromagnetic ordering at ∼4 K. → The magnetic ordering is due to the interactions of Eu 2+ ions. → It was elucidated by specific heat and 151 Eu Moessbauer spectrum measurements.

  20. Vlasov simulations of self generated strong magnetic fields in plasmas and laser-plasma interaction

    Directory of Open Access Journals (Sweden)

    Inglebert A.

    2013-11-01

    Full Text Available A new formulation based on Hamiltonian reduction technique using the invariance of generalized canonical momentum is introduced for the study of relativistic Weibel-type instability. An example of application is given for the current filamentation instability resulting from the propagation of two counter-streaming electron beams in the relativistic regime of the instability. This model presents a double advantage. From an analytical point of view, the method is exact and standard fluid dispersion relations for Weibel or filamentation instabilies can be recovered. From a numerical point of view, the method allows a drastic reduction of the computational time. A 1D multi-stream Vlasov-Maxwell code is developed using such dynamical invariants in the perpendicular momentum space. Numerical comparison with a full Vlasov-Maxwell system has also been carried out to show the efficiency of this reduction technique.

  1. QCD in magnetic field, Landau levels and double-life of unbroken center-symmetry

    Science.gov (United States)

    Anber, Mohamed M.; Ünsal, Mithat

    2014-12-01

    We study the thermal confinement/deconfinement and non-thermal quantum phase transitions or rapid cross-overs in QCD and QCD-like theories in external magnetic fields. At large magnetic fields, while the contribution of gauge fluctuations to Wilson-line potential remains unaltered at one-loop order, the contribution of fermions effectively becomes two lower dimensional and is enhanced by the density of states of the lowest Landau level (LLL). In a spatial compactification and for heavy adjoint fermions, this enhancement leads to a calculable zero temperature quantum phase transition on driven by a competition between the center-destabilizing gauge contribution and center-stabilizing LLL fermions. We also show that at a (formal) asymptotically large magnetic field, the adjoint fermions with arbitrarily large but fixed mass stabilize the center symmetry. This is an exotic case of simultaneous non-decoupling of large mass fermions (due to the enhancement by the LLL density of states) and decoupling from the low energy effective field theory. This observation has important implications for both Hosotani mechanism, for which gauge symmetry "breaking" occurs, and large- N volume independence (Eguchi-Kawai reduction), for which gauge structure is never "broken". Despite sounding almost self-contradictory, we carefully explain the physical scales entering the problem, double-meaning of unbroken center symmetry and how a clash is avoided. We also identify, for both thermal and spatial compactification, the jump in magnetic susceptibility as an order parameter for the deconfinement transition. The predictions of our analysis are testable by using current lattice techniques.

  2. Magnetic study of a few antiferromagnets in very-strong pulsed fields (450 kOE)

    International Nuclear Information System (INIS)

    Krebs, J.

    1968-01-01

    In this thesis we describe a pulsed field device with which we obtain magnetization curves up to 450 kOE at all temperatures between 1. 6 and 300. We have studied the 'spin-flopping'(and therefore the anisotropy) in MnF 2 versus temperature, below the Neel point. We have also studied the antiferromagnets MnSO 4 . and MnSO 4 .H 2 O which have revealed saturation fields respectively of 250 kOE and 320 kOE. (author) [fr

  3. Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes

    Science.gov (United States)

    Salvesen, Greg; Simon, Jacob B.; Armitage, Philip J.; Begelman, Mitchell C.

    2016-03-01

    Strongly magnetized accretion discs around black holes have attractive features that may explain enigmatic aspects of X-ray binary behaviour. The structure and evolution of these discs are governed by a dynamo-like mechanism, which channels part of the accretion power liberated by the magnetorotational instability (MRI) into an ordered toroidal magnetic field. To study dynamo activity, we performed three-dimensional, stratified, isothermal, ideal magnetohydrodynamic shearing box simulations. The strength of the self-sustained toroidal magnetic field depends on the net vertical magnetic flux, which we vary across almost the entire range over which the MRI is linearly unstable. We quantify disc structure and dynamo properties as a function of the initial ratio of mid-plane gas pressure to vertical magnetic field pressure, β _0^mid = p_gas / p_B. For 10^5 ≥ β _0^mid ≥ 10 the effective α-viscosity parameter scales as a power law. Dynamo activity persists up to and including β _0^mid = 10^2, at which point the entire vertical column of the disc is magnetic pressure dominated. Still stronger fields result in a highly inhomogeneous disc structure, with large density fluctuations. We show that the turbulent steady state βmid in our simulations is well matched by the analytic model of Begelman et al. describing the creation and buoyant escape of toroidal field, while the vertical structure of the disc can be broadly reproduced using this model. Finally, we discuss the implications of our results for observed properties of X-ray binaries.

  4. Output voltage calculations in double barrier magnetic tunnel junctions with asymmetric voltage behavior

    KAUST Repository

    Useinov, Arthur

    2011-10-22

    In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR-V curves, output voltages and I-V characteristics for negative and positive values of applied voltages were carried out using MTJs with CoFeB/MgO interfaces as an example. Asymmetry of the experimental TMR-V curves is explained by different values of the minority and majority Fermi wave vectors for the left and right sides of the tunnel barrier, which arises due to different annealing regimes. Electron tunneling in DMTJs was simulated in two ways: (i) Coherent tunneling, where the DMTJ is modeled as one tunnel system and (ii) consecutive tunneling, where the DMTJ is modeled by two single barrier junctions connected in series. © 2012 Elsevier B.V. All rights reserved.

  5. Density-matrix-functional calculations for matter in strong magnetic fields: Ground states of heavy atoms

    DEFF Research Database (Denmark)

    Johnsen, Kristinn; Yngvason, Jakob

    1996-01-01

    We report on a numerical study of the density matrix functional introduced by Lieb, Solovej, and Yngvason for the investigation of heavy atoms in high magnetic fields. This functional describes exactly the quantum mechanical ground state of atoms and ions in the limit when the nuclear charge Z...... and the electron number N tend to infinity with N/Z fixed, and the magnetic field B tends to infinity in such a way that B/Z4/3→∞. We have calculated electronic density profiles and ground-state energies for values of the parameters that prevail on neutron star surfaces and compared them with results obtained...... by other methods. For iron at B=1012 G the ground-state energy differs by less than 2% from the Hartree-Fock value. We have also studied the maximal negative ionization of heavy atoms in this model at various field strengths. In contrast to Thomas-Fermi type theories atoms can bind excess negative charge...

  6. A strong, highly-tilted interstellar magnetic field near the Solar System.

    Science.gov (United States)

    Opher, M; Bibi, F Alouani; Toth, G; Richardson, J D; Izmodenov, V V; Gombosi, T I

    2009-12-24

    Magnetic fields play an important (sometimes dominant) role in the evolution of gas clouds in the Galaxy, but the strength and orientation of the field in the interstellar medium near the heliosphere has been poorly constrained. Previous estimates of the field strength range from 1.8-2.5 microG and the field was thought to be parallel to the Galactic plane or inclined by 38-60 degrees (ref. 2) or 60-90 degrees (ref. 3) to this plane. These estimates relied either on indirect observational inferences or modelling in which the interstellar neutral hydrogen was not taken into account. Here we report measurements of the deflection of the solar wind plasma flows in the heliosheath to determine the magnetic field strength and orientation in the interstellar medium. We find that the field strength in the local interstellar medium is 3.7-5.5 microG. The field is tilted approximately 20-30 degrees from the interstellar medium flow direction (resulting from the peculiar motion of the Sun in the Galaxy) and is at an angle of about 30 degrees from the Galactic plane. We conclude that the interstellar medium field is turbulent or has a distortion in the solar vicinity.

  7. Strong coupling operation of a free-electron-laser amplifier with an axial magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Rullier, J.L.; Devin, A.; Gardelle, J.; Labrouche, J.; Le Taillandier, P. [Commissariat a lEnergie Atomique, Boite Postale 2, 33114 Le Barp (France); Donohue, J.T. [Centre dEtudes Nucleaires de Bordeaux-Gradignan, Boite Postale 120, 33175 Gradignan (France)

    1996-03-01

    We present the results of a free-electron-laser (FEL) experiment at 35 GHz, using a strongly relativistic electron beam ({ital T}=1.75 MeV). The electron pulse length is 30 ns full width at half maximum with a peak current of 400 A. The FEL is designed to operate in the high-gain Compton regime, with a negative coupling parameter ({Phi}{lt}0) leading to a strong growth rate. More than 50 MW of rf power in the TE{sub 1}{sub 1} mode (43 dB gain) has been obtained with good reproducibility. The experimental results are in good agreement with predictions made using the three-dimensional stationary simulation code solitude. {copyright} {ital 1996 The American Physical Society.}

  8. The dynamics of magnetic Rossby waves in spherical dynamo simulations: A signature of strong-field dynamos?

    Science.gov (United States)

    Hori, K.; Teed, R. J.; Jones, C. A.

    2018-03-01

    We investigate slow magnetic Rossby waves in convection-driven dynamos in rotating spherical shells. Quasi-geostrophic waves riding on a mean zonal flow may account for some of the geomagnetic westward drifts and have the potential to allow the toroidal field strength within the planetary fluid core to be estimated. We extend the work of Hori et al. (2015) to include a wider range of models, and perform a detailed analysis of the results. We find that a predicted dispersion relation matches well with the longitudinal drifts observed in our strong-field dynamos. We discuss the validity of our linear theory, since we also find that the nonlinear Lorentz terms influence the observed waveforms. These wave motions are excited by convective instability, which determines the preferred azimuthal wavenumbers. Studies of linear rotating magnetoconvection have suggested that slow magnetic Rossby modes emerge in the magnetostrophic regime, in which the Lorentz and Coriolis forces are in balance in the vorticity equation. We confirm this to be predominant balance for the slow waves we have detected in nonlinear dynamo systems. We also show that a completely different wave regime emerges if the magnetic field is not present. Finally we report the corresponding radial magnetic field variations observed at the surface of the shell in our simulations and discuss the detectability of these waves in the geomagnetic secular variation.

  9. Double coating protection of Nd–Fe–B magnets: Intergranular phosphating treatment and copper plating

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jingwu; Chen, Haibo; Qiao, Liang [College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Lin, Min [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology and Engineering Chinese Academy of Science, Ningbo 315201 (China); Jiang, Liqiang; Che, Shenglei [College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Hu, Yangwu, E-mail: 346648086@qq.com [College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014 (China); Wenzhou Institute of Industry and Science, Wenzhou 325000 (China)

    2014-12-15

    In this work, a double coating protection technique of phosphating treatment and copper plating was made to improve the corrosion resistance of sintered Nd–Fe–B magnets. In other words, the intergranular region of sintered Nd–Fe–B is allowed to generate passive phosphate conversion coating through phosphating treatment, followed by the copper coating on the surface of sintered Nd–Fe–B. The morphology and corrosion resistance of the phosphated sintered Nd–Fe–B were observed using SEM and electrochemical method respectively. The phosphate conversion coating was formed more preferably on the intergranular region of sintered Nd–Fe–B than on the main crystal region; just after a short time of phosphating treatment, the intergranular region of sintered Nd–Fe–B has been covered by the phosphate conversion coating and the corrosion resistance is significantly improved. With the synergistic protection of the intergranular phosphorization and the followed copper electrodeposition, the corrosion resistance of the sintered Nd–Fe–B is significantly better than that with a single phosphate film or single plating protection. - Highlights: • We combined intergranular phosphating and copper plating to protect Nd–Fe–B. • The phosphate conversion coating was formed preferably on the intergranular region. • The phosphating coating can obviously improve the corrosion resistance of Nd–Fe–B. • The corrosion resistance of Nd–Fe–B was improved by double coating protection.

  10. Double-outlet right ventricle: morphologic demonstration using nuclear magnetic resonance imaging.

    Science.gov (United States)

    Parsons, J M; Baker, E J; Anderson, R H; Ladusans, E J; Hayes, A; Fagg, N; Cook, A; Qureshi, S A; Deverall, P B; Maisey, M N

    1991-07-01

    Sixteen patients with double-outlet right ventricle, aged 1 week to 29 years (median 5 months), were studied with a 1.5 tesla nuclear magnetic resonance (NMR) imaging scanner. Two-dimensional echocardiography was performed in all patients. Thirteen patients underwent angiography, including nine who underwent subsequent surgical correction. Three patients underwent postmortem examination. Small children and infants were scanned inside a 32 cm diameter proton head coil. Multiple 5 mm thick sections separated by 0.5 mm and gated to the patient's electrocardiogram were acquired with a spin-echo sequence and an echo time of 30 ms. A combination of standard and oblique imaging planes was used. Imaging times were less than 90 min. The NMR images were technically unsuitable in one patient because of excessive motion artifact. In the remaining patients, the diagnosis of double outlet right ventricle was confirmed and correlated with surgical and postmortem findings. The NMR images were particularly valuable in demonstrating the interrelations between the great arteries and the anatomy of the outlet septum and the spatial relations between the ventricular septal defect and the great arteries. Although the atrioventricular (AV) valves were not consistently demonstrated, NMR imaging in two patients identified abnormalities of the mitral valve that were not seen with two-dimensional echocardiography. In one patient who had a superoinferior arrangement of the ventricles, NMR imaging was the most useful imaging technique for demonstrating the anatomy. In patients with double-outlet right ventricle, NMR imaging can provide clinically relevant and accurate morphologic information that may contribute to future improvement in patient management.

  11. Numerical analysis of magnetic field effects on hydro-thermal behavior of a magnetic nanofluid in a double pipe heat exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Shakiba, Ali, E-mail: Shakiba7858@yahoo.com [Department of Mechanical Engineering, Mazandaran Institute of Technology, Babol (Iran, Islamic Republic of); Vahedi, Khodadad, E-mail: Khvahedi@ihu.ac.ir [Department of Mechanical Engineering, Imam Hossein University, Tehran (Iran, Islamic Republic of)

    2016-03-15

    This study attempts to numerically investigate the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe{sub 3}O{sub 4}) in a counter-current horizontal double pipe heat exchanger, which is exposed to a non-uniform transverse magnetic field with different intensities. The magnetic field is generated by an electric current going through a wire located parallel to the inner tube and between two pipes. The single phase model and the control volume technique have been used to study the flow. The effects of magnetic field have been added to momentum equation by applying C++ codes in Ansys Fluent 14. The results show that applying this kind of magnetic field causes kelvin force to be produced perpendicular to the ferrofluid flow, changing axial velocity profile and creating a pair of vortices which leads to an increase in Nusselt number, friction factor and pressure drop. Comparing the enhancement percentage of Nusselt number, friction factor and pressure drop demonstrates that the optimum value of magnetic number for Re{sub ff}=50 is between Mn=1.33×10{sup 6} and Mn=2.37×10{sup 6}. So applying non-uniform transverse magnetic field can control the flow of ferrofluid and improve heat transfer process of double pipe heat exchanger. - Highlights: • Effect of applying non-uniform transverse magnetic field on a ferrofluid for enhancing the cooling process in a double pipe heat exchanger is investigated. • Heat exchanger is exposed to a non-uniform transverse magnetic field with different intensities. • The magnetic field is generated by an electric current going through a wire located parallel to inner tube and between two pipes. • Applying this field produces kelvin force to change axial velocity profile and creating a pair of vortices increasing Nusselt number, friction factor and pressure drop.

  12. Atomic ordering and magnetic properties of non-stoichiometric double-perovskite Sr sub 2 Fe sub x Mo sub 2 sub - sub x O sub 6

    CERN Document Server

    Liu, G Y; Feng, X M; Yang, H F; Ouyang, Z W; Liu, W F; Liang, J K

    2003-01-01

    The crystal structure and magnetic properties of a new series of ordered double-perovskite oxides Sr sub 2 Fe sub x Mo sub 2 sub - sub x O sub 6 (0.8 <= x <= 1.5) have been studied. The crystal structure changes from a tetragonal I4/mmm lattice to a cubic Fm3-bar m lattice around x = 1.2. The degree of ordering in Sr sub 2 Fe sub x Mo sub 2 sub - sub x O sub 6 exhibits a maximal at x = 0.95 and decreases as x deviates from 0.95. The saturated magnetization increases from x = 0.8 to 0.95 and then decreases from x = 0.95 to 1.5. The Curie temperature exhibits an abrupt drop around x = 1.2, where the structural transition takes place. These complex behaviours are strongly correlated to antisite defect concentration in the compounds.

  13. On the thermoelectric power in degenerate narrow gap semiconductors in the presence of a strong magnetic field

    International Nuclear Information System (INIS)

    Ghatak, K.P.; De, B.

    1991-01-01

    In this paper the authors have studied the thermoelectric power under strong magnetic field in degenerate semiconductors on the basis of fourth order in affective mass theory and taking into account the interactions of the conduction electrons, heavy-holes, light-holes and split-off holes respectively. The results obtained are then compared to those derived on the basis of the well-known three-band Kane model. It is found, taking n-Hg 1-x Cd x Te as an example, that the magneto-thermo power increases with decreasing electron concentration and increasing magnetic field respectively for both the models in an oscillatory way. The oscillations are due to SdH effects and the theoretical analysis in accordance with fourth order in effective mass theory i in agreement with the experimental observation as reported elsewhere. In addition, the corresponding results for parabolic energy bands have also been obtained as special cases of our generalized formulations

  14. Preparation of cold ions in strong magnetic field and its application to gas-phase NMR spectroscopy

    International Nuclear Information System (INIS)

    Fuke, K.; Ohshima, Y.; Tona, M.

    2015-01-01

    Nuclear Magnetic Resonance (NMR) technique is widely used as a powerful tool to study the physical and chemical properties of materials. However, this technique is limited to the materials in condensed phases. To extend this technique to the gas-phase molecular ions, we are developing a gas-phase NMR apparatus. In this note, we describe the basic principle of the NMR detection for molecular ions in the gas phase based on a Stern-Gerlach type experiment in a Penning trap and outline the apparatus under development. We also present the experimental procedures and the results on the formation and the manipulation of cold ions under a strong magnetic field, which are the key techniques to detect the NMR by the present method

  15. Analytical GIAO and hybrid-basis integral derivatives: application to geometry optimization of molecules in strong magnetic fields.

    Science.gov (United States)

    Tellgren, Erik I; Reine, Simen S; Helgaker, Trygve

    2012-07-14

    Analytical integral evaluation is a central task of modern quantum chemistry. Here we present a general method for evaluating differentiated integrals over standard Gaussian and mixed Gaussian/plane-wave hybrid orbitals. The main idea is to have a representation of basis sets that is flexible enough to enable differentiated integrals to be reinterpreted as standard integrals over modified basis functions. As an illustration of the method, we report a very simple implementation of Hartree-Fock level geometrical derivatives in finite magnetic fields for gauge-origin independent atomic orbitals, within the London program. As a quantum-chemical application, we optimize the structure of helium clusters and some well-known covalently bound molecules (water, ammonia and benzene) subject to strong magnetic fields.

  16. Magnetic properties of Hf177 and Hf180 in the strong-coupling deformed model

    Science.gov (United States)

    Muto, S.; Stone, N. J.; Bingham, C. R.; Stone, J. R.; Walker, P. M.; Audi, G.; Gaulard, C.; Köster, U.; Nikolov, J.; Nishimura, K.; Ohtsubo, T.; Podolyak, Z.; Risegari, L.; Simpson, G. S.; Veskovic, M.; Walters, W. B.

    2014-04-01

    This paper reports NMR measurements of the magnetic dipole moments of two high-K isomers, the 37/2-, 51.4 m, 2740 keV state in Hf177 and the 8-, 5.5 h, 1142 keV state in Hf180 by the method of on-line nuclear orientation. Also included are results on the angular distributions of γ transitions in the decay of the Hf177 isotope. These yield high precision E2/M1 multipole mixing ratios for transitions in bands built on the 23/2+, 1.1 s, isomer at 1315 keV and on the 9/2+, 0.663 ns, isomer at 321 keV. The new results are discussed in the light of the recently reported finding of systematic dependence of the behavior of the gR parameter upon the quasiproton and quasineutron make up of high-K isomeric states in this region.

  17. Dst Index in the 2008 GEM Modeling Challenge - Model Performance for Moderate and Strong Magnetic Storms

    Science.gov (United States)

    Rastaetter, Lutz; Kuznetsova, Maria; Hesse, Michael; Chulaki, Anna; Pulkkinen, Antti; Ridley, Aaron J.; Gombosi, Tamas; Vapirev, Alexander; Raeder, Joachim; Wiltberger, Michael James; hide

    2010-01-01

    The GEM 2008 modeling challenge efforts are expanding beyond comparing in-situ measurements in the magnetosphere and ionosphere to include the computation of indices to be compared. The Dst index measures the largest deviations of the horizontal magnetic field at 4 equatorial magnetometers from the quiet-time background field and is commonly used to track the strength of the magnetic disturbance of the magnetosphere during storms. Models can calculate a proxy Dst index in various ways, including using the Dessler-Parker Sckopke relation and the energy of the ring current and Biot-Savart integration of electric currents in the magnetosphere. The GEM modeling challenge investigates 4 space weather events and we compare models available at CCMC against each other and the observed values of Ost. Models used include SWMF/BATSRUS, OpenGGCM, LFM, GUMICS (3D magnetosphere MHD models), Fok-RC, CRCM, RAM-SCB (kinetic drift models of the ring current), WINDMI (magnetosphere-ionosphere electric circuit model), and predictions based on an impulse response function (IRF) model and analytic coupling functions with inputs of solar wind data. In addition to the analysis of model-observation comparisons we look at the way Dst is computed in global magnetosphere models. The default value of Dst computed by the SWMF model is for Bz the Earth's center. In addition to this, we present results obtained at different locations on the Earth's surface. We choose equatorial locations at local noon, dusk (18:00 hours), midnight and dawn (6:00 hours). The different virtual observatory locations reveal the variation around the earth-centered Dst value resulting from the distribution of electric currents in the magnetosphere during different phases of a storm.

  18. Effect of a dc magnetic field on the magnetization relaxation of uniaxial single-domain ferromagnetic particles driven by a strong ac magnetic field

    International Nuclear Information System (INIS)

    Dejardin, Pierre-Michel; Kalmykov, Yuri P.

    2010-01-01

    The nonlinear ac stationary response of the magnetization of noninteracting uniaxial single-domain ferromagnetic particles acted on by superimposed dc and ac magnetic fields applied along the anisotropy axis is evaluated from the Fokker-Planck equation, expressed as an infinite hierarchy of recurrence equations for Fourier components of the relaxation functions governing longitudinal relaxation of the magnetization. The exact solution of this hierarchy comprises a matrix continued fraction, allowing one to evaluate the ac nonlinear response and reversal time of the magnetization. For weak ac fields, the results agree with perturbation theory. It is shown that the dc bias field changes substantially the magnetization dynamics leading to new nonlinear effects. In particular, it is demonstrated that for a nonzero bias field as the magnitude of the ac field increases the reversal time first increases and having attained its maximum at some critical value of the ac field, decreases exponentially.

  19. Photometric variability in a warm, strongly magnetic DQ white dwarf, SDSS J103655.39+652252.2

    International Nuclear Information System (INIS)

    Williams, Kurtis A.; Winget, D. E.; Montgomery, M. H.; Hermes, J. J.; Falcon, Ross E.; Winget, K. I.; Dufour, Patrick; Kepler, S. O.; Bolte, Michael; Rubin, Kate H. R.; Liebert, James

    2013-01-01

    We present the discovery of photometric variability in the DQ white dwarf SDSS J103655.39+652252.2 (SDSS J1036+6522). Time-series photometry reveals a coherent monoperiodic modulation at a period of 1115.64751(67) s with an amplitude 0.442% ± 0.024%; no other periodic modulations are observed with amplitudes ≳ 0.13%. The period, amplitude, and phase of this modulation are constant within errors over 16 months. The spectrum of SDSS J1036+6522 shows magnetic splitting of carbon lines, and we use Paschen-Back formalism to develop a grid of model atmospheres for mixed carbon and helium atmospheres. Our models, while reliant on several simplistic assumptions, nevertheless match the major spectral and photometric properties of the star with a self-consistent set of parameters: T eff ≈ 15, 500 K, log g ≈ 9, log (C/He) = –1.0, and a mean magnetic field strength of 3.0 ± 0.2 MG. The temperature and abundances strongly suggest that SDSS J1036+6522 is a transition object between the hot, carbon-dominated DQs and the cool, helium-dominated DQs. The variability of SDSS J1036+6522 has characteristics similar to those of the variable hot carbon-atmosphere white dwarfs (DQVs), however, its temperature is significantly cooler. The pulse profile of SDSS J1036+6522 is nearly sinusoidal, in contrast with the significantly asymmetric pulse shapes of the known magnetic DQVs. If the variability in SDSS J1036+6522 is due to the same mechanism as other DQVs, then the pulse shape is not a definitive diagnostic on the absence of a strong magnetic field in DQVs. It remains unclear whether the root cause of the variability in SDSS J1036+6522 and the other hot DQVs is the same.

