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Sample records for magnetized pure electron

  1. Nanosized graphene crystallite induced strong magnetism in pure carbon films.

    Science.gov (United States)

    Wang, Chao; Zhang, Xi; Diao, Dongfeng

    2015-03-14

    We report strong magnetism in pure carbon films grown by electron irradiation assisted physical vapor deposition in electron cyclotron resonance plasma. The development of graphene nanocrystallites in the amorphous film matrix, and the dependence of the magnetic behavior on amorphous, nanocrystallite and graphite-like structures were investigated. Results were that the amorphous structure shows weak paramagnetism, graphene nanocrystallites lead to strong magnetization, and graphite-like structures corresponded with a lower magnetization. At a room temperature of 300 K, the highest saturation magnetization of 0.37 emu g(-1) was found in the nanosized graphene nanocrystallite structure. The origin of strong magnetism in nanocrystallites was ascribed to the spin magnetic moment at the graphene layer edges.

  2. Hydrogen-bond-dynamics-based switching of conductivity and magnetism: a phase transition caused by deuterium and electron transfer in a hydrogen-bonded purely organic conductor crystal.

    Science.gov (United States)

    Ueda, Akira; Yamada, Shota; Isono, Takayuki; Kamo, Hiromichi; Nakao, Akiko; Kumai, Reiji; Nakao, Hironori; Murakami, Youichi; Yamamoto, Kaoru; Nishio, Yutaka; Mori, Hatsumi

    2014-08-27

    A hydrogen bond (H-bond) is one of the most fundamental and important noncovalent interactions in chemistry, biology, physics, and all other molecular sciences. Especially, the dynamics of a proton or a hydrogen atom in the H-bond has attracted increasing attention, because it plays a crucial role in (bio)chemical reactions and some physical properties, such as dielectricity and proton conductivity. Here we report unprecedented H-bond-dynamics-based switching of electrical conductivity and magnetism in a H-bonded purely organic conductor crystal, κ-D3(Cat-EDT-TTF)2 (abbreviated as κ-D). This novel crystal κ-D, a deuterated analogue of κ-H3(Cat-EDT-TTF)2 (abbreviated as κ-H), is composed only of a H-bonded molecular unit, in which two crystallographically equivalent catechol-fused ethylenedithiotetrathiafulvalene (Cat-EDT-TTF) skeletons with a +0.5 charge are linked by a symmetric anionic [O···D···O](-1)-type strong H-bond. Although the deuterated and parent hydrogen systems, κ-D and κ-H, are isostructural paramagnetic semiconductors with a dimer-Mott-type electronic structure at room temperature (space group: C2/c), only κ-D undergoes a phase transition at 185 K, to change to a nonmagnetic insulator with a charge-ordered electronic structure (space group: P1). The X-ray crystal structure analysis demonstrates that this dramatic switching of the electronic structure and physical properties originates from deuterium transfer or displacement within the H-bond accompanied by electron transfer between the Cat-EDT-TTF π-systems, proving that the H-bonded deuterium dynamics and the conducting TTF π-electron are cooperatively coupled. Furthermore, the reason why this unique phase transition occurs only in κ-D is qualitatively discussed in terms of the H/D isotope effect on the H-bond geometry and potential energy curve.

  3. Magnetization oscillations and waves driven by pure spin currents

    Science.gov (United States)

    Demidov, V. E.; Urazhdin, S.; de Loubens, G.; Klein, O.; Cros, V.; Anane, A.; Demokritov, S. O.

    2017-02-01

    Recent advances in the studies of pure spin currents-flows of angular momentum (spin) not accompanied by the electric currents-have opened new horizons for the emerging technologies based on the electron's spin degree of freedom, such as spintronics and magnonics. The main advantage of pure spin current, as compared to the spin-polarized electric current, is the possibility to exert spin transfer torque on the magnetization in thin magnetic films without the electrical current flow through the material. In addition to minimizing Joule heating and electromigration effects, this enables the implementation of spin torque devices based on the low-loss insulating magnetic materials, and offers an unprecedented geometric flexibility. Here we review the recent experimental achievements in investigations of magnetization oscillations excited by pure spin currents in different nanomagnetic systems based on metallic and insulating magnetic materials. We discuss the spectral properties of spin-current nano-oscillators, and relate them to the spatial characteristics of the excited dynamic magnetic modes determined by the spatially-resolved measurements. We also show that these systems support locking of the oscillations to external microwave signals, as well as their mutual synchronization, and can be used as efficient nanoscale sources of propagating spin waves.

  4. Fluid echoes in a pure electron plasma.

    Science.gov (United States)

    Yu, J H; O'Neil, T M; Driscoll, C F

    2005-01-21

    Experimental observations of diocotron wave echoes on a magnetized electron column are reported, representing Kelvin wave echoes on a rotating near-ideal fluid. The echoes occur by reversal of an inviscid wave damping process, and the phase-space mixing and unmixing are directly imaged. The basic echo characteristics agree with a simple nonlinear ballistic theory. At late times, the echo is degraded, and the maximal observed echo times agree with a theory of electron-electron collisions acting on separately evolving velocity classes.

  5. Anomalous rectification in a purely electronic memristor

    Science.gov (United States)

    Wang, Jingrui; Pan, Ruobing; Cao, Hongtao; Wang, Yang; Liang, Lingyan; Zhang, Hongliang; Gao, Junhua; Zhuge, Fei

    2016-10-01

    An anomalous rectification was observed in a purely electronic memristive device Ti/ZnO/Pt. It could be due to (1) an Ohmic or quasi-Ohmic contact at the ZnO/Pt interface and (2) a Schottky contact at the Ti/ZnO interface. The Ohmic contact originates from the reduction of ZnO occurring in the whole film instead of only at the Ti/ZnO interface. The Schottky contact may come from moisture adsorbed in the nanoporous ZnO. The conduction in the electroformed device is controlled by the carrier trapping/detrapping of the trap sites, inducing a poor rectification and high nonlinearity. Furthermore, a complementary resistive switching was achieved.

  6. Synaptic devices based on purely electronic memristors

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Ruobing [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Institute of Materials Science, School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China); Li, Jun; Zhuge, Fei, E-mail: zhugefei@nimte.ac.cn, E-mail: h-cao@nimte.ac.cn; Zhu, Liqiang; Liang, Lingyan; Zhang, Hongliang; Gao, Junhua; Cao, Hongtao, E-mail: zhugefei@nimte.ac.cn, E-mail: h-cao@nimte.ac.cn; Fu, Bing; Li, Kang [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2016-01-04

    Memristive devices have been widely employed to emulate biological synaptic behavior. In these cases, the memristive switching generally originates from electrical field induced ion migration or Joule heating induced phase change. In this letter, the Ti/ZnO/Pt structure was found to show memristive switching ascribed to a carrier trapping/detrapping of the trap sites (e.g., oxygen vacancies or zinc interstitials) in ZnO. The carrier trapping/detrapping level can be controllably adjusted by regulating the current compliance level or voltage amplitude. Multi-level conductance states can, therefore, be realized in such memristive device. The spike-timing-dependent plasticity, an important Hebbian learning rule, has been implemented in this type of synaptic device. Compared with filamentary-type memristive devices, purely electronic memristors have potential to reduce their energy consumption and work more stably and reliably, since no structural distortion occurs.

  7. Electron Acoustic Waves in Pure Ion Plasmas

    Science.gov (United States)

    Anderegg, F.; Affolter, M.; Driscoll, C. F.; O'Neil, T. M.; Valentini, F.

    2012-10-01

    Electron Acoustic Waves (EAWs) are the low-frequency branch of near-linear Langmuir (plasma) waves: the frequency is such that the complex dielectric function (Dr, Di) has Dr= 0; and ``flattening'' of f(v) near the wave phase velocity vph gives Di=0 and eliminates Landau damping. Here, we observe standing axisymmetric EAWs in a pure ion column.footnotetextF. Anderegg, et al., Phys. Rev. Lett. 102, 095001 (2009). At low excitation amplitudes, the EAWs have vph˜1.4 v, in close agreement with near-linear theory. At moderate excitation strengths, EAW waves are observed over a range of frequencies, with 1.3 v vphvph.footnotetextF. Valentini et al., arXiv:1206.3500v1. Large amplitude EAWs have strong phase-locked harmonic content, and experiments will be compared to same-geometry simulations, and to simulations of KEENfootnotetextB. Afeyan et al., Proc. Inertial Fusion Sci. and Applications 2003, A.N.S. Monterey (2004), p. 213. waves in HEDLP geometries.

  8. Pure Electric and Pure Magnetic Resonances in Near-Infrared Metal Double-Triangle Metamaterial Arrays

    Institute of Scientific and Technical Information of China (English)

    CAO Zhi-Shen; PAN Jian; CHEN Zhuo; ZHAN Peng; MIN Nai-Ben; WANG Zhen-Lin

    2011-01-01

    @@ We experimentally and numerically investigate the optical properties of metamaterial arrays composed of double partially-overlapped metallic nanotriangles fabricated by an angle-resolved nanosphere lithography.We demonstrate that each double-triangle can be viewed as an artificial magnetic element analogous to the conventional metal split-ring-resonator.It is shown that under normal-incidence conditions,individual double-triangle can exhibit a strong local magnetic resonance,but the collective response of the metamaterial arrays is purely electric because magnetic resonances of the two double-triangles in a unit cell having opposite openings are out of phase.For oblique incidences the metamaterial arrays are shown to support a pure magnetic response at the same frequency band.Therefore,switchable electric and magnetic resonances are achieved in double-triangle arrays.Moreover,both the electric and magnetic resonances axe shown to allow for a tunability over a large spectral range down to near-infrared.%We experimentally and numerically investigate the optical properties of metamaterial arrays composed of double partially-overlapped metallic nanotriangles fabricated by an angle-resolved nanosphere lithography. We demonstrate that each double-triable can be viewed as an artificial magnetic element analogous to the conventional metal split-ring-resonator. It is shown that under normal-incidence conditions, individual double-triangle can exhibit a strong local magnetic resonance, but the collective response of the metamaterial arrays is purely electric because magnetic resonances of the two double-triangles in a unit cell having opposite openings are out of phase.For oblique incidences the metamaterial arrays are shown to support a pure magnetic response at the same frequency band. Therefore, switchable electric and magnetic resonances are achieved in double-triangle arrays.Moreover, both the electric and magnetic resonances are shown to allow for a tunability over

  9. Long-Lived Vortex Structures in Collisional Pure and Gas-Discharge Nonneutral Electron Plasmas

    CERN Document Server

    Kervalishvili, N A

    2013-01-01

    The analysis of experimental investigations of equilibrium, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas during the time much more than the electron-neutral collision time has been carried out. The problem of long confinement of the column of pure electron plasma in Penning-Malmberg trap is considered. The mechanism of stability of long-lived vortex structure in gas-discharge nonneutral electron plasma is investigated. The collapse of electron sheath in gas-discharge nonneutral electron plasma in Penning cell at high pressures of neutral gas is described. The interaction between the stable vortex structure and the annular electron sheath, and the action of vortex structures on the transport of electrons along and across the magnetic field are discussed.

  10. Complex windmill transformation producing new purely magnetic fluids

    NARCIS (Netherlands)

    Lozanovski, L.; Wylleman, L.

    2011-01-01

    Minimal complex windmill transformations of G2IB(ii) spacetimes (admitting a two-dimensional Abelian group of motions of the so-called Wainwright B(ii) class) are defined and the compatibility with a purely magnetic Weyl tensor is investigated. It is shown that the transformed spacetimes cannot be p

  11. Measurements of electron drift velocity in pure isobutane

    Energy Technology Data Exchange (ETDEWEB)

    Vivaldini, Tulio C.; Lima, Iara B.; Goncalves, Josemary A.C.; Botelho, Suzana; Tobias, Carmen C.B., E-mail: ccbueno@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Ridenti, Marco A.; Pascholati, Paulo R. [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Fisica. Lab. do Acelerador Linear; Fonte, Paulo; Mangiarotti, Alessio [Universidade de Coimbra (Portugal). Dept de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas

    2009-07-01

    In this work we report on preliminary results related to the dependence of the electron drift velocity for pure isobutane as a function of reduced electric field (E/N) in the range from 100 Td up to 216 Td. The measurements of electron drift velocity were based on the Pulsed Townsend technique. In order to validate the technique and analyzing non-uniformity effects, results for nitrogen are also presented and compared with a numerical simulation of the Bolsig+ code. (author)

  12. Electronic structures and physical properties of pure aluminum metal

    Institute of Scientific and Technical Information of China (English)

    谢佑卿; 刘心笔

    1999-01-01

    By one-atom theory, the electronic structure of pure Al metal with f.c.c, structure has been determined to be [Ne](3sc)1.8790(3pc)0.4982(3sf+3pf)0.6228. According to this electronic structure, the potential curve, lattice constant, cohesive energy, elastisity, and the temperature dependence of the linear thermal expansion coefficients have been calculated. The electronic structures and characteristic properties of Al metals with b. c. c., h.c.p. structures and liquid have been studied. It is argued that the pure Al metal with f. c.c. structure can exist naturally, but with b. c. c.and h. c.p. structures cannot.##属性不符

  13. Pure-type superconducting permanent-magnet undulator.

    Science.gov (United States)

    Tanaka, Takashi; Tsuru, Rieko; Kitamura, Hideo

    2005-07-01

    A novel synchrotron radiation source is proposed that utilizes bulk-type high-temperature superconductors (HTSCs) as permanent magnets (PMs) by in situ magnetization. Arrays of HTSC blocks magnetized by external magnetic fields are placed below and above the electron path instead of conventional PMs, generating a periodic magnetic field with an offset. Two methods are presented to magnetize the HTSCs and eliminate the field offset, enabling the HTSC arrays to work as a synchrotron radiation source. An analytical formula to calculate the peak field achieved in a device based on this scheme is derived in a two-dimensional form for comparison with synchrotron radiation sources using conventional PMs. Experiments were performed to demonstrate the principle of the proposed scheme and the results have been found to be very promising.

  14. Pure iron and other magnetic minerals in meteorites

    Science.gov (United States)

    Pechersky, D. M.; Markov, G. P.; Tsel'movich, V. A.

    2015-01-01

    The results of thermomagnetic and microprobe analyses of 37 samples from 25 different types of meteorite are analyzed with the focus on the presence of pure (nickel-free) iron in them. It is established that the metallic particles in the studied meteorites cluster in three isolated groups: (1) pure iron, (2) kamacite with mode 3-6% Ni, and (3) taenite with mode ˜50% Ni. The hiatuses in the Fe-Ni alloy compositions between these groups of magnetic grains contradict the Fe-Ni phase diagram, which predicts a continuous series of solid solutions in this system. This isolated distribution of the compositions of the metallic particles in the meteorites is reasonably accounted for by the specific properties of the melt (melts) and the processes of their crystallization and decomposition in space. It is suggested that pure iron in the meteorites could have been formed by either of two scenarios. According to the "primary," pure iron crystallizes from the melt, and according to the "secondary" scenario, it is produced by the decomposition of the solid solution.

  15. Surface modification of pure titanium by pulsed electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.D. [Key Laboratory of Materials Modification and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Laboratoired' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France); Hao, S.Z., E-mail: ebeam@dlut.edu.cn [Key Laboratory of Materials Modification and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Li, X.N. [Key Laboratory of Materials Modification and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Dong, C., E-mail: dong@dlut.edu.cn [Key Laboratory of Materials Modification and School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Grosdidier, T., E-mail: Thierry.grosdidier@univ-metz.fr [Laboratoired' Etude des Microstructures et de Mecanique des Materiaux (LEM3), CNRS UMR 7239, Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France)

    2011-04-15

    The microstructure, hardness and corrosion resistance of commercially pure Ti treated by low energy high current pulsed electron beam (LEHCPEB) have been investigated. The thin near-surface melted layer rapidly solidified into {beta} and subsequently transformed into ultrafine {alpha}' martensite. This has led to a drastic improvement of the corrosion properties and a significant increase (more than 60%) in hardness of the top surface.

  16. On the Nonrelativistic 2D Purely Magnetic Supersymmetric Pauli Operator

    OpenAIRE

    Grinevich, P.; Mironov, A.(Lebedev Physics Institute; ITEP, Moscow, Russia); Novikov, S.

    2011-01-01

    The Complete Manifold of Ground State Eigenfunctions for the Purely Magnetic 2D Pauli Operator is considered as a by-product of the new reduction found by the present authors few years ago for the Algebrogeometric Inverse Spectral Data (i.e. Riemann Surfaces and Divisors). This reduction is associated with the (2+1) Soliton Hierarhy containing a 2D analog of the famous "Burgers System". This article contains also exposition of the previous works made since 1980 including the first topological...

  17. Low-frequency fluctuations in a pure toroidal magnetized plasma

    Indian Academy of Sciences (India)

    P K Sharma; R Singh; D Bora

    2009-12-01

    A magnetized, low- plasma in pure toroidal configuration is formed and extensively studied with ion mass as control parameter. Xenon, krypton and argon plasmas are formed at a fixed toroidal magnetic field of 0.024 T, with a peak density of ∼ 1011 cm-3, ∼ 4 × 1010 cm-3 and ∼ 2 × 1010 cm−3 respectively. The experimental investigation of time-averaged plasma parameter reveals that their profiles remain insensitive to ion mass and suggests that saturated slab equilibrium is obtained. Low-frequency (LF) coherent fluctuations ( < ci) are observed and identified as flute modes. Here ci represents ion cyclotron frequency. Our results indicate that these modes get reduced with ion mass. The frequency of the fluctuating mode decreases with increase in the ion mass. Further, an attempt has been made to discuss the theory of flute modes to understand the relevance of some of our experimental observations.

  18. DYNAMIC COMPACTION OF PURE COPPER POWDER USING PULSED MAGNETIC FORCE

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The compaction of pure Cu powder was carried out through a series of experiments using dynamic magnetic pulse compaction, and the effects of process parameters, such as discharge energy and compacting direction, on the homogeneity and the compaction density of compacted specimens were presented and discussed. The results indicated that the compaction density of specimens increased with the augment of discharge voltage and time. During unidirectional compaction, there was a density gradient along the loading direction in the compacted specimen, and the minimum compaction density was localized to the center of the bottom of the specimen. The larger the aspect ratio of a powder body, the higher the compaction density of the compacted specimen. And high conductivity drivers were beneficial to the increase of the compaction density. The iterative and the double direction compaction were efficient means to manufacture the homogeneous and high-density powder parts.

  19. Thickness-dependent electronic structure modulation of ferromagnetic films on shape memory alloy substrates based on a pure strain effect

    Science.gov (United States)

    Feng, Chun; Hu, Di; Gong, Kui; Jiang, Xumin; Yin, Jianjuan; Cao, Yi; Tang, Xiao-Lei; Yang, Feng; Zhou, Zhongfu; Yu, Guanghua; Andrew Evans, D.

    2016-11-01

    Pure strain-induced electronic structure modulation in ferromagnetic films is critical for developing reliable strain-assisted spintronic devices with low power consumption. For the conventional electricity-controlled strain engineering, it is difficult to reveal the pure strain effect on electronic structure tunability due to the inseparability of pure strain effect and surface charge effect. Here, a non-electrically controlled NiTi shape memory alloy was utilized as a strain output substrate to induce a pure strain on attached Fe films through a thermally controlled shape memory effect. The pure strain induced electronic structure evolution was revealed by in-situ X-ray photoelectron spectroscopy and correlated with first-principles calculations and magnetic anisotropy measurements. A compressive strain enhances the shielding effect for core electrons and significantly tunes their binding energy. Meanwhile, the strain modifies the partial density of states of outer d orbits, which may affect spin-orbit coupling strength and related magnetic anisotropy. This work helps for clarifying the physical nature of the pure strain effect and developing the pure-strain-assisted spintronic devices.

  20. Non-radial oscillations of the magnetized rotating stars with purely toroidal magnetic fields

    CERN Document Server

    Asai, Hidetaka; Yoshida, Shijun

    2015-01-01

    We calculate non-axisymmetric oscillations of uniformly rotating polytropes magnetized with a purely toroidal magnetic field, taking account of the effects of the deformation due to the magnetic field. As for rotation, we consider only the effects of Coriolis force on the oscillation modes, ignoring those of the centrifugal force, that is, of the rotational deformation of the star. Since separation of variables is not possible for the oscillation of rotating magnetized stars, we employ finite series expansions for the perturbations using spherical harmonic functions. We calculate magnetically modified normal modes such as $g$-, $f$-, $p$-, $r$-, and inertial modes. In the lowest order, the frequency shifts produced by the magnetic field scale with the square of the characteristic Alfv\\'en frequency. As a measure of the effects of the magnetic field, we calculate the proportionality constant for the frequency shifts for various oscillation modes. We find that the effects of the deformation are significant for ...

  1. Synthesis, Characterization, and Magnetic Properties of Pure and EDTA-Capped NiO Nanosized Particles

    Directory of Open Access Journals (Sweden)

    H. T. Rahal

    2017-01-01

    Full Text Available The effect of ethylenediaminetetraacetic acid (EDTA as a capping agent on the structure, morphology, optical, and magnetic properties of nickel oxide (NiO nanosized particles, synthesized by coprecipitation method, was investigated. Nickel chloride hexahydrate and sodium hydroxide (NaOH were used as precursors. The resultant nanoparticles were characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, and scanning electron microscopy (SEM. XRD patterns showed that NiO have a face-centered cubic (FCC structure. The crystallite size, estimated by Scherrer formula, has been found in the range of 28–33 nm. It is noticed that EDTA-capped NiO nanoparticles have a smaller size than pure nanoparticles. Thus, the addition of 0.1 M capping agent EDTA can form a nucleation point for nanoparticles growth. The optical and magnetic properties were investigated by Fourier transform infrared spectroscopy (FTIR and UV-vis absorption spectroscopy (UV as well as electron paramagnetic resonance (EPR and magnetization measurements. FTIR spectra indicated the presence of absorption bands in the range of 402–425 cm−1, which is a common feature of NiO. EPR for NiO nanosized particles was measured at room temperature. An EPR line with g factor ≈1.9–2 is detected for NiO nanoparticles, corresponding to Ni2+ ions. The magnetic hysteresis of NiO nanoparticles showed that EDTA capping recovers the surface magnetization of the nanoparticles.

  2. Pure electron-electron dephasing in percolative aluminum ultrathin film grown by molecular beam epitaxy.

    Science.gov (United States)

    Lin, Shih-Wei; Wu, Yue-Han; Chang, Li; Liang, Chi-Te; Lin, Sheng-Di

    2015-01-01

    We have successfully grown ultrathin continuous aluminum film by molecular beam epitaxy. This percolative aluminum film is single crystalline and strain free as characterized by transmission electron microscopy and atomic force microscopy. The weak anti-localization effect is observed in the temperature range of 1.4 to 10 K with this sample, and it reveals that, for the first time, the dephasing is purely caused by electron-electron inelastic scattering in aluminum.

  3. Magnetic electron lenses

    CERN Document Server

    1982-01-01

    No single volume has been entirely devoted to the properties of magnetic lenses, so far as I am aware, although of course all the numerous textbooks on electron optics devote space to them. The absence of such a volume, bringing together in­ formation about the theory and practical design of these lenses, is surprising, for their introduction some fifty years ago has created an entirely new family of commercial instruments, ranging from the now traditional transmission electron microscope, through the reflection and transmission scanning microscopes, to co­ lumns for micromachining and microlithography, not to mention the host of experi­ mental devices not available commercially. It therefore seemed useful to prepare an account of the various aspects of mag­ netic lens studies. These divide naturally into the five chapters of this book: the theoretical background, in which the optical behaviour is described and formu­ lae given for the various aberration coefficients; numerical methods for calculat­ ing...

  4. Application of permanent magnets in accelerators and electron storage rings

    Science.gov (United States)

    Halbach, K.

    1985-04-01

    The use of permanent-magnet systems in high-energy accelerators and as sources of synchrotron radiation in electron-storage rings is discussed in a review of recent experimental investigations. Consideration is given to the generic advantages of permanent magnets over electromagnets (higher field strength per magnet size) in small-scale configurations; the magnetic properties of some charge-sheet-equivalent-permanent-magnet materials (CSEMs); and the design of pure-CSEM and CSEM-Fe-hybrid multipole magnetic lenses, dipoles, and undulator/wiggler systems for use in free-electron lasers and the production of elliptically polarized synchrotron light. Drawings and diagrams are provided.

  5. The influence of anthropogenic pure iron on magnetic properties of indoor dust.

    Science.gov (United States)

    Górka-Kostrubiec, Beata; Teisseyre-Jeleńska, Maria

    2015-04-01

    observed for the samples containing high contribution of pure iron. After heating, the loops were wide and their parameters are characteristic for SD+MD grains of the magnetite. The results show that the small amount of soft-magnetic pure iron significantly affects the values of hysteresis parameters , i.e. shifts the ratios Bcr/Bc towards larger value and Mrs/Ms towards smaller values on the Day-Dunlop's diagram. The recognition of morphology and chemical composition of the magnetic fraction was confirmed by the scanning electron microscope observation and the energy dispersive X-ray spectrometer measurement. Microscopic observations of dust samples revealed the presence of the elongated particles composed of pure iron. We found that magnetic susceptibility correlates with the concentration of following anthropogenic elements: Co, Cr, Fe, Ni but only Fe concentration influences high values of susceptibility observed in 2nd set of samples. Reference: B. Górka-Kostrubiec, M. Jeleńska and E. Król. (2014) Magnetic signature of indoor air pollution: household dust study. Acta Geophysica vol. 62, 1478-1503, DOI: 10.2478/s11600-014-0238-1.

  6. Secondary effects on electron multiplication in pure isobutane

    Energy Technology Data Exchange (ETDEWEB)

    Mangiarotti, A. [Laboratorio de Instrumentacao e Fisica Experimental de Particulas, Departamento de Fisica da Universidade de Coimbra, 3004-516 Coimbra (Portugal); Departamento de Fisica, Faculdade de Ciencias e Tecnologia, Universidade de Coimbra, Coimbra (Portugal); Lima, I.B.; Vivaldini, T.C. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000 Cidade Universitaria, Sao Paulo (Brazil); Goncalves, J.A.C. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000 Cidade Universitaria, Sao Paulo (Brazil); Departamento de Fisica, Pontificia Universidade Catolica de Sao Paulo, 01303-050 Sao Paulo (Brazil); Petri, A.R. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000 Cidade Universitaria, Sao Paulo (Brazil); Botelho, S. [Instituto de Pesquisas Energeticas e Nucleares, 05508-000 Cidade Universitaria, Sao Paulo (Brazil); Departamento de Fisica, Pontificia Universidade Catolica de Sao Paulo, 01303-050 Sao Paulo (Brazil); and others

    2012-12-01

    The presence of secondary processes in electron multiplication under high uniform electric fields at atmospheric pressure in pure isobutane was investigated. The experimental setup consists of a Resistive Plate Chamber-like cell with the anode made of a high resistivity glass (2 Multiplication-Sign 10{sup 12}{Omega}cm) and a metallic cathode, on which photoelectrons are produced by the incidence of a pulsed laser beam. In particular, the dependence of the first Townsend coefficient ({alpha}) on the repetition rate and the intensity of the UV laser pulses was studied. The E/N range considered spanned from Almost-Equal-To 145 to Almost-Equal-To 200 Td. The {alpha} coefficient was determined by measuring both the primary ionization and the avalanche currents with the help of an electrometer, directly connected to the cathode. Of all the investigated secondary effects, only the ohmic drop across the resistive glass has been found to be non-negligible in the present experimental conditions and has been corrected for. The obtained values are compared with Magboltz simulation results and presented in tabular form.

  7. The quest for rationalizing the magnetism in purely organic semiquinone-bridged bisdithiazolyl molecular magnets.

    Science.gov (United States)

    Fumanal, Maria; Deumal, Mercè

    2016-07-27

    Semiquinone-bridged bisdithiazolyl-based radicals (XBBO) are appealing purely organic magnetic building blocks for the synthesis of new functional materials. Remarkably, for the phenyl-derivative PhBBO, the rationalization of its magnetism becomes a proof of concept that DFT can dramatically fail to evaluate JAB magnetic interactions between purely organic radical pairs. Instead, wavefunction-based methods are required. Once JAB's are fully characterized, the magnetic topology of PhBBO is disclosed to consist of ferromagnetic FM π-stacks that are very weakly coupled (by FM and AFM JAB interactions). The magnetic susceptibility χT(T) and magnetization M(H) of PhBBO are then calculated using a first-principles bottom-up approach. The study of the unit cell contraction upon cooling from room temperature to zero-Kelvin is relevant to propose a suitable model for the phase transition that occurs at 4.5 K. A simplistic picture tells us that the antiparallel-aligned 1D-FM-chains convert into domains of weakly either FM- or AFM-coupled 1D-FM-chains. Accordingly, the presence of these domains may introduce geometrical spin frustration below 4.5 K.

  8. Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in γ-Fe temperature region

    Science.gov (United States)

    Wu, Yan; Duan, Guosheng; Zhao, Xiang

    2015-03-01

    Effects of magnetic field intensity on carbon diffusion coefficient in pure iron in the γ-Fe temperature region were investigated using carburizing technology. The carbon penetration profiles from the iron surface to interior were measured by field emission electron probe microanalyzer. The carbon diffusion coefficient in pure iron carburized with different magnetic field intensities was calculated according to the Fick's second law. It was found that the magnetic field intensity could obviously affect the carbon diffusion coefficient in pure iron in the γ-Fe temperature region, and the carbon diffusion coefficient decreased obviously with the enhancement of magnetic field intensity, when the magnetic field intensity was higher than 1 T, the carbon diffusion coefficient in field annealed specimen was less than half of that of the nonfield annealed specimen, further enhancing the magnetic field intensity, the carbon diffusion coefficient basically remains unchanged. The stiffening of lattice due to field-induced magnetic ordering was responsible for an increase in activation barrier for jumping carbon atoms. The greater the magnetic field intensity, the stronger the inhibiting effect of magnetic field on carbon diffusion.

  9. Pure Electron Equilibrium and Transport Jumps in the Columbia Non-neutral Torus

    Science.gov (United States)

    Hahn, M.; Pedersen, T. Sunn; Marksteiner, Q.; Berkery, J.; Brenner, P. W.

    2008-11-01

    CNT is a simple stellarator being used to study pure electron plasmas. The dependence of the equilibrium on the location of the electron source has been studied. When the emitter is displaced from the magnetic axis the equilibrium on the inner surfaces is consistent with a global thermal equilibrium, as demonstrated by comparing measurements with the results of a numerical equilibrium solver. The equilibrium of a pure electron plasma depends on electrostatic boundary conditions. Recently a conducting boundary conforming to the last closed flux surface was installed. Experimental studies have been done to characterize the equilibrium with this new boundary condition and compare it to the results with the non-conforming boundary. For an internal emitter in a steady state plasma the loss rate of electrons is the same as the total emission current. As parameters are varied to increase transport abrupt jumps in the emission current occur at particular currents. The jumps imply discontinuous changes in the confinement time and are accompanied by measureable changes in the equilibrium. Using multiple emitters it has been shown that the jumps occur at the local emission current not the total transport rate, which strongly suggests that the jumps are caused by a cathode instability. Supported by NSF-DOE grant NSF-PHY-04-49813.

  10. Surface electric current distributions on spheres and spheroids as sources of pure quadrupole magnetic fields

    OpenAIRE

    L. Medina; E. Ley-Koo

    2011-01-01

    Neutral atom magnetic traps and nuclear magnetic resonance imaging require internal regions with constant gradient magnetic induction fields, which are identified as pure quadrupole fields. This contribution starts from such fields in the interior of spheres and spheroids in cartesian coordinates, identifying immediately their respective scalar magnetic potentials. Next, the corresponding potentials inside and outside are constructed using spherical and spheroidal harmonic functions, respecti...

  11. Phase Pure Synthesis and Morphology Dependent Magnetization in Mn Doped ZnO Nanostructures

    Directory of Open Access Journals (Sweden)

    Murtaza Saleem

    2014-01-01

    Full Text Available Zn0.95Mn0.05O nanostructures were synthesized using sol gel derived autocombustion technique. As-burnt samples were thermally annealed at different temperatures (400, 600, and 800°C for 8 hours to investigate their effect on structural morphology and magnetic behavior. X-ray diffraction and scanning electron microscopic studies demonstrated the improvement in crystallinity of phase pure wurtzite structure of Mn doped ZnO with variation of annealing temperature. Energy dispersive X-ray elemental compositional analysis confirmed the exact nominal compositions of the reactants. Electrical resistivity measurements were performed with variation in temperature, which depicted the semiconducting nature similar to parent ZnO after 5 at% Mn doping. Magnetic measurements by superconducting quantum interference device detected an enhanced trend of ferromagnetic interactions in thermally annealed compositions attributed to the improved structural morphology and crystalline refinement process.

  12. Nanostructured electronic and magnetic materials

    Indian Academy of Sciences (India)

    R V Ramanujan

    2003-02-01

    Research and development in nanostructured materials is one of the most intensely studied areas in science. As a result of concerted R & D efforts, nanostructured electronic and magnetic materials have achieved commercial success. Specific examples of novel industrially important nanostructured electronic and magnetic materials are provided. Advantages of nanocrystalline magnetic materials in the context of both materials and devices are discussed. Several high technology examples of the use of nanostructured magnetic materials are presented. Methods of processing nanostructured materials are described and the examples of sol gel, rapid solidification and powder injection moulding as potential processing methods for making nanostructured materials are outlined. Some opportunities and challenges are discussed.

  13. Long-Lived Vortex Structures in Collisional Pure and Gas-Discharge Nonneutral Electron Plasmas

    OpenAIRE

    Kervalishvili, N. A.

    2013-01-01

    The analysis of experimental investigations of equilibrium, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas during the time much more than the electron-neutral collision time has been carried out. The problem of long confinement of the column of pure electron plasma in Penning-Malmberg trap is considered. The mechanism of stability of long-lived vortex structure in gas-discharge nonneutral electron plasma is investigated. The collap...

  14. Effects of Electric and Magnetic Fields on Pure Dephasing of Exciton Qubits

    Institute of Scientific and Technical Information of China (English)

    LIU Yun-Fei; XIAO Jing-Lin

    2009-01-01

    In a two-dimensional quantum dot (QD) with parabolic confinement potential, we investigate pure dephasing due to deformation potential exciton-bulk longitudinal acoustic phonons (LAP) interaction for exciton qubits under the influence of external static electric and magnetic fields by adopting the full quantum-mechanical method of Kunihiro Kojima and Akihisa Tomita. The wave function is found and the dependence of the pure dephusing factor on the confinement length of the QD and time and temperature is discussed. We find the external electric and magnetic fields have important effects on pure dephasing of exciton qubits because exciton-LAP interaction increases, leading to more pure dephasing.

  15. Pure magnetic hard fct FePt nanoparticles: Chemical synthesis, structural and magnetic properties correlations

    Energy Technology Data Exchange (ETDEWEB)

    Suber, L., E-mail: lorenza.suber@ism.cnr.it [ISM-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Marchegiani, G. [ISM-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Olivetti, E.S.; Celegato, F.; Coïsson, M.; Tiberto, P. [INRIM, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy); Allia, P. [DISAT Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Barrera, G. [Dipartimento di Chimica, Università di Torino, Via Pietro Giuria 7, 10125 Torino (Italy); Pilloni, L. [UTTMAT-CHI, Via Anguillarese 10, 00123 S. Maria di Galeria, Roma (Italy); Barba, L. [IC-CNR, Area Science Park, SS 14 Km 163.5 Basovizza, 34149 Trieste (Italy); Padella, F. [UTTMAT-CHI, Via Anguillarese 10, 00123 S. Maria di Galeria, Roma (Italy); Cossari, P. [IGAG-CNR, Area della Ricerca di Roma 1, Via Salaria km 29.300, 00015 Monterotondo Scalo, RM (Italy); Chiolerio, A. [Istituto Italiano di Tecnologia, Center for Space Human Robotics, Corso Trento 21, 10129 Torino (Italy)

    2014-03-01

    FePt nanoparticles, containing a near-equal atomic percentage of Fe and Pt, with a face centered tetragonal structure (fct), are challenging for potential applications in high performance permanent magnets and high density data storage. In this study, we report on the chemical synthesis, carried out both solvothermally and hydrothermally in autoclave reacting iron (III) acetylacetonate and platinum (II) acetylacetonate with tri- or tetra-ethylene glycol, these employed as solvents, reducers and particle surface protecting agents as well. In both methods, a subsequent thermal treatment at high temperatures is necessary to transform the magnetic soft face centered cubic (fcc) phase to the hard fct one. Organic low-weight molecules, generally used to protect the nanoparticle surface and avoid particle aggregation, are decomposed by the thermal treatment resulting in particle aggregation and coalescence phenomena; on the contrary, in this case, a polymer matrix is formed as particle protecting agent and, by thermally treating the hydrothermally prepared nanoparticles up to 750 °C for 1 h, the pure magnetic hard fct phase is obtained while preserving the nanostructure. A detailed study is carried out on FePt nanoparticle structure (fcc and fct phases) and correlated to the magnetic properties of the system. - Highlights: • fct FePt nanoparticles for hard magnetic nanotechnology applications. • Influence of synthesis parameters on the precursor fcc FePt nanoparticle structure. • Easy hydrothermal method for preparing pure fct FePt nanoparticles. • Monitoring the role of temperature and time on the FePt fcc–fct phase transformation. • Correlation between FePt nanoparticle structural and magnetic properties.

  16. Tailored jump operators for purely dissipative quantum magnetism

    Science.gov (United States)

    Weimer, Hendrik

    2017-01-01

    I propose an architecture for the realization of dissipative quantum many-body spin models. The dissipative processes are mediated by interactions with auxiliary particles and lead to a widely tunable class of correlated quantum jump operators. These findings enable the investigation of purely dissipative spin models, where coherent dynamics is entirely absent. I provide a detailed review of a recently introduced variational method to analyze such dissipative quantum many-body systems, and I discuss a specific example in terms of a purely dissipative Heisenberg model, for which I find an additional disordered phase that is not present in the corresponding ground state phase diagram.

  17. Tailored jump operators for purely dissipative quantum magnetism

    CERN Document Server

    Weimer, Hendrik

    2016-01-01

    I propose an archtitecture for the realization of dissipative quantum many-body spin models. The dissipative processes are mediated by interactions with auxiliary particles and lead to a widely tunable class of correlated quantum jump operators. These findings enable the investigation of purely dissipative spin models, where coherent dynamics is entirely absent. I provide a detailed review of a recently introduced variational method to analyze such dissipative quantum many-body systems, and I discuss a specific example in terms of a purely dissipative Heisenberg model, for which I find an additional disordered phase that is not present in the corresponding ground state phase diagram.

  18. Electron Cloud Trapping in Recycler Combined Function Dipole Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, Sergey A. [Chicago U.; Nagaitsev, S. [Fermilab

    2016-10-04

    Electron cloud can lead to a fast instability in intense proton and positron beams in circular accelerators. In the Fermilab Recycler the electron cloud is confined within its combined function magnets. We show that the field of combined function magnets traps the electron cloud, present the results of analytical estimates of trapping, and compare them to numerical simulations of electron cloud formation. The electron cloud is located at the beam center and up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multiturn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The multi-turn build-up can be stopped by injection of a clearing bunch of 1010 p at any position in the ring.

  19. Image tuning techniques for enhancing the performance of pure permanent magnet undulators with small gap/period ratios

    Energy Technology Data Exchange (ETDEWEB)

    Tatchyn, R. [Stanford Univ., CA (United States)

    1995-12-31

    The on-axis field of a small-gap undulator constricted out of pure permanent magnet (PM) blocks arranged in an alternating-dipole (i.e., 2 dipoles/period) array can be substantially varied by positioning monolithic permeable plates above and below the undulator jaws. This simple technique, which can be used to control the 1st harmonic energy in conventional synchrotron radiation (SR) or Free Electron Laser (FEL) applications requiring sub-octave tuning, can also be shown to suppress magnetic inhomogeneities that can contribute to the undulator`s on-axis field errors. If a standard 4 block/period Halbach undulator, composed of PM blocks with square cross sections, is rearranged into an alternating-dipole array with the same period, the peak field that can be generated with superimposed image plates can substantially exceed that of the pure-PM Halbach array. This design technique, which can be viewed as intermediate between the {open_quotes}pure-PM{close_quotes} and standard {open_quotes}hybrid/PM{close_quotes} configurations, provides a potentially cost-effective method of enhancing the performance of small-gap, pure-PM insertion devices. In this paper we report on the analysis and recent characterization of pure-PM undulator structures with superimposed image plates, and discuss possible applications to FEL research.

  20. Magnetic Properties of Amorphous Fe-Si-B Powder Cores Mixed with Pure Iron Powder

    Science.gov (United States)

    Kim, Hyeon-Jun; Nam, Seul Ki; Kim, Kyu-Sung; Yoon, Sung Chun; Sohn, Keun-Yong; Kim, Mi-Rae; Sul Song, Yong; Park, Won-Wook

    2012-10-01

    Amorphous Fe-Si-B alloy was prepared by melt-spinning, and then the ribbons were pulverized and ball-milled to make the amorphous powder of ˜25 µm in size. Subsequently those were mixed with pure iron powders with an average particle size of 3 µm, and 1.5 wt % water glass diluted by distilled water at the ratio of 1:2. The powder mixtures were cold compacted at 650 MPa in toroid die, and heat treated at 430-440 °C under a nitrogen atmosphere for 1 h and 30 min, respectively. The soft magnetic properties of powder core were investigated using a B-H analyzer and a flux meter at the frequency range of ˜100 kHz. The microstructure was observed using scanning electron microscope (SEM), and the density of the core was measured using the principle of Archimedes. Based on the experimental results, the amorphous powder mixed with pure iron powder showed the improved powder compactability, which resulted in the increased permeability and the reduced core loss.

  1. Pure-oxygen radiative shocks with electron thermal conduction

    Science.gov (United States)

    Borkowski, Kazimierz J.; Shull, J. Michael

    1990-01-01

    Steady state radiative shock models in gas composed entirely of oxygen are calculated with the purpose of explaining observations of fast-moving knots in Cas A and other oxygen-rich SNRs. Models with electron thermal conduction differ significantly from models in which conduction is neglected. Conduction reduces postshock electron temperatures by a factor of 7-10 and flattens temperature gradients. The O III ion, whose forbidden emission usually dominates the observed spectra, is present over a wide range of shock velocities, from 100 to 170 km/s. The electron temperature in the O III forbidden line formation region is 30,000 K, in agreement with the 20,000 K derived from observations. All models with conduction have extensive warm (T above 4000 K) photoionization zones, which provides better agreement with observed optical O I line strengths.

  2. Structural and magnetic properties of pure and Cu doped In{sub 2}O{sub 3} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, N. Sai; Kaleemulla, S., E-mail: skaleemulla@gmail.com; Rao, N. Madhusudhana; Krishnamoorthi, C.; Begam, M. Rigana [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore – 632014 (India); Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam –603102 (India); UGC-DAE-CSR, Kalpakkam Node, Kokilamedu-603104 (India)

    2015-06-24

    Pure and Cu (7 at.%) doped In{sub 2}O{sub 3} thin films were prepared using an electron beam evaporation technique. A systematic study was carried out on the structural, chemical and magnetic properties of the thin films. X-ray diffraction analysis revealed that all the films were cubic in structure. The pure and Cu doped In{sub 2}O{sub 3} thin films showed ferromagnetism at room temperature. The Cu doped In{sub 2}O{sub 3} thin films showed the saturation magnetization, coercivity and retentivity of 38.71 emu/cm{sup 3}, 245 G and 5.54 emu/cm{sup 3}, respectively.

  3. Time-resolved imaging of purely valence-electron dynamics during a chemical reaction

    DEFF Research Database (Denmark)

    Hockett, Paul; Bisgaard, Christer Z.; Clarkin, Owen J.

    2011-01-01

    Chemical reactions are manifestations of the dynamics of molecular valence electrons and their couplings to atomic motions. Emerging methods in attosecond science can probe purely electronic dynamics in atomic and molecular systems(1-6). By contrast, time-resolved structural-dynamics methods......,17): in both cases, this sensitivity derives from the ionization-matrix element(18,19). Here we demonstrate a time-resolved molecular-frame photoelectron-angular-distribution (TRMFPAD) method for imaging the purely valence-electron dynamics during a chemical reaction. Specifically, the TRMFPADs measured during...... the non-adiabatic photodissociation of carbon disulphide demonstrate how the purely electronic rearrangements of the valence electrons can be projected from inherently coupled electronic-vibrational dynamics. Combined with ongoing efforts in molecular frame alignment(20) and orientation(21,22), TRMFPADs...

  4. Normal modes and mode transformation of pure electron vortex beams

    Science.gov (United States)

    Thirunavukkarasu, G.; Mousley, M.; Babiker, M.; Yuan, J.

    2017-02-01

    Electron vortex beams constitute the first class of matter vortex beams which are currently routinely produced in the laboratory. Here, we briefly review the progress of this nascent field and put forward a natural quantum basis set which we show is suitable for the description of electron vortex beams. The normal modes are truncated Bessel beams (TBBs) defined in the aperture plane or the Fourier transform of the transverse structure of the TBBs (FT-TBBs) in the focal plane of a lens with the said aperture. As these modes are eigenfunctions of the axial orbital angular momentum operator, they can provide a complete description of the two-dimensional transverse distribution of the wave function of any electron vortex beam in such a system, in analogy with the prominent role Laguerre-Gaussian (LG) beams played in the description of optical vortex beams. The characteristics of the normal modes of TBBs and FT-TBBs are described, including the quantized orbital angular momentum (in terms of the winding number l) and the radial index p>0. We present the experimental realization of such beams using computer-generated holograms. The mode analysis can be carried out using astigmatic transformation optics, demonstrating close analogy with the astigmatic mode transformation between LG and Hermite-Gaussian beams. This article is part of the themed issue 'Optical orbital angular momentum'.

  5. Development of Electron Magnetic Spectrometer and Application

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The interaction between ultra-short pulse laser and solid plasma produces hot electron. Thereare many methods to study hot electron spectrum and space distribution. But the way of electron magnetic spectrometer is the most directional method. Particles with charge act circle movement in spare magnetic field. Different energy electrons have different whirl radius. So along whirl diameter direction electron spectrum can be obtained. Actually, electron is affected by gravity excursion and magnetic grads and curvature excursion besides lawrence power. The direction of

  6. Effects of geometry in itinerant electron magnets

    Science.gov (United States)

    Nakamura, H.; Muro, Y.; Kohara, T.; Shiga, M.

    2007-04-01

    The magnetism of quasi-one-dimensional itinerant electron magnets RMn4Al8 is compared with that of the typical frustrated itinerant electron magnet YMn2. The possible formation and observation of the spin pseudogap are discussed in connection with the spin-liquid state in strongly correlated itinerant electron systems.

  7. Bidirectional effect of magnetic field on electronic thermal transport of metals from all-electron first-principles calculations

    Science.gov (United States)

    Yang, Jia-Yue; Yue, Sheng-Ying; Hu, Ming

    2016-12-01

    Considerable discussions have occurred about the critical role played by free electrons in the transport of heat in pure metals. In principle, any environment that can influence the dynamical behaviors of electrons would have impact on electronic thermal conductivity (κel) of metals. Over the past decades, significant progress and comprehensive understanding have been gained from theoretical, as well as experimental, investigations by taking into account the effects of various conditions, typically temperature, impurities, strain, dimensionality, interface, etc. However, the effect of external magnetic field has received less attention. In this paper, the magnetic-field dependence of electron-phonon scattering, the electron's lifetime, and κel of representative metals (Al, Ni, and Nb) are investigated within the framework of all-electron spin-density functional theory. For Al and Ni, the induced magnetization vector field and difference in electron density under external magnetic-field aggregate toward the center of unit cell, leading to the enhanced electron-phonon scattering, the damped electron's lifetime, and thus the reduced κel. On the contrary, for Nb with strong intrinsic electron-phonon interaction, the electron's lifetime and κel slightly increase as external magnetic field is enhanced. This is mainly attributed to the separately distributed magnetization vector field and difference in electron density along the corner of unit cell. This paper sheds light on the origin of influence of external magnetic field on κel for pure metals and offers a new route for robust manipulation of electronic thermal transport via applying external magnetic field.

  8. Nuclear magnetic resonance study of pure and Ni/Co doped LiFeAs

    Energy Technology Data Exchange (ETDEWEB)

    Grafe, Hans-Joachim; Baek, Seung-Ho; Hammerath, Franziska; Graefe, Uwe; Utz, Yannic; Harnagea, L.; Nacke, Claudia; Aswartham, Saicharan; Wurmehl, Sabine; Buechner, Bernd [Leibniz-Institut fuer Festkoerper- und Werkstoffforschung, Dresden (Germany)

    2011-07-01

    We present Nuclear Magnetic and Nuclear Quadrupole Resonance (NMR/NQR) measurements on pure, Ni and Co doped LiFeAs single crystals. The parent compound LiFeAs exhibits unconventional superconductivity with a transition temperature of about 17 K. Unlike other Fe based superconductors, where superconductivity is induced or stabilized by Co or Ni doping, replacement of Fe by these elements leads to a suppression of the superconducting transition temperature in LiFeAs. In case of Ni doping, a bulk magnetic order is induced below about 160 K. In contrast, for Co doping, the superconducting transition temperature is only reduced, but no magnetic order is observed. We discuss the nature and the origin of this magnetic order and its relation to unconventional superconductivity in pure LiFeAs.

  9. Effect of pulse magnetic field on solidification structure and properties of pure copper

    Institute of Scientific and Technical Information of China (English)

    LIAO Xi-liang; GONG Yong-yong; LI Ren-xing; CHEN Wen-jie; ZHAI Qi-jie

    2007-01-01

    The application of pulse magnetic field to metal solidification is an advanced technique which can remarkably refine solidification structure. In this paper, the effect of pulse magnetic field on solidification structure,mechanical properties and conductivity of pure copper was experimentally investigated. The results showed that the solidification structure transformed from coarse columnar crystal to fine globular crystal with increasing pulse voltage.Increasing pulse voltage also improved the tensile strength. However, with the increase of pulse voltage, the elongation and electrical resistivity firstly decreased, then increased when the pulse voltage beyond a critical value. Moreover,in some conditions, pulse magnetic field can simultaneously improve the conductivity and mechanical property of pure copper.

  10. Parity-time symmetry from stacking purely dielectric and magnetic slabs

    CERN Document Server

    Gear, James; Chu, S T; Rotter, Stefan; Li, Jensen

    2015-01-01

    We show that Parity-time symmetry in matching electric permittivity to magnetic permeability can be established by considering an effective Parity operator involving both mirror symmetry and coupling between electric and magnetic fields. This approach extends the discussion of Parity-time symmetry to the situation with more than one material potential. We show that the band structure of a one-dimensional photonic crystal with alternating purely dielectric and purely magnetic slabs can undergo a phase transition between propagation modes and evanescent modes when the balanced gain/loss parameter is varied. The cross-matching between different material potentials also allows exceptional points of the constitutive matrix to appear in the long wavelength limit where they can be used to construct ultrathin metamaterials with unidirectional reflection.

  11. Spin fluctuation theory of itinerant electron magnetism

    CERN Document Server

    Takahashi, Yoshinori

    2013-01-01

    This volume shows how collective magnetic excitations determine most of  the magnetic properties of itinerant electron magnets. Previous theories were mainly restricted to the Curie-Weiss law temperature dependence of magnetic susceptibilities. Based on the spin amplitude conservation idea including the zero-point fluctuation amplitude, this book shows that the entire temperature and magnetic field dependence of magnetization curves, even in the ground state, is determined by the effect of spin fluctuations. It also shows that the theoretical consequences are largely in agreement with many experimental observations. The readers will therefore gain a new comprehensive perspective of their unified understanding of itinerant electron magnetism.

  12. Study and Demarcating of Electron Magnetic Spectrometer

    Institute of Scientific and Technical Information of China (English)

    LIYe-jun; SHANYu-sheng; TAOYe-zheng; CHENGYou-jian; ZHANGHai-feng

    2003-01-01

    The principle of electron magnetic spectrometer is a moving charged particle circles a central point for the Lorenz force when it moves in a steady magnetic field, at the same time, we consider the influence of gravity excursion, magnetic grads excursion and curvature excursion. Having adopted yoke iron equalizing technology and had magnetic field and gravity field at the same line.

  13. Manipulation of pure spin current in ferromagnetic metals independent of magnetization

    Science.gov (United States)

    Tian, Dai; Li, Yufan; Qu, D.; Huang, S. Y.; Jin, Xiaofeng; Chien, C. L.

    2016-07-01

    Upon the injection of a pure spin current, a ferromagnet, similar to a nonmagnetic metal, also exhibits inverse spin Hall effect (ISHE). We show in Co/Cu/YIG, where the thin Cu layer allows transmission of spin current from YIG into Co but decouples the two ferromagnets, that the interaction between ISHE and ferromagnetic ordering in Co can be unambiguously investigated. By switching on and off the pure spin current contribution, we demonstrate that the ISHE in Co is independent of the direction of the Co magnetization, which clearly suggests that the ISHE in Co is dominated not by the extrinsic impurity scatterings, but from the intrinsic origin.

  14. Electronic Structure of Pure Selenium and Tellurium Chains and Selenium Rings and with Impurities

    Science.gov (United States)

    Maharjan, N. B.; Cho, Hwa-Suck; Scheicher, R. H.

    2005-03-01

    We have studied the electronic structures of pure chain-structured Selenium and Tellurium and with chalcogen impurities as well as ring-structured Selenium both pure and with Tellurium impurity atoms. The Hartree-Fock Cluster Theory procedure combined with many-body perturbation theory procedure has been used. The accuracy of the calculated electronic wave functions is tested by the investigation of ^77Se and ^125Te nuclear quadrupole interaction parameters. Good agreement is found with experiment for the pure systems. For the impurity systems, the agreement is reasonable but suggests the need for inclusion of more extensive relaxation around the impurity atoms. (*) Current Address: Dept. of Physics, Uppsala University, Sweden (**) Also: Dept. of Physics, University of Central Florida, Orlando, Florida

  15. Void formation in pure aluminium irradiated with high-energetic electron beams and gamma-quanta

    DEFF Research Database (Denmark)

    Gan, V. V.; Ozhigou, L. S.; Yamnitsky, V. A.