  20. On the theory of stationary charged particle ensembles in strongly non-homogeneous azimuthally symmetric magnetic fields

    International Nuclear Information System (INIS)

    Auluck, S.K.H.

    1982-01-01

    A method of treating problems involving strongly nonadiabatic particle orbits in a magnetic field is described for the case when the system is long-lived on the collisional time scale. A canonical distribution P=Z -1 exp-β(H+Ωpsub(theta)) results from maximization of entropy subject to conservation of the Hamiltonian H and canonical angular momentum psub(theta) for an azimuthally symmetric system. By taking the MIGMA problem as an example, the method of determining the constants β,Ω,Z from the average energy, average angular momentum and the total number of particles is illustrated. Associated physical effects are discussed. (author)

  1. Global well-posedness and decay estimates of strong solutions to a two-phase model with magnetic field

    Science.gov (United States)

    Wen, Huanyao; Zhu, Limei

    2018-02-01

    In this paper, we consider the Cauchy problem for a two-phase model with magnetic field in three dimensions. The global existence and uniqueness of strong solution as well as the time decay estimates in H2 (R3) are obtained by introducing a new linearized system with respect to (nγ -n˜γ , n - n ˜ , P - P ˜ , u , H) for constants n ˜ ≥ 0 and P ˜ > 0, and doing some new a priori estimates in Sobolev Spaces to get the uniform upper bound of (n - n ˜ ,nγ -n˜γ) in H2 (R3) norm.

  2. The Double Star magnetic field investigation: instrument design, performance and highlights of the first year's observations

    Directory of Open Access Journals (Sweden)

    C. Carr

    2005-11-01

    Full Text Available One of the primary objectives of the Double Star mission is the accurate measurement of the magnetic field vector along the orbits of the two spacecraft. The magnetic field is an essential parameter for the understanding of space plasma processes and is also required for the effective interpretation of data from the other instruments on the spacecraft. We present the design of the magnetic field instrument onboard both of the Double Star spacecraft and an overview of the performance as measured first on-ground and then in-orbit. We also report the results of in-flight calibration of the magnetometers, and the processing methods employed to produce the final data products which are provided to Double Star investigators, and the wider community in general. Particular attention is paid to the techniques developed for removing magnetic interference generated by the solar arrays on the first (equatorial orbiting spacecraft. Results from the first year of operations are reviewed in the context of combined observations by Double Star and Cluster, and examples given from the different regions visited by the spacecraft to date.

  3. Large magnetization and frustration switching of magnetoresistance in the double-perovskite ferrimagnet Mn2FeReO6.

    Science.gov (United States)

    Arévalo-López, Angel M; McNally, Graham M; Attfield, J Paul

    2015-10-05

    Ferrimagnetic A2 BB'O6 double perovskites, such as Sr2 FeMoO6 , are important spin-polarized conductors. Introducing transition metals at the A-sites offers new possibilities to increase magnetization and tune magnetoresistance. Herein we report a ferrimagnetic double perovskite, Mn2 FeReO6 , synthesized at high pressure which has a high Curie temperature of 520 K and magnetizations of up to 5.0 μB which greatly exceed those for other double perovskite ferrimagnets. A novel switching transition is discovered at 75 K where magnetoresistance changes from conventional negative tunneling behavior to large positive values, up to 265 % at 7 T and 20 K. Neutron diffraction shows that the switch is driven by magnetic frustration from antiferromagnetic Mn(2+) spin ordering which cants Fe(3+) and Re(5+) spins and reduces spin-polarization. Ferrimagnetic double perovskites based on A-site Mn(2+) thus offer new opportunities to enhance magnetization and control magnetoresistance in spintronic materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Strong Transverse Photosphere Magnetic Fields and Twist in Light Bridge Dividing Delta Sunspot of Active Region 12673

    Science.gov (United States)

    Wang, Haimin; Yurchyshyn, Vasyl; Liu, Chang; Ahn, Kwangsu; Toriumi, Shin; Cao, Wenda

    2018-01-01

    Solar Active Region (AR) 12673 is the most flare productive AR in the solar cycle 24. It produced four X-class flares including the X9.3 flare on 06 September 2017 and the X8.2 limb event on 10 September. Sun and Norton (2017) reported that this region had an unusual high rate of flux emergence, while Huang et al. (2018) reported that the X9.3 flare had extremely strong white-light flare emissions. Yang at al. (2017) described the detailed morphological evolution of this AR. In this report, we focus on usual behaviors of the light bridge (LB) dividing the delta configuration of this AR, namely the strong magnetic fields (above 5500 G) in the LB and apparent photospheric twist as shown in observations with a 0.1 arcsec spatial resolution obtained by the 1.6m telescope at Big Bear Solar Observatory.

  5. Strong ion accelerating by collisionless magnetosonic shock wave propagating perpendicular to a magnetic field

    International Nuclear Information System (INIS)

    Ohsawa, Yukiharu.

    1984-12-01

    A 2-1/2 dimensional fully relativistic, fully electromagnetic particle code is used to study a time evolution of nonlinear magnetosonic pulse propagating in the direction perpendicular to a magnetic field. The pulse is excited by an instantaneous piston acceleration, and evolves totally self-consistently. Large amplitude pulse traps some ions and accelerates them parallel to the wave front. They are detrapped when their velocities become of the order of the sum of the ExB drift velocity and the wave phase velocity, where E is the electric field in the direction of wave propagation. The pulse develops into a quasi-shock wave in a collisionless plasma by a dissipation due to the resonant ion acceleration. Simple nonlinear wave theory for a cold plasma well describes the shock properties observed in the simulation except for the effects of resonant ions. In particular, magnitude of an electric potential across the shock region is derived analytically and is found to be in good agreement with our simulations. The potential jump is proportional to B 2 , and hence the ExB drift velocity of the trapped ions is proportional to B. (author)

  6. Faraday effect in rare-earth ferrite garnets located in strong magnetic fields

    International Nuclear Information System (INIS)

    Valiev, U.V.; Zvezdin, A.K.; Krinchik, G.S.; Levitin, R.Z.; Mukimov, K.M.; Popov, A.I.

    1983-01-01

    The Faraday effect is investigated experimentally in single crystal specimens of rare earth iron garnets (REIG) R 3 Fe 5 O 12 (R=Y, Gd, Tb, Dy, Er, Tm, Yb, Eu, Sm and Ho) and also in mixed iron garnets Rsub(x)Ysub(3-x)Fesub(5)Osub(12) (R=Tb, Dy). The m.easurements are carried out in pulsed magnetic fields of intensity up to 200 kOe, in a temperature range from 4.2 to 300 K and at a wavelength of the light lambda=1.15 μm. The field dependence of the Faraday effect observed in the REIG cannot be explained if only the usually considered ''paramagnetic'' contribution to the Faraday effect is taken into account. A theory is developed which, besides the paramagnetic mechanism, takes into account a diamagnetic mechanism and also the mixing of the wave functions of the ground and excited multiplets. The contributions of each of these three mechanisms to the angle of rotation of the plane of polarization by the rare earth sublattice of the iron garnet are estimated theoretically. It is concluded that the mixing mechanism contributes significantly to the field and temperature dependences of the Faraday effect in REIG

  7. Magnetism and local symmetry breaking in a Mott insulator with strong spin orbit interactions.

    Science.gov (United States)

    Lu, L; Song, M; Liu, W; Reyes, A P; Kuhns, P; Lee, H O; Fisher, I R; Mitrović, V F

    2017-02-09

    Study of the combined effects of strong electronic correlations with spin-orbit coupling (SOC) represents a central issue in quantum materials research. Predicting emergent properties represents a huge theoretical problem since the presence of SOC implies that the spin is not a good quantum number. Existing theories propose the emergence of a multitude of exotic quantum phases, distinguishable by either local point symmetry breaking or local spin expectation values, even in materials with simple cubic crystal structure such as Ba 2 NaOsO 6 . Experimental tests of these theories by local probes are highly sought for. Our local measurements designed to concurrently probe spin and orbital/lattice degrees of freedom of Ba 2 NaOsO 6 provide such tests. Here we show that a canted ferromagnetic phase which is preceded by local point symmetry breaking is stabilized at low temperatures, as predicted by quantum theories involving multipolar spin interactions.

  8. MRI-related static magnetic stray fields and postural body sway: a double-blind randomized crossover study.

    Science.gov (United States)

    van Nierop, Lotte E; Slottje, Pauline; Kingma, Herman; Kromhout, Hans

    2013-07-01

    We assessed postural body sway performance after exposure to movement induced time-varying magnetic fields in the static magnetic stray field in front of a 7 Tesla (T) magnetic resonance imaging scanner. Using a double blind randomized crossover design, 30 healthy volunteers performed two balance tasks (i.e., standing with eyes closed and feet in parallel and then in tandem position) after standardized head movements in a sham, low exposure (on average 0.24 T static magnetic stray field and 0.49 T·s(-1) time-varying magnetic field) and high exposure condition (0.37 T and 0.70 T·s(-1)). Personal exposure to static magnetic stray fields and time-varying magnetic fields was measured with a personal dosimeter. Postural body sway was expressed in sway path, area, and velocity. Mixed-effects model regression analysis showed that postural body sway in the parallel task was negatively affected (P < 0.05) by exposure on all three measures. The tandem task revealed the same trend, but did not reach statistical significance. Further studies are needed to investigate the possibility of independent or synergetic effects of static magnetic stray field and time-varying magnetic field exposure. In addition, practical safety implications of these findings, e.g., for surgeons and others working near magnetic resonance imaging scanners need to be investigated. Copyright © 2012 Wiley Periodicals, Inc.

  9. Investigating the efficacy of magnetic nanofluid as a coolant in double-pipe heat exchanger in the presence of magnetic field

    International Nuclear Information System (INIS)

    Bahiraei, Mehdi; Hangi, Morteza

    2013-01-01

    Highlights: • Efficacy of magnetic nanofluid as coolant was studied in double-pipe heat exchanger. • Effect of applying quadrupole magnetic field with different magnitudes was analyzed. • Magnetic force makes the concentration distribution more uniform in tube side. • Applying magnetic field enhances both pressure drop and heat transfer. • Optimization was performed to reach maximum heat transfer and minimum pressure drop. - Abstract: The current study attempts to investigate the performance of water based Mn–Zn ferrite magnetic nanofluid in a counter-flow double-pipe heat exchanger under quadrupole magnetic field using the two-phase Euler–Lagrange method. The nanofluid flows in the tube side as coolant, while the hot water flows in the annulus side. The effects of different parameters including concentration, size of the particles, magnitude of the magnetic field and Reynolds number are examined. Distribution of the particles is non-uniform at the cross section of the tube such that the concentration is higher at central regions of the tube. Application of the magnetic field makes the distribution of particles more uniform and this uniformity increases by increasing the distance from the tube inlet. Increasing each of the parameters of concentration, particle size and magnitude of the magnetic field will lead to a greater pressure drop and also higher heat transfer improvement. At higher Reynolds numbers, the effect of magnetic force is diminished. Optimization was performed using genetic algorithm coupled with compromise programming technique in order to reach the maximum overall heat transfer coefficient along with the minimum pressure drop. For this purpose, the models of objective functions of overall heat transfer coefficient and pressure drop of the nanofluid were first extracted in terms of the effective parameters using neural network. The neural network model predicts the output variables with a very good accuracy. The optimal values were

  10. Comparative studies of density-functional approximations for light atoms in strong magnetic fields

    Science.gov (United States)

    Zhu, Wuming; Zhang, Liang; Trickey, S. B.

    2014-08-01

    For a wide range of magnetic fields, 0≤B≤2000 a.u., we present a systematic comparative study of the performance of different types of density-functional approximations in light atoms (2≤Z≤6). Local, generalized-gradient approximation (GGA; semilocal), and meta-GGA ground-state exchange-correlation (xc) functionals are compared on an equal footing with exact-exchange, Hartree-Fock (HF), and current-density-functional-theory (CDFT) approximations. Comparison also is made with published quantum Monte Carlo data. Though all approximations give qualitatively reasonable results, the exchange energies from local and GGA functionals are too negative for large B. Results from the Perdew-Burke-Ernzerhof ground-state GGA and Tao-Perdew-Staroverov-Scuseria (TPSS) ground-state meta-GGA functionals are very close. Because of confinement, self-interaction error in such functionals is more severe at large B than at B =0, hence self-interaction correction is crucial. Exact exchange combined with the TPSS correlation functional results in a self-interaction-free (xc) functional, from which we obtain atomic energies of comparable accuracy to those from correlated wave-function methods. Specifically for the B and C atoms, we provide beyond-HF energies in a wide range of B fields. Fully self-consistent CDFT calculations were done with the Vignale-Rasolt-Geldart (VRG) functional in conjunction with the PW92 xc functional. Current effects turn out to be small, and the vorticity variable in the VRG functional diverges in some low-density regions. This part of the study suggests that nonlocal, self-interaction-free functionals may be better than local approximations as a starting point for CDFT functional construction and that some basic variable other than the vorticity could be helpful in making CDFT calculations practical.

  11. Strong perpendicular magnetic anisotropy at FeCoB/MgO interface with an ultrathin HfOx insertion layer

    Science.gov (United States)

    Ou, Yongxi; Ralph, Daniel; Buhrman, Robert

    The realization of robust perpendicular magnetic anisotropy (PMA) in heavy metal(HM)/FeCoB/MgO thin-film heterostructures has enabled a pathway for the implementation of high density memory elements based on perpendicularly magnetized tunnel junctions, and also provides a platform for the study and control of domain walls and of novel magnetic chiral structures such as skyrmions in nanowire structures. Here we report on the achievement of more robust PMA in Ta/FeCoB/MgO heterostructures by the insertion of an ultrathin HfOx passivation layer at the FeCoB/MgO interface. This is accomplished by depositing one to two atomic layers of Hf onto the FeCoB before the subsequent rf sputter deposition of the MgO layer, which fully oxidizes the Hf layer as confirmed by X-ray photoelectron spectroscopy measurements. The result is a strong interfacial perpendicular anisotropy energy density as large as 1.7 erg/cm-2 without any post-fabrication annealing treatment. Similar results have been achieved with the use of W and Pt HM base layers. This work broadens the class and enhances the capabilities of PMA HM/FM heterostructures for spintronics research and applications.

  12. A device to measure the effects of strong magnetic fields on the image resolution of PET scanners

    CERN Document Server

    Burdette, D; Chesi, E; Clinthorne, N H; Cochran, E; Honscheid, K; Huh, S S; Kagan, H; Knopp, M; Lacasta, C; Mikuz, M; Schmalbrock, P; Studen, A; Weilhammer, P

    2009-01-01

    Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. As these systems approach sub-millimeter resolutions, the range of the positron is becoming the dominant contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as and , which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally, we developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper, we describe the instrument and present initial results of a study of the effects of magnetic fields up to 7 T on PET image resolution for and point sources.

  13. Performance and analysis of wireless power charging system from room temperature to HTS magnet via strong resonance coupling method

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Y. D.; Lee, S. Y.; Lee, T. W.; Kim, J. S. [Suwon Science College, Suwon (Korea, Republic of); Lee, C. Y. [Korea Railroad Institute, Uiwang (Korea, Republic of)

    2016-03-15

    The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.

  14. SN 2011A: A Low-luminosity Interacting Transient with a Double Plateau and Strong Sodium Absorption

    Science.gov (United States)

    de Jaeger, T.; Anderson, J. P.; Pignata, G.; Hamuy, M.; Kankare, E.; Stritzinger, M. D.; Benetti, S.; Bufano, F.; Elias-Rosa, N.; Folatelli, G.; Förster, F.; González-Gaitán, S.; Gutiérrez, C. P.; Inserra, C.; Kotak, R.; Lira, P.; Morrell, N.; Taddia, F.; Tomasella, L.

    2015-07-01

    We present optical photometry and spectroscopy of the optical transient SN 2011A. Our data span 140 days after discovery including {BVRI} u\\prime g\\prime r\\prime i\\prime z\\prime photometry and 11 epochs of optical spectroscopy. Originally classified as a type IIn supernova (SN IIn) due to the presence of narrow Hα emission, this object shows exceptional characteristics. First, the light curve shows a double plateau, a property only observed before in the impostor SN 1997bs. Second, SN 2011A has a very low luminosity ({M}V=-15.72), placing it between normal luminous SNe IIn and SN impostors. Third, SN 2011A shows low velocity and high equivalent width absorption close to the sodium doublet, which increases with time and is most likely of circumstellar origin. This evolution is also accompanied by a change in line profile; when the absorption becomes stronger, a P Cygni profile appears. We discuss SN 2011A in the context of interacting SNe IIn and SN impostors, which appears to confirm the uniqueness of this transient. While we favor an impostor origin for SN 2011A, we highlight the difficulty in differentiating between terminal and non-terminal interacting transients. This paper includes data obtained with the 6.5 m Magellan Telescopes and du Pont telescope; the Gemini-North Telescope, Mauna Kea, USA (Gemini Program GN-2010B-Q67, PI: Stritzinger); the PROMPT telescopes at Cerro Tololo Inter-American Observatory in Chile; with the Liverpool Telescope operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council; based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofisica de Canarias; the NTT from ESO Science Archive

  15. Test of Horizontal Magnetic Field Measurements in the Presence of a Strong Vertical Field

    CERN Document Server

    Vasserman, Isaac

    2004-01-01

    Trajectory straightness is an important parameter defining the performance of free-electron laser (FEL) devices. The first test of horizontal field measurements using Hall probes was done in 1998 as a preparation to the tuning of undulators for the FEL project at the Advanced Photon Source. This work continues the 1998 work, now associated with Linac Coherent Light Source (LCLS) project. Tolerances for the LCLS FEL undulator specify 2 um trajectory excursion in both (horizontal and vertical) planes for a particle energy of 14.1 GeV, which means that measurements of a small horizontal field in presence of strong (up to 1.5 T) vertical field are required. Hall probe measurements under such conditions are complicated due to a planar Hall probe effect. Previous tests done in 1998 showed that a 2- axis Sentron probe is a possible choice. The high sensitivity of horizontal field integrals to the vertical position of the sensor was observed. It was shown that this probe could be used for fast measurements and tuning...

  16. Effects of a strong magnetic field on internal gravity waves: trapping, phase mixing, reflection and dynamical chaos

    Science.gov (United States)

    Loi, Shyeh Tjing; Papaloizou, John C. B.

    2018-04-01

    The spectrum of oscillation modes of a star provides information not only about its material properties (e.g. mean density), but also its symmetries. Spherical symmetry can be broken by rotation and/or magnetic fields. It has been postulated that strong magnetic fields in the cores of some red giants are responsible for their anomalously weak dipole mode amplitudes (the "dipole dichotomy" problem), but a detailed understanding of how gravity waves interact with strong fields is thus far lacking. In this work, we attack the problem through a variety of analytical and numerical techniques, applied to a localised region centred on a null line of a confined axisymmetric magnetic field which is approximated as being cylindrically symmetric. We uncover a rich variety of phenomena that manifest when the field strength exceeds a critical value, beyond which the symmetry is drastically broken by the Lorentz force. When this threshold is reached, the spatial structure of the g-modes becomes heavily altered. The dynamics of wave packet propagation transitions from regular to chaotic, which is expected to fundamentally change the organisation of the mode spectrum. In addition, depending on their frequency and the orientation of field lines with respect to the stratification, waves impinging on different parts of the magnetised region are found to undergo either reflection or trapping. Trapping regions provide an avenue for energy loss through Alfvén wave phase mixing. Our results may find application in various astrophysical contexts, including the dipole dichotomy problem, the solar interior, and compact star oscillations.

  17. Structural, magnetic and electrical characterization of Cd-substituted Mg ferrites synthesized by double sintering technique

    Energy Technology Data Exchange (ETDEWEB)

    Zahir, R. [Department of Physics, Chittagong University of Engineering and Technology, Chittagong 4349 (Bangladesh); Chowdhury, F.-U.Z, E-mail: faruque@cuet.ac.bd [Department of Physics, Chittagong University of Engineering and Technology, Chittagong 4349 (Bangladesh); Uddin, M.M. [Department of Physics, Chittagong University of Engineering and Technology, Chittagong 4349 (Bangladesh); Hakim, M.A. [Materials Science Division, Atomic Energy Center, Dhaka 1000 (Bangladesh)

    2016-07-15

    Cd-substituted Mg ferrites with compositional formula Mg{sub 1−x}Cd{sub x}Fe{sub 2}O{sub 4} with 0.1≤x≤0.6 in the steps of 0.1 have been synthesized by double sintering ceramic technique. The X-ray diffraction analysis has revealed that the samples crystallize in a single phase cubic spinel structure. The lattice parameter has increased with increasing Cd content in conformity with Vegard's law. The study of scanning electron microscopy has revealed that Cd substitution has increased the particle size of the ferrites increases from ~2.2 to 9.2 µm. Some probable interpretations based on literature have been discussed. The increase in particle size with increasing of Cd content has consequently resulted in the initial permeability. The Curie temperature has decreased linearly with increasing Cd content which pointed out the weakening of A-B exchange interaction. The spectra of quality factor have showed a steady bandwidth of 0.1–8 MHz, this finding makes the ferrite system suitable for broadband pulse transformer. The variation of electrical resistivity (DC and AC) has been explained on the basis of electron hopping between Fe{sup 2+}and Fe{sup 3+}. - Highlights: • Synthesis of Cd-substituted Mg ferrites by double sintering ceramic technique. • Studies of Cd substitution on the structural and magnetic properties of Mg Ferrites. • The Curie temperature decreases linearly with increasing Cd concentration. • Due to the conduction of hopping of charge carriers DC resistivity decreases.

  18. Double disordered YBCO coated conductors of industrial scale: high currents in high magnetic field

    International Nuclear Information System (INIS)

    Abraimov, D; Francis, A; Jaroszynski, J; McCallister, J; Polyanskii, A; Santos, M; Viouchkov, Y L; Ballarino, A; Bottura, L; Rossi, L; Barth, C; Senatore, C; Dietrich, R; Rutt, A; Schlenga, K; Usoskin, A; Majkic, G S; Selvamanickam, V

    2015-01-01

    A significant increase of critical current in high magnetic field, up to 31 T, was recorded in long tapes manufactured by employing a double-disorder route. In a double-disordered high-temperature superconductor (HTS), a superimposing of intrinsic and extrinsic disorder takes place in a way that (i) the intrinsic disorder is caused by local stoichiometry deviations that lead to defects of crystallinity that serve as pining centers in the YBa 2 Cu 3 O x−δ matrix and (ii) the extrinsic disorder is introduced via embedded atoms or particles of foreign material (e.g. barium zirconate), which create a set of lattice defects. We analyzed possible technological reasons for this current gain. The properties of these tapes over a wider field-temperature range as well as field anisotropy were also studied. Record values of critical current as high as 309 A at 31 T, 500 A at 18 Tm and 1200 A at 5 T were found in 4 mm wide tape at 4.2 K and B perpendicular to tape surface. HTS layers were processed in medium-scale equipment that allows a maximum batch length of 250 m while 22 m long batches were provided for investigation. Abnormally high ratios (up to 10) of critical current density measured at 4.2 K, 19 T to critical current density measured at 77 K, self-field were observed in tapes with the highest in-field critical current. Anisotropy of the critical current as well as angular dependences of n and α values were investigated. The temperature dependence of critical current is presented for temperatures between 4.2 and 40 K. Prospects for the suppression of the dog-bone effect by Cu plating and upscale of processing chain to >500 m piece length are discussed. (paper)

  19. The itinerant magnetism in a 3d-4d double perovskite Sr2CrMoO6

    Science.gov (United States)

    Dimitri Ngantso, G.; Boujnah, M.; Benyoussef, A.; El Kenz, A.

    2017-12-01

    In this work, we use the exact diagonalization and Monte Carlo calculations to study magnetic behaviors of the 3d-4d double perovskite Sr2CrMoO6. The model is described by a quantum Hamiltonian induced by the hybridization mechanism in Sr2CrMoO6 via the double exchange, considering the transition metal Mo5+ (σ = 1/2, 4d1) cation totally non-magnetic and classical core spins S = 3/2 located at sites of Cr3+ (S = 3/2, 3d3) cations. We have defined a Hamiltonian matrix and determined eigen-energies which are functions of core spins interactions. At ground state, we have found that the ferromagnetic phase of core spins stabilizes the system for the electronic density n = 0.25. To study magnetic properties at finite temperature, we have defined an effective magnetic Hamiltonian for spins, approving the Monte Carlo simulations for systems of high sizes. Thus, the exchange coupling effect, the magnetization and the magnetic susceptibility are investigated for different sizes, and the critical temperature is determined.