    1983-01-01

    The spatial distribution of displaced atoms and helium atoms and also the spectra of damaging energies of primary displaced atoms in a thick aluminium target irradiated with electrons of 225 MeV energy were calculated. Pure aluminium (99.9999%) irradiated up to 0.04 dose was studied by electron-m......-microscopy. Voids of size 5 to 40 nm were obtained and their vacancy nature was estimated. The dislocation structure of the material was studied...

  16. Electronic properties of magnetically doped nanotubes

    Indian Academy of Sciences (India)

    Keivan Esfarjani; Z Chen; Y Kawazoe

    2003-01-01

    Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons of the tube screen the magnetization of the dopants: the coupling to the tube is usually antiferromagnetic (except for Cr).

  17. Runaway electrons and magnetic island confinement

    Science.gov (United States)

    Boozer, Allen H.

    2016-08-01

    The breakup of magnetic surfaces is a central feature of ITER planning for the avoidance of damage due to runaway electrons. Rapid thermal quenches, which lead to large accelerating voltages, are thought to be due to magnetic surface breakup. Impurity injection to avoid and to mitigate both halo and runaway electron currents utilizes massive gas injection or shattered pellets. The actual deposition is away from the plasma center, and the breakup of magnetic surfaces is thought to spread the effects of the impurities across the plasma cross section. The breakup of magnetic surfaces would prevent runaway electrons from reaching relativistic energies were it not for the persistence of non-intercepting flux tubes. These are tubes of magnetic field lines that do not intercept the walls. In simulations and in magnetic field models, non-intercepting flux tubes are found to persist near the magnetic axis and in the cores of magnetic islands even when a large scale magnetic surface breakup occurs. As long as a few magnetic surfaces reform before all of the non-intercepting flux tubes dissipate, energetic electrons confined and accelerated in these flux tubes can serve as the seed electrons for a transfer of the overall plasma current from thermal to relativistic carriers. The acceleration of electrons is particularly strong because of the sudden changes in the poloidal flux that naturally occur in a rapid magnetic relaxation. The physics of magnetic islands as non-intercepting flux tubes is studied. Expressions are derived for (1) the size of islands required to confine energetic runaway electrons, (2) the accelerating electric field in an island, (3) the increase or reduction in the size of an island by the runaway electron current, (4) the approximate magnitude of the runaway current in an island, and (5) the time scale for the evolution of an island.

  18. Formation and Dynamics of Vortex Structures in Pure and Gas-Discharge Nonneutral Collisionless Electron Plasmas

    CERN Document Server

    Kervalishvili, N A

    2013-01-01

    The comparative analysis of the results of experimental investigations of the processes of formation, interaction and dynamics of vortex structures in pure electron and gas-discharge electron nonneutral plasmas taking place for the period of time much less than the electron-neutral collision time has been given. The general processes of formation and behavior of vortex structures in these two plasmas were considered. The phenomena, taking place only in one of these plasmas were also considered. It is shown that the existing difference in behavior of vortex structures is caused by different initial states of nonneutral electron plasmas. The role of vortex structures in the processes taking place in nonneutral electron plasma is discussed.

  19. Generation of an ultralong pure longitudinal magnetization needle with high axial homogeneity using an azimuthally polarized beam modulated by pure multi-zone plate phase filter

    Science.gov (United States)

    Yan, Weichao; Nie, Zhongquan; Zhang, Xueru; Wang, Yuxiao; Song, Yinglin

    2017-08-01

    Based on the vector diffraction theory and the inverse Faraday effect in the magneto-optic film, light-induced magnetization distributions, for a high numerical aperture focusing configuration with an azimuthally polarized beam modulated by an optimized pure multi-zone plate phase filter, are investigated. By making use of the compeletely destructive interference of its inter circle with the π phase shift between adjacent sub-annuli, and the capability to extend the constructive interference in the propagating direction through its narrow outer annulus modulated by three misplaced helical phases, an ultralong (107λ ) magnetization needle with both transverse super-resolution (0.37λ ) and uniform axial field strength is achieved in the focal region. The perfect magnetization needle and the accessible method give a guide for ultrahigh density magnetic storage, fabricating magnetic lattices for spin wave operation, as well as atomic trapping.

  20. The effect of electron beam treatment on hydrogen sorption ability of commercially pure titanium

    Energy Technology Data Exchange (ETDEWEB)

    Panin, Alexey V.; Kazachenok, Marina S. [Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk 634021 (Russian Federation); Kretova, Oksana M., E-mail: oksikom@bk.ru [Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk 634021 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk 634050 (Russian Federation); Perevalova, Olga B. [Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk 634021 (Russian Federation); Ivanov, Yurii F. [Institute of High Current Electronics of the Siberian Branch of the Russian Academy of Sciences, Tomsk 634055 (Russian Federation); National Research Tomsk Polytechnic University, Tomsk 634050 (Russian Federation); Lider, Andrey M.; Stepanova, Olga M.; Kroening, Michael H. [National Research Tomsk Polytechnic University, Tomsk 634050 (Russian Federation)

    2013-11-01

    The surface morphology and the microstructure of commercially pure titanium specimens subjected to electron beam treatment with energy density varying from 12 to 25 J/cm{sup 2} were studied using atomic force microscopy and transmission electron microscopy as well as X-ray diffraction analysis. Lamellar α-phase structure of a thin surface layer of the specimens resulted from the treatment was shown to have a great effect on hydrogen sorption ability of the material as well as on hydrogen arrangement in titanium crystal lattice.

  1. Measurements of Dendritic Growth Velocities in Undercooled Melts of Pure Nickel Under Static Magnetic Fields

    Science.gov (United States)

    Gao, Jianrong; Zhang, Zongning; Zhang, Yingjie

    2012-01-01

    Dendritic growth velocities in undercooled melts of pure Ni have been intensively studied over the past fifty years. However, the literature data are at marked variance with the prediction of the widely accepted model for rapid dendritic growth both at small and at large undercoolings. In the present work, bulk melts of pure Ni samples of high purity were undercooled by glass fluxing treatment under a static magnetic field. The recalescence processes of the samples at different undercoolings were recorded using a high-speed camera, and were modeled using a software to determine the dendritic growth velocities. The present data confirmed the effect of melt flow on dendritic growth velocities at undercoolings below 100 K. A comparison of the present data with previous measurements on a lower purity material suggested an effect of impurities on dendritic growth velocities at undercoolings larger than 200 K as well.

  2. Fast instability caused by electron cloud in combined function magnets

    Directory of Open Access Journals (Sweden)

    S. A. Antipov

    2017-04-01

    Full Text Available One of the factors which may limit the intensity in the Fermilab Recycler is a fast transverse instability. It develops within a hundred turns and, in certain conditions, may lead to a beam loss. The high rate of the instability suggests that its cause is electron cloud. We studied the phenomena by observing the dynamics of stable and unstable beams, simulating numerically the buildup of the electron cloud, and developed an analytical model of an electron cloud driven instability with the electrons trapped in combined function dipoles. We found that beam motion can be stabilized by a clearing bunch, which confirms the electron cloud nature of the instability. The clearing suggest electron cloud trapping in Recycler combined function magnets. Numerical simulations show that up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud buildup is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multiturn accumulation allows the electron cloud to reach final intensities orders of magnitude greater than in a pure dipole. The estimated resulting instability growth time of about 30 revolutions and the mode frequency of 0.4 MHz are consistent with experimental observations and agree with the simulation in the pei code. The created instability model allows investigating the beam stability for the future intensity upgrades.

  3. Fast Instability Caused by Electron Cloud in Combined Function Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, S. A. [Chicago U.; Adamson, P. [Fermilab; Burov, A. [Fermilab; Nagaitsev, S. [Fermilab; Yang, M. J. [Fermilab

    2016-12-12

    One of the factors which may limit the intensity in the Fermilab Recycler is a fast transverse instability. It develops within a hundred turns and, in certain conditions, may lead to a beam loss. The high rate of the instability suggest that its cause is electron cloud. We studied the phenomena by observing the dynamics of stable and unstable beam, simulating numerically the build-up of the electron cloud, and developed an analytical model of an electron cloud driven instability with the electrons trapped in combined function di-poles. We found that beam motion can be stabilized by a clearing bunch, which confirms the electron cloud nature of the instability. The clearing suggest electron cloud trapping in Recycler combined function mag-nets. Numerical simulations show that up to 1% of the particles can be trapped by the magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a Recycler combined function dipole this multi-turn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The estimated resulting instability growth rate of about 30 revolutions and the mode fre-quency of 0.4 MHz are consistent with experimental observations and agree with the simulation in the PEI code. The created instability model allows investigating the beam stability for the future intensity upgrades.

  4. Electron acceleration by magnetic collapse during decoupling

    Science.gov (United States)

    Bennet, Euan D.; Potts, Hugh E.; Teodoro, Luis F. A.; Diver, Declan A.

    2014-12-01

    This paper identifies the non-equilibrium evolution of magnetic field structures at the onset of large-scale recombination of an inhomogeneously ionized plasma. The context for this is the Universe during the epoch of recombination. The electromagnetic treatment of this phase transition can produce energetic electrons scattered throughout the Universe, localized near the edges of magnetic domains. This is confirmed by a numerical simulation in which a magnetic domain is modelled as a uniform field region produced by a thin surrounding current sheet. Conduction currents sustaining the magnetic structure are removed as the charges comprising them combine into neutrals. The induced electric field accompanying the magnetic collapse is able to accelerate ambient stationary electrons (that is, electrons not participating in the current sheet) to energies of up to order 10keV. This is consistent with theoretical predictions. The localized electron acceleration leads to local imbalances of charge which has implications for charge separation in the early Universe.

  5. Electronic structures and physical properties of pure Cr, Mo and W

    Institute of Scientific and Technical Information of China (English)

    谢佑卿; 邓永平; 刘心笔

    2003-01-01

    Using the one atom theory, the electronic structures of pure Cr, Mo and W with bcc structure were determined respectively as: [Ar](3dc)3.32(3dn)2.26(4sc)0.25(4sf)0.17, [Kr](4dc)4.23(4dn)1.48(5sc)0.02(5sf)0.27 and [Xe](5dc)5.16(6sc)0.25(6sf)0.59.The electronic structures of these metals with hcp and fcc structures and liquid state were also studied. According to their electronic structures, the relationship between the electronic structure and crystalline structure was explained qualitatively and the relationship between the difference of mechanical properties and transport properties of pure Cr, Mo and W with bcc structure and their electronic structures was also explained qualitatively; the lattice constants, binding energy, potential curves, elasticities and the temperature dependence of the linear thermal expansion coefficient of bcc-Cr, bcc-Mo and bcc-W were calculated quantitatively.

  6. Electron Acceleration in Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; LU Quan-Ming; WANG Shui; FU Xiang-Rong

    2005-01-01

    @@ A 21/2-dimensional electromagnetic particle-in-cell (PIC) simulation code is used to investigate the electron acceleration in collisionless magnetic reconnection. The results show that the electrons are accelerated in the diffusion region near the X point, and the acceleration process can be roughly divided into two procedures: firstly the electrons are accelerated in the z direction due to the electric field in the negative z direction. Then the electrons gyrate surrounding the magnetic field with the action of the Lorentz force, through this procedure the electrons reach higher velocity in the x direction and then flow out of the diffusion region. After being accelerated away from the diffusion region, part of electrons is trapped near the O point, and the other part of electrons flows into plasma sheet boundary layer along the magnetic field.

  7. Seeking large-scale magnetic fields in a pure-disk dwarf galaxy NGC 2976

    CERN Document Server

    Drzazga, R T; Heald, G H; Elstner, D; Gallagher, J S

    2016-01-01

    It is still unknown how magnetic field-generation mechanisms could operate in low-mass dwarf galaxies. Here, we present a detailed study of a nearby pure-disk dwarf galaxy NGC 2976. Unlike previously observed dwarf objects, this galaxy possesses a clearly defined disk. For the purpose of our studies, we performed deep multi-frequency polarimetric observations of NGC 2976 with the VLA and Effelsberg radio telescopes. Additionally, we supplement them with re-imaged data from the WSRT-SINGS survey. The magnetic field morphology discovered in NGC 2976 consists of a southern polarized ridge. This structure does not seem to be due to just a pure large-scale dynamo process (possibly cosmic-ray driven) at work in this object, as indicated by the RM data and dynamo number calculations. Instead, the field of NGC 2976 is modified by past gravitational interactions and possibly also by ram pressure inside the M 81 galaxy group environment. The estimates of total (7 muG) and ordered (3 muG) magnetic field strengths, as we...

  8. Electronic structure and magnetism in actinide compounds

    Energy Technology Data Exchange (ETDEWEB)

    Durakiewicz, T. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)]. E-mail: tomasz@lanl.gov; Joyce, J.J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lander, G.H. [JRC, Institute of Transuranium Elements, Postfach 2340, 76125 Karlsruhe (Germany); Olson, C.G. [Ames Laboratory, Iowa State University, Ames, Iowa 5011 (United States); Butterfield, M.T. [Lawrence Livermoore National Laboratory, Livermoore, CA 94550 (United States); Guziewicz, E. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Batista, C.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Arko, A.J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Morales, L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Mattenberger, K. [Laboratorium fur Festkorperphysik, ETH, CH-8093, Zurich (Switzerland); Vogt, O. [Laboratorium fur Festkorperphysik, ETH, CH-8093, Zurich (Switzerland)

    2006-05-01

    A close relationship between electronic structure and magnetic properties is observed in actinide compounds. The exact nature of this relationship is under investigation. We present examples of a direct link between electronic structure and ordered magnetic moment and/or magnetization. Specifically, results obtained for cubic U, Np and Pu compounds and quasi-2D U compounds are be presented. In the case of cubic compounds, a direct relationship between binding energy of valence band features and magnetic moment will be discussed. A Stoner-like mechanism and simple mean-field explanation is proposed for ferromagnetic UTe.

  9. Magnetocrystalline anisotropy of pure magnetic semiconductors of MnGeP2 and MnGeAs2: A first-principles study

    Science.gov (United States)

    Cha, Gi-Beom; Yun, Won Seok; Hong, Soon Cheol

    2016-12-01

    In this study, we use the all-electron full-potential linearized augmented plane wave method to investigate the magnetocrystalline anisotropies of pure magnetic MnGeP2 and MnGeAs2 semiconductors. Both MnGeP2 and MnGeAs2 have been calculated to be more stable in their antiferromagnetic (AFM) states than in their ferromagnetic (FM) states, with energy differences of about 230 and 190 meV/Mn, respectively. MnGeP2 and MnGeAs2 exhibit a positive EMCA (magnetization along the z axis) of +52.3 and +122.6 μeV/Mn in their AFM magnetic ground states with a negative EMCA (magnetization on the xy plane) of -71.1 and -177.8 μeV/Mn in their FM states. The EMCA behaviors are analyzed in terms of the electronic structure.

  10. Purification-induced sidewall functionalization of magnetically pure single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Schoenfelder, R [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Ruemmeli, M H [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Gruner, W [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Loeffler, M [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Acker, J [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Hoffmann, V [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Gemming, T [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Buechner, B [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany); Pichler, T [IFW Dresden, PO Box 270116, D-01171 Dresden (Germany)

    2007-09-19

    In this contribution we present systematic studies on the purification and subsequent functionalization of magnetically pure single-walled carbon nanotubes. We show through a combination of burning treatments and microwave digester treatments in aqua regia that single-walled carbon nanotubes can be purified without incurring any damage, with 90 wt% of catalyst material being removed. It is also shown that multiple microwave digester treatments lead to incremental functionalization of the nanotubes. The obtained functional groups are easily removed by annealing the sample in vacuum.

  11. Magnetic neutrino scattering on atomic electrons revisited

    CERN Document Server

    Kouzakov, Konstantin A

    2010-01-01

    We reexamine the role of electron binding effects in the inelastic neutrino-atom scattering induced by the neutrino magnetic moment. The differential cross section of the process is presented as a sum of the longitudinal and transverse components, according to whether the force that the neutrino magnetic moment exerts on electrons is parallel or perpendicular to momentum transfer. The atomic electrons are treated nonrelativistically. On this basis, it is shown that the recently published theoretical studies devoted to the magnetic neutrino scattering on atoms are deficient. Numerical calculations are performed for ionization of a hydrogenlike Ge$^{+31}$ ion by neutrino impact.

  12. Controlling bi-anisotropy in infrared metamaterials using three-dimensional split-ring-resonators for purely magnetic resonance.

    Science.gov (United States)

    Moritake, Yuto; Tanaka, Takuo

    2017-07-27

    We propose and demonstrate the strategy to control bi-anisotropic response in three-dimensional split-ring-resonators (3D-SRRs) array for purely magnetic resonance in the mid-infrared region. By using a metal-stress-driven self-folding method, inversion symmetry along a propagation axis of 3D-SRRs was controlled. The inversion symmetry of 3D-SRRs realized non-bi-anisotropic response of a magnetic resonant mode at around 10 μm in wavelength resulting in purely magnetic resonance with high transmission of 70%. Highly transparent purely magnetic artificial elements demonstrated in this study will be a key component for functional applications using artificial magnetism at the optical frequencies.

  13. Magnetism and Raman Spectroscopy of Pristine and Hydrogenated TaSe2 Monolayer tuned by Tensile and Pure Shear Strain

    Science.gov (United States)

    Chowdhury, Sugata; Simpson, Jeffrey; Einstein, T. L.; Walker, Angela R. Hight

    2D-materials with controllable optical, electronic and magnetic properties are desirable for novel nanodevices. Here we studied these properties for both pristine and hydrogenated TaSe2 (TaSe2-H) monolayer (ML) in the framework of DFT using the PAW method. We considered uniaxial and biaxial tensile strain, as well as shear strain along the basal planes in the range between 1% and 16%. Previous theoretical works (e.g.) considered only symmetrical biaxial tensile. Pristine ML is ferromagnetic for uniaxial tensile strain along ◯ or ŷ. For tensile strain in ŷ, the calculated magnetic moments of the Ta atoms are twice those for the same strain in ◯. Under pure shear strain (expansion along ŷ and compression along ◯), a pristine ML is ferromagnetic, but becomes non-magnetic when the strain directions are interchanged. Due to carrier-mediated double-exchange, the pristine ML is ferromagnetic when the Se-Ta-Se bond angle is < 82° and the ML thickness is < 3.25Å. We find that all Raman-active phonon modes show obvious red-shifting due to bond elongation and the E2 modes degeneracy is lifted as strain increases. For a TaSe2-H ML, the same trends were observed. Results show the ability to tune the properties of 2D-materials.

  14. Structural and magnetic properties of pure and Ca-doped LaCoO3 nanopowders obtained by a sol-gel route.

    Science.gov (United States)

    Armelao, Lidia; Barreca, Davide; Bottaro, Gregorio; Maragno, Cinzia; Tondello, Eugenio; Caneschi, Andrea; Sangregorio, Claudio; Gialanella, Stefano

    2006-04-01

    Pure and Ca-doped LaCoO3 nanopowders were prepared by a non-alkoxidic sol-gel route using cobalt(II) acetate, lanthanum(III) nitrate and calcium(II) acetate as oxide precursors. The structural evolution and magnetic properties of the samples were studied as a function of thermal treatments in air up to 1273 K. In particular, the microstructure and composition of the systems were analyzed by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-ray Photoelectron Spectroscopy (XPS). Both pure and calcium-doped samples annealing at 973 K resulted in the formation of cubic LaCoO3 (average crystallite size <30 nm). This phase was fully retained in the calcium-doped materials even after annealing at higher temperatures, whereas a transition to the rhomboedral polymorph was detected in the pure samples at 1073 K. The magnetic behavior of the nanopowders was investigated as a function of temperature and applied field using both dynamic and static susceptibility measurements. Pure lanthanum cobaltite samples underwent a transition to an ordered state at 88 K, and their magnetic properties changed as a function of thermal treatments. As concerns calcium-doped samples, they ordered ferromagnetically at 171 and 185 K depending on the annealing temperature and displayed open hysteresis loops with coercive fields as large as 1.75 T at low temperatures.

  15. Entanglement Entropy of Magnetic Electron Stars

    CERN Document Server

    Albash, Tameem; MacDonald, Scott

    2015-01-01

    We study the behavior of the entanglement entropy in $(2+1)$--dimensional strongly coupled theories via the AdS/CFT correspondence. We consider theories at a finite charge density with a magnetic field, with their holographic dual being Einstein-Maxwell-Dilaton theory in four dimensional anti--de Sitter gravity. Restricting to black hole and electron star solutions at zero temperature in the presence of a background magnetic field, we compute their holographic entanglement entropy using the Ryu-Takayanagi prescription for both strip and disk geometries. In the case of the electric or magnetic zero temperature black holes, we are able to confirm that the entanglement entropy is invariant under electric-magnetic duality. In the case of the electron star with a finite magnetic field, for the strip geometry, we find a discontinuity in the first derivative of the entanglement entropy as the strip width is increased.

  16. Magnetic properties of pure and Fe doped HoCrO3 thin films fabricated via a solution route

    Science.gov (United States)

    Yin, Shiqi; Sauyet, Theodore; Guild, Curt; Suib, S. L.; Jain, Menka

    2017-04-01

    Multiferroic properties of orthorhombically distorted perovskite rare-earth chromites, such as HoCrO3, are being investigated extensively in recent years. In the present work, we report on the effect of Fe substitution on the magnetic properties of HoCrO3 thin films. Thin films of HoCrO3 and HoCr0.7Fe0.3O3 were fabricated via a solution route on platinized silicon substrates. Structural properties of the films were evaluated by X-ray diffraction and Raman spectroscopy techniques. The surface morphology and cross-sections of the films were examined using scanning electron microscopy. Optical band gaps of pure and Fe doped HoCrO3 films are found to be 3.45 eV and 3.39 eV, respectively. The magnetization measurements show that the Néel temperatures (where Cr3+ orders) for the HoCrO3 and HoCr0.7Fe0.3O3 films are 134 and 148 K, respectively. In a magnetic field of 2 T, the maximum entropy change and relative cooling power, two parameters to evaluate the magnetocaloric properties of a material, were 0.813 J/kg K at 11 K and 21.1 J/kg for HoCrO3 film, in comparison with 0.748 J/kg K at 15 K and 26.8 J/kg for HoCr0.7Fe0.3O3 film. To our knowledge, this is the first work exploring the band gap and magnetocaloric properties of rare-earth chromite thin films. These findings should inspire the development of rare-earth chromite thin films for temperature control of nanoscale electronic devices and sensors in the low temperature region (< 30 K).

  17. Electronic, magnetic, and optical materials

    CERN Document Server

    Fulay, Pradeep

    2013-01-01

    Technological aspects of ferroelectric, piezoelectric and pyroelectric materials are discussed in detail, in a way that should allow the reader to select an optimal material for a particular application. The basics of magnetostatics are described clearly, as are a wide range of magnetic properties of materials … .-Tony Harker, Department of Physics and Astronomy, University College London

  18. Magnetic monopole field exposed by electrons

    CERN Document Server

    Béché, A; Van Tendeloo, G; Verbeeck, J

    2013-01-01

    Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

  19. Characterization of magnetic domain walls using electron magnetic chiral dichroism

    Directory of Open Access Journals (Sweden)

    Ren Chao Che, Chong Yun Liang, Xiang He, Hai Hua Liu and Xiao Feng Duan

    2011-01-01

    Full Text Available Domain walls and spin states of permalloy were investigated by electron magnetic chiral dichroism (EMCD technique in Lorentz imaging mode using a JEM-2100F transmission electron microscope. EMCD signals from both Fe and Ni L3,2 edges were detected from the Bloch lines but not from the adjacent main wall. The magnetic polarity orientation of the circular Bloch line is opposite to that of the cross Bloch line. The orientations of Fe and Ni spins are parallel rather than antiparallel, both at the cross Bloch line and circular Bloch line.

  20. Electron holes in inhomogeneous magnetic field: electron heating and electron hole evolution

    Science.gov (United States)

    Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton; Drake, James

    2016-04-01

    Electron holes are electrostatic non-linear structures widely observed in the space plasma, e.g., in reconnecting current sheets, collisionless bow shocks, Earth auroral region and outer radiation belt etc. In the present paper we analyze the process of energy exchange between trapped electrons, untrapped electrons and electron hole propagating in weakly inhomogeneous magnetic field. We show that as electron hole propagates into the region with stronger magnetic field, trapped electrons are heated due to conservation of the first adiabatic invariant. At the same time electron hole may grow or dissipate in dependence on peculiarities of distribution functions of trapped and resonant untrapped electrons. The energy gain of trapped electrons is due to energy losses of resonant electrons and/or decrease of electron hole energy (electrostatic energy and kinetic energy of non-resonant electrons). We stress that taking into account the energy exchange with resonant untrapped electrons increases the heating factor of trapped electrons that is proportional to the magnetic field magnitude in the region up to what electron holes survive. We illustrate the suggested mechanism for H. Schamel's electron holes and show that during propagation along a positive magnetic field gradient their amplitude should grow. Neglect of energy exchange with resonant untrapped electrons would result electron hole dissipation with only modest heating factor of trapped electrons. We argue that the suggested mechanism may be responsible for generation of energetic electrons in the space plasma.

  1. Electronic structure and magnetism of complex materials

    CERN Document Server

    Papaconstantopoulos, D A

    2003-01-01

    Recent developments in electronic structure theory have led to a new understanding of magnetic materials at the microscopic level. This enables a truly first-principles approach to investigations of technologically important magnetic materials. Among these advances have been practical schemes for handling non-collinear magnetic systems, including relativity, understanding of the origins and role of orbital magnetism within band structure formalisms, density functional approaches for magnons and low-lying spin excitations, understanding of the interplay of orbital, spin and lattice orderings in complex oxides, transport theories for layered systems, and the theory of magnetic interactions in doped semiconductors. The book covers these recent developments with review articles by some of the main originators of these advances.

  2. Magnetic and electronic properties of ruthenocuprates

    Science.gov (United States)

    Hirai, Y.; Schneider, M. L.; Frazer, B. H.; Rast, S.; Onellion, M.; Asaf, U.; Felner, I.; Nowik, I.; Ali, N.; Roy, S.; Prester, M.; Drobac, D.; Zivkovic, I.; Perfetti, L.; Reginelli, A.; Ariosa, D.; Margaritondo, G.

    2001-03-01

    We present data on as-prepared, oxygen annealed, and hydrogen loaded ruthenocuprate samples. We include: * magnetic measurements: magnetization,^1 ac susceptibility; * electronic properties: x-ray photoemission,^1,2 x-ray absorption^3; * the effects of hydrogen loading and of oxygen annealing. We concentrate on the changes of magnetic properties with carrier concentration, and discuss the superconducting properties only briefly. ^1B.H. Frazer et.al., Phys. Rev. B. ^2B.H. Frazer et.al., Euro. J. Phys., in press (2000). ^3Y. Hirai et.al., submitted.

  3. Electron transmission through a periodically driven graphene magnetic barrier

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, R., E-mail: rbiswas.pkc@gmail.com [Department of Physics, P. K. College, Contai, Purba Medinipur, West Bengal – 721401 (India); Maiti, S. [Ajodhya Hills G.S.A.T High School, Ajodhya, Purulia, West Bengal – 723152 (India); Mukhopadhyay, S. [Purulia Zilla School, Dulmi Nadiha, Purulia, West Bengal – 723102 (India); Sinha, C. [Department of Physics, P. K. College, Contai, Purba Medinipur, West Bengal – 721401 (India); Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur – 700032 (India)

    2017-05-10

    Electronic transport through graphene magnetic barriers is studied theoretically in presence of an external time harmonic scalar potential in the framework of non-perturbative Landau–Floquet Formalism. The oscillating field mostly suppresses the transmission for rectangular magnetic barrier structure and exhibits the Fano resonance for multiphoton processes due to the presence of bound state inside the barrier. While, for a pair of delta function barriers of larger separation, the oscillating potential suppresses the usual Fabry–Perot oscillations in the transmission and a new type of asymmetric Fano resonance is noted for smaller separation, occurring due to extended states between the barriers. - Highlights: • Tunnelling of the Dirac Fermions through oscillating pure magnetic barriers is reported for the first time. • The high energy transmission through a graphene magnetic barrier is suppressed by the application of time periodic modulation. • Suppression of the Fabry Perot transmission is noted due to the application of an external time harmonic potential. • Two kinds of the Fano resonances are noted in transmission through a pair of modulated δ-function magnetic barriers.

  4. Electron accumulation layer in ultrastrong magnetic field

    Science.gov (United States)

    Sammon, M.; Fu, Han; Shklovskii, B. I.

    2017-02-01

    When a three-dimensional electron gas is subjected to a very strong magnetic field, it can reach a quasi-onedimensional state in which all electrons occupy the lowest Landau level. This state is referred to as the extreme quantum limit ( EQL ) and has been studied in the physics of pulsars and bulk semiconductors. Here we present a theory of the EQL phase in electron accumulation layers created by an external electric field E at the surface of a semiconductor with a large Bohr radius such as InSb , PbTe , SrTiO 3 ( STO ) , and particularly in the LaA 1 O 3 / SrTiO 3 ( LAO / STO ) heterostructure. The phase diagram of the electron gas in the plane of the magnetic field strength and the electron surface concentration is found for different orientations of the magnetic field. We find that in addition to the quasi-classical metallic phase ( M ), there is a metallic EQL phase, as well as an insulating Wigner crystal state ( WC ). Within the EQL phase, the Thomas-Fermi approximation is used to find the electron density and the electrostatic potential profiles of the accumulation layer. Additionally, the quantum capacitance for each phase is calculated as a tool for experimental study of these phase diagrams.

  5. Magnetic focusing in triangular electron billiards

    DEFF Research Database (Denmark)

    Bøggild, Peter; Kristensen, A.; Lindelof, Poul Erik

    1999-01-01

    The classical ballistic magnetotransport in triangular electron billiards fabricated in a high mobility GaAs heterostructure has been studied at 4.2 K. The sample geometry may be viewed as a double-slit structure with a skewed injection angle. We observe a striking cancellation of the magnetic...

  6. Numerical methods in electron magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Soernes, A.R

    1998-07-01

    The focal point of the thesis is the development and use of numerical methods in the analysis, simulation and interpretation of Electron Magnetic Resonance experiments on free radicals in solids to uncover the structure, the dynamics and the environment of the system.

  7. Chiral magnetism of magnetic adatoms generated by Rashba electrons

    Science.gov (United States)

    Bouaziz, Juba; dos Santos Dias, Manuel; Ziane, Abdelhamid; Benakki, Mouloud; Blügel, Stefan; Lounis, Samir

    2017-02-01

    We investigate long-range chiral magnetic interactions among adatoms mediated by surface states spin-splitted by spin–orbit coupling. Using the Rashba model, the tensor of exchange interactions is extracted wherein a thepseudo-dipolar interaction is found, in addition to the usual isotropic exchange interaction and the Dzyaloshinskii–Moriya interaction. We find that, despite the latter interaction, collinear magnetic states can still be stabilized by the pseudo-dipolar interaction. The interadatom distance controls the strength of these terms, which we exploit to design chiral magnetism in Fe nanostructures deposited on a Au(111) surface. We demonstrate that these magnetic interactions are related to superpositions of the out-of-plane and in-plane components of the skyrmionic magnetic waves induced by the adatoms in the surrounding electron gas. We show that, even if the interatomic distance is large, the size and shape of the nanostructures dramatically impacts on the strength of the magnetic interactions, thereby affecting the magnetic ground state. We also derive an appealing connection between the isotropic exchange interaction and the Dzyaloshinskii–Moriya interaction, which relates the latter to the first-order change of the former with respect to spin–orbit coupling. This implies that the chirality defined by the direction of the Dzyaloshinskii–Moriya vector is driven by the variation of the isotropic exchange interaction due to the spin–orbit interaction.

  8. Investigation of pure and Co{sup 2+}-doped ZnO quantum dot electronic structures using the density functional theory: choosing the right functional

    Energy Technology Data Exchange (ETDEWEB)

    Badaeva, Ekaterina; Feng Yong; Gamelin, Daniel R; Li Xiaosong [Department of Chemistry, University of Washington, Seattle, WA 98195-1700 (United States)], E-mail: li@chem.washington.edu

    2008-05-15

    The electronic structures of pure and Co{sup 2+}-doped ZnO quantum dots (QDs) with sizes up to 300 atoms were investigated using three different density functional theory approximations: local spin density approximation (LSDA), gradient-corrected Perdew-Burke-Ernzerhof (PBE) and the hybrid PBE1 functionals with LANL2DZ pseudo-potential and associated basis set. Qualitative agreement among the three methods is found for the pure ZnO nanostructures, but only the hybrid functional reproduces the correct bandgap energies quantitatively. For Co{sup 2+}-doped ZnO QDs, both LSDA and PBE incorrectly model interactions between Co{sup 2+} d levels and the valence band of ZnO, which will strongly impair predictions of dopant-carrier magnetic exchange interactions based on such computational results. Experimental observations are reproduced well in calculations at the hybrid PBE1 level of theory, making this the method of choice for exploring the magnetism of transition metal ions in ZnO QDs computationally. The qualitative features of the Co{sup 2+} 3d levels do not change appreciably with changes in cluster size over the range examined, leading to size-dependent dopant-band edge energy differences. The results presented here thus provide an experimentally calibrated framework for future ab initio descriptions of dopant-carrier and dopant-dopant magnetic exchange interactions in diluted magnetic semiconductors (DMS) nanocrystals.

  9. Nonlinear Electron Waves in Strongly Magnetized Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens

    1980-01-01

    dynamics in the analysis is also demonstrated. As a particular case the authors investigate nonlinear waves in a strongly magnetized plasma filled wave-guide, where the effects of finite geometry are important. The relevance of this problem to laboratory experiments is discussed.......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. Highly conductive and pure gold nanostructures grown by electron beam induced deposition

    Science.gov (United States)

    Shawrav, Mostafa M.; Taus, Philipp; Wanzenboeck, Heinz D.; Schinnerl, M.; Stöger-Pollach, M.; Schwarz, S.; Steiger-Thirsfeld, A.; Bertagnolli, Emmerich

    2016-09-01

    This work introduces an additive direct-write nanofabrication technique for producing extremely conductive gold nanostructures from a commercial metalorganic precursor. Gold content of 91 atomic % (at. %) was achieved by using water as an oxidative enhancer during direct-write deposition. A model was developed based on the deposition rate and the chemical composition, and it explains the surface processes that lead to the increases in gold purity and deposition yield. Co-injection of an oxidative enhancer enabled Focused Electron Beam Induced Deposition (FEBID)—a maskless, resistless deposition method for three dimensional (3D) nanostructures—to directly yield pure gold in a single process step, without post-deposition purification. Gold nanowires displayed resistivity down to 8.8 μΩ cm. This is the highest conductivity achieved so far from FEBID and it opens the possibility of applications in nanoelectronics, such as direct-write contacts to nanomaterials. The increased gold deposition yield and the ultralow carbon level will facilitate future applications such as the fabrication of 3D nanostructures in nanoplasmonics and biomolecule immobilization.

  11. Studies on Electronic Structure and Magnetic Properties of an Organic Magnet with Metallic Mn2+ and Cu2+ Ions

    Institute of Scientific and Technical Information of China (English)

    YAO Jian-Guo; PENG Guang-Xiong

    2004-01-01

    The electronic structure and the magnetic properties of the non-pure organic ferromagnetic compound MnCu(pbaOH)(H2O)3 with pbaOH = 2-hydroxy-1, 3-propylenebis (oxamato) are studied by using the density-functional theory with local-spin-density approximation. The density of states, total energy, and the spin magnetic moment are calculated. The calculations reveal that the compound MnCu(pbaOH)(H20)3 has a stable metal-ferromagnetic ground state, and the spin magnetic moment per molecule is 2.208 μB, and the spin magnetic moment is mainly from Mn ion and Cu ion. An antiferromagnetic order is expected and the antiferromagnetic exchange interaction of d-electrons of Cu and Mn passes through the antiferromagnetic interaction between the adjacent C, O, and N atoms along the path linking the atoms Cu and Mn.

  12. Electron cooling device without bending magnets

    Science.gov (United States)

    Sharapa, A. N.; Shemyakin, A. V.

    1993-11-01

    The scheme of an axisymmetric electron cooling device without bending magnets is proposed. Solutions for the most important elements, i.e., a gun and a recuperator, are considered. The main characteristics of the recuperator of the Faraday cup type having a reflector and a gun with a ring emitter are explored. In the gun, the beam is formed, the diameter of which is 40 mm and the dimension of a disturbance region is several millimeters.

  13. Fast electron bremsstrahlung in axisymmetric magnetic configuration

    Science.gov (United States)

    Peysson, Y.; Decker, J.

    2008-09-01

    The nonthermal bremsstrahlung is calculated in a plasma with arbitrary axisymmetric magnetic configuration, taking into account the relativistic angular anisotropy of the radiation cross section at high photon energies, the helical winding of the field lines on the magnetic flux surfaces, and the poloidal variation of the electron distribution function including particle trapping effects. The fast electron dynamics during current drive in tokamaks and reverse field pinches can be investigated in detail by coupling this calculation to a bounce-averaged relativistic Fokker-Planck solver, which calculates the electron distribution function. The asymmetry between high- and low-field side hard x-ray emission intensity that has been measured on the Tore-Supra tokamak [Equipe TORE SUPRA, in Proceedings of the 15th Conference on Plasma Physics and Controlled Nuclear Fusion Research, Seville (International Atomic Energy Agency, Vienna, 1995) Vol. 1, IAEA-CN-60/A1-5 (Institute of Physics, Bristol, U.K., 1995), p. 105] is explained for the first time by the role of trapped electrons. A much stronger poloidal asymmetry is predicted for the line-integrated fast electron bremsstrahlung in the poloidal plane of the Madison Symmetric Torus [R. N. Dexter et al., Fusion Tech. 19, 131 (1991)], since the helical winding of the magnetic field lines is much larger for a reverse field pinch configuration. In this case, the hard x-ray emission is no longer a flux surface quantity, which prevents local reconstructions using a standard Abel inversion, whatever the geometrical arrangement of the lines of sight.

  14. Effects of magnetic annealing on structure and multiferroic properties of pure and dysprosium substituted BiFeO 3

    KAUST Repository

    Zhang, Shuxia

    2012-07-01

    In this work, the effects of magnetic annealing on crystal structure and multiferroic properties of BiFeO 3 and Bi 0.85Dy 0.15FeO 3 have been investigated. It is found that the X-ray diffraction patterns of pure BiFeO 3 samples are obviously broadened after magnetic annealing, whereas those of Bi 0.85Dy 0.15FeO 3 samples are almost unchanged. Magnetic field annealing did not affect the magnetic properties of these two kinds of samples much. However, ferroelectric properties of the two materials exhibited different behaviors after magnetic field annealing. For pure BiFeO 3 samples, the remnant polarizations (P r) are suppressed; in contrast, for Bi 0.85Dy 0.15FeO 3 samples, P r is greatly enhanced. Possible mechanisms for the effects of magnetic field annealing have been discussed. © 2012 Elsevier B.V. All rights reserved.

  15. Structural, electronic, and hyperfine properties of pure and Ta-doped m-ZrO2

    DEFF Research Database (Denmark)

    Taylor, M.A.; Alonso, R.E.; Errico, L.A.

    2012-01-01

    A combination of experiments and ab initio quantum-mechanical calculations has been applied to examine electronic, structural, and hyperfine interactions in pure and Ta-doped zirconium dioxide in its monoclinic phase (m-ZrO2). From the theoretical point of view, the full-potential linear augmented...

  16. Collisional relaxation of a strongly magnetized two-species pure ion plasma

    Energy Technology Data Exchange (ETDEWEB)

    Chim, Chi Yung; O’Neil, Thomas M.; Dubin, Daniel H. [Department of Physics, University of California at San Diego, La Jolla, California 92093 (United States)

    2014-04-15

    The collisional relaxation of a strongly magnetized pure ion plasma that is composed of two species with slightly different masses is discussed. We have in mind two isotopes of the same singly ionized atom. Parameters are assumed to be ordered as Ω{sub 1},Ω{sub 2}≫|Ω{sub 1}−Ω{sub 2}|≫v{sup ¯}{sub ij}/b{sup ¯} and v{sup ¯}{sub ⊥j}/Ω{sub j}≪b{sup ¯}, where Ω{sub 1} and Ω{sub 2} are two cyclotron frequencies, v{sup ¯}{sub ij}=√(T{sub ∥}/μ{sub ij}) is the relative parallel thermal velocity characterizing collisions between particles of species i and j, and b{sup ¯}=2e{sup 2}/T{sub ∥} is the classical distance of closest approach for such collisions, and v{sup ¯}{sub ⊥j}/Ω{sub j}=√(2T{sub ⊥j}/m{sub j})/Ω{sub j} is the characteristic cyclotron radius for particles of species j. Here, μ{sub ij} is the reduced mass for the two particles, and T{sub ∥} and T{sub ⊥j} are temperatures that characterize velocity components parallel and perpendicular to the magnetic field. For this ordering, the total cyclotron action for the two species, I{sub 1}=∑{sub i∈1}m{sub 1}v{sub ⊥i}{sup 2}/(2Ω{sub 1}) and I{sub 2}=∑{sub i∈2}m{sub 2}v{sub ⊥i}{sup 2}/(2Ω{sub 2}) are adiabatic invariants that constrain the collisional dynamics. On the timescale of a few collisions, entropy is maximized subject to the constancy of the total Hamiltonian H and the two actions I{sub 1} and I{sub 2}, yielding a modified Gibbs distribution of the form exp[−H/T{sub ∥}−α{sub 1}I{sub 1}−α{sub 2}I{sub 2}]. Here, the α{sub j}’s are related to T{sub ∥} and T{sub ⊥j} through T{sub ⊥j}=(1/T{sub ∥}+α{sub j}/Ω{sub j}){sup −1}. Collisional relaxation to the usual Gibbs distribution, exp[−H/T{sub ∥}], takes place on two timescales. On a timescale longer than the collisional timescale by a factor of (b{sup ¯2}Ω{sub 1}{sup 2}/v{sup ¯}{sub 11}{sup 2})exp(5[3π(b{sup ¯}|Ω{sub 1}−Ω{sub 2}|/v{sup ¯}{sub 12})]{sup 2/5}/6), the two

  17. Proliferation of mouse fibroblast-like and osteoblast-like cells on pure titanium films manufactured by electron beam melting.

    Science.gov (United States)

    Kawase, Mayu; Hayashi, Tatsuhide; Asakura, Masaki; Tomino, Masafumi; Mieki, Akimichi; Kawai, Tatsushi

    2016-10-01

    The physical characteristics and biological compatibility of surfaces produced by electron beam melting (EBM) are not well known. In particular, there are not many reports on biocompatibility qualities. In this study, pure Ti films were manufactured using EBM. While it is reported that moderately hydrophilic biomaterial surfaces display improved cell growth and biocompatibility, contact angle measurements on the EBM-produced pure Ti films showed slight hydrophobicity. Nonetheless, we found the cell count of both fibroblast-like cells (L929) and osteoblast-like cells (MC3T3-E1) increased on pure Ti films, especially the MC3T3-E1, which increased more than that of the control. In addition, the morphology of L929 and MC3T3-E1 was polygonal and spindle-shaped and the cytoskeleton was well developed in the pure Ti surface groups. Upon staining with Alizarin red S, a slight calcium deposition was observed and this level gradually rose to a remarkable level. These results indicate that pure Ti films manufactured by EBM have good biocompatibility and could be widely applied as biomedical materials in the near future. © 2016 International Federation for Cell Biology.

  18. In situ transmission electron microscopy for magnetic nanostructures

    DEFF Research Database (Denmark)

    Ngo, Duc-The; Kuhn, Luise Theil

    2016-01-01

    Nanomagnetism is a subject of great interest because of both application and fundamental aspects in which understanding of the physical and electromagnetic structure of magnetic nanostructures is essential to explore the magnetic properties. Transmission electron microscopy (TEM) is a powerful tool......-structure correlation. This paper aims at reviewing and discussing in situ TEM magnetic imaging studies, including Lorentz microscopy and electron holography in TEM, applied to the research of magnetic nanostructures....

  19. On the advantages of spring magnets compared to pure FePt: Strategy for rare-earth free permanent magnets following a bottom-up approach

    Science.gov (United States)

    Pousthomis, M.; Garnero, C.; Marcelot, C. G.; Blon, T.; Cayez, S.; Cassignol, C.; Du, V. A.; Krispin, M.; Arenal, R.; Soulantica, K.; Viau, G.; Lacroix, L.-M.

    2017-02-01

    Nanostructured magnets benefiting from efficient exchange-coupling between hard and soft grains represent an appealing approach for integrated miniaturized magnetic power sources. Using a bottom-up approach, nanostructured materials were prepared from binary assemblies of bcc FeCo and fcc FePt nanoparticles and compared with pure L10-FePt materials. The use of a bifunctional mercapto benzoic acid yields homogeneous assemblies of the two types of particles while reducing the organic matter amount. The 650 °C thermal annealing, mandatory to allow the L10-FePt phase transition, led to an important interdiffusion and thus decreased drastically the amount of soft phase present in the final composites. The analysis of recoil curves however evidenced the presence of an efficient interphase exchange coupling, which allows obtaining better magnetic performances than pure L10 FePt materials, energy product above 100 kJ m-3 being estimated for a Pt content of only 33%. These results clearly evidenced the interest of chemically grown nanoparticles for the preparation of performant spring-magnets, opening promising perspective for integrated subcentimetric magnets with optimized properties.

  20. Runaway electrons as a diagnostic of plasma internal magnetic fluctuations

    Institute of Scientific and Technical Information of China (English)

    Zheng Yong-Zhen; Ding Xuan-Tong; Li Wen-Zhong

    2006-01-01

    The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This diffusion coefficient is determined by internal magnetic fluctuations, so it can be interpreted in terms of a magnetic fluctuation level. The internal magnetic fluctuation level (br/BT) is estimated to be about (2-4)×-4 in the HL-1M plasma. The results presented here demonstrate the effectiveness of using runaway electron transport techniques to determine internal magnetic fluctuations. A profile of magnetic fluctuation level in the HL-1M plasma can be estimated from Dr.

  1. Formation Mechanism of Micropores on the Surface of Pure Aluminum Induced by High-Current Pulsed Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    ZOU Yang; CAI Jie; WAN Ming-Zhen; LV Peng; GUAN Qing-Feng

    2011-01-01

    The mechanism of micropores formed on the surface of polycrystalline pure aluminum under high-current pulsed electron beam (HCPEB) irradiation is explained. It is discovered that dispersed micropores with sizes of 0.1-1μm on the irradiated surface of pure aluminum can be successfully fabricated after HCPEB irradiation. The dominant formation mechanism of the surface micropores should be attributed to the formation of supersaturation vacancies within the near surface during the HCPEB irradiation and the migration of vacancies along gra,in boundaries and/or dislocations towards the irradiated surface. It is expected that the HCPEB technique will become a new method for the rapid synthesis of surface porous materials.%The mechanism of micropores formed on the surface of polycrystalline pure aluminum under high-current pulsed electron beam (HCPEB) irradiation is explained.It is discovered that dispersed micropores with sizes of 0.1-1μm on the irradiated surface of pure aluminum can be successfully fabricated after HCPEB irradiation.The dominant formation mechanism of the surface micropores should be attributed to the formation of supersaturation vacancies within the near surface during the HCPEB irradiation and the migration of vacancies along grain boundaries and/or dislocations towards the irradiated surface.It is expected that the HCPEB technique will become a new method for the rapid synthesis of surface porous materials.High-current pulsed electron beams (HCPEBs)have attracted much attention in the field of material surface modification.[1-7] During the transient bombardment process a high energy (108-109 W·cm-2) is deposited only in a very thin layer (less than tens of micrometers) within a very short time (a few microseconds) and thereby causes ultrafast heating and cooling on the irradiated surface of materials.The dynamic stress fields induced in these processes can induce intense deformation on the material surface.

  2. Electronic structure and magnetic properties of solids

    Science.gov (United States)

    Savrasov, Sergej Y.; Toropova, Antonina; Katsnelson, Mikhail I.; Lichtenstein, Alexander I.; Antropov, Vladimir; Kotliar, Gabriel

    2005-05-01

    We review basic computational techniques for simulations of various magnetic properties of solids. Several applications to compute magnetic anisotropy energy, spin wave spectra, magnetic susceptibilities and temperature dependent magnetisations for a number of real systems are presented for illustrative purposes.

  3. Electronic structure and magnetic properties of solids

    OpenAIRE

    Savrasov, S. Y.; Toropova, A.; Katsnelson, M. I.; Lichtenstein, A. I.; Antropov, V.; Kotliar, G.

    2005-01-01

    We review basic computational techniques for simulations of various magnetic properties of solids. Several applications to compute magnetic anisotropy energy, spin wave spectra, magnetic susceptibilities and temperature dependent magnetisations for a number of real systems are presented for illustrative purposes.

  4. On electron-proton energy exchange in strong magnetic field

    Science.gov (United States)

    Zelener, B. B.; Zelener, B. V.; Manykin, E. A.; Bronin, S. Y.; Bobrov, A. A.

    2016-11-01

    Heating of protons in cold electron gas in strong magnetic field is studied. Calculations of heating process are preformed using molecular dynamics method. Estimations of heating rate depending on initial proton energies and electron gas temperatures are made.

  5. P.U.R.E. (purposeful, unambiguous, respectful, and effective) Conversations and electronic fetal monitoring: gaining consensus and collaboration.

    Science.gov (United States)

    Veltman, Larry; Larison, Kristine

    2010-11-01

    A revised nomenclature regarding electronic fetal heart rate monitoring was accepted at a National Institute of Child Health and Human Development consensus conference in 2008. At the heart of patient safety are communication strategies that enhance teamwork and collaboration between health care professionals. Communications is a complex 2-way process that involves more than transfer of factual information. P.U.R.E. (purposeful, unambiguous, respectful, and effective) Conversations in Obstetrics is an acronym that helps facilitate this communication process in perinatal care. P.U.R.E. stands for purposeful, unambiguous, respectful, and effective. The P.U.R.E. Conversations approach involves refinement of the mental processes associated with delivering the message, delivery of the message with data, accuracy, and direct requests for action, attention to relationships and behaviors between the communicating parties, and real-time assessment of the effectiveness of the communication. When the new electronic monitoring nomenclature is combined with an effective communication tool, one could expect to see a reduction in communication failures that could lead to adverse perinatal outcomes.

  6. Electronic and magnetic properties of Pd-Ni multilayers: Study using density functional theory

    Science.gov (United States)

    Gómez, Guillermina; Cabeza, Gabriela F.; Belelli, Patricia G.

    2009-10-01

    Electronic and magnetic properties of Pd-Ni multilayers have been studied using VASP method in the framework of the density functional theory (DFT). The calculations performed for different configurations (Pd n/Ni m(1 1 1), where n Pd layers are piled up over m Ni layers with n=0 to 4 and n+m=4), reveal that the important magnetic moment of Ni is significantly enhanced according as n increases due to hybridization effects between Pd and Ni mostly localized at the interface. The results also indicate that the Pd atoms are strongly polarized in the studied systems when compared with the pure metal.

  7. Electronic and magnetic properties of Pd-Ni multilayers: Study using density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Gomez, Guillermina [Grupo de Materiales y Sistemas Cataliticos, Departamento de Fisica, Universidad Nacional del Sur, Avda. Alem 1253, Bahia Blanca, B8000CPB (Argentina); Cabeza, Gabriela F. [CONICET (Argentina)], E-mail: gcabeza@uns.edu.ar; Belelli, Patricia G. [CONICET (Argentina)

    2009-10-15

    Electronic and magnetic properties of Pd-Ni multilayers have been studied using VASP method in the framework of the density functional theory (DFT). The calculations performed for different configurations (Pd{sub n}/Ni{sub m}(1 1 1), where n Pd layers are piled up over m Ni layers with n=0 to 4 and n+m=4), reveal that the important magnetic moment of Ni is significantly enhanced according as n increases due to hybridization effects between Pd and Ni mostly localized at the interface. The results also indicate that the Pd atoms are strongly polarized in the studied systems when compared with the pure metal.

  8. Monte Carlo modeling of cavity imaging in pure iron using back-scatter electron scanning microscopy

    Science.gov (United States)

    Yan, Qiang; Gigax, Jonathan; Chen, Di; Garner, F. A.; Shao, Lin

    2016-11-01

    Backscattered electrons (BSE) in a scanning electron microscope (SEM) can produce images of subsurface cavity distributions as a nondestructive characterization technique. Monte Carlo simulations were performed to understand the mechanism of void imaging and to identify key parameters in optimizing void resolution. The modeling explores an iron target of different thicknesses, electron beams of different energies, beam sizes, and scan pitch, evaluated for voids of different sizes and depths below the surface. The results show that the void image contrast is primarily caused by discontinuity of energy spectra of backscattered electrons, due to increased outward path lengths for those electrons which penetrate voids and are backscattered at deeper depths. Size resolution of voids at specific depths, and maximum detection depth of specific voids sizes are derived as a function of electron beam energy. The results are important for image optimization and data extraction.

  9. Soft magnetic properties and high frequency characteristics of FeM (M = B, Hf, Zr) and pure Fe films fabricated by oblique deposition

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Chengcheng; Zhang, Chao; Wang, Fenglong; Zhao, Zhong; Jiang, Changjun; Xue, Desheng [Lanzhou University, Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou (China); Lanzhou University, Key Laboratory of Special Function Materials and Structure Design of Ministry of Education, Lanzhou (China)

    2015-09-15

    To improve the high-frequency properties of Fe-based thin films, doped and pure Fe thin films were obliquely deposited on Si (100) substrate by RF-magnetron sputtering. Vibrating sample magnetometer (VSM) measurements show obvious in-plane uniaxial magnetic anisotropy in both doped and pure Fe thin films, and enhancement effects of doping on Soft magnetic properties were also observed. Microwave permeability measurements indicate that the resonance frequency and permeability of pure Fe films are much larger than those of doped Fe thin films. Damping factors of Fe thin films deposited at different oblique angles were further investigated. (orig.)

  10. Magnetic anisotropy of polycrystalline magnetoferritin investigated by SQUID and electron magnetic resonance

    Science.gov (United States)

    Moro, F.; de Miguel, R.; Jenkins, M.; Gómez-Moreno, C.; Sells, D.; Tuna, F.; McInnes, E. J. L.; Lostao, A.; Luis, F.; van Slageren, J.

    2014-06-01

    Magnetoferritin molecules with an average inorganic core diameter of 5.7±1.6 nm and polycrystalline internal structure were investigated by a combination of transmission electron microscopy, magnetic susceptibility, magnetization, and electron magnetic resonance (EMR) experiments. The temperature and frequency dependence of the magnetic susceptibility allowed for the determination of the magnetic anisotropy on an experimental time scale which spans from seconds to nanoseconds. In addition, angle-dependent EMR experiments were carried out for the determination of the nanoparticle symmetry and internal magnetic field. Due to the large surface to volume ratio, the nanoparticles show larger and uniaxial rather than cubic magnetic anisotropies compared to bulk maghemite and magnetite.

  11. Creating pure nanostructures from electron-beam-induced deposition using purification techniques: a technology perspective

    NARCIS (Netherlands)

    Botman, A.; Mulders, J.J.L.; Hagen, C.W.

    2009-01-01

    The creation of functional nanostructures by electron-beam-induced deposition (EBID) is becoming more widespread. The benefits of the technology include fast ‘point-and-shoot’ creation of three-dimensional nanostructures at predefined locations directly within a scanning electron microscope. One sig

  12. Improved Nonambipolar Electron Source Operation with Permanent Magnets

    Science.gov (United States)

    Gudmundson, Jesse; Hershkowitz, Noah

    2008-11-01

    The Nonambipolar Electron Source (NES) is a Radio Frequency (rf) plasma-based electron source that does not rely on electron emission at a cathode surface. All electrons are extracted at an electron sheath through a biased ring and all ions are lost radially to a biased Faraday shield. An electromagnet in the original NES has been replaced by a NdFeB permanent magnet array. A portion of the magnet array consists of a ring of radially aligned magnets followed by a ring of axially aligned magnets that produce a peak field of approximately 800 Gauss. Axial magnetic field strength at the extraction ring was increased using an additional ring of axially aligned magnets. Measurement of the magnetic field was in good agreement with field predicted by the FEMM (Finite Element Method Magnetics) code. Optimization of the single turn antenna and biased ring position in the magnetic field will be discussed. At least 15 A of electron current was extracted using a flow rate of 15 sccm Ar at 600 W of rf power at 13.56 MHz. For comparison, the original NES required 1200 W of power to achieve 15 A of extracted current. Compared to the previous coil design, the NdFeB magnets are lighter weight and require no power.

  13. Purely electric and magnetic dipole resonances in metamaterial dielectric resonators through perturbation theory inspired geometries

    CERN Document Server

    Campione, Salvatore; Warne, Larry K; Sinclair, Michael B

    2014-01-01

    In this paper we describe a methodology for tailoring the design of metamaterial dielectric resonators, which represent a promising path toward low-loss metamaterials at optical frequencies. We first describe a procedure to decompose the far field scattered by subwavelength resonators in terms of multipolar field components, providing explicit expressions for the multipolar far fields. We apply this formulation to confirm that an isolated high-permittivity cube resonator possesses frequency separated electric and magnetic dipole resonances, as well as a magnetic quadrupole resonance in close proximity to the electric dipole resonance. We then introduce multiple dielectric gaps to the resonator geometry in a manner suggested by perturbation theory, and demonstrate the ability to overlap the electric and magnetic dipole resonances, thereby enabling directional scattering by satisfying the first Kerker condition. We further demonstrate the ability to push the quadrupole resonance away from the degenerate dipole ...

  14. Pure quantum states of neutrino with rotating spin in dense magnetized matter

    CERN Document Server

    Arbuzova, E V; Murchikova, E M

    2009-01-01

    The problem of rotation of the neutrino spin in dense matter and in strong electromagnetic field is solved in full agreement with the basic principles of quantum mechanics. We found complete system of wave functions of a massive Dirac neutrino possessing anomalous magnetic moment. These functions are eigenfunctions of kinetic momentum operator and describe neutrino with rotating spin. Using these wave functions it is possible to calculate probabilities of various processes with neutrino in the framework of the Furry picture. The dispersion law for the neutrino in dense magnetized matter is found. It is shown that group velocity of neutrino is independent of spin orientation.

  15. Magnetic Force Microscopy Using Electron-Beam Fabricated Tips

    NARCIS (Netherlands)

    Rührig, M.; Porthun, S.; Lodder, J.C.

    1994-01-01

    We used a new concept of tip preparation for magnetic force microscopy (MFM) proposed recently based on coating electron beam deposited carbon needles with appropriate magnetic thin film materials. In combining the advantages of electron beam fabricated needles with those of already widely used thin

  16. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    NARCIS (Netherlands)

    Haynes, C.T.; Burgess, D.; Camporeale, E.; Sundberg, T.

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic

  17. Read-out electronics for DC squid magnetic measurements

    Science.gov (United States)

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    2002-01-01

    Read-out electronics for DC SQUID sensor systems, the read-out electronics incorporating low Johnson noise radio-frequency flux-locked loop circuitry and digital signal processing algorithms in order to improve upon the prior art by a factor of at least ten, thereby alleviating problems caused by magnetic interference when operating DC SQUID sensor systems in magnetically unshielded environments.

  18. Anisotropic Electron Tail Generation during Tearing Mode Magnetic Reconnection

    Science.gov (United States)

    DuBois, Ami M.; Almagri, Abdulgader F.; Anderson, Jay K.; Den Hartog, Daniel J.; Lee, John David; Sarff, John S.

    2017-02-01

    The first experimental evidence of anisotropic electron energization during magnetic reconnection that favors a direction perpendicular to the guide magnetic field in a toroidal, magnetically confined plasma is reported in this Letter. Magnetic reconnection plays an important role in particle heating, energization, and transport in space and laboratory plasmas. In toroidal devices like the Madison Symmetric Torus, discrete magnetic reconnection events release large amounts of energy from the equilibrium magnetic field. Fast x-ray measurements imply a non-Maxwellian, anisotropic energetic electron tail is formed at the time of reconnection. The tail is well described by a power-law energy dependence. The expected bremsstrahlung from an electron distribution with an anisotropic energetic tail (v⊥>v∥ ) spatially localized in the core region is consistent with x-ray emission measurements. A turbulent process related to tearing fluctuations is the most likely cause for the energetic electron tail formation.

  19. Magnetic field contribution to the last electron-photon scattering

    OpenAIRE

    Giovannini, Massimo

    2010-01-01

    When the cosmic microwave photons scatter electrons just prior to the decoupling of matter and radiation, magnetic fields do contribute to the Stokes matrix as well as to the scalar, vector and tensor components of the transport equations for the brightness perturbations. The magnetized electron-photon scattering is hereby discussed in general terms by including, for the first time, the contribution of magnetic fields with arbitrary direction and in the presence of the scalar, vector and tens...

  20. Ultrafast imprinting of topologically protected magnetic textures via pulsed electrons

    Science.gov (United States)

    Schäffer, A. F.; Dürr, H. A.; Berakdar, J.

    2017-07-01

    Short electron pulses are demonstrated to trigger and control magnetic excitations, even at low electron current densities. We show that the tangential magnetic field surrounding a picosecond electron pulse can imprint topologically protected magnetic textures such as skyrmions in a sample with a residual Dzyaloshinskii-Moriya spin-orbital coupling. Characteristics of the created excitations such as the topological charge can be steered via the duration and the strength of the electron pulses. The study points to a possible way for a spatiotemporally controlled generation of skyrmionic excitations.

  1. Induction heating pure vapor source of high temperature melting point materials on electron cyclotron resonance ion source.

    Science.gov (United States)

    Kutsumi, Osamu; Kato, Yushi; Matsui, Yuuki; Kitagawa, Atsushi; Muramatsu, Masayuki; Uchida, Takashi; Yoshida, Yoshikazu; Sato, Fuminobu; Iida, Toshiyuki

    2010-02-01

    Multicharged ions that are needed are produced from solid pure material with high melting point in an electron cyclotron resonance ion source. We develop an evaporator by using induction heating (IH) with multilayer induction coil, which is made from bare molybdenum or tungsten wire without water cooling and surrounding the pure vaporized material. We optimize the shapes of induction coil and vaporized materials and operation of rf power supply. We conduct experiment to investigate the reproducibility and stability in the operation and heating efficiency. IH evaporator produces pure material vapor because materials directly heated by eddy currents have no contact with insulated materials, which are usually impurity gas sources. The power and the frequency of the induction currents range from 100 to 900 W and from 48 to 23 kHz, respectively. The working pressure is about 10(-4)-10(-3) Pa. We measure the temperature of the vaporized materials with different shapes, and compare them with the result of modeling. We estimate the efficiency of the IH vapor source. We are aiming at the evaporator's higher melting point material than that of iron.

  2. Electron spin resonance evaluation of pure CaSO4 and as a phosphor doped with P and Dy.

    Science.gov (United States)

    de Jesus, E F O; Rossi, A M; Lopes, R T

    2002-01-01

    Polycrystalline CaSO4 powder, doped with different elements but mainly rare earths, is one of the most interesting thermoluminescent (TL) materials. Although many electron spin resonance (ESR) analyses have been reported for these materials few studies have been published about the potential of CaSO4 for ESR dosimetry; almost all studies used CaSO4:Dy with a very low Dy concentration as the material for TL measurements. Pure CaSO4 from Merck was used to prepare CaSO4:Dy and CaSO4:P:Dy with different Dy concentrations. Samples were annealed at 600 degrees C for 1 h before irradiation in a Gammacell 220 irradiator with a 60Co gamma source at a dose rate of 100 Gy x min(-1). The ESR spectra of the pure CaSO4 and CaSO4 doped with P and Dy show the lines usually observed with these types of material, with the factor g around 2.036 and an intense line at g = 2.0011 found only in the pure material. This line, probably an axial SO4-, grows linearly with absorbed dose until 1.0 kGy and shows good stability with time. The line should be stabilized by matrix impurities because it can be removed by a simple treatment with hot sulphuric acid.

  3. Magnetic susceptibility of Alq{sub 3} powder, pure and Al-doped 8-hydroxyquinoline

    Energy Technology Data Exchange (ETDEWEB)

    Burke, Franklyn, E-mail: frburke@tcd.i [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland); Abid, Mohamed; Stamenov, Plamen; Coey, J.M.D. [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland)

    2010-05-15

    Single-crystal nanowires several microns long and 100-200 nm in diameter were grown by physical vapour deposition from mixed Alq{sub 3}/gamma-Al{sub 2}O{sub 3} powder. The crystals are orthorhombic Al-doped 8-hydroxyquinoline. The molar susceptibility is -3x10{sup -9} at room temperature, and it shows a Curie-law upturn below about 50 K. The approach to saturation at low temperature indicates a density of S=1/2 defects 4x10{sup -4} per formula unit. Pure 8-hydroxyquinoline and aluminium (Alq{sub 3}) behave similarly. Pressed pellets exhibit much increased paramagnetic susceptibility due to iron ions scavanged from the steel die. Subsequent melting of these samples produces a ferromagnetic signal of order 0.01 A m{sup 2} kg{sup -1}, which is attributed to metallic iron nanoclusters in the organic material.

  4. Electron diffusion in a sheared unperturbed magnetic field and an electrostatic stochastic field

    Energy Technology Data Exchange (ETDEWEB)

    Petrisor, I [Department of Physics, Association Euratom-MEdC, Romania, University of Craiova, 13 A I Cuza Str., 200585 Craiova (Romania); Negrea, M [Department of Physics, Association Euratom-MEdC, Romania, University of Craiova, 13 A I Cuza Str., 200585 Craiova (Romania); Weyssow, B [Physique Statistique-Plasmas, Association Euratom-Etat Belge, Universite Libre de Bruxelles, Campus Plaine, Bd. du Triomphe, 1050 Brussels (Belgium)

    2007-01-15

    The electron diffusion induced by a two-dimensional electrostatic turbulence, in a sheared slab approximation of the toroidal magnetic geometry, is studied firstly using the decorrelation trajectory method (DCT), secondly by direct numerical simulation. The former semi-analytical method allows us to go beyond the Corrsin approximation, thus allowing for a non-classical analysis of the particle trapping phenomenon. The DCT results are compared to the transport properties of the electrons obtained by numerical simulations assuming an isotropic spectrum of electrostatic drift type turbulence that is Gaussian for small wavevectors and power-law k{sup -3} for large wavevectors. The 'radial' and the 'poloidal' running and asymptotic diffusion coefficients of thermal electrons are obtained for physically relevant parameter values. The existence of enhanced diffusion in the poloidal direction is observed in the presence of magnetic shear. The agreement between the semi-analytical method and the purely numerical method is pointed out.

  5. Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

    DEFF Research Database (Denmark)

    Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

    2015-01-01

    We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

  6. Carrier generation and electronic properties of a single-component pure organic metal

    Science.gov (United States)

    Kobayashi, Yuka; Terauchi, Takeshi; Sumi, Satoshi; Matsushita, Yoshitaka

    2017-01-01

    Metallic conduction generally requires high carrier concentration and wide bandwidth derived from strong orbital interaction between atoms or molecules. These requisites are especially important in organic compounds because a molecule is fundamentally an insulator; only multi-component salts with strong intermolecular interaction--namely, only charge transfer complexes and conducting polymers--have demonstrated intrinsic metallic behaviour. Herein we report a single-component electroactive molecule, zwitterionic tetrathiafulvalene(TTF)-extended dicarboxylate radical (TED), exhibiting metallic conduction even at low temperatures. TED exhibits d.c. conductivities of 530 S cm-1 at 300 K and 1,000 S cm-1 at 50 K with copper-like electronic properties. Spectroscopic and theoretical investigations of the carrier-generation mechanism and the electronic states of this single molecular species reveal a unique electronic structure with a spin-density gradient in the extended TTF moieties that becomes, in itself, a metallic state.

  7. Electron holography of magnetic field generated by a magnetic recording head.

    Science.gov (United States)

    Goto, Takayuki; Jeong, Jong Seok; Xia, Weixing; Akase, Zentaro; Shindo, Daisuke; Hirata, Kei

    2013-06-01

    The magnetic field generated by a magnetic recording head is evaluated using electron holography. A magnetic recording head, which is connected to an electric current source, is set on the specimen holder of a transmission electron microscope. Reconstructed phase images of the region around the magnetic pole show the change in the magnetic field distribution corresponding to the electric current applied to the coil of the head. A simulation of the magnetic field, which is conducted using the finite element method, reveals good agreement with the experimental observations.

  8. Reconfigurable Boolean Logic Using Magnetic Single-Electron Transistors

    Science.gov (United States)

    Gonzalez-Zalba, M. Fernando; Ciccarelli, Chiara; Zarbo, Liviu P.; Irvine, Andrew C.; Campion, Richard C.; Gallagher, Bryan L.; Jungwirth, Tomas; Ferguson, Andrew J.; Wunderlich, Joerg

    2015-01-01

    We propose a novel hybrid single-electron device for reprogrammable low-power logic operations, the magnetic single-electron transistor (MSET). The device consists of an aluminium single-electron transistor with a GaMnAs magnetic back-gate. Changing between different logic gate functions is realized by reorienting the magnetic moments of the magnetic layer, which induces a voltage shift on the Coulomb blockade oscillations of the MSET. We show that we can arbitrarily reprogram the function of the device from an n-type SET for in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane magnetization orientation. Moreover, we demonstrate a set of reprogrammable Boolean gates and its logical complement at the single device level. Finally, we propose two sets of reconfigurable binary gates using combinations of two MSETs in a pull-down network. PMID:25923789

  9. Ionospheric Electron Density during Magnetically Active Times over Istanbul

    Science.gov (United States)

    Naz Erbaş, Bute; Kaymaz, Zerefsan; Ceren Moral, Aysegul; Emine Ceren Kalafatoglu Eyiguler, R. A..

    2016-07-01

    In this study, we analyze electron density variations over Istanbul using Dynasonde observations during the magnetically active times. In order to perform statistical analyses, we first determined magnetic storms and magnetospheric substorm intervals from October 2012 to October 2015 using Kyoto's magnetic index data. Corresponding ionospheric parameters, such as critical frequency of F2 region (foF2), maximum electron density height (hmF2), total electron density (TEC) etc. were retrieved from Dynasonde data base at Istanbul Technical University's Space Weather Laboratory. To understand the behavior of electron density during the magnetically active times, we remove the background quiet time variations first and then quantify the anomalies. In this presentation, we will report results from our preliminary analyses from the selected cases corresponding to the strong magnetic storms. Initial results show lower electron densities at noon times and higher electron densities in the late afternoon toward sunset times when compared to the electron densities of magnetically quiet times. We also compare the results with IRI and TIEGCM ionospheric models in order to understand the physical and dynamical causes of these variations. During the presentation we will also discuss the role of these changes during the magnetically active times on the GPS communications through ionosphere.

  10. Spherical fused silica cells filled with pure helium for nuclear magnetic resonance-magnetometry

    Energy Technology Data Exchange (ETDEWEB)

    Maul, Andreas; Blümler, Peter, E-mail: bluemler@uni-mainz.de; Heil, Werner; Nikiel, Anna; Otten, Ernst [Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz (Germany); Petrich, Andreas; Schmidt, Thomas [ifw Günter-Köhler-Institut für Fügetechnik und Werkstoffprüfung GmbH, Otto-Schott-Str. 13, 07745 Jena (Germany)

    2016-01-15

    High magnetic fields (>1 T) are measured by NMR magnetometers with unrivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted {sup 3}He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field, the optimal container for the {sup 3}He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO{sub 2} laser and the inner volume was filled with a few mbars of {sup 3}He via wall permeation. NMR-measurements on such a sample had coherence times of 5 min. While the hemispheres were produced with <1 μm deviation from sphericity, the bonding left a step of ca. 50 μm at maximum. The influence of such a mismatch, its orientation, and the immediate environment of the sample is analyzed by FEM-simulations and discussed in view of coherence times and absolute field measurements.

  11. Electron acoustic solitary waves in a magnetized plasma with nonthermal electrons and an electron beam

    Science.gov (United States)

    Singh, S. V.; Devanandhan, S.; Lakhina, G. S.; Bharuthram, R.

    2016-08-01

    A theoretical investigation is carried out to study the obliquely propagating electron acoustic solitary waves having nonthermal hot electrons, cold and beam electrons, and ions in a magnetized plasma. We have employed reductive perturbation theory to derive the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation describing the nonlinear evolution of these waves. The two-dimensional plane wave solution of KdV-ZK equation is analyzed to study the effects of nonthermal and beam electrons on the characteristics of the solitons. Theoretical results predict negative potential solitary structures. We emphasize that the inclusion of finite temperature effects reduces the soliton amplitudes and the width of the solitons increases by an increase in the obliquity of the wave propagation. The numerical analysis is presented for the parameters corresponding to the observations of "burst a" event by Viking satellite on the auroral field lines.

  12. Electronic and magnetic properties of ultrathin rhodium nanowires

    CERN Document Server

    Wang Bao Lin; Ren-Yun; Sun Hou Qian; Chen Xiao Shuang; Zhao Ji Jun

    2003-01-01

    The structures of ultrathin rhodium nanowires are studied using empirical molecular dynamics simulations with a genetic algorithm. Helical multishell cylindrical and pentagonal packing structures are found. The electronic and magnetic properties of the rhodium nanowires are calculated using an spd tight-binding Hamiltonian in the unrestricted Hartree-Fock approximation. The average magnetic moment and electronic density of states are obtained. Our results indicate that the electronic and magnetic properties of the rhodium nanowires depend not only on the size of the wire but also on the atomic structure. In particular, centred pentagonal and hexagonal structures can be unusually ferromagnetic.

  13. Simulations of space charge neutralization in a magnetized electron cooler

    Energy Technology Data Exchange (ETDEWEB)

    Gerity, James [Texas A-M; McIntyre, Peter M. [Texas A-M; Bruhwiler, David Leslie [RadiaSoft, Boulder; Hall, Christopher [RadiaSoft, Boulder; Moens, Vince Jan [Ecole Polytechnique, Lausanne; Park, Chong Shik [Fermilab; Stancari, Giulio [Fermilab

    2017-02-02

    Magnetized electron cooling at relativistic energies and Ampere scale current is essential to achieve the proposed ion luminosities in a future electron-ion collider (EIC). Neutralization of the space charge in such a cooler can significantly increase the magnetized dynamic friction and, hence, the cooling rate. The Warp framework is being used to simulate magnetized electron beam dynamics during and after the build-up of neutralizing ions, via ionization of residual gas in the cooler. The design follows previous experiments at Fermilab as a verification case. We also discuss the relevance to EIC designs.

  14. Visual object agnosia and pure word alexia: correlation of functional magnetic resonance imaging and lesion localization.

    Science.gov (United States)

    Salvan, Carmen V; Ulmer, John L; DeYoe, Edgar A; Wascher, Thomas; Mathews, Vincent P; Lewis, James W; Prost, Robert W

    2004-01-01

    We present a case of a 64-year-old, right-handed female with a metastatic breast cancer lesion involving the left posterior inferior temporal lobe causing complete loss of the ability to recognize visually common objects and words. After her symptoms resolved on corticosteroid therapy, functional magnetic resonance imaging (fMRI) mapping demonstrated strong left-hemispheric dominance for word recognition and right-hemispheric dominance for object recognition. The case illustrates the relationships among ventral occipito-temporal cortical activation, lesion localization, and lesion-induced deficits of higher visual function. The relationship between hemispheric dominance determined by fMRI and risk of postoperative deficit depends on the specific visual function of interest.

  15. Modified Fermi energy of electrons in a superhigh magnetic field

    Science.gov (United States)

    Zhu, Cui; Gao, Zhi Fu; Li, Xiang Dong; Wang, Na; Yuan, Jian Ping; Peng, Qiu He

    2016-04-01

    In this paper, we investigate the electron Landau level stability and its influence on the electron Fermi energy, EF(e), in the circumstance of magnetars, which are powered by magnetic field energy. In a magnetar, the Landau levels of degenerate and relativistic electrons are strongly quantized. A new quantity gn, the electron Landau level stability coefficient is introduced. According to the requirement that gn decreases with increasing the magnetic field intensity B, the magnetic field index β in the expression of EF(e) must be positive. By introducing the Dirac-δ function, we deduce a general formulae for the Fermi energy of degenerate and relativistic electrons, and obtain a particular solution to EF(e) in a superhigh magnetic field (SMF). This solution has a low magnetic field index of β = 1/6, compared with the previous one, and works when ρ ≥ 107g cm-3 and Bcr ≪ B ≤ 1017 Gauss. By modifying the phase space of relativistic electrons, a SMF can enhance the electron number density ne, and decrease the maximum of electron Landau level number, which results in a redistribution of electrons. According to Pauli exclusion principle, the degenerate electrons will fill quantum states from the lowest Landau level to the highest Landau level. As B increases, more and more electrons will occupy higher Landau levels, though gn decreases with the Landau level number n. The enhanced ne in a SMF means an increase in the electron Fermi energy and an increase in the electron degeneracy pressure. The results are expected to facilitate the study of the weak-interaction processes inside neutron stars and the magnetic-thermal evolution mechanism for magnetars.

  16. Pure rotational spectra of PbSe and PbTe: potential function, Born-Oppenheimer breakdown, field shift effect and magnetic shielding.

    Science.gov (United States)

    Giuliano, Barbara M; Bizzocchi, Luca; Cooke, Stephen; Banser, Deike; Hess, Mareike; Fritzsche, Juliane; Grabow, Jens-Uwe

    2008-04-21

    The pure rotational spectra of 41 isotopic species of PbSe and PbTe have been measured in their X 1Sigma+ electronic state with a resonator pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of suitable target rods and stabilised in supersonic jets of noble gas. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients delta01 for Pb, Se and Te. Unusual large values of the BOB parameters for Pb have been rationalized in terms of finite nuclear size (field shift) effect. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both PbSe and PbTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 207Pb, 77Se, 123Te, and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.

  17. Polarization of radiation of electrons in highly turbulent magnetic fields

    Science.gov (United States)

    Prosekin, A. Yu.; Kelner, S. R.; Aharonian, F. A.

    2016-09-01

    We study the polarization properties of the jitter and synchrotron radiation produced by electrons in highly turbulent anisotropic magnetic fields. The net polarization is provided by the geometry of the magnetic field the directions of which are parallel to a certain plane. Such conditions may appear in the relativistic shocks during the amplification of the magnetic field through the so-called Weibel instability. While the polarization properties of the jitter radiation allows extraction of direct information on the turbulence spectrum as well as the geometry of magnetic field, the polarization of the synchrotron radiation reflects the distribution of the magnetic field over its strength. For the isotropic distribution of monoenergetic electrons, we found that the degree of polarization of the synchrotron radiation is larger than the polarization of the jitter radiation. For the power-law energy distribution of electrons the relation between the degree of polarization of synchrotron and jitter radiation depends on the spectral index of the distribution.

  18. Polarization of radiation of electrons in highly turbulent magnetic fields

    CERN Document Server

    Prosekin, A Yu; Aharonian, F A

    2016-01-01

    We study the polarization properties of the jitter and synchrotron radiation produced by electrons in highly turbulent anisotropic magnetic fields. The net polarization is provided by the geometry of the magnetic field the directions of which are parallel to a certain plane. Such conditions may appear in the relativistic shocks during the amplification of the magnetic field through the so-called Weibel instability. While the polarization properties of the jitter radiation allows extraction of direct information on the turbulence spectrum as well as the geometry of magnetic field, the polarization of the synchrotron radiation reflects the distribution of the magnetic field over its strength. For the isotropic distribution of monoenergetic electrons, we found that the degree of polarization of the synchrotron radiation is larger than the polarization of the jitter radiation. For the power-law energy distribution of electrons the relation between the degree of polarization of synchrotron and jitter radiation dep...

  19. Electronic structure and magnetism on FeSiAl alloy: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso Schwindt, V.; Sandoval, M.; Ardenghi, J.S.; Bechthold, P.; González, E.A.; Jasen, P.V., E-mail: pjasen@uns.edu.ar

    2015-09-01

    Density functional theory (DFT) calculation has been performed to study the electronic structure and chemical bonding in FeSiAl alloy. These calculations are useful to understand the magnetic properties of this alloy. Our results show that the mean magnetic moment of Fe atoms decreases due to the crystal structure and the effect of Si and Al. Depending on the environment, the magnetic moment of one Fe site (Fe{sub 1}) increases to about 14.3% while of the other site (Fe{sub 2}) decreases to about 25.9% (compared with pure bcc Fe). All metal–metal overlap interactions are bonding and slightly weaker than those found in the bcc Fe structure. The electronic structure (DOS) shows an important hybridization among Fe, Si and Al atoms, thus making asymmetric the PDOS with a very slight polarization of Al and Si atoms. Our study explains the importance of crystal structure in determining the magnetic properties of the alloys. FeSiAl is a good candidate for electromagnetic interference shielding combining low price and good mechanical and magnetic properties. - Highlights: • The mean magnetic moment of the Fe atoms decreases compared to bcc Fe. • There are strong bonding interactions among the Fe, Si and Al atoms. • This structure has a stable ferromagnetism. • The Fe–Fe bonds distances elongates and are weaker than those in the bcc Fe.

  20. Axisymmetric Magnetic Fields, Electron Capture and Pycnonuclear Reactions in Magnetized White Dwarfs

    CERN Document Server

    Otoniel, Edson; Malheiro, Manuel; Schramm, Stefan; Weber, Fridolin

    2016-01-01

    In this work, we study the properties of magnetized white dwarfs taking into account possible instabilities due to electron capture and pycnonuclear fusion reactions in the cores of such objects. The structure of white dwarfs is obtained by solving the Einstein-Maxwell equations with a poloidal magnetic field in a fully general relativistic approach. The stellar interior is composed of a regular crystal lattice made of carbon ions immersed in a degenerate relativistic electron gas. The onsets of electron capture reactions and pycnonuclear reactions are determined with and without magnetic fields. We find that magnetized white dwarfs violate the standard Chandrasekhar mass limit significantly, even when electron capture and pycnonuclear instabilities are present in the stellar interior. We obtain a maximum white dwarf mass of around $2.12\\,M_{\\odot}$ with a central magnetic field of $\\sim 1.74\\times 10^{14}$G, which indicates that magnetized white dwarfs may be the progenitor candidates of superluminous type I...

  1. Inoculation of pure aluminium structure with Ti + B addition in impulse magnetic field

    Directory of Open Access Journals (Sweden)

    J. Szajnar

    2005-12-01

    Full Text Available Purpose: The main aim of investigations was the reduction of grain size and unification of structure for clean metal casting by introduction of small amount of inoculant with impulse magnetic field.Design/methodology/approach: Experimental plan was planed on the basis of statistical factor design on two levels for three variables (pouring parameters. The equiaxed crystals zone content was calculated by computer program to processing and image analysis after metallographic research.Findings: The results of study show relationship between area of equiaxial zone and pouring parameters.Research limitations/implications: Towards lack of resolute relations between casting parameters and structure was selected statistical analysis to determine these relations using stepwise regression. Practical implications: The work presents refinement of structure methods which are particularly important in continuous and semi-continuous casting where products are used for plastic forming. Large columnar crystals zone result in forces extrusion rate reduction and during the ingot rolling delamination of external layers can occur.Originality/value: The value of this paper resides in coupling of two refinement of structure methods. The first method is internal factor - inoculation with Ti+B and the second method is external factor - influence of electromagnetic field on crystallization process.

  2. Optical, thermal and magnetic studies of pure and cobalt chloride doped L-alanine cadmium chloride

    Science.gov (United States)

    Benila, B. S.; Bright, K. C.; Delphine, S. Mary; Shabu, R.

    2017-03-01

    Single crystals of L-alanine cadmium chloride (LACC) and cobalt chloride (Co2+) doped LACC have been grown by the slow evaporation solution growth technique. The grown crystals were subjected to various characterizations such as powder XRD, SXRD, FTIR, UV-vis, EDAX, TG/DTA, VSM, Dielectric and Second Harmonic Generation (SHG) measurements. The lattice parameters of the grown crystals were determined by single crystal X-ray analysis. EDAX analysis confirms the presence of Co2+ ion in the host material. The functional group and optical behavior of the crystals were identified from FTIR and UV-vis spectrum analysis. Electrical parameters such as dielectric constant, dielectric loss have been studied. The thermal stability of the compound was found out using TGA/DTA analysis. Second Harmonic Generation of the samples was confirmed by Kurtz-Perry powder technique. Magnetic properties of the crystals studied by VSM were also reported. The encouraging results show that the cobalt chloride doped LACC crystals have greater potential applications in optical devices.

  3. Design, simulation and construction of quadrupole magnets for focusing electron beam in powerful industrial electron accelerator

    Directory of Open Access Journals (Sweden)

    S KH Mousavi

    2015-09-01

    Full Text Available In this paper the design and simulation of quadrupole magnets and electron beam optical of that by CST Studio code has been studied. Based on simulation result the magnetic quadrupole has been done for using in beam line of first Iranian powerful electron accelerator. For making the suitable magnetic field the effects of material and core geometry and coils current variation on quadrupole magnetic field have been studied. For test of quadrupole magnet the 10 MeV beam energy and 0.5 pi mm mrad emittance of input beam has been considered. We see the electron beam through the quadrupole magnet focus in one side and defocus in other side. The optimum of distance between two quadrupole magnets for low emittance have been achieved. The simulation results have good agreement with experimental results

  4. Electron spin separation without magnetic field.

    Science.gov (United States)

    Pawłowski, J; Szumniak, P; Skubis, A; Bednarek, S

    2014-08-27

    A nanodevice capable of separating spins of two electrons confined in a quantum dot formed in a gated semiconductor nanowire is proposed. Two electrons confined initially in a single quantum dot in the singlet state are transformed into the system of two electrons confined in two spatially separated quantum dots with opposite spins. In order to separate the electrons' spins we exploit transitions between the singlet and the triplet state, which are induced by resonantly oscillating Rashba spin-orbit coupling strength. The proposed device is all electrically controlled and the electron spin separation can be realized within tens of picoseconds. The results are supported by solving numerically the quasi-one-dimensional time-dependent Schroedinger equation for two electrons, where the electron-electron correlations are taken into account in the exact manner.

  5. Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes

    Energy Technology Data Exchange (ETDEWEB)

    Kahler, S.W. [Air Force Research Laboratory, 29 Randolph Rd, Hanscom AFB, Massachusetts 01731 (United States); Crooker, N.U. [Center for Space Physics, Boston University, 725 Commonwealth Ave., Boston, Massachusetts 02215 (United States); Gosling, J.T. [Los Alamos National Laboratory, MS D 466, Los Alamos, New Mexico 87545 (United States)

    1999-06-01

    We have used solar wind electron heat fluxes to determine the magnetic polarities of the interplanetary magnetic fields (IMF) during the ISEE-3 observations in 1978{endash}1982. That period included 14 magnetic clouds (MCs) identified by Zhang and Burlaga. The MCs have been modeled as single magnetic flux ropes, and it is generally assumed that they are magnetically closed structures with each end of the flux rope connected to the Sun. The flux rope model is valid only if the magnetic polarity of each MC does not change during the passage of ISEE-3 through the MC. We test this model with the heat flux data, using the dominant heat flux in bidirectional electron heat fluxes to determine the MC polarities. The polarity changes within at least 2, and possibly 6, of the 14 MCs, meaning that those MCs can not fit the model of a single flux rope. {copyright} {ital 1999 American Institute of Physics.}

  6. Exploring ISEE-3 magnetic cloud polarities with electron heat fluxes

    Science.gov (United States)

    Kahler, S. W.; Crooker, N. U.; Gosling, J. T.

    1999-06-01

    We have used solar wind electron heat fluxes to determine the magnetic polarities of the interplanetary magnetic fields (IMF) during the ISEE-3 observations in 1978-1982. That period included 14 magnetic clouds (MCs) identified by Zhang and Burlaga. The MCs have been modeled as single magnetic flux ropes, and it is generally assumed that they are magnetically closed structures with each end of the flux rope connected to the Sun. The flux rope model is valid only if the magnetic polarity of each MC does not change during the passage of ISEE-3 through the MC. We test this model with the heat flux data, using the dominant heat flux in bidirectional electron heat fluxes to determine the MC polarities. The polarity changes within at least 2, and possibly 6, of the 14 MCs, meaning that those MCs can not fit the model of a single flux rope.

  7. Electron-scale measurements of magnetic reconnection in space.

    Science.gov (United States)

    Burch, J L; Torbert, R B; Phan, T D; Chen, L-J; Moore, T E; Ergun, R E; Eastwood, J P; Gershman, D J; Cassak, P A; Argall, M R; Wang, S; Hesse, M; Pollock, C J; Giles, B L; Nakamura, R; Mauk, B H; Fuselier, S A; Russell, C T; Strangeway, R J; Drake, J F; Shay, M A; Khotyaintsev, Yu V; Lindqvist, P-A; Marklund, G; Wilder, F D; Young, D T; Torkar, K; Goldstein, J; Dorelli, J C; Avanov, L A; Oka, M; Baker, D N; Jaynes, A N; Goodrich, K A; Cohen, I J; Turner, D L; Fennell, J F; Blake, J B; Clemmons, J; Goldman, M; Newman, D; Petrinec, S M; Trattner, K J; Lavraud, B; Reiff, P H; Baumjohann, W; Magnes, W; Steller, M; Lewis, W; Saito, Y; Coffey, V; Chandler, M

    2016-06-03

    Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.

  8. Magnetic field contribution to the last electron-photon scattering

    CERN Document Server

    Giovannini, Massimo

    2010-01-01

    When the cosmic microwave photons scatter electrons just prior to the decoupling of matter and radiation, magnetic fields do contribute to the Stokes matrix as well as to the scalar, vector and tensor components of the transport equations for the brightness perturbations. The magnetized electron-photon scattering is hereby discussed in general terms by including, for the first time, the contribution of magnetic fields with arbitrary direction and in the presence of the scalar, vector and tensor modes of the geometry. The propagation of relic vectors and relic gravitons is discussed for a varying magnetic field orientation and for different photon directions. The source terms of the transport equations in the presence of the relativistic fluctuations of the geometry are also explicitly averaged over the magnetic field orientations and the problem of a consistent account of the small-scale and large-scale magnetic field is briefly outlined.

  9. Magnetic field contribution to the last electron-photon scattering

    Energy Technology Data Exchange (ETDEWEB)

    Giovannini, Massimo, E-mail: massimo.giovannini@cern.c [Department of Physics, Theory Division, CERN, 1211 Geneva 23 (Switzerland); INFN, Section of Milan-Bicocca, 20126 Milan (Italy)

    2010-11-21

    When the cosmic microwave photons scatter electrons just prior to the decoupling of matter and radiation, magnetic fields do contribute to the Stokes matrix as well as to the scalar, vector and tensor components of the transport equations for the brightness perturbations. The magnetized electron-photon scattering is hereby discussed in general terms by including, for the first time, the contribution of magnetic fields with arbitrary direction and in the presence of the scalar, vector and tensor modes of the geometry. The propagation of relic vectors and relic gravitons is discussed for a varying magnetic field orientation and for different photon directions. The source terms of the transport equations in the presence of the relativistic fluctuations of the geometry are also explicitly averaged over the magnetic field orientations and the problem of a consistent account of the small-scale and large-scale magnetic field is briefly outlined.

  10. Magnetic field contribution to the last electron-photon scattering

    Science.gov (United States)

    Giovannini, Massimo

    2010-11-01

    When the cosmic microwave photons scatter electrons just prior to the decoupling of matter and radiation, magnetic fields do contribute to the Stokes matrix as well as to the scalar, vector and tensor components of the transport equations for the brightness perturbations. The magnetized electron-photon scattering is hereby discussed in general terms by including, for the first time, the contribution of magnetic fields with arbitrary direction and in the presence of the scalar, vector and tensor modes of the geometry. The propagation of relic vectors and relic gravitons is discussed for a varying magnetic field orientation and for different photon directions. The source terms of the transport equations in the presence of the relativistic fluctuations of the geometry are also explicitly averaged over the magnetic field orientations and the problem of a consistent account of the small-scale and large-scale magnetic field is briefly outlined.

  11. Electron Induced Surface Reactions of cis-Pt(CO)2Cl2: A Route to Focused Electron Beam Induced Deposition of Pure Pt Nanostructures.

    Science.gov (United States)

    Spencer, Julie A; Wu, Yung-Chien; McElwee-White, Lisa; Fairbrother, D Howard

    2016-07-27

    Using mechanistic data from surface science studies on electron-induced reactions of organometallic precursors, cis-Pt(CO)2Cl2 (1) was designed specifically for use in focused electron beam induced deposition (FEBID) of Pt nanostructures. Electron induced decomposition of adsorbed 1 under ultrahigh vacuum (UHV) conditions proceeds through initial CO loss as determined by in situ X-ray photoelectron spectroscopy and mass spectrometry. Although the Pt-Cl bonds remain intact during the initial decomposition step, larger electron doses induce removal of the residual chloride through an electron-stimulated desorption process. FEBID structures created from cis-Pt(CO)2Cl2 under steady state deposition conditions in an Auger spectrometer were determined to be PtCl2, free of carbon and oxygen. Coupled with the electron stimulated removal of chlorine demonstrated in the UHV experiments, the Auger deposition data establish a route to FEBID of pure Pt. Results from this study demonstrate that structure-activity relationships can be used to design new precursors specifically for FEBID.

  12. Formation of interstitial-vacancy pairs by electronic excitation in pure ionic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Noriaki; Tanimura, Katsumi (Nagoya Univ. (Japan). Dept. of Physics)

    1990-01-01

    We review experiments and theories on defect formation induced by electronic excitation. Emphasis is placed on the microscopic mechanism of F-H pair formation in alkali halides and relevant phenomena in other systems such as alkaline earth fluorides, amorphous silicon dioxide and alkali halide surfaces. Dynamic and thermally-activated formation of the F-H pairs are discussed separately and it is pointed out that these two processes involve relaxation on different adiabatic potential surfaces. The mechanism of the temperature dependence is discussed in some detail. The significance of the value of S/D for the defect formation process in alkali halides, where S is the space between the halogen ion and D is the diameter of a halogen atom, is also discussed. Although understanding of the defect formation processes in systems other than alkali halides is not as deep as in alkali halides, the similarities and differences in the processes in alkali halides and other materials are discussed. Defect formation and sputtering of alkali halides are also compared. (author).

  13. Studies on Electronic Structure and Magnetic Properties of an Organic Magnet with Metallic Mn2+ and Cu2+ Ions

    Institute of Scientific and Technical Information of China (English)

    YAOJian-Guo; PENGGuang-Xiong

    2004-01-01

    The electronic structure and the magnetic properties of the non-pure organic ferromagnetic compound MnCu(pbaOH)(H2O)3 with pbaOH=2-hydroxy-1, 3-propylenebis (oxamato) are studied by using the density-functional theory with local-spin-density approximation. The density of states, total energy, and the spin magnetic moment are calculated. The calculations reveal that the compound MnCu(pbaOH)(H2O)3 has a stable metal-ferromagnetic ground state, and the spin magnetic moment per molecule is 2.208 μa, and the spin magnetic moment is mainly from Mn ionand Cu ion. An antiferromagnetic order is expected and the antiferromagnetic exchange interaction of d-electrons of Cu and Mn passes through the antiferromagnetic interaction between the adjacent O, 0, and N atoms along the path linking the atoms Cu and Mn.

  14. Electron vortex magnetic holes: a nonlinear coherent plasma structure

    CERN Document Server

    Haynes, Christopher T; Camporeale, Enrico; Sundberg, Torbjorn

    2014-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional PIC simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is ...

  15. Experimental Observation of Energetic Electrons during Magnetic Island Merging

    Science.gov (United States)

    Na, Byungkeun; Yoo, Jongsoo; Jara-Almonte, Jonathan; Fox, Will; Yamada, Masaaki; Ji, Hantao

    2015-11-01

    Non-thermal particles have been observed in space as a consequence of magnetic reconnection, but the exact acceleration mechanisms are not well understood. The energization of electrons during magnetic island merging is studied in the Magnetic Reconnection Experiment (MRX). A double-sided electron energy analyzer is developed to simultaneously measure the electron energy distribution in two directions, parallel and anti-parallel to the electron flow. The bias of the selector grid is swept from -30 to 0 V with respect to the floating potential within 1 μs , comparable to the Alfvén time of the typical MRX plasma. Energetic electrons are found inside the magnetic island after island merging is completed. The measured electron tail distribution is well modeled by a high temperature Maxwellian. In the parallel direction, the tail temperature (~ 28 eV) is found to be up to four times higher than the bulk temperature (~ 7 eV). In the anti-parallel direction, a negligible tail population is observed. The measured electron energy distribution is discussed in connection with possible electron acceleration mechanisms.

  16. Magnetic contrast in threshold photoemission electron microscopy

    NARCIS (Netherlands)

    Veghel, Marinus Godefridus Adrianus van

    2004-01-01

    In threshold photoemission electron microscopy (threshold PEEM), photoelectrons are excited by UV photons with an energy just above the photoemission threshold. The lateral intensity distribution of these electrons is then imaged by an electrostatic lens system. In this thesis, the possibilities o

  17. Probing Nanoscale Electronic and Magnetic Interaction with Scanning Tunneling Spectroscopy

    DEFF Research Database (Denmark)

    Bork, Jakob

    This thesis is concerned with fundamental research into electronic and magnetic interaction on the nanoscale. From small metallic and magnetic islands and layers to single atoms. The research revolves around magnetic interaction probed through the spectroscopic capabilities of the scanning....... This is related to research in correlated electron materials such as studies of phase transitions in heavy fermion compounds and magnetic interaction in spintronic research. The capping of cobalt islands on Cu(111) with silver is investigated with STM and photoemission spectroscopy. It is shown that at low...... coverage the silver preferably nucleates on top of the bilayer high cobalt islands compared to directly on the Cu(111) substrate. Furthermore, the silver forms a combination of a reconstruction and a Moire pattern which is investigated with low-energy electron diraction and spectroscopic STM mapping at 6...

  18. Fast Magnetic Reconnection Due to Anisotropic Electron Pressure

    CERN Document Server

    Cassak, P A; Fermo, R L; Beidler, M T; Shay, M A; Swisdak, M; Drake, J F; Karimabadi, H

    2015-01-01

    A new regime of fast magnetic reconnection with an out-of-plane (guide) magnetic field is reported in which the key role is played by an electron pressure anisotropy described by the Chew-Goldberger-Low gyrotropic equations of state in the generalized Ohm's law, which even dominates the Hall term. A description of the physical cause of this behavior is provided and two-dimensional fluid simulations are used to confirm the results. The electron pressure anisotropy causes the out-of-plane magnetic field to develop a quadrupole structure of opposite polarity to the Hall magnetic field and gives rise to dispersive waves. In addition to being important for understanding what causes reconnection to be fast, this mechanism should dominate in plasmas with low plasma beta and a high in-plane plasma beta with electron temperature comparable to or larger than ion temperature, so it could be relevant in the solar wind and some tokamaks.

  19. Electronic structure and magnetism of ThFeAsN

    Science.gov (United States)

    Wang, Guangtao; Shi, Xianbiao

    2016-03-01

    The electronic structure and magnetic properties of ThFeAsN, a newly discovered superconductor, are investigated by means of first-principles calculations. ThFeAsN shares electronic structure and magnetic properties similar to those of LaOFeAs. Its calculated ground state is the stripe antiferromagnetic state. The hole-like Fermi surfaces (FSs) along the Γ\\text-Z line largely overlap with the electron-like FS along the M\\text-A line with the vector q= (π, π, 0) . Such significant FS nesting induces a peak of the bare susceptibility χ0(q ) at the M-point.

  20. Electron transport through nuclear pasta in magnetized neutron stars

    CERN Document Server

    Yakovlev, D G

    2015-01-01

    We present a simple model for electron transport in a possible layer of exotic nuclear clusters (in the so called nuclear pasta layer) between the crust and liquid core of a strongly magnetized neutron star. The electron transport there can be strongly anisotropic and gyrotropic. The anisotropy is produced by different electron effective collision frequencies along and across local symmetry axis in domains of exotic ordered nuclear clusters and by complicated effects of the magnetic field. We also calculate averaged kinetic coefficients in case local domains are freely oriented. Possible applications of the obtained results and open problems are outlined.

  1. Electronic, transport, and magnetic properties of punctured carbon nanotubes

    Science.gov (United States)

    dos Santos, Jeová Calisto; de Vasconcelos, Fabrício Morais; de Aguiar, Acrísio Lins; Alves, Tayroni Francisco de Alencar; Meunier, Vincent; Girão, Eduardo Costa

    2016-12-01

    We use a spin-polarized tight-binding model Hamiltonian and the Landauer transport formalism to investigate the electronic transport properties of carbon nanotubes where different types of holes have been drilled through their sidewalls. We focus on zigzag edged defects with different atomic configurations since these systems enable the emergence of magnetic properties. We show that a number of hole geometries, magnetic states, and electronic spins yield attractive transport properties, such as ON/OFF switching for the electronic current, and nontrivial dependence of transmission with hole size.

  2. GGA+U investigations of impurity d-electrons effects on the electronic and magnetic properties of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Ul Haq, Bakhtiar [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Ahmed, R., E-mail: rashidahmed@utm.my [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Shaari, A. [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, UTM Skudai, 81310 Johor (Malaysia); Goumri-Said, Souraya, E-mail: Souraya.Goumri-Said@kaust.edu.sa [Physical Science Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900 (Saudi Arabia)

    2014-08-01

    Stimulation of novel features in ZnO by impurity electrons has attracted a remarkable attention of researchers from the past decade. Consequently, ZnO has found several applications in the field of spintronics and optoelectronics. We report, the effect of 3d-(V, Ag) electrons on the properties of ZnO in stable wurtzite (WZ) and metastable zincblende (ZB) phase using the density functional theory. Introduction of V-3d electrons was found to induce a high magnetic moment value of 5.22 in WZ and 3.26 in the ZB phase, and moreover transform the semiconductor character of ZnO into a metallic nature. Ag-d electrons result in the p-type half-metallic nature of ZnO with a weak ferromagnetic background. Our calculations for ground-state magnetic ordering show that ZnO in the presence of impure 3d-(V, Ag) electrons favors ferromagnetic ordering, and obey the double exchange mechanism. However, impurity atoms have very marginal effect on the lattice parameters of ZnO, thereby exposing its potential to absorb the impurity atoms in high concentration. - Graphical abstract: - Highlights: • Doping 3d-(V, Ag) electrons on ZnO factors FM order. • The use of GGA+U is more accurate and complete than pure DFT. • The electronic structure of Ag and V:ZnO is drastically changed. • Spin-density maps show the polarization of O and Zn due to Ag and V doping.

  3. Electronic and magnetic properties of modified silicene/graphene hybrid: Ab initio study

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, Suman; Jana, Debnarayan, E-mail: cujanad@yahoo.com

    2016-11-01

    Among other two-dimensional (2D) novel materials, graphene and silicene both have drawn intense research interest among the researchers because they possess some unique intriguing properties which can change the scenario of the current electronic industry. In this work we have studied the electronic and the magnetic properties of a new kind of materials which is the hybrid of these two materials. Density functional theory (DFT) has been employed to calculate the relevant electronic and magnetic properties of this hybrid material. The pristine structure is modified by substitutional doping or by creating vacancy (Y-X, where one Y atom (Si or C) has been replaced by one X atom (B, N, Al, P or void)). The calculations have revealed that void systems are unstable while Si-B and Si-N are most stable ones. It has been noticed that some of these doped structures are magnetic in nature having induced mid-gap states in the system. In particular, Si-void structure is unstable yet it possess the highest magnetic moment of the order of 4 μ{sub B} (μ{sub B} being the Bohr magneton). The estimated band gaps of modified silicene/graphene hybrid from spin polarized partial density of states (PDOS) vary between 1.43–2.38 eV and 1.58–2.50 eV for spin-up and spin-down channel respectively. The implication of midgap states has been critically analysed in the light of magnetic nature. This study may be useful to build hybrid spintronic devices with controllable gap for spin up and spin down states. - Graphical abstract: We have studied the electronic and magnetic properties of silicene/graphene hybrid by employing density functional theory (DFT). - Highlights: • Electronic and magnetic properties of two dimensional graphene/silicene hybrid have been explored. • There is no magnetism in the system for a single carbon atom vacancy. • A net magnetic moment of 4.0 Bohr magneton is observed for a single silicon atom vacancy. • Unpaired electrons introduce mid-gap states which

  4. Analysis of magnetic electron lens with secant hyperbolic field distribution

    CERN Document Server

    Pany, S S; Dubey, B P

    2014-01-01

    Electron-optical imaging instruments like Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) use specially designed solenoid electromagnets for focusing of electron beam probe. Indicators of imaging performance of these instruments, like spatial resolution, have strong correlation with focal characteristics of the magnetic lenses which in turn have been shown to be functions of the spatial distribution of axial magnetic field generated by them. Owing to complicated design of practical lenses, empirical mathematical expressions are deemed convenient for use in physics based calculations of their focal properties. So, degree of closeness of such models to the actual field distribution determines accuracy of the calculations. Mathematical models proposed by Glaser[1] and Ramberg[1] have historically been put into extensive use. In this paper the authors discuss one such model with secant-hyperbolic type magnetic field distribution function, and present a comparison among these models, ...

  5. Beam induced electron cloud resonances in dipole magnetic fields

    Science.gov (United States)

    Calvey, J. R.; Hartung, W.; Makita, J.; Venturini, M.

    2016-07-01

    The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. Both resonances have been studied directly in dipole fields using retarding field analyzers installed in the Cornell Electron Storage Ring. These measurements are supported by both analytical models and computer simulations.

  6. Energetic electrons associated with magnetic reconnection in the magnetic cloud boundary layer.

    Science.gov (United States)

    Wang, Y; Wei, F S; Feng, X S; Zhang, S H; Zuo, P B; Sun, T R

    2010-11-05

    Here is reported in situ observation of energetic electrons (∼100-500 keV) associated with magnetic reconnection in the solar wind by the ACE and Wind spacecraft. The properties of this magnetic cloud driving reconnection and the associated energetic electron acceleration problem are discussed. Further analyses indicate that the electric field acceleration and Fermi-type mechanism are two fundamental elements in the electron acceleration processes and the trapping effect of the specific magnetic field configuration maintains the acceleration status that increases the totally gained energy.

  7. Study of electron transport across the magnetic filter of NIO1 negative ion source

    Science.gov (United States)

    Veltri, P.; Sartori, E.; Cavenago, M.; Serianni, G.; Barbisan, M.; Zaniol, B.

    2017-08-01

    In the framework of the accompanying activities in support to the ITER NBI test facility, a relatively compact radiofrequency (RF) ion source, named NIO1 (Negative Ion Optimization, phase 1) was developed in Padua, Italy, in collaboration between Consorzio RFX and INFN. Negative hydrogen ions are formed in a cold, inductively coupled plasma with a 2MHz, 2.5 kW external antenna. A low electron energy is necessary to increase the survival probability of negative ions in the proximity of the extraction area. This goal is accomplished by means of a transversal magnetic field, confining the high energy electrons better than the colder electrons. In NIO1, this filter field can cover different topologies, exploiting different set of magnets and high current paths. In this contribution we study the property of the plasma in the vicinity of the extraction region for two different B field configurations. For this experiment the source was operated in pure volume conditions, in hydrogen and oxygen plasmas. The experimental data, measured by spectroscopic means, is interpreted also with the support of finite element analyses simulations of the magnetic field and a dedicated particle in cell (PIC) numerical model for the electron transport across it, including Coulomb and gas collisions.

  8. Magnetic resonance imaging and pathological characteristics of pure mucinous carcinoma in the breast according to echogenicity on ultrasonography

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Young Gyung; Kim, Eun Kyung; Kim, Min Jung; Yoon, JUng Hyun; Moon, Hee Jung [Dept. of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul (Korea, Republic of)

    2017-04-15

    The aim of this study was to explore the clinical and pathological characteristics of pure mucinous breast carcinoma (PMBC) according to internal echogenicity on ultrasonography (US). Thirty-three patients with PMBC diagnosed at surgery were included in this study. Cases of PMBC were classified according to internal echogenicity on US. The imaging features on magnetic resonance (MR) imaging and clinicohistopathological characteristics were compared between the hypoechogenic and the isoechogenic to hyperechogenic groups. Eleven cases of PMBC (33.3%) exhibited hypoechogenicity on US, while 22 cases (66.7%) exhibited isoechogenicity or hyperechogenicity. Of the isoechogenic to hyperechogenic PMBCs, 95.5% showed a high signal on T2-weighted images, which was a significantly greater percentage than was observed for the hypoechogenic group (54.5%) (P=0.010). Of the hypoechogenic PMBCs, 63.6% showed a washout pattern in the delayed phase, which was substantially more than the result of 23.8% observed for the isoechogenic to hyperechogenic PMBCs (P=0.053). PMBCs with isoechogenicity or hyperechogenicity were more likely to show a high signal intensity on T2-weighted images than hypoechogenic PMBCs. However, other MR imaging and clinicohistopathological characteristics were not significantly different between the two groups.