  20. Effect of interdiffusion and external magnetic field on electronic states and light absorption in Gaussian-shaped double quantum ring

    Science.gov (United States)

    Aziz-Aghchegala, V. L.; Mughnetsyan, V. N.; Kirakosyan, A. A.

    2018-02-01

    The effect of interdiffusion and magnetic field on confined states of electron and heavy hole as well as on interband absorption spectrum in a Ga1-xAlxAs/GaAs Gaussian-shaped double quantum ring are investigated. It is shown that both interdiffusion and magnetic field lead to the change of the charge carriers' quantum states arrangement by their energies. The oscillating behavior of the electron ground state energy as a function of magnetic field induction gradually disappears with the increase of diffusion parameter due to the enhanced tunneling of electron to the central region of the ring. For the heavy hole the ground state energy oscillations are not observable in the region of the values of magnetic field induction B = 0 - 10 T . For considered transitions both the magnetic field and the interdiffusion lead to a blue-shift of the absorption spectrum and to decreasing of the absorption intensity. The obtained results indicate on the opportunity of purposeful manipulation of energy states and absorption spectrum of a Gaussian-shaped double quantum ring by means of the post growth annealing and the external magnetic field.

  1. Anomalously strong relaxation of the polarization of muons in the magnetically ordered and paramagnetic states of the TbMnO3 multiferroic

    Science.gov (United States)

    Andrievskii, D. S.; Vorob'ev, S. I.; Getalov, A. L.; Golovenchits, E. I.; Komarov, E. N.; Kotov, S. A.; Sanina, V. A.; Shcherbakov, G. V.

    2017-09-01

    An anomalously strong relaxation of the muon polarization in a magnetically ordered state in the TbMnO3 multiferroic has been revealed by the method below the μ SR Néel temperature (42 K). Such a relaxation is due to the muon channel of relaxation of the polarization and the interaction of the magnetic moment of the muon with inhomogeneities of the internal magnetic field of an ordered state in the form of a cycloid. Above the Néel temperature, beginning with temperatures depending on the applied magnetic field, a two-phase state has been revealed where one phase has an anomalously strong relaxation of the muon polarization for a paramagnetic state. These features of the paramagnetic state are due to short-range magnetic order domains that appear in strongly frustrated TbMnO3. A true paramagnetic state has been observed only at T ≥ 150 K.

  2. Magnetic resonance therapy for knee osteoarthritis: a randomized, double blind placebo controlled trial.

    Science.gov (United States)

    Gökşen, Nurgül; Çaliş, Mustafa; Doğan, Serap; Çaliş, Havva T; Özgöçmen, Salih

    2016-08-01

    Therapeutic nuclear magnetic resonance therapy (MRT) works based on the electromagnetic fields. To investigate efficacy of MRT in knee osteoarthritis (OA). Prospective, randomized, double-blind, placebo controlled trial. Outpatient clinic, university hospital. Patients who had mild to moderate knee OA at a single knee joint and between 30-75-years-old were randomized by blinded chip cards (1:1). The treatment group received ten sessions of one hour daily MRT, controls received placebo MRT. All patients underwent clinical examination at baseline, after 2 weeks, and 12 weeks. Imaging included blindly assessed ultrasonography and magnetic resonance (MR) of the knee. Ninety-seven patients completed the study. Both groups improved significantly but the average change from baseline in outcome parameters was similar in MRT group (on VAS-pain,-2.6; WOMAC-pain, -2.09; WOMAC-stiffness, -1.81; WOMAC-physical, -1.96) compared to placebo after two weeks (VAS-pain,-1.6; WOMAC-pain, -1.91; WOMAC-stiffness, -1.27; WOMAC-physical, -1.54). Also changes were quite similar at the 12th week after the treatment. SF-36 components at 12th week improved but changes were not significant. Imaging arm also failed to show significant differences between groups in terms of cartilage thickness on US and MR scores. No adverse events were recorded. MRT is safe, but not superior to placebo in terms of improvement in clinical or imaging parameters after a 10-day course of treatment in mild to moderate knee OA. The present study does not promote use of a 10-day course of MRT in mild to moderate knee OA.

  3. Design and status of the 250 T - bending magnets for the 15 GeV Harmonic Double Sided Microtron for MAMI

    CERN Document Server

    Thomas, A; Kaiser, K H; Kreidel, H J; Ludwig-Mertin, U; Seidel, M

    2002-01-01

    The recirculating system of the Harmonic Double Sided Microtron (HDSM) for MAMI (Mainz Microtron) consists of four large bending magnets, which act like 90 degrees - mirrors for all beams. For the compensation of the strong vertical defocusing resulting from the -45deg. pole face rotation a special pole profile was chosen, leading to the appropriate field decay normal to the straight front edge. The machining procedure for a high quality and precise surface of the partly concave poles was worked out in collaboration with the manufacturer. 3D-codes (TOSCA and IDEAS) were used to optimise both magnetic and mechanical properties of the magnets. As a result, it was decided to build the iron core essentially only from two 125t-pieces made of high permeable cast iron. The coils were designed for a minimum temperature increase at a given power consumption and for high reliability by avoiding internal tube brazing. The first of the four magnets has been delivered end of 2001 and was transported through narrow buildin...

  4. MFM study of magnetic interaction between recording and soft magnetic layers

    International Nuclear Information System (INIS)

    Honda, Yukio; Tanahashi, Kiwamu; Hirayama, Yoshiyuki; Kikukawa, Atsushi; Futamoto, Masaaki

    2001-01-01

    Magnetic force microscopy was used to study the magnetic interaction between the recording and the soft magnetic layers in double-layer perpendicular media by observing the magnetization structure from the soft magnetic layer side. There was a strong magnetic interaction between the recording and the soft magnetic layers. Introducing a thin nonmagnetic intermediate layer between the two layers greatly reduced the magnetic interaction and drastically reduced the medium noise

  5. High-latitude dayside electric fields and currents during strong northward interplanetary magnetic field: Observations and model simulation

    International Nuclear Information System (INIS)

    Clauer, C.R.; Friis-Christensen, E.

    1988-01-01

    On July 23, 1983, the Interplanetary Magnetic Field turned strongly northward, becoming about 22 nT for several hours. Using a combined data set of ionospheric convection measurements made by the Sondre Stromfjord incoherent scatter radar and convection inferred from Greenland magnetometer measurements, we observe the onset of the reconfiguration of the high-latitude ionospheric currents to occur about 3 min following the northward IMF encountering the magnetopause. The large-scale reconfiguration of currents, however, appears to evolve over a period of about 22 min. Using a computer model in which the distribution of field-aligned current in the polar cleft is directly determined by the strength and orientation of the interplanetary electric field, we are able to simulate the time-varying pattern of ionospheric convection, including the onset of high-latitude ''reversed convection'' cells observed to form during the interval of strong northward IMF. These observations and the simulation results indicate that the dayside polar cap electric field observed during strong northward IMF is produced by a direct electrical current coupling with the solar wind. copyright American Geophysical Union 1988

  6. Structural, magnetic and electrical properties of a new double-perovskite LaNaMnMoO6 material.

    Science.gov (United States)

    Borchani, Sameh Megdiche; Koubaa, Wissem Cheikh-Rouhou; Megdiche, Makrem

    2017-11-01

    Structural, magnetic, magnetocaloric, electrical and magnetoresistance properties of an LaNaMnMoO 6 powder sample have been investigated by X-ray diffraction (XRD), magnetic and electrical measurements. Our sample has been synthesized using the ceramic method. Rietveld refinements of the XRD patterns show that our sample is single phase and it crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature in a magnetic applied field of 0.05 T shows that our sample exhibits a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature T C is found to be 320 K. Arrott plots show that all our double-perovskite oxides exhibit a second-order magnetic phase transition. From the measured magnetization data of an LaNaMnMoO 6 sample as a function of the magnetic applied field, the associated magnetic entropy change |-ΔSM| and the relative cooling power (RCP) have been determined. In the vicinity of T C , |-ΔSM| reached, in a magnetic applied field of 8 T, a maximum value of ∼4 J kg -1  K -1 . Our sample undergoes a large magnetocaloric effect at near-room temperature. Resistivity measurements reveal the presence of an insulating-metal transition at Tρ = 180 K. A magnetoresistance of 30% has been observed at room temperature for 6 T, significantly larger than that reported for the A 2 FeMoO 6 (A = Sr, Ba) double-perovskite system.

  7. High-pressure synthesis, crystal structure and magnetic properties of double perovskite oxide Ba2CuOsO6

    International Nuclear Information System (INIS)

    Feng, Hai L.; Arai, Masao; Matsushita, Yoshitaka; Tsujimoto, Yoshihiro; Yuan, Yahua; Sathish, Clastin I.; He, Jianfeng; Tanaka, Masahiko; Yamaura, Kazunari

    2014-01-01

    A new compositional double perovskite oxide Ba 2 CuOsO 6 was synthesized under high-pressure (6 GPa) and high-temperature (1500 °C) conditions. The polycrystalline Ba 2 CuOsO 6 was characterized by synchrotron X-ray diffraction, thermogravimetric analysis, and magnetic susceptibility, isothermal magnetization, and specific heat measurements. The oxide crystallizes in a double-perovskite structure with an I4/m space group, in which Os(VI) and Cu(II) are ordered in the perovskite B-site. Ba 2 CuOsO 6 is electrically insulating with an activation energy of 0.813(2) eV and shows antiferromagnetic-like characteristics at temperatures of ∼55 K and ∼70 K. The results of the first-principle calculation suggested that the spin–orbit interaction of Os(VI) plays a substantial role in the insulating state. The Jahn–Teller distortion of CuO 6 octahedra influences the magnetic characteristics with regard to possible two-dimensional magnetic correlations. - Graphical abstract: A new compositional double perovskite oxide Ba 2 CuOsO 6 synthesized by a high-pressure (6 GPa) and high-temperature (1500 °C) method. - Highlights: • A new compositional double perovskite oxide Ba 2 CuOsO 6 was synthesized. • Ba 2 CuOsO 6 is electrically insulating and antiferromagnetic below ∼70 K. • The Jahn–Teller distortion of CuO 6 has relevance to possible magnetic anisotropy

  8. Evaluation of colonic involvement in endometriosis: double-contrast barium enema vs. magnetic resonance imaging.

    Science.gov (United States)

    Faccioli, N; Foti, G; Manfredi, R; Mainardi, P; Spoto, E; Ruffo, G; Minelli, L; Mucelli, R Pozzi

    2010-08-01

    The purpose of the study was to compare the accuracy of double-contrast barium enema (DCBE) and magnetic resonance imaging (MRI) in the diagnosis of intestinal endometriosis using the histological examination on resected specimen as comparative standard. Eighty-three consecutive patients with suspected intestinal endometriosis, resected between 2005 and 2007, were prospectively evaluated. All of the women underwent preoperative DCBE and MRI on the same day. We evaluated number, site (rectum, sigmoid, cecum), and size of the lesions. The imaging findings were correlated with those resulting at pathology. Among the 65 women who underwent surgery, 50/65 (76.9%) were found to have bowel endometriosis, with 9/50 (18%) patients presenting two lesions; DCBE allowed to detect 50/59 (84.7%) lesions. MRI allowed to detect 42/59 (71.1%) lesions. DCBE showed sensibility, specificity, PPV, NPV, and accuracy of respectively 84.7, 93.7, 98.0, 62.5, and 86.6%, MRI of 71.1, 83.3, 93.3, 46.8, and 74.6%. DCBE is more accurate than unenhanced MRI in the diagnosis of bowel endometriosis, and should be preferred in the preoperative management of this disease, since it usually enables a proper surgical planning.

  9. Fabrication and magnetic properties of electrodeposited Ni/Cu nanowires using the double bath method

    International Nuclear Information System (INIS)

    Maleak, N.; Potpattanapol, P.; Bao, N.N.; Ding, J.; Wongkokuo, W.; Tang, I.M.; Thongmee, S.

    2014-01-01

    Ordered Ni/Cu multilayered nanowires (NW's) were fabricated using the two bath method in which the AAO template was switched back and forth between the two baths each containing solutions of dissolved Ni and Cu sulfates repeatedly. Different combinations of periods in which templates spent in each bath were used. The SEM and TEM images of the NW's showed that the NW's were smooth and uniform. The VSM results showed that in the presence of a field applied parallel to the NW, the coercivity and squareness increased when the deposition times of the Ni and Cu increased. To account for the behavior when both the thicknesses of the Ni and Cu layers were increasing, the effects of the increase in the Cu layer partially offset the effects of the increase in the Ni layer. The highest coercivity and squareness achieved was 822 Oe and 0.949, respectively, when the deposition times were 8 min for the Ni deposition and 2.5 min for the Cu deposition. - Highlights: • The double bath method produced nanowires having alternating layers of Ni and Cu. • The coercivities and squareness were higher for magnetic fields applied parallel to the wire's axis. • Coercivities of the nanowires increased from 365 Oe to 822 Oe as the Ni deposition time increased. • Squareness increased from 0.800 to 0.949 as the Ni deposition times increased

  10. Repetitive transcranial magnetic stimulation for rehabilitation of poststroke dysphagia: A randomized, double-blind clinical trial.

    Science.gov (United States)

    Du, Juan; Yang, Fang; Liu, Ling; Hu, Jingze; Cai, Biyang; Liu, Wenhua; Xu, Gelin; Liu, Xinfeng

    2016-03-01

    This randomized, sham-controlled, double-blind study was conducted to investigate the effects of high-frequency versus low-frequency repetitive transcranial magnetic stimulation (rTMS) on patients with poststroke dysphagia during early rehabilitation. Forty patients with poststroke dysphagia were randomized to receive five daily sessions of sham, 3-Hz ipsilesional, or 1-Hz contralesional rTMS. Swallowing function, the severity of stroke and functional disability, and cortical excitability were examined before, immediately after five daily sessions, as well as the first, second, and third month after the last session. At baseline, no significant differences between groups were observed in terms of demographic and clinical rating scales. However, a significantly greater improvement in swallowing function as well as functional disability was observed after real rTMS when compared with sham rTMS, which remained 3 months after the end of the treatment sessions. In addition, 1-Hz rTMS increased cortical excitability of the affected hemisphere and decreased that of the non-affected hemisphere; however, 3-Hz rTMS only increased cortical excitability of the affected hemisphere. rTMS (both high and low frequency) improved swallowing recovery in patients with poststroke dysphagia, and the effects lasted for at least 3 months. rTMS appears to be a beneficial therapeutic modality for patients with dysphagia during the early phase of stroke. Copyright © 2015 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  11. Ferromagnetic interactions in new double end-on-azide-bridged dinuclear Ni(II) complex: Synthesis, crystal structures, magnetic and photoluminescence properties

    Science.gov (United States)

    Donmez, Adem; Oylumluoglu, Gorkem; Coban, M. Burak; Kocak, Cagdas; Aygun, Muhittin; Kara, Hulya

    2017-12-01

    A new double end-on azide-bridged dinuclear nickel(II) Schiff base complex, [Ni2(μ1,1-N3)2(HL)2(MeOH)2], [HL = 2-[(2-hydroxypropylimino)methyl)-3,5-chlorophenol] has been synthesized and characterized by elemental analysis, UV and IR spectroscopy, single crystal X-ray diffraction, magnetic and photoluminescence study. The asymmetric unit contains half of the dinuclear unit. The Ni(HL) units in each dinuclear molecule are connected to each other by two bridging end-on azide ligands. In the crystalline architecture of the Ni(II) complex, intermolecular Osbnd H⋯N hydrogen bonds link the molecules which form one-dimensional structure. Additionally, low temperature magnetic measurements indicate a dominant intradimer ferromagnetic interactions in double end-on azide-bridged dinuclear Ni(II) complex. Room temperature solid state photoluminescence measurements of Ni(II) complex show strong green emission band at λmax = 508 nm while its free ligand H2L shows broad yellow emission band at λmax = 594 nm. The luminescent performances making Ni(II) complex may be good candidates for potential luminescence materials.

  12. Double-layered perpendicular magnetic recording media of granular-type FePt-MgO films

    International Nuclear Information System (INIS)

    Zhang Zhengang; Singh, Amarendra K.; Yin Jinhua; Perumal, A.; Suzuki, Takao

    2005-01-01

    The recording performance of double-layered granular-type FePt-MgO perpendicular magnetic recording media fabricated onto glass discs by sputtering is investigated. The (0 0 1)-textured FePt granular films are obtained by annealing FePt/MgO multilayers. Three different multilayer structures are compared in their magnetic properties and recording SNR performances. To evaluate thermal stability property of these granular-type FePt disks, the time-dependent magnetic force microscope (MFM) signal from the written bits on one of these disks is recorded in the temperature range 25-200 degree sign C. The signal decay at high observation temperature is interpreted based on the temperature dependence of magnetic anisotropy (K u )

  13. Phase manipulation of Goos–Hänchen shifts in a single-layer of graphene nanostructure under strong magnetic field

    Science.gov (United States)

    Solookinejad, Gh; Jabbari, M.; Panahi, M.; Ahmadi Sangachin, E.

    2017-11-01

    In this paper, we discuss the phase management of Goos–Hänchen (GH) shifts of a probe light through a cavity with a single-layer graphene nanostructure under a strong magnetic field. By using the quantum mechanical density matrix formalism we study the GH shifts of reflected and transmitted light beams. It is realized that negative or positive GH shifts can be achieved simultaneously by tuning some controllable parameters such as relative phase and the Rabi frequency of the applied fields. Moreover, the thickness effect of the cavity structure is considered as an effective parameter for adjusting the GH shifts of reflected and transmitted light beams. We find that by choosing suitable parameters, a maximum negative shift of 4.5 mm and positive shift of 5.4 mm are possible for GH shifts in reflected and transmitted light. Our proposed model may be useful for developing all-optical devices in the infrared region.

  14. THE POST-MERGER MAGNETIZED EVOLUTION OF WHITE DWARF BINARIES: THE DOUBLE-DEGENERATE CHANNEL OF SUB-CHANDRASEKHAR TYPE Ia SUPERNOVAE AND THE FORMATION OF MAGNETIZED WHITE DWARFS

    International Nuclear Information System (INIS)

    Ji Suoqing; Fisher, Robert T.; García-Berro, Enrique; Tzeferacos, Petros; Jordan, George; Lee, Dongwook; Lorén-Aguilar, Pablo; Cremer, Pascal; Behrends, Jan

    2013-01-01

    Type Ia supernovae (SNe Ia) play a crucial role as standardizable cosmological candles, though the nature of their progenitors is a subject of active investigation. Recent observational and theoretical work has pointed to merging white dwarf binaries, referred to as the double-degenerate channel, as the possible progenitor systems for some SNe Ia. Additionally, recent theoretical work suggests that mergers which fail to detonate may produce magnetized, rapidly rotating white dwarfs. In this paper, we present the first multidimensional simulations of the post-merger evolution of white dwarf binaries to include the effect of the magnetic field. In these systems, the two white dwarfs complete a final merger on a dynamical timescale, and are tidally disrupted, producing a rapidly rotating white dwarf merger surrounded by a hot corona and a thick, differentially rotating disk. The disk is strongly susceptible to the magnetorotational instability (MRI), and we demonstrate that this leads to the rapid growth of an initially dynamically weak magnetic field in the disk, the spin-down of the white dwarf merger, and to the subsequent central ignition of the white dwarf merger. Additionally, these magnetized models exhibit new features not present in prior hydrodynamic studies of white dwarf mergers, including the development of MRI turbulence in the hot disk, magnetized outflows carrying a significant fraction of the disk mass, and the magnetization of the white dwarf merger to field strengths ∼2 × 10 8 G. We discuss the impact of our findings on the origins, circumstellar media, and observed properties of SNe Ia and magnetized white dwarfs

  15. Fibrous polymer grafted magnetic chitosan beads with strong poly(cation-exchange) groups for single step purification of lysozyme.

    Science.gov (United States)

    Bayramoglu, Gulay; Tekinay, Turgay; Ozalp, V Cengiz; Arica, M Yakup

    2015-05-15

    Lysozyme is an important polypetide used in medical and food applications. We report a novel magnetic strong cation exchange beads for efficient purification of lysozyme from chicken egg white. Magnetic chitosan (MCHT) beads were synthesized via phase inversion method, and then grafted with poly(glycidyl methacrylate) (p(GMA)) via the surface-initiated atom transfer radical polymerization (SI-ATRP). Epoxy groups of the grafted polymer, were modified into strong cation-exchange groups (i.e., sulfonate groups) in the presence of sodium sulfite. The MCTH and MCTH-g-p(GMA)-SO3H beads were characterized by ATR-FTIR, SEM, and VSM. The sulphonate groups content of the modified MCTH-g-p(GMA)-4 beads was found to be 0.53mmolg(-1) of beads by the potentiometric titration method. The MCTH-g-p(GMA)-SO3H beads were first used as an ion-exchange support for adsorption of lysozyme from aqueous solution. The influence of different experimental parameters such as pH, contact time, and temperature on the adsorption process was evaluated. The maximum adsorption capacity was found to be 208.7mgg(-1) beads. Adsorption of lysozyme on the MCTH-g-p(GMA)-SO3H beads fitted to Langmuir isotherm model and followed the pseudo second-order kinetic. More than 93% of the adsorbed lysozyme was desorbed using Na2CO3 solution (pH 11.0). The purity of the lysozyme was checked by HPLC and SDS gel electrophoresis. In addition, the MCTH-g-p(GMA)-SO3H beads prepared in this work showed promising potential for separation of various anionic molecules. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. He 2++ molecular ion in a strong time-dependent magnetic field: a current-density functional study.

    Science.gov (United States)

    Vikas

    2011-08-01

    The He 2++ molecular ion exposed to a strong ultrashort time-dependent (TD) magnetic field of the order of 10(9) G is investigated through a quantum fluid dynamics (QFD) and current-density functional theory (CDFT) based approach using vector exchange-correlation (XC) potential and energy density functional that depend not only on the electronic charge-density but also on the current density. The TD-QFD-CDFT computations are performed in a parallel internuclear-axis and magnetic field-axis configuration at the field-free equilibrium internuclear separation R = 1.3 au with the field-strength varying between 0 and 10(11) G. The TD behavior of the exchange- and correlation energy of the He 2++ is analyzed and compared with that obtained using a [B-TD-QFD-density functional theory (DFT)] approach based on the conventional TD-DFT under similar computational constraints but using only scalar XC potential and energy density functional dependent on the electronic charge-density alone. The CDFT based approach yields TD exchange- and correlation energy and TD electronic charge-density significantly different from that obtained using the conventional TD-DFT based approach, particularly, at typical magnetic field strengths and during a typical time period of the TD field. This peculiar behavior of the CDFT-based approach is traced to the TD current-density dependent vector XC potential, which can induce nonadiabatic effects causing retardation of the oscillating electronic charge density. Such dissipative electron dynamics of the He 2++ molecular ion is elucidated by treating electronic charge density as an electron-"fluid" in the terminology of QFD. Copyright © 2011 Wiley Periodicals, Inc.

  17. Quasilongitudinal soliton in a two-dimensional strongly coupled complex dusty plasma in the presence of an external magnetic field.

    Science.gov (United States)

    Ghosh, Samiran

    2014-09-01

    The propagation of a nonlinear low-frequency mode in two-dimensional (2D) monolayer hexagonal dusty plasma crystal in presence of external magnetic field and dust-neutral collision is investigated. The standard perturbative approach leads to a 2D Korteweg-de Vries (KdV) soliton for the well-known dust-lattice mode. However, the Coriolis force due to crystal rotation and Lorentz force due to magnetic field on dust particles introduce a linear forcing term, whereas dust-neutral drag introduce the usual damping term in the 2D KdV equation. This new nonlinear equation is solved both analytically and numerically to show the competition between the linear forcing and damping in the formation of quasilongitudinal soliton in a 2D strongly coupled complex (dusty) plasma. Numerical simulation on the basis of the typical experimental plasma parameters and the analytical solution reveal that the neutral drag force is responsible for the usual exponential decay of the soliton, whereas Coriolis and/or Lorentz force is responsible for the algebraic decay as well as the oscillating tail formation of the soliton. The results are discussed in the context of the plasma crystal experiment.

  18. Optimizing Power Density and Efficiency of a Double-Halbach Array Permanent-Magnet Ironless Axial-Flux Motor

    Science.gov (United States)

    Duffy, Kirsten P.

    2016-01-01

    NASA Glenn Research Center is investigating hybrid electric and turboelectric propulsion concepts for future aircraft to reduce fuel burn, emissions, and noise. Systems studies show that the weight and efficiency of the electric system components need to be improved for this concept to be feasible. This effort aims to identify design parameters that affect power density and efficiency for a double-Halbach array permanent-magnet ironless axial flux motor configuration. These parameters include both geometrical and higher-order parameters, including pole count, rotor speed, current density, and geometries of the magnets, windings, and air gap.

  19. Effects of dynamic diffraction conditions on magnetic parameter determination in a double perovskite Sr2FeMoO6 using electron energy-loss magnetic chiral dichroism.

    Science.gov (United States)

    Wang, Z C; Zhong, X Y; Jin, L; Chen, X F; Moritomo, Y; Mayer, J

    2017-05-01

    Electron energy-loss magnetic chiral dichroism (EMCD) spectroscopy, which is similar to the well-established X-ray magnetic circular dichroism spectroscopy (XMCD), can determine the quantitative magnetic parameters of materials with high spatial resolution. One of the major obstacles in quantitative analysis using the EMCD technique is the relatively poor signal-to-noise ratio (SNR), compared to XMCD. Here, in the example of a double perovskite Sr 2 FeMoO 6 , we predicted the optimal dynamical diffraction conditions such as sample thickness, crystallographic orientation and detection aperture position by theoretical simulations. By using the optimized conditions, we showed that the SNR of experimental EMCD spectra can be significantly improved and the error of quantitative magnetic parameter determined by EMCD technique can be remarkably lowered. Our results demonstrate that, with enhanced SNR, the EMCD technique can be a unique tool to understand the structure-property relationship of magnetic materials particularly in the high-density magnetic recording and spintronic devices by quantitatively determining magnetic structure and properties at the nanometer scale. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Magnetic susceptibility and specific heat of uranium double perovskite oxides Ba2 MUO6 (M=Co, Ni)

    International Nuclear Information System (INIS)

    Hinatsu, Yukio; Doi, Yoshihiro

    2006-01-01

    Double perovskites Ba 2 MUO 6 (M=Co, Ni) were prepared by the solid-state reaction. X-ray diffraction measurements show that both cobalt (nickel) and uranium ions are ordered in the NaCl type over the six-coordinate B sites of the perovskite ABO 3 . Detailed magnetic susceptibility and specific heat measurements show that Ba 2 CoUO 6 and Ba 2 NiUO 6 order ferromagnetically at 9.1 and 25 K, respectively. From the analysis of the magnetic specific heat, the ground states of the Co 2+ and Ni 2+ ions were determined. - Graphical abstract: The crystal structure for Ba 2 CoUO 6 and Ba 2 NiUO 6 . They crystallize in the cubic double perovskite-type structure and order ferromagnetically at 9.1 and 25 K, respectively

  1. Cyclotron resonance study of the two-dimensional electron layers and double layers in tilted magnetic fields

    Czech Academy of Sciences Publication Activity Database

    Goncharuk, Natalya; Smrčka, Ludvík; Kučera, Jan

    2004-01-01

    Roč. 22, - (2004), s. 590-593 ISSN 1386-9477. [International Conference on Electronic Properties of Two-Dimensional Systems /15./. Nara, 14.07.2003-18.07.2003] R&D Projects: GA ČR GA202/01/0754 Institutional research plan: CEZ:AV0Z1010914 Keywords : single layer * double layer * two-dimensional electron system * cyclotron resonance Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.898, year: 2004

  2. Ion-acoustic double layers in magnetized positive-negative ion plasmas with nonthermal electrons

    Science.gov (United States)

    El-Labany, S. K.; Sabry, R.; El-Taibany, W. F.; Elghmaz, E. A.

    2012-07-01

    The nonlinear ion-acoustic double layers (IADLs) in a warm magnetoplasma with positive-negative ions and nonthermal electrons are investigated. For this purpose, the hydrodynamic equations for the positive-negative ions, nonthermal electron density distribution, and the Poisson equation are used to derive a modified Zakharov-Kuznetsov (MZK) equation, in the small amplitude regime. It is found that compressive and rarefactive IADLs strongly depend on the mass and density ratios of the negative-to-positive ions as well as the nonthermal electron parameter. Also, it is shown that there are one critical value for the density ratio of the negative-to-positive ions ( ν), the ratio between unperturbed electron-to-positive ion density ( μ), and the nonthermal electron parameter ( β), which decide the existence of positive and negative IADLs. The present study is applied to examine the small amplitude nonlinear IADL excitations for the (H+, O2-) and (H+,H-) plasmas, where they are found in the D- and F-regions of the Earth's ionosphere. This investigation should be helpful in understanding the salient features of the nonlinear IADLs in either space or laboratory plasmas where two distinct groups of ions and non-Boltzmann distributed electrons are present.

  3. Quark matter and quark stars in strong magnetic fields at finite temperature within the confined-isospin-density-dependent mass model

    Science.gov (United States)

    Chu, Peng-Cheng; Li, Xiao-Hua; Ma, Hong-Yang; Wang, Bin; Dong, Yu-Min; Zhang, Xiao-Min

    2018-03-01

    We study the properties of strange quark matter (SQM) and quark stars (QSs) in strong magnetic fields within the extended confined isospin-density-dependent mass (CIDDM) model including the temperature dependence of the equivalent mass for quarks. The quark symmetry energy, quark symmetry free energy, and the equation of state (EOS) of SQM in constant magnetic fields at finite temperature are investigated, and it is found that including the temperature dependence in CIDDM model and considering strong magnetic fields can both significantly influence the properties of the SQM and the maximum mass of quark stars. Using the density-dependent magnetic field and assuming two extreme cases for the magnetic field orientation in QSs (the radial orientation in which the local magnetic fields are along the radial direction and the transverse orientation in which the local magnetic fields are randomly oriented but perpendicular to the radial orientation), we analyze the mass-radius relations for different stages of the protoquark stars (PQSs) along the star evolution. Our results indicate that the maximum mass of magnetized PQSs may depend on not only the strength distribution and the orientation of the magnetic fields inside the PQSs, but also the heating process and the cooling process in the star evolution.

  4. Research on a new magnetic-field-modulated brushless double-rotor machine with sinusoidal-permeance modulating ring

    Science.gov (United States)

    Zheng, Ping; Liu, Jiaqi; Bai, Jingang; Song, Zhiyi; Liu, Yong

    2017-05-01

    The magnetic-field-modulated brushless double-rotor machine (MFM-BDRM), composed of a stator, a modulating ring rotor, and a PM rotor, is a kind of power-split device for hybrid electric vehicles (HEVs). In this paper, a new MFM-BDRM with sinusoidal-permeance modulating ring named Sinusoidal-Permeance-Modulating-Ring Brushless Double-Rotor Machine (SPMR-BDRM) is proposed to solve the problem of poor mechanical strength and large iron loss. The structure and the operating principle of the MFM-BDRM are introduced. The design principle of the sinusoidal-permeance modulating ring is analyzed and derived. The main idea of that is to minimize the harmonic permeance of air gap, thereby the harmonic magnetic fields can be restrained. There are comparisons between a MFM-BDRM with sinusoidal-permeance modulating ring and a same size MFM-BDRM with traditional modulating ring, including magnetic field distributions and electromagnetic performances. Most importantly, the iron losses are compared under six different conditions. The result indicates that the harmonic magnetic fields in the air gap are restrained; the electromagnetic torque and power factor are almost the same with same armature current; the torque ripples of the modulating ring rotor and the PM rotor are reduced; the stator loss is reduced by 13% at least and the PM loss is reduced by 20% at least compared with the same size traditional MFM-BDRM under the same operating conditions.

  5. Research on a new magnetic-field-modulated brushless double-rotor machine with sinusoidal-permeance modulating ring

    Directory of Open Access Journals (Sweden)

    Ping Zheng

    2017-05-01

    Full Text Available The magnetic-field-modulated brushless double-rotor machine (MFM-BDRM, composed of a stator, a modulating ring rotor, and a PM rotor, is a kind of power-split device for hybrid electric vehicles (HEVs. In this paper, a new MFM-BDRM with sinusoidal-permeance modulating ring named Sinusoidal-Permeance-Modulating-Ring Brushless Double-Rotor Machine (SPMR-BDRM is proposed to solve the problem of poor mechanical strength and large iron loss. The structure and the operating principle of the MFM-BDRM are introduced. The design principle of the sinusoidal-permeance modulating ring is analyzed and derived. The main idea of that is to minimize the harmonic permeance of air gap, thereby the harmonic magnetic fields can be restrained. There are comparisons between a MFM-BDRM with sinusoidal-permeance modulating ring and a same size MFM-BDRM with traditional modulating ring, including magnetic field distributions and electromagnetic performances. Most importantly, the iron losses are compared under six different conditions. The result indicates that the harmonic magnetic fields in the air gap are restrained; the electromagnetic torque and power factor are almost the same with same armature current; the torque ripples of the modulating ring rotor and the PM rotor are reduced; the stator loss is reduced by 13% at least and the PM loss is reduced by 20% at least compared with the same size traditional MFM-BDRM under the same operating conditions.

  6. Validation of numerical solvers for liquid metal flow in a complex geometry in the presence of a strong magnetic field

    Science.gov (United States)

    Patel, Anita; Pulugundla, Gautam; Smolentsev, Sergey; Abdou, Mohamed; Bhattacharyay, Rajendraprasad

    2018-04-01

    Following the magnetohydrodynamic (MHD) code validation and verification proposal by Smolentsev et al. (Fusion Eng Des 100:65-72, 2015), we perform code to code and code to experiment comparisons between two computational solvers, FLUIDYN and HIMAG, which are presently considered as two of the prospective CFD tools for fusion blanket applications. In such applications, an electrically conducting breeder/coolant circulates in the blanket ducts in the presence of a strong plasma-confining magnetic field at high Hartmann numbers, it{Ha} (it{Ha}^2 is the ratio between electromagnetic and viscous forces) and high interaction parameters, it{N} (it{N} is the ratio of electromagnetic to inertial forces). The main objective of this paper is to provide the scientific and engineering community with common references to assist fusion researchers in the selection of adequate computational means to be used for blanket design and analysis. As an initial validation case, the two codes are applied to the classic problem of a laminar fully developed MHD flows in a rectangular duct. Both codes demonstrate a very good agreement with the analytical solution for it{Ha} up to 15, 000. To address the capabilities of the two codes to properly resolve complex geometry flows, we consider a case of three-dimensional developing MHD flow in a geometry comprising of a series of interconnected electrically conducting rectangular ducts. The computed electric potential distributions for two flows (Case A) it{Ha}=515, it{N}=3.2 and (Case B) it{Ha}=2059, it{N}=63.8 are in very good agreement with the experimental data, while the comparisons for the MHD pressure drop are still unsatisfactory. To better interpret the observed differences, the obtained numerical data are analyzed against earlier theoretical and experimental studies for flows that involve changes in the relative orientation between the flow and the magnetic field.

  7. Magnetic and thermal responses triggered by structural changes in the double perovskite Sr2YRuO6.

    Science.gov (United States)

    Bernardo, P L; Ghivelder, L; Eslava, G G; Amorim, H S; Sinnecker, E H C; Felner, I; Neumeier, J J; García, S

    2012-12-05

    Among double perovskites, the interpretation of the magnetic, thermal and transport properties of Sr(2)YRuO(6) remains a challenge. Characterization using different techniques reveals a variety of features that are not understood, described as anomalous, and yields contradictory values for several relevant parameters. We solved this situation through detailed susceptibility, specific heat, thermal expansion and x-ray diffraction measurements, including a quantitative correlation of the parameters characterizing the so-called anomalies. The emergence of short-range magnetic correlations, surviving well above the long-range transition, naturally accounts for the observed unconventional behavior of this compound. High resolution x-ray powder diffraction and thermal expansion results conclusively show that the magnetic and thermal responses are driven by lattice changes, providing a comprehensive scenario in which the interplay between the spin and structural degrees of freedom plays a relevant role.

  8. Structural phase transition and magnetic properties of double perovskites Ba2CaMO6 (M=W, Re, Os)

    International Nuclear Information System (INIS)

    Yamamura, Kazuhiro; Wakeshima, Makoto; Hinatsu, Yukio

    2006-01-01

    Structures and magnetic properties for double perovskites Ba 2 CaMO 6 (M=W, Re, Os) were investigated. Both Ba 2 CaReO 6 and Ba 2 CaWO 6 show structural phase transitions at low temperatures. For Ba 2 CaReO 6 , the second order transition from cubic Fm3-bar m to tetragonal I4/m has been observed near 120K. For Ba 2 CaWO 6 , the space group of the crystal structure is I4/m at 295K and the transition to monoclinic I2/m has been observed between 220K. Magnetic susceptibility measurements show that Ba 2 CaReO 6 (S=1/2) and Ba 2 CaOsO 6 (S=1) transform to an antiferromagnetic state below 15.4 and 51K, respectively. Anomalies corresponding to their structural phase transition and magnetic transition have been also observed through specific heat measurements

  9. Structure and magnetic properties of double perovskites SrCaLnRuO6 (Ln = La, Pr, Nd)

    International Nuclear Information System (INIS)

    Sasaki, Akira; Doi, Yoshihiro; Hinatsu, Yukio

    2009-01-01

    Double perovskite compounds SrCaLnRuO 6 (Ln = La, Pr, Nd) were prepared as a single phase. X-ray diffraction measurements show that Ca 2+ and Ln 3+ ions are partially disordered at the A site and half of the B site of the perovskite ABO 3 , and that Ca 2+ /Ln 3+ and Ru 5+ ions are regularly ordered at the B site. These compounds should be represented by SrCa 1-x Ln x [Ln 1-x Ca x ]RuO 6 and x = 0.83-0.93 for Ln = La, Pr, and Nd. Magnetic and specific heat measurements show that any of these compounds orders antiferromagnetically at 10-12 K, which is due to the magnetic interactions between Ru 5+ ions. The analysis of the magnetic entropy change indicates that the ground states of Ru 5+ and Ln 3+ ions are both doublet.

  10. Magnetic and thermal responses triggered by structural changes in the double perovskite Sr2YRuO6

    International Nuclear Information System (INIS)

    Bernardo, P L; Ghivelder, L; Eslava, G G; Amorim, H S; Sinnecker, E H C; García, S; Felner, I; Neumeier, J J

    2012-01-01

    Among double perovskites, the interpretation of the magnetic, thermal and transport properties of Sr 2 YRuO 6 remains a challenge. Characterization using different techniques reveals a variety of features that are not understood, described as anomalous, and yields contradictory values for several relevant parameters. We solved this situation through detailed susceptibility, specific heat, thermal expansion and x-ray diffraction measurements, including a quantitative correlation of the parameters characterizing the so-called anomalies. The emergence of short-range magnetic correlations, surviving well above the long-range transition, naturally accounts for the observed unconventional behavior of this compound. High resolution x-ray powder diffraction and thermal expansion results conclusively show that the magnetic and thermal responses are driven by lattice changes, providing a comprehensive scenario in which the interplay between the spin and structural degrees of freedom plays a relevant role.

  11. Behavior of Particle Depots in Molten Silicon During Float-Zone Growth in Strong Static Magnetic Fields

    Science.gov (United States)

    Jauss, T.; SorgenFrei, T.; Croell, A.; Azizi, M.; Reimann, C.; Friedrich, J.; Volz, M. P.

    2014-01-01

    In the photovoltaics industry, the largest market share is represented by solar cells made from multicrystalline silicon, which is grown by directional solidification. During the growth process, the silicon melt is in contact with the silicon nitride coated crucible walls and the furnace atmosphere which contains carbon monoxide. The dissolution of the crucible coating, the carbon bearing gas, and the carbon already present in the feedstock, lead to the precipitation of silicon carbide, and silicon nitride, at later stages of the growth process. The precipitation of Si3N4 and SiC particles of up to several hundred micrometers in diameter leads to severe problems during the wire sawing process for wafering the ingots. Furthermore the growth of the silicon grains can be negatively influenced by the presence of particles, which act as nucleation sources and lead to a grit structure of small grains and are sources for dislocations. If doped with Nitrogen from the dissolved crucible coating, SiC is a semi conductive material, and can act as a shunt, short circuiting parts of the solar cell. For these reasons, the incorporation of such particles needs to be avoided. In this contribution we performed model experiments in which the transport of intentionally added SiC particles and their interaction with the solid-liquid interface during float zone growth of silicon in strong steady magnetic fields was investigated. SiC particles of 7µm and 60µm size are placed in single crystal silicon [100] and [111] rods of 8mm diameter. This is achieved by drilling a hole of 2mm diameter, filling in the particles and closing the hole by melting the surface of the rod until a film of silicon covers the hole. The samples are processed under a vacuum of 1x10(exp -5) mbar or better, to prevent gas inclusions. An oxide layer to suppress Marangoni convection is applied by wet oxidation. Experiments without and with static magnetic field are carried out to investigate the influence of melt

  12. Strong magnetism observed in carbon nanoparticles produced by the laser vaporization of a carbon pellet in hydrogen-containing Ar balance gas.

    Science.gov (United States)

    Asano, Hirohito; Muraki, Susumu; Endo, Hiroki; Bandow, Shunji; Iijima, Sumio

    2010-08-25

    Nanometer-scale carbon particles driven by the pulsed-laser vaporization of pelletized pure carbon powder at 1000 °C in a hydrogen-containing environment show anomalous magnetism like a superparamagnet, while the sample prepared in 100% of Ar does not show such magnetism. The observed magnetism was unchanged over months in the ambient. The structure of this nanomaterial resembles the foam of a laundry detergent and transmission electron microscopy indicates a clear corrugated line contrast. On the other hand, a sample without strong magnetism does not give such an image contrast. The x-ray diffraction pattern coincides with that of graphite and no other peak is detected. Thermogravimetry indicates that all samples completely burn out up to approx. 820 °C and no material remains after combustion, indicating that the sample does not contain impurity metals. Magnetization is easily saturated by ∼10,000 G at 280 K with no hysteresis, but the hysteresis appears at 4.2 K. This phenomenon is explained by introducing a crystalline anisotropy which restricts the motion of the magnetic moment and stabilizes the remnant magnetization at zero magnetic field. Magnitudes of the saturation magnetization are in the range of 1-5 emu G g(-1) at 4.2 K, which correspond to 0.002-0.01 Bohr magneton per carbon atom. This concentration may be increased by ten times or more, because only about 4-10% of particles have a magnetic domain in the present samples.

  13. Strong magnetism observed in carbon nanoparticles produced by the laser vaporization of a carbon pellet in hydrogen-containing Ar balance gas

    Energy Technology Data Exchange (ETDEWEB)

    Asano, Hirohito; Muraki, Susumu; Endo, Hiroki; Bandow, Shunji; Iijima, Sumio, E-mail: bandow@meijo-u.ac.j [Department of Materials Science and Engineering, Meijo University, 1-501 Shiogamaguchi, Tenpaku, Nagoya 468-8502 (Japan)

    2010-08-25

    Nanometer-scale carbon particles driven by the pulsed-laser vaporization of pelletized pure carbon powder at 1000 {sup 0}C in a hydrogen-containing environment show anomalous magnetism like a superparamagnet, while the sample prepared in 100% of Ar does not show such magnetism. The observed magnetism was unchanged over months in the ambient. The structure of this nanomaterial resembles the foam of a laundry detergent and transmission electron microscopy indicates a clear corrugated line contrast. On the other hand, a sample without strong magnetism does not give such an image contrast. The x-ray diffraction pattern coincides with that of graphite and no other peak is detected. Thermogravimetry indicates that all samples completely burn out up to approx. 820 {sup 0}C and no material remains after combustion, indicating that the sample does not contain impurity metals. Magnetization is easily saturated by {approx} 10 000 G at 280 K with no hysteresis, but the hysteresis appears at 4.2 K. This phenomenon is explained by introducing a crystalline anisotropy which restricts the motion of the magnetic moment and stabilizes the remnant magnetization at zero magnetic field. Magnitudes of the saturation magnetization are in the range of 1-5 emu G g{sup -1} at 4.2 K, which correspond to 0.002-0.01 Bohr magneton per carbon atom. This concentration may be increased by ten times or more, because only about 4-10% of particles have a magnetic domain in the present samples.

  14. Progress on The GEMS (Gravity Electro-Magnetism-Strong) Theory of Field Unification and Its Application to Space Problems

    International Nuclear Information System (INIS)

    Brandenburg, J. E.

    2008-01-01

    Progress on the GEMS (Gravity Electro-Magnetism-Strong), theory is presented as well as its application to space problems. The GEMS theory is now validated through the Standard Model of physics. Derivation of the value of the Gravitation constant based on the observed variation of α with energy: results in the formula G congruent with (ℎ/2π)c/M ηc 2 exp(-1/(1.61α)), where α is the fine structure constant,(ℎ/2π), is Planck's constant, c, is the speed of light, and M ηc is the mass of the η cc Charmonium meson that is shown to be identical to that derived from the GEM postulates. Covariant formulation of the GEM theory is now possible through definition of the spacetime metric tensor as a portion of the EM stress tensor normalized by its own trace: g ab = 4(F c a F cb )/(F ab F ab ), it is found that this results in a massless ground state vacuum and a Newtonian gravitation potential φ = 1/2 E 2 /B 2 . It is also found that a Lorentz or flat-space metric is recovered in the limit of a full spectrum ZPF

  15. Surface-termination-dependent magnetism and strong perpendicular magnetocrystalline anisotropy of an FeRh(001) thin film

    Czech Academy of Sciences Publication Activity Database

    Jekal, S.; Rhim, S.H.; Hong, S.C.; Son, W.-J.; Shick, Alexander

    2015-01-01

    Roč. 92, č. 6 (2015), " 064410-1"-" 064410-6" ISSN 1098-0121 R&D Projects: GA ČR GA15-07172S Institutional support: RVO:68378271 Keywords : magnetic anisotropy * magnetic recording * surface science Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.736, year: 2014

  16. Magnetic-Flux-Controlled Giant Fano Factor for Coherent Tunneling Through a Parallel Double-Quantum-Dot

    International Nuclear Information System (INIS)

    Dong Bing; Lei Xiaolin; Cui Hongliang

    2008-01-01

    We report our studies of zero-frequency shot noise in tunneling through a parallel-coupled quantum dot interferometer by employing number-resolved quantum rate equations. We show that the combination of quantum interference effect between two pathways and strong Coulomb repulsion could result in a giant Fano factor, which is controllable by tuning the enclosed magnetic flux

  17. Conductance of graphene based normal-superconductor junction with double magnetic barriers

    Science.gov (United States)

    Abdollahipour, B.; Mohebalipour, A.; Maleki, M. A.

    2018-05-01

    We study conductance of a graphene based normal metal-superconductor junction with two magnetic barriers. The magnetic barriers are induced via two applied magnetic fields with the same magnitudes and opposite directions accompanied by an applied electrostatic potential. We solve Dirac-Bogoliubov-De-Gennes (DBdG) equation to calculate conductance of the junction. We find that applying the magnetic field leads to suppression of the Andreev reflection and conductance for all energies. On the other hand, we observe a crossover from oscillatory to tunneling behavior of the conductance as a function of the applied potential by increasing the magnetic field.

  18. Sc2NiMnO6: A Double-Perovskite with a Magnetodielectric Response Driven by Multiple Magnetic Orders.

    Science.gov (United States)

    Yi, Wei; Princep, Andrew J; Guo, Yanfeng; Johnson, Roger D; Khalyavin, Dmitry; Manuel, Pascal; Senyshyn, Anatoliy; Presniakov, Igor A; Sobolev, Alexey V; Matsushita, Yoshitaka; Tanaka, Masahiko; Belik, Alexei A; Boothroyd, Andrew T

    2015-08-17

    Perovskite materials provide a large variety of interesting physical properties and applications. Here, we report on unique properties of a fully ordered magnetodielectric double-perovskite, Sc2NiMnO6 (space group P21/n, a = 4.99860 Å, b = 5.35281 Å, c = 7.34496 Å, and β = 90.7915°), exhibiting sequential magnetic transitions at T1 = 35 K and T2 = 17 K. The transition at T1 corresponds to a single-k antiferromagnetic phase with propagation vector k1 = (1/2, 0, 1/2), while the second transition at T2 corresponds to a 2-k magnetic structure with propagation vectors k1 = (1/2, 0, 1/2) and k2 = (0, 1/2, 1/2). Symmetry analysis suggests that the two ordering wave vectors are independent, and calculations imply that k1 is associated with the Mn sublattice and k2 with the Ni sublattice, suggesting that Mn-Ni coupling is very small or absent. A magnetodielectric anomaly at T2 likely arises from an antiferroelectric ordering that results from the exchange-striction between the two magnetic sublattices belonging to k1 and k2. The behavior of Sc2NiMnO6 demonstrates 3d double-perovskites with small A-site cations as a promising avenue in which to search for magnetoelectric materials.