  9. Iterative reconstruction of magnetic induction using Lorentz transmission electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Phatak, C., E-mail: cd@anl.gov [Materials Science Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Gürsoy, D. [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2015-03-15

    Intense ongoing research on complex nanomagnetic structures requires a fundamental understanding of the 3D magnetization and the stray fields around the nano-objects. 3D visualization of such fields offers the best way to achieve this. Lorentz transmission electron microscopy provides a suitable combination of high resolution and ability to quantitatively visualize the magnetization vectors using phase retrieval methods. In this paper, we present a formalism to represent the magnetic phase shift of electrons as a Radon transform of the magnetic induction of the sample. Using this formalism, we then present the application of common tomographic methods particularly the iterative methods, to reconstruct the 3D components of the vector field. We present an analysis of the effect of missing wedge and the limited angular sampling as well as reconstruction of complex 3D magnetization in a nanowire using simulations. - Highlights: • We present a formalism to represent electron-optical magnetic phase shift as a Radon transform of the 3D magnetic induction of the nano-object. • We have analyzed four different tomographic reconstruction methods for vectorial data reconstruction. • Reconstruction methods were tested for varying experimental limitations such as limited tilt range and limited angular sampling. • The analysis showed that Gridrec and SIRT methods performed better with lower errors than other reconstruction methods.

  10. Regimes of the electron diffusion region in magnetic reconnection.

    Science.gov (United States)

    Le, A; Egedal, J; Ohia, O; Daughton, W; Karimabadi, H; Lukin, V S

    2013-03-29

    The electron diffusion region during magnetic reconnection lies in different regimes depending on the pressure anisotropy, which is regulated by the properties of thermal electron orbits. In kinetic simulations at the weakest guide fields, pitch angle mixing in velocity space causes the outflow electron pressure to become nearly isotropic. Above a threshold guide field that depends on a range of parameters, including the normalized electron pressure and the ion-to-electron mass ratio, electron pressure anisotropy develops in the exhaust and supports extended current layers. This new regime with electron current sheets extending to the system size is also reproduced by fluid simulations with an anisotropic closure for the electron pressure. It offers an explanation for recent spacecraft observations.

  11. Localized electron heating during magnetic reconnection in MAST

    Science.gov (United States)

    Yamada, T.; Tanabe, H.; Watanabe, T. G.; Hayashi, Y.; Imazawa, R.; Inomoto, M.; Ono, Y.; Gryaznevich, M.; Scannell, R.; Michael, C.; The MAST Team

    2016-10-01

    Significant increase in the plasma temperature above 1 keV was measured during the kilogauss magnetic field reconnection of two merging toroidal plasmas under the high-guide field and collision-less conditions. The electron temperature was observed to peak significantly at the X-point inside the current sheet, indicating Joule heating caused by the toroidal electric field along the X-line. This peaked temperature increases significantly with the guide field, in agreement with the electron mean-free path calculation. The slow electron heating in the downstream suggests energy conversion from ions to electrons through ion-electron collisions in the bulk plasma as the second electron heating mechanism in the bulk plasma. The electron density profile clearly reveals the electron density pile-up / fast shock structures in the downstream of reconnection, suggesting energy conversion from ion flow energy to ion thermal energy as well as significant ion heating by reconnection outflow.

  12. Modified Fermi Energy of Electrons in a Superhigh Magnetic Field

    CERN Document Server

    Zhu, C; Li, X D; Wang, N; Yuan, J P; Peng, Q H

    2016-01-01

    In this paper, we investigate the electron Landau-level stability and its influence on the electron Fermi energy, $E_{\\rm F}(e)$, in the circumstance of magnetars, which are powered by magnetic field energy. In a magnetar, the Landau levels of degenerate and relativistic electrons are strongly quantized. A new quantity $g_{n}$, the electron Landau-level stability coefficient is introduced. According to the requirement that $g_{n}$ decreases with increasing the magnetic field intensity $B$, the magnetic-field index $\\beta$ in the expression of $E_{\\rm F}(e)$ must be positive. By introducing the Dirac$-\\delta$ function, we deduce a general formulae for the Fermi energy of degenerate and relativistic electrons, and obtain a particular solution to $E_{\\rm F}(e)$ in a superhigh magnetic field. This solution has a low magnetic-field index of $\\beta=1/6$, compared with the previous one, and works when $\\rho\\geq 10^{7}$~g cm$^{-3}$ and $B_{\\rm cr}\\ll B\\leq 10^{17}$~Gauss. By modifying the phase space of relativistic ...

  13. Optical Signatures from Magnetic 2-D Electron Gases in High Magnetic Fields to 60 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Crooker, S.A.; Kikkawa, J.M.; Awschalom, D.D.; Smorchikova, I.P.; Samarth, N.

    1998-11-08

    We present experiments in the 60 Tesla Long-Pulse magnet at the Los Alamos National High Magnetic Field Lab (NHMFL) focusing on the high-field, low temperature photoluminescence (PL) from modulation-doped ZnSe/Zn(Cd,Mn)Se single quantum wells. High-speed charge-coupled array detectors and the long (2 second) duration of the magnet pulse permit continuous acquisition of optical spectra throughout a single magnet shot. High-field PL studies of the magnetic 2D electron gases at temperatures down to 350mK reveal clear intensity oscillations corresponding to integer quantum Hall filling factors, from which we determine the density of the electron gas. At very high magnetic fields, steps in the PL energy are observed which correspond to the partial unlocking of antiferromagnetically bound pairs of Mn2+ spins.

  14. Tailoring of electron flow current in magnetically insulated transmission lines

    Directory of Open Access Journals (Sweden)

    J. P. Martin

    2009-03-01

    Full Text Available It is desirable to optimize (minimizing both the inductance and electron flow the magnetically insulated vacuum sections of low impedance pulsed-power drivers. The goal of low inductance is understandable from basic efficiency arguments. The goal of low electron flow results from two observations: (1 flowing electrons generally do not deliver energy to (or even reach most loads, and thus constitute a loss mechanism; (2 energetic electrons deposited in a small area can cause anode damage and anode plasma formation. Low inductance and low electron flow are competing goals; an optimized system requires a balance of the two. While magnetically insulated systems are generally forgiving, there are times when optimization is crucial. For example, in large pulsed-power drivers used to energize high energy density physics loads, the electron flow as a fraction of total current is small, but that flow often reaches the anode in relatively small regions. If the anode temperature becomes high enough to desorb gas, the resulting plasma initiates a gap closure process that can impact system performance. Magnetic-pressure driven (z pinches and material equation of state loads behave like a fixed inductor for much of the drive pulse. It is clear that neither fixed gap nor constant-impedance transmission lines are optimal for driving inductive loads. This work shows a technique for developing the optimal impedance profile for the magnetically insulated section of a high-current driver. Particle-in-cell calculations are used to validate the impedance profiles developed in a radial disk magnetically insulated transmission line geometry. The input parameters are the spacing and location of the minimum gap, the effective load inductance, and the desired electron flow profile. The radial electron flow profiles from these simulations are in good agreement with theoretical predictions when driven at relatively high voltage (i.e., V≥2  MV.

  15. Three-Electron Quantum Dots in Zero Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    By using the exact diagonalization method, a system of three electrons confined in a parabolic quantum dot in zero magnetic field is studied. The ground-state electronic structures and orbital and spin angular momenta transitions as a function of the confined strength are investigated. We find that the confinement may cause accidental degeneracies between levels with different low-lying states and the inversion of the energy values. The present results are useful to understanding the optical properties and internal electron-electron correlations of quantum dot materials.

  16. Electronic structure, magnetic and structural properties of Ni doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Shalendra, E-mail: shailuphy@gmail.com [School of Materials Science and Engineering, Changwon National University, 9 Sarim dong, Changwon 641 773 (Korea, Republic of); Vats, Prashant [Material Science Research Laboratory, Department of Physics, S. V. College, Aligarh 202001, Uttar Pradesh (India); Gautam, S. [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Gupta, V.P.; Verma, K.D. [Material Science Research Laboratory, Department of Physics, S. V. College, Aligarh 202001, Uttar Pradesh (India); Chae, K.H. [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Hashim, Mohd [Department of Applied Physics, Aligarh Muslim University, Aligarh 202-002 (India); Choi, H.K., E-mail: hkchoi99@changwon.ac.kr [Department of Mechatronics Convergence, College of Engineering, Changwon National University, Changwon 641 773 (Korea, Republic of)

    2014-11-15

    Highlights: • XRD, and HR-TEM results show the single phase nature of Ni doped ZnO nanoparticles. • dc magnetization results indicate the RT-FM in Ni doped ZnO nanoparticles. • Ni L{sub 3,2} edge NEXAFS spectra infer that Ni ions are in +2 valence state. • O K edge NEXAFS spectra show that O vacancy increases with Ni doping in ZnO. - Abstract: We report structural, magnetic and electronic structural properties of Ni doped ZnO nanoparticles prepared by auto-combustion method. The prepared nanoparticles were characterized by using X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, and dc magnetization measurements. The XRD and HR-TEM results indicate that Ni doped ZnO nanoparticles have single phase nature with wurtzite lattice and exclude the presence of secondary phase. NEXAFS measurements performed at Ni L{sub 3,2}-edges indicates that Ni ions are in +2 valence state and exclude the presence of Ni metal clusters. O K-edge NEXAFS spectra indicate an increase in oxygen vacancies with Ni-doping, while Zn L{sub 3,2}-edge show the absence of Zn-vacancies. The magnetization measurements performed at room temperature shows that pure and Ni doped ZnO exhibits ferromagnetic behavior.

  17. Electron/ion whistler instabilities and magnetic noise bursts

    Science.gov (United States)

    Akimoto, K.; Gary, S. Peter; Omidi, N.

    1987-01-01

    Two whistler instabilities are investigated by means of the linear Vlasov dispersion equation. They are called the electron/ion parallel and oblique whistler instabilities, and are driven by electron/ion relative drifts along the magnetic field. It is demonstrated that the enhanced fluctuations from these instabilities can explain several properties of magnetic noise bursts in and near the plasma sheet in the presence of ion beams and/or field-aligned currents. At sufficiently high plasma beta, these instabilities may affect the current system in the magnetotail.

  18. Magnetoresistance of Electrons Channelled by Microscopic Magnetic Field Modulation

    Institute of Scientific and Technical Information of China (English)

    DAI Bo; LIU Xiao-Xia; LEI Yong; Alain Nogaret

    2009-01-01

    We report the magnetoresistance of two-dimensional electron gas,which is made of GaAs based epitaxial multilayers and laterally subjected to a periodic magnetic field.The modulation field is produced by an array of submicrometre ferromagnets fabricated at the surface of the heterostructure.The magnetoresistance of about 20% is found at low temperature 80K.The measurement is in quantitative agreement with semiclassical simulations,which reveal that the magnetoresistance is due to electrons trapped in snake orbits along lines of zero magnetic field.

  19. Unusual electronic and magnetic responses from sulfur-decorated graphene

    Science.gov (United States)

    Hwang, Choongyu; Cybart, S. A.; Wu, S. M.; Dynes, R. C.; Shin, S. J.; Haller, E. E.; Kim, S.; Kim, K.; Min, B. I.; Rappoport, T. G.; Jozwiak, C.; Fedorov, A. V.; Mo, S.-K.; Castro Neto, A. H.; Lee, D.-H.; Lanzara, A.

    Interactions between two different materials can produce strong electronic correlations that do not exist when each material stands alone. We search for such correlations from graphene, a non-magnetic semi-metal, decorated by sulfur, a diamagnetic insulator, using angle-resolved photoemission spectroscopy and magneto-transport measurements. Sulfur-decorated graphene exhibits unusual electronic and magnetic responses that are clearly distinguished from clean graphene. Our findings provide intriguing insights on the search for novel quantum phases in graphene-based compounds.

  20. Primordial Magnetic Fields, Right Electrons, and the Abelian Anomaly

    CERN Document Server

    Joyce, M

    1997-01-01

    In the standard model there are charges with abelian anomaly only (e.g. right-handed electron number) which are effectively conserved in the early universe until some time shortly before the electroweak scale. A state at finite chemical potential of such a charge, possibly arising due to asymmetries produced at the GUT scale, is unstable to the generation of hypercharge magnetic field. We argue that quite large magnetic fields ($\\sim 10^{23}$ gauss at $T\\sim 3$ TeV with typical inhomogeneity scale up to $\\sim interest, potentially acting as seeds for amplification to larger scale magnetic fields through non-linear mechanisms.

  1. Electronic and Magnetic Properties of Small Iridium Clusters

    Institute of Scientific and Technical Information of China (English)

    KUANG Xiang-jun

    2004-01-01

    The electronic and magnetic properties of small IrN clusters (N=5, 6, 9, 13, and 19 ) are studied by using the discrete-variational local-spin-density-functional method. The equilibrium bond length in the chosen geometry for IrN clusters are determined and show bond contraction compared with the bulk interatomic spacing. The clusters with magnetic ground state have ferromagnetic interaction and their average magnetic moment per atom has a complex size dependence. At last, the reactivity of IrN clusters toward H2, N2 and CO molecules is predicted.

  2. Simulation of magnetic circular dichroism in the electron microscope

    Science.gov (United States)

    Rubino, Stefano; Schattschneider, Peter; Rusz, Jan; Verbeeck, Johan; Leifer, Klaus

    2010-12-01

    As electron energy-loss spectroscopy (EELS) and x-ray absorption spectroscopy (XAS) probe the same transitions from core-shell states to unoccupied states above the Fermi energy, it should always be possible to apply the two techniques to the same physical phenomena, such as magnetic dichroism, and obtain the same information. Indeed, the similarity in the expression of the electron and x-ray cross-sections had been already exploited to prove the equivalence of x-ray magnetic linear dichroism and anisotropy in EELS, by noting that the polarization vector of a photon plays the same role as the momentum transfer in electron scattering. Recently, the same was proven true for x-ray magnetic circular dichroism (XMCD) by establishing a new TEM technique called EMCD (electron energy-loss magnetic chiral dichroism) (Schattschneider P et al 2006 Nature 441 486-8), which makes use of special electron scattering conditions to force the absorption of a circularly polarized virtual photon. The intrinsic advantage of EMCD over XMCD is the high spatial resolution of electron microscopes, which are readily available. Among the particular obstacles in EMCD that do not exist for synchrotron radiation, is the notoriously low signal and the very particular scattering conditions necessary to observe a chiral dichroic signal. In spite of that, impressive progress has been made in recent years. The signal strength could be considerably increased, and some innovations such as using a convergent beam have been introduced. EMCD has evolved into several techniques, which make full use of the versatility of the TEM and energy filtering, spectroscopy or STEM conditions (Rubino S 2007 Magnetic circular dichroism in the transmission electron microscope PhD Thesis Vienna University of Technology, Vienna, Austria).

  3. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    Science.gov (United States)

    Haynes, Christopher T.; Burgess, David; Camporeale, Enrico; Sundberg, Torbjorn

    2015-01-01

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  4. Electron vortex magnetic holes: A nonlinear coherent plasma structure

    Energy Technology Data Exchange (ETDEWEB)

    Haynes, Christopher T., E-mail: c.t.haynes@qmul.ac.uk; Burgess, David; Sundberg, Torbjorn [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Camporeale, Enrico [Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)

    2015-01-15

    We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

  5. An in-plane magnetic chiral dichroism approach for measurement of intrinsic magnetic signals using transmitted electrons.

    Science.gov (United States)

    Song, Dongsheng; Tavabi, Amir H; Li, Zi-An; Kovács, András; Rusz, Ján; Huang, Wenting; Richter, Gunther; Dunin-Borkowski, Rafal E; Zhu, Jing

    2017-05-15

    Electron energy-loss magnetic chiral dichroism is a powerful technique that allows the local magnetic properties of materials to be measured quantitatively with close-to-atomic spatial resolution and element specificity in the transmission electron microscope. Until now, the technique has been restricted to measurements of the magnetic circular dichroism signal in the electron beam direction. However, the intrinsic magnetization directions of thin samples are often oriented in the specimen plane, especially when they are examined in magnetic-field-free conditions in the transmission electron microscope. Here, we introduce an approach that allows in-plane magnetic signals to be measured using electron magnetic chiral dichroism by selecting a specific diffraction geometry. We compare experimental results recorded from a cobalt nanoplate with simulations to demonstrate that an electron magnetic chiral dichroism signal originating from in-plane magnetization can be detected successfully.

  6. Surface magnetism Correlation of structural, electronic and chemical properties with magnetic behavior

    CERN Document Server

    Getzlaff, Mathias

    2010-01-01

    This volume reviews on selected aspects related to surface magnetism, a field of extraordinary interest during the last decade. The special emphasis is set to the correlation of structural, electronic and magnetic properties in rare earth metal systems and ferromagnetic transition metals. This is made possible by the combination of electron emission techniques (spin polarized photoelectron spectroscopy, magnetic dichroism in photoemission and spin polarized metastable deexcitation spectroscopy) and local probes with high lateral resolution down to the atomic scale (spin polarized scanning tunneling microscopy / spectroscopy).

  7. Phase-space dynamics of runaway electrons in magnetic fields

    Science.gov (United States)

    Guo, Zehua; McDevitt, Christopher J.; Tang, Xian-Zhu

    2017-04-01

    Dynamics of runaway electrons in magnetic fields are governed by the competition of three dominant physics: parallel electric field acceleration, Coulomb collision, and synchrotron radiation. Examination of the energy and pitch-angle flows reveals that the presence of local vortex structure and global circulation is crucial to the saturation of primary runaway electrons. Models for the vortex structure, which has an O-point to X-point connection, and the bump of runaway electron distribution in energy space have been developed and compared against the simulation data. Identification of these velocity-space structures opens a new venue to re-examine the conventional understanding of runaway electron dynamics in magnetic fields.

  8. Imaging of magnetic and electric fields by electron microscopy.

    Science.gov (United States)

    Zweck, Josef

    2016-10-12

    Nanostructured materials become more and more a part of our daily life, partly as self-assembled particles or artificially patterned. These nanostructures often possess intrinsic magnetic and/or electric fields which determine (at least partially) their physical properties. Therefore it is important to be able to measure these fields reliably on a nanometre scale. A rather common instrument for the investigation of these fields is the transmission electron microscope as it offers high spatial resolution. The use of an electron microscope to image electric and magnetic fields on a micron down to sub-nanometre scale is treated in detail for transmission electron microscopes (TEM) and scanning transmission electron microscopes (STEM). The formation of contrast is described for the most common imaging modes, the specific advantages and disadvantages of each technique are discussed and examples are given. In addition, the experimental requirements for the use of the techniques described are listed and explained.

  9. Imaging of magnetic and electric fields by electron microscopy

    Science.gov (United States)

    Zweck, Josef

    2016-10-01

    Nanostructured materials become more and more a part of our daily life, partly as self-assembled particles or artificially patterned. These nanostructures often possess intrinsic magnetic and/or electric fields which determine (at least partially) their physical properties. Therefore it is important to be able to measure these fields reliably on a nanometre scale. A rather common instrument for the investigation of these fields is the transmission electron microscope as it offers high spatial resolution. The use of an electron microscope to image electric and magnetic fields on a micron down to sub-nanometre scale is treated in detail for transmission electron microscopes (TEM) and scanning transmission electron microscopes (STEM). The formation of contrast is described for the most common imaging modes, the specific advantages and disadvantages of each technique are discussed and examples are given. In addition, the experimental requirements for the use of the techniques described are listed and explained.

  10. Electronic structure and magnetic anisotropy of CrO_2

    OpenAIRE

    Toropova, A.; Kotliar, G.; Savrasov, S. Y.; Oudovenko, V. S.

    2004-01-01

    The problem of importance of strong correlations for the electronic structure, transport and magnetic properties of half--metallic ferromagnetic CrO_2 is addressed by performing density functional electronic structure calculations in the local spin density approximation (LSDA) as well as using the LSDA+U method. It is shown that the corresponding low--temperature experimental data are best fitted without accounting for the Hubbard U corrections. We conclude that the ordered phase of CrO$_2 is...

  11. Focused electron beam induced deposition of magnetic nanostructures

    Science.gov (United States)

    de Teresa, Jose M.

    2011-03-01

    Nanopatterning strategies of magnetic materials normally rely on standard techniques such as electron-beam lithography using electron-sensitive resists. Focused electron beam induced deposition (FEBID) is currently being investigated as an alternative single-step route to produce functional magnetic nanostructures. Thus, Co-based and Fe-based precursors have been recently investigated for the growth of magnetic nanostructures by FEBID. In the present contribution, I will give an overview of the existing literature on magnetic nanostructures by FEBID and I will focus on the growth of Co nanostructures by FEBID using Co 2 (CO)8 as precursor gas. The Co content in the nanostructures can reach 95%. Magnetotransport experiments indicate that full metallic behaviour is displayed with relatively low residual resistivity and standard anisotropic magnetoresistance (0.8%). The coercive field of nanowires with changing aspect ratio has been determined in nanowires with width down to 150 nm by means of Magneto-optical Kerr Effect and the magnetization reversal has been imaged by means of Magnetic Force Microscopy, Scanning Transmission X-ray Microscopy as well as Lorentz Microscopy experiments. Nano-Hall probes have been grown with remarkable minimum detectable magnetic flux. Noticeably, it has been found that the domain-wall propagation field is lower than the domain-wall nucleation field in L-shaped nanowires, with potential applications in magnetic logic, sensing and storage. The spin polarization of these Co nanodeposits has been determined through Andreev-Reflection experiments in ferromagnetic-superconducting nanocontacts and amounts to 35%. Recent results obtained in Fe-based nanostructures by FEBID using Fe 2 (CO)9 precursor will be also presented. I acknowledge the collaboration in this field with A. Fernandez-Pacheco, R. Cordoba, L. Serrano, S. Sangiao, L.A. Rodriguez, C. Magen, E. Snoeck, L. Morellon, M.R. Ibarra.

  12. Optimal electron, phonon, and magnetic characteristics for low energy thermally induced magnetization switching

    Energy Technology Data Exchange (ETDEWEB)

    Atxitia, U., E-mail: Unai.Atxitia@uni-konstanz.de [Fachbereich Physik, Universität Konstanz, D-78457 Konstanz (Germany); Zukunftskolleg, Universität Konstanz, D-78457 Konstanz (Germany); Ostler, T. A., E-mail: t.ostler@exeter.ac.uk [Department of Physics, University of York, York YO105DD (United Kingdom); College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, Devon EX4 4SB (United Kingdom); Chantrell, R. W. [Department of Physics, University of York, York YO105DD (United Kingdom); Chubykalo-Fesenko, O. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain)

    2015-11-09

    Using large-scale computer simulations, we thoroughly study the minimum energy required to thermally induced magnetization switching (TIMS) after the application of a femtosecond heat pulse in transition metal-rare earth ferrimagnetic alloys. We find that for an energy efficient TIMS, a low ferrimagnetic net magnetization with a strong temperature dependence is the relevant factor for the magnetic system. For the lattice and electron systems, the key physics for efficient TIMS is a large electron-phonon relaxation time. Importantly, we show that as the cooling time of the heated electrons is increased, the minimum power required to produce TIMS can be reduced by an order of magnitude. Our results show the way to low power TIMS by appropriate engineering of magnetic heterostructures.

  13. Cooling force on ions in a magnetized electron plasma

    CERN Document Server

    Nersisyan, H B

    2011-01-01

    Electron cooling is a well-established method to improve the phase space quality of ion beams in storage rings. In the common rest frame of the ion and the electron beam the ion is subjected to a drag force and it experiences a loss or a gain of energy which eventually reduces the energy spread of the ion beam. A calculation of this process is complicated as the electron velocity distribution is anisotropic and the cooling process takes place in a magnetic field which guides the electrons. In this paper the cooling force is calculated in a model of binary collisions (BC) between ions and magnetized electrons, in which the Coulomb interaction is treated up to second order as a perturbation to the helical motion of the electrons. The calculations are done with the help of an improved BC theory which is uniformly valid for any strength of the magnetic field and where the second-order two-body forces are treated in the interaction in Fourier space without specifying the interaction potential. The cooling force is...

  14. Structural, electronic and magnetic properties of MnB2

    Indian Academy of Sciences (India)

    R Masrour; E K Hlil; M Hamedoun; A Benyoussef; O Mounkachi; H El Moussaoui

    2015-08-01

    The self-consistent ab-initio calculations, based on density functional theory approach and using the full potential linear augmented plane wave method, are performed to investigate both electronic and magnetic properties of the MnB2 compounds. Polarized spin and spin–orbit coupling are included in calculations within the framework of the ferromagnetic state between two adjacent Mn atoms. Magnetic moment considered to lie along the (001) axes are computed. The antiferromagnetic and ferromagnetic energies of MnB2 systems are obtained. Obtained data from ab-initio calculations are used as input for the high-temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The exchange interactions between the magnetic atoms Mn–Mn in MnB2 are established by using the mean field theory. The HTSEs of the magnetic susceptibility with the magnetic moments in MnB2 (Mn) through Ising model is given. The critical temperature C (K) is obtained by HTSEs applied to the magnetic susceptibility series combined with the Padé approximant method. The critical exponent associated with the magnetic susceptibility is deduced as well.

  15. Electron Whistler Mode Waves Associated with Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; YU Bin; GUO Guang-Hai; ZHAO Bo

    2011-01-01

    @@ The results of particle-in-cell (PIC) simulations are presented on the evolution of the electron whistler waves during the collisionless magnetic reconnection.The simulation results show that the electron whistler waves with frequency higher than the lower hybrid frequency are found to occur in the electrons outflow region.Moreover, the present results indicate that these electron whistler waves with high-frequency in the region greater than an ion inertial scale of the x-line are irrelevant to the fast reconnection, but are generated as a result of the reconnection processes.%The results of particle-in-cell (PIC) simulations are presented on the evolution of the electron whistler waves during the collisionless magnetic reconnection. The simulation results show that the electron whistler waves with frequency higher than the lower hybrid frequency are found to occur in the electrons outflow region. Moreover,the present results indicate that these electron whistler waves with high-frequency in the region greater than an ion inertial scale of the x-line are irrelevant to the fast reconnection, but are generated as a result of the reconnection processes.

  16. Fast Transverse Beam Instability Caused by Electron Cloud Trapped in Combined Function Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, Sergey [Univ. of Chicago, IL (United States)

    2017-03-01

    Electron cloud instabilities affect the performance of many circular high-intensity particle accelerators. They usually have a fast growth rate and might lead to an increase of the transverse emittance and beam loss. A peculiar example of such an instability is observed in the Fermilab Recycler proton storage ring. Although this instability might pose a challenge for future intensity upgrades, its nature had not been completely understood. The phenomena has been studied experimentally by comparing the dynamics of stable and unstable beam, numerically by simulating the build-up of the electron cloud and its interaction with the beam, and analytically by constructing a model of an electron cloud driven instability with the electrons trapped in combined function dipoles. Stabilization of the beam by a clearing bunch reveals that the instability is caused by the electron cloud, trapped in beam optics magnets. Measurements of microwave propagation confirm the presence of the cloud in the combined function dipoles. Numerical simulations show that up to 10$^{-2}$ of the particles can be trapped by their magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a combined function dipole this multi-turn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The estimated fast instability growth rate of about 30 revolutions and low mode frequency of 0.4 MHz are consistent with experimental observations and agree with the simulations. The created instability model allows investigating the beam stability for the future intensity upgrades.

  17. Electronic and magnetic properties of pristine and hydrogenated borophene nanoribbons

    Science.gov (United States)

    Meng, Fanchen; Chen, Xiangnan; Sun, Songsong; He, Jian

    2017-07-01

    The groundbreaking works in graphene and graphene nanoribbons (GNRs) over the past decade, and the very recent discovery of borophene naturally draw attention to the yet-to-be-explored borophene nanoribbons (BNRs). We herein report a density functional theory (DFT) study of the electronic and magnetic properties of BNRs. The foci are the impact of orientation (denoted as BxNRs and ByNRs with their respective periodic orientations along x- and y-axis), ribbon width (Nx, Ny=4-15), and hydrogenation effects on the geometric, electronic and magnetic properties of BNRs. We found that the anisotropic quasi-planar geometric structure of BNR and the edge states largely govern its electronic and magnetic properties. In particular, pristine ByNRs adopt a magnetic ground state, either anti-ferromagnetic (AFM) or ferromagnetic (FM) depending on the ribbon width, while pristine BxNRs are non-magnetic (NM). Upon hydrogenation, all BNRs exhibit NM. Interestingly, both pristine and hydrogenated ByNRs undergo a metal-semiconductor-metal transition at Ny=7, while all BxNRs remain metallic.

  18. Structural, magnetic and electronic structure properties of Co doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Shalendra, E-mail: shailuphy@gmail.com [Institute of Basic Sciences, Changwon National University, Changwon, Gyeongnam 641-773 (Korea, Republic of); School of Materials Science and Engineering, Changwon National University, Changwon, Gyeongnam 641-773 (Korea, Republic of); Song, T.K., E-mail: tksong@changwon.ac.kr [School of Materials Science and Engineering, Changwon National University, Changwon, Gyeongnam 641-773 (Korea, Republic of); Gautam, Sanjeev; Chae, K.H. [Advanced Analysis Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Kim, S.S.; Jang, K.W. [Institute of Basic Sciences, Changwon National University, Changwon, Gyeongnam 641-773 (Korea, Republic of)

    2015-06-15

    Highlights: • XRD and HR-TEM results show the single phase nature of Co doped ZnO nanoparticles. • XMCD and dc magnetization results indicate the RT-FM in Co doped ZnO nanoparticles. • Co L{sub 3,2} NEXAFS spectra infer that Co ions are in 2+ valence state. • O K edge NEXAFS spectra show that O vacancy increases with Co doping in ZnO. - Abstract: We reported structural, magnetic and electronic structure studies of Co doped ZnO nanoparticles. Doping of Co ions in ZnO host matrix has been studied and confirmed using various methods; such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersed X-ray (EDX), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), near edge X-ray absorption fine structure (NEXAFS) spectroscopy, magnetic hysteresis loop measurements and X-ray magnetic circular dichroism (XMCD). From the XRD and HR-TEM results, it is observed that Co doped ZnO nanoparticles have single phase nature with wurtzite structure and exclude the possibility of secondary phase formation. FE-SEM and TEM micrographs show that pure and Co doped nanoparticles are nearly spherical in shape. O K edge NEXAFS spectra indicate that O vacancies increase with Co doping. The Co L{sub 3,2} edge NEXAFS spectra revealed that Co ions are in 2+ valence state. DC magnetization hysteresis loops and XMCD results clearly showed the intrinsic origin of temperature ferromagnetism in Co doped ZnO nanoparticles.

  19. Magnetic anisotropy of polycrystalline magnetoferritin investigated by SQUID and electron magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Moro, F., E-mail: fabrizio.moro@nottingham.ac.uk [School of Physics, University of Nottingham, NG7 2RD Nottingham (United Kingdom); Miguel, R. de [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Jenkins, M. [Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, 50009 Zaragoza (Spain); Gómez-Moreno, C. [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Sells, D.; Tuna, F. [EPSRC National UK EPR Facility, Photon Science Institute, University of Manchester, Manchester, M13 9PL (United Kingdom); McInnes, E.J.L. [EPSRC National UK EPR Facility, Photon Science Institute, University of Manchester, Manchester, M13 9PL (United Kingdom); School of Chemistry, University of Manchester, Manchester M13 9PL (United Kingdom); Lostao, A. [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Fundación ARAID (Spain); Luis, F. [Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-CSIC, 50009 Zaragoza (Spain); Slageren, J. van [Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart (Germany)

    2014-06-01

    Magnetoferritin molecules with an average inorganic core diameter of 5.7±1.6 nm and polycrystalline internal structure were investigated by a combination of transmission electron microscopy, magnetic susceptibility, magnetization, and electron magnetic resonance (EMR) experiments. The temperature and frequency dependence of the magnetic susceptibility allowed for the determination of the magnetic anisotropy on an experimental time scale which spans from seconds to nanoseconds. In addition, angle-dependent EMR experiments were carried out for the determination of the nanoparticle symmetry and internal magnetic field. Due to the large surface to volume ratio, the nanoparticles show larger and uniaxial rather than cubic magnetic anisotropies compared to bulk maghemite and magnetite. - Highlights: • Synthesis of polycristalline magnetoferritin with average particle size of 5.7 nm. • Observation of surface effects and estimation of the anisotropy constant and energy barrier by a combined SQUID and EMR study. • Deviation of Gilbert relaxation of the magnetization in magnetoferritin. • Determination of particle symmetry and internal magnetic field by angle-dependent EMR studies.

  20. Electron holography on remanent magnetization distribution of melt-spun Nd-Fe-B magnets.

    Science.gov (United States)

    Park, Young-Gil; Shindo, Daisuke

    2004-01-01

    Microstructures and magnetic domain structures of melt-spun Nd-Fe-B permanent magnets were investigated in detail by analytical electron microscopy and electron holography. While the crystal orientation of matrix Nd2Fe14B grains was analyzed by nanobeam electron diffraction, precipitates of a few tens of nanometers at grain boundaries were identified to be alpha-Fe by energy-dispersive X-ray spectroscopy. The detailed magnetization distribution in Nd2Fe14B grains and at their boundaries was visualized by electron holography. Ex situ experimentation with an electromagnet revealed that the domain walls in the demagnetized state and remanent states were pinned at grain boundaries, and Fe precipitates at the grain boundary were situated at the center of the closure domain.

  1. Electron-Bernstein Waves in Inhomogeneous Magnetic Fields

    DEFF Research Database (Denmark)

    Armstrong, R. J.; Frederiksen, Å.; Pécseli, Hans

    1984-01-01

    The propagation of small amplitude electron-Bernstein waves in different inhomogeneous magnetic field geometries is investigated experimentally. Wave propagation towards both cut-offs and resonances are considered. The experimental results are supported by a numerical ray-tracing analysis. Spatial...... enhancements of the wave amplitude are interpreted as a result of caustic formation....

  2. Electronic and magnetic properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

    Soon, Yee Yeen; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melaka Campus, 75450 Melaka (Malaysia)

    2015-04-24

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

  3. Ultrasharp magnetization steps in the antiferromagnetic itinerant-electron system LaF e12B6

    Science.gov (United States)

    Diop, L. V. B.; Isnard, O.; Rodríguez-Carvajal, J.

    2016-01-01

    The remarkable intrinsic magnetic properties of the LaF e12B6 compound have been studied by neutron powder diffraction (NPD) and magnetization measurements. The NPD measurement reveals that LaF e12B6 exhibits an antiferromagnetic (AFM) structure that can be described with a magnetic propagation vector of (¼, ¼, ¼) below TN. In the amplitude-modulated model used for the refinement, the Fe magnetic moments are confined to the a b plane with a maximum value of 0.43 μB at 1.5 K. It is shown that the AFM state can be transformed to a ferromagnetic (FM) state via a field-induced first-order transition accompanied with a huge magnetic hysteresis. The LaF e12B6 compound is not only the unique stable R F e12B6 phase, along the rare-earth R series but also presents unique magnetic behavior for a purely 3 d itinerant electron system, including particularly low ordering temperature TN=36 K , remarkably small Fe moment, unusual amplitude-modulated magnetic arrangement, and a multicritical point in the magnetic phase diagram. In addition, we reveal that at 2 K, the AFM-FM transition is abrupt, leading to a large increase of the Fe magnetic moment up to 1.55 μB ; the magnetization curve presents ultrasharp steps, giving rise to an unusual staircaselike behavior.

  4. Resonant tunneling in truly axial symmetry Mn12 single-molecule magnets: sharp crossover between thermally assisted and pure quantum tunneling.

    Science.gov (United States)

    Wernsdorfer, W; Murugesu, M; Christou, G

    2006-02-10

    Magnetization measurements of a truly axial symmetry molecular nanomagnet with a spin ground state of S = 10 show resonant tunneling. This compound has the same magnetic anisotropy as but the molecules are better isolated and the crystals have less disorder and a higher symmetry. Hysteresis loop measurements at several temperatures reveal a well-resolved step fine structure which is due to level crossings of excited states. All step positions can be modeled by a simple spin Hamiltonian. The results establish a sharp crossover between thermally assisted and pure quantum tunneling, as had been previously predicted.

  5. Electron Acceleration in Contracting Magnetic Islands during Solar Flares

    Science.gov (United States)

    Borovikov, D.; Tenishev, V.; Gombosi, T. I.; Guidoni, S. E.; DeVore, C. R.; Karpen, J. T.; Antiochos, S. K.

    2017-01-01

    Electron acceleration in solar flares is well known to be efficient at generating energetic particles that produce the observed bremsstrahlung X-ray spectra. One mechanism proposed to explain the observations is electron acceleration within contracting magnetic islands formed by magnetic reconnection in the flare current sheet. In a previous study, a numerical magnetohydrodynamic simulation of an eruptive solar flare was analyzed to estimate the associated electron acceleration due to island contraction. That analysis used a simple analytical model for the island structure and assumed conservation of the adiabatic invariants of particle motion. In this paper, we perform the first-ever rigorous integration of the guiding-center orbits of electrons in a modeled flare. An initially isotropic distribution of particles is seeded in a contracting island from the simulated eruption, and the subsequent evolution of these particles is followed using guiding-center theory. We find that the distribution function becomes increasingly anisotropic over time as the electrons’ energy increases by up to a factor of five, in general agreement with the previous study. In addition, we show that the energized particles are concentrated on the Sunward side of the island, adjacent to the reconnection X-point in the flare current sheet. Furthermore, our analysis demonstrates that the electron energy gain is dominated by betatron acceleration in the compressed, strengthened magnetic field of the contracting island. Fermi acceleration by the shortened field lines of the island also contributes to the energy gain, but it is less effective than the betatron process.

  6. What is the Magnetic Moment of the Electron?

    Science.gov (United States)

    Steinmann, Othmar

    Because of infrared effects the charged sectors of QED contain no eigenstates of the mass operator. The electron is therefore not definable as a Wigner particle. There exists no sharp, unambiguous, definition of the notion of a 1-electron state. The assignment of a fixed value of the magnetic moment - or similar quantities - to the electron is therefore at first problematic. It is not clear a priori that such a notion is meaningful. Conventionally this problem is solved by first calculating the desired quantity in an IR-regularized theory and then removing the regularization. If this method yields a finite value, that is considered sufficient proof of its soundness. This is clearly less than satisfactory. Here we propose a more convincing way of defining the intrinsic magnetic moment of the electron, which does not use any regularizations and is not based on an interaction with external fields. A pseudostatic 1-electron state is defined in a phenomenological way. Its magnetic moment, as defined here, does not depend on the unavoidable ambiguities inherent in this definition. The method leads to the same analytic expression as the conventional approach, thus preserving the excellent agreement between theory and experiment.

  7. Observations of slow electron holes at a magnetic reconnection site.

    Science.gov (United States)

    Khotyaintsev, Yu V; Vaivads, A; André, M; Fujimoto, M; Retinò, A; Owen, C J

    2010-10-15

    We report in situ observations of high-frequency electrostatic waves in the vicinity of a reconnection site in the Earth's magnetotail. Two different types of waves are observed inside an ion-scale magnetic flux rope embedded in a reconnecting current sheet. Electron holes (weak double layers) produced by the Buneman instability are observed in the density minimum in the center of the flux rope. Higher frequency broadband electrostatic waves with frequencies extending up to f(pe) are driven by the electron beam and are observed in the denser part of the rope. Our observations demonstrate multiscale coupling during the reconnection: Electron-scale physics is induced by the dynamics of an ion-scale flux rope embedded in a yet larger-scale magnetic reconnection process.

  8. Nonlinear electron acoustic waves in presence of shear magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata 700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

    2013-12-15

    Nonlinear electron acoustic waves are studied in a quasineutral plasma in the presence of a variable magnetic field. The fluid model is used to describe the dynamics of two temperature electron species in a stationary positively charged ion background. Linear analysis of the governing equations manifests dispersion relation of electron magneto sonic wave. Whereas, nonlinear wave dynamics is being investigated by introducing Lagrangian variable method in long wavelength limit. It is shown from finite amplitude analysis that the nonlinear wave characteristics are well depicted by KdV equation. The wave dispersion arising in quasineutral plasma is induced by transverse magnetic field component. The results are discussed in the context of plasma of Earth's magnetosphere.

  9. Effects of electron inertia in collisionless magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Andrés, Nahuel, E-mail: nandres@iafe.uba.ar; Gómez, Daniel [Instituto de Astronomía y Física del Espacio, CC. 67, suc. 28, 1428, Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Univrsidad de Buenos Aires, Pabellón I, 1428, Buenos Aires (Argentina); Martin, Luis; Dmitruk, Pablo [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Univrsidad de Buenos Aires, Pabellón I, 1428, Buenos Aires (Argentina)

    2014-07-15

    We present a study of collisionless magnetic reconnection within the framework of full two-fluid MHD for a completely ionized hydrogen plasma, retaining the effects of the Hall current, electron pressure and electron inertia. We performed 2.5D simulations using a pseudo-spectral code with no dissipative effects. We check that the ideal invariants of the problem are conserved down to round-off errors. Our numerical results confirm that the change in the topology of the magnetic field lines is exclusively due to the presence of electron inertia. The computed reconnection rates remain a fair fraction of the Alfvén velocity, which therefore qualifies as fast reconnection.

  10. Magnetically insulated electron flows in pulsed power systems

    Science.gov (United States)

    Lawconnell, Robert I.

    1989-08-01

    Magnetic insulation is crucial in the operation of large pulsed power systems. Particular attention will be paid to describing magnetic insulation in realistic pulsed power systems. A theoretical model is developed that allows the production of self consistent magnetically insulated laminar flows in perturbed cylindrical systems given only the electron density profile. The theory is checked and justified by detailed comparisons with results from a 2-dimensional electromagnetic code, MASK. The procedure followed in the theoretical development is to use the relativistic Vlasov equation, Ampere's law and Gauss' law, to obtain a relation between the density profile and the velocity profile for insulated flows. Given the density profile and the corresponding derived velocity profile, a self consistent flow solution is obtained by means of Maxwell's equations. It is checked by taking a special case (corresponding to no perturbations) which results in the well known Brillouin flow theory. Emphasis is placed on determining the magnetic insulation threshold of a pulsed power system employing a plasma erosion opening switch. The procedure employed in the computational study is to vary critical aspects of the pulsed power system and then note whether magnetic insulation breaks down. The point at which magnetic insulation breaks down (as a function of geometry, load impedance, and applied voltage) is the magnetic insulation threshold for the system.

  11. Tunable electronic and magnetic properties in stanene by 3d transition metal atoms absorption

    Science.gov (United States)

    Xing, Dan-Xu; Ren, Ceng-Ceng; Zhang, Shu-Feng; Feng, Yong; Chen, Xin-Lian; Zhang, Chang-Wen; Wang, Pei-Ji

    2017-03-01

    The electronic and magnetic properties of transition metal (TM) atoms (V, Cr, Mn, Fe, Co, Ni) adsorption on stanene are investigated by first-principles calculations. The results indicate that the TM atoms prefer to be relaxed on a H site on stanene except V atom which lies on the valley site. Fe-absorbed stanene is a spin gapless semiconductor with up-spin electron and down-spin hole carriers allowing the coexistence of charge current and the pure spin current. Co-absorbed stanene lies in the half metal phase. The V-, Cr-, Mn-, and Cu-absorbed stanene turn the stanene into metal, while Ni- and Zn-absorbed stanene open a narrow band gap. For V-, Cr-, Mn-, Fe-, and Co-absorbed stanene, the magnetic moment of the TM will survive while the Ni-, Cu-, and Zn-absorbed stanene will be non-magnetic material. These findings may have great potential in the design of new electrically controllable spintronic devices.

  12. Structure and magnetic properties of Fe doped In{sub 2}O{sub 3} thin films prepared by electron beam evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Krishna, N. Sai; Kaleemulla, S., E-mail: skaleemulla@gmail.com; Rao, N. Madhusudhana; Krishnamoorthi, C.; Begam, M. Rigana [Thin Films Laboratory, School of Advanced Sciences, VIT University, Vellore – 632014 (India); Amarendra, G. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam – 603102 (India); UGC-DAE-CSR, Kalpakkam Node, Kokilamedu, Tamilnadu -603104 (India)

    2015-06-24

    Pure and Fe (7 at.%) doped In{sub 2}O{sub 3} thin films were grown onto the glass substrates by electron beam evaporation technique. The structural and magnetic properties of the pure and Fe doped In{sub 2}O{sub 3} thin films have been studied. The undoped and Fe doped In{sub 2}O{sub 3} thin films shown ferromagnetic property at room temperature. A magnetization of 24 emu/cm{sup 3} was observed for pure In{sub 2}O{sub 3} thin films. The magnetization of 38.23 emu/cm{sup 3} was observed for the Fe (7 at.%) doped In{sub 2}O{sub 3} thin films.

  13. Role of 4 f electrons in crystallographic and magnetic complexity

    Science.gov (United States)

    Pathak, Arjun K.; Paudyal, Durga; Mudryk, Yaroslav; Pecharsky, Vitalij K.

    2017-08-01

    The functionality of many magnetic materials critically depends on first manipulating and then taking advantage of highly nonlinear changes of properties that occur during phase transformations. Unique to lanthanides, property-defining 4 f electrons are highly localized and, as commonly accepted, play little to no role in chemical bonding. Yet here we demonstrate that the competition between 4 f -electron energy landscapes of Dy (4 f9 ) and Er (4 f11 ) is the key element of the puzzle required to explain complex interplay of magnetic and structural features observed in E r1 -xD yxC o2 , and likely many other mixed lanthanide systems. Unlike the parent binaries—DyC o2 and ErC o2 —E r1 -xD yxC o2 exhibits two successive magnetostructural transitions: a first order at TC, followed by a second order in the ferrimagnetically ordered state. Supported by first-principles calculations, our results offer new opportunities for targeted design of magnetic materials with multiple functionalities, and also provide a critical insight into the role of 4 f electrons in controlling the magnetism and structure of lanthanide intermetallics.

  14. Ultrafast electron transport in graphene and magnetic nanostructures

    Science.gov (United States)

    Turchinovich, Dmitry

    2016-03-01

    Ultrafast terahertz spectroscopy is an ideal tool for observation of dynamics of charge, lattice and spin in solids on the most elementary timescale: in the regime ωτ ~ 1, where ω is the electromagnetic wave oscillation frequency, and τ is the characteristic timescale at which the fundamental phenomena in the three subsystems comprising the solid occur. In this paper two case studies will be discussed. (i) Ultrafast electron transport in graphene. We will show, that the free-carrier conductivity of graphene in arbitrary ultrafast, (sub-)picosecond electric fields is defined by the thermodynamic balance maintained within the electronic structure of graphene acting as thermalized electron gas. Within this simple thermodynamic picture, the electron gas quasi-instantaneously increases its temperature by absorbing the energy of driving ultrafast electric field, and at the same time cools down via a time-retarded, few picosecond-long process of phonon emission. The asymmetry in electron heating and cooling dynamics leads to heat accumulation in the electron population of graphene, concomitantly lowering the chemical potential for hotter electrons, and thereby reducing the intraband conductivity of graphene - an effect crucially important for understanding of ultrafast graphene transistors and photodetectors. (ii) We will also discuss the fundamental observation of spin-controlled electron conduction of Fermilevel electrons in ferromagnetic metals, and will directly quantify the Mott picture of conduction in ferromagnets - the effect directly employed in modern magnetic sensor technologies such as giant magnetoresistance.

  15. Electron-positron pair production by an electron in a magnetic field in the resonant case

    CERN Document Server

    Novak, O P

    2012-01-01

    Resonant e+e- pair production by an electron in a magnetic field near the process threshold has been analytically studied. Using the Nikishov's theorem an estimation of the number of events has been made in the magnetic field equivalent to laser wave in the SLAC experiment [D.Burke et.al. Phys. Rev. Lett.79, 1626 (1997)]. The obtained estimation is in reasonable agreement with the experimental data.

  16. Electron Paramagnetic Studies Of Diluted Magnetic Semiconductor Nanostructures

    CERN Document Server

    Montes, L A

    1999-01-01

    In this thesis we investigate the Electron Paramagnetic Resonance (EPR) of Diluted Magnetic Semiconductor (DMS) nanostructures. The first chapter studies the appearance of strain-induced magnetic dipole forbidden transitions in the EPR spectrum of highly mismatched DMS superlattices grown by Molecular Beam Epitaxy (MBE). We investigated ZnTe/MnTe, ZnTe/CdTe:Mn and CdTe/ZnTe:Mn superlattices where the lattice mismatch between layers reaches values as large as 6%. We report the appearance of forbidden transitions even at orientations where strain should not produce any mixing, and interpret them as the onset of three dimensional growth of Quantum Dots (QD)...

  17. New Electron Cloud Detectors for the PS Main Magnets

    CERN Document Server

    Yin Vallgren, Ch; Gilardoni, S; Taborelli, M; Neupert, H; Ferreira Somoza, J

    2014-01-01

    Electron cloud (EC) has already been observed during normal operation of the PS, therefore it is necessary to study its in fluence on any beam instability for the future LHC Injector Upgrade (LIU). Two new electron cloud detectors have been discussed, developed and installed during the Long Shutdown (LS1) in one of the PS main magnets. The first measurement method is based on current measurement by using a shielded button-type pick-up. Due to the geometry and space limitation in the PS magnet, the button-type pick-up made of a 96%Al2O3 block coated with a thin layer of solvent-based Ag painting, placed 30 degrees to the bottom part of the vacuum chamber was installed in the horizontal direction where the only opening of the magnet coil is. The other newly developed measurement method is based on detection of photons emitted by the electrons from the electron cloud impinging on the vacuum chamber walls. The emitted photons are reected to a quartz window. A MCP-PMT (Micro-Channel Plate Photomultiplier Tube) wit...

  18. Particle Acceleration in Relativistic Magnetized Collisionless Electron-Ion Shocks

    CERN Document Server

    Sironi, Lorenzo

    2010-01-01

    We investigate shock structure and particle acceleration in relativistic magnetized collisionless electron-ion shocks by means of 2.5D particle-in-cell simulations with ion-to-electron mass ratios (m_i/m_e) ranging from 16 to 1000. We explore a range of inclination angles between the pre-shock magnetic field and the shock normal. In "subluminal" shocks, where relativistic particles can escape ahead of the shock along the magnetic field lines, ions are efficiently accelerated via a Fermi-like mechanism. The downstream ion spectrum consists of a relativistic Maxwellian and a high-energy power-law tail, which contains ~5% of ions and ~30% of ion energy. Its slope is -2.1. Upstream electrons enter the shock with lower energy than ions, so they are more strongly tied to the field. As a result, only ~1% of the incoming electrons are Fermi-accelerated at the shock before being advected downstream, where they populate a steep power-law tail (with slope -3.5). For "superluminal" shocks, where relativistic particles ca...

  19. Localized Electron Heating by Strong Guide-Field Magnetic Reconnection

    Science.gov (United States)

    Guo, Xuehan; Sugawara, Takumichi; Inomoto, Michiaki; Yamasaki, Kotaro; Ono, Yasushi; UTST Team

    2015-11-01

    Localized electron heating of magnetic reconnection was studied under strong guide-field (typically Bt 15Bp) using two merging spherical tokamak plasmas in Univ. Tokyo Spherical Tokamak (UTST) experiment. Our new slide-type two-dimensional Thomson scattering system documented for the first time the electron heating localized around the X-point. The region of high electron temperature, which is perpendicular to the magnetic field, was found to have a round shape with radius of 2 [cm]. Also, it was localized around the X-point and does not agree with that of energy dissipation term Et .jt . When we include a guide-field effect term Bt / (Bp + αBt) for Et .jt where α =√{ (vin2 +vout2) /v∥2 } , the energy dissipation area becomes localized around the X-point, suggesting that the electrons are accelerated by the reconnection electric field parallel to the magnetic field and thermalized around the X-point. This work was supported by JSPS A3 Foresight Program ``Innovative Tokamak Plasma Startup and Current Drive in Spherical Torus,'' a Grant-in-Aid from the Japan Society for the Promotion of Science (JSPS) Fellows 15J03758.

  20. Permanent magnet electron beam ion source/trap systems with bakeable magnets for improved operation conditions.

    Science.gov (United States)

    Schmidt, M; Zschornack, G; Kentsch, U; Ritter, E

    2014-02-01

    The magnetic system of a Dresden electron beam ion source (EBIS) generating the necessary magnetic field with a new type of permanent magnet made of high energy density NdFeB-type material operable at temperatures above 100 °C has been investigated and tested. The employment of such kind of magnets provides simplified operation without the time-consuming installation and de-installation procedures of the magnets for the necessary baking of the ion source after commissioning and maintenance work. Furthermore, with the use of a new magnetization technique the geometrical filling factor of the magnetic Dresden EBIS design could be increased to a filling factor of 100% leading to an axial magnetic field strength of approximately 0.5 T exceeding the old design by 20%. Simulations using the finite element method software Field Precision and their results compared with measurements are presented as well. It could be shown that several baking cycles at temperatures higher than 100 °C did not change the magnetic properties of the setup.

  1. Electronic and magnetic properties of DUT-8(Ni).

    Science.gov (United States)

    Trepte, Kai; Schwalbe, Sebastian; Seifert, Gotthard

    2015-07-14

    First principles calculations using density functional theory (DFT) have been performed to investigate the electronic and magnetic properties of DUT-8(Ni) (DUT - Dresden University of Technology). This flexible metal-organic framework (MOF) exists in two crystalline forms: DUT-8(Ni)open and DUT-8(Ni)closed. To identify the energetically favoured magnetic ordering, the density of states (DOS) and the energy difference between a low-spin (LS) and a high-spin (HS) coupling ΔELS-HS for those crystalline structures have been computed. Calculations on supercells have been carried out to include a variety of different magnetic couplings beyond a single unit cell. Several molecular model systems have been employed to further investigate the magnetic behaviour by introducing a diversity of chemical environments to the magnetic centers. The magnetic ground state of both crystalline structures has been found to be the low-spin state (S = 0). This low-spin ordering can be seen in the DOS as well as from ΔELS-HS calculations. Additionally, the calculations on the supercells confirm that the local character of the ordering (i.e. within the Ni dimers) is the most favoured one. However, the model systems indicate a change from the low-spin (S = 0) to a high-spin (S ≠ 0) ordering by introducing certain alterations into the chemical environment. Such alterations could be incorporated into the crystalline systems which should lead to similar results.