  19. First-principles study of magnetic, electronic and optical properties of double perovskite Bi2FeMnO6

    Science.gov (United States)

    Ahmed, Towfiq; Yarotski, Dzmitry; Jia, Quanxi; Zhu, Jian-Xin

    2015-03-01

    We study magnetic, electronic and optical properties of double perovskite Bi2FeMnO6 (BFMO) using density functional theory. In these systems, the exchange interaction between Fe and Mn sites gives rise to a ferrimagnetic ordering, which is captured in our ab initio calculations. Thin film Bi2FeMnO6 (BFMO) are generally grown on substrates such as SrTiO3 and Si. Significant strain has been experimentally observed in BFMO unit cells due to slight lattice mismatch between the thin film and substrate unit cells. In this work, we find that the net magnetic moment in BFMO depends on the ``c/a'' ratio of the unit cell, suggesting the strain dependence of magnetization in such system. We further calculate x-ray magnetic dichroism (XMCD) signals of Fe and Mn ions in BFMO for L2 and L3 edges. By applying the XMCD sum rules, we adopted an alternative approach to estimate the spin and orbital magnetic moment from our DFT calculations. We find qualitative agreement between our calculated values and the experimental measurements based on different techniques.Moreover, we study spin resolved optical conductivity and density of states in BFMO. These calculations give insight into electronic structure near Fermi energy, and dominant electronic excitations in the valence-conduction region of BFMO. This work was supported by U.S. DOE at LANL under Contract No. DE-AC52-06NA25396, the LANL LDRD Program.

  20. Double salt ionic liquids based on 1-ethyl-3-methylimidazolium acetate and hydroxyl-functionalized ammonium acetates: strong effects of weak interactions.

    Science.gov (United States)

    Pereira, Jorge F B; Barber, Patrick S; Kelley, Steven P; Berton, Paula; Rogers, Robin D

    2017-10-11

    The properties of double salt ionic liquids based on solutions of cholinium acetate ([Ch][OAc]), ethanolammonium acetate ([NH 3 (CH 2 ) 2 OH][OAc]), hydroxylammonium acetate ([NH 3 OH][OAc]), ethylammonium acetate ([NH 3 CH 2 CH 3 ][OAc]), and tetramethylammonium acetate ([N(CH 3 ) 4 ][OAc]) in 1-ethyl-3-methylimidazolium acetate ([C 2 mim][OAc]) were investigated by NMR spectroscopy and X-ray crystallography. Through mixture preparation, the solubility of [N(CH 3 ) 4 ][OAc] is the lowest, and [Ch][OAc] shows a 3-fold lower solubility than the other hydroxylated ammonium acetate-based salts in [C 2 mim][OAc] at room temperature. NMR and X-ray crystallographic studies of the pure salts suggest that the molecular-level mechanisms governing such miscibility differences are related to the weaker interactions between the -NH 3 groups and [OAc] - , even though three of these salts possess the same strong 1 : 1 hydrogen bonds between the cation -OH group and the [OAc] - ion. The formation of polyionic clusters between the anion and those cations with unsatisfied hydrogen bond donors seems to be a new tool by which the solubility of these salts in [C 2 mim][OAc] can be controlled.

  1. Evolution of the spin-split quantum Hall states with magnetic field tilt in the InAs-based double quantum wells

    NARCIS (Netherlands)

    Yakunin, M.V.; de Visser, A.; Galistu, G.; Podgornykh, S.M.; Sadofyev, Y.G.; Shelushinina, N.G.; Harus, G.I.

    2009-01-01

    Development of quantum Hall peculiarities due to mobility gap between spin-split magnetic levels with addition of the parallel magnetic field component B|| is analyzed in double quantum wells (DQW) created in InGaAs/GaAs and InAs/AlSb heterosystems chosen due to their relatively large bulk

  2. Cationic ordering and role of the B-site lanthanide(III) and molybdenum(V) cations on the structure and magnetism of double perovskites Sr{sub 2}LnMoO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pinacca, R.M.; Larrégola, S.A.; López, C.A. [INTEQUI-Área de Química General e Inorgánica “Dr. G.F. Puelles”, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Pedregosa, J.C., E-mail: jpedreg@gmail.com [INTEQUI-Área de Química General e Inorgánica “Dr. G.F. Puelles”, Facultad de Química, Bioquímica y Farmacia, Universidad Nacional de San Luis, Chacabuco y Pedernera, 5700 San Luis (Argentina); Pomjakushin, Vladimir [Laboratory for Neutron Scattering, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Sánchez, R.D. [Centro Atómico Bariloche, Comisión Nacional de Energía Atómica and Instituto Balseiro, Universidad Nacional de Cuyo, 8400 S.C. de Bariloche, Río Negro (Argentina); Alonso, J.A. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain)

    2015-06-15

    Highlights: • Five new double perovskites of formula Sr{sub 2}LnMoO{sub 6} were synthesized. • All the samples crystallize in the monoclinic P2{sub 1}/n space group. • Strong reducing conditions were used in order to stabilized Mo(V) cations. • A complete ordering between the rare earth and molybdenum ions was observed. • Magnetism agrees with the crystal distortions observed from Rietveld analysis. - Abstract: We describe the preparation, crystal structure determination and magnetic properties of a new series of ordered double perovskite oxides Sr{sub 2}LnMoO{sub 6} (Ln = Eu, Gd, Dy, Ho, Er, Yb) with Mo{sup 5+} and Ln{sup 3+} electronic configurations. These compounds have been obtained by solid state reaction under reducing conditions in order to stabilize Mo{sup 5+} cations. Structural characterization by XRPD and NPD was performed when Ln = Ho, Er, Yb and just XRPD for absorbing Ln = Eu, Gd, Dy. At room temperature, an excellent Rietveld fit was obtained for all the samples in a monoclinic symmetry, space group P2{sub 1}/n, with long-range ordering of Ln and Mo atoms. Magnetic susceptibility measurements show that some of these materials present magnetic ordering below 25 K and the determined effective magnetic moments are consistent with those expected for the pair Ln{sup 3+}–Mo{sup 5+}. All the phases have negative values​​ of the Weiss temperature indicating dominance of antiferromagnetic interactions.

  3. Electric and magnetic field modulated energy dispersion, conductivity and optical response in double quantum wire with spin-orbit interactions

    Science.gov (United States)

    Karaaslan, Y.; Gisi, B.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.

    2018-02-01

    We study the influence of electric field on the electronic energy band structure, zero-temperature ballistic conductivity and optical properties of double quantum wire. System described by double-well anharmonic confinement potential is exposed to a perpendicular magnetic field and Rashba and Dresselhaus spin-orbit interactions. Numerical results show up that the combined effects of internal and external agents cause the formation of crossing, anticrossing, camel-back/anomaly structures and the lateral, downward/upward shifts in the energy dispersion. The anomalies in the energy subbands give rise to the oscillation patterns in the ballistic conductance, and the energy shifts bring about the shift in the peak positions of optical absorption coefficients and refractive index changes.

  4. Crystal and magnetic structure of the double perovskite Sr2CoUO6: a neutron diffraction study.

    Science.gov (United States)

    Pinacca, R; Viola, M C; Pedregosa, J C; Muñoz, A; Alonso, J A; Martínez, J L; Carbonio, R E

    2005-02-07

    Sr2CoUO6 double perovskite has been prepared as a polycrystalline powder by solid-state reaction, in air. This material has been studied by X-ray, neutron powder diffraction (NPD) and magnetic measurements. At room temperature, the crystal structure is monoclinic, space group P2(1)/n, Z= 2, with a= 5.7916(2), b= 5.8034(2), c= 8.1790(3) A, beta= 90.1455(6)degrees. The perovskite lattice consists of a completely ordered array of CoO6 and UO6 octahedra, which exhibit an average tilting angle phi= 11.4 degrees. Magnetic and neutron diffraction measurements indicate an antiferromagnetic ordering below TN = 10 K. The low-temperature magnetic structure was determined by NPD, selected among the possible magnetic solutions compatible with the P2(1)/n space group, according with the group theory representation. The propagation vector is k= 0. A canted antiferromagnetic structure is observed below TN = 10 K, which remains stable down to 3 K, with an ordered magnetic moment of 2.44(7)mu(B) for Co2+ cations. The magnetic moment calculated from the Curie-Weiss law at high temperatures (5.22 mu(B)/f.u.) indicates that the orbital contribution is unquenched at high temperatures, which is consistent with high-spin Co2+((4)T(1g) ground state) in a quasi-regular octahedral environment. Magnetic and structural features are consistent with an electronic configuration Co2+[3d(7)]-U6+[Rn].

  5. Double-enhanced lateral flow immunoassay for potato virus X based on a combination of magnetic and gold nanoparticles.

    Science.gov (United States)

    Razo, Shyatesa C; Panferov, Vasily G; Safenkova, Irina V; Varitsev, Yuri A; Zherdev, Anatoly V; Dzantiev, Boris B

    2018-05-12

    This study presents the joint use of magnetic nanoparticles (MNPs) and gold nanoparticles (GNPs) for double enhancement in a lateral flow immunoassay (LFIA). The study realizes two types of enhancement: (1) increasing the concentration of analytes in the samples using conjugates of MNPs with specific antibodies and (2) increasing the visibility of the label through MNP aggregation caused by GNPs. The proposed strategy was implemented using a LFIA for potato virus X (PVX), a significant potato pathogen. MNPs conjugated with biotinylated antibodies specific to PVX and GNPs conjugated with streptavidin were synthesized and characterized. The LFIAs with and without the proposed enhancements were compared. The double-enhanced LFIA achieved the highest sensitivity, equal to 0.25 ng mL -1 and 32 times more sensitivity than the non-enhanced LFIA (detection limit: 8 ng mL -1 ). LFIAs using one of the types of amplification (magnetic concentration without GNPs-causing aggregation or MNP aggregation without the concentration stage) showed intermediate levels of sensitivity. The double-enhanced LFIA was successfully used for PVX detection in potato leaves. The results for PVX detection in the infected plants were similar for the double-enhanced LFIA developed and the conventional LFIA based on the GNP conjugates; however, the new system provided significant coloring enhancement. This study confirmed that a simple combination of MNPs and GNPs has great potential for high-sensitivity detection and could possibly be adopted for LFIAs of other compounds. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Characterization of Magnetic Field Immersed Photomultipliers from Double Chooz Experiment. Design and Construction of their Magnetic Shields; Caracterizacion de los fotomultiplicadores del experimento Double Chooz bajo campo magnetico y diseno y construccion de sus blindajes magneticos

    Energy Technology Data Exchange (ETDEWEB)

    Valdivia Valero, F. J.

    2007-12-28

    Flavour oscillations of neutrinos are a quantum-mechanical effect widely demonstrated. It is explained through interferences of their mass eigenstates, therefore, belonging to the physical area beyond the Standard Model. This work deals with the CIEMAT collaboration in the neutrino experiment Double Chooz. Such an experiment aims to measure the mixture angle {theta}{sub 1}3, one of the PMNS leptonic mixture matrix, with a un reached-before sensibility by decrease of systematic errors. For this, two identical scintillator detectors, equipped with PMT's, will be sited at different distances from two reactors located in the nuclear power plant CHOOZ B (France). The electronic neutrino flux from these reactors will be compared, explaining its deficit by flavour oscillations of these particles. The identity of both detectors will be diminished by the magnetic field effects on the PMT's response. Therefore, this study serves as for quantifying such an effects as for fitting the magnetic shields design that minimize them. Shielding measurements and final design of magnetic shields as much as the effect these ones cause in the PMT's response immersed in a monitored magnetic field are presented. (Author) 85 refs.

  7. Manipulating the spin states in a double molecular magnets tunneling junction

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Liang; Liu, Xi [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Zhang, Zhengzhong, E-mail: zeikeezhang@126.com [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China); Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123 (China); Wang, Ruiqiang [Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China)

    2014-01-17

    We theoretically explore the spin transport through nano-structures consisting of two serially coupled single-molecular magnets (SMM) sandwiched between two nonmagnetic electrodes. We find that the magnetization of SMM can be controlled by the spin transfer torque with respect to the bias voltage direction, and the electron current can be switched on/off in different magnetic structures. Such a manipulation is performed by full electrical manner, and needs neither external magnetic field nor ferromagnetic electrodes in the tunneling junction. The proposal device scheme can be realized with the use of the present technology and has potential applications in molecular spintronics or quantum information processing.

  8. Manipulating the spin states in a double molecular magnets tunneling junction

    Science.gov (United States)

    Jiang, Liang; Liu, Xi; Zhang, Zhengzhong; Wang, Ruiqiang

    2014-01-01

    We theoretically explore the spin transport through nano-structures consisting of two serially coupled single-molecular magnets (SMM) sandwiched between two nonmagnetic electrodes. We find that the magnetization of SMM can be controlled by the spin transfer torque with respect to the bias voltage direction, and the electron current can be switched on/off in different magnetic structures. Such a manipulation is performed by full electrical manner, and needs neither external magnetic field nor ferromagnetic electrodes in the tunneling junction. The proposal device scheme can be realized with the use of the present technology [6] and has potential applications in molecular spintronics or quantum information processing.

  9. Three-dimensional visualization of magnetic domain structure with strong uniaxial anisotropy via scanning hard X-ray microtomography

    Science.gov (United States)

    Suzuki, Motohiro; Kim, Kab-Jin; Kim, Sanghoon; Yoshikawa, Hiroki; Tono, Takayuki; Yamada, Kihiro T.; Taniguchi, Takuya; Mizuno, Hayato; Oda, Kent; Ishibashi, Mio; Hirata, Yuushou; Li, Tian; Tsukamoto, Arata; Chiba, Daichi; Ono, Teruo

    2018-03-01

    An X-ray tomographic technique was developed to investigate the internal magnetic domain structure in a micrometer-sized ferromagnetic sample. The technique is based on a scanning hard X-ray nanoprobe using X-ray magnetic circular dichroism (XMCD). From transmission XMCD images at the Gd L3 edge as a function of the sample rotation angle, the three-dimensional (3D) distribution of a single component of the magnetic vector in a GdFeCo microdisc was reconstructed with a spatial resolution of 360 nm, using a modified algebraic reconstruction algorithm. The method is applicable to practical magnetic materials and can be extended to 3D visualization of the magnetic domain formation process under external magnetic fields.

  10. Development of effective power supply using electric double layer capacitor for static magnetic field coils in fusion plasma experiments.

    Science.gov (United States)

    Inomoto, M; Abe, K; Yamada, T; Kuwahata, A; Kamio, S; Cao, Q H; Sakumura, M; Suzuki, N; Watanabe, T; Ono, Y

    2011-02-01

    A cost-effective power supply for static magnetic field coils used in fusion plasma experiments has been developed by application of an electric double layer capacitor (EDLC). A prototype EDLC power supply system was constructed in the form of a series LCR circuit. Coil current of 100 A with flat-top longer than 1 s was successfully supplied to an equilibrium field coil of a fusion plasma experimental apparatus by a single EDLC module with capacitance of 30 F. The present EDLC power supply has revealed sufficient performance for plasma confinement experiments whose discharge duration times are an order of several seconds.

  11. Interactions among magnetic moments in the double perovskites Sr2Fe1+xMo1−xO6

    International Nuclear Information System (INIS)

    Pilo, J.; Carvajal, E.; Oviedo-Roa, R.; Cruz-Irisson, M.; Navarro, O.

    2014-01-01

    It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr 2 FeMoO 6 are well characterized. In this work we studied the iron rich compounds Sr 2 Fe 1+x Mo 1−x O 6 , using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states

  12. Interactions among magnetic moments in the double perovskites Sr{sub 2}Fe{sub 1+x}Mo{sub 1−x}O{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Pilo, J. [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Carvajal, E., E-mail: ecarvajalq@ipn.mx [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Oviedo-Roa, R. [Programa de Investigación en Ingeniería Molecular, Instituto Mexicano del Petróleo Eje Central Lázaro Cárdenas Norte 152, México, D. F., C. P. 07730, México (Mexico); Cruz-Irisson, M. [Escuela Superior de Ingeniería Mecánica y Eléctrica-Culhuacán, Instituto Politécnico Nacional Av. Santa Ana 1000, México, D. F., C. P. 04430, México (Mexico); Navarro, O. [Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México A.P. 70-360, México, D. F., C. P. 04510, México (Mexico)

    2014-12-15

    It is well known that every double perovskite shows a characteristic magnetic behavior, as a consequence of the interactions among the magnetic moments associated with the atoms in their cells; at the same time, the electric and magnetic properties of the bulk double perovskite Sr{sub 2}FeMoO{sub 6} are well characterized. In this work we studied the iron rich compounds Sr{sub 2}Fe{sub 1+x}Mo{sub 1−x}O{sub 6}, using a supercell to model such concentrations that made Fe richer perovskites by ±66.6% and ±200%. Starting from the stoichiometric double perovskite, and modifying the Fe/Mo ratio in the compound, the study of these materials were based on the calculation of the magnetic moment at each atom, as well as the partial density of states.

  13. EBSD Study on the Effect of a Strong Axial Magnetic Field on the Microstructure and Crystallography of Al-Ni Alloys During Solidification

    Science.gov (United States)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Moreau, Rene; Du, Dafan; Ren, Zhongming; Lu, Xionggang

    2016-03-01

    The effect of a strong magnetic field on the microstructure and crystallography of the primary and eutectic Al3Ni phases in Al-Ni alloys was investigated by using EBSD. The results show that the magnetic field significantly affected the microstructures and crystallography during both volume and directional solidification. As a result, the Al3Ni primary phases were aligned with the crystal direction along the magnetic field and formed a layer-like structure. The magnetic field intensity, solidification temperature, growth speed, and alloy composition played important roles during the alignment process of the Al3Ni primary phase. Indeed, the alignment degree increased with the magnetic field and the solidification temperature during normal solidification. Moreover, the effect of the magnetic field on the crystallography of the Al-Al3Ni eutectic in the Al-Ni alloys was also studied. The applied magnetic field modified the orientation of the preferred growth direction of the Al3Ni eutectic fiber and the crystallographic orientation relationship of the Al-Al3Ni eutectic. The orientation of the preferred growth direction of the Al3Ni eutectic fiber depended mainly on the solidification direction and the alignment of the Al3Ni primary phase. Furthermore, a method for controlling the crystallization process by adjusting the angle between the solidification direction and the magnetic field was proposed.

  14. Double-trap measurement of the proton magnetic moment at 0.3 parts per billion precision.

    Science.gov (United States)

    Schneider, Georg; Mooser, Andreas; Bohman, Matthew; Schön, Natalie; Harrington, James; Higuchi, Takashi; Nagahama, Hiroki; Sellner, Stefan; Smorra, Christian; Blaum, Klaus; Matsuda, Yasuyuki; Quint, Wolfgang; Walz, Jochen; Ulmer, Stefan

    2017-11-24

    Precise knowledge of the fundamental properties of the proton is essential for our understanding of atomic structure as well as for precise tests of fundamental symmetries. We report on a direct high-precision measurement of the magnetic moment μ p of the proton in units of the nuclear magneton μ N The result, μ p = 2.79284734462 (±0.00000000082) μ N , has a fractional precision of 0.3 parts per billion, improves the previous best measurement by a factor of 11, and is consistent with the currently accepted value. This was achieved with the use of an optimized double-Penning trap technique. Provided a similar measurement of the antiproton magnetic moment can be performed, this result will enable a test of the fundamental symmetry between matter and antimatter in the baryonic sector at the 10 -10 level. Copyright © 2017, American Association for the Advancement of Science.

  15. Spin asymmetry calculations of the TMR-V curves in single and double-barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2011-10-01

    Spin-polarization asymmetry is the key parameter in asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) in magnetic tunnel junctions. In this paper, we study the value of the TMR as a function of the applied voltage Va in the single as well as double barrier magnetic tunnel junctions (SMTJ & DMTJ, which are constructed from CoFeB/MgO interfaces) and numerically estimate the possible difference of the TMR-V a curves for negative and positive voltages in the homojunctions. As a result, we found that AVB may help to determine the exact values of Fermi wave vectors for minority and majority conducting spin sub-bands. Moreover, significant asymmetry of the experimental TMR-Va curves, which arises due to different annealing regimes, is explained by different heights of the tunnel barriers and values of the spin asymmetry. The numerical TMR-V a data are in good agreement with experimental ones. © 2011 IEEE.

  16. Biosensor based on the measurements of clustering dynamics of magnetic particles using a double pass setup

    DEFF Research Database (Denmark)

    2014-01-01

    Disclosed herein is a biosensor for optical detection of Brownian relaxation dynamics of magnetic particles measured by light transmission. The magnetic particles can be functionalized with biological ligands for the detection of target analytes in a sample. The setup may be implemented in a disc...

  17. Electron spin resonance and nuclear magnetic resonance of sodium macrostructures in strongly irradiated NaCl-K crystals: Manifestation of quasi-one-dimensional behavior of electrons

    NARCIS (Netherlands)

    Cherkasov, FG; Mustafin, RG; L'vov, SG; Denisenko, GA; den Hartog, HW; Vainshtein, D. I.

    1998-01-01

    Data from an investigation of electron spin resonance and nuclear magnetic resonance of NaCl-K (similar to 1 mole%) crystals strongly irradiated with electrons imply the observation of a metal-insulator transition with decreasing temperature and the manifestation of quasi-one-dimensional electron

  18. Analysis and testing of a double armature brushless dc linear motor with NdFeB permanent magnets

    International Nuclear Information System (INIS)

    Filho, A.F.F.

    1998-01-01

    The use of high-energy product NdFeB permanent magnets benefits the design and features of a double armature brushless dc linear motor. As the linear motor is also slotless, its 5 mm airgap requires a source of high flux to overcome the reluctance and produce an adequate amount of force. The linear motor employs a topology that makes use of five permanent magnets to provide excitation flux. The permanent magnets are arranged in such a way that maximises the force the linear motor can deliver. The actuator produces a force up to 86.2 N at an armature current of 4.5 A. However, the topology makes the actuator prone to saturation. It affects the operation point of the permanent magnets, reduces the airgap flux density and the force, and increases flux leakage. To avoid saturation, a flux compensation scheme was conceived. The results are presented and assessed by means of finite element simulation and by experimental results that presented a good agreement. (orig.)

  19. Simulation of plasma double-layer structures

    International Nuclear Information System (INIS)

    Borovsky, J.E.; Joyce, G.

    1982-01-01

    Electrostatic plasma double layers are numerically simulated by means of a magnetized 2 1/2-dimensional particle-in-cell method. The investigation of planar double layers indicates that these one-dimensional potential structures are susceptible to periodic disruption by instabilities in the low-potential plasmas. Only a slight increase in the double-layer thickness with an increase in its obliqueness to the magnetic field is observed. Weak magnetization results in the double-layer electric-field alignment of accelerated particles and strong magnetization results in their magnetic-field alignment. The numerial simulations of spatially periodic two-dimensional double layers also exhibit cyclical instability. A morphological invariance in two-dimensional double layers with respect to the degree of magnetization implies that the potential structures scale with Debye lengths rather than with gyroradii. Electron-beam excited electrostatic electron-cyclotron waves and (ion-beam driven) solitary waves are present in the plasmas adjacent to the double layers

  20. Rotationally modulated variability and pulsations of the He-rich star CPD -62°2124 with an extraordinarily strong magnetic field

    Science.gov (United States)

    Hubrig, S.; Mikulášek, Z.; Kholtygin, A. F.; Ilyin, I.; Schöller, M.; Järvinen, S. P.; Scholz, R.-D.; Zejda, M.

    2017-11-01

    A longitudinal magnetic field with a strength of 5.2 kG was recently detected in CPD -62°2124, which has a fractional main-sequence lifetime of about 60 per cent. Strongly magnetic early-B type chemically peculiar stars in an advanced evolutionary state are of special interest to understand the evolution of the angular momentum and spin-down time-scales in the presence of a global magnetic field. We made use of 17 FORS 2 low-resolution spectropolarimetric observations and 844 ASAS3 photometric measurements for the determination of the rotation period, pulsationsand the magnetic field geometry of the star. We calculated periodograms and applied phenomenological models of photometric, spectral and spectropolarimetric variability. We found that all quantities studied, specifically equivalent widths, the mean longitudinal magnetic field 〈Bz〉 and the flux in the V filter, vary with the same period P = 2.628 d, which was identified as the rotation period. The observed variations can be fully explained by a rigidly rotating main-sequence star with an uneven distribution of chemical elements, photometric spots and a stable, nearly dipolar magnetic field with a polar field strength of about 21 kG, frozen into the body of the star. The magnetic field of CPD -62°2124 is tilted to the rotation axis by β = 28° ± 7°, while the inclination of the rotation axis towards the line of sight is only i = 20° ± 5°. In the acquired FORS 2 spectra, we detect short-term line profile variations indicating the presence of β Cephei type pulsations. As of today, no other pulsating star of this type is known to possess such a strong magnetic field.

  1. From Positive to Negative Zero-Field Splitting in a Series of Strongly Magnetically Anisotropic Mononuclear Metal Complexes.