  2. On the magnetic properties of iron nanostructures fabricated via focused electron beam induced deposition and autocatalytic growth processes

    Science.gov (United States)

    Tu, F.; Drost, M.; Vollnhals, F.; Späth, A.; Carrasco, E.; Fink, R. H.; Marbach, H.

    2016-09-01

    We employ Electron beam induced deposition (EBID) in combination with autocatalytic growth (AG) processes to fabricate magnetic nanostructures with controllable shapes and thicknesses. Following this route, different Fe deposits were prepared on silicon nitride membranes under ultra-high vacuum conditions and studied by scanning electron microscopy (SEM) and scanning transmission x-ray microspectroscopy (STXM). The originally deposited Fe nanostructures are composed of pure iron, especially when fabricated via autocatalytic growth processes. Quantitative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy was employed to derive information on the thickness dependent composition. X-ray magnetic circular dichroism (XMCD) in STXM was used to derive the magnetic properties of the EBID prepared structures. STXM and XMCD analysis evinces the existence of a thin iron oxide layer at the deposit-vacuum interface, which is formed during exposure to ambient conditions. We were able to extract magnetic hysteresis loops for individual deposits from XMCD micrographs with varying external magnetic field. Within the investigated thickness range (2-16 nm), the magnetic coercivity, as evaluated from the width of the hysteresis loops, increases with deposit thickness and reaches a maximum value of ˜160 Oe at around 10 nm. In summary, we present a viable technique to fabricate ferromagnetic nanostructures in a controllable way and gain detailed insight into their chemical and magnetic properties.

  3. Electron dynamics in collisionless magnetic reconnection with a PIC simulation

    Institute of Scientific and Technical Information of China (English)

    GUO Jun

    2009-01-01

    Two-dimensional particle-in-cell (PIC) simulation is used to investigate electron dynamics in colli-sionless magnetic reconnection, and the proton/electron mass ratio is taken to be ml/me = 256. The results show that the presence of a strong initial guide field will change the direction of the electron flow. The electron density cavities and the parallel electric field can be found in the electron inflow re-gion along the separatrix, and the electron inflow and density cavities only appear in the second and fourth quadrants. What is different from the results with a smaller mass ratio is that new structures appear in the diffusion region near the X line: (1) Narrow regions of density enhancement and density cavities can be found synchronously in this region; and (2) corresponding to the electron density changes near the X line, the strong parallel electric fields are found to occur in the first and third quadrants. These electric fields perhaps play a more important role in acceleration and heating elec-trons than those fields located in the density cavities.

  4. The Mechanisms of Electron Heating and Acceleration during Magnetic Reconnection

    CERN Document Server

    Dahlin, J T; Swisdak, M

    2014-01-01

    The heating of electrons in collisionless magnetic reconnection is explored in particle-in-cell (PIC) simulations with non-zero guide fields so that electrons remain magnetized. In this regime electric fields parallel to B accelerate particles directly while those perpendicular to B do so through gradient-B and curvature drifts. The curvature drift drives parallel heating through Fermi reflection while the gradient B drift changes the perpendicular energy through betatron acceleration. We present simulations in which we evaluate each of these mechanisms in space and time in order to quantify their role in electron heating. For a case with a small guide field (20 % of the magnitude of the reconnecting component) the curvature drift is the dominant source of electron heating. However, for a larger guide field (equal to the magnitude of the reconnecting component) electron acceleration by the curvature drift is comparable to that of the parallel electric field. In both cases the heating by the gradient B drift i...

  5. Trembling motion of relativistic electrons in a magnetic field

    CERN Document Server

    Rusin, Tomasz M

    2010-01-01

    One-electron 3+1 and 2+1 Dirac equations are used to calculate the motion of a relativistic electron in a vacuum in the presence of an external magnetic field. First, calculations are carried on an operator level and exact analytical results are obtained for the electron trajectories which contain both intraband frequency components, identified as the cyclotron motion, as well as interband frequency components, identified as the trembling motion (Zitterbewegung, ZB). Next, time-dependent Heisenberg operators are used for the same problem to compute average values of electron position and velocity employing Gaussian wave packets. It is shown that the presence of a magnetic field and the resulting quantization of the energy spectrum has pronounced effects on the electron Zitterbewegung: it introduces intraband frequency components into the motion, influences all the frequencies and makes the motion stationary (not decaying in time) in case of the 2+1 Dirac equation. Finally, simulations of the 2+1 Dirac equatio...

  6. Electron self-reinforcing process of magnetic reconnection.

    Science.gov (United States)

    Wan, Weigang; Lapenta, Giovanni

    2008-07-04

    The growth of collisionless magnetic reconnection is discovered to be a nonlinear electron self-reinforcing process. Accelerated by the reconnection electric field, the small portion of energetic electrons in the vicinity of the X point are found to be the cause of the fast reconnection rate. This new mechanism explains that recent simulation results of different reconnection evolutions (i.e., steady state, quasisteady state, or nonsteady state) are essentially determined by the availability of feeding plasma inflows. Simulations are carried out with open boundary conditions.

  7. Formation of Ferric Porphyrinoids with Unusual Electronic and Magnetic Properties

    Institute of Scientific and Technical Information of China (English)

    M.Nakamura; Y.Ohgo; A.Ikezaki

    2007-01-01

    1 Results Energy levels of the metal 3d orbitals in iron(Ⅲ) porphyrinoids are controlled by various factors such as the nature and number of axial ligands, electronic and steric effects of peripheral substituents, deformation and core modification of porphyrin ring, hydrogen bonding to the axial ligand, etc. By manipulating these factors, we are now able to prepare various iron(Ⅲ) porphyrinoids withunusual electronic and magnetic properties[1]. Here, we report the formation of such complexes as ⅰ) low-s...

  8. Intrinsic magnetic refrigeration of a single electron transistor

    Energy Technology Data Exchange (ETDEWEB)

    Ciccarelli, C.; Ferguson, A. J. [Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom); Campion, R. P.; Gallagher, B. L. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom)

    2016-02-01

    In this work, we show that aluminium doped with low concentrations of magnetic impurities can be used to fabricate quantum devices with intrinsic cooling capabilities. We fabricate single electron transistors made of aluminium doped with 2% Mn by using a standard multi angle evaporation technique and show that the quantity of metal used to fabricate the devices generates enough cooling power to achieve a drop of 160 mK in the electron temperature at the base temperature of our cryostat (300 mK). The cooling mechanism is based on the magneto-caloric effect from the diluted Mn moments.

  9. Electronic structure and magnetic anisotropy of CrO2

    Science.gov (United States)

    Toropova, A.; Kotliar, G.; Savrasov, S. Y.; Oudovenko, V. S.

    2005-05-01

    The problem of importance of strong correlations for the electronic structure, transport, and magnetic properties of half-metallic ferromagnetic CrO2 is addressed by performing density functional electronic structure calculations in the local spin density approximation (LSDA) as well as using the LSDA+U method. It is shown that the corresponding low-temperature experimental data are best fitted without accounting for the Hubbard U corrections. We conclude that the ordered phase of CrO2 is weakly correlated.

  10. Electronic and Magnetic Properties of the p-NPNN

    Institute of Scientific and Technical Information of China (English)

    LUOShi-Jun; YAOKai-Lun

    2003-01-01

    In this paper, we study the electronic band structure and the ferromagnetic properties of the organic radical p-NPNN by employing density-functional theory with generalized gradient approximation (GGA ) and local-spin density approximation (LSDA). The density of states, the total energy, and the spin magnetic moment are calculated. The calculations reveal that the δ-phase of p-NPNN has a stable ferromagnetic ground state. It is found that an unpaired electron in this compound is localized in a single occupied molecular orbital (SOMO) constituted primarily of π* (NO) orbitals, and the main contribution of the spin magnetic moment comes from the π* (NO) orbitals. By comparison, we find that the GGA is more suitable to describe free radical systems than LSDA.

  11. Magnetic alteration of entanglement in two-electron quantum dots

    CERN Document Server

    Simonovic, N S

    2015-01-01

    Quantum entanglement is analyzed thoroughly in the case of the ground and lowest states of two-electron axially symmetric quantum dots under a perpendicular magnetic field. The individual-particle and the center-of-mass representations are used to study the entanglement variation at the transition from interacting to noninteracting particle regimes. The mechanism of symmetry breaking due to the interaction, that results in the states with symmetries related to the later representation only, being entangled even at the vanishing interaction, is discussed. The analytical expression for the entanglement measure based on the linear entropy is derived in the limit of noninteracting electrons. It reproduces remarkably well the numerical results for the lowest states with the magnetic quantum number M>2 in the interacting regime. It is found that the entanglement of the ground state is a discontinuous function of the field strength. A method to estimate the entanglement of the ground state, characterized by the quan...

  12. Electron thermal self-energy in a magnetic field

    CERN Document Server

    Persson, D

    1995-01-01

    Using the general form of the static energy solutions to the Dirac equation with a magnetic field, we calculate a general self-energy matrix in the Furry-picture. In the limit of high temperatures, but even higher magnetic fields, a self-consistent dispersion relation is solved. In contrast to the high temperature limit, this merely results in a small mass shift. The electron anomalous magnetic moment is calculated. The contribution from thermal fermions is found to be different from the corresponding contribution using perturbation theory and plane-wave external states. In the low temperature limit the self-energy is shown to exhibit de Haas--van Alphen oscillations. In the limit of low temperatures and high densities, the self-energy becomes very large.

  13. Influence of Magnetic Field Decay on Electron Capture in Magnetars

    Indian Academy of Sciences (India)

    Jie Zhang

    2014-09-01

    The de-excited energy of electron capture (EC) induced by magnetic field decay may be a new source for heating magnetar crust, so we do a quantitative calculation on EC process near the outer crust and analyse their influence on persistent X-ray radiation of magnetars, adopting the experimental data or the results of theoretical model (including the large-scale shell model and quasi-particle random phase approximation).

  14. A permanent magnet electron beam phase-shifter

    Energy Technology Data Exchange (ETDEWEB)

    Novikov, G.A. E-mail: trower@naxs.net; Ermakov, A.N.; Pakhomov, N.I.; Semyachkin, V.K.; Shvedunov, V.I.; Skachkov, V.S.; Tyurin, S.A

    2004-05-21

    We describe here the design and construction of a permanent magnet-based electron beam phase-shifter now operating in our 70 MeV Race-Track Microtron (P. Lucas, S. Webber (Eds.), Proceedings of the 2001 Particle Accelerator Conference, Vol. 4, IEEE, Piscataway, NJ, 2001, p. 2596; L. Gennary (Ed.), Proceedings of the 1995 Particle Accelerator Conference, Vol. 2, IEEE, Piscataway, NJ, 1996, p. 807)

  15. Effects of Ion-to-Electron Mass Ratio on Electron Dynamics in Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    GUO Jun; LU Quan-Ming

    2007-01-01

    A 21/2-dimensional electromagnetic particle-in-cell (PIC) simulation code is used to investigate electron behaviour in collisionless magnetic reconnection. The results show that the ion/electron mass ratio (mi/me) almost has no impact on the reconnection rate, however it can significantly affect electron behaviour in the diffusion region. For the case with larger mass ratio, the width of electron current sheet becomes smaller and the outflow region along the separatrix is smaller, hence the peak of the electron outflow speed is essentially larger. Density cavities and the parallel electric field E// along the separatrix can be found in the case with larger mass ratio, which may have significant influences on the acceleration and heating of the electrons near the X point.

  16. Holographic description of strongly correlated electrons in external magnetic fields

    CERN Document Server

    Gubankova, E; Cubrovic, M; Schalm, K; Schijven, P; Zaanen, J

    2013-01-01

    We study the Fermi level structure of (2+1)-dimensional strongly interacting electron systems in external magnetic field using the AdS/CFT correspondence. The gravity dual of a finite density fermion system is a Dirac field in the background of the dyonic AdS-Reissner-Nordstrom black hole. In the probe limit the magnetic system can be reduced to the non-magnetic one, with Landau-quantized momenta and rescaled thermodynamical variables. We find that at strong enough magnetic fields, the Fermi surface vanishes and the quasiparticle is lost either through a crossover to conformal regime or through a phase transition to an unstable Fermi surface. In the latter case, the vanishing Fermi velocity at the critical magnetic field triggers the non-Fermi liquid regime with unstable quasiparticles and a change in transport properties of the system. We associate it with a metal-"strange metal" phase transition. We compute the DC Hall and longitudinal conductivities using the gravity-dressed fermion propagators. As expecte...

  17. Electronic and Magnetic Structure of Octahedral Molecular Sieves

    Science.gov (United States)

    Morey-Oppenheim, Aimee M.

    The major part of this research consists of magnetic and electronic studies of metal doped cryptomelane-type manganese oxide octahedral molecular sieves (KOMS-2). The second part of this study involves the magnetic characterization of cobalt doped MCM-41 before and after use in the synthesis of single walled carbon nanotubes. Manganese oxides have been used widely as bulk materials in catalysis, chemical sensors, and batteries due to the wide range of possible stable oxidation states. The catalytic function of manganese oxides is further tuned by doping the material with numerous transition metals. It is of particular interest the oxidation states of Mn present after doping. New titrations to determine the oxidation state of Mn were investigated. To further examine the structure of KOMS-2, the magnetic contribution of dopant metals was also examined. The KOMS-2 structure having both diamagnetic and paramagnetic metal ions substitutions was studied. MCM-41 with the incorporation of cobalt into the structure was analyzed for its magnetic properties. The material undergoes significant structural change during the synthesis of single walled carbon nanotubes. It was the focus of this portion of the research to do a complete magnetic profile of both the before and after reaction material.

  18. "Spectral implementation" for creating a labeled pseudo-pure state and the Bernstein-Vazirani algorithm in a four-qubit nuclear magnetic resonance quantum processor.

    Science.gov (United States)

    Peng, Xinhua; Zhu, Xiwen; Fang, Ximing; Feng, Mang; Liu, Maili; Gao, Kelin

    2004-02-22

    A quantum circuit is introduced to describe the preparation of a labeled pseudo-pure state by multiplet-component excitation scheme which has been experimentally implemented on a 4-qubit nuclear magnetic resonance quantum processor. Meanwhile, we theoretically analyze and numerically investigate the low-power selective single-pulse implementation of a controlled-rotation gate, which manifests its validity in our experiment. Based on the labeled pseudo-pure state prepared, a 3-qubit Bernstein-Vazirani algorithm has been experimentally demonstrated by spectral implementation. The "answers" of the computations are identified from the split peak positions in the spectra of the observer spin, which are equivalent to projective measurements required by the algorithms.

  19. Cavity Control of a Single-Electron Quantum Cyclotron:\\\\Measuring the Electron Magnetic Moment

    CERN Document Server

    Hanneke, D; Gabrielse, G

    2010-01-01

    Measurements with a one-electron quantum cyclotron determine the electron magnetic moment, given by $g/2 = 1.001\\,159\\,652\\,180\\,73\\,(28)\\,[0.28~\\textrm{ppt}]$, and the fine structure constant, $\\alpha^{-1}=137.035\\,999\\,084\\,(51)\\,[0.37~\\textrm{ppb}]$. Brief announcements of these measurements are supplemented here with a more complete description of the one-electron quantum cyclotron and the new measurement methods, a discussion of the cavity control of the radiation field, a summary of the analysis of the measurements, and a fuller discussion of the uncertainties.

  20. Universal logarithmic temperature dependence of magnetic susceptibility of one-dimensional electrons at critical values of magnetic field

    OpenAIRE

    Vekua, Temo

    2014-01-01

    We study the leading low temperature dependence of magnetic susceptibility of one-dimensional electrons with fixed total number of particles at the magnetic fields equal to zero temperature critical values where magnetic field induces commensurate-incommensurate quantum phase transitions. For free and repulsively interacting electrons there is only one such critical field corresponding to the transition to the fully polarized state. For attractively interacting electrons besides saturation fi...

  1. Coherent states of an electron in a homogeneous constant magnetic field and the zero magnetic field limit

    Energy Technology Data Exchange (ETDEWEB)

    Varro, S.

    1984-06-01

    Coherent states of an electron embedded in a constant homogeneous magnetic field are constructed. The centres of the probability distributions belonging to these states gyrate along possible classical trajectories. Suitable packets of such coherent states are defined which reduce to properly normalised free electronic states in the zero magnetic field limit. A simple example is given to illustrate the dynamics of free electron localisation due to the presence of a magnetic field.

  2. Ab initio study of the structural, magnetic, and electronic properties of copper and silver clusters and their alloys with one palladium atom

    Directory of Open Access Journals (Sweden)

    S. J Hashemifar

    2015-01-01

    Full Text Available In this paper, the structural, magnetic, and electronic properties of two- to nine-atom copper and silver clusters and their alloys with one palladium atom are investigated by using full-potential all-electron density functional computations. After calculating minimized energy of several structural isomers of every nanocluster, it is argued that the small size nanoclusters (up to size of 6, ‎ prefer planar structures, while by increasing size a 2D-3D structural transformation is observed. The structural transformation of pure and copper-palladium clusters occurs in the size of seven and that of silver-palladium cluster in happens at the size of six. The calculated second difference and dissociation energies confirm that the two- and eight- atom pure clusters and three- and seven- atom alloyed clusters are magic clusters. The electronic and magnetic properties of stable isomers are calculated and considered after applying many body based GW correction.

  3. Highly Accurate Measurement of the Electron Orbital Magnetic Moment

    CERN Document Server

    Awobode, A M

    2015-01-01

    We propose to accurately determine the orbital magnetic moment of the electron by measuring, in a Magneto-Optical or Ion trap, the ratio of the Lande g-factors in two atomic states. From the measurement of (gJ1/gJ2), the quantity A, which depends on the corrections to the electron g-factors can be extracted, if the states are LS coupled. Given that highly accurate values of the correction to the spin g-factor are currently available, accurate values of the correction to the orbital g-factor may also be determined. At present, (-1.8 +/- 0.4) x 10-4 has been determined as a correction to the electron orbital g-factor, by using earlier measurements of the ratio gJ1/gJ2, made on the Indium 2P1/2 and 2P3/2 states.

  4. Electron Transport Behavior in a Mirror Magnetic Field and a Non-uniform Electric Field

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Hong; LIU Zu-Li; YAO Kai-Lun; WEI He-Lin; LIU Hong-Xiang

    2001-01-01

    The behaviors of electrons as they move under the influence of mirror magnetic field and non-uniform electric field in a positive column of helium radio frequency gas discharge are studied by Monte Carlo simulation. Some types of collisions (elastic, excitation and ionization collisions) are considered. Graphs showing how the electron density,electron energy, electron current density, collision rate and the electron-scattering angular distribution are affected by the mirror magnetic field are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column. In the presence of the mirror magnetic field, the electrons are restricted in the middle part of the positive column, and the electron density is greatly increased. The electron collision rate and the electron current density are enhanced in the middle region, and the electron-scattering angles are extended by the mirror magnetic tields. These results are in good agreement with experimental results.

  5. Interplay between electronic transport and magnetic order in ferromagnetic magnetic manganite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Hundley, M.F.; Neumeier, J.J.; Heffner, R.H.; Jia, Q.X.; Wu, X.D.; Thompson, J.D.

    1997-05-01

    The transition metal oxides La{sub 1{minus}x}A{sub x}MnO{sub 3} (A = Ba, Ca, or Sr) order ferromagnetically with Curie temperatures ranging from as low as 50 K to well above room temperature. Magnetic order in these compounds results in a concomitant metal-insulator transition. The feature displayed by the manganites that is most important technologically is the extremely large negative magnetoresistance that achieves its largest values near the magnetic ordering temperature. Qualitatively, this colossal magnetoresistance (CMR) phenomenon involves the suppression of the relatively sharp maximum in the resistivity that is centered at T{sub C}. When considered collectively, the anomalous temperature-dependent transport properties, the CMR effect, and the magnetically ordered ground state indicate that a novel interplay between magnetism and electronic transport occurs in the manganites. General features of the magnetic-field and temperature-dependent electrical resistivity and magnetization as displayed by PLD-grown thin films are examined. Particular emphasis is placed on what these measurements tell us about the conduction process both above and below the magnetic ordering temperature.

  6. Observation of hyperfine mixing in measurements of a magnetic octupole decay in isotopically pure nickel-like 129Xe and 132Xe ions

    Energy Technology Data Exchange (ETDEWEB)

    Trabert, E; Beiersdorfer, P; Brown, G V

    2006-12-21

    We present measurements of high statistical significance of the rate of the magnetic octupole (M3) decay in nickel-like ions of isotopically pure {sup 129}Xe and {sup 132}Xe. On {sup 132}Xe, an isotope with zero nuclear spin and therefore without hyperfine structure, the lifetime of the metastable level was established as (15.06 {+-} 0.24) ms. On {sup 129}Xe, an additional fast (2.7 {+-} 0.1 ms) decay component was established that represents hyperfine mixing with a level that decays by electric quadrupole (E2) radiation.

  7. On the texture, phase and tensile properties of commercially pure Ti produced via selective laser melting assisted by static magnetic field.

    Science.gov (United States)

    Kang, Nan; Yuan, Hao; Coddet, Pierre; Ren, Zhongming; Bernage, Charles; Liao, Hanlin; Coddet, Christian

    2017-01-01

    Tensile strength and ductility of Selective Laser Melting (SLM) processed commercially pure Ti (CP-Ti) were simultaneous enhanced by preforming the melting/solidification processes under Static Magnetic Field (SMF). The effects of SMF on microstructure and tensile properties were examined. The SMF-SLMed CP-Ti sample presents a microstructure of fine acicular martensitic α'-Ti and lath-shaped α-Ti. Meanwhile, the texture structure of SLMed CP-Ti was eliminated after adding a SMF. The SMF-SLM process offers new avenues to ameliorate the microstructure and improve the mechanical properties of SLMed sample.

  8. Electron turbulence and transport in large magnetic islands

    Science.gov (United States)

    Morton, Lucas

    2016-10-01

    Magnetic islands, observed in both reversed-field pinches (RFPs) and tokamaks, often display unexpected turbulence and transport characteristics. For the first time in an RFP, the high repetition rate Thomson scattering diagnostic on MST has captured a 2D image of the rotating electron temperature structure of a magnetic island in a single discharge. MHD modeling using edge magnetic signals implies a 16 cm wide m,n =1,6 tearing mode island which completely overlaps a 5.5 cm n =7 island (12 cm between island centers). The 3D field is partially chaotic, but still reflective of the n =6 island structure. The measured temperature structure matches the shape and location of the n =6 partially chaotic (or `remnant') island. Contrary to the usual assumption that islands have flat internal temperature, the electron temperature is peaked inside the remnant magnetic island due to ohmic heating. The temperature peaking implies a local effective perpendicular conductivity 10-40 m2/s inside the remnant island. This agrees quantitatively with an effective perpendicular conductivity of 16 m2/s estimated using the magnetic diffusion coefficient (evaluated at the electron mean free path) calculated from the modeled chaotic field. Statistical analysis of measurement ensembles with lower time resolution implies that remnant island heating is common in MST discharges. To investigate the role of turbulence near a magnetic island, the 2D structure of long-wavelength density turbulence has been mapped around a large applied static m,n =2,1 L-mode island in the DIII-D tokamak. The turbulence exhibits intriguing spatial structure. Fluctuations are enhanced several-fold (compared to the no-island case) on the inboard side of the X-point, but not on the outboard side of the X-point and are also reduced near the O-point. This work is supported by the NSF and US DOE under DE-FC02-04ER54698, and DE-FG02-89ER53296.

  9. Effect of a transverse magnetic field on solidification morphology and microstructures of pure Sn and Sn-15 wt% Pb alloys grown by a Czochralski method

    Science.gov (United States)

    Shen, Zhe; Zhong, Yunbo; Wang, Huai; Ren, Weili; Lei, Zuosheng; Ren, Zhongming

    2015-12-01

    The pure Sn and Sn-15 wt% Pb alloys were grown by a Czochralski method under various magnetic flux densities in this paper. The influence of thermoelectric magnetic (TEM) flows and buoyancy flows on solidification morphology, macrosegregation and microstructures had been investigated experimentally, and the velocity magnitude of TEM flows and buoyancy flows had been studied by 3D numerical simulations. The experimental results indicate that the modification of solidification morphology and microstructures is attributed to the unidirectional Pb solutes transport caused by TEM flows. The 3D numerical simulations results show that the buoyancy flows dominate the flows in the melt under a weak transverse magnetic field (B≤0.43 T), and the unidirectional TEM flows at the vicinity of solid-liquid interface become the dominant flows in the melt with the increase of magnetic field. The interaction of TEM flows and buoyancy flows affecting solidification morphology and microstructures during directional solidification of alloys by the Czochralski method under various magnetic flux densities has been discussed and a corresponding simple evolution mechanism of dendritic growth has been proposed.

  10. Screening of Local Magnetic Moment by Electrons of Disordered Graphene

    Institute of Scientific and Technical Information of China (English)

    SHI Li-Peng; XIONG Shi-Jie

    2009-01-01

    Based on the Anderson impurity model and self-consistent approach,we investigate the condition for the screening of a local magnetic moment by electrons in graphene and the influence of the moment on electronic properties of the system.The results of numerical calculations carried out on a finite sheet of graphene show that when the Fermi energy is above the single occupancy energy and below the double occupancy energy of the local impurity,a magnetic state is possible.A phase diagram in a parameter space spanned by the Coulomb energy U and the Fermi energy is obtained to distinguish the parameter regions for the magnetic and nonmagnetic states of the impurity.We find that the combined effect of the impurity and finite size effect results in a large charge density near the edges of the finite graphene sheet.The density of states exhibits a peak at the Dirac point which is caused by the appearance of the edge states localized at the zigzag edges of the sheet.

  11. The Mechanisms of Electron Acceleration During Multiple X Line Magnetic Reconnection with a Guide Field

    CERN Document Server

    Wang, Huanyu; Huang, Can; Wang, Shui

    2016-01-01

    The interactions between magnetic islands are considered to play an important role in electron acceleration during magnetic reconnection. In this paper, two-dimensional (2-D) particle-in-cell (PIC) simulations are performed to study electron acceleration during multiple X line reconnection with a guide field. The electrons remain almost magnetized, and we can then analyze the contributions of the parallel electric field, Fermi and betatron mechanisms to electron acceleration during the evolution of magnetic reconnection by comparing with a guide-center theory. The results show that with the proceeding of magnetic reconnection, two magnetic islands are formed in the simulation domain. The electrons are accelerated by both the parallel electric field in the vicinity of the X lines and Fermi mechanism due to the contraction of the two magnetic islands. Then the two magnetic islands begin to merge into one, and in such a process electrons can be accelerated by the parallel electric field and betatron mechanisms. ...

  12. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    Science.gov (United States)

    Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2015-04-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  13. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    Directory of Open Access Journals (Sweden)

    Jaeyoung Park

    2015-06-01

    Full Text Available We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad’s work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β. This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  14. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Directory of Open Access Journals (Sweden)

    Jia-Jia Zheng

    2016-01-01

    Full Text Available Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn. Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  15. Magnetic and electronic properties of porphyrin-based molecular nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Zhao, Xiang, E-mail: xzhao@mail.xjtu.edu.cn [Institute for Chemical Physics & Department of Chemistry, MOE Key Laboratory for Non-equilibrium Condensed Matter and Quantum Engineering, School of Science, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Wei-Wei [Research Center for Computational Science, Institute for Molecular Science, Okazaki, Aichi 444-8585 (Japan)

    2016-01-15

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  16. Electron transfer mechanism and the locality of the system-bath interaction: a comparison of local, semilocal, and pure dephasing models.

    Science.gov (United States)

    Weiss, Emily A; Katz, Gil; Goldsmith, Randall H; Wasielewski, Michael R; Ratner, Mark A; Kosloff, Ronnie; Nitzan, Abraham

    2006-02-21

    We simulate the effects of two types of dephasing processes, a nonlocal dephasing of system eigenstates and a dephasing of semilocal eigenstates, on the rate and mechanism of electron transfer (eT) through a series of donor-bridge-acceptor systems, D-B(N)-A, where N is the number of identical bridge units. Our analytical and numerical results show that pure dephasing, defined as the perturbation of system eigenstates through the system-bath interaction, does not disrupt coherent eT because it induces no localization; electron transfer may proceed through superexchange in a system undergoing only pure dephasing. A more physically reasonable description may be obtained via a system-bath interaction that reflects the perturbation of more local electronic structure by local nuclear distortions and dipole interactions. The degree of locality of this interaction is guided by the structure of the system Hamiltonian and by the nature of the measurement performed on the system (i.e., the nature of the environment). We compare our result from this "semilocal" model with an even more local phenomenological dephasing model. We calculate electron transfer rate by obtaining nonequilibrium steady-state solutions for the elements of a reduced density matrix; a semigroup formalism is used to write down the dissipative part of the equation of motion.

  17. Magnetic electron focusing and tuning of the electron current with a pn-junction

    Energy Technology Data Exchange (ETDEWEB)

    Milovanović, S. P., E-mail: slavisa.milovanovic@uantwerpen.be; Ramezani Masir, M., E-mail: mrmphys@gmail.com; Peeters, F. M., E-mail: francois.peeters@uantwerpen.be [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

    2014-01-28

    Transverse magnetic focusing properties of graphene using a ballistic four terminal structure are investigated. The electric response is obtained using the semiclassical billiard model. The transmission exhibits pronounced peaks as a consequence of skipping orbits at the edge of the structure. When we add a pn-junction between the two probes, snake states along the pn-interface appear. Injected electrons are guided by the pn-interface to one of the leads depending on the value of the applied magnetic field. Oscillations in the resistance are found depending on the amount of particles that end up in each lead.

  18. Planar electron beams in a wiggler magnet array

    Indian Academy of Sciences (India)

    Arti Hadap; K C Mittal

    2013-02-01

    Transport of high current (∼kA range with particle energy ∼ 1 MeV) planar electron beams is a topic of increasing interest for applications in high-power (1–10 GW) and high-frequency (10–20 GHz) microwave devices such as backward wave oscillator (BWO), klystrons, gyro-BWOs, etc. In this paper, we give a simulated result for transport of electron beams with velocity $V_{b} = 5.23 × 10^{8}$ cm s-1 , relativistic factor = 1.16, and beam voltage = ∼80 kV in notched wiggler magnet array. The calculation includes self-consistent effects of beam-generated fields. Our results show that the notched wiggler configuration with ∼6.97 kG magnetic field strength can provide vertical and horizontal confinements for a sheet electron beam with 0.3 cm thickness and 2 cm width. The feasibility calculation addresses to a system expected to drive for 13–20 GHz BWO with rippled waveguide parameters as width = 3.0 cm, thickness = 1.0 cm, corrugation depth ℎ = 0.225 cm, and spatial periodicity = 1.67 cm.

  19. Electronic structure and magnetism in half-Heusler compounds

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, B R K; Dasgupta, I [Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India)

    2003-11-05

    In this paper we have applied the full-potential linearized muffin tin orbital method and the tight-binding linearized muffin tin orbital method to investigate in detail the electronic structure and magnetism of a series of half-Heusler compounds XMZ with X = Fe,Co,Ni, M = Ti,V,Nb,Zr,Cr,Mo,Mn and Z Sb,Sn. Our detailed analysis of the electronic structure using various indicators of chemical bonding suggests that covalent hybridization of the higher-valent transition element X with the lower-valent transition element M is the key interaction responsible for the formation of the d-d gap in these systems. However, the presence of the sp-valent element is crucial to provide stability to these systems. The influence of the relative ordering of the atoms in the unit cell on the d-d gap is also investigated. We have also studied in detail some of these systems with more than 18 valence electrons which exhibit novel magnetic properties, namely half-metallic ferro- and ferrimagnetism. We show that the d-d gap in the paramagnetic state, the relatively large X-Sb hybridization and the large exchange splitting of the M atoms are responsible for the half-metallic property of some of these systems.

  20. (Fundamental studies of new magnetic heterostructures: Their growth, crystallographic structure, magnetic and electronic properties)

    Energy Technology Data Exchange (ETDEWEB)

    Onellion, M. (Wisconsin Univ., Madison, WI (USA). Dept. of Physics); Dowben, P.A. (Syracuse Univ., NY (USA). Dept. of Physics)

    1990-01-01

    As part of our request for renewal of our grant, we include this progress report on the significant results obtained under grant number FG02-89ER45319, Fundamental Studies of New Magnetic Heterostructures: Their Growth, Crystallographic Structure, Magnetic and Electronic Properties,'' since the inception of the grant. The results include the scientific accomplishments, the instrumentation developed, and the technological applications of our work. Each area is discussed separately and an initial summary of all areas is provided before the detailed discussion.

  1. The expected imprint of flux rope geometry on suprathermal electrons in magnetic clouds

    OpenAIRE

    Owens, Mathew James; Crooker, N. U.; Horbury, T. S.

    2009-01-01

    Magnetic clouds are a subset of interplanetary coronal mass ejections characterized by a smooth rotation in the magnetic field direction, which is interpreted as a signature of a magnetic flux rope. Suprathermal electron observations indicate that one or both ends of a magnetic cloud typically remain connected to the Sun as it moves out through the heliosphere. With distance from the axis of the flux rope, out toward its edge, the magnetic field winds more tightly about the axis and electrons...

  2. Acoustic solitons in magnetized quantum electron-positron plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Mahmood, S; Akhtar, N; Ur-Rehman, H, E-mail: shahzadm100@gmail.com [Theoretical Plasma Physics Division (TPPD), PINSTECH, PO Nilore, Islamabad 44000 (Pakistan)

    2011-03-15

    Nonlinear acoustic wave propagation in dense magnetized electron-positron (e-p) plasmas in the presence of ions is studied. The e-p quantum fluid is taken to be dynamic, while the ions are assumed to be stationary to neutralize the plasma background only. The quantum hydrodynamics model is employed and the reductive perturbation method is used to derive the Zakharov-Kuznetsov equation. Electrostatic potential hump structures are obtained and it is found that an increase in positron concentration decreases the wave amplitude. However, an increase in magnetic field strength reduces the width of the structure significantly. The numerical results are also shown for illustration; the parameters used are taken from the data for the outer layers of white dwarfs.

  3. Frenkel electron on an arbitrary electromagnetic background and magnetic Zitterbewegung

    CERN Document Server

    Deriglazov, Alexei A

    2014-01-01

    We present Lagrangian which implies both necessary constraints and dynamical equations for position and spin of relativistic spin one-half particle. The model is consistent for any value of magnetic moment $\\mu$ and for arbitrary electromagnetic background. Our equations coincide with those of Frenkel in the approximation in which the latter have been obtained by Frenkel. Transition from approximate to exact equations yields two structural modifications of the theory. First, Frenkel condition on spin-tensor turns into the Pirani condition. Second, canonical momentum is no more proportional to velocity. Due to this, even when $\\mu=1$ (Frenkel case), the complete and approximate equations predict different behavior of spinning particle. The difference of momentum from velocity means extra contribution into spin-orbit interaction. To estimate the contribution, we found exact solution to complete equations for the case of uniform magnetic field. While BMT electron moves around the circle, our particle experiences...

  4. Electronic and Magnetic Properties of the p-NPNN

    Institute of Scientific and Technical Information of China (English)

    LUO Shi-Jun; YAO Kai-Lun

    2003-01-01

    In this paper, we study the electronic band structure and the ferromagnetic properties of the organic radicalp-NPNN by employing density-functional theory with generalized gradient approximation (GGA) and local-spin densityapproximation (LSDA). The density of states, the total energy, and the spin magnetic moment are calculated. Thecalculations reveal that the δ-phase of p-NPNN has a stable ferromagnetic ground state. It is found that an unpairedelectron in this compound is localized in a single occupied molecular orbital (SOMO) constituted primarily of π* (NO)orbitals, and the main contribution of the spin magnetic moment comes from the π* (NO) orbitals. By comparison, wefind that the GGA is more suitable to describe free radical systems than LSDA.

  5. Electronic structures of MnB soft magnet

    Directory of Open Access Journals (Sweden)

    Jihoon Park

    2016-05-01

    Full Text Available We have calculated the electronic structure of MnB using first-principles calculations based on the density functional theory within the local-spin-density approximation. The temperature dependence of saturation magnetization [Ms(T] was calculated by mean field approximation. The calculated density of states (DOS shows that the energy region near the Fermi energy (EF is mostly attributed to the d bands of Mn. The saturation magnetizations (Ms of MnB were calculated to be 964.5 emu/cm3 (1.21 T at 0 K and 859.3 emu/cm3 (1.08 T at 300 K. The calculated Ms at 300 K is in good agreement with experimental Ms of 851.5 emu/cm3.

  6. Transport of solar electrons in the turbulent interplanetary magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ablaßmayer, J.; Tautz, R. C., E-mail: robert.c.tautz@gmail.com [Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstraße 36, D-10623 Berlin (Germany); Dresing, N., E-mail: dresing@physik.uni-kiel.de [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, Leibnizstraße 11, D-24118 Kiel (Germany)

    2016-01-15

    The turbulent transport of solar energetic electrons in the interplanetary magnetic field is investigated by means of a test-particle Monte-Carlo simulation. The magnetic fields are modeled as a combination of the Parker field and a turbulent component. In combination with the direct calculation of diffusion coefficients via the mean-square displacements, this approach allows one to analyze the effect of the initial ballistic transport phase. In that sense, the model complements the main other approach in which a transport equation is solved. The major advancement is that, by recording the flux of particles arriving at virtual detectors, intensity and anisotropy-time profiles can be obtained. Observational indications for a longitudinal asymmetry can thus be explained by tracing the diffusive spread of the particle distribution. The approach may be of future help for the systematic interpretation of observations for instance by the solar terrestrial relations observatory (STEREO) and advanced composition explorer (ACE) spacecrafts.

  7. The Stereo Electron Spikes and the Interplanetary Magnetic Field

    Science.gov (United States)

    Jokipii, J. R.; Sheeley, N. R., Jr.; Wang, Y. M.; Giacalone, J.

    2016-12-01

    A recent paper (Klassen etal, 2015) discussed observations of a spike event of 55-65 keV electrons which occurred very nearly simultaneously at STEREO A and STEREO B, which at the time were separated in longitude by 38 degrees. The authors associated the spikes with a flare at the Sun near the footpoint of the nominal Archimedean spiral magnetic field line passing through STEREO A. The spike at STEREO A was delayed by 2.2 minutes from that at STEREOB. We discuss the observations in terms of a model in which the electrons, accelerated at the flare, propagate without significant scattering along magnetic field lines which separate or diverge as a function of radial distance from the Sun. The near simultaneity of the spikes at the two spacecraft is a natural consequence of this model. We interpret the divergence of the magnetic field lines as a consequence of field-line random walk and flux-tube expansion. We show that the field-line random walk in the absence of flux-tube expansion produces an rms spread of field lines significantly less than that which is required to produce to observed divergence. We find that observations of the solar wind and its source region at the time of the event can account for the observations in terms of propagation along interplanetary magnetic field-lines. Klassen, A., Dresing, N., Gomez-Herrero, R, and Heber, B., A&A 580, A115 (2015) Financial support for NS and YMW was provided by NASA and CNR.

  8. Magnetic field modification to the relativistic runaway electron avalanche length

    Science.gov (United States)

    Cramer, E. S.; Dwyer, J. R.; Rassoul, H. K.

    2016-11-01

    This paper explores the impact of the geomagnetic field on the relativistic runaway electron avalanche length, λe-. Coleman and Dwyer (2006) developed an analytical fit to Monte Carlo simulations using the Runaway Electron Avalanche Model. In this work, we repeat this process but with the addition of the geomagnetic field in the range of [100,900]/n μT, where n is the ratio of the density of air at altitude to the sea level density. As the ambient electric field approaches the runaway threshold field (Eth≈284 kV/m sea level equivalent), it is shown that the magnetic field has an impact on the orientation of the resulting electron beam. The runaway electrons initially follow the vertically oriented electric field but then are deflected in the v × B direction, and as such, the electrons experience more dynamic friction due to the increase in path length. This will be shown to result in a difference in the avalanche length from the case where B = 0. It will also be shown that the average energy of the runaway electrons will decrease while the required electric field to produce runaway electrons increases. This study is also important in understanding the physics of terrestrial gamma ray flashes (TGFs). Not only will this work impact relativistic feedback rates determined from simulations, it may also be useful in studying spectroscopy of TGFs observed from balloon and aircraft measurements. These models may also be used in determining beaming properties of TGFs originating in the tropical regions seen from orbiting spacecraft.

  9. Induced Compton Scattering by Relativistic Electrons in Magnetized Astrophysical Plasmas.

    Science.gov (United States)

    Sincell, Mark William

    1994-01-01

    The effects of stimulated scattering on high brightness temperature radiation are studied in two important contexts. In the first case, we assume that the radiation is confined to a collimated beam traversing a relativistically streaming magnetized plasma. When the plasma is cold in the bulk frame, stimulated scattering is only significant if the angle between the photon motion and the plasma velocity is less than gamma^{-1} , where gamma is the bulk Lorentz factor. Under the assumption that the center of the photon beam is parallel to the bulk motion, we calculate the scattering rate as a function of the angular spread of the beam and gamma. Magnetization changes the photon recoil, without which stimulated scattering has no effect. It also introduces a strong dependence on frequency and polarization: if the photon frequency matches the electron cyclotron frequency, the scattering rate of photons polarized perpendicular to the magnetic field can be substantially enhanced relative to Thomson, and if the photon frequency is much less than the cyclotron frequency the scattering is suppressed. Applying these calculations to pulsars, we find that stimulated scattering of the radio beam in the magnetized wind believed to exist outside the light cylinder can substantially alter the spectrum and polarization state of the radio signal. We suggest that the scattering rate is so high in some pulsars that the ability of the radio signal to penetrate the pulsar magnetosphere requires modification of either the conventional model of the magnetosphere or assumptions about the effects of stimulated scattering upon a beam. In the second case, we present a model of the radio emission from synchrotron self-absorbed sources, including the effects of induced Compton scattering by the relativistic electrons in the source. Order of magnitude estimates show that stimulated scattering becomes the dominant absorption process when (kTB/m ec^2)tau_{T }_sp{~}> 0.1. Numerical simulations

  10. Magnetic anisotropy of pure and doped YbInCu sub 4 compounds at ambient and high pressures

    CERN Document Server

    Mushnikov, N V; Rozenfeld, E V; Yoshimura, K; Zhang, W; Yamada, M; Kageyama, H

    2003-01-01

    The susceptibility and high-field magnetization of single-crystalline Yb sub 1 sub - sub x Y sub x InCu sub 4 (x = 0, 0.2 and 0.3) samples have been measured for different field orientations at ambient and high pressures. The compounds with x = 0 and 0.2 undergo a first-order valence transition from the intermediate-valence state to the trivalent state on increasing either temperature or magnetic field. The magnetization and susceptibility of these compounds have appreciable anisotropy in both states. The magnetic phase diagram of Yb sub 1 sub - sub x Y sub x InCu sub 4 determined at ambient pressure is also anisotropic, which is explained by the crystal-field calculations for the free Yb ion in the high-temperature phase. Moreover, the low-temperature magnetization process for x = 0.2 and 0.3 has been measured in low fields under high pressure; it shows anisotropic ferromagnetic ordering.

  11. Effect of electron-electron interaction on the magnetic moment and susceptibility of a parabolic GaAs quantum dot

    Science.gov (United States)

    Boda, Aalu; Kumar, D. Sanjeev; Sankar, I. V.; Chatterjee, Ashok

    2016-11-01

    The problem of a parabolically confined two-dimensional semiconductor GaAs quantum dot with two interacting electrons in the presence of an external magnetic field and the spin-Zeeman interaction is studied using a method of numerical diagonalization. The energy spectrum is calculated as a function of the magnetic field. The magnetic moment (M) and the magnetic susceptibility (χ) show zero temperature diamagnetic peaks due to the exchange induced singlet-triplet transitions. The position and the number of these peaks depend both on the confinement strength of the quantum dot and the strength of the electron-electron interaction (β) .

  12. Nanoscale magnetic hysteresis of Ni80Fe20/Au/Co trilayers using ballistic electron magnetic microscopy

    NARCIS (Netherlands)

    Haq, E.; Gokcan, H.; Banerjee, T.; Postma, F.M.; Siekman, M.H.; Jansen, R.; Lodder, J.C.

    2004-01-01

    Ballistic electron magnetic microscopy is used to study spin-dependent hot-electron transport and local magnetic switching of ferromagnetic thin films grown on a Au/Si(100) collector. For Ni80Fe20 films, the collector current is a factor of 2 larger than for Co, consistent with the shorter hot-elect

  13. Electronic and Magnetic Properties of Ultrathin Au/Pt Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Teng, X.; Feygenson, M; Wang, Q; He, J; Du, W; Frenkel, A; Han, W; Aronson, M

    2009-01-01

    We have reported the synthesis of Au25Pt75 and Au48Pt52 alloyed ultrathin nanowires with average widths of less than 3 nm via a wet chemistry approach at room temperature. Using a combination of techniques, including scanning transmission electron microscopy equipped with X-ray energy dispersive spectroscopy, ultraviolet-visible spectroscopy, and X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies, we identified the stoichiometry-dependent heterogeneous crystalline structures, as well as electronic structures with respect to the charge transfer between Pt and Au within both nanowires. In particular, we observed d-charge depletion at the Au site and the d-charge gain at the Pt site in Au48Pt52 nanowires, which accounted for its ferromagnetic magnetic behavior, in contrast to the paramagnetism and diamagnetism appearing respectively in bulk Pt and Au.

  14. Electronic and magnetic properties of ultrathin Au/Pt nanowires.

    Science.gov (United States)

    Teng, Xiaowei; Feygenson, Mikhail; Wang, Qi; He, Jiaqing; Du, Wenxin; Frenkel, Anatoly I; Han, Weiqiang; Aronson, Meigan

    2009-09-01

    We have reported the synthesis of Au(25)Pt(75) and Au(48)Pt(52) alloyed ultrathin nanowires with average widths of less than 3 nm via a wet chemistry approach at room temperature. Using a combination of techniques, including scanning transmission electron microscopy equipped with X-ray energy dispersive spectroscopy, ultraviolet-visible spectroscopy, and X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopies, we identified the stoichiometry-dependent heterogeneous crystalline structures, as well as electronic structures with respect to the charge transfer between Pt and Au within both nanowires. In particular, we observed d-charge depletion at the Au site and the d-charge gain at the Pt site in Au(48)Pt(52) nanowires, which accounted for its ferromagnetic magnetic behavior, in contrast to the paramagnetism and diamagnetism appearing respectively in bulk Pt and Au.

  15. Pure ground glass nodular adenocarcinomas: Are preoperative positron emission tomography/computed tomography and brain magnetic resonance imaging useful or necessary?

    Science.gov (United States)

    Cho, Hyoun; Lee, Ho Yun; Kim, Jhingook; Kim, Hong Kwan; Choi, Joon Young; Um, Sang-Won; Lee, Kyung Soo

    2015-09-01

    The utility of (18)F-Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) scanning and brain magnetic resonance imaging (MRI) as a staging workup for lung adenocarcinoma manifesting as pure ground glass opacity (GGO) is unknown. The purpose of this study was to determine the utility of these 2 tests for preoperative staging of pure GGO nodular lung adenocarcinoma. The study included 164 patients (male:female, 73:91; mean age, 62 years) with pure GGO nodular lung adenocarcinoma who underwent PET/CT (in 136 patients) and/or brain MRI (in 109 patients) before surgery. Pathologic N staging and dedicated standard imaging or follow-up imaging findings for M staging were used as reference standards. The median follow-up time was 47.9 months. On PET/CT scan, abnormal FDG uptake of lymph nodes was found in 2 of 136 patients (1.5%); both were negative on final pathology. Abnormal FDG uptake of the liver was detected in 1 patient, which was also confirmed to be negative by dedicated abdominal CT. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of PET/CT in detecting metastases were not applicable, 98% (95% confidence interval [CI], 94%-100%), 0% (95% CI, 0%-71%), 100% (95% CI, 97%-100%), and 98% (95% CI, 94%-100%), respectively. No brain metastasis was found in preoperative brain MRI of 109 patients. Of 109 patients, 1 (0.9%) developed brain metastasis 30 months after surgical resection. PET/CT and brain MRI is not necessary in the staging of pure GGO nodular lung adenocarcinoma. Copyright © 2015 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.

  16. Structural, magnetic, and electronic properties of high moment FeCo nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zehani, K., E-mail: zehani@icmpe.cnrs.fr [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Bez, R. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); LMOP, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Boutahar, A. [LPMMAT, Université Hassan II, Faculté des Sciences Ain Chock, B.P.5366 Maârif, Route d’El Jadida, km-8, Casablanca (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Lassri, H. [LPMMAT, Université Hassan II, Faculté des Sciences Ain Chock, B.P.5366 Maârif, Route d’El Jadida, km-8, Casablanca (Morocco); Moscovici, J. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France); Mliki, N. [LMOP, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Tunis (Tunisia); Bessais, L. [CMTR, ICMPE, UMR7182, CNRS – Université Paris Est Créteil, 2-8 rue Henri Dunant, F-94320 Thiais (France)

    2014-04-05

    Highlights: • The nanoparticles cobalt ferrite was synthesized in polyol medium (10 nm). • Subsequently, the ferrite is annealed under argon at 873 K for different times. • After annealing, we have obtained of nanoparticles FeCo. • Their Structural, electronic, and magnetic properties have been presented. • The sample annealed at 873 K for 4 h exhibits the best M{sub s} (M{sub s} = 235 emu g{sup −1}). -- Abstract: Soft-magnetic Fe{sub 55}Co{sub 45} alloy nanoparticles have been successfully synthesized by the polyol reduction process followed by annealing under argon. The diethylene glycol (DEG) was used as solvent and reducing agent simultaneously in this process. The synthesized samples of nanoparticles were annealed at 873 K for different times. The alloy formation processes, the evolution of the microstructure, the magnetic properties, and the DOS calculation have been investigated before and after samples annealing. The X-ray diffraction of the synthesized product before annealing shows that a cobalt ferrite is spinel structure of crystallite size of about 10 nm. X-ray diffraction analysis of the samples annealed at 873 K for different times also shows that of the FeCo alloy has been obtained by reducing the cobalt ferrite. It has been confirmed the formation of a body-centered-cubic (bcc) single phase structure where the wt.% increases with annealing times leading to a pure phase after annealing during 4 h. These results are confirmed by transmission electron microscopy study. The saturation magnetization of the Fe–Co alloys increases with annealing time, indicating an increasing homogeneity in composition and the single bcc FeCo phase formation. The highest saturation magnetization of 235 emu g{sup −1}with a low coercivity of 76 Oe was obtained for the Fe{sub 55}Co{sub 45}nanoparticles annealed during 4 h. The local random anisotropy constant K{sub L} has been extracted. This work presents also detailed information about total, and atom

  17. Magnetic interactions and electronic structure of Ni–Mn–In

    Energy Technology Data Exchange (ETDEWEB)

    D' Souza, Sunil Wilfred [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India); Chakrabarti, Aparna [Raja Ramanna Centre for Advanced Technology, Indore 452013, Madhya Pradesh (India); Barman, Sudipta Roy, E-mail: barmansr@gmail.com [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452001, Madhya Pradesh (India)

    2016-04-15

    Highlights: • The ground state of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} is ferromagnetic. • The magnetic moments of Ni–Mn–In are in good agreement with the magnetization measurements. • Exchange coupling parameters exhibit a strong competition between ferromagnetic and antiferromagnetic configurations. • Jahn–Teller splitting of the Ni 3d e{sub g} states drives the martensite transformation. - Abstract: The electronic structure and magnetic properties of a magnetic shape memory alloy Ni–Mn–In have been studied using spin polarized fully relativistic Korringa–Kohn–Rostoker (SPRKKR) method. The total energy calculations with different starting magnetic spin configurations show that the ground state of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} is ferromagnetic. The spin and orbital magnetic moments of Ni{sub 2}Mn{sub 1.4}In{sub 0.6} and Ni{sub 2}MnIn are in good agreement with the magnetization measurements. The exchange coupling parameters of the different sublattice interactions exhibit a strong competition between ferromagnetic and antiferromagnetic configurations, due to the substitution of excess Mn atoms at the In site in Ni{sub 2}Mn{sub 1.4}In{sub 0.6}. The Curie temperature of Ni{sub 2}MnIn, calculated under a mean field approximation, is found to be in relatively good agreement with the experimental values. While Ni{sub 2}MnIn does not undergo martensite transition, it is shown that a Jahn–Teller splitting of the Ni 3d e{sub g} states plays an important role in driving the martensite transformation in Ni{sub 2}Mn{sub 1.4}In{sub 0.6}. We find that both the calculated ultra-violet photoemission spectra and the inverse photoemission spectra are in good agreement with the existing experimental data.

  18. Liquid scintillation counting efficiency in three photomultiplier systems. Pure electron capture; Eficiencia de recuento por centelleo liquido en sistemas con tres fotomultiplicadores. Captura electronica pura

    Energy Technology Data Exchange (ETDEWEB)

    Los Arcos, J. M.; Grau Carles, A.; Grau Malonda, A.

    1990-07-01

    The tables of counting efficiency as a function of the figure of merit for a liquid scintillation counting system working with three phototubes are presented. The evaluation has been carried out for a Toluene-based scintillator with 5, 10 and 15 ml column, and 19 different radionuclides decaying by pure electron capture: 37Ar 41Ca, 49V, 53 Mn, 55Fe, 59Ni, 68Ge 7iGe, 82Sr, 97Tc, 118Te, 131CS, 137La, 140Ca, 157Tb, 165Er, 193Pt, 194Hg, 205Pb. (Author) 22 refs.

  19. The irradiation of pure CH3OH and 1:1 mixture of NH3:CH3OH ices at 30 K using low energy electrons

    Science.gov (United States)

    Jheeta, Sohan; Domaracka, A.; Ptasinska, S.; Sivaraman, B.; Mason, N. J.

    2013-01-01

    The results of an experimental investigation of 1 keV electron irradiation of ices (deposited at 30 K) of (i) pure methanol and (ii) of a 1:1 mixture of NH3:CH3OH are reported. Molecular products formed within the ice were detected and monitored using FTIR spectroscopy. The products observed were methyl formate (H3COHCO), methane (CH4), hydroxymethyl (CH2OH), formamide (HCONH2), formic acid (HCOOH), formaldehyde (H2CO), formyl radical (HCO), cyanate ion (OCN-), isocyanic acid (HNCO), carbon monoxide (CO) and carbon dioxide (CO2). The consequences of these results for prebiotic chemistry in the interstellar medium and star forming regions are discussed.