    Science.gov (United States)

    Novitchi, Ghénadie; Jiang, Shangda; Shova, Sergiu; Rida, Fatima; Hlavička, Ivo; Orlita, Milan; Wernsdorfer, Wolfgang; Hamze, Rana; Martins, Cyril; Suaud, Nicolas; Guihéry, Nathalie; Barra, Anne-Laure; Train, Cyrille

    2017-12-18

    A series of mononuclear [M(hfa) 2 (pic) 2 ] (Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; pic = 4-methylpyridine; M = Fe II , Co II , Ni II , Zn II ) compounds were obtained and characterized. The structures of the complexes have been resolved by single-crystal X-ray diffraction, indicating that, apart from the zinc derivative, the complexes are in a trans configuration. Moreover, a dramatic lenghthening of the Fe-N distances was observed, whereas the nickel(II) complex is almost perfectly octahedral. The magnetic anisotropy of these complexes was thoroughly studied by direct-current (dc) magnetic measurements, high-field electron paramagnetic resonance, and infrared (IR) magnetospectroscopy: the iron(II) derivative exhibits an out-of-plane anisotropy (D Fe = -7.28 cm -1 ) with a high rhombicity, whereas the cobalt(II) and nickel(II) complexes show in-plane anisotropy (D Co ∼ 92-95 cm -1 ; D Ni = 4.920 cm -1 ). Ab initio calculations were performed to rationalize the evolution of the structure and identify the excited states governing the magnetic anisotropy along the series. For the iron(II) complex, an out-of-phase alternating-current (ac) magnetic susceptibility signal was observed using a 0.1 T dc field. For the cobalt(II) derivative, the ac magnetic susceptibility shows the presence of two field-dependent relaxation phenomena: at low field (500 Oe), the relaxation process is beyond single-ion behavior, whereas at high field (2000 Oe), the relaxation of magnetization implies several mechanisms including an Orbach process with U eff = 25 K and quantum tunneling of magnetization. The observation by μ-SQUID magnetization measurements of hysteresis loops of up to 1 K confirmed the single-ion-magnet behavior of the cobalt(II) derivative.

  2. Denaturation strategies for detection of double stranded PCR products on GMR magnetic biosensor array

    DEFF Research Database (Denmark)

    Rizzi, Giovanni; Lee, Jung-Rok; Guldberg, Per

    2017-01-01

    Microarrays and other surface-based nucleic acid detection schemes rely on the hybridization of the target to surface-bound detection probes. We present the first comparison of two strategies to detect DNA using a giant magnetoresistive (GMR) biosensor platform starting from an initially double...

  3. Commensurability oscillations in a quasi-two-dimensional electron gas subject to strong in-plane magnetic field

    Czech Academy of Sciences Publication Activity Database

    Smrčka, Ludvík

    2016-01-01

    Roč. 77, Mar (2016), s. 108-113 ISSN 1386-9477 Institutional support: RVO:68378271 Keywords : lateral superlattices * commensurability oscillations * in-plane magnetic field Subject RIV: BE - Theoretical Physics Impact factor: 2.221, year: 2016

  4. Ce3 - xMgxCo9 : Transformation of a Pauli Paramagnet into a Strong Permanent Magnet

    Science.gov (United States)

    Lamichhane, Tej N.; Taufour, Valentin; Palasyuk, Andriy; Lin, Qisheng; Bud'ko, Sergey L.; Canfield, Paul C.

    2018-02-01

    We report on the synthesis of single-crystal and polycrystalline samples of Ce3 -xMgxCo9 solid solution (0 ≤x ≲1.4 ) and characterization of their structural and magnetic properties. The crystal structure remains rhombohedral in the whole composition range and Mg partially replaces Ce in the 6 c site of the CeCo3 structure. Ferromagnetism is induced by Mg substitutions starting as low as x =0.18 and reaching a Curie temperature as high as 450 K for x =1.35 . Measurements on single crystals with x =1.34 and TC=440 K indicate an axial magnetic anisotropy with an anisotropy field of 6 T and a magnetization of 6 μB/f .u . at 300 K. Coercicity is observed in the polycrystalline samples consistent with the observed axial magnetic anisotropy. Our discovery of ferromagnetism with large axial magnetic anisotropy induced by substituting a rare-earth element by Mg is a very promising result in the search of inexpensive permanent-magnet materials and suggests that other nonmagnetic phases, similar to CeCo3 , may also conceal nearby ferromagnetic phases.

  5. Magnetic and resonant X-ray scattering investigations of strongly correlated electron systems; Etude de systemes electroniques fortement correles par diffusion magnetique et resonnante des rayons X

    Energy Technology Data Exchange (ETDEWEB)

    Paolasini, L.; Bergevin, F. de [European Synchrotron Radiation Facility, 38 - Grenoble (France)

    2008-06-15

    Resonant X-ray scattering is a method which combines high-Q resolution X-ray elastic diffraction and atomic core-hole spectroscopy for investigating electronic and magnetic long-range ordered structures in condensed matter. During recent years the development of theoretical models to describe resonant X-ray scattering amplitudes and the evolution of experimental techniques, which include the control and analysis of linear photon polarization and the introduction of extreme environment conditions such as low temperatures, high magnetic field and high pressures, have opened a new field of investigation in the domain of strongly correlated electron systems. (authors)

  6. Effect of particle-core-vibration coupling near the double closed $^{132}$Sn nucleus from precise magnetic moment measurements

    CERN Multimedia

    Postma, H; Heyde, K; Walker, P; Grant, I; Veskovic, M; Stone, N; Stone, J

    2002-01-01

    % IS301 \\\\ \\\\ Low temperature nuclear orientation of isotope-separator implanted short-lived radio-isotopes makes possible the measurements of nuclear magnetic dipole moments of oriented ground and excited states with half-lives longer than a few seconds. Coupling schemes characterizing the odd nucleons and ground-state deformations can be extracted from the nuclear moments. \\\\ We thus propose to measure the magnetic dipole moments of $^{127-133}$Sb to high precision using NMR/ON at the NICOLE facility. With (double magic +1) $^{133}$Sb as the reference, the main aim of this experiment is to examine whether the collective component in the 7/2$^+$ Sb ground state magnetic dipole moment varies as expected according to particle-core coupling calculations carried out for the Sb (Z=51) isotopes. Comparison of the 1-proton-particle excitations in Sb to 1-proton-hole states in In nuclei will shed light on differences between particle and hole excitations as understood within the present model. Comparison of ...

  7. Moderate and strong static magnetic fields directly affect EGFR kinase domain orientation to inhibit cancer cell proliferation

    Science.gov (United States)

    Wang, Wenchao; Li, Zhiyuan; Liu, Juanjuan; Yang, Xingxing; Ji, Xinmiao; Luo, Yan; Hu, Chen; Hou, Yubin; He, Qianqian; Fang, Jun; Wang, Junfeng; Liu, Qingsong; Li, Guohui; Lu, Qingyou; Zhang, Xin

    2016-01-01

    Static magnetic fields (SMFs) can affect cell proliferation in a cell-type and intensity-dependent way but the mechanism remains unclear. At the same time, although the diamagnetic anisotropy of proteins has been proposed decades ago, the behavior of isolated proteins in magnetic fields has not been directly observed. Here we show that SMFs can affect isolated proteins at the single molecular level in an intensity-dependent manner. We found that Epidermal Growth Factor Receptor (EGFR), a protein that is overexpressed and highly activated in multiple cancers, can be directly inhibited by SMFs. Using Liquid-phase Scanning Tunneling Microscopy (STM) to examine pure EGFR kinase domain proteins at the single molecule level in solution, we observed orientation changes of these proteins in response to SMFs. This may interrupt inter-molecular interactions between EGFR monomers, which are critical for their activation. In molecular dynamics (MD) simulations, 1-9T SMFs caused increased probability of EGFR in parallel with the magnetic field direction in an intensity-dependent manner. A superconducting ultrastrong 9T magnet reduced proliferation of CHO-EGFR cells (Chinese Hamster Ovary cells with EGFR overexpression) and EGFR-expressing cancer cell lines by ~35%, but minimally affected CHO cells. We predict that similar effects of magnetic fields can also be applied to some other proteins such as ion channels. Our paper will help clarify some dilemmas in this field and encourage further investigations in order to achieve a better understanding of the biological effects of SMFs. PMID:27223425

  8. The Earth's revolution, Moon phase, Syzygy astronomy events, their effect in disturbances of the Earth's geomagnetic field, and the ``Magnetic Storm Double Time Method'' for predicting the occurrence time, magnitude and epicenter location of earthquakes

    Science.gov (United States)

    Chen, I. W.

    2003-04-01

    An increasing number of geomagnetic observation stations were established and operated in China since 1966 to the 1980s (and until present), effectively covering a large area of the nation. Close relativity between magnetic storms and earthquakes, as well as close relativity between the regional differences of magnetic disturbance recorded by these stations and the epicenter location of earthquakes, was discovered and observed by Tie-zheng Zhang during1966 - 1969. On such basis during 1969/1970, Zhang developed the “Magnetic Storm Double Time Method” for predicting the occurrence time, magnitude and epicenter location of EQs. By this method,.Zhang successfully predicted the Yunnan Tonghai Ms7.7 EQ Jan. 5, 1970 (occurrence date only), the Bohai ML5.2 EQ, Feb. 12, 1970 and other EQs, including the Haicheng Ms7.3 EQ Feb. 4, 1975, and the Tangshan Ms7.8 EQ July 28, 1976. On the basis of this method, Z.P. Shen developed the “Geomagnetic Deflection Angle Double Time Method” in 1970, and later developed the “Magnetic Storm - Moon Phase Double Time Method” in 1990s. With this method, Shen is able to predict the occurrence dates of most of the strongest EQs Ms37.5 on the Earth since 1991. Zhang also discovered that strong EQs often correspond with a number of sets of magnetic storms. Z.Q. Ren discovered close relativity exists between Syzygy astronomy events and such sets of magnetic storm as well as the occurrence dates of strong EQs. Computerized calculation of historical magnetic storm and EQ data proves the effectiveness of this method. Over 3,000 days of geomagnetic isoline images are computer processed by the Author from over 400,000 geomagnetic field data obtained by Zhang from over 100 geomagnetic observation stations during 1966 - 1984. Clear relativity is shown between the Earth’s revolution, Moon phases, Syzygy astronomy events related to the Earth, and their disturbance effect on the Earth’s geomagnetic field and the occurrence of EQs.

  9. Electronic and magnetic properties of double perovskite Sr2CoUO6: Heisenberg model

    Science.gov (United States)

    Nid-bahami, A.; Ahmed, S. Sidi; Ait-Tamerd, M.; Zaari, H.; El Kenz, A.; Benyoussef, A.

    2018-01-01

    This work will be focused on the electronic and magnetic properties of Sr2CoUO6 (SCUO) using ab-initio calculations and Monte Carlo Simulation (MCS). Firstly, we calculate the exchange coupling and the crystal field, then, the electronic and magnetic properties will be studied, using the full-potential linearized augmented plane wave (FP-LAPW) method, as implemented in the Wien2k code. This method employing the generalized gradient approximation (GGA) for exchange-correlation term. The half-metallic ferromagnetic nature implies a potential application of this new compound in spintronics devices. Also, we have presented the results of the band structures and densities of states for the two up and down spin polarizations. The exchange coupling and the crystal field calculated are J = 0 . 567 meV and δ = 0 . 559meV, and total spin magnetic moments is 2.96 μB closed to experimental values 3 μB. Secondly, we have presented the results for the magnetization and the susceptibility as a function of temperature. Finally, we obtain the critical temperature T = 9 . 20 K by MCS in good agreement with the experimental value.

  10. Effect of Quench Treatment on Fe/Mo Order and Magnetic Properties of Double Perovskite Sr2FeMoO6

    International Nuclear Information System (INIS)

    Yan-Chun Hu; Ya-Wen Cui; Xian-Wei Wang; Yi-Pu Liu

    2016-01-01

    A quench-treatment technique is used to prepare a high-quality polycrystalline sample of double perovskite Sr 2 FeMoO 6 (SFMO). X-ray powder diffraction analysis reveals that the sample has a single phase and exhibits I4/m symmetry. The cation order η of the sample increases to 98.9(2)% from 94.2(3)%, which is prepared by the traditional sol-gel method. The initial magnetization isotherm of the sample is detected at 300 K. Unit-cell magnetization for the current sample is 1.332 μ B at 300 K, and the one for the traditional sol-gel method sample is 0.946 μ B . Unit-cell magnetization is enhanced to 40.80% by the quench-treatment technique. Quench treatment is an effective method of enhancing the Fe/Mo order and magnetic properties of double perovskite SFMO. (paper)

  11. Synthesis, characterization and magnetic behavior of Mg–Fe–Al mixed oxides based on layered double hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, Angélica C., E-mail: angelicacheredia@gmail.com [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina); Oliva, Marcos I. [IFEG, Universidad Nacional de Córdoba, Córdoba (Argentina); CONICET (Argentina); Agú, Ulises [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina); CONICET (Argentina); Zandalazini, Carlos I. [CONICET (Argentina); INFIQC, FCQ Universidad Nacional de Córdoba, Córdoba (Argentina); Marchetti, Sergio G. [CINDECA, UNLP, Buenos Aires (Argentina); Herrero, Eduardo R.; Crivello, Mónica E. [Universidad Tecnológica Nacional, Facultad Regional Córdoba-CITeQ, Maestro López esq. Cruz Roja Argentina, Ciudad Universitaria, 5016 Córdoba (Argentina)

    2013-09-15

    In the present work, Mg–Al–Fe layered double hydroxides were prepared by coprecipitation reaction with hydrothermal treatment. The characterization of precursors and their corresponding calcinated products (mixed oxides) were carried out by X ray diffraction, X-ray photoelectron spectroscopy (XPS), termogravimetric analysis and differential scanning calorimetry, diffuse reflectance UV–vis spectroscopy, specific surface area, Mössbauaer and magnetic properties. The Fe{sup 3+} species were observed in tetrahedrally and octahedrally coordination in brucite layered. The XPS analysis shows that the Fe{sup 3+} ions can be found in two coordination environments (tetrahedral and octahedral) as mixed oxides, and as spinel-structure. Oxides show a decrease in the specific surface areas when the iron loading is increased. The magnetic and Mössbauaer response show that MgAlFe mixed oxides are different behaviours such as different population ratios of ferromagnetic, weak-ferromagnetic, paramagnetic and superparamagnetic phases. The better crystallization of spinel structure with increased temperature, is correlated with the improved magnetic properties. - Highlights: • Mg–Al–Fe were successfully prepared by coprecipitation with hydrothermal treatment. • MgO, α-Fe{sub 2}O{sub 3,} MgFe{sub 2}O{sub 4} were detected by XRD in the calcined samples. • The Fe{sup 3+} is in tetrahedral and octahedral coordination in the brucite layered. • The specific surface area is directly related with the iron content. • The magnetic properties and MgFe{sub 2}O{sub 4} improve with increasing calcination temperature.

  12. Quantum fluid dynamics based current-density functional study of a helium atom in a strong time-dependent magnetic field

    Science.gov (United States)

    Vikas, Hash(0x125f4490)

    2011-02-01

    Evolution of the helium atom in a strong time-dependent (TD) magnetic field ( B) of strength up to 1011 G is investigated through a quantum fluid dynamics (QFD) based current-density functional theory (CDFT). The TD-QFD-CDFT computations are performed through numerical solution of a single generalized nonlinear Schrödinger equation employing vector exchange-correlation potentials and scalar exchange-correlation density functionals that depend both on the electronic charge-density and the current-density. The results are compared with that obtained from a B-TD-QFD-DFT approach (based on conventional TD-DFT) under similar numerical constraints but employing only scalar exchange-correlation potential dependent on electronic charge-density only. The B-TD-QFD-DFT approach, at a particular TD magnetic field-strength, yields electronic charge- and current-densities as well as exchange-correlation potential resembling with that obtained from the time-independent studies involving static (time-independent) magnetic fields. However, TD-QFD-CDFT electronic charge- and current-densities along with the exchange-correlation potential and energy differ significantly from that obtained using B-TD-QFD-DFT approach, particularly at field-strengths >109 G, representing dynamical effects of a TD field. The work concludes that when a helium atom is subjected to a strong TD magnetic field of order >109 G, the conventional TD-DFT based approach differs "dynamically" from the CDFT based approach under similar computational constraints.

  13. Quantum fluid dynamics based current-density functional study of a helium atom in a strong time-dependent magnetic field

    International Nuclear Information System (INIS)

    Vikas

    2011-01-01

    Evolution of the helium atom in a strong time-dependent (TD) magnetic field (B) of strength up to 10 11 G is investigated through a quantum fluid dynamics (QFD) based current-density functional theory (CDFT). The TD-QFD-CDFT computations are performed through numerical solution of a single generalized nonlinear Schroedinger equation employing vector exchange-correlation potentials and scalar exchange-correlation density functionals that depend both on the electronic charge-density and the current-density. The results are compared with that obtained from a B-TD-QFD-DFT approach (based on conventional TD-DFT) under similar numerical constraints but employing only scalar exchange-correlation potential dependent on electronic charge-density only. The B-TD-QFD-DFT approach, at a particular TD magnetic field-strength, yields electronic charge- and current-densities as well as exchange-correlation potential resembling with that obtained from the time-independent studies involving static (time-independent) magnetic fields. However, TD-QFD-CDFT electronic charge- and current-densities along with the exchange-correlation potential and energy differ significantly from that obtained using B-TD-QFD-DFT approach, particularly at field-strengths >10 9 G, representing dynamical effects of a TD field. The work concludes that when a helium atom is subjected to a strong TD magnetic field of order >10 9 G, the conventional TD-DFT based approach differs 'dynamically' from the CDFT based approach under similar computational constraints. (author)

  14. Electron gas interacting in a metal, submitted to a strong magnetic field; Gas de eletrons interagentes num metal, sujeito a um campo magnetico forte

    Energy Technology Data Exchange (ETDEWEB)

    Alcaraz, Francisco Castilho

    1977-07-01

    Using the propagator's technique in the grand ensemble developed by Montroll and Ward we investigate the magnetic properties of an interacting electron gas in a strong magnetic field. The free propagator properly constructed shows that the spin paramagnetism does not have a term with strong temperature dependence, contrary to the result of Isihara. Considering the electron density to be constant, the dHVA oscillations in the magnetic susceptibility and sound velocity, considering the effects of first exchange interactions, show only one phase in agreement with experimental result, while Ichimura and Isihara obtained two phases differing by {pi}/2. The effects of first order exchange interactions in the dHVA oscillations of the magnetic susceptibility and sound velocity give rise to an exponential factor in the amplitudes of oscillator (Dingle factor), being the Dingle temperature linearly dependent of the Fermi velocity. The calculations of the ring diagram contribution to the grand partition function, show that the approximation used by Isihara for this calculations is not good and the dHVA oscillations of the contributions from the ring diagrams for the grand partition function have a phase differing by {pi}/2 from that obtained by Isihara. (author)

  15. On the La.sub.2-x./sub.Sr.sub.x./sub.CoRuO.sub.6./sub. double perovskites: crystal structure, magnetic properties and transport

    Czech Academy of Sciences Publication Activity Database

    Tomeš, P.; Hejtmánek, Jiří; Knížek, Karel

    2008-01-01

    Roč. 10, č. 4 (2008), s. 486-490 ISSN 1293-2558 R&D Projects: GA ČR GA202/06/0051 Institutional research plan: CEZ:AV0Z10100521 Keywords : double perovskite La 2-x Sr x CoRuO 6 * magnetic interactions * charge carrier transport Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.742, year: 2008

  16. Effect of a strong, DC-induced magnetic field on circadian singing activity of the house cricket (orthoptera:gryllidae)

    Energy Technology Data Exchange (ETDEWEB)

    Shaw, K.C.; Bitzer, R.J.; Galliart, L. [Iowa State Univ., Ames, IA (United States)] [and others

    1995-05-01

    We investigated the effect of a strong, DC-induced electromagnetic field (EMF) on the circadian singing activity of the house cricket, Acheta domesticus (L.). Groups of 10 crickets were exposed to strong, DC-induced EMFs under two light regimes, 12:12 (L:D) h and 0:24 (L:D) h. Exposure to the strong EMF resulted in an increase in mean time per hour during which one or more crickets were singing and in number of crickets singing per hour. Correcting for phase shift during O:24 (L:D) h, the daily pattern of singing was apparently unaffected by any treatment. The greatest percentage of singing and number of crickets singing per hour occurred during actual or expected scotophase. This is the first report of an increase in insect activity during exposure to a strong DC-induced EMF.

  17. SISGR: Improved Electrical Energy Storage with Electrochemical Double Layer Capacitance Based on Novel Carbon Electrodes, New Electrolytes, and Thorough Development of a Strong Science Base

    Energy Technology Data Exchange (ETDEWEB)

    Ruoff, Rodney S. [PI; Alam, Todd M. [co-PI; Bielawski, Christopher W. [co-PI; Chabal, Yves [co-PI; Hwang, Gyeong [co-PI; Ishii, Yoshitaka [co-PI; Rogers, Robin [co-PI

    2014-07-23

    The broad objective of the SISGR program is to advance the fundamental scientific understanding of electrochemical double layer capacitance (EDLC) and thus of ultracapacitor systems composed of a new type of electrode based on chemically modified graphene (CMG) and (primarily) with ionic liquids (ILs) as the electrolyte. Our team has studied the interplay between graphene-based and graphene-derived carbons as the electrode materials in electrochemical double layer capacitors (EDLC) systems on the one hand, and electrolytes including novel ionic liquids (ILs), on the other, based on prior work on the subject.

  18. Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain

    Science.gov (United States)

    Gálisová, Lucia

    2017-11-01

    The double-tetrahedral chain in a longitudinal magnetic field, whose nodal lattice sites occupied by the localized Ising spins regularly alternate with triangular plaquettes with the dynamics described by the Hubbard model, is rigorously investigated. It is demonstrated that the uniform change of electron concentration controlled by the chemical potential in a combination with the competition between model parameters and the external magnetic field leads to the formation of one chiral and seven nonchiral phases at the absolute zero temperature. Rational plateaux at one-third and one-half of the saturation magnetization can also be identified in the low-temperature magnetization curves. On the other hand, the gradual electron doping results in 11 different ground-state regions that distinguish from each other by the evolution of the electron distribution during this process. Several doping-dependent magnetization plateaux are observed in the magnetization process as a result of the continuous change of electron content in the model.

  19. Electronic transport in armchair graphene nanoribbon under double magnetic barrier modulation

    Science.gov (United States)

    Wang, Haiyan; Wu, Chao; Xie, Fang; Zhang, Xiaojiao; Zhou, Guanghui

    2018-03-01

    We present a theoretical investigation of the transport properties and the magnetoresistance effect in armchair graphene nanoribbons (AGNRs) under modulation by two magnetic barriers. The energy levels are found to be degenerate for a metallic AGNR but are not degenerate for a semiconducting AGNR. However, the conductance characteristics show quantized plateaus in both the metallic and semiconducting cases. When the magnetization directions of the barriers change from parallel to antiparallel, the conductance plateau in the metallic AGNR shows a degenerate feature due to matching between the transport modes in different regions. As the barrier height increases, the conductance shows more oscillatory behavior with sharp peaks and troughs. Specifically, the initial position of nonzero conductance for the metallic AGNR system moves towards a higher energy regime, which indicates that an energy gap has been opened. In addition, the magnetoresistance ratio also shows plateau structures in certain specific energy regions. These results may be useful in the design of electron devices based on AGNR nanostructures.

  20. A fast spinning magnetic white dwarf in the double degenerate, super-Chandrasekhar system NLTT 12758

    Czech Academy of Sciences Publication Activity Database

    Kawka, Adela; Briggs, G.; Vennes, Stephane; Ferrario, L.; Paunzen, E.; Wickramasinghe, D.T.

    2017-01-01

    Roč. 466, č. 1 (2017), s. 1127-1139 ISSN 0035-8711 R&D Projects: GA ČR GAP209/12/0217; GA ČR GA15-15943S; GA MŠk LG14013; GA MŠk(CZ) LG15010 Institutional support: RVO:67985815 Keywords : close binaries * NLTT 12758 * magnetic field Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 4.961, year: 2016

  1. Magnetic polymer particles prepared by double crosslinking in reverse emulsion with potential biomedical applications

    Czech Academy of Sciences Publication Activity Database

    Balaita, L.; Cadinoiu, A. N.; Postolache, P.; Šafaříková, Miroslava; Popa, M.