  20. Vlasov simulations of electron hole dynamics in inhomogeneous magnetic field

    Science.gov (United States)

    Kuzichev, Ilya; Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton

    2017-04-01

    Electron holes (EHs) or phase space vortices are solitary electrostatic waves existing due to electrons trapped within EH electrostatic potential. Since the first direct observation [1], EHs have been widely observed in the Earth's magnetosphere: in reconnecting current sheets [2], injection fronts [3], auroral region [4], and many other space plasma systems. EHs have typical spatial scales up to tens of Debye lengths, electric field amplitudes up to hundreds of mV/m and propagate along magnetic field lines with velocities of about electron thermal velocity [5]. The role of EHs in energy dissipation and supporting of large-scale potential drops is under active investigation. The accurate interpretation of spacecraft observations requires understanding of EH evolution in inhomogeneous plasma. The critical role of plasma density gradients in EH evolution was demonstrated in [6] using PIC simulations. Interestingly, up to date no studies have addressed a role of magnetic field gradients in EH evolution. In this report, we use 1.5D gyrokinetic Vlasov code to demonstrate the critical role of magnetic field gradients in EH dynamics. We show that EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. Remarkably, the reflection points of decelerating EHs are independent of the average magnetic field gradient in the system and depend only on the EH parameters. EHs are decelerated (accelerated) faster than would follow from the "quasi-particle" concept assuming that EH is decelerated (accelerated) entirely due to the mirror force acting on electrons trapped within EH. We demonstrate that EH propagation in inhomogeneous magnetic fields results in development of a net potential drop along an EH, which depends on the magnetic field gradient. The revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. In

  1. Cooling of ions and antiprotons with magnetized electrons

    CERN Document Server

    Mollers, B; Walter, M; Zwicknagel, G; Carli, Christian; Nersisyan, H

    2004-01-01

    Electron cooling is a well-established method to improve the phase space quality of ion beams in storage rings. More recently antiprotons have been cooled in traps, first by electrons and then by positrons in order to produce antihydrogen atoms as simplest form of antimatter for CPT-tests. During these cooling processes the light particles are guided by strong external magnetic fields which imposes a challenge to the theoretical description. Within the binary collision model we treat the Coulomb interaction as second-order perturbation to the helix motion of the light particles and also by numerical simulations. In the complementary dielectric theory we calculate the polarization of the light particles by solving the nonlinear Vlasov-Poisson equation as well as linear response. It turns out that the linearization becomes dubious at low ion velocities. In the presence of a strong magnetic field the numerically expensive solution of the Vlasov-Poisson equation is the method of choice, alternatively one may empl...

  2. Electron acceleration in an ion channel by a magnetized plasma wave

    Directory of Open Access Journals (Sweden)

    A. Kargarian

    2014-04-01

    Full Text Available In this paper, the acceleration of an electron in the interaction with a plasma wave and a magnetized ion-channel is analyzed. The electron dynamics is studied treated employing complete three-dimensional Lorentz force equations. A relativistic three dimensional single particle code is used to obtain the electron-trajectories. The results of numerical calculation show that the electrons can be accelerated in the magnetized channel. Furthermore, the electron energy gain with axial magnetic field is compared to that without axial magnetic field.

  3. Electronic and magnetic properties of iron doped zirconia: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Debernardi, A., E-mail: alberto.debernardi@mdm.imm.cnr.it; Sangalli, D.; Lamperti, A.; Cianci, E. [Laboratorio MDM, IMM-CNR, 20864 Agrate Brianza (MB) (Italy); Lupo, P.; Casoli, F.; Albertini, F.; Nasi, L. [CNR-IMEM, Parco Area delle Scienze 37/A, 43124 Parma (Italy); Ciprian, R.; Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14 km 163.5, Basovizza, I-34149 Trieste (Italy)

    2014-05-07

    We systematically investigated, both theoretically and experimentally, Zr{sub 1−x}Fe{sub x}O{sub 2−y} ranging from diluted (x ≈ 0.05) up to large (x ≈ 0.25) Fe concentration. By atomic layer deposition, we grew thin films of high-κ zirconia in cubic phase with Fe uniformly distributed in the film, as proven by time of flight secondary ion mass spectrometry and transmission electron microscopy measurements. Iron is in Fe{sup 3+} oxidation state suggesting the formation of oxygen vacancies with y concentration close to x/2. By ab-initio simulations, we studied the phase diagram relating the stability of monoclinic vs. tetragonal phase as a function of Fe doping and film thickness: the critical thickness at which the pure zirconia is stabilized in the tetragonal phase is estimated ranging from 2 to 6 nm according to film morphology. Preliminary results by X-ray magnetic circular dichroism and alternating gradient force magnetometry are discussed in comparison to ab initio data enlightening the role of oxygen vacancies in the magnetic properties of the system.

  4. Synthesis of pure colloidal silver nanoparticles with high electroconductivity for printed electronic circuits: the effect of amines on their formation in aqueous media.

    Science.gov (United States)

    Natsuki, Jun; Abe, Takao

    2011-07-01

    This paper describes a practical and convenient method to prepare stable colloidal silver nanoparticles for use in printed electronic circuits. The method uses a dispersant and two kinds of reducing agents including 2-(dimethylamino) ethanol (DMAE), which play important roles in the reduction of silver ions in an aqueous medium. The effect of DMAE and dispersant, as well as the factors affecting particle size and morphology are investigated. In the formation of the silver nanoparticles, reduction occurs rapidly at room temperature and the silver particles can be separated easily from the mixture in a short time. In addition, organic solvents are not used. Pure, small and relatively uniform particles with a diameter less than 10 nm can be obtained that exhibit high electroconductivity. The silver nanoparticles are stable, and can be isolated as a dried powder that can be fully redispersed in deionized water. This method of producing colloidal silver nanoparticles will find practical use in electronics applications.

  5. Doping-dependent magnetization plateaus of a coupled spin-electron chain: exact results

    Science.gov (United States)

    Strečka, Jozef; Čisárová, Jana

    2016-10-01

    A coupled spin-electron chain composed of localized Ising spins and mobile electrons is exactly solved in an external magnetic field within the transfer-matrix method. The ground-state phase diagram involves in total seven different ground states, which differ in the number of mobile electrons per unit cell and the respective spin arrangements. A rigorous analysis of the low-temperature magnetization process reveals doping-dependent magnetization plateaus, which may be tuned through the density of mobile electrons. It is demonstrated that the fractional value of the electron density is responsible for an enhanced magnetocaloric effect due to an annealed bond disorder of the mobile electrons.

  6. Cross-field transport of electrons at the magnetic throat in an annular plasma reactor

    Science.gov (United States)

    Zhang, Yunchao; Charles, Christine; Boswell, Rod

    2017-01-01

    Cross-field transport of electrons has been studied at the magnetic throat of the annular Chi-Kung reactor. This annular configuration allows the creation of a low pressure argon plasma with two distinct electron heating locations by independently operating a radio-frequency antenna surrounding the outer source tube, or an antenna housed inside the inner source tube. The two antenna cases show opposite variation trends in radial profiles of electron energy probability function, electron density, plasma potential and electron temperature. The momentum and energy transport coefficients are obtained from the electron energy probability functions, and the related electron fluxes follow the path of electron cooling across the magnetic throat.

  7. Analysis of magnetically immersed electron guns with non-adiabatic fields

    Science.gov (United States)

    Pikin, Alexander; Alessi, James G.; Beebe, Edward N.; Raparia, Deepak; Ritter, John

    2016-11-01

    Electron diode guns, which have strongly varying magnetic or electric fields in a cathode-anode gap, were investigated in order to generate laminar electron beams with high current density using magnetically immersed guns. By creating a strongly varying radial electric field in a cathode-anode gap of the electron gun, it was demonstrated that the optical properties of the gun can be significantly altered, which allows the generation of a laminar, high-current electron beam with relatively low magnetic field on the cathode. The relatively high magnetic compression of the electron beam achieved by this method is important for producing electron beams with high current density. A similar result can be obtained by inducing a strong variation of the magnetic field in a cathode-anode gap. It was observed that creating a dip in the axial magnetic field in the cathode-anode gap of an adiabatic electron gun has an optical effect similar to guns with strong variation of radial electric field. By analyzing the electron trajectories angles and presenting the results in a gun performance map, different geometries of magnetically immersed electron guns with non-adiabatic fields are compared with each other and with a more traditional adiabatic electron gun. Some advantages and limitations of guns with non-adiabatic fields are outlined. The tests' results of a non-adiabatic electron gun with modified magnetic field are presented.

  8. How to probe transverse magnetic anisotropy of a single-molecule magnet by electronic transport?

    Science.gov (United States)

    Misiorny, M.; Burzuri, E.; Gaudenzi, R.; Park, K.; Leijnse, M.; Wegewijs, M.; Paaske, J.; Cornia, A.; van der Zant, H.

    We propose an approach for in-situ determination of the transverse magnetic anisotropy (TMA) of an individual molecule by electronic transport measurements, see Phys. Rev. B 91, 035442 (2015). We study a Fe4 single-molecule magnet (SMM) captured in a gateable junction, a unique tool for addressing the spin in different redox states of a molecule. We show that, due to mixing of the spin eigenstates of the SMM, the TMA significantly manifests itself in transport. We predict and experimentally observe the pronounced intensity modulation of the Coulomb peak amplitude with the magnetic field in the linear-response transport regime, from which the TMA parameter E can be estimated. Importantly, the method proposed here does not rely on the small induced tunnelling effects and, hence, works well at temperatures and electron tunnel broadenings by far exceeding the tunnel splittings and even E itself. We deduce that the TMA for a single Fe4 molecule captured in a junction is substantially larger than the bulk value. Work supported by the Polish Ministry of Science and Education as `Iuventus Plus' project (IP2014 030973) in years 2015-2016.

  9. Non-local electron energy probability function in a plasma expanding along a magnetic nozzle.

    Directory of Open Access Journals (Sweden)

    Roderick William Boswell

    2015-03-01

    Full Text Available Electron energy probability functions (eepfs have been measured along the axis of low pressure plasma expanding in a magnetic nozzle. The eepf at the maximum magnetic field of the nozzle shows a depleted tail commencing at an energy corresponding to the measured potential drop in the magnetic nozzle. The eepfs measured along the axis demonstrate that the potential and kinetic energies of the electrons are conserved and confirm the non-local collisionless kinetics of the electron dynamics.

  10. Simulation of runaway electrons, transport affected by J-TEXT resonant magnetic perturbation

    Science.gov (United States)

    Jiang, Z. H.; Wang, X. H.; Chen, Z. Y.; Huang, D. W.; Sun, X. F.; Xu, T.; Zhuang, G.

    2016-09-01

    The topology of a magnetic field and transport properties of runaway electrons can be changed by a resonant magnetic perturbation field. The J-TEXT magnetic topology can be effectively altered via static resonant magnetic perturbation (SRMP) and dynamic resonant magnetic perturbation (DRMP). This paper studies the effect of resonant magnetic perturbation (RMP) on the confinement of runaway electrons via simulating their drift orbits in the magnetic perturbation field and calculating the orbit losses for different runaway initial energies and different runaway electrons, initial locations. The model adopted is based on Hamiltonian guiding center equations for runaway electrons, and the J-TEXT magnetic turbulences and RMP are taken into account. The simulation indicates that the loss rate of runaway electrons is sensitive to the radial position of electrons. The loss of energetic runaway beam is dominated by the shrinkage of the confinement region. Outside the shrinkage region of the runaway electrons are lost rapidly. Inside the shrinkage region the runaway beam is confined very well and is less sensitive to the magnetic perturbation. The experimental result on the response of runaway transport to the application RMP indicates that the loss of runaway electrons is dominated by the shrinkage of the confinement region, other than the external magnetic perturbation.

  11. Electronic and magnetic properties of UPdSn: the itinerant 5f electrons approach

    CERN Document Server

    Sandratskii, L M

    1997-01-01

    Density functional theory, modified to include spin-orbit coupling and an effective orbital field to simulate Hound's second rule, is applied to investigate the magnetic structure and electronic properties of the compound Upends. Our theoretical results are in overall good agreement with experiment. Thus both theory and experiment find the magnetic structure of Upends to be non collinear, the calculated magnetic U-moments being in very good agreement with the measurements. Also, the calculated density of states is found to simulate closely the photoemission spectrum and the very low experimental value of 5 mJ mol sup - sup 1 K sup - sup 2 for the specific heat gamma is reproduced reasonably well by the calculated value of 7.5 mJ mol sup - sup 1 K sup - sup 2. Furthermore, the interconnection of the magnetic structure with the crystal structure is investigated. Here theory and experiment agree concerning the planar non collinear antiferromagnetic configuration in the orthorhombic crystal structure and for the ...

  12. Retraction notice to "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps" [Chinese Optics Letters 9, 060201 (2011)

    Institute of Scientific and Technical Information of China (English)

    Jicheng Wang; Yueyuan Wang; Yueke Wang; Guangyu Fang; Shutian Liu

    2011-01-01

    This article "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps",which was published on Chinese Optics Letters (9,060201 (2011)) has been retracted at the request of the authors.Reason:The first author,Jicheng Wang,participated in a related research in Professor Kirk Madison's group in the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Some of the experimental data have not been authorized for publication,even though they have been consented to be used by Jicheng Wang in his own research.The authors apologize to Professor K.Madison for misunderstanding,and to Chinese Optics Letters and the readers of Chinese Optics Letters for any inconvenience this mistake may have caused.

  13. Electron magnetic resonance investigation of chromium diffusion in yttria powders

    Energy Technology Data Exchange (ETDEWEB)

    Biasi, R.S. de, E-mail: rsbiasi@ime.eb.b [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, Pr. General Tiburcio, 80, 22290-270 Rio de Janeiro, RJ (Brazil); Grillo, M.L.N., E-mail: mluciag@uerj.b [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

    2010-03-01

    The electron magnetic resonance (EMR) technique was used to investigate the diffusion of chromium in yttria (Y{sub 2}O{sub 3}) powders. The EMR absorption intensity was measured for several annealing times and three different temperatures of isothermal annealing: 1273, 1323 and 1373 K. The activation temperature for diffusion, calculated from the experimental data using a theoretical model based on the Fick equation, was found to be E{sub A}=342+-5 kJ mol{sup -1}. This value is larger than the activation energy for the diffusion of chromium in rutile (TiO{sub 2}), periclase (MgO) and cobalt monoxide (CoO) and smaller than the activation energy for the diffusion of chromium in chrysoberyl (BeAl{sub 2}O{sub 4}).

  14. Counterstreaming electrons in small interplanetary magnetic flux ropes

    Science.gov (United States)

    Feng, H. Q.; Zhao, G. Q.; Wang, J. M.

    2015-12-01

    Small interplanetary magnetic flux ropes (SIMFRs) are commonly observed by spacecraft at 1 AU, and their origin still remains disputed. We investigated the counterstreaming suprathermal electron (CSE) signatures of 106 SIMFRs measured by Wind during 1995-2005. We found that 79 (75%) of the 106 flux ropes contain CSEs, and the percentages of counterstreaming vary from 8% to 98%, with a mean value of 51%. CSEs are often observed in magnetic clouds (MCs), and this indicates these MCs are still attached to the Sun at both ends. CSEs are also related to heliospheric current sheets (HCSs) and the Earth's bow shock. We divided the SIMFRs into two categories: The first category is far from HCSs, and the second category is in the vicinity of HCSs. The first category has 57 SIMFRs, and only 7 of 57 ropes have no CSEs. This ratio is similar to that of MCs. The second category has 49 SIMFRs; however, 20 of the 49 events have no CSEs. This ratio is larger than that of MCs. These two categories have different origins. One category originates from the solar corona, and most ropes are still connected to the Sun at both ends. The other category is formed near HCSs in the interplanetary space.

  15. Electronic structure of the pure and Ti-doped Sr2RuO4 superconductor obtained by the embedded cluster method

    Science.gov (United States)

    Kaplan, Ilya G.; Soullard, Jacques

    2007-11-01

    Electronic structure of the pure and Ti-doped Sr2RuO4 superconductor is studied by the embedded cluster method at the Hartree-Fock (HF) and the second-order Møller-Plesset perturbation theory (MP2) electron correlation levels. The representative cluster was embedded into the Madelung potential that mimics a real crystal. The interatomic interaction leads to an effective electron transfer from O to Ru at both the HF and MP2 levels. At the MP2 level, we obtained the Ru charge equal to +1.57 , instead of +4 in the formal valence (ionic) model. The eg level, which was assumed empty in most of the previous studies, was found partly populated. The Ti substitution almost does not change the atomic charges, but induces the essential charge redistribution between d orbitals of Ru that leads to an increase of the eg population. A drastic effect of the Ti impurity on the spin density distribution was revealed; it strongly depends on the electron correlation. In undoped crystals, the MP2 spin density is located only on the Ru and Sr atoms. In the Ti-substituted crystals, the local spin density near an impurity disappears on Sr and localizes on Ru and four O atoms, surrounding it, on orbitals directed along the z axis. The latter are in complete agreement with experiments by Maeno and co-workers [Phys. Rev. B 63, 180504(R) (2001); Phys. Rev. Lett. 88, 197002 (2002)].

  16. Nonlinear evolution of electron shear flow instabilities in the presence of an external guide magnetic field

    CERN Document Server

    Jain, Neeraj

    2016-01-01

    The dissipation mechanism by which the magnetic field reconnects in the presence of an external (guide) magnetic field in the direction of the main current is not well understood. In thin electron current sheets (ECS) (thickness ~ an electron inertial length) formed in collisionless magnetic reconnection, electron shear flow instabilities (ESFI) are potential candidates for providing an anomalous dissipation mechanism which can break the frozen-in condition of the magnetic field affecting the structure and rate of reconnection. We investigate the evolution of ESFI in guide field magnetic reconnection. The properties of the resulting plasma turbulence and their dependence on the strength of the guide field are studied. Utilizing 3-D electron-magnetohydrodynamic simulations of ECS we show that, unlike the case of ECS self-consistently embedded in anti-parallel magnetic fields, the evolution of thin ECS in the presence of a guide field (equal to the asymptotic value of the reconnecting magnetic field or larger) ...

  17. Development of High-frequency Soft Magnetic Materials for Power Electronics

    Directory of Open Access Journals (Sweden)

    LIU Jun-chang

    2017-05-01

    Full Text Available The new requirements of high-frequency magnetic properties are put forward for electronic components with the rapid development of power electronics industry and the use of new electromagnetic materials. The properties of magnetic core, which is the key unit of electronic components, determine the performance of electronic components directly. Therefore, it's necessary to study the high-frequency soft magnetic materials. In this paper, the development history of four types of soft magnetic materials was reviewed. The advantages and disadvantages of each kind of soft magnetic materials and future development trends were pointed out. The emphases were placed on the popular soft magnetic composite materials in recent years. The tendency is to develop high-frequency soft magnetic composite materials with the particle size controllable, uniform coating layer on the core and a mass production method from laboratory to industrialization.

  18. Electron Velocity Distribution Function in Magnetic Clouds in the Solar Wind

    Science.gov (United States)

    Nieves-Chinchil, Teresa; Vinas, Adolfo F.; Bale, Stuart D.

    2006-01-01

    We present a study of the kinetic properties of the electron velocity distribution functions within magnetic clouds, since they are the dominant thermal component. The study is based on high time resolution data from the GSFC WIND/SWE electron spectrometer and the Berkeley 3DP electron plasma instruments. Recent studies on magnetic clouds have shown observational evidence of anti-correlation between the total electron density and electron temperature, which suggest a polytrope law P(sub e) = alpha(Nu(sub e) (sup gamma)) for electrons with the constant gamma approximates 0.5 non-Maxwellian electron distributions (i.e. non-thermal) within magnetic clouds. These works suggested that the non-thermal electrons can contribute as much as 50% of the total electron pressure within magnetic clouds. We have revisited some of the magnetic cloud events previously studied and attempted to quantify the nature of the non-thermal electrons by modeling the electron velocity distribution function using a kappa distribution function to characterize the kinetic non-thermal effects. If non-thermal tail effects are the source for the anti-correlation between the moment electron temperature and density and if the kappa distribution is a reasonable representative model of non-thermal effects, then the electron velocity distribution within magnetic clouds should show indication for small K-values when gamma < 1.

  19. The Effect of Large Scale Magnetic Turbulence on the Acceleration of Electrons by Perpendicular Collisionless Shocks

    CERN Document Server

    Guo, Fan

    2010-01-01

    We study the physics of electron acceleration at collisionless shocks that move through a plasma containing large-scale magnetic fluctuations. We numerically integrate the trajectories of a large number of electrons, which are treated as test particles moving in the time dependent electric and magnetic fields determined from 2-D hybrid simulations (kinetic ions, fluid electron). The large-scale magnetic fluctuations effect the electrons in a number of ways and lead to efficient and rapid energization at the shock front. Since the electrons mainly follow along magnetic lines of force, the large-scale braiding of field lines in space allows the fast-moving electrons to cross the shock front several times, leading to efficient acceleration. Ripples in the shock front occuring at various scales will also contribute to the acceleration by mirroring the electrons. Our calculation shows that this process favors electron acceleration at perpendicular shocks. The current study is also helpful in understanding the inje...

  20. Quantum Mechanical Fourier-Hankel Representation Transform for an Electron Moving in a Uniform Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    FAN Hong-Yi

    2004-01-01

    We find quantum mechanical Fourier-Hankel representation transform for an electron moving in a uniform magnetic field. The physical meaning of Fourier decomposition states of electron's coordinate eigenstate and the momentum eigenstate are revealed.

  1. Foucault imaging and small-angle electron diffraction in controlled external magnetic fields.

    Science.gov (United States)

    Nakajima, Hiroshi; Kotani, Atsuhiro; Harada, Ken; Ishii, Yui; Mori, Shigeo

    2016-12-01

    We report a method for acquiring Foucault images and small-angle electron diffraction patterns in external magnetic fields using a conventional transmission electron microscope without any modification. In the electron optical system that we have constructed, external magnetic fields parallel to the optical axis can be controlled using the objective lens pole piece under weak excitation conditions in the Foucault mode and the diffraction mode. We observe two ferromagnetic perovskite-type manganese oxides, La0.7Sr0.3MnO3 (LSMO) and Nd0.5Sr0.5MnO3, in order to visualize magnetic domains and their magnetic responses to external magnetic fields. In rhombohedral-structured LSMO, pinning of magnetic domain walls at crystallographic twin boundaries was found to have a strong influence on the generation of new magnetic domains in external applied magnetic fields.

  2. On the Physical Origin of the Anomalous Magnetic Moment of Electron

    CERN Document Server

    Mandache, N B

    2013-01-01

    A simple physical insight into the origin of the magnetic moment anomaly of electron is presented. This approach is based on the assumption that the electromagnetic mass of the electron due to the electric field generated by electron charge in the exterior of the sphere of radius half of the Compton wavelength of the electron, does not contribute to the magnetic moment of the electron. This explanation is compatible with the well-known quantum electrodynamics approach. A formula is derived, which is similar to that obtained by quantum electrodynamics calculus of one loop contribution to anomalous part of the magnetic moment.

  3. Electron acceleration by whistler-mode waves around the magnetic null during 3D reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Fuliang [School of Physics and Electronic Sciences, Changsha University of Science and Technology, Changsha, 410004 (China); Zong Qiugang; Pu Zuyin; He Jiansen; Wang Yongfu [School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Su Zhenpeng; Zheng Huinan [CAS Key Laboratory for Basic Plasma Physics, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China); Cao Jinbin, E-mail: qgzong@pku.edu.c [State Key Laboratory of Space Weather, PO Box 8701, Beijing 100080 (China)

    2010-05-15

    The magnetic field configuration around a magnetic null pair and its associated electron behavior during 3D magnetic reconnection have recently been reported from in situ observations. Electrons are suggested to be temporarily trapped in the central reconnection region as indicated by an electron density peak observed near the magnetic null (He J-S et al 2008 Geophys. Res. Lett. 35 L14104). It is highly interesting that energetic electron beams of a few kiloelectronvolts are found to be related to the magnetic null structure. However, the acceleration mechanism is still not fully understood. In this paper, we show that strong whistler-mode electromagnetic waves are indeed found around the magnetic null. Further we propose a new electron acceleration scenario of trapped electrons near the magnetic null points driven by the whistler-mode waves, which is confirmed by numerical results. It is demonstrated that whistler waves can enhance the phase space density (PSD) of electrons for energies of approx2 keV by a factor of 100 at lower pitch angles very rapidly, typically within 2 s. The accelerated electrons may escape from the loss cone of the magnetic cusp mirrors around the magnetic null, leading to the observed energetic beams. (brief communication)

  4. Unraveling electronic and magnetic structure at cuprate-manganite interfaces

    Science.gov (United States)

    Freeland, John

    2014-03-01

    Oxide interfaces offer a rich variety of physics and a pathway to create new classes of functional oxide materials. The interface between the cuprate high-temperature superconductors and ferromagnetic manganites is of particular interest due to the strongly antagonistic nature of the superconducting and ferromagnetic phases. Advancements in the synthesis of oxide heterostructure offers the opportunity to merge these two dissimilar oxides with atomic precision to understand the fundamental limits of bringing such states into close proximity. However, the main challenge is to understand the physical framework that describes the behavior of strongly correlated electrons near oxide interfaces. One aspect that will be addressed here is the use of advanced tools to gain detailed electronic and magnetic information from the boundary region. In this talk, recent work will be addressed both in connection to visualizing the interface with spatially resolved tools as well as harnessing layer-by-layer growth to explore the limits in ultrathin superlattices. These insights allow us to better understand the physics behind the interfacial spin and orbital reconstruction observed in this system. Work at Argonne is supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.

  5. Small Explorer (SMEX) POsitron Electron Magnet Spectrometer (POEMS)

    Science.gov (United States)

    LHeureux, Jacques; Evenson, Paul A.; Aleman, R. (Technical Monitor)

    1995-01-01

    This report covers the activities of Louisiana State University (LSU) under subcontract 26053-EX between LSU and the Bartol Research Institute (Bartol), which began January 1, 1994. The purpose of this subcontract was for LSU to participate in and support Bartol in the work to define the SMEX (Small Explorer)/POEMS (Positron Electron Magnet Spectrometer) spaceflight mission under NASA Contract NAS5-38098 between NASA and Bartol. The conclusions of this study were that for a 1998 launch into a 600km altitude, 98 degrees, approximately sun synchronous orbit, (a) the total radiation dose would be typically a few k-rad per year, certainly less than 20 k-rad per year for the anticipated shielding and potential solar flare environment, (b) detector counting rates would be dominated by the South Atlantic Anomaly (SAA) and the horns of the Van Allen belts, (c) the galactic electron and positron 'signal' can be extracted from the albedo background and the trapped populations by detailed evaluation of the geomagnetic transmission function (cut-off) for each event, (d) POEMS could make significant contributions to magnetospheric science if sufficient downlink capacity were provided and, (e) a fully functioning, cost efficient, data processing and analysis facility design was developed for the mission. Overall, POEMS was found to be a relatively simple experiment to manifest, operate and analyze and had potential for fundamental new discoveries in cosmic, heliospheric, solar and magnetospheric science.

  6. Injection of electron beam into a toroidal trap using chaotic orbits near magnetic null.

    Science.gov (United States)

    Nakashima, C; Yoshida, Z; Himura, H; Fukao, M; Morikawa, J; Saitoh, H

    2002-03-01

    Injection of charged particle beam into a toroidal magnetic trap enables a variety of interesting experiments on non-neutral plasmas. Stationary radial electric field has been produced in a toroidal geometry by injecting electrons continuously. When an electron gun is placed near an X point of magnetic separatrix, the electron beam spreads efficiently through chaotic orbits, and electrons distribute densely in the torus. The current returning back to the gun can be minimized less than 1% of the total emission.

  7. Two-Electron Energy Spectrum in a Parabolic Quantum Dot Under a Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2003-01-01

    Two interacting electrons in a harmonic oscillator potential under the influence of a perpendicular homo-geneous magnetic field are considered. The energies of two-electron quantum dots with the electron-LO-phonon couplingas a function of magnetic field are calculated. Calculations are made by using the method of few-body physics withinthe effective-mass approximation. Our results show that the electron-LO-phonon coupling effect is very important insemiconductor quantum dots.

  8. Pressure of Degenerate and Relativistic electrons in a superhigh magnetic field

    CERN Document Server

    Gao, Zhi Fu; He, Peng Qiu; Jie, Du Yuan

    2013-01-01

    Based on our previous work, we deduce a general formula for pressure of degenerate and relativistic electrons,Pe, which is suitable for superhigh magnetic fields, discuss the quantization of Landau levels of electrons, and consider the quantum electrodynam-ic(QED) effects on the equations of states (EOSs) for different matter systems. The main conclusions are as follows:Pe is related to the magnetic field B, matter density ?, and electron fraction Ye ; the stronger the magnetic field, the higher the electron pressure becomes; the high electron pressure could be caused by high Fermi energy of electrons in a superhigh magnetic field; compared with a common radio pulsar, a magnetar could be a more compact oblate spheroid-like deformed neutron star due to the anisotropic total pressure; and an increase in the maximum mass of a magnetar is expected because of the positive contribution of the magnetic field energy to the EOS of the star.

  9. Electron gun for a multiple beam klystron with magnetic compression of the electron beams

    Science.gov (United States)

    Ives, R. Lawrence; Tran, Hien T; Bui, Thuc; Attarian, Adam; Tallis, William; David, John; Forstall, Virginia; Andujar, Cynthia; Blach, Noah T; Brown, David B; Gadson, Sean E; Kiley, Erin M; Read, Michael

    2013-10-01

    A multi-beam electron gun provides a plurality N of cathode assemblies comprising a cathode, anode, and focus electrode, each cathode assembly having a local cathode axis and also a central cathode point defined by the intersection of the local cathode axis with the emitting surface of the cathode. Each cathode is arranged with its central point positioned in a plane orthogonal to a device central axis, with each cathode central point an equal distance from the device axis and with an included angle of 360/N between each cathode central point. The local axis of each cathode has a cathode divergence angle with respect to the central axis which is set such that the diverging magnetic field from a solenoidal coil is less than 5 degrees with respect to the projection of the local cathode axis onto a cathode reference plane formed by the device axis and the central cathode point, and the local axis of each cathode is also set such that the angle formed between the cathode reference plane and the local cathode axis results in minimum spiraling in the path of the electron beams in a homogenous magnetic field region of the solenoidal field generator.

  10. Magnetic dynamics studied by high-resolution electron spectroscopy and time-resolved electron microscopy

    Science.gov (United States)

    Jayaraman, Rajeswari

    Future information technology requires an increased magnetically encoded data density and novel electromagnetic modes of data transfer. While to date magnetic properties are observed and characterized mostly statically, the need emerges to monitor and capture their fast dynamics. In this talk, I will focus on the spin dynamics i.e. spin wave excitations and the dynamics of a new topological distribution of spins termed ``skyrmions''. Wave packets of spin waves offer the unique capability to transport a quantum bit, the spin, without the transport of charge or mass. Here, large wave-vector spin waves are of particular interest as they admit spin localization within a few nanometers. By using our recently developed electron energy loss spectrometer, we could study such spin waves in ultrathin films with an unprecedented energy resolution of 4 meV. By virtue of the finite penetration depth of low energy electrons, spin waves localized at interfaces between a substrate and a thin capping layer can be been studied yielding information about the exchange coupling between atoms at the interface. The quantization of spin waves with wave vectors perpendicular to the film gives rise to standing modes to which EELS has likewise access. Such studies when carried out as function of the film thickness again yield information on the layer dependence of the exchange coupling. Magnetic skyrmions are promising candidates as information carriers in logic or storage devices. Currently, little is known about the influence of disorder, defects, or external stimuli on the spatial distribution and temporal evolution of the skyrmion lattice. In this talk, I will describe the dynamical role of disorder in a large and flat thin film of Cu2OSeO3, exhibiting a skyrmion phase in an insulating material. We image up to 70,000 skyrmions by means of cryo-Lorentz Transmission Electron Microscopy as a function of the applied magnetic field. In the skyrmion phase, dislocations are shown to cause the

  11. Magnetic field turbulence, electron heating, magnetic holes, proton cyclotron waves, and the onsets of bipolar pulse (electron hole events: a possible unifying scenario

    Directory of Open Access Journals (Sweden)

    B. T. Tsurutani

    2003-01-01

    Full Text Available Two electron heating events have been identified on 20 May 1996 when Polar was in the polar cap/polar cusp boundary layer. The electron heating events were located within magnetic holes/cavities/bubbles and were accompanied by nonlinear ± 14 nT peak-to-peak (f ~ 0.6 to 0.7 fcp obliquely propagating proton cyclotron waves. The electrons appear to be heated isotropically. Electric bipolar pulse (electron hole onset events were also detected within the heating events. We propose a scenario which can link the above phenomena. Nonlinear Alfvén waves, generated through cusp magnetic reconnection, propagate down magnetic field lines and locally heat electrons through the ponderomotive force. The magnetic cavity is created through the diamagnetic effect of the heated electrons. Ion heating also occurs through ponderomotive acceleration (but much less than the electrons and the protons generate the electromagnetic proton cyclotron waves through the loss cone instability. The obliquely propagating electromagnetic proton cyclotron waves accelerate bi-streaming electrons, which are the source of free energy for the electron holes.

  12. Generation of a spin-polarized electron beam by multipole magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Ebrahim, E-mail: ekarimi@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Grillo, Vincenzo [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Institute of Optics, University of Rochester, Rochester, NY 14627 (United States); Santamato, Enrico [Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, 80126 Napoli (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Napoli (Italy)

    2014-03-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin–magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. - Highlights: • Theory of generating spin-polarized electron beams. • Interacting electron vortex beams with space-variant magnetic fields. • Bohr–Pauli impossibility of generating spin-polarized free electrons.

  13. Magnetic Coupling Constants in Three Electrons Three Centers Problems from Effective Hamiltonian Theory and Validation of Broken Symmetry-Based Approaches.

    Science.gov (United States)

    Reta, Daniel; Moreira, Ibério de P R; Illas, Francesc

    2016-07-12

    In the most general case of three electrons in three symmetry unrelated centers with Ŝ1 = Ŝ2 = Ŝ3 = 1/2 localized magnetic moments, the low energy spectrum consists of one quartet (Q) and two doublet (D1, D2) pure spin states. The energy splitting between these spin states can be described with the well-known Heisenberg-Dirac-Van Vleck (HDVV) model spin Hamiltonian, and their corresponding energy expressions are expressed in terms of the three different two-body magnetic coupling constants J12, J23, and J13. However, the values of all three magnetic coupling constants cannot be extracted using the calculated energy of the three spin-adapted states since only two linearly independent energy differences between pure spin states exist. This problem has been recently investigated by Reta et al. (J. Chem. Theory Comput. 2015, 11, 3650), resulting in an alternative proposal to the original Noodleman's broken symmetry mapping approach. In the present work, this proposal is validated by means of ab initio effective Hamiltonian theory, which allows a direct extraction of all three J values from the one-to-one correspondence between the matrix elements of both effective and HDVV Hamiltonian. The effective Hamiltonian matrix representation has been constructed from configuration interaction wave functions for the three spin states obtained for two model systems showing a different degree of delocalization of the unpaired electrons. These encompass a trinuclear Cu(II) complex and a π-conjugated purely organic triradical.

  14. Structural, electronic, and magnetic investigation of magnetic ordering in MBE-grown CrxSb2-xTe3 thin films

    Science.gov (United States)

    Collins-McIntyre, L. J.; Duffy, L. B.; Singh, A.; Steinke, N.-J.; Kinane, C. J.; Charlton, T. R.; Pushp, A.; Kellock, A. J.; Parkin, S. S. P.; Holmes, S. N.; Barnes, C. H. W.; van der Laan, G.; Langridge, S.; Hesjedal, T.

    2016-07-01

    We report the structural, electronic, and magnetic study of Cr-doped Sb2Te3 thin films grown by a two-step deposition process using molecular-beam epitaxy (MBE). The samples were investigated using a variety of complementary techniques, namely, x-ray diffraction (XRD), atomic force microscopy, SQUID magnetometry, magneto-transport, and polarized neutron reflectometry (PNR). It is found that the samples retain good crystalline order up to a doping level of x=0.42 (in Cr x Sb2-x Te3), above which degradation of the crystal structure is observed by XRD. Fits to the recorded XRD spectra indicate a general reduction in the c-axis lattice parameter as a function of doping, consistent with substitutional doping with an ion of smaller ionic radius. The samples show soft ferromagnetic behavior with the easy axis of magnetization being out-of-plane. The saturation magnetization is dependent on the doping level, and reaches from ˜2 μ_\\text{B} to almost 3 μ_\\text{B} per Cr ion. The transition temperature (T{c}) depends strongly on the Cr concentration and is found to increase with doping concentration. For the highest achievable doping level for phase-pure films of x=0.42 , a T{c} of 125 K was determined. Electric transport measurements find surface-dominated transport below ˜10 K. The magnetic properties extracted from anomalous Hall effect data are in excellent agreement with the magnetometry data. PNR studies indicate a uniform magnetization profile throughout the film, with no indication of enhanced magnetic order towards the sample surface.

  15. Electron beam fabrication and characterization of high- resolution magnetic force microscopy tips

    NARCIS (Netherlands)

    Rührig, M.; Porthun, S.; Lodder, J.C.; McVitie, S.; Heyderman, L.J.; Johnston, A.B.; Chapman, J.N.

    1996-01-01

    The stray field, magnetic microstructure, and switching behavior of high‐resolution electron beam fabricated thin film tips for magnetic force microscopy (MFM) are investigated with different imaging modes in a transmission electron microscope (TEM). As the tiny smooth carbon needles covered with a

  16. The effects of magnetic annealing of transition metal alloys deduced from ab initio electronic structure calculations

    Energy Technology Data Exchange (ETDEWEB)

    Razee, S.S.A.; Staunton, J.B. [Department of Physics, University of Warwick, Coventry (United Kingdom); Ginatempo, B.; Bruno, E. [Dipartimento di Fisica and Unita INFM, Universita di Messina, Messina (Italy); Pinski, F.J. [Department of Physics, University of Cincinnati, OH (United States)

    2001-09-24

    A theory is presented for describing the effects of annealing magnetic alloys in magnetic fields. It has an ab initio spin-polarized relativistic Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) electronic structure basis and uses the framework of concentration waves. Alloys which would otherwise be soft magnets are found experimentally to develop directional chemical order and significant uniaxial anisotropy when annealed in magnetic fields. Our approach is able to provide a quantitative description of these effects together with the underlying electronic mechanisms. We describe applications to the soft magnetic alloys permalloy and FeCo. (author)

  17. Magnetic properties and electronic structure of Mn-Ni-Ga magnetic shape memory alloys.

    Science.gov (United States)

    D'Souza, Sunil Wilfred; Roy, Tufan; Barman, Sudipta Roy; Chakrabarti, Aparna

    2014-12-17

    Influence of disorder, antisite defects, martensite transition and compositional variation on the magnetic properties and electronic structure of Mn(2)NiGa and Mn(1+x)Ni(2-x)Ga magnetic shape memory alloys have been studied by using full potential spin-polarized scalar relativistic Korringa-Kohn-Rostocker (FP-SPRKKR) method. Mn(2)NiGa is ferrimagnetic and its total spin moment increases when disorder in the occupancy of MnNi (Mn atom in Ni position) is considered. The moment further increases when Mn-Ga antisite defect [1] is included in the calculation. A reasonable estimate of TC for Mn(2)NiGa is obtained from the exchange parameters for the disordered structure. Disorder influences the electronic structure of Mn(2)NiGa through overall broadening of the density of states and a decrease in the exchange splitting. Inclusion of antisite defects marginally broaden the minority spin partial DOS (PDOS), while the majority spin PDOS is hardly affected. For Mn(1+x)Ni(2-x)Ga where 1 ⩾ x ⩾ 0, as x decreases, Mn(Mn) moment increases while Mn(Ni) moment decreases in both austenite and martensite phases. For x ⩾ 0.25, the total moment of the martensite phase is smaller compared to the austenite phase, which indicates possible occurrence of inverse magnetocaloric effect. We find that the redistribution of Ni 3d- Mn(Ni) 3d minority spin electron states close to the Fermi level is primarily responsible for the stability of the martensite phase in Mn-Ni-Ga.

  18. Theme of the Workshop on Itinerant-Electron Magnetism, and Spin Fluctuations

    Science.gov (United States)

    Yoshimura, Kazuyoshi

    2017-06-01

    The international workshop on itinerant-electron magnetism was held during September 25-27, 2015 in the seminar house of Graduate School of Science, Kyoto University, Kyoto, Japan. Here, I explain the theme of this workshop, and stress the development of itinerant-electron magnetism in several decades. The workshop was also organized in commemoration of Professor Yoshinori Takahashi’s retirement from University of Hyogo, Japan. Here, I also explain some of his works contributing to the development of itinerant magnetism.

  19. Electron microscopy observations of surface morphologies and particle arrangement behaviors of magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    沈辉; 徐雪青; 王伟

    2003-01-01

    The surface morphology of quasi-periodic stripe-shaped patterns of magnetite fluids was observed in applied perpendicular magnetic fields by means of scanning electron microscopy. The nanoparticles of the magnetite fluids are arranged in oriental quasilinear chains in applied perpendicular magnetic fields as observed using transmission electron microscopy. This arrangement results from particle-particle interactions and particle-carrier liquids interactions, which are eventually controlled by the magnetic fields distribution.

  20. RF current drive by electron cyclotron waves in the presence of magnetic islands

    Energy Technology Data Exchange (ETDEWEB)

    Da Silva Rosa, P.; Giruzzi, G

    1999-11-01

    The influence of the presence of magnetic islands, and the consequent modification of the tokamak magnetic surface topology, on electron current drive is analyzed. To this end, a new 3D Fokker-Planck code has been developed, taking into account the modifications of the magnetic equilibrium topology owing to the presence of the islands. Significant differences between electron cyclotron current drive efficiency with and without island inside the plasma are found, particularly in the case of interaction with locked modes. (authors)

  1. First-principles study on electronic structure, magnetic and dielectric properties of Cr-doped Fe3C

    Institute of Scientific and Technical Information of China (English)

    杨建平; 陈津; 李伟; 韩培德; 郭丽娜

    2016-01-01

    The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe3C, in comparison to those of pure Fe3C and Cr3C. The obtained results show that the thermodynamic stability of Cr- doped Fe3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe3C, Fe11CrC4(g), and Fe11CrC4(s) are respectively 21.36μB/cell, 16.92μB/cell, and 17.62μB/cell, and in Fe11CrC4(g) and Fe11CrC4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe11CrC4(s)>Cr3C>Fe11CrC4(g)>Fe3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.

  2. Effect of Electron Drift Velocity on Whistler Instability in Collisionless Magnetic Reconnection

    Institute of Scientific and Technical Information of China (English)

    WANG De-Yu; HUANG Guang-Li; LU Quan-Ming

    2004-01-01

    The whistler instability is studied under the condition that the electron and ion velocities can be described in a bi-Maxwellian distribution with a field-aligned electron outflow drift velocity. It is found that the electron outflow drift velocity might obviously make the threshold condition of whistler instability decrease when this velocity is parallel to the magnetic field, whereas the electron outflow drift velocity might increase the threshold condition when this velocity is anti-parallel to the magnetic field in collisionless magnetic reconnection.

  3. A nonperturbative calculation of the electron's magnetic moment

    Science.gov (United States)

    Brodsky, S. J.; Franke, V. A.; Hiller, J. R.; McCartor, G.; Paston, S. A.; Prokhvatilov, E. V.

    2004-12-01

    In principle, the complete spectrum and bound-state wave functions of a quantum field theory can be determined by finding the eigenvalues and eigensolutions of its light-cone Hamiltonian. One of the challenges in obtaining nonperturbative solutions for gauge theories such as QCD using light-cone Hamiltonian methods is to renormalize the theory while preserving Lorentz symmetries and gauge invariance. For example, the truncation of the light-cone Fock space leads to uncompensated ultraviolet divergences. We present two methods for consistently regularizing light-cone-quantized gauge theories in Feynman and light-cone gauges: (1) the introduction of a spectrum of Pauli-Villars fields which produces a finite theory while preserving Lorentz invariance; (2) the augmentation of the gauge-theory Lagrangian with higher derivatives. In the latter case, which is applicable to light-cone gauge ( A=0), the A component of the gauge field is maintained as an independent degree of freedom rather than a constraint. Finite-mass Pauli-Villars regulators can also be used to compensate for neglected higher Fock states. As a test case, we apply these regularization procedures to an approximate nonperturbative computation of the anomalous magnetic moment of the electron in QED as a first attempt to meet Feynman's famous challenge.

  4. Electron magnetic resonance of gadolinium-doped calcium fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Biasi, R.S. de, E-mail: rsbiasi@ime.eb.br [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil); Grillo, M.L.N., E-mail: mluciag@uerj.br [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

    2012-06-15

    Electron magnetic resonance (EMR) spectra of gadolinium-doped calcium fluoride have been studied at room temperature for Gd concentrations between 0.01 and 2.00 mol%. Gd{sup 3+} ions in sites with two different symmetries were observed. One of the sites, with cubic symmetry, is unstable at room temperature and decays with a time constant of 2.2 day{sup -1}. The other site, with tetragonal symmetry, is stable and is attributed to Gd{sup 3+} ions in substitutional sites next to a charge-compensating F{sup -} interstitial ion. The linewidth and intensity of the EMR spectrum with tetragonal symmetry increase with increasing Gd concentration. A theoretical calculation based on the concentration dependence of the EMR linewidth yields an effective range of the exchange interaction between Gd{sup 3+} ions in CaF{sub 2} of 0.774 nm, of the same order as that of Gd{sup 3+} ions in other cubic ionic compounds.

  5. Quantitative evaluation of magnetic flux density in a magnetic recording head and pseudo soft underlayer by electron holography.

    Science.gov (United States)

    Xia, Weixing; Hirata, Kei; Yanagisawa, Keiichi; Ishida, Yoichi; Kasai, Hiroto; Yanagiuchi, Katsuaki; Shindo, Daisuke; Tonomura, Akira

    2010-01-01

    The magnetic interaction between the pole tip of a single-pole head and a pseudo soft underlayer in perpendicular magnetic recording was observed by electron holography. The magnetic flux density inside the soft underlayer was quantitatively evaluated. The distribution of magnetic flux density was calculated using the finite element method, and the influences of the modulation of the reference wave and stray fields were investigated by comparison with experimental results. The flux density observed was found to be underestimated due to the modulation of the phase shift in reference wave. The magnetic flux measured experimentally was larger than that inside the specimen because of the relatively large stray fields above and below the specimen in the direction of the electron beam.

  6. From the Gyration of Electrons to Cosmic Magnetic Fields

    Science.gov (United States)

    Wang, Xia-Wei

    2010-01-01

    Employing Bohr's quantum theory, the author deduces three limits, which correspond to the magnetic fields of white dwarfs, neutron stars and the strongest in the universe. The author discusses the possible origins of magnetic fields due to collapse of stars, which produces a magnetic field of 10[superscript 8] T. Although the complete analysis…

  7. Gamma-ray and neutron diffraction studies of CoF2: magnetostriction, electron density and magnetic moments.

    Science.gov (United States)

    Jauch, W; Reehuis, M; Schultz, A J

    2004-01-01

    Accurate structure factors up to sin theta/lambda = 1.6 A(-1) have been measured with 316.5 keV gamma-rays from CoF(2), both at room temperature and in the antiferromagnetic state at 10 K. The same crystal was used to collect extended time-of-flight neutron diffraction data in the two magnetic states, which allowed an accurate determination of the fluorine positional parameter. For room temperature, the standard structural parameters are reported. At 10 K, a complete charge-density study has been carried out. The total number of 3d electrons on Co is found to be 6.95 (3). The experimental populations of the d orbitals agree with expectation from crystal field theory. The fluorine valence region exhibits a strong dipolar deformation. Electronic properties at the bond critical points and integrated atomic properties are derived from the static model electron density, revealing the Co-F interactions as purely ionic. On magnetic ordering, a shift of the fluorine ions of 1.5 (4) x 10(-3) A is found which confirms a prediction from theory of optical birefringence. The effect of magnetostriction on the distortion of the ligand coordination octahedra is compared for the late members of the 3d transition-metal difluorides. From neutron powder diffraction, an ordered magnetic moment of 2.60 (4) mu(B) per cobalt ion is found. Despite the strong deviation from the ideal spin value of 3 mu(B), there is still an appreciable orbital contribution to the local magnetic moment.

  8. The Relationship Between Magnet Designation, Electronic Health Record Adoption, and Medicare Meaningful Use Payments.

    Science.gov (United States)

    Lippincott, Christine; Foronda, Cynthia; Zdanowicz, Martin; McCabe, Brian E; Ambrosia, Todd

    2017-03-02

    The objective of this study was to examine the relationship between nursing excellence and electronic health record adoption. Of 6582 US hospitals, 4939 were eligible for the Medicare Electronic Health Record Incentive Program, and 6419 were eligible for evaluation on the HIMSS Analytics Electronic Medical Record Adoption Model. Of 399 Magnet hospitals, 330 were eligible for the Medicare Electronic Health Record Incentive Program, and 393 were eligible for evaluation in the HIMSS Analytics Electronic Medical Record Adoption Model. Meaningful use attestation was defined as receipt of a Medicare Electronic Health Record Incentive Program payment. The adoption electronic health record was defined as Level 6 and/or 7 on the HIMSS Analytics Electronic Medical Record Adoption Model. Logistic regression showed that Magnet-designated hospitals were more likely attest to Meaningful Use than non-Magnet hospitals (odds ratio = 3.58, P < .001) and were more likely to adopt electronic health records than non-Magnet hospitals (Level 6 only: odds ratio = 3.68, P < .001; Level 6 or 7: odds ratio = 4.02, P < .001). This study suggested a positive relationship between Magnet status and electronic health record use, which involves earning financial incentives for successful adoption. Continued investigation is needed to examine the relationships between the quality of nursing care, electronic health record usage, financial implications, and patient outcomes.

  9. The electronic and magnetic properties of (Mn,C)-codoped ZnO diluted magnetic semiconductor

    Institute of Scientific and Technical Information of China (English)

    Zhao Long; Lu Peng-Fei; Yu Zhong-Yuan; Ma Shi-Jia; Ding Lu; Liu Jian-Tao

    2012-01-01

    The electronic and magnetic properties of (Mn,C)-codoped ZnO are studied in the Perdew-Burke-Ernzerhof form of generalized gradient approximation of the density functional theory.By investigating five geometrical configurations,we find that Mn doped ZnO exhibits anti-ferromagnetic or spin-glass behaviour,and there are no carriers to mediate the long range ferromagnetic (FM) interaction without acceptor co-doping.We observe that the FM interaction for (Mn,C)-codoped ZnO is due to the hybridization between C 2p and Mn 3d states,which is strong enough to lead to hole-mediated ferromagnetism at room temperature.Meanwhile,we demonstrate that ZnO co-doped with Mn and C has a stable FM ground state and show that the (Mn,C)-codoped ZnO is FM semiconductor with super-high Curie temperature (TC = 5475 K).These results are conducive to the design of dilute magnetic semiconductors with codopants for spintronics applications.

  10. Probing the spinor nature of electronic states in nanosize non-collinear magnets

    Science.gov (United States)

    Fischer, Jeison A.; Sandratskii, Leonid M.; Phark, Soo-Hyon; Ouazi, Safia; Pasa, André A.; Sander, Dirk; Parkin, Stuart S. P.

    2016-01-01

    Non-collinear magnetization textures provide a route to novel device concepts in spintronics. These applications require laterally confined non-collinear magnets (NCM). A crucial aspect for potential applications is how the spatial proximity between the NCM and vacuum or another material impacts the magnetization texture on the nanoscale. We focus on a prototypical exchange-driven NCM given by the helical spin order of bilayer Fe on Cu(111). Spin-polarized scanning tunnelling spectroscopy and density functional theory reveal a nanosize- and proximity-driven modification of the electronic and magnetic structure of the NCM in interfacial contact with a ferromagnet or with vacuum. An intriguing non-collinearity between the local magnetization in the sample and the electronic magnetization probed above its surface results. It is a direct consequence of the spinor nature of electronic states in NCM. Our findings provide a possible route for advanced control of nanoscale spin textures by confinement. PMID:27721384

  11. Medical high-resolution image sharing and electronic whiteboard system: A pure-web-based system for accessing and discussing lossless original images in telemedicine.

    Science.gov (United States)

    Qiao, Liang; Li, Ying; Chen, Xin; Yang, Sheng; Gao, Peng; Liu, Hongjun; Feng, Zhengquan; Nian, Yongjian; Qiu, Mingguo

    2015-09-01

    There are various medical image sharing and electronic whiteboard systems available for diagnosis and discussion purposes. However, most of these systems ask clients to install special software tools or web plug-ins to support whiteboard discussion, special medical image format, and customized decoding algorithm of data transmission of HRIs (high-resolution images). This limits the accessibility of the software running on different devices and operating systems. In this paper, we propose a solution based on pure web pages for medical HRIs lossless sharing and e-whiteboard discussion, and have set up a medical HRI sharing and e-whiteboard system, which has four-layered design: (1) HRIs access layer: we improved an tile-pyramid model named unbalanced ratio pyramid structure (URPS), to rapidly share lossless HRIs and to adapt to the reading habits of users; (2) format conversion layer: we designed a format conversion engine (FCE) on server side to real time convert and cache DICOM tiles which clients requesting with window-level parameters, to make browsers compatible and keep response efficiency to server-client; (3) business logic layer: we built a XML behavior relationship storage structure to store and share users' behavior, to keep real time co-browsing and discussion between clients; (4) web-user-interface layer: AJAX technology and Raphael toolkit were used to combine HTML and JavaScript to build client RIA (rich Internet application), to meet clients' desktop-like interaction on any pure webpage. This system can be used to quickly browse lossless HRIs, and support discussing and co-browsing smoothly on any web browser in a diversified network environment. The proposal methods can provide a way to share HRIs safely, and may be used in the field of regional health, telemedicine and remote education at a low cost.

  12. The expected imprint of flux rope geometry on suprathermal electrons in magnetic clouds

    Directory of Open Access Journals (Sweden)

    M. J. Owens

    2009-10-01

    Full Text Available Magnetic clouds are a subset of interplanetary coronal mass ejections characterized by a smooth rotation in the magnetic field direction, which is interpreted as a signature of a magnetic flux rope. Suprathermal electron observations indicate that one or both ends of a magnetic cloud typically remain connected to the Sun as it moves out through the heliosphere. With distance from the axis of the flux rope, out toward its edge, the magnetic field winds more tightly about the axis and electrons must traverse longer magnetic field lines to reach the same heliocentric distance. This increased time of flight allows greater pitch-angle scattering to occur, meaning suprathermal electron pitch-angle distributions should be systematically broader at the edges of the flux rope than at the axis. We model this effect with an analytical magnetic flux rope model and a numerical scheme for suprathermal electron pitch-angle scattering and find that the signature of a magnetic flux rope should be observable with the typical pitch-angle resolution of suprathermal electron data provided ACE's SWEPAM instrument. Evidence of this signature in the observations, however, is weak, possibly because reconnection of magnetic fields within the flux rope acts to intermix flux tubes.

  13. Fundamental Principles of the Physics of Magnetism and the Problem of Localized and Itinerant Electronic States

    CERN Document Server

    Kuzemsky, A L

    2000-01-01

    Some of the remarkably and recently observed features of complex transition metal and rare-earth metal oxides, compounds and alloys concerning mainly of their magnetic behaviour are reviewed in the context of slow neutron scattering. These includes variety of the new class of materials with unusual properties: high Tc superconductors, heavy fermion compounds, perovskite manganites, magnetic d and f transition metals, diluted magnetic semiconductors, etc. Contrary to simple metals where the fundamentals very well known and the electrons can be represented in a way such that they weakly interact with each other, in these materials the electrons interact strongly and moreover their spectra are complex, i.e. have many branches, etc. The behaviour and the true nature of the electronic states are of central importance to the understanding of unusual transport and magnetic properties of this class of materials. We argue that interesting electronic and magnetic properties of these substances are intimately related wi...

  14. Electronic structures and magnetic/optical properties of metal phthalocyanine complexes

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shintaro; Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.jp; Oku, Takeo [Department of Materials Science, The University of Shiga Prefecture. 2500 Hassaka, Hikone, Shiga 522-8533 (Japan)

    2016-02-01

    Electronic structures and magnetic / optical properties of metal phthalocyanine complexes were studied by quantum calculations using density functional theory. Effects of central metal and expansion of π orbital on aromatic ring as conjugation system on the electronic structures, magnetic, optical properties and vibration modes of infrared and Raman spectra of metal phthalocyanines were investigated. Electron and charge density distribution and energy levels near frontier orbital and excited states were influenced by the deformed structures varied with central metal and charge. The magnetic parameters of chemical shifts in {sup 13}C-nuclear magnetic resonance ({sup 13}C-NMR), principle g-tensor, A-tensor, V-tensor of electric field gradient and asymmetry parameters derived from the deformed structures with magnetic interaction of nuclear quadruple interaction based on electron and charge density distribution with a bias of charge near ligand under crystal field.

  15. Classical understanding of electron vortex beams in a uniform magnetic field

    Science.gov (United States)

    Han, Yeong Deok; Choi, Taeseung

    2017-04-01

    Recently, interesting observations on electron vortex beams have been made. We propose a classical model that shows vortex-like motion due to suitably-synchronized motion of each electron's cyclotron motion in a uniform magnetic field. It is shown that some basic features of electron vortex beams in a uniform magnetic field, such as azimuthal currents, the relation between energy and kinetic angular momentum, and the parallel-axis theorem are understandable by using this classical model. We also show that the time-dependence of kinetic angular momentum of electron vortex beams could be understood as an effect of a specific nonuniform distribution of classical electrons.

  16. Electron cyclotron resonance heating by magnetic filter field in a negative hydrogen ion source

    Energy Technology Data Exchange (ETDEWEB)

    Kim, June Young, E-mail: beacoolguy@snu.ac.kr; Cho, Won-Hwi; Dang, Jeong-Jeung; Chung, Kyoung-Jae, E-mail: jkjlsh1@snu.ac.kr; Hwang, Y. S. [Department of Nuclear Engineering, Seoul National University, Seoul 151-742 (Korea, Republic of)

    2016-02-15

    The influence of magnetic filter field on plasma properties in the heating region has been investigated in a planar-type inductively coupled radio-frequency (RF) H{sup −} ion source. Besides filtering high energy electrons near the extraction region, the magnetic filter field is clearly observed to increase the electron temperature in the heating region at low pressure discharge. With increasing the operating pressure, enhancement of electron temperature in the heating region is reduced. The possibility of electron cyclotron resonance (ECR) heating in the heating region due to stray magnetic field generated by a filter magnet located at the extraction region is examined. It is found that ECR heating by RF wave field in the discharge region, where the strength of an axial magnetic field is approximately ∼4.8 G, can effectively heat low energy electrons. Depletion of low energy electrons in the electron energy distribution function measured at the heating region supports the occurrence of ECR heating. The present study suggests that addition of axial magnetic field as small as several G by an external electromagnet or permanent magnets can greatly increase the generation of highly ro-vibrationally excited hydrogen molecules in the heating region, thus improving the performance of H{sup −} ion generation in volume-produced negative hydrogen ion sources.

  17. The effect of non-thermal electrons on obliquely propagating electron acoustic waves in a magnetized plasma

    Science.gov (United States)

    Singh, Satyavir; Bharuthram, Ramashwar

    2016-07-01

    Small amplitude electron acoustic solitary waves are studied in a magnetized plasma consisting of hot electrons following Cairn's type non-thermal distribution function and fluid cool electrons, cool ions and an electron beam. Using reductive perturbation technique, the Korteweg-de-Vries-Zakharov-Kuznetsov (KdV-ZK) equation is derived to describe the nonlinear evolution of electron acoustic waves. It is observed that the presence of non-thermal electrons plays an important role in determining the existence region of solitary wave structures. Theoretical results of this work is used to model the electrostatic solitary structures observed by Viking satellite. Detailed investigation of physical parameters such as non-thermality of hot electrons, beam electron velocity and temperature, obliquity on the existence regime of solitons will be discussed.

  18. Role of the electron transfer and magnetic exchange interactions in the magnetic properties of mixed-valence polyoxovanadate complexes.

    Science.gov (United States)

    Calzado, Carmen J; Clemente-Juan, Juan M; Coronado, Eugenio; Gaita-Arino, Alejandro; Suaud, Nicolas

    2008-07-01

    Modeling the properties of high-nuclearity, high-electron-population, mixed-valence (MV) magnetic systems remains one of the open challenges in molecular magnetism. In this work, we analyze the magnetic properties of a series of polyoxovananadate clusters of formula [V 18O 42] (12-) and [V 18O 42] (4-). The first compound is a fully localized spin cluster that contains 18 unpaired electrons located at the metal sites, while the second one is a MV cluster with 10 unpaired electrons largely delocalized over the 18 metal sites. A theoretical model that takes into account the interplay between electron transfer and magnetic exchange interactions is developed to explain the unexpected enhancement of the antiferromagnetic coupling when the number of unpaired electrons is reduced from 18 to 10 in these clusters. In the MV area, these systems represent the most complex magnetic clusters studied theoretically so far. Because of the high complexity of the systems, the number of relevant parameters is too large for a conventional model Hamiltonian approach. We therefore perform a theoretical study that combines ab initio calculations with the model Hamiltonian. In this way, we use ab initio calculations performed on small fragments of the cluster to lower the degrees of freedom of the parameter set of the model Hamiltonian that operates in the whole MV cluster. This approach shows the usefulness of combining ab initio calculations with model Hamiltonians in order to explore the magnetic properties of large and complex molecular systems, emphasizing the key role played by the electron transfer in these model magnetic materials.

  19. Electron butterfly distributions at particular magnetic latitudes observed during Juno's perijove pass

    Science.gov (United States)

    Ma, Q.; Thorne, R. M.; Li, W.; Zhang, X.-J.; Mauk, B. H.; Paranicas, C.; Haggerty, D. K.; Kurth, W. S.; Connerney, J. E. P.; Bagenal, F.; Bolton, S. J.

    2017-05-01

    We report observations of energetic electron butterfly distributions measured in a narrow range of Jupiter's magnetic latitudes by Juno during perijove 1. The electron butterfly distributions are characterized as clear electron flux peaks at 30-80° pitch angles, compared with the 90°-peaked pitch angle distributions of the trapped electrons. Jupiter Energetic Particle Detector Instrument measurements during the close approach to Jupiter indicate a specific electron population with butterfly distributions formed between the main auroral oval and the radiation belt. The off-90° flux peak is most clearly observed at tens of keV energies and gradually merges toward 90° pitch angle at higher energies. By projecting the observed electron pitch angle distributions along the magnetic field line, we found that the electron butterfly distributions are observed close to their source region. The particular electron distribution is possibly formed by parallel acceleration of electrons through Landau resonance with electrostatic waves.

  20. Calculation of thermal conductivity coefficients of electrons in magnetized dense matter

    CERN Document Server

    Bisnovatyi-Kogan, G S

    2016-01-01

    The solution of Boltzmann equation for plasma in magnetic field, with arbitrarily degenerate electrons and non-degenerate nuclei, is obtained by Chapman-Enskog method. Functions, generalizing Sonin polynomials are used for obtaining an approximate solution. Fully ionized plasma is considered. The tensor of the heat conductivity coefficients in non-quantized magnetic field is calculated. For non-degenerate and strongly degenerate plasma the asymptotic analytic formulas are obtained, which are compared with results of previous authors. The Lorentz approximation, with neglecting of electron-electron encounters, is asymptotically exact for strongly degenerate plasma. For non-degenerate plasma the solution at 3-function approximation for Lorentz gas deviate from the exact solution for about 2.2\\%, at zero magnetic field. We obtain the solution for the heat conductivity tensor for the case of non-degenerate electrons, in presence of a magnetic field, in three polynomial approximation with account of electron-electr...

  1. The Effect of Magnetic Field of Multicusp and Wall Material on Electron Trajectories

    Science.gov (United States)

    Khodadadi Azadboni, Fatemeh; Sedaghatizade, Mahmood

    2010-04-01

    In this paper, the effect of electron confinement with magnetic fields in the multicusp ion source has been investigated. That is, electron confinement with magnetic fields plays a very important role for the generation of negative ions at plasma. Three-dimensional spatial distributions of electrons production are obtained for a multicusp ion source. The electron confinement of magnetic fields from various surface materials (such as Al2O3, Al, Au, Cu, w and stainless-steel) have been compared in a multicusp plasma source. The electron confinement effect becomes stronger with increasing N (the number of rows of permanent magnets) and using Al for plasma chamber wall material. The results of investigations have demonstrated good correspondence with experimental data, and therefore the adequacy of the developed approach and the possibility to build more effective source on this basis.

  2. THE MECHANISMS OF ELECTRON ACCELERATION DURING MULTIPLE X LINE MAGNETIC RECONNECTION WITH A GUIDE FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huanyu; Lu, Quanming; Huang, Can; Wang, Shui, E-mail: qmlu@ustc.edu.cn [CAS Key Lab of Geospace Environment, Department of Geophysics and Planetary Science, University of Science and Technology of China, Hefei 230026 (China)

    2016-04-20

    The interactions between magnetic islands are considered to play an important role in electron acceleration during magnetic reconnection. In this paper, two-dimensional particle-in-cell simulations are performed to study electron acceleration during multiple X line reconnection with a guide field. Because the electrons remain almost magnetized, we can analyze the contributions of the parallel electric field, Fermi, and betatron mechanisms to electron acceleration during the evolution of magnetic reconnection through comparison with a guide-center theory. The results show that with the magnetic reconnection proceeding, two magnetic islands are formed in the simulation domain. Next, the electrons are accelerated by both the parallel electric field in the vicinity of the X lines and the Fermi mechanism due to the contraction of the two magnetic islands. Then, the two magnetic islands begin to merge into one, and, in such a process, the electrons can be accelerated by both the parallel electric field and betatron mechanisms. During the betatron acceleration, the electrons are locally accelerated in the regions where the magnetic field is piled up by the high-speed flow from the X line. At last, when the coalescence of the two islands into one big island finishes, the electrons can be further accelerated by the Fermi mechanism because of the contraction of the big island. With the increase of the guide field, the contributions of the Fermi and betatron mechanisms to electron acceleration become less and less important. When the guide field is sufficiently large, the contributions of the Fermi and betatron mechanisms are almost negligible.

  3. Transmission electron microscopy and ab initio calculations to relate interfacial intermixing and the magnetism of core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chi, C.-C.; Hsiao, C.-H.; Ouyang, Chuenhou, E-mail: houyang@mx.nthu.edu.tw [Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan (China); Skoropata, E.; Lierop, J. van [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

    2015-05-07

    Significant efforts towards understanding bi-magnetic core-shell nanoparticles are underway currently as they provide a pathway towards properties unavailable with single-phased systems. Recently, we have demonstrated that the magnetism of γ-Fe2O3/CoO core-shell nanoparticles, in particular, at high temperatures, originates essentially from an interfacial doped iron-oxide layer that is formed by the migration of Co{sup 2+} from the CoO shell into the surface layers of the γ-Fe2O3 core [Skoropata et al., Phys. Rev. B 89, 024410 (2014)]. To examine directly the nature of the intermixed layer, we have used high-resolution transmission electron microscopy (HRTEM) and first-principles calculations to examine the impact of the core-shell intermixing at the atomic level. By analyzing the HRTEM images and energy dispersive spectra, the level and nature of intermixing was confirmed, mainly as doping of Co into the octahedral site vacancies of γ-Fe2O3. The average Co doping depths for different processing temperatures (150 °C and 235 °C) were 0.56 nm and 0.78 nm (determined to within 5% through simulation), respectively, establishing that the amount of core-shell intermixing can be altered purposefully with an appropriate change in synthesis conditions. Through first-principles calculations, we find that the intermixing phase of γ-Fe2O3 with Co doping is ferromagnetic, with even higher magnetization as compared to that of pure γ-Fe2O3. In addition, we show that Co doping into different octahedral sites can cause different magnetizations. This was reflected in a change in overall nanoparticle magnetization, where we observed a 25% reduction in magnetization for the 235 °C versus the 150 °C sample, despite a thicker intermixed layer.

  4. Small amplitude nonlinear electron acoustic solitary waves in weakly magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Manjistha; Khan, Manoranjan [Department of Instrumentation Science, Jadavpur University, Kolkata-700 032 (India); Ghosh, Samiran [Department of Applied Mathematics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata-700 009 (India); Roychoudhury, Rajkumar [Indian Statistical Institute, Kolkata-700 108 (India); Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar Kolkata-700 064 (India)

    2013-01-15

    Nonlinear propagation of electron acoustic waves in homogeneous, dispersive plasma medium with two temperature electron species is studied in presence of externally applied magnetic field. The linear dispersion relation is found to be modified by the externally applied magnetic field. Lagrangian transformation technique is applied to carry out nonlinear analysis. For small amplitude limit, a modified KdV equation is obtained, the modification arising due to presence of magnetic field. For weakly magnetized plasma, the modified KdV equation possesses stable solitary solutions with speed and amplitude increasing temporally. The solutions are valid upto some finite time period beyond which the nonlinear wave tends to wave breaking.

  5. Measurement of magnetic fields produced by a "magnetic deflector" for the removal of electron contamination in radiotherapy.

    Science.gov (United States)

    Damrongkijudom, N; Oborn, B; Butson, M; Rosenfeld, A

    2006-12-01

    Electron contamination generated from interactions of x-rays with components in a medical linear accelerator's head can increase damage to skin and subcutaneous tissue during radiotherapy through increased dose deposition. Skin and subcutaneous dose from high energy x-rays can be reduced using magnetic fields to sweep the electron contamination away from the radiation treatment field. This work is aimed at investigating the magnetic fields generated by an improved magnetic deflector which utilizes Nd2Fe14B magnets. Magnetic field strengths generated by the deflector have been simulated using Vizimag 3.0 magnetic modelling software. The improved deflector has a more uniform magnetic field strength than its predecessor and is optimised to easily fit on a clinical linear accelerator. Experimental measurements of the magnetic field strengths produced have also been performed for comparison. Results show a relatively good match to Vizimag modelling in the central regions of the deflector. Reductions of skin and subcutaneous dose up to 34% of original values were seen for a 20 x 20 cm2 field at 6MV x-ray energy.

  6. Non-Equilibrium Green's Function Calculation for Electron Transport through Magnetic Tunnel Junction

    Directory of Open Access Journals (Sweden)

    Sara Nobakht

    2014-06-01

    Full Text Available In this paper non-equilibrium Green's function method –dependent electron transport through non magnetic layer (insulator has been studied in one dimension .electron transport in multi-layer (magnetic/non magnetic/ magneticlayers is studied as quantum .the result show increasing the binding strength of the electrical insulator transition probability density case , the electron density , broad levels of disruption increases. Broad band connection increases the levels of disruption to electrical insulation and show non- conductive insulating state to semiconductor stat and even conductor

  7. Electron beam guiding by external magnetic fields in imploded fuel plasma

    Science.gov (United States)

    Johzaki, T.; Sentoku, Y.; Nagatomo, H.; Sunahara, A.; Sakagami, H.; Fujioka, S.; Shiraga, H.; Endo, T.; FIREX project Group

    2016-05-01

    For enhancing the core heating efficiency in fast ignition laser fusion, we proposed the fast electron beam by externally-applied the kilo-tesla (kT) class longitudinal magnetic field. We evaluated the imploded core and the magnetic field profiles formed through the implosion dynamics by resistive MHD radiation hydro code. Using those profiles, the guiding effect was evaluated by fast electron transport simulations, which shows that in addition to the feasible field configuration (moderate mirror ratio), the kT-class magnetic field is required at the fast electron generation point. In this case, the significant enhancement in heating efficiency is expected.

  8. Electronic Structure Magnetic Properties and Optical Properties of Co-doped AlN from First Principles

    Institute of Scientific and Technical Information of China (English)

    ZHAO Long; LU Peng-Fei; YU Zhong-Yuan; GUO Xiao-Tao; YE Han; YUAN Gui-Fang; SHEN Yue; LIU Yu-Min

    2011-01-01

    The electronic structure, magnetic properties, and optical properties of Co-doped AlN are investigated based upon the Perdew-Burke-Ernzerhof form of generalized gradient approximation within the density functional theory. The band gaps narrowing of Al1-xCoxN are found with the increase of Co concentrations. The analyses of the band structures and density of states show that Al1-xCoxN alloys exhibit a half-metallic character. Moreover, we have succeeded in demonstrating that Co doped AlN system in x = 0.125 is always antiferromagnetic, which is in good agreement with the experimental results. Besides, it is shown that the insertion of Co atom leads to redshift of the optical absorption edge.Finally, the optical constants of pure AlN and Al1-xCoxN alloy, such as loss function, refractive index and reflectivity,are discussed.

  9. ELECTRON ACCELERATION BY CASCADING RECONNECTION IN THE SOLAR CORONA. I. MAGNETIC GRADIENT AND CURVATURE DRIFT EFFECTS

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, X.; Büchner, J.; Bárta, M. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Gan, W.; Liu, S. [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, 210008 (China)

    2015-12-10

    We investigate the electron acceleration by magnetic gradient and curvature drift effects in cascading magnetic reconnection of a coronal current sheet via a test particle method in the framework of the guiding center approximation. After several Alfvén transit times, most of the electrons injected at the current sheet are still trapped in the magnetic islands. A small fraction of the injected electrons precipitate into the chromosphere. The acceleration of trapped electrons is dominated by the magnetic curvature drifts, which change the parallel momentum of the electron, and appears to be more efficient than the acceleration of precipitating electrons, which is dominated by the perpendicular momentum change caused by the magnetic gradient drifts. With the resulting trapped energetic electron distribution, the corresponding hard X-ray (HXR) radiation spectra are calculated using an optically thin Bremsstrahlung model. Trapped electrons may explain flare loop top HXR emission as well as the observed bright spots along current sheets trailing coronal mass ejections. The asymmetry of precipitating electrons with respect to the polarity inversion line may contribute to the observed asymmetry of footpoint emission.

  10. Simultaneous electronic and the magnetic excitation of a ferromagnet by intense THz pulses

    CERN Document Server

    Shalaby, Mostafa; Hauri, Christoph P

    2015-01-01

    The speed of magnetization reversal is a key feature in magnetic data storage. Magnetic fields from intense THz pulses have been recently shown to induce small magnetization dynamics in Cobalt thin film on the sub-picosecond time scale. Here, we show that at higher field intensities, the THz electric field starts playing a role, strongly changing the dielectric properties of the cobalt thin film. Both the electronic and magnetic responses are found to occur simultaneously, with the electric field response persistent on a time scale orders of magnitude longer than the THz stimulus

  11. Two dimensional electron gas confined over a spherical surface: Magnetic moment

    Energy Technology Data Exchange (ETDEWEB)

    Hernando, A; Crespo, P [Instituto de Magnetismo Aplicado, UCM-CSIC-ADIF, Las Rozas. P. O. Box 155, Madrid 28230 (Spain) and Dpto. Fisica de Materiales, Universidad Complutense (Spain); Garcia, M A, E-mail: antonio.hernando@adif.es [Instituto de Ceramica y Vidrio, CSIC c/Kelsen, 5 Madrid 28049 (Spain)

    2011-04-01

    Magnetism of capped nanoparticles, NPs, of non-magnetic substances as Au and ZnO is briefly reviewed. The source of the magnetization is discussed on the light of recent X-ray magnetic circular dichroism experiments. As magnetic dichroism analysis has pointed out impurity atoms bonded to the surface act as donor or acceptor of electrons that occupy the surface states. It is proposed that mesoscopic collective orbital magnetic moments induced at the surface states can account for the experimental magnetism characteristic of these nanoparticles. The total magnetic moment of the surface originated at the unfilled Fermi level can reach values as large as 10{sup 2} or 10{sup 3} Bohr magnetons.

  12. Effects of interfacial Fe electronic structures on magnetic and electronic transport properties in oxide/NiFe/oxide heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qianqian; Chen, Xi; Zhang, Jing-Yan [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yang, Meiyin [SKLSM, Institute of Semiconductors, CAS, P.O. Box 912, Beijing 100083 (China); Li, Xu-Jing; Jiang, Shao-Long; Liu, Yi-Wei; Cao, Yi [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Wu, Zheng-Long [Analytical and Testing Center, Beijing Normal University, Beijing 100875 (China); Feng, Chun [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Ding, Lei [School of Materials and Chemical Engineering, Hainan University, Haikou 570228 (China); Yu, Guang-Hua, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-09-15

    Highlights: • The magnetic and transport properties of oxide/NiFe/oxide films were studied. • The oxide (SiO{sub 2}, MgO and HfO{sub 2}) has different elemental electronegativity. • Redox reaction at different NiFe/oxide interface is dependent on the oxide layer. • Different interfacial electronic structures shown by XPS influence the properties. - Abstract: We report that the magnetic and electronic transport properties in oxide/NiFe(2 nm)/oxide film (oxide = SiO{sub 2}, MgO or HfO{sub 2}) are strongly influenced by the electronic structure of NiFe/oxide interface. Magnetic measurements show that there exist magnetic dead layers in the SiO{sub 2} sandwiched film and MgO sandwiched film, whereas there is no magnetic dead layer in the HfO{sub 2} sandwiched film. Furthermore, in the ultrathin SiO{sub 2} sandwiched film no magnetoresistance (MR) is detected, while in the ultrathin MgO sandwiched film and HfO{sub 2} sandwiched film the MR ratios reach 0.35% and 0.88%, respectively. The investigation by X-ray photoelectron spectroscopy reveals that the distinct interfacial redox reactions, which are dependent on the oxide layers, lead to the variation of magnetic and transport properties in different oxide/NiFe/oxide heterostructures.

  13. Electronic structures, magnetic properties, half-metallicity and optical properties of the zincblende Zn1-xMoxS

    Science.gov (United States)

    Yin, Zhu-Hua; Zhang, Jian-Min; Xu, Ke-Wei

    2016-03-01

    The electronic structures, magnetic properties, half-metallicity and optical properties of Zn1-x Mox S (x=0.00, 0.25, 0.50, 0.75, 1.00) are studied by spin-polarized first-principles calculation. Excepting the Zn0.5 Mo0.5 S system with a tetragonal structure, the other systems Zn1-x Mox S (x=0.00, 0.25, 0.75, 1.00) are all in the cubic structure. The lattice constants (volumes) of the Mo doped systems are larger than those of the pure ZnS due to the atomic radius of 2.01 Å for Mo atom larger than that of 1.53 Å for Zn atom. Although pure ZnS is a nonmagnetic semiconductor with a wide band gap of 3.12 eV, due to incompletely filled Mo-4d orbital both the moderate Mo doped systems Zn0.5 Mo0.5 S and Zn0.25 Mo0.75 S are magnetic metal, especially the less Mo doped system Zn0.75 Mo0.25 S and the completely Mo doped system MoS are magnetic half-metal. For Zn0.75 Mo0.25 S system with a magnetic half-metal character as one example, the conducted spin-up channel is only contributed by the threefold degenerate t2g (dxy, dyz, dzx) states due to the tetrahedral crystal field of the S atoms pushing the spin-up channel of the double degenerate eg (dz2, dx2 -y2) states down below the Fermi level EF. Mo doping not only influences the shape of the original broad absorption peak ranging from 2.5 to 20 eV of pure ZnS, but also leads to two new narrow absorption peaks appeared in the ranges from 0 to 3 eV and from 33 to 43 eV. Moreover, their maximum absorption rate and the corresponding energy increase with increasing Mo content. These results are very useful for Zn1-x Mox S to be applied in optical detectors and spintronics devices.

  14. A comparative study on geometries, stabilities, and electronic properties between bimetallic AgnX (X=Au, Cu; n=1-8) and pure silver clusters

    Institute of Scientific and Technical Information of China (English)

    Ding Li-Ping; Kuang Xiao-Yu; Shao Peng; Zhao Ya-Ru; Li Yah-Fang

    2012-01-01

    Using the meta-generalized gradient approximation (meta-GGA) exchange correlation TPSS functional,the geometric structures,the relative stabilities,and the electronic properties of bimetallic AgnX (X=Au,Cu; n=l-8) clusters are systematically investigated and compared with those of pure silver clusters.The optimized structures show that the transition point from preferentially planar to three-dimensional structure occurs at n =6 for the AgnAu clusters,and at n =5 for AgnCu clusters.For different-sized AgnX clusters,one X (X=Au or Cu) atom substituted Agn+1 structure is a dominant growth pattern.The calculated fragmentation energies,second-order differences in energies,and the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps show interesting odd-even oscillation behaviours,indicating that Ag2,4,6,8 and Ag1,3,5,7X (X=Au,Cu) clusters keep high stabilities in comparison with their neighbouring clusters.The natural population analysis reveals that the charges transfer from the Agn host to the impurity atom except for the Ag2Cu cluster.Moreover,vertical ionization potential (VIP),vertical electronic affinity (VEA),and chemical hardness (η) are discussed and compared in depth.The same odd-even oscillations are found for the VIP and ηof the AgnX (X=Au,Cu; n=1-8) clusters.

  15. Investigation of magnetic domains in Ni Mn Ga alloys with a scanning electron microscope

    Science.gov (United States)

    Ge, Y.; Heczko, O.; Söderberg, O.; Hannula, S.-P.; Lindroos, V. K.

    2005-10-01

    The magnetic domains of martensite have been investigated with a scanning electron microscope in three Ni-Mn-Ga alloys with five-layered, seven-layered and non-layered (T) martensite structure. Type I magnetic contrast provides an overview of the domain pattern. This contrast arises from the stray field of the specimen and it is observed in a secondary-electron image. The type II magnetic contrast of a backscattered electron image gives the detailed magnetic microstructure together with the crystal morphology. A stripe domain pattern is formed in all the alloys when there is one dominant martensite variant in the sample. The second minor variant might be distorted due to interaction with the magnetic domain structure of the major variant. The mechanism of the deformation is not entirely clear and a tentative explanation for this deformation is suggested.

  16. Magnetism and the low-energy electronic structure of Mott insulators K{sub 2}CoF{sub 4} and SrMnO{sub 3} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Nalecz, D.M., E-mail: sfnalecz@cyf-kr.edu.pl [Institute of Physics, Pedagogical University, 30-084, Krakow (Poland); Radwanski, R.J. [Institute of Physics, Pedagogical University, 30-084, Krakow (Poland); Center of Solid State Physics, S" n" t Filip 5, 31-150, Krakow (Poland); Ropka, Z. [Center of Solid State Physics, S" n" t Filip 5, 31-150, Krakow (Poland)

    2016-09-01

    For Mott insulators, K{sub 2}CoF{sub 4} and SrMnO{sub 3}, we have calculated, in the purely ionic model, the low-energy electronic structure both in the paramagnetic and magnetic state as well as zero-temperature magnetic moment, its direction and its temperature dependence. We have calculated the octahedral crystal-field strength 10Dq to be 0.98 and 2.25 eV. We claim that for an adequate theoretical description of magnetic properties even small local distortions and the intra-atomic relativistic spin-orbit coupling have to be taken into account. Our studies have revealed a strong interplay of the magnetism, the orbital moment in particular, with the local crystallographic structure. The calculated orbital moment in K{sub 2}CoF{sub 4} is very large, 1.06 μ{sub B}, giving 30% contribution to the total moment - this result points the necessity to “unquench” the orbital magnetism in 3d compounds. We consistently described magnetic and some optical properties of these compounds, containing atoms with incomplete 3d shell, in agreement with their insulating ground state. - Highlights: • The octahedral crystal-field 10Dq amounts to 0.98 and 2.25 eV in K{sub 2}CoF{sub 4} and SrMnO{sub 3}. • The low-energy electronic structures in the magnetic state is displayed. • There is a strong interplay of the magnetism and the local crystal structure. • Temperature dependence of the Mn{sup 4+}- ion magnetic moment has been described. • Relativistic spin-orbit coupling is indispensable for description of 3d magnetism.

  17. Observation of the stray field of thin film magnetic tips using electron holography

    NARCIS (Netherlands)

    Lunedei, E.; Matteucci, G.; Frost, B.G.; Greve, J.

    1996-01-01

    The stray field around thin film ferromagnetic tips employed for magnetic force microscopy has been revealed using electron holography. The experimental phase difference maps are in good agreement with simulations. Quantitative flux measurements of the leakage field are obtained.

  18. Short Range Wake Field Caused by Electron Cloud in Bending Magnet

    CERN Document Server

    Wang, L; Zimmermann, Frank; Ohmi, K

    2001-01-01

    A short-range wake field caused by the electron cloud has previously been studied for a drift space. In a bending magnet, the cloud electrons undergo cyclotron motion with a small radius (10 GHz) in the horizontal plane due to the strong magnetic field of order 1 T. In this report, we study the motion of electrons under the combined influence of a strong magnetic dipole field and the electric field of the beam on the time scale of the bunch length, discuss the short-range wake field caused by the electrons, and simulate the emittance growth. As expected, the wake field in a bending magnet is very different from that in a drift space. The dipole field almost completely suppresses any horizontal coherent motion and rms-size blow up, and it also slows down the instability in the vertical direction.

  19. Electronic and magnetic properties of Fe and Mn doped two dimensional hexagonal germanium sheets

    Energy Technology Data Exchange (ETDEWEB)

    Soni, Himadri R., E-mail: himadri.soni@gmail.com; Jha, Prafulla K., E-mail: himadri.soni@gmail.com [Department of Physics, Maharaja Krishnakumarsinhji Bhavnagar University, Bhavnagar-364001 (India)

    2014-04-24

    Using first principles density functional theory calculations, the present paper reports systematic total energy calculations of the electronic properties such as density of states and magnetic moment of pristine and iron and manganese doped two dimensional hexagonal germanium sheets.

  20. Whistler wave interaction with magnetic islands and electron scale structure formation

    Science.gov (United States)

    Pathak, Neha

    2016-07-01

    The present work aims to investigate the role of whistler waves in facilitating reconnection and to explore relationship between magnetic reconnection and turbulence. The key role of the whistler waves in the formation of coherent structures during their propagation in the pre-existing fully developed chain of magnetic islands has been investigated. For this scenario, the dynamical equation of whistler wave has been derived in the presence of magnetic islands and has been solved semi-analytically as well as numerically. Due to pre-existing magnetic islands, background field gets perturbed and localization of the whistler waves and formation of current sheets of electron scale takes place, contributing to the generation of magnetic turbulence. In this way whistler wave propagating through fully developed magnetic islands may provide a physical mechanism underlying the formation of electron scale current sheet.

  1. Magnetization and susceptibility of a parabolic InAs quantum dot with electron-electron and spin-orbit interactions in the presence of a magnetic field at finite temperature

    Science.gov (United States)

    Kumar, D. Sanjeev; Mukhopadhyay, Soma; Chatterjee, Ashok

    2016-11-01

    The magnetization and susceptibility of a two-electron parabolic quantum dot are studied in the presence of electron-electron and spin-orbit interactions as a function of magnetic field and temperature. The spin-orbit interactions are treated by a unitary transformation and an exactly soluble parabolic interaction model is considered to mimic the electron-electron interaction. The theory is finally applied to an InAs quantum dot. Magnetization and susceptibility are calculated using canonical ensemble approach. Our results show that Temperature has no effect on magnetization and susceptibility in the diamagnetic regime whereas electron-electron interaction reduces them. The temperature however reduces the height of the paramagnetic peak. The Rashba spin-orbit interaction is shown to shift the paramagnetic peak towards higher magnetic fields whereas the Dresselhaus spin-orbit interaction shifts it to the lower magnetic field side. Spin-orbit interaction has no effect on magnetization and susceptibility at larger temperatures.

  2. The influence of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation

    Science.gov (United States)

    Putro, Triswantoro; Endarko

    2016-04-01

    The influences of electron discharge and magnetic field on calcium carbonate (CaCO3) precipitation in water have been successfully investigated. The study used three pairs of magnetic field 0.1 T whilst the electron discharge was generated from television flyback transformer type BW00607 and stainless steel SUS 304 as an electrode. The water sample with an initial condition of 230 mg/L placed in the reactor with flow rate 375 mL/minutes, result showed that the electron discharge can be reduced contain of calcium carbonate the water sample around 17.39% within 2 hours. Meanwhile for the same long period of treatment and flow rate, around 56.69% from initial condition of 520 mg/L of calcium carbonate in the water sample can be achieved by three pairs of magnetic field 0.1 T. When the combination of three pairs of magnetic field 0.1 T and the electron discharge used for treatment, the result showed that the combination of electron discharge and magnetic field methods can be used to precipitate calcium carbonate in the water sample 300 mg/L around 76.66% for 2 hours of treatment. The study then investigated the influence of the polar position of the magnetic field on calcium carbonate precipitation. Two positions of magnetic field were tested namely the system with alternated polar magnetics and the system without inversion of the polar magnetics. The influence of the polar position showed that the percentage reduction in levels of calcium carbonate in the water sample (360 mg/L) is significant different. Result showed that the system without inversion of the polar magnetics is generally lower than the system with alternated polar magnetics, with reduction level at 30.55 and 57.69%, respectively.

  3. Multicusp type electron cyclotron resonance plasma with arrangement of permanent magnets

    Energy Technology Data Exchange (ETDEWEB)

    Amemiya, H.; Maeda, M. [Institute of Physical and Chemical Research, Wako, Saitama (Japan)

    1995-09-01

    ECR (electron cyclotron resonance) plasmas are generated in a multicusp field of 12-pole formed by permanent magnets, where the polarity of the magnetic field at the end sections is reversed to reflect axially drifting electrons as in the mirror field. Furthermore, the radius of multicusp is contracted below the cut-off radius of the waveguide in vacuum. This is effective in increasing the microwave power absorbed in the plasma and the ion density. (author).

  4. The Work Function Associated with Ultra-relativistic Electron Emission from Strongly Magnetized Neutron Star Surface

    Indian Academy of Sciences (India)

    Arpita Ghosh; Somenath Chakrabarty

    2011-09-01

    Following an extremely interesting idea (Schieber 1984), published long ago, the work function associated with the emission of ultra-relativistic electrons from magnetically deformed metallic crystal (mainly iron) at the outer crust of a magnetar is obtained using relativistic version of Thomas–Fermi type model for electron distribution around the nuclei in this region. In the present scenario, surprisingly, the work function becomes anisotropic; the longitudinal part is an increasing function of magnetic field strength, whereas the transverse part diverges.

  5. The Spontaneous Radiation of Electrons in a Plane Wiggler with Inhomogeneous Magnetic Field

    CERN Document Server

    Ayryan, E A; Izmailian, N Sh; Oganesyan, K B

    2016-01-01

    The spectral distribution of spontaneous emission of electrons moving in a plane wiggler with inhomogeneous magnetic field is calculated. We show that electrons do complicated motion consisting of slow(strophotron) and fast(undulator) parts. The equations of motion are averaged over fast undulator part and we obtain equations for connected motion. It is shown, that the account of inhomogenity of the magnetic field leads to appearance of additional peaks in the spectral distribution of spontaneous radiation.

  6. Magnetic microstructure of iron sulfide crystals in magnetotactic bacteria from off-axis electron holography

    Energy Technology Data Exchange (ETDEWEB)

    Kasama, T. [Frontier Research System, Institute of Physical and Chemical Research (Japan); Department of Materials Science and Metallurgy, University of Cambridge (United Kingdom); Posfai, M. [Department of Earth and Environmental Sciences, University of Veszprem (Hungary); Chong, R.K.K. [Department of Materials Science and Metallurgy, University of Cambridge (United Kingdom); Finlayson, A.P. [Department of Materials Science and Metallurgy, University of Cambridge (United Kingdom); Dunin-Borkowski, R.E. [Department of Materials Science and Metallurgy, University of Cambridge (United Kingdom); Frontier Research System, Institute of Physical and Chemical Research (Japan); Frankel, R.B. [Department of Physics, California Polytechnic State University, San Luis Obispo, CA 93407 (United States)]. E-mail: rfrankel@calpoly.edu

    2006-10-01

    Transmission electron microscopy, off-axis electron holography and energy-selected imaging were used to study the crystallography, morphology, and magnetic microstructure of nanoscale greigite (Fe{sub 3}S{sub 4}) magnetosomes in magnetotactic bacteria from a sulfidic habitat. The greigite magnetosomes were organized in chains, but were less ordered than magnetite magnetosomes in other bacteria. Nevertheless, the magnetosomes comprise a permanent magnetic dipole, sufficient for magnetotaxis.

  7. Electron spin relaxation can enhance the performance of a cryptochrome-based magnetic compass sensor

    DEFF Research Database (Denmark)

    Kattnig, Daniel R; Sowa, Jakub K; Solov'yov, Ilia A

    2016-01-01

    The radical pair model of the avian magnetoreceptor relies on long-lived electron spin coherence. Dephasing, resulting from interactions of the spins with their fluctuating environment, is generally assumed to degrade the sensitivity of this compass to the direction of the Earth's magnetic field...... to an Earth-strength magnetic field. Supported by calculations using toy radical pair models, we argue that these enhancements could be consistent with the molecular dynamics and magnetic interactions in avian cryptochromes....

  8. Electron acceleration in the inverse free electron laser with a helical wiggler by axial magnetic field and ion-channel guiding

    Institute of Scientific and Technical Information of China (English)

    Reza Khazaeinezhad; Mahdi Esmaeilzadeh

    2012-01-01

    Electron acceleration in the inverse free electron laser (IFEL) with a helical wiggler in the presence of ion-channel guiding and axial magnetic field is investigated in this article.The effects of tapering wiggler amplitude and axial magnetic field are calculated for the electron acceleration.In free electron lasers,electron beams lose energy through radiation while in IFEL electron beams gain energy from the laser.The equation of electron motion and the equation of energy exchange between a single electron and electromagnetic waves are derived and then solved numerically using the fourth order Runge-Kutta method.The tapering effects of a wiggler magnetic field on electron acceleration are investigated and the results show that the electron acceleration increases in the case of a tapered wiggler magnetic field with a proper taper constant.

  9. Magnetic imaging with a Zernike-type phase plate in a transmission electron microscope

    DEFF Research Database (Denmark)

    Pollard, Shawn; Malac, Marek; Beleggia, Marco

    2013-01-01

    We demonstrate the use of a hole-free phase plate (HFPP) for magnetic imaging in transmission electron microscopy by mapping the domain structure in PrDyFeB samples. The HFPP, a Zernike-like imaging method, allows for detecting magnetic signals in-focus to correlate the sample crystal structure a...

  10. Study of the leakage field of magnetic force microscopy thin-film tips using electron holography

    NARCIS (Netherlands)

    Frost, B.G.; Hulst, van N.F.; Lunedei, E.; Matteucci, G.; Rikkers, E.

    1996-01-01

    Electron holography is applied for the study of the leakage field of thin-film ferromagnetic tips used as probes in magnetic force microscopy. We used commercially available pyramidal tips covered o­n o­ne face with a thin NiCo film, which were then placed in a high external magnetic field directed

  11. Electronic structure and exchange interactions in V-15 magnetic molecules: LDA+U results

    NARCIS (Netherlands)

    Boukhvalov, D.W.; Dobrovitski, V.V.; Katsnelson, M.I.; Lichtenstein, A.I.; Harmon, B.N.; Kogerler, P.

    2004-01-01

    Single-molecule magnets of the type V-15(K-6[V15As6O42(H2O)].8H(2)O) have attracted a great deal of attention recently, being promising systems for studying low-temperature spin-relaxation and quantum-spin tunneling. To understand in detail the internal magnetic and electronic structure, and the

  12. High Energy Electron Confinement in a Magnetic Cusp Configuration

    CERN Document Server

    Park, Jaeyoung; Sieck, Paul E; Offermann, Dustin T; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2014-01-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when beta (plasma pressure/magnetic field pressure) is order of unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high beta a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. The current experiment validates this theoretical conjecture for the first time and represents critical progress toward the Polywell fusion concept which combines a high beta cusp configuration with an electrostatic fusion for a compact, economical, power-producing nuclear fusion reactor.

  13. Quantum well electronic states in a tilted magnetic field

    Science.gov (United States)

    Trallero-Giner, C.; Padilha, J. X.; Lopez-Richard, V.; Marques, G. E.; Castelano, L. K.

    2017-08-01

    We report the energy spectrum and the eigenstates of conduction and uncoupled valence bands of a quantum well under the influence of a tilted magnetic field. In the framework of the envelope approximation, we implement two analytical approaches to obtain the nontrivial solutions of the tilted magnetic field: (a) the Bubnov-Galerkin spectral method and b) the perturbation theory. We discuss the validity of each method for a broad range of magnetic field intensity and orientation as well as quantum well thickness. By estimating the accuracy of the perturbation method, we provide explicit analytical solutions for quantum wells in a tilted magnetic field configuration that can be employed to study several quantitative phenomena.

  14. Nonthermally Dominated Electron Acceleration during Magnetic Reconnection in a Low-beta Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaocan [Los Alamos National Laboratory

    2015-07-21

    This work was motivated by electron acceleration during solar flares. After some introductory remarks on proposed particle acceleration mechanisms and questions needing answers, dynamic simulations and simulation results are presented including energy spectra and the formation of the power law distribution. In summary, magnetic reconnection is highly efficient at converting the free magnetic energy stored in a magnetic shear and accelerating electrons to nonthermal energies in low-β regime. The nonthermal electrons have a dominant fraction and form power-law energy spectra with spectral index p ~ 1 in low-β regime. Electrons are preferentially accelerated along the curvature drift direction along the electric field induced by the reconnection outflow. The results can be applied to explain the observations of electron acceleration during solar flares.

  15. Classical understanding of electron vortex beams in a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Han, Yeong Deok [Department of Computer Science and Engineering, Woosuk University, Wanju, Cheonbuk, 565-701 (Korea, Republic of); Choi, Taeseung, E-mail: tschoi@swu.ac.kr [Division of Applied Food System, College of Natural Science, Seoul Women' s University, Seoul 139-774 (Korea, Republic of); School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-012 (Korea, Republic of)

    2017-04-25

    Recently, interesting observations on electron vortex beams have been made. We propose a classical model that shows vortex-like motion due to suitably-synchronized motion of each electron's cyclotron motion in a uniform magnetic field. It is shown that some basic features of electron vortex beams in a uniform magnetic field, such as azimuthal currents, the relation between energy and kinetic angular momentum, and the parallel-axis theorem are understandable by using this classical model. We also show that the time-dependence of kinetic angular momentum of electron vortex beams could be understood as an effect of a specific nonuniform distribution of classical electrons. - Highlights: • A classical model for electron vortex beams is proposed. • The basic features of azimuthal currents could be understood by using this model. • The kinetic angular momentum of electron vortex beams is intuitively understandable.

  16. Control of Electron Beam Using Strong Magnetic Field for Efficient Core Heating in Fast Ignition

    CERN Document Server

    Johzaki, T; Sentoku, Y; Sunahara, A; Nagatomo, H; Sakagami, H; Mima, K; Fujioka, S; Shiraga, H

    2014-01-01

    For enhancing the core heating efficiency in electron-driven fast ignition, we proposed the fast electron beam guiding using externally applied longitudinal magnetic fields. Based on the PIC simulations for the FIREX-class experiments, we demonstrated the sufficient beam guiding performance in the collisional dense plasma by kT-class external magnetic fields for the case with moderate mirror ratio (~<10 ). Boring of the mirror field was found through the formation of magnetic pipe structure due to the resistive effects, which indicates a possibility of beam guiding in high mirror field for higher laser intensity and/or longer pulse duration.

  17. Spinel ferrite nanocrystals embedded inside ZnO: magnetic, electronic andmagneto-transport properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Shengqiang; Potzger, K.; Xu, Qingyu; Kuepper, K.; Talut, G.; Marko, D.; Mucklich, A.; Helm, M.; Fassbender, J.; Arenholz, E.; Schmidt, H.

    2009-08-21

    In this paper we show that spinel ferrite nanocrystals (NiFe{sub 2}O{sub 4}, and CoFe{sub 2}O{sub 4}) can be texturally embedded inside a ZnO matrix by ion implantation and post-annealing. The two kinds of ferrites show different magnetic properties, e.g. coercivity and magnetization. Anomalous Hall effect and positive magnetoresistance have been observed. Our study suggests a ferrimagnet/semiconductor hybrid system for potential applications in magneto-electronics. This hybrid system can be tuned by selecting different transition metal ions (from Mn to Zn) to obtain various magnetic and electronic properties.

  18. First principle study of structural, electronic and magnetic properties of silicon doped zigzag boron nitride nanoribbon

    Science.gov (United States)

    Bahadur, Amar; Verma, Mohan L.; Mishra, Madhukar

    2015-04-01

    Using first principle calculation, we investigate the structural, electronic and magnetic properties of silicon doped zigzag boron nitride nanoribbon (ZBNNR). Our results show that the shift in position of silicon doping with respect to the ribbon edge causes change in the structural geometry, electronic structure and magnetization of ZBNNR. The band gap of silicon doped ZBNNR is found to become narrower as compared to that of perfect ZBNNR. We find that band gap and magnetic moment of ZBNNR can be tuned by substitutional silicon doping position and doping concentration.

  19. Magnetic field instability in a neutron star driven by electroweak electron-nucleon interaction versus chiral magnetic effect

    CERN Document Server

    Dvornikov, Maxim

    2014-01-01

    We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons ($eN$ interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field provides its growth up to $\\gtrsim 10^{15}\\thinspace\\text{G}$ during a time comparable with the ages of young magnetars $\\sim 10^4\\thinspace\\text{yr}$. The magnetic field instability originates from the parity violation in the $eN$ interaction entering the generalized Dirac equation for right and left massless electrons in an external uniform magnetic field. The averaged electric current given by the solution of the modified Dirac equation contains an extra current for right and left electrons (positrons). Such current includes both a changing chiral imbalance of electrons and the $eN$ potential given by a constant neutron density in NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic helicity which accounts for the $eN$ interaction. By solving this system, we show that ...

  20. A magnetic-free high-resolution parabolic mirror time-of-flight electron energy spectrometer

    Institute of Scientific and Technical Information of China (English)

    张戈; 沈鸿元; 曾瑞荣; 黄呈辉; 林文雄; 黄见洪

    2001-01-01

    The principle and structure of a magnetic-free high-resolution high-efficiency parabolic mirror time-offligght electron energy spectrometer are presented. The electron energy spectrum of Nz in a flight tube is measured using a 105 fs Ti:sappbire laser under different gas pressures.

  1. Probing momentum distributions in magnetic tunnel junctions via hot-electron decay

    NARCIS (Netherlands)

    Jansen, R.; Banerjee, T.; Park, B.G.; Lodder, J.C.

    2007-01-01

    The tunnel momentum distribution in a (magnetic) tunnel junction is probed by analyzing the decay of the hot electrons in the Co metal anode after tunneling, using a three-terminal transistor structure in which the hot-electron attenuation is sensitive to the tunnel momentum distribution. Solid stat

  2. Two-dimensional coupled electron-hole layers in high magnetic fields

    NARCIS (Netherlands)

    Parlangeli, Andrea

    2000-01-01

    In solids, it is nowadays possible to create structures in which electrons are confined into a two-dimensional (2D) plane. The physics of a 2D electron gas (2DEG) has proved to be very rich, in particular in the presence of a transverse magnetic field. The Quantum Hall Effect, i.e. the quantization

  3. Near-Curie magnetic anomaly at the Ni/C interface observed by Electron Holography

    DEFF Research Database (Denmark)

    Ferrari, Loris; Matteucci, Giorgio; Schofield, Marvin A

    2010-01-01

    We analyze with electron holography carried out in a transmission electron microscope the near-Curie behavior of magnetism at the edge of a Nickel thin film coated with Carbon. In-situ experiments with finely controlled variations of the sample temperature reveal an anomaly in the ferromagnetic t...

  4. Is the angular momentum of an electron conserved in a uniform magnetic field?

    Science.gov (United States)

    Greenshields, Colin R; Stamps, Robert L; Franke-Arnold, Sonja; Barnett, Stephen M

    2014-12-12

    We show that an electron moving in a uniform magnetic field possesses a time-varying "diamagnetic" angular momentum. Surprisingly this means that the kinetic angular momentum of the electron may vary with time, despite the rotational symmetry of the system. This apparent violation of angular momentum conservation is resolved by including the angular momentum of the surrounding fields.

  5. Design and performance of a 30 KV electron gun with ten independent cathodes & a magnetic lens.

    Energy Technology Data Exchange (ETDEWEB)

    Rudys, Joseph Matthew; Reed, Kim Warren

    2006-08-01

    Measurements on a 30 kV electron gun with ten independent cathodes, operating in a 6.5 Tesla (T) magnetic field are presented. An earlier paper covered the design of this electron gun [1]. Experimental results are compared to model predictions. Beam current is compared to theoretical space charge limited flow.

  6. Neutrino production of electron-positron pairs at excited Landau levels in a strong magnetic field

    CERN Document Server

    Kuznetsov, A V; Savin, V N

    2014-01-01

    The process of neutrino production of electron positron pairs in a magnetic field of arbitrary strength, where electrons and positrons can be created in the states corresponding to excited Landau levels, is analysed. The mean value of the neutrino energy loss due to the process $\

  7. Thermodynamics of Two-Dimensional Electron Gas in a Magnetic Field

    Directory of Open Access Journals (Sweden)

    V. I. Nizhankovskii

    2011-01-01

    Full Text Available Change of the chemical potential of electrons in a GaAs-AlGa1−As heterojunction was measured in magnetic fields up to 6.5 T at several temperatures from 2.17 to 12.3 K. A thermodynamic equation of state of two-dimensional electron gas well describes the experimental results.

  8. Fast magnetic and turbulent-wave dynamos in electron magnetohydrodynamics

    NARCIS (Netherlands)

    Lakhin, V. P.; Moiseev, S. S.; Schep, T. J.

    2000-01-01

    The influence of inertia on the spontaneous amplification of large-scale perturbations by electron magnetohydrodynamic (EMHD) turbulence is studied in a 2 1/2 -dimensional(2 1/2 -D) model. It is shown that electron inertia results in the modification of ct-like effects, which are due to the helicity

  9. Electronic and magnetic properties of nonmetal atoms doped blue phosphorene: First-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, Huiling; Yang, Hui [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Department of Physics, Jilin University, Changchun 130012 (China); Wang, Hongxia [College of Mathematics, Physics and Information Science, Zhejiang Ocean University, Zhoushan 316000 (China); Du, Xiaobo [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Department of Physics, Jilin University, Changchun 130012 (China); Yan, Yu, E-mail: yanyu@jlu.edu.cn [Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), Department of Physics, Jilin University, Changchun 130012 (China)

    2016-06-15

    Using first-principles calculations, we study the geometrical structure, electronic structure and magnetic properties of substitutionally doped blue phosphorene with a series of nonmetallic atoms, including F, Cl, B, N, C, Si and O. The calculated formation energies and molecular dynamics simulations indicate that F, Cl, B, N, C, Si and O doped blue phosphorene are stable. Moreover, the substitutional doping of F, Cl, B and N cannot induce the magnetism in blue phosphorene due to the saturation or pairing of the valence electron of dopant and its neighboring P atoms. In contrast, ground states of C, Si and O doped blue phosphorene are spin-polarized and the magnetic moments induced by a doping atom are all 1.0 μ{sub B}, which is attributed to the appearance of an unpaired valence electron of C and Si and the formation of a nonbonding 3p electron of a neighboring P atom around O. Furthermore, the magnetic coupling between the moments induced by two C, Si and O are found to be long-range anti-ferromagnetic and the origin of the coupling can be attributed to the p–p hybridization interaction involving polarized electrons. - Highlights: • F, Cl, B, N, C, Si and O doped blue phosphorene are stable. • Substitutional doping of C, Si and O can produce the magnetism in blue phosphorene. • Magnetic coupling between two C, Si and O is long-range anti-ferromagnetic.

  10. Dynamic Analysis of Permanent Magnet Synchronous Generator with Power Electronics

    Directory of Open Access Journals (Sweden)

    OZCIRA, S.

    2010-05-01

    Full Text Available Permanent magnet DC motor-generators (PMDC, PMSG have been widely used in industrial and energy sectors recently. Power control of these systems can be achieved by controlling the output voltage. In this study, PMDC-PMSG systems are mathematically modeled and simulated in MATLAB and Simulink software. Then the results are discussed. A low power permanent magnet synchronous generator is driven by a permanent magnet DC motor and the output voltage is controlled by a frequency cycle-converter. The output of a half-wave uncontrolled rectifier is applied to an SPWM inverter and the power is supplied to a 300V, 50Hz load. The load which is connected to an LC filter is modeled by state-space equations. LC filter is utilized in order to suppress the voltage oscillations at the inverter output.