    2015-01-01

    Roč. 17, č. 7-8 (2015), s. 1198-1209 ISSN 1454-4164 Grant - others:Ministery of Education of the Czech Republic(CZ) MP0701 Institutional support: RVO:67179843 Keywords : acid-modified chitosan * drug-delivery * nanoparticles * release * microparticles * microspheres * stability * alcohol * complex * Chitosan * Poly(vinyl alcohol) * Magnetic particles * Ionic crosslinking * Covalent crosslinking * Drug delivery Subject RIV: EH - Ecology, Behaviour Impact factor: 0.383, year: 2015

  2. Separation of species of a binary fluid mixture confined in a channel in presence of a strong transverse magnetic field

    Directory of Open Access Journals (Sweden)

    Sharma Bishwaram

    2012-01-01

    Full Text Available Effects of a transverse magnetic field on separation of a binary mixture of incompressible viscous thermally and electrically conducting fluids confined between two stationary parallel plates are examined. Both the plates are maintained at constant temperatures. It is assumed that one of the components, which is rarer and lighter, is present in the mixture in a very small quantity. The equations governing the motion, temperature and concentration in Cartesian coordinate are solved analytically. The solution obtained for concentration distribution is plotted against the width of the channel for various values of non-dimensional parameters. It is found that the effect of transverse magnetic field is to separate the species of rarer and lighter component by contributing its effect directly to the temperature gradient and the pressure gradient. The effects of increase in the values of Hartmann number, magnetic Reynolds number, barodiffusion number, thermal diffusion number, electric field parameter and the product of Prandtl number and Eckert number are to collect the rarer and lighter component near the upper plate and throw away the heavier component towards the lower plate. The problem discussed here derives its application in the basic fluid dynamics separation processes to separate the rare component of the different isotopes of heavier molecules where electromagnetic method of separation does not work.

  3. Ionospheric convection response to changes of interplanetary magnetic field B-z component during strong B-y component

    DEFF Research Database (Denmark)

    Huang, C.S.; Murr, D.; Sofko, G.J.

    2000-01-01

    enough, the B-z reorientation causes changes in the flow intensity but not in the shape of the convection pattern. The results show the characteristics of ionospheric convection response during strong B-y and suggest that the convection reconfiguration is not only determined by the changing B-z but also...... the dawn-dusk meridian plane, which is interpreted as propagation or expansion of newly generated convection cells in the cusp region. Other studies showed that the change in convection pattern in response to IMF reorientations is spatially fixed. In this paper, we investigate the ionospheric convection...... response to IMF Bz changes during strong IMF BZ. On March 23, 1995, B-x was small, B-y was strongly positive (7-11 nT), and the B-z polarity changed several times after 1300 UT. The dayside ionospheric convection is dominated by a large clockwise convection cell. The cell focus (the "eye" of the convection...

  4. Electronic structure, magnetic, mechanical and thermo-physical behavior of double perovskite Ba2MgOsO6

    Science.gov (United States)

    Dar, Sajad Ahmad; Srivastava, Vipul; Sakalle, Umesh Kumar; Parey, Vanshree

    2018-02-01

    The electronic structure, the magnetic, elasto-mechanical and thermodynamic belongings of cubic double oxide perovskites Ba2MgOsO6 have been successfully investigated within the full potential linearized augmented plane wave method (FP-LAPW), based upon the density functional theory (DFT). The structural examination reveals ferromagnetic stability and the spin polarized electronic band structure and density of states display half-metallic nature of the compound. The calculated magnetic moment was found to have an integer value of 2μ_B. From the knowledge of obtained elastic constants mechanical properties like Young's modulus ( E), shear modulus ( G), Poisson ratio (ν) and the anisotropic factor have been predicted. The calculated B/ G and Cauchy pressure ( C_{12}-C_{44}) both portray the ductile nature of the compound. For a complete understanding of the thermo-physical behavior of vital parameters like heat capacity, thermal expansion, Grüneisen parameter and Debye temperature were predicted using quasi harmonic Debye approximation.

  5. The role of nonmagnetic d{sup 0} vs. d{sup 10}B-type cations on the magnetic exchange interactions in osmium double perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Hai L., E-mail: Hai.Feng@cpfs.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Yamaura, Kazunari [Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Tjeng, Liu Hao [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Jansen, Martin, E-mail: M.Jansen@fkf.mpg.de [Max Planck Institute for Chemical Physics of Solids, Dresden 01187 (Germany); Max Planck Institute for Solid State Research, Stuttgart 70569 (Germany)

    2016-11-15

    Polycrystalline samples of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were synthesized by solid state reactions. They adopt the cubic double perovskite structures (space group, Fm-3m) with ordered B and Os arrangements. Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) show antiferromagnetic transitions at 93 K, 69 K, and 28 K, respectively. The Weiss-temperatures are −590 K for Ba{sub 2}ScOsO{sub 6}, −571 K for Ba{sub 2}YOsO{sub 6}, and −155 K for Ba{sub 2}InOsO{sub 6}. Sc{sup 3+} and Y{sup 3+} have the open-shell d{sup 0} electronic configuration, while In{sup 3+} has the closed-shell d{sup 10}. This indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. Comparison of Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) to their Sr and Ca analogues shows that the structural distortions weaken the overall magnetic exchange interactions. - Graphical abstract: Magnetic properties of osmium double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. Comparison of Ba{sub 2}BOsO{sub 6}indicates that a d{sup 0} B-type cation induces stronger overall magnetic exchange interactions in comparison to a d{sup 10}. - Highlights: • Magnetic properties of double perovskites Ba{sub 2}BOsO{sub 6} (B=Sc, Y, In) were studied. • A d{sup 0}B-type cation induces stronger magnetic interactions than a d{sup 10}. • Structural distortions weaken the overall Os{sup 5+}-Os{sup 5+} magnetic interactions.

  6. Inner conductor of the magnetic double-horn for the neutrino oscillation experiment with BEBC

    CERN Multimedia

    CERN PhotoLab

    1982-01-01

    In 1980 renewed interest arose in probing for neutrino non-zero masses and associated neutrino oscillations. Low-energy muon-neutrino beams (produced with a proton beam from the PS) were directed towards the SPS neutrino detectors, BEBC, WA1 and WA18 (Annual Report 1982, p.43, Fig.13). Experiments PS169 (WA1) and PS181 (WA18) were "disappearence" experiments and used a "bare" production target, whereas experiment PS180 (BEBC), looked for electron-neutrino "appearence" and used a horn-focused beam. The manufacture of the inner conductor of the double-horn (a particular breed of current-sheet lens) required exceedingly delicate machining. For further pictures see 8304055 and Annual Report 1982, p.137; and p.43 for a description of the experiments.

  7. Tilted magnetic field quantum magnetotransport in the double quantum well with a sizable bulk g-factor: InxGa1-xAs/GaAs

    NARCIS (Netherlands)

    Yakunin, M.V.; Galistu, G.; de Visser, A.

    2008-01-01

    Rich patterns of transformations in the structure of quantum Hall (QH) effect and magnetoresistivity under tilted magnetic fields were obtained in the InxGa1-xAs/GaAs double quantum well at mK temperatures. Local features correspond to the calculated intersections of Landau levels from different

  8. Magnetic nanocomposites with drug-intercalated layered double hydroxide shell supported on commercial magnetite and laboratory-made magnesium ferrite core materials

    Energy Technology Data Exchange (ETDEWEB)

    Ay, Ahmet Nedim, E-mail: ay@hacettepe.edu.tr; Konuk, Deniz; Zuemreoglu-Karan, Birguel

    2011-07-20

    Mg-Al-layered double hydroxide intercalated with a model drug, salicylate, was deposited on laboratory-made magnesium ferrite and commercial magnetite nanoparticles. The obtained core-shell nanocomposites have been characterized by a variety of methods. The combined information from X-ray diffraction patterns, electron diffraction patterns, FTIR spectra, X-ray photoelectron spectra, electron microscopy images, thermogravimetric analysis and microchemical analysis has indicated a similar nature and composition for the two samples. Magnetic measurements have revealed that although the inherent magnetization of magnetite was significantly higher, the nanocomposites displayed nearly similar magnetic properties.

  9. Breast magnetic resonance imaging significance for breast cancer diagnostic in women with genetic predisposition and a strong family history

    Directory of Open Access Journals (Sweden)

    M. S. Karpova

    2013-01-01

    Full Text Available Screening of breast cancer with mammography recommended to women over 40 has been shown to decrease breast cancer mortality. But mam- mography has much lower accuracy in young women with BRCA1/2 mutations and women with a strong family history. Therefore new screening methods in young high-risk women are necessary to detect early-stage cancer.

  10. Effectively doubling the magnetic field in spin-1/2-spin-1, HSQC, HDQC, coupled HSQC, and coupled HDQC in solution NMR.

    Science.gov (United States)

    Shekar, S Chandra; Backer, Jonathan M; Girvin, Mark E

    2008-05-14

    Pulse sequences for spin-1/2-spin-1 pair heteronuclear single quantum correlation (HSQC), heteronuclear double quantum correlation (HDQC), and coupled-HSQC, and coupled-HDQC NMR spectroscopies are outlined, and experimental realization for a (13)C-(2)H pair is demonstrated in solution state. In both the coupled versions, conditions for generation of in-phase and antiphase multiplets in either dimension are arrived at. The patterns and the intensity ratios are explained. The double quantum (2Q) experiments confirm doubling of both the shift frequency and the splitting due to coupling (to spin 1/2) of the 2Q coherence emanating from spin 1. The frequency doubling is equivalent to the corresponding single quantum (1Q) coherence at double the magnetic field strength. The coupling doubling, however, is independent of the magnetic field strength and a signature feature of the 2Q coherence. The ramification of the relative relaxation rates of 1Q and 2Q coherences is discussed.

  11. Effectively doubling the magnetic field in spin-1∕2–spin-1, HSQC, HDQC, coupled HSQC, and coupled HDQC in solution NMR

    Science.gov (United States)

    Chandra Shekar, S.; Backer, Jonathan M.; Girvin, Mark E.

    2008-01-01

    Pulse sequences for spin-1∕2–spin-1 pair heteronuclear single quantum correlation (HSQC), heteronuclear double quantum correlation (HDQC), and coupled-HSQC, and coupled-HDQC NMR spectroscopies are outlined, and experimental realization for a 13C–2H pair is demonstrated in solution state. In both the coupled versions, conditions for generation of in-phase and antiphase multiplets in either dimension are arrived at. The patterns and the intensity ratios are explained. The double quantum (2Q) experiments confirm doubling of both the shift frequency and the splitting due to coupling (to spin 1∕2) of the 2Q coherence emanating from spin 1. The frequency doubling is equivalent to the corresponding single quantum (1Q) coherence at double the magnetic field strength. The coupling doubling, however, is independent of the magnetic field strength and a signature feature of the 2Q coherence. The ramification of the relative relaxation rates of 1Q and 2Q coherences is discussed. PMID:18532820

  12. The magnetic properties of $^{\\rm 177}$Hf and $^{\\rm 180}$Hf in the strong coupling deformed model

    OpenAIRE

    Muto, S.; Stone, N. J.; Bingham, C. R.; Stone, J. R.; Walker, P. M.; Audi, G.; Gaulard, C.; Köster, U.; Nikolov, J.; Nishimura, K.; Ohtsubo, T.; Podolyak, Z.; Risegari, L.; Simpson, G. S.; Veskovic, M.

    2014-01-01

    This paper reports NMR measurements of the magnetic dipole moments of two high-K isomers, the 37/2$^-$, 51.4 m, 2740 keV state in $^{\\rm 177}$Hf and the 8$^-$, 5.5 h, 1142 keV state in $^{\\rm 180}$Hf by the method of on-line nuclear orientation. Also included are results on the angular distributions of gamma transitions in the decay of the $^{\\rm 177}$Hf isotope. These yield high precision E2/M1 multipole mixing ratios for transitions in bands built on the 23/2$^+$, 1.1 s, isomer at 1315 keV ...

  13. Skew angle effects in shingled magnetic recording system with double/triple reader head array

    Science.gov (United States)

    Elidrissi, Moulay Rachid; Sann Chan, Kheong; Greaves, Simon; Kanai, Yasushi; Muraoka, Hiroaki

    2014-05-01

    Shingled Magnetic Recording (SMR) is a scheme used to extend the life of the current perpendicular magnetic recording technology. SMR enables writing narrow tracks with a wide writer. Currently, SMR employs a single reader and will suffer inter-track interference (ITI) as the tracks become comparable in width to the reader. ITI can be mitigated by using narrower readers; however, narrower readers suffer from increased reader noise. Another approach to combat ITI is to process 2D readback and use ITI cancellation schemes to retrieve the data track. Multiple readbacks can be obtained either with a single reader and multiple revolutions or with a reader array. The former suffers from increased readback latency. In this work, we focus on the latter. When using a reader array, the skew angle poses major challenges. During writing, there is increased adjacent track erasure, and during readback the effective reader pitch varies and there is an increase in the 2D intersymbol interference caused by the rotated reader profile. In this work, we run micromagnetic simulations at different skew angles to train the grain flipping probability model, and then evaluate raw bit channel error rate performance at skew. In particular, we investigate the performance degradation caused by skewing of the 2 or 3 read head array for various read-head geometries.

  14. B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD -57° 3509

    Science.gov (United States)

    Przybilla, N.; Fossati, L.; Hubrig, S.; Nieva, M.-F.; Järvinen, S. P.; Castro, N.; Schöller, M.; Ilyin, I.; Butler, K.; Schneider, F. R. N.; Oskinova, L. M.; Morel, T.; Langer, N.; de Koter, A.; BOB Collaboration

    2016-03-01

    Aims: We report the detection of a magnetic field in the helium-strong star CPD -57° 3509 (B2 IV), a member of the Galactic open cluster NGC 3293, and characterise the star's atmospheric and fundamental parameters. Methods: Spectropolarimetric observations with FORS2 and HARPSpol are analysed using two independent approaches to quantify the magnetic field strength. A high-S/N FLAMES/GIRAFFE spectrum is analysed using a hybrid non-LTE model atmosphere technique. Comparison with stellar evolution models constrains the fundamental parameters of the star. Results: We obtain a firm detection of a surface averaged longitudinal magnetic field with a maximum amplitude of about 1 kG. Assuming a dipolar configuration of the magnetic field, this implies a dipolar field strength larger than 3.3 kG. Moreover, the large amplitude and fast variation (within about 1 day) of the longitudinal magnetic field implies that CPD -57° 3509 is spinning very fast despite its apparently slow projected rotational velocity. The star should be able to support a centrifugal magnetosphere, yet the spectrum shows no sign of magnetically confined material; in particular, emission in Hα is not observed. Apparently, the wind is either not strong enough for enough material to accumulate in the magnetosphere to become observable or, alternatively, some leakage process leads to loss of material from the magnetosphere. The quantitative spectroscopic analysis of the star yields an effective temperature and a logarithmic surface gravity of 23 750 ± 250 K and 4.05 ± 0.10, respectively, and a surface helium fraction of 0.28 ± 0.02 by number. The surface abundances of C, N, O, Ne, S, and Ar are compatible with the cosmic abundance standard, whereas Mg, Al, Si, and Fe are depleted by about a factor of 2. This abundance pattern can be understood as the consequence of a fractionated stellar wind. CPD -57° 3509 is one of the most evolved He-strong stars known with an independent age constraint due to its

  15. An ionization pressure gauge with LaB6 emitter for long-term operation in strong magnetic fields

    Science.gov (United States)

    Wenzel, U.; Pedersen, T. S.; Marquardt, M.; Singer, M.

    2018-03-01

    We report here on a potentially significant improvement in the design of neutral pressure gauges of the so-called ASDEX-type which were first used in the Axially Symmetric Divertor EXperiment (ASDEX). Such gauges are considered state-of-the-art and are in wide use in fusion experiments, but they nonetheless suffer from a relatively high failure rate when operated at high magnetic field strengths for long times. This is therefore a significant concern for long-pulse, high-field experiments such as Wendelstein 7-X (W7-X) and ITER. The new design is much more robust. The improvement is to use a LaB6 crystal instead of a tungsten wire as the thermionic emitter of electrons in the gauge. Such a LaB6 prototype gauge was successfully operated for a total of 60 h in B = 3.1 T, confirming the significantly improved robustness of the new design and qualifying it for near-term operation in W7-X. With the LaB6 crystal, an order of magnitude reduction in heating current is achieved, relative to the tungsten filament based gauges, from 15-20 A to 1-2 A. This reduces the Lorenz forces and the heating power by an order of magnitude also and is presumably the reason for the much improved robustness. The new gauge design, test environment setup at the superconducting magnet, and results from test operation are described.

  16. Study of Muon Triggers and Momentum Reconstruction in a Strong Magnetic Field for a Muon Detector at LHC

    CERN Multimedia

    2002-01-01

    % RD-5 \\\\ \\\\ A small fraction of a muon detector for possible use in an LHC experiment is installed in the SPS H2 beam. It consists of a 3T superconducting solenoid enclosing a 10$\\lambda$ deep calorimeter made of stainless steel plates interleaved with Honeycomb strip chambers. Behind this magnet are located 3 muon stations for triggering and momentum measurement. These stations, consisting of UA1 muon chambers backed up with Resistive Plate Chambers (RPC), are inserted in a 1.5~T absorber magnet of 20$\\lambda$ total thickness, station 2 being located after 10$\\lambda$. \\\\ \\\\During the data taking period (1991-1994) 10$^{7}$ muon and hadron events were recorded. Beams of negative muons and pions and of positive muons and hadrons $ (\\pi^+, K ^+ $ and protons) were used with a momentum ranging from 10~to~300~GeV/c. \\\\ \\\\The RD-5 program has covered several topics related to muon detection at LHC: \\\\ \\\\\\begin{description} \\item[(i)]~~study of the behaviour of muons from hadron punchthrough and decays, and also ...

  17. Strong static magnetic fields of NMR: Do they affect tissue perfusion. Beeinflussen starke statische Magnetfelder in der NMR-Tomographie die Gewebedurchblutung

    Energy Technology Data Exchange (ETDEWEB)

    Stick, C.; Hinkelmann, K. (Kiel Univ. (Germany, F.R.). Inst. fuer Angewandte Physiologie und Medizinische Klimatologie); Eggert, P. (Kiel Univ. (Germany, F.R.). Abt. Allgemeine Paediatrie); Wendhausen, H. (Kiel Univ. (Germany, F.R.). Abt. Radiologie)

    1991-03-01

    Findings obtained in humans and test animals raised the question whether strong static magnetic fields as used in NMR-tomography may affect tissue perfusion. In two test series including 20 subjects, each skin blood flow at the thumb was determined by heat clearance, and forearm blood flow was measured by venous occlusion plethysmography. For comparative purposes, measurements were carried out bilaterally at both extremities. The experiments consisted of three sections that lasted 10 min each. During the second section the thumb or the forearm were unilaterally exposed to magnetic fields of 0,9 to 1 T and 0.4 to 0.5 T, respectively. The results of this section were compared with the values obtained during the experimental sections prior to and after the exposure to the magnetic field. The results were also compared with the blood flow measured at the contralateral extremity. Neither at the skin of the thumb nor at the forearm were there changes in local blood flow attributable to the magnetic fields applied. (orig.).

  18. Thickness Dependence of Magnetic Relaxation and E-J Characteristics in Superconducting (Gd-Y)-Ba-Cu-O Films with Strong Vortex Pinning

    Energy Technology Data Exchange (ETDEWEB)

    Polat, Ozgur [ORNL; Sinclair IV, John W [ORNL; Zuev, Yuri L [ORNL; Thompson, James R [ORNL; Christen, David K [ORNL; Cook, Sylvester W [ORNL; Kumar, Dhananjay [ORNL; Chen, Y [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2011-01-01

    The dependence of the critical current density Jc on temperature, magnetic field, and film thickness has been investigated in (Gd-Y)BaCu-oxide materials of 0.7, 1.4, and 2.8 m thickness. Generally, the Jc decreases with film thickness at investigated temperatures and magnetic fields. The nature and strength of the pinning centers for vortices have been identified through angular and temperature measurements, respectively. These films do not exhibit c-axis correlated vortex pinning, but do have correlated defects oriented near the ab-planes. For all film thicknesses studied, strong pinning dominates at most temperatures. The vortex dynamics were investigated through magnetic relaxation studies in the temperature range of 5 77 K in 1 T and 3 T applied magnetic fields, H || surface-normal. The creep rate S is thickness dependent at high temperatures, implying that the pinning energy is also thickness dependent. Maley analyses of the relaxation data show an inverse power law variation for the effective pinning energy Ueff ~ (J0/J) . Finally, the electric field-current density (E-J) characteristics were determined over a wide range of dissipation by combining experimental results from transport, swept field magnetometry (VSM), and Superconducting Quantum Interference Device (SQUID) magnetometry. We develop a self-consistent model of the combined experimental results, leading to an estimation of the critical current density Jc0(T) in the absence of flux creep.

  19. Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy

    Science.gov (United States)

    Mohseni, S. Morteza; Yazdi, H. F.; Hamdi, M.; Brächer, T.; Mohseni, S. Majid

    2018-03-01

    Current induced spin wave excitations in spin transfer torque nano-contacts are known as a promising way to generate exchange-dominated spin waves at the nano-scale. It has been shown that when these systems are magnetized in the film plane, broken spatial symmetry of the field around the nano-contact induced by the Oersted field opens the possibility for spin wave mode co-existence including a non-linear self-localized spin-wave bullet and a propagating mode. By means of micromagnetic simulations, here we show that in systems with strong perpendicular magnetic anisotropy (PMA) in the free layer, two propagating spin wave modes with different frequency and spatial distribution can be excited simultaneously. Our results indicate that in-plane magnetized spin transfer nano-contacts in PMA materials do not host a solitonic self-localized spin-wave bullet, which is different from previous studies for systems with in plane magnetic anisotropy. This feature renders them interesting for nano-scale magnonic waveguides and crystals since magnon transport can be configured by tuning the applied current.

  20. Investigations of ultrafast ligand rebinding to heme and heme proteins using temperature and strong magnetic field perturbations

    Science.gov (United States)

    Zhang, Zhenyu

    This thesis is written to summarize investigations of the mechanisms that underlie the kinetics of diatomic ligand rebinding to the iron atom of the heme group, which is chelated inside heme proteins. The family of heme proteins is a major object of studies for several branches of scientific research activity. Understanding the ligand binding mechanisms and pathways is one of the major goals for biophysics. My interests mainly focus on the physics of this ligand binding process. Therefore, to investigate the problem, isolated from the influence of the protein matrix, Fe-protophorphyrin IX is chosen as the prototype system in my studies. Myoglobin, the most extensively and intensively studied protein, is another ideal system that allows coupling the protein polypeptide matrix into the investigation. A technique to synchro-lock two laser pulse trains electronically is applied to our pump-probe spectroscopic studies. Based on this technique, a two color, fs/ps pump-probe system is developed which extends the temporal window for our investigation to 13ns and fills a gap existing in previous pump-probe investigations. In order to apply this newly-developed pump-probe laser system to implement systematic studies on the kinetics of diatomic ligand (NO, CO, O2) rebinding to heme and heme proteins, several experimental setups are utilized. In Chapter 1, the essential background knowledge, which helps to understand the iron-ligand interaction, is briefly described. In Chapter 2, in addition to a description of the preparation protocols of protein samples and details of the method for data analysis, three home-made setups are described, which include: a picosecond laser regenerative amplifier, a pump-probe application along the bore (2-inch in diameter) of a superconducting magnet and a temperature-controllable cryostat for spinning sample cell. Chapter 3 presents high magnetic field studies of several heme-ligand or protein-ligand systems. Pump-probe spectroscopy is used to

  1. Magnetic interactions in rhenium-containing rare earth double perovskites Sr_2LnReO_6 (Ln=rare earths)

    International Nuclear Information System (INIS)

    Nishiyama, Atsuhide; Doi, Yoshihiro; Hinatsu, Yukio

    2017-01-01

    The perovskite-type compounds containing both rare earth and rhenium Sr_2LnReO_6 (Ln=Y, Tb-Lu) have been prepared. Powder X-ray diffraction measurements and Rietveld analysis show that Ln"3"+ and Re"5"+ ions are structurally ordered at the B site of the perovskite SrBO_3. Magnetic anomalies are found in their magnetic susceptibility and specific heat measurements at 2.6–20 K for Ln=Y, Tb, Dy, Yb, Lu compounds. They are due to magnetic interactions between Re"5"+ ions. The results of the magnetic hysteresis and remnant magnetization measurements for Sr_2YReO_6 and Sr_2LuReO_6 indicate that the antiferromagnetic interactions between Re"5"+ ions below transition temperatures have a weak ferromagnetic component. The analysis of the magnetic specific heat data for Sr_2YbReO_6 shows that both the Yb"3"+ and Re"5"+ ions magnetically order at 20 K. For the case of Sr_2DyReO_6, magnetic ordering of the Re"5"+ moments occurs at 93 K, and with decreasing temperature, the moments of Dy"3"+ ferromagnetically order at 5 K from the measurements of magnetic susceptibility and specific heat. - Graphical abstract: Crystal structure of double perovskite Sr_2LnReO_6. Red and black lines show cubic and monoclinic unit cells, respectively. - Highlights: • Double perovskites Sr_2LnReO_6 (Ln=rare earths) were prepared. • They show an antiferromagnetic transition at 2.6–20 K. • In Sr_2DyReO_6, Dy and Re moments magnetically order at 5 and 93 K, respectively.