  11. Electronic and magnetic properties of zincblende half-metal superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Fong, C Y; Qian, M C; Pask, J; Yang, L H; Dag, S

    2003-11-05

    Zincblende half-metallic compounds such as CrAs, with large magnetic moments and high Curie temperatures, are promising materials for spintronic applications. They explore layered materials, consisting of alternating layers of zincblende half-metals, by first principles calculations, and find that superlattices of (CrAs){sub 1}(MnAs){sub 1} and (CrAs){sub 2}(MnAs){sub 2} are half-metallic with magnetic moments of 7.0{mu}{sub B} and 14.0{mu}{sub B} per unit cell, respectively. They discuss the nature of the bonding and half-metallicity in these materials and, based on the understanding acquired, develop a simple expression for the magnetic moment in such materials. They explore the range of lattice constants over which half-metallicity is manifested, and suggest corresponding substrates for growth in thin film form.

  12. On the Electron Diffusion Region in Asymmetric Reconnection with a Guide Magnetic Field

    Science.gov (United States)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-01-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  13. Transport Properties of Two-Dimensional Electron Gases in Antiparallel Magnetic-Electric Barrier Structures

    Institute of Scientific and Technical Information of China (English)

    PING Yun-Xia; CHENG Ze

    2006-01-01

    We study theoretically transport properties of two-dimensional electron gases through antiparallel magnetic electric barrier structures. Two kinds of magnetic barrier configurations are employed: one is that the strength of the double δ-function in opposite directions is equal and the other is that the strength is unequal. Similarities and differences of electronic transports are presented. It is found that the transmission and the conductance depend strongly on the shape of the magnetic barrier and the height of the electric barrier. The results indicate that this system does not possess any spin filtering and spin polarization and electron gases can realize perfect resonant tunneling and wave-vector filtering properties. Moreover, the strength of the effect of the inhomogeneous magnetic field on the transport properties is discussed.

  14. On the Electron Diffusion Region in Asymmetric Reconnection with a Guide Magnetic Field

    Science.gov (United States)

    Hesse, Michael; Liu, Yi-Hsin; Chen, Li-Jen; Bessho, Naoki; Kuznetsova, Masha; Birn, Joachim; Burch, James L.

    2016-01-01

    Particle-in-cell simulations in a 2.5-D geometry and analytical theory are employed to study the electron diffusion region in asymmetric reconnection with a guide magnetic field. The analysis presented here demonstrates that similar to the case without guide field, in-plane flow stagnation and null of the in-plane magnetic field are well separated. In addition, it is shown that the electric field at the local magnetic X point is again dominated by inertial effects, whereas it remains dominated by nongyrotropic pressure effects at the in-plane flow stagnation point. A comparison between local electron Larmor radii and the magnetic gradient scale lengths predicts that distribution should become nongyrotropic in a region enveloping both field reversal and flow stagnation points. This prediction is verified by an analysis of modeled electron distributions, which show clear evidence of mixing in the critical region.

  15. Generalized description of few-electron quantum dots at zero and nonzero magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Ciftja, Orion [Department of Physics, Prairie View A and M University, Prairie View, TX 77446 (United States)

    2007-01-31

    We introduce a generalized ground state variational wavefunction for parabolically confined two-dimensional quantum dots that equally applies to both cases of weak (or zero) and strong magnetic field. The wavefunction has a Laughlin-like form in the limit of infinite magnetic field, but transforms into a Jastrow-Slater wavefunction at zero magnetic field. At intermediate magnetic fields (where a fraction of electrons is spin-reversed) it resembles Halperin's spin-reversed wavefunction for the fractional quantum Hall effect. The properties of this variational wavefunction are illustrated for the case of two-dimensional quantum dot helium (a system of two interacting electrons in a parabolic confinement potential) where we find the description to be an excellent representation of the true ground state for the whole range of magnetic fields.

  16. Effects of the insulated magnetic field and oblique incidence of electrons on the multipactor in MILO

    Institute of Scientific and Technical Information of China (English)

    Fan Jie-Qing; Hao Jian-Hong

    2011-01-01

    The theoretical analysis and actual performance of the single-surface multipactor discharge model in the presence of a magnetic field are conducted through simulations. The effects of the magnitude of the insulated magnetic field and the oblique incidence of electrons on the multipactor are analysed. The results show that the multipactor susceptibility region shrinks gradually as the magnetic field increases when the electron cyclotron frequency is close to the RF frequency of the electric field. As a result, the evolution of the multipactor discharge will reach saturation earlier and become saturated at a higher level than the case when the magnetic field is absent, but the change of evolution and saturation as the insulated magnetic field increases is not obvious.

  17. Neutrino energy loss by electron capture in magnetic field at the crusts of neutron stars

    Institute of Scientific and Technical Information of China (English)

    LIU Jing-Jing; LUO Zhi-Quan

    2008-01-01

    Based on the p-f shell model,the effect of strong magnetic field on neutrino energy loss rates by electron capture is investigated.The calculations show that the magnetic field has only a slight effect on the neutrino energy loss rates in the range of 108-1013 G on the surfaces of most neutron stars.But for some magnetars,the range of the magnetic field is 1013-1018 G,and the neutrino energy loss rates are greatly reduced,even by more than four orders of magnitude due to the strong magnetic field.

  18. Strong electromagnetic waves in a magnetized relativistic electron-positron plasma

    Energy Technology Data Exchange (ETDEWEB)

    Yu, M.Y.; Shukla, P.K.; Rao, N.N. (Bochum Univ. (Germany, F.R.). Inst. fuer Theoretische Physik)

    1984-12-01

    It is shown that in a strongly magnetized relativistic electron-positron plasma, strongly localized large amplitude circularly polarized electromagnetic wave pulses exist. The localization is due to relativistic mass variation as well as ponderomotive force effects. Three types of pulses are found analytically: the sharply spiked pulse in a strongly magnetized cold plasma, the smooth pulse in a weak magnetized warm plasma, and the moderately spiked pulse for a weakly magnetized cold plasma. The physical mechanisms giving rise to these pulses are distinct for each case. Possible implications of our investigation to pulsar radiation are discussed.

  19. Measurement of hot electron transport in overdense plasma VIA self induced giant magnetic pulses

    Science.gov (United States)

    Mondal, S.; Narayanan, V.; Lad, Amit D.; Ahmed, Saima; Sengupta, S.; Das, A.; Sheng, Z. M.; Kaw, P. K.; Kumar, G. Ravindra

    2010-08-01

    Spatial and temporal resolved ultrashort(8ps) multimegagauss(65 MG) magnetic field has been measured in plasma produced on Al-coated BK-7 glass by the interaction of a relativististic intensity laser(4x1018W/cm2, 30 fs) using pump-probe polarimetry. The 2D profile of magnetic field is captured using a CCD camera. Mapping of this magnetic field maps the transport of relativistic electrons in the plasma. The magnetic field profiles indicate filamentary behavior (Weibel-like instability). Particle in cell simulation are used to explain the result obtained.

  20. Particle dynamics in the electron current layer in collisionless magnetic reconnection

    CERN Document Server

    Zenitani, Seiji

    2016-01-01

    Particle dynamics in the electron current layer in collisionless magnetic reconnection is investigated by using a particle-in-cell simulation. Electron motion and velocity distribution functions are studied by tracking self-consistent trajectories. New classes of electron orbits are discovered: figure-eight-shaped regular orbits inside the electron jet, noncrossing regular orbits on the jet flanks, noncrossing Speiser orbits, and nongyrotropic electrons in the downstream of the jet termination region. Properties of a super-Alfv\\'{e}nic outflow jet are attributed to an ensemble of electrons traveling through Speiser orbits. Noncrossing orbits are mediated by the polarization electric field near the electron current layer, and it turns out that they are non-negligible in number density. The impact of these new orbits to electron mixing, spatial distribution of energetic electrons, and observational signatures, is presented.

  1. Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection.

    Science.gov (United States)

    Eriksson, S; Wilder, F D; Ergun, R E; Schwartz, S J; Cassak, P A; Burch, J L; Chen, L-J; Torbert, R B; Phan, T D; Lavraud, B; Goodrich, K A; Holmes, J C; Stawarz, J E; Sturner, A P; Malaspina, D M; Usanova, M E; Trattner, K J; Strangeway, R J; Russell, C T; Pollock, C J; Giles, B L; Hesse, M; Lindqvist, P-A; Drake, J F; Shay, M A; Nakamura, R; Marklund, G T

    2016-07-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E_{∥}) that is larger than predicted by simulations. The high-speed (∼300  km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E_{∥} is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

  2. The Structure of the Electron Outflow Jet in Collisionless Magnetic Reconnection

    Science.gov (United States)

    Hesse, Michael; Zenitani, Seiji; Klimas, Alex

    2008-01-01

    Particle-in-cell simulations and analytic theory are applied to the study of the electron outflow jet in collisionless magnetic reconnection. In these jets, which have also been identified in spacecraft observations, electron flow speeds in thin layers exceed the ExB drift, suggesting that electrons are unmagnetized. In this study, we find the surprising result that the electron flow jets can be explained by a combination of EjcB drifts and of diamagnetic effects, through the combination of the gradients of particle pressure and of the magnetic field. In a suitably rotated coordinate system, the electron motion is readily decomposed into ExB drift and the motion to support the required current density, consistent with electron gyrotropy. This process appears to be nondissipative.

  3. Generation of a spin-polarized electron beam by multipoles magnetic fields

    CERN Document Server

    Karimi, Ebrahim; Boyd, Robert W; Santamato, Enrico

    2013-01-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin--magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of these analysis could prove useful in the design of improved electron microscope.

  4. Magnetospheric Multiscale Observations of the Electron Diffusion Region of Large Guide Field Magnetic Reconnection

    Science.gov (United States)

    Eriksson, S.; Wilder, F. D.; Ergun, R. E.; Schwartz, S. J.; Cassak, P. A.; Burch, J. L.; Chen, Li-Jen; Torbert, R. B.; Phan, T. D.; Lavraud, B.; hide

    2016-01-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of a large guide field magnetic reconnection event. The observations suggest that two of the four MMS spacecraft sampled the electron diffusion region, whereas the other two spacecraft detected the exhaust jet from the event. The guide magnetic field amplitude is approximately 4 times that of the reconnecting field. The event is accompanied by a significant parallel electric field (E(sub parallel lines) that is larger than predicted by simulations. The high-speed (approximately 300 km/s) crossing of the electron diffusion region limited the data set to one complete electron distribution inside of the electron diffusion region, which shows significant parallel heating. The data suggest that E(sub parallel lines) is balanced by a combination of electron inertia and a parallel gradient of the gyrotropic electron pressure.

  5. Calculation of fusion gain in fast ignition with magnetic target by relativistic electrons and protons

    Directory of Open Access Journals (Sweden)

    A Parvazian

    2010-12-01

    Full Text Available Fast ignition is a new method for inertial confinement fusion (ICF in which the compression and ignition steps are separated. In the first stage, fuel is compressed by laser or ion beams. In the second phase, relativistic electrons are generated by pettawat laser in the fuel. Also, in the second phase 5-35 MeV protons can be generated in the fuel. Electrons or protons can penetrate in to the ultra-dense fuel and deposit their energy in the fuel . More recently, cylindrical rather than spherical fuel chambers with magnetic control in the plasma domain have been also considered. This is called magnetized target fusion (MTF. Magnetic field has effects on relativistic electrons energy deposition rate in fuel. In this work, fast ignition method in cylindrical fuel chambers is investigated and transportation of the relativistic electrons and protons is calculated using MCNPX and FLUKA codes with 0. 25 and 0. 5 tesla magnetic field in single and dual hot spot. Furthermore, the transfer rate of relativistic electrons and high energy protons to the fuel and fusion gain are calculated. The results show that the presence of external magnetic field guarantees higher fusion gain, and relativistic electrons are much more appropriate objects for ignition. MTF in dual hot spot can be considered as an appropriate substitution for the current ICF techniques.

  6. Magnetic-field-induced suppression of tunnelling into a two-dimensional electron system

    Energy Technology Data Exchange (ETDEWEB)

    Reker, T.; Chung, Y.C.; Im, H.; Klipstein, P.C.; Nicholas, R.J. [Clarendon Laboratory, Department of Physics, University of Oxford, Oxford (United Kingdom); Shtrikman, Hadas [Braun Center for Submicron Research, Weizmann Institute of Science, Rehovot (Israel)

    2002-06-10

    Tunnelling between a three-dimensional emitter contact and a two-dimensional electron system (2DES) is studied in magnetic fields aligned perpendicular to the barriers of a double-barrier heterostructure. The differential conductance around the Fermi energy exhibits a magnetic-field-dependent pseudogap. This pseudogap is shown to be thermally activated and to depend on the two-dimensional electron density. We attribute this pseudogap to an extra energy that an electron tunnelling from the emitter into the 2DES has to overcome as a result of the correlated state of the 2DES. (author)

  7. Electronic structure and magnetic properties of selected lanthanide and actinide intermetallic Laves-phase alloys

    DEFF Research Database (Denmark)

    Eriksson, Olle; Johansson, Börje; Brooks, M. S. S.

    1989-01-01

    The electronic structure and magnetic properties of some yttrium and uranium Laves-phase pseudobinary alloys with 3d elements have been calculated. The calculations were done by simulating the electronic structure of the alloy by that of an ordered compound with the same stoichiometry. In general...... a good agreement between the experimental and theoretical magnetic moment was found, indicating that the spurious long-range order of the calculations is of minor importance. A comparison between the present supercell cluster approach and the virtual-crystal approximation for the electronic structure...

  8. Streaming energetic electrons in earth's magnetotail - Evidence for substorm-associated magnetic reconnection

    Science.gov (United States)

    Bieber, J. W.; Stone, E. C.

    1980-01-01

    This letter reports the results of a systematic study of streaming greater than 200 keV electrons observed in the magnetotail with the Caltech Electron/Isotope Spectrometers aboard IMP-7 and IMP-8. A clear statistical association of streaming events with southward magnetic fields, often of steep inclination, and with substorms as evidenced by the AE index is demonstrated. These results support the interpretation that streaming energetic electrons are indicative of substorm-associated magnetic reconnection in the near-earth plasma sheet.

  9. On the problem of electron loss in the outer radiation belt during a magnetic storm

    Science.gov (United States)

    Lazutin, L. L.

    2016-09-01

    An abrupt change in the latitudinal profile of energetic electrons in the Earth's outer radiation belt during magnetic storms is explained in many publications by a loss of electrons at L = 4-7 resulting from their departure to the atmosphere or to the magnetopause. In the present work, the loss of electrons is explained primarily by adiabatic transformation of the magnetic drift trajectories. For this purpose, the effect of dawnto- dusk asymmetry measured by low-orbit SERVIS-1 and KORONAS-F satellites is involved.

  10. A case study of the relation between energetic electrons and magnetic activity

    Science.gov (United States)

    Lam, Hing-Lan

    The case study is based on the event of Telesat Canada's Anik E-1 and E-2 satellite failures on two consecutive days of January 20 and 21 in 1994. The malfunction of the two satellites wreaked havoc with television and computer data transmissions across Canada, as well as telephone services to remote northern communities. The fluxes of ∼2 MeV energetic electrons were high prior to the occurrences of the two Anik E satellite upsets. In this study, energetic electron fluxes were checked against magnetic activity. Strong Pc5 magnetic pulsations in the ground magnetic fluctuations were found to be present during periods of high electron fluxes, lending support to the contention of Pc5 ULF waves as a mechanism for energetic electron flux enhancement.

  11. Electronic structure and magnetism of samarium and neodymium adatoms on free-standing graphene

    Science.gov (United States)

    Kozub, Agnieszka L.; Shick, Alexander B.; Máca, František; Kolorenč, Jindřich; Lichtenstein, Alexander I.

    2016-09-01

    The electronic structure of selected rare-earth atoms adsorbed on a free-standing graphene was investigated using methods beyond the conventional density functional theory (DFT+U , DFT+HIA, and DFT+ED). The influence of the electron correlations and the spin-orbit coupling on the magnetic properties has been examined. The DFT+U method predicts both atoms to carry local magnetic moments (spin and orbital) contrary to a nonmagnetic f6 (J =0 ) ground-state configuration of Sm in the gas phase. Application of DFT +Hubbard-I (HIA) and DFT +exact diagonalization (ED) methods cures this problem, and yields a nonmagnetic ground state with six f electrons and J =0 for the Sm adatom. Our calculations show that Nd adatom remains magnetic, with four localized f electrons and J =4.0 . These conclusions could be verified by STM and XAS experiments.

  12. A laser accelerator. [interaction of polarized light beam with electrons in magnetic field

    Science.gov (United States)

    Colson, W. B.; Ride, S. K.

    1979-01-01

    It is shown that a laser can efficiently accelerate charged particles if a magnetic field is introduced to improve the coupling between the particle and the wave. Solving the relativistic equations of motion for an electron in a uniform magnetic field and superposed, circularly polarized electromagnetic wave, it is found that in energy-position phase space an electron traces out a curtate cycloid: it alternately gains and loses energy. If, however, the parameters are chosen so that the electron's oscillations in the two fields are resonant, it will continually accelerate or decelerate depending on its initial position within a wavelength of light. A laboratory accelerator operating under these resonant conditions appears attractive: in a magnetic field of 10,000 gauss, and the fields of a 5 x 10 to the 12th W, 10 micron wavelength laser, an optimally positioned electron would accelerate to 700 MeV in only 10 m.

  13. Experimental Verification of the Role of Electron Pressure in Fast Magnetic Reconnection with a Guide Field.

    Science.gov (United States)

    Fox, W; Sciortino, F; V Stechow, A; Jara-Almonte, J; Yoo, J; Ji, H; Yamada, M

    2017-03-24

    We report detailed laboratory observations of the structure of a reconnection current sheet in a two-fluid plasma regime with a guide magnetic field. We observe and quantitatively analyze the quadrupolar electron pressure variation in the ion-diffusion region, as originally predicted by extended magnetohydrodynamics simulations. The projection of the electron pressure gradient parallel to the magnetic field contributes significantly to balancing the parallel electric field, and the resulting cross-field electron jets in the reconnection layer are diamagnetic in origin. These results demonstrate how parallel and perpendicular force balance are coupled in guide field reconnection and confirm basic theoretical models of the importance of electron pressure gradients for obtaining fast magnetic reconnection.

  14. An in situ Comparison of Electron Acceleration at Collisionless Shocks under Differing Upstream Magnetic Field Orientations

    Science.gov (United States)

    Masters, A.; Sulaiman, A. H.; Stawarz, Ł.; Reville, B.; Sergis, N.; Fujimoto, M.; Burgess, D.; Coates, A. J.; Dougherty, M. K.

    2017-07-01

    A leading explanation for the origin of Galactic cosmic rays is acceleration at high-Mach number shock waves in the collisionless plasma surrounding young supernova remnants. Evidence for this is provided by multi-wavelength non-thermal emission thought to be associated with ultrarelativistic electrons at these shocks. However, the dependence of the electron acceleration process on the orientation of the upstream magnetic field with respect to the local normal to the shock front (quasi-parallel/quasi-perpendicular) is debated. Cassini spacecraft observations at Saturn’s bow shock have revealed examples of electron acceleration under quasi-perpendicular conditions, and the first in situ evidence of electron acceleration at a quasi-parallel shock. Here we use Cassini data to make the first comparison between energy spectra of locally accelerated electrons under these differing upstream magnetic field regimes. We present data taken during a quasi-perpendicular shock crossing on 2008 March 8 and during a quasi-parallel shock crossing on 2007 February 3, highlighting that both were associated with electron acceleration to at least MeV energies. The magnetic signature of the quasi-perpendicular crossing has a relatively sharp upstream-downstream transition, and energetic electrons were detected close to the transition and immediately downstream. The magnetic transition at the quasi-parallel crossing is less clear, energetic electrons were encountered upstream and downstream, and the electron energy spectrum is harder above ˜100 keV. We discuss whether the acceleration is consistent with diffusive shock acceleration theory in each case, and suggest that the quasi-parallel spectral break is due to an energy-dependent interaction between the electrons and short, large-amplitude magnetic structures.

  15. Studies of Beam Induced Electron Cloud Resonances in Dipole Magnetic Fields

    CERN Document Server

    Calvey, J R; Makita, J; Venturini, M

    2016-01-01

    The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. Both resonances have been studied directly in dipole fields using retarding field analyzers installed in the Cornell Electron Storage Ring (CESR). These measurements are supported by both analytical models and computer simulations.

  16. Cyclotron radiation cooling of a short electron bunch kicked in an undulator with guiding magnetic field

    Directory of Open Access Journals (Sweden)

    I. V. Bandurkin

    2015-11-01

    Full Text Available We propose to use of an undulator with the guiding axial magnetic field as a “kicker” forming a bunch of electron gyro-oscillators with a small spread in the axial velocity. The cyclotron emission from the bunch leads to losing oscillatory velocity of electron gyrorotation, but it does not perturb the axial electron velocity. This effect can be used for transformation of minimization of the spread in electron axial velocity in the undulator section into minimization of the spread in electron energy in the cyclotron radiation section.

  17. One-electron versus electron-electron interaction contributions to the spin-spin coupling mechanism in nuclear magnetic resonance spectroscopy: analysis of basic electronic effects.

    Science.gov (United States)

    Gräfenstein, Jürgen; Cremer, Dieter

    2004-12-22

    For the first time, the nuclear magnetic resonance (NMR) spin-spin coupling mechanism is decomposed into one-electron and electron-electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin-spin coupling constants result from totally different Fermi contact coupling mechanisms. (1)J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas (2)J(H,H) spin-spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of (1)J(C,H) and (2)J(H,H), respectively, for hydrocarbons.

  18. Propagation of Vortex Electron Wave Functions in a Magnetic Field

    CERN Document Server

    Gallatin, Gregg M

    2012-01-01

    The physics of coherent beams of photons carrying axial orbital angular momentum (OAM) is well understood and such beams, sometimes known as vortex beams, have found applications in optics and microscopy. Recently electron beams carrying very large values of axial OAM have been generated. In the absence of coupling to an external electromagnetic field the propagation of such vortex electron beams is virtually identical mathematically to that of vortex photon beams propagating in a medium with a homogeneous index of refraction. But when coupled to an external electromagnetic field the propagation of vortex electron beams is distinctly different from photons. Here we use the exact path integral solution to Schrodingers equation to examine the time evolution of an electron wave function carrying axial OAM. Interestingly we find that the nonzero OAM wave function can be obtained from the zero OAM wave function, in the case considered here, simply by multipling it by an appropriate time and position dependent pref...

  19. Electron acceleration at slow-mode shocks in the magnetic reconnection region in solar flares

    Science.gov (United States)

    Mann, Gottfried; Aurass, Henry; Önel, Hakan; Warmuth, Alexander

    2016-04-01

    A solar flare appears as an sudden enhancement of the emission of electromagnetic radiation of the Sun covering a broad range of the spectrum from the radio up to the gamma-ray range. That indicates the generation of energetic electrons during flares, which are considered as the manifestation of magnetic reconnection in the solar corona. Spacecraft observations in the Earth's magnetosphere, as for instance by NASA's MMS mission, have shown that electrons can efficiently accelerated at the slow-mode shocks occuring in the magnetic reconnection region. This mechanism is applied to solar flares. The electrons are accelerated by the cross-shock potential at slow-mode shocks resulting in magnetic field aligned beams of energetic electrons in the downstream region. The interaction of this electron beam with the plasma leads to the excitation of whistler waves and, subsequently, to a strong heating of the electrons in the downstream region. Considering this process under coronal circumstances, enough electrons with energies >30keV are generated in the magnetic reconnection region as required for the hard X-ray radiation during solar flares as observed by NASA's RHESSI mission.

  20. MAGNETIC MODELING VS MEASUREMENTS OF THE DIPOLES FOR THE JLAB 10 KW FREE ELECTRON LASER UPGRADE

    Energy Technology Data Exchange (ETDEWEB)

    David Douglas; Robin Wines; Tom Hiatt; George Biallas; Kenneth Baggett; T.J. Schultheiss; V.A. Christina; J.W. Rathke; A. Smirnov; D. Newsham; Y. Luo; D. Yu

    2003-05-01

    Magnetic measurements of the six families of dipoles for the infrared Free Electron Laser Upgrade at the Thomas Jefferson National Accelerator Facility (Jlab) are compared to the magnetic models on which their design is based. The magnets were designed in parallel by three organizations. They used ANSYS, Radia or Opera 3D as a 3D magnetic modeling program. Comparison of the discrepancies between model and magnet measurement is presented along with analysis of their potential causes. These dipoles operate in two field ranges. The Injector/ Extractor Dipoles operate around 0.05 T and the Arc Dipoles and Optical Chicane Dipoles operate between 0.22 to 0.71 T. All magnets are required to meet core field and field integral flatness to parts in 104 over their good field region.

  1. Improvement of charged particles transport across a transverse magnetic filter field by electrostatic trapping of magnetized electrons

    Energy Technology Data Exchange (ETDEWEB)

    Das, B. K., E-mail: bdyt.ds@rediffmail.com; Hazarika, P.; Chakraborty, M. [Centre of Plasma Physics-Institute for Plasma Research, Tepesia-782402, Kamrup, Assam (India); Bandyopadhyay, M., E-mail: mainak@iter-india.org [ITER-India, Institute for Plasma Research, Gandhinagar-382025, Gujarat (India)

    2014-07-15

    A study on the transport of charged particles across a magnetic filter field has been carried out in a double plasma device (DPD) and presented in this manuscript. The DPD is virtually divided into two parts viz. source and target regions by a transverse magnetic field (TMF) which is constructed by inserting strontium ferrite magnets into two stainless steel rectangular tubes. Plasma electrons are magnetized but ions are unmagnetized inside the TMF region. Negative voltages are applied to the TMF tubes in order to reduce the loss of electrons towards them. Plasma is produced in the source region by filament discharge method and allowed to flow towards the target region through this negatively biased TMF. It is observed that in the target region, plasma density can be increased and electron temperature decreased with the help of negatively biased TMF. This observation is beneficial for negative ion source development. Plasma diffusion across the negatively biased TMF follows Bohm or anomalous diffusion process when negative bias voltage is very less. At higher negative bias, diffusion coefficient starts deviating from the Bohm diffusion value, associated with enhanced plasma flow in the target region.

  2. Experimental modelling of the dipole magnet for the electron storage ring DELSY

    CERN Document Server

    Meshkov, I N; Syresin, E M

    2003-01-01

    In the Joint Institute for Nuclear Research (Dubna) the project of Dubna Electron Synchrotron (DELSY) with an electron energy of 1.2 GeV is developed. The electron storage ring in the DELSY project is planned to be created on the basis of magnetic elements, which were used earlier in the storage ring AmPS (NIKHEF, Amsterdam). The optics of the ring is necessary to be changed, its perimeter to be reduced approximately in one and a half time, the energy of electrons to be increased. The paper is devoted to the development of a modified dipole magnet of the storage ring. The preliminary estimation of geometry of the magnet pole is carried out by means of computer modelling using two- and three- dimensional codes of the magnetic field calculation SUPERFISH and RADIA. The experimental stand for the measurements of the dipole magnetic field is described. As the result of calculational and experimental modelling for the dipole magnet, the geometry of its poles was estimated, providing in the horizontal aperture +- 3...

  3. Effect of magnetic field on an electronic structure and intraband quantum transitions in multishell quantum dots

    Science.gov (United States)

    Holovatsky, V. A.; Voitsekhivska, O. M.; Yakhnevych, M. Ya.

    2017-09-01

    The electron energy spectrum and wave functions in multishell spherical quantum dot, consisting of core and two spherical shells - potential wells separated by thin potential barriers, are obtained in the framework of the effective mass approximation and single band model. The investigations are performed within the matrix method for the nanostructure driven by magnetic field using the complete set of wave functions obtained without the magnetic field. The electron dipole momentum and oscillator strengths of intraband quantum transitions as functions of the magnetic field induction are numerically calculated. In order to increase the sensibility to magnetic field, the geometric parameters of the shells are chosen in such a way that the electron in the ground state is to be located in outer spherical well, but when the magnetic field induction becomes bigger, it moves into the core. It is shown that size of the middle potential well causes the smooth change of the electron location due to the effect of magnetic field, what is displayed on optical properties of nanostructure. The calculations are performed for multishell quantum dot CdSe/ZnS/CdSe/ZnS/CdSe.

  4. Electronic and magnetic properties of spiral spin-density-wave states in transition-metal chains

    Science.gov (United States)

    Tanveer, M.; Ruiz-Díaz, P.; Pastor, G. M.

    2016-09-01

    The electronic and magnetic properties of one-dimensional (1D) 3 d transition-metal nanowires are investigated in the framework of density functional theory. The relative stability of collinear and noncollinear (NC) ground-state magnetic orders in V, Mn, and Fe monoatomic chains is quantified by computing the frozen-magnon dispersion relation Δ E (q ⃗) as a function of the spin-density-wave vector q ⃗. The dependence on the local environment of the atoms is analyzed by varying systematically the lattice parameter a of the chains. Electron correlation effects are explored by comparing local spin-density and generalized-gradient approximations to the exchange and correlation functional. Results are given for Δ E (q ⃗) , the local magnetic moments μ⃗i at atom i , the magnetization-vector density m ⃗(r ⃗) , and the local electronic density of states ρi σ(ɛ ) . The frozen-magnon dispersion relations are analyzed from a local perspective. Effective exchange interactions Ji j between the local magnetic moments μ⃗i and μ⃗j are derived by fitting the ab initio Δ E (q ⃗) to a classical 1D Heisenberg model. The dominant competing interactions Ji j at the origin of the NC magnetic order are identified. The interplay between the various Ji j is revealed as a function of a in the framework of the corresponding magnetic phase diagrams.

  5. Quantitative in situ magnetization reversal studies in Lorentz microscopy and electron holography

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, L.A. [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); CEMES-CNRS 29, rue Jeanne Marvig, B.P. 94347, F-31055 Toulouse Cedex (France); Magén, C., E-mail: cmagend@unizar.es [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); Fundación ARAID, 50018 Zaragoza (Spain); Snoeck, E.; Gatel, C. [Transpyrenean Associated Laboratory for Electron Microscopy (TALEM), CEMES-INA, CNRS-Universidad de Zaragoza, Toulouse (France); CEMES-CNRS 29, rue Jeanne Marvig, B.P. 94347, F-31055 Toulouse Cedex (France); Marín, L. [Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, 50018 Zaragoza (Spain); Serrano-Ramón, L. [Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Instituto de Ciencia de Materiales de Aragón (ICMA), Universidad de Zaragoza-CSIC, 50009 Zaragoza (Spain); and others

    2013-11-15

    A generalized procedure for the in situ application of magnetic fields by means of the excitation of the objective lens for magnetic imaging experiments in Lorentz microscopy and electron holography is quantitatively described. A protocol for applying magnetic fields with arbitrary in-plane magnitude and orientation is presented, and a freeware script for Digital Micrograph{sup ™} is provided to assist the operation of the microscope. Moreover, a method to accurately reconstruct hysteresis loops is detailed. We show that the out-of-plane component of the magnetic field cannot be always neglected when performing quantitative measurements of the local magnetization. Several examples are shown to demonstrate the accuracy and functionality of the methods. - Highlights: • Generalized procedure for application of magnetic fields with the TEM objective lens. • Arbitrary in-plane magnetic field magnitude and orientation can be applied. • Method to accurately reconstruct hysteresis loops by electron holography. • Out-of-plane field component should be considered in quantitative measurements. • Examples to illustrate the method in Lorentz microscopy and electron holography.

  6. Electron acceleration in collisionless shocks and magnetic reconnection by laser-produced plasma ablation

    Science.gov (United States)

    Park, Jaehong; Spitkovksy, Anatoly; Fox, Will; Bhattacharjee, Amitava

    2016-10-01

    We perform particle-in-cell simulations of collisionless shocks and magnetic reconnection generated by ablated plasma expanding into a magnetized background plasma. We find: (1) The simulated proton radiography produces different morphology of the shock structure depending on the orientation of the magnetic field and can be used to identify a shock in the experiment. Electrons are accelerated by the whistler waves generated at oblique sites of the shock. (2) Forced collisionless magnetic reconnection is induced when the expanding plumes carry opposite magnetic polarities and interact with a background plasma. Electrons are accelerated at the reconnection X line and reveal a power-law distribution as the plasma beta is lowered, β = 0.08 . As the plasma beta is increased, β = 0.32 , the 1st order Fermi mechanism against the two plasma plumes contributes to the electron acceleration as well as the X line acceleration. Using 3-D simulations, we also explore the effect of 3-D instabilities (Weibel instability or drift-kink) on particle acceleration and magnetic field annihilation between the colliding magnetized plumes

  7. Measuring the electron beam energy in a magnetic bunch compressor

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, Kirsten

    2010-09-15

    Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 {mu}m precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

  8. Mechanisms of the outer radiation belt electron flux variation during magnetic storms

    Science.gov (United States)

    Nakamura, M.; Obara, T.; Koshiishi, H.; Koga, K.; Matsumoto, H.; Goka, T.

    2003-12-01

    We have investigated variations of the energetic electron flux (> 0.4 MeV) and the magnetic field in the outer radiation belt obtained from the Standard DOse Monitor (SDOM) and the MAgnetoMeter (MAM) of the Space Environment Data Acquisition equipment (SEDA) onboard Tsubasa (Mission Demonstration Test Satellite (MDS)-1). Since Tsubasa operates in geostationary transfer orbit (GTO) with an orbital period of 10 hours and an inclination of 28.5 degrees, it has provided a rare opportunity for directly observing near-equatorial radiation belt plasma particles and the magnetic field during magnetic storms. The decreases of the energetic electron flux during the main phase of the magnetic storms, and the subsequent recoveries and enhancements during the recovery phase in the outer radiation belt are linked respectively to typical variations of the magnetic field. At the moment that the outer radiation belt flux sharply drops during the main phase of the 17 April 2002 magnetic storm, the butterfly distribution is observed at L=5 and the magnetic equator where the magnitude of magnetic field is much smaller than the IGRF model. Calculating the drift motions of the energetic electrons in the Tyganenko 2001 magnetospheric magnetic field model, shows that the drift-shell splitting mechanism could generate the butterfly distribution due to loss of the near-equatorially mirroring electrons through dayside magnetopause boundary. We evaluate roles and contributions of the other possible mechanisms to explain the flux decreases. We discuss the three-dimensional field configuration in the magnetopause to compare with the low earth orbital observation of the outer radiation belt flux.

  9. One-electron singular spectral features of the 1D Hubbard model at finite magnetic field

    Science.gov (United States)

    Carmelo, J. M. P.; Čadež, T.

    2017-01-01

    The momentum, electronic density, spin density, and interaction dependences of the exponents that control the (k , ω)-plane singular features of the σ = ↑ , ↓ one-electron spectral functions of the 1D Hubbard model at finite magnetic field are studied. The usual half-filling concepts of one-electron lower Hubbard band and upper Hubbard band are defined in terms of the rotated electrons associated with the model Bethe-ansatz solution for all electronic density and spin density values and the whole finite repulsion range. Such rotated electrons are the link of the non-perturbative relation between the electrons and the pseudofermions. Our results further clarify the microscopic processes through which the pseudofermion dynamical theory accounts for the one-electron matrix elements between the ground state and excited energy eigenstates.

  10. Magnetic transition and electronic transport in colossal magnetoresistance perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Lofland, S.E.; Bhagat, S.M. [Department of Physics, University of Maryland, College Park, Maryland 20742-4111 (United States); Ghosh, K.; Greene, R.L. [Center for Superconductivity Research, University of Maryland, College Park, Maryland 20742-4111 (United States); Karabashev, S.G.; Shulyatev, D.A.; Arsenov, A.A.; Mukovskii, Y. [Moscow State Steel and Alloys Institute, Leninskii Prospect 4, Moscow 117936 (Russia)

    1997-12-01

    We present here the results of a careful study of the magnetic transition, as well as, the dc resistivity in the same specimen of a single crystal of La{sub 0.8}Sr{sub 0.2}MnO{sub 3}. We find that the Curie temperature of the specimen is far below the point where the temperature coefficient of the resistivity changes sign. {copyright} {ital 1997} {ital The American Physical Society}

  11. Morphological, electronic and magnetic characterization of bulk Cr tips

    Energy Technology Data Exchange (ETDEWEB)

    Corbetta, Marco; Ouazi, Safia; Nahas, Yasmine; Oka, Hirofumi; Wedekind, Sebastian; Sander, Dirk; Kirschner, Juergen [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany); Donati, Fabio [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany); CNISM, NEMAS, Milano (Italy); Dipartimento di Energia - Politecnico di Milano, Milano (Italy)

    2011-07-01

    The most delicate task for successful SP-STM measurements is the preparation of suitable tips offering high spatial resolution, high spin polarization and negligible magnetic stray field. Nonmagnetic tips covered with an ultrathin film of antiferromagnetic material as Cr have been largely and successfully used. The main drawback of coated tips is that an in-situ preparation is required. Recently a simple and reliable method for the preparation of bulk Cr tips using only a standard electrochemical etching has been proposed. We produced and used such tips for in-field spin-polarized STM measurements at 7 K on Co nano-islands on Cu(111). We obtain stable and reliable spin-resolved imaging and spectroscopy results. We measure symmetric hysteresis loops of the differential conductance, which show that the magnetization direction of the Cr tip apex follows the external magnetic field direction. Measuring dI/dV asymmetry curves on Co islands we find that the spin polarization of bulk Cr tips can be as large as 30%, which is larger as compared to Cr/Co/W tips.

  12. Electronic and magnetic properties of Mn-doped WSe2 monolayer under strain

    Science.gov (United States)

    Xin, Qianqian; Zhao, Xu; Wang, Tianxing

    2017-04-01

    Electronic and magnetic properties of Mn-doped WSe2 monolyer subject to isotropic strain are investigated using the first-principles methods based on the density functional theory. Our results indicate that Mn-doped WSe2 monolayer is a magnetic semiconductor nanomaterial with strong spontaneous magnetism without strain and the total magnetic moment of Mn-doped system is 1.038μB. We applied strain to Mn-doped WSe2 monolayer from -10% to 10%. The doped system transforms from magnetic semiconductor to half-metallic material from -10% to -2% compressive strain and from 2% to 6% tensile strain. The largest half-metallic gap is 0.450 eV at -2% compressive strain. The doped system shows metal property from 7% to 10%. Its maximum magnetic moment comes to 1.181μB at 6% tensile strain. However, the magnetic moment of system decreases to zero sharply when tensile strain arrived at 7%. Strain changes the redistribution of charges and arises to the magnetic effect. The coupling between the 3d orbital of Mn atom, 5d orbital of W atom and 4p orbital of Se atom is analyzed to explain the strong strain effect on the magnetic properties. Our studies predict Mn-doped WSe2 monolayers under strain to be candidates for thin dilute magnetic semiconductors, which is important for application in semiconductor spintronics.

  13. Scanning Electron Microscope-Cathodoluminescence Analysis of Rare-Earth Elements in Magnets.

    Science.gov (United States)

    Imashuku, Susumu; Wagatsuma, Kazuaki; Kawai, Jun

    2016-02-01

    Scanning electron microscope-cathodoluminescence (SEM-CL) analysis was performed for neodymium-iron-boron (NdFeB) and samarium-cobalt (Sm-Co) magnets to analyze the rare-earth elements present in the magnets. We examined the advantages of SEM-CL analysis over conventional analytical methods such as SEM-energy-dispersive X-ray (EDX) spectroscopy and SEM-wavelength-dispersive X-ray (WDX) spectroscopy for elemental analysis of rare-earth elements in NdFeB magnets. Luminescence spectra of chloride compounds of elements in the magnets were measured by the SEM-CL method. Chloride compounds were obtained by the dropwise addition of hydrochloric acid on the magnets followed by drying in vacuum. Neodymium, praseodymium, terbium, and dysprosium were separately detected in the NdFeB magnets, and samarium was detected in the Sm-Co magnet by the SEM-CL method. In contrast, it was difficult to distinguish terbium and dysprosium in the NdFeB magnet with a dysprosium concentration of 1.05 wt% by conventional SEM-EDX analysis. Terbium with a concentration of 0.02 wt% in an NdFeB magnet was detected by SEM-CL analysis, but not by conventional SEM-WDX analysis. SEM-CL analysis is advantageous over conventional SEM-EDX and SEM-WDX analyses for detecting trace rare-earth elements in NdFeB magnets, particularly dysprosium and terbium.

  14. Achievement of a record electron temperature for a magnetic mirror device

    CERN Document Server

    Bagryansky, P A; Lizunov, A A; Maximov, V V; Prikhodko, V V; Shalashov, A G; Soldatkina, E I; Solomakhin, A L; Yakovlev, D V

    2014-01-01

    We demonstrate plasma discharges with extremely high temperature of bulk electrons at the large axially symmetric magnetic mirror device GDT (Budker Institute, Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over several sequential shots is 660 $\\pm$ 50 eV with peak values exceeding 900 eV in few shots. This corresponds to at least threefold increase as compared to previous experiments both at the GDT and at other comparable machines, thus demonstrating the maximum quasi-stationary (~1 ms) electron temperature achieved in open traps. The breakthrough is made possible with application of sophisticated electron cyclotron resonance heating in addition to standard heating by neutral beams. The reported increase of the electron temperature along with previous experiments, which demonstrated high-density plasma confinement with $\\beta\\approx$ 60%, provide a firm basis for extrapolating to fusion relevant applications of open magnetic systems.

  15. Electron transport properties in InAs four-terminal ballistic junctions under weak magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, M.; Fujiwara, K.; Amano, N.; Maemoto, T.; Sasa, S.; Inoue, M. [Nanomaterials Microdevices Research Center, Osaka Institute of Technology (JP)u, Osaka 535-8585 (Japan)

    2009-06-15

    We report on the electron transport properties based on ballistic electrons under magnetic fields in four-terminal ballistic junctions fabricated on an InAs/AlGaSb heterostructure. The four-terminal junction structure is composed of two longitudinal stems with two narrow wires slanted with 30 degree from the perpendicular axis. The electron focusing peak was obtained with the bend resistance measurement. Then it was investigated the nonlinear electron transport property of potential difference between longitudinal stems due to ballistic electrons with applying direct current from narrow wires. Observed nonlinearity showed clear rectification effects which have negative polarity regardless of input voltage polarity. Although this nonlinearity was qualitatively changed due to the Lorentz force under magnetic fields, the degradation of ballistic effects on nonlinear properties were observed when the current increased to higher strength. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Multipoint Measurements of the Electron Jet of Symmetric Magnetic Reconnection with a Moderate Guide Field

    Science.gov (United States)

    Wilder, F. D.; Ergun, R. E.; Eriksson, S.; Phan, T. D.; Burch, J. L.; Ahmadi, N.; Goodrich, K. A.; Newman, D. L.; Trattner, K. J.; Torbert, R. B.; Giles, B. L.; Strangeway, R. J.; Magnes, W.; Lindqvist, P.-A.; Khotyaintsev, Yu-V.

    2017-06-01

    We report observations from the Magnetospheric Multiscale (MMS) satellites of the electron jet in a symmetric magnetic reconnection event with moderate guide field. All four spacecraft sampled the ion diffusion region and observed the electron exhaust. The observations suggest that the presence of the guide field leads to an asymmetric Hall field, which results in an electron jet skewed towards the separatrix with a nonzero component along the magnetic field. The jet appears in conjunction with a spatially and temporally persistent parallel electric field ranging from -3 to -5 mV /m , which led to dissipation on the order of 8 nW /m3 . The parallel electric field heats electrons that drift through it, and is associated with a streaming instability and electron phase space holes.

  17. Model of Electron Pressure Anisotropy in the Process of Magnetic Reconnection

    Science.gov (United States)

    Divin, A. V.; Lapenta, G.; Markidis, S.

    2009-12-01

    In our work we use particle-in-cell simulations of plasma for the study of magnetic reconection. Details of the diffusive process inside electron diffusion region (EDR) are explored. Reconnection is considered in two-dimensional antiparallel approach and pressure anisotropy is well-known to provide for collisionless dissipation in such configurations. We identify particles of different trajectories near X-point and their contribution to the pressure tensor anisotropy. Electrons are magnetized far from X-point (gyrotropic particle distribution) but gyrotropy is lost as the magnetic field vanishes near the X-point and electrons behave non-adiabaticly. The transition between inflow distribution and accelerated particles manifests itself as a tilt of distribution function, which creates pressure anisotropy and renders electron pressure divergency to be non-zero. Assuming stationarity of the reconnection process, next we apply test particle approach and trace particles back in time over characteristic meandering time. It allows for the separation between different populations of particles: those particles which meander in the vicinity of X-point are accelerating and trapped, whereas magnetized particles display drift motion and stay inside the inflow region. Model of electron pressure anisotropy is proposed, based on such bi-Maxwellian origin of the distribution function inside EDR. Equating reconnection electric field and divergency of pressure tensor at the X-point, we obtain scalings for the elecron flow velocity, width and total electron current within EDR.

  18. Formation of electron energy spectra during magnetic reconnection in laser-produced plasma

    Science.gov (United States)

    Huang, Kai; Lu, Quanming; Huang, Can; Dong, Quanli; Wang, Huanyu; Fan, Feibin; Sheng, Zhengming; Wang, Shui; Zhang, Jie

    2017-10-01

    Energetic electron spectra formed during magnetic reconnection between two laser-produced plasma bubbles are investigated by the use of two-dimensional particle-in-cell simulations. It is found that the evolution of such an interaction between the two plasma bubbles can be separated into two distinct stages: squeezing and reconnection stages. In the squeezing stage, when the two plasma bubbles expand quickly and collide with each other, the magnetic field in the inflow region is greatly enhanced. In the second stage, a thin current sheet is formed between the two plasma bubbles, and then, magnetic reconnection occurs therein. During the squeezing stage, electrons are heated in the perpendicular direction by betatron acceleration due to the enhancement of the magnetic field around the plasma bubbles. Meanwhile, non-thermal electrons are generated by the Fermi mechanism when these electrons bounce between the two plasma bubbles approaching quickly and get accelerated mainly by the convective electric field associated with the plasma bubbles. During the reconnection stage, electrons get further accelerated mainly by the reconnection electric field in the vicinity of the X line. When the expanding speed of the plasma bubbles is sufficiently large, the formed electron energy spectra have a kappa distribution, where the lower energy part satisfies a Maxwellian function and the higher energy part is a power-law distribution. Moreover, the increase in the expanding speed will result in the hardening of formed power-law spectra in both the squeezing and reconnection stages.

  19. Calibrating MMS Electron Drift Instrument (EDI) Ambient Electron Flux Measurements and Characterizing 3D Electric Field Signatures of Magnetic Reconnection

    Science.gov (United States)

    Shuster, J. R.; Torbert, R. B.; Vaith, H.; Argall, M. R.; Li, G.; Chen, L. J.; Ergun, R. E.; Lindqvist, P. A.; Marklund, G. T.; Khotyaintsev, Y. V.; Russell, C. T.; Magnes, W.; Le Contel, O.; Pollock, C. J.; Giles, B. L.

    2015-12-01

    The electron drift instruments (EDIs) onboard each MMS spacecraft are designed with large geometric factors (~0.01cm2 str) to facilitate detection of weak (~100 nA) electron beams fired and received by the two gun-detector units (GDUs) when EDI is in its "electric field mode" to determine the local electric and magnetic fields. A consequence of the large geometric factor is that "ambient mode" electron flux measurements (500 eV electrons having 0°, 90°, or 180° pitch angle) can vary depending on the orientation of the EDI instrument with respect to the magnetic field, a nonphysical effect that requires a correction. Here, we present determinations of the θ- and ø-dependent correction factors for the eight EDI GDUs, where θ (ø) is the polar (azimuthal) angle between the GDU symmetry axis and the local magnetic field direction, and compare the corrected fluxes with those measured by the fast plasma instrument (FPI). Using these corrected, high time resolution (~1,000 samples per second) ambient electron fluxes, combined with the unprecedentedly high resolution 3D electric field measurements taken by the spin-plane and axial double probes (SDP and ADP), we are equipped to accurately detect electron-scale current layers and electric field waves associated with the non-Maxwellian (anisotropic and agyrotropic) particle distribution functions predicted to exist in the reconnection diffusion region. We compare initial observations of the diffusion region with distributions and wave analysis from PIC simulations of asymmetric reconnection applicable for modeling reconnection at the Earth's magnetopause, where MMS will begin Science Phase 1 as of September 1, 2015.

  20. 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.

  1. Electronic and magnetic properties of germanene: Surface functionalization and strain effects

    Science.gov (United States)

    Liang, Pei; Liu, Yang; Xing, Song; Shu, Haibo; Tai, Bo

    2016-01-01

    The surface functionalization and strain effects on the structural, electronic, and magnetic properties of full-/half-passivated germanenes are investigated systematically by the first-principle calculations within density functional theory. It is found that the germanenes with full-passivation have different band structures. i.e., the band-gap of GeH is larger than that of GeF and GeCl. Interestingly, when surface passivation and strain are utilized, germanenes go through a transformation from semiconductor to semi-metal. Moreover, germanenes with half-passivation present different magnetic characters, i.e,. Ge2H is a ferromagnetic semiconductor, while Ge2F and Ge2Cl are anti-ferromagnetic semiconductors. The stability of magnetic coupling of Ge2Xs can be modulated by external strain. Our calculations indicate that the electronic and magnetic properties of passivated-germanenes strongly depend on their surface functionalization and strain effects.

  2. Electron and ion heating characteristics during magnetic reconnection in MAST

    CERN Document Server

    Tanabe, H; Watanabe, T; Gi, K; Kadowaki, K; Inomoto, M; Imazawa, R; Gryaznevich, M; Michael, C; Crowley, B; Conway, N; Scannell, R; Harrison, J; Fitzgerald, I; Meakins, A; Hawkes, N; Cheng, C Z; Ono, Y

    2015-01-01

    Local electron and ion heating characteristics during merging reconnection startup on the MAST spherical tokamak have been revealed for the first time using a 130 channel YAG-TS system and a new 32 chord ion Doppler tomography diagnostic. 2D local profile measurement of $T_e$, $n_e$ and $T_i$ detect highly localized electron heating at the X point and bulk ion heating downstream. For the push merging experiment under high guide field condition, thick layer of closed flux surface formed by reconnected field sustains the heating profile for more than electron and ion energy relaxation time $\\tau^E_{ei}\\sim4-10$ms, both heating profiles finally form triple peak structure at the X point and downstream. Toroidal guide field mostly contributes the formation of peaked electron heating profile at the X point. The localized heating increases with higher guide field, while bulk downstream ion heating is unaffected by the change in the guide field under MAST conditions ($B_t>3B_{rec}$).

  3. Magnetic properties of lanthanoid(III) phthalocyaninato triple-decker complexes in an external magnetic field and electronic transport properties for molecular spintronics

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, K; Yamamoto, K; Breedlove, B K; Yamashita, M [Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578 (Japan); Kajiwara, T [Department of Chemistry, Faculty of Science, Nara Women' s University, Nishi-Machi, Kita-Uoya, Nara 630-8506 (Japan); Takeya, J, E-mail: yamashita@agnus.chem.tohoku.ac.jp [Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaragi 567-0047 (Japan)

    2011-07-06

    Lanthanoid phthalocyaninato complexes of Dy{sub 2}(obPc){sub 3} (1) and Tb{sub 2}(obPc){sub 3} (2) are shown to be a single-molecule magnet. The relationships among the magnetic relaxation properties of 1 in a direct current (dc) magnetic field in comparison to 2 and the electronic properties of a cast film are discussed.

  4. GGA+U investigations of impurity d-electrons effects on the electronic and magnetic properties of ZnO

    KAUST Repository

    Ul Haq, Bakhtiar

    2014-08-01

    Stimulation of novel features in ZnO by impurity electrons has attracted a remarkable attention of researchers from the past decade. Consequently, ZnO has found several applications in the field of spintronics and optoelectronics. We report, the effect of 3d-(V, Ag) electrons on the properties of ZnO in stable wurtzite (WZ) and metastable zincblende (ZB) phase using the density functional theory. Introduction of V-3d electrons was found to induce a high magnetic moment value of 5.22 in WZ and 3.26 in the ZB phase, and moreover transform the semiconductor character of ZnO into a metallic nature. Ag-d electrons result in the p-type half-metallic nature of ZnO with a weak ferromagnetic background. Our calculations for ground-state magnetic ordering show that ZnO in the presence of impure 3d-(V, Ag) electrons favors ferromagnetic ordering, and obey the double exchange mechanism. However, impurity atoms have very marginal effect on the lattice parameters of ZnO, thereby exposing its potential to absorb the impurity atoms in high concentration. © 2014 Elsevier B.V. All rights reserved.

  5. First-principles study on electronic and magnetic properties of (Mn,Fe)-codoped ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Huawei [Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education, Beijing 100876 (China); Lu, Pengfei, E-mail: photon.bupt@gmail.com [Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education, Beijing 100876 (China); Cai, Ningning; Zhang, Xianlong; Yu, Zhongyuan [Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), Ministry of Education, Beijing 100876 (China); Gao, Tao [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Wang, Shumin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2014-02-15

    First-principle calculations have been performed to investigate the electronic and magnetic properties of (Mn,Fe)-codoped ZnO within the generalized gradient approximation (GGA) and GGA+U schemes. The formation energy of five different configurations is investigated and the ground state is demonstrated to be ferromagnetic ordering. By applying the U correction, the band gap energy of pure ZnO is close to the experimental values, while the ferromagnetic ordering of the ground state remains unchanged. The ferromagnetic stabilization is mediated by double exchange mechanism. In addition, defects corresponding to Zn-vacancy and O-vacancy cannot enhance the ferromagnetism obviously. These results indicate that (Mn,Fe)-codoped ZnO are promising magneto-electronic and spintronic materials. - Highlights: • We have considered 5 different configurations of Mn/Fe codoped bulk ZnO. • The formation energy is calculated to investigate the structural stability. • The double exchange mechanism is responsible for the ferromagnetic behavior. • Defects are not effective method to get room temperature ferromagnetism. • Mn/Fe codoped ZnO are promising ferromagnetic semiconductor materials.

  6. Probing Electronic States of Magnetic Semiconductors Using Atomic Scale Microscopy & Spectroscopy

    Science.gov (United States)

    2013-12-01

    N000140710348 Final Report as of December 2013 Objective: This project was focused on the application of the scanning tunneling microscopy (STM...magnetic atoms on the surface of a superconductor can be used as a versatile platform for creating a topological superconductor . These initial...the application of the scanning tunneling microscopy (STM) to understand the electronic structure of magnetically doped semiconductors