  2. Extreme enhancement of blocking temperature by strong magnetic dipoles interaction of α-Fe nanoparticle-based high-density agglomerate

    International Nuclear Information System (INIS)

    Kura, H; Takahashi, M; Ogawa, T

    2011-01-01

    High-volume fraction α-Fe nanoparticle (NP) agglomerates were prepared using chemically synthesized NPs. In the agglomerate, NPs are separated by surfactant and NP superlattice with a hexagonal close-packed structure is locally realized. Volume fractions of NPs at 20% and 42% were obtained in agglomerates consisting of 2.9 nm and 8.2 nm diameter NPs, respectively. The high saturation magnetization of α-Fe NPs and high volume fraction of NPs in the agglomerate provide strong magnetic dipole-dipole interaction. The interaction energy of the agglomerate became much larger than the anisotropic energy of individual NPs. As a result, the blocking temperature of the 8.2 nm NP agglomerate was significantly enhanced from 52.2 K to around 500 K. (fast track communication)

  3. Quantum fluid dynamics based current-density functional study of a helium atom in a strong time-dependent magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Vikas [Quantum Chemistry Group, Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, 160014 Chandigrah (India)

    2011-02-15

    Evolution of the helium atom in a strong time-dependent (TD) magnetic field (B) of strength up to 10{sup 11} G is investigated through a quantum fluid dynamics (QFD) based current-density functional theory (CDFT). The TD-QFD-CDFT computations are performed through numerical solution of a single generalized nonlinear Schroedinger equation employing vector exchange-correlation potentials and scalar exchange-correlation density functionals that depend both on the electronic charge-density and the current-density. The results are compared with that obtained from a B-TD-QFD-DFT approach (based on conventional TD-DFT) under similar numerical constraints but employing only scalar exchange-correlation potential dependent on electronic charge-density only. The B-TD-QFD-DFT approach, at a particular TD magnetic field-strength, yields electronic charge- and current-densities as well as exchange-correlation potential resembling with that obtained from the time-independent studies involving static (time-independent) magnetic fields. However, TD-QFD-CDFT electronic charge- and current-densities along with the exchange-correlation potential and energy differ significantly from that obtained using B-TD-QFD-DFT approach, particularly at field-strengths >10{sup 9} G, representing dynamical effects of a TD field. The work concludes that when a helium atom is subjected to a strong TD magnetic field of order >10{sup 9} G, the conventional TD-DFT based approach differs 'dynamically' from the CDFT based approach under similar computational constraints. (author)

  4. The strongly generalized double difference χ sequence spaces defined by a modulus - doi: 10.4025/actascitechnol.v35i4.16184

    Directory of Open Access Journals (Sweden)

    Subramanian Nagarajan

    2013-10-01

    Full Text Available In this paper we introduce the strongly generalized difference sequence spaces of modulus function and is a non-negative four dimensional matrix of complex numbers and (pi(mn is a sequence of positive real numbers. We also give natural relationship between strongly generalized difference summable sequences with respect of modulus. We examine some topological properties of the above spaces and investigate some inclusion relations between these spaces.  

  5. Investigation of the magnetic properties in double perovskite R2CoMnO6 single crystals (R  =  rare earth: La to Lu).

    Science.gov (United States)

    Kim, M K; Moon, J Y; Choi, H Y; Oh, S H; Lee, N; Choi, Y J

    2015-10-28

    We have successfully synthesized the series of the double-perovskite R2CoMnO6 (R  =  rare earth: La to Lu) single crystals and have investigated their magnetic properties. The ferromagnetic order of Co(2+)/Mn(4+) spins emerges mainly along the c axis. Upon decreasing the size of rare earth ion, the magnetic transition temperature decreases linearly from 204 K for La2CoMnO6 to 48 K for Lu2CoMnO6, along with the enhancement of monoclinic distortion. The temperature and magnetic-field dependences of magnetization reveal the various magnetic characteristics such as the metamagnetic transition in R  =  Eu, the isotropic nature of rare earth moment in R  =  Gd, and the reversal of magnetic anisotropy in R  =  Tb and Dy. Our results offer comprehensive information for understanding the roles of mixed-valent magnetic ions and rare earth magnetic moments on the magnetic properties.

  6. On the impact of the elastic-plastic flow upon the process of destruction of the solenoid in a super strong pulsed magnetic field

    Science.gov (United States)

    Krivosheev, S. I.; Magazinov, S. G.; Alekseev, D. I.

    2018-01-01

    At interaction of super strong magnetic fields with a solenoid material, a specific mode of the material flow forms. To describe this process, magnetohydrodynamic approximation is traditionally used. The formation of plastic shock-waves in material in a rapidly increasing pressure of 100 GPa/μs, can significantly alter the distribution of the physical parameters in the medium and affect the flow modes. In this paper, an analysis of supporting results of numerical simulations in comparison with available experimental data is presented.

  7. Pacemaker reed switch behavior in 0.5, 1.5, and 3.0 Tesla magnetic resonance imaging units: are reed switches always closed in strong magnetic fields?

    Science.gov (United States)

    Luechinger, Roger; Duru, Firat; Zeijlemaker, Volkert A; Scheidegger, Markus B; Boesiger, Peter; Candinas, Reto

    2002-10-01

    MRI is established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. The aim of this study was to investigate the state of a pacemaker reed switch in different orientations and positions in the main magnetic field of 0.5-, 1.5-, and 3.0-T MRI scanners. Reed switches used in current pacemakers and ICDs were tested in 0.5-, 1.5-, and 3.0-T MRI scanners. The closure of isolated reed switches was evaluated for different orientations and positions relative to the main magnetic field. The field strengths to close and open the reed switch and the orientation dependency of the closed state inside the main magnetic field were investigated. The measurements were repeated using two intact pacemakers to evaluate the potential influence of the other magnetic components, like the battery. If the reed switches were oriented parallel to the magnetic fields, they closed at 1.0 +/- 0.2 mT and opened at 0.7 +/- 0.2 mT. Two different reed switch behaviors were observed at different magnetic field strengths. In low magnetic fields ( 200 mT), the reed switches opened in 50% of all tested orientations. No difference between the three scanners could be demonstrated. The reed switches showed the same behavior whether they were isolated or an integral part of the pacemakers. The reed switch in a pacemaker or an ICD does not necessarily remain closed in strong magnetic fields at 0.5, 1.5, or 3.0 T and the state of the reed switch may not be predictable with certainty in clinical situations.

  8. Ionospheric convection response to changes of interplanetary magnetic field B-z component during strong B-y component

    DEFF Research Database (Denmark)

    Huang, C.S.; Murr, D.; Sofko, G.J.

    2000-01-01

    the dawn-dusk meridian plane, which is interpreted as propagation or expansion of newly generated convection cells in the cusp region. Other studies showed that the change in convection pattern in response to IMF reorientations is spatially fixed. In this paper, we investigate the ionospheric convection...... response to IMF Bz changes during strong IMF BZ. On March 23, 1995, B-x was small, B-y was strongly positive (7-11 nT), and the B-z polarity changed several times after 1300 UT. The dayside ionospheric convection is dominated by a large clockwise convection cell. The cell focus (the "eye" of the convection...... pattern) is located in the prenoon sector for northward B-z and in the postnoon sector for southward B-z. It is found that the cell focus shifts from the prenoon sector to the postnoon sector following a southward BL turning and vice versa for a northward B-z turning. However, the motion of the convection...

  9. Polarized neutron reflectometry study on BiFeO3/Co0.9Fe0.1 heterostructures: enhanced magnetization in BiFeO3 and strong magnetic coupling at interface

    Science.gov (United States)

    Wang, Qiang; Gao, Ya; Ramesh, Ramamoorthy; Fitzsimmons, Michael

    2015-03-01

    Polarized neutron reflectometry (PNR) quantified the uncompensated magnetization occurring throughout the thickness of a BiFeO3 (BFO)/ Co0.9Fe0.1 (CoFe) heterostructures. The net uncompensated magnetization (1.0 μB/Fe) within BFO layer is much larger than that which has been theoretically predicted (0.1 μB/Fe) due to the Dzyaloshinskii-Moriya (DM) type interaction. The field dependent study indicates strong interfacial coupling between BFO and CoFe which extends into CoFe layer within about 1 nm interfacial region. The study also suggests the uncompensated magnetization in the BFO layer has relatively small anisotropy.

  10. Structure, magnetism and electronic properties in 3d-5d based double perovskite ([Formula: see text]Y x )2FeIrO6.

    Science.gov (United States)

    Kharkwal, K C; Pramanik, A K

    2017-11-13

    The 3d-5d based double perovskites are of current interest as they provide model systems to study the interplay between electronic correlation (U) and spin-orbit coupling (SOC). Here, we report detailed structural, magnetic and transport properties of doped double perovskite material ([Formula: see text]Y x ) 2 FeIrO 6 with [Formula: see text]. With substitution of Y, the system retains its original crystal structure but structural parameters change with x in nonmonotonic fashion. The magnetization data for Sr 2 FeIrO 6 show antiferromagnetic type magnetic transition around 45 K; however, a close inspection of the data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr 2 FeIrO 6 shows an insulating behavior over the whole temperature range, which nevertheless does not change with Y substitution. The nature of charge conduction is found to follow thermally activated Mott's variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in ([Formula: see text]Y x ) 2 FeIrO 6 is observed to reverse with [Formula: see text], which is believed to arise due to a change in the transition metal ionic state.

  11. Structure, magnetism and electronic properties in 3d-5d based double perovskite ({Sr_{1-x}} Y x )2FeIrO6

    Science.gov (United States)

    Kharkwal, K. C.; Pramanik, A. K.

    2017-12-01

    The 3d-5d based double perovskites are of current interest as they provide model systems to study the interplay between electronic correlation (U) and spin-orbit coupling (SOC). Here, we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr1-x Y x )2FeIrO6 with x ≤slant 0.2 . With substitution of Y, the system retains its original crystal structure but structural parameters change with x in nonmonotonic fashion. The magnetization data for Sr2FeIrO6 show antiferromagnetic type magnetic transition around 45 K however, a close inspection of the data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr2FeIrO6 shows an insulating behavior over the whole temperature range, which nevertheless does not change with Y substitution. The nature of charge conduction is found to follow thermally activated Mott’s variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr1-x Y x )2FeIrO6 is observed to reverse with x > 0.1 , which is believed to arise due to a change in the transition metal ionic state.

  12. Structure, magnetism and electronic properties in 3d-5d based double perovskite (Sr1-xYx)2FeIrO6.

    Science.gov (United States)

    Kharkwal, Kishor Chandra; Pramanik, Ashim Kumar

    2017-10-17

    The 3$d$-5$d$ based double perovskites are of current interest as they provide model system to study the interplay between electronic correlation ($U$) and spin-orbit coupling (SOC). Here we report detailed structural, magnetic and transport properties of doped double perovskite material (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ with $x$ $\\leq$ 0.2. With substitution of Y, system retains its original crystal structure but structural parameters modify with $x$ in nonmonotonic fashion. The magnetization data for Sr$_2$FeIrO$_6$ show antiferromagnetic type magnetic transition around 45 K, however, a close inspection in data indicates a weak magnetic phase transition around 120 K. No change of structural symmetry has been observed down to low temperature, although the lattice parameters show sudden changes around the magnetic transitions. Sr$_2$FeIrO$_6$ shows an insulating behavior over the whole temperature range which yet does not change with Y substitution. Nature of charge conduction is found to follow thermally activated Mott's variable range hopping and power law behavior for parent and doped samples, respectively. Interestingly, evolution of structural, magnetic and transport behavior in (Sr$_{1-x}$Y$_x$)$_2$FeIrO$_6$ is observed to reverse with $x$ $>$ 0.1 which is believed to arise due to change in transition metal ionic state. © 2017 IOP Publishing Ltd.

  13. Improved background rejection in neutrinoless double beta decay experiments using a magnetic field in a high pressure xenon TPC

    Science.gov (United States)

    Renner, J.; Cervera, A.; Hernando, J. A.; Imzaylov, A.; Monrabal, F.; Muñoz, J.; Nygren, D.; Gomez-Cadenas, J. J.

    2015-12-01

    We demonstrate that the application of an external magnetic field could lead to an improved background rejection in neutrinoless double-beta (0νββ) decay experiments using a high-pressure xenon (HPXe) TPC. HPXe chambers are capable of imaging electron tracks, a feature that enhances the separation between signal events (the two electrons emitted in the 0νββ decay of 136Xe) and background events, arising chiefly from single electrons of kinetic energy compatible with the end-point of the 0νββ decay (0Qββ). Applying an external magnetic field of sufficiently high intensity (in the range of 0.5-1 Tesla for operating pressures in the range of 5-15 atmospheres) causes the electrons to produce helical tracks. Assuming the tracks can be properly reconstructed, the sign of the curvature can be determined at several points along these tracks, and such information can be used to separate signal (0νββ) events containing two electrons producing a track with two different directions of curvature from background (single-electron) events producing a track that should spiral in a single direction. Due to electron multiple scattering, this strategy is not perfectly efficient on an event-by-event basis, but a statistical estimator can be constructed which can be used to reject background events by one order of magnitude at a moderate cost (about 30%) in signal efficiency. Combining this estimator with the excellent energy resolution and topological signature identification characteristic of the HPXe TPC, it is possible to reach a background rate of less than one count per ton-year of exposure. Such a low background rate is an essential feature of the next generation of 0νββ experiments, aiming to fully explore the inverse hierarchy of neutrino masses.

  14. Diacylhydrazone-assembled {Ln11} nanoclusters featuring a "double-boats conformation" topology: synthesis, structures and magnetism.

    Science.gov (United States)

    Wang, Kai; Chen, Zi-Lu; Zou, Hua-Hong; Zhang, Shu-Hua; Li, Yan; Zhang, Xiu-Qing; Sun, Wei-Yin; Liang, Fu-Pei

    2018-02-13

    A family of novel Ln nanoclusters, namely, [Ln 11 (ovpho) 4 (μ-CH 3 O) 2 (μ-H 2 O) 2 (μ 3 -OH) 6 (CH 3 OH) 4 (H 2 O) 2 (NO 3 ) 8 ](OH)·xH 2 O·yCH 3 OH [Ln = Gd (1), x = 1, y = 3; Ln = Tb (2), x = 1, y = 3; Ln = Dy (3), x = 0, y = 3], was obtained via solvothermal reactions of Ln(NO 3 ) 3 with a diacylhydrazone ligand N,N'-bis(o-vanillidene)pyridine-2,6-dicarbohydrazide N-oxide (H 4 ovpho). Their isostructural molecular structures are composed of two crystallographically symmetric {Ln 6 } rings sharing a Ln 3+ ion, and display an unprecedented "double boat conformation" topology that, to our knowledge, has not yet been reported. O phenol , O enol and O oxynitride from ovpho 4- ligands, as well as O methanol , O water and O hydroxyl help to bridge the Ln 3+ ions. The structural variation between these {Ln 11 } clusters and a previously reported {Gd 18 } nanowheel, both of which are assembled by H 4 ovpho under the same synthetic method and reaction conditions, is caused only by changing the anions of Ln salts. Magnetic investigations revealed a large magnetocaloric effect (MCE) of 1, whose maximum -ΔS m value reaches 30.1 J kg -1 K -1 for ΔH = 50 kOe at 2.0 K. Additionally, it was found that 3 shows single-molecule magnets (SMMs) behavior, with an approximated energy barrier U eff = 6.13 K and pre-exponential factor τ 0 = 1.70 × 10 -6 s.

  15. La2MnVO6 Double Perovskite: A Structural, Magnetic and X-Ray Absorption Investigation

    International Nuclear Information System (INIS)

    Mandal, T.; Croft, M.; Hadermann, J.; Van Tendeloo, G.; Stephens, P.; Greenblatt, M.

    2009-01-01

    The synthesis, electron diffraction (ED), synchrotron X-ray and neutron structure, X-ray absorption spectroscopy (XAS) and magnetic property studies of La2MnVO6 double perovskite are described. Analysis of the synchrotron powder X-ray diffraction data for La2MnVO6 indicates a disordered arrangement of Mn and V at the B-site of the perovskite structure. Absence of super-lattice reflections in the ED patterns for La2MnVO6 supports the disordered cation arrangement. Room temperature time-of-flight (TOF) neutron powder diffraction (NPD) data show no evidence of cation ordering, in corroboration with the ED and synchrotron studies (orthorhombic Pnma, a = 5.6097(3), b = 7.8837(5) and c = 5.5668(3); 295 K, NPD). A comparison of XAS analyses of La2TVO6 with T = Ni and Co shows T2+ formal oxidation state while the T = Mn material evidences a Mn3+ admixture into a dominantly Mn2+ ground state. V-K edge measurements manifest a mirror image behavior with a V4+ state for T = Ni and Co with a V3+ admixture arising in the T = Mn material. The magnetic susceptibility data for La2MnVO6 show ferromagnetic correlations; the observed effective moment, μeff (5.72 μB) is much smaller than the calculated moment (6.16 μμB) based on the spin-only formula for Mn2+ (d5, HS)/V4+ (d1), supportive of the partly oxidized Mn and reduced V scenario (Mn3+/V3+).

  16. The electronic, magnetic and optical properties of ZnO doped with doubles impurities (Cr, Fe): An LDA-SIC and Monte Carlo study

    Energy Technology Data Exchange (ETDEWEB)

    Salmani, El Mehdi, E-mail: elmehdisalmani@gmail.com [LMPHE, Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Laghrissi, Ayoub; Lamouri, Rachida; Ez-Zahraouy, Hamid [LMPHE, Faculté des Sciences, Université Mohammed V, Rabat (Morocco); Benyoussef, Abdelilah [Institute for Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Académie Hassan II des Sciences et Techniques, Rabat (Morocco)

    2017-01-15

    Electronic structure, magnetic and optical properties of ZnO doped with single and double impurities Zn{sub 1−x}Cr{sub x}O, Zn{sub 1−x}Fe{sub x}O, and Zn{sub 1−2x}Cr{sub x}Fe{sub x}O (x=0.03 and 0.06) are investigated using first-principles calculations. Based on the Korringa–Kohn–Rostoker method combined with the coherent potential approximation, we investigated the half-metallic ferromagnetic behavior of doubles impurities (Cr, Fe) doped ZnO. To support our results, we apply the self-interaction-corrected local density approximation (SIC-LDA) to study the electronic structure, optical and magnetic properties of Co-doped ZnO with doubles impurities (Cr, Fe) showing that the half-metallic ferromagnetic state still persists. The stability of the ferromagnetic state compared with the spin-glass state is investigated by comparing their total energies. The exchange interactions obtained from first principle calculations and used in a classical Ising model by a Monte Carlo approach resulted in ferromagnetic states with high Neel temperature. - Highlights: • The electronic structure calculations for ZnO doped with doubles impurities (Cr, Fe) have been discussed. • The half-metallic aspect was proven to take place for doubles impurities (Cr, Fe) codoped ZnO. • The doubles impurities (Cr, Fe)impurities are shown to introduce the necessary magnetic moment that makes ZnO good candidates for spintronic applications.

  17. Scattering of the transverse magnetic modes from an abruptly ended strongly asymmetrical slab waveguide by an accelerated integral equation technique.

    Science.gov (United States)

    Manenkov, A B; Latsas, G P; Tigelis, L G

    2001-12-01

    We study the problem of the scattering of the first TM guided mode from an abruptly ended strongly asymmetrical slab waveguide by an improved iteration technique, which is based on the integral equation method with "accelerating" parameters. We demonstrate that the values of these parameters are related to the variational principle, and we save approximately 1-2 iterations compared with the case in which these parameters are not employed. The tangential electric-field distribution on the terminal plane, the reflection coefficient of the first TM guided mode, and the far-field radiation pattern are computed. Furthermore, a simple technique based on the Aitken extrapolation procedure is employed for faster computation of the higher-order solutions of the reflection coefficient. Numerical results are presented for several cases of abruptly ended waveguides, including systems with variational profile, while special attention is given to the far-field radiation pattern rotation and its explanation.

  18. Strong spin-photon coupling in silicon.

    Science.gov (United States)

    Samkharadze, N; Zheng, G; Kalhor, N; Brousse, D; Sammak, A; Mendes, U C; Blais, A; Scappucci, G; Vandersypen, L M K

    2018-03-09

    Long coherence times of single spins in silicon quantum dots make these systems highly attractive for quantum computation, but how to scale up spin qubit systems remains an open question. As a first step to address this issue, we demonstrate the strong coupling of a single electron spin and a single microwave photon. The electron spin is trapped in a silicon double quantum dot, and the microwave photon is stored in an on-chip high-impedance superconducting resonator. The electric field component of the cavity photon couples directly to the charge dipole of the electron in the double dot, and indirectly to the electron spin, through a strong local magnetic field gradient from a nearby micromagnet. Our results provide a route to realizing large networks of quantum dot-based spin qubit registers. Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  19. Radio emission from the X-ray pulsar Her X-1: a jet launched by a strong magnetic field neutron star?

    Science.gov (United States)

    van den Eijnden, J.; Degenaar, N.; Russell, T. D.; Miller-Jones, J. C. A.; Wijnands, R.; Miller, J. M.; King, A. L.; Rupen, M. P.

    2018-01-01

    Her X-1 is an accreting neutron star (NS) in an intermediate-mass X-ray binary. Like low-mass X-ray binaries (LMXBs), it accretes via Roche lobe overflow, but similar to many high-mass X-ray binaries containing a NS; Her X-1 has a strong magnetic field and slow spin. Here, we present the discovery of radio emission from Her X-1 with the Very Large Array. During the radio observation, the central X-ray source was partially obscured by a warped disc. We measure a radio flux density of 38.7 ± 4.8 μJy at 9 GHz but cannot constrain the spectral shape. We discuss possible origins of the radio emission, and conclude that coherent emission, a stellar wind, shocks and a propeller outflow are all unlikely explanations. A jet, as seen in LMXBs, is consistent with the observed radio properties. We consider the implications of the presence of a jet in Her X-1 on jet formation mechanisms and on the launching of jets by NSs with strong magnetic fields.

  20. Design features of a planar hybrid/permanent magnet strong-focusing undulator for Free Electron Laser (FEL) and Synchrotron Radiation (SR) applications

    Science.gov (United States)

    Tatchyn, Roman

    1997-05-01

    Insertion devices for Angstrom-wavelength Free Electron Laser (FEL) amplifiers driven by multi-GeV electron beams generally require distributed focusing substantially stronger than their natural focusing fields(C. Pellegrini, "A 4 to 0.1 nm FEL Based on the SLAC Linac," in Proc. Workshop on 4th Generation Light Sources, M.Cornacchia and H. Winick, eds., SSRL, Feb. 1992. p. 364 ff.)(R. Tatchyn, "Optimal Insertion Device Parameters for SASE FEL Operation," ibid., p. 605 ff.). Over the last several years a wide variety of focusing schemes and configurations have been proposed for undulators of this class, ranging from conventional current-driven quadrupoles external to the undulator magnets(R. Tatchyn, R. Boyce, K. Halbach, H.-D. Nuhn, J. Seeman, H. Winick, and C. Pellegrini, "Design Considerations for a 60 Meter Pure Permanent Magnet Undulator for the SLAC Linac Coherent Light Source (LCLS)," in Proceedings of the 1993 Particle Accelerator Conference, IEEE Catalog No. 93CH3279-7, 1608(1993).) to permanent magnet (PM) lattices inserted into the insertion device gap(R. Tatchyn, "Selected applications of planar permanent magnet multipoles in FEL insertion device design," NIM A341, 449(1994).)(A. A. Varfolomeev, A. H. Hairetdinov, "Advanced hybrid undulator schemes providing enhanced transverse e-beam focusing," ibid., p. 462.)(G. Travish, J. Rosenzweig, "Strong sextupole focussing in planar undulators," NIM A345, 585(1994).). In this paper we present design studies of a flexible hybrid/PM undulator with superimposed planar PM focusing proposed for a 1.5 Angstrom Linac Coherent Light Source (LCLS) undulator(S. Caspi, R. Schlueter, R. Tatchyn, "High-Field Strong-Focusing Undulator Designs for X-Ray Linac Coherent Light Source (LCLS) Applications," Proc. IEEE PAC95, Dallas, TX, May 1-5, 1995, SLAC-PUB-95-6885.)(R. Tatchyn, "Permanent Magnet Edge-Field Quadrupole," US Patent 5,596,304.) driven by an electron beam with a 1 mm-mr normalized emittance(R. Tatchyn et al, NIM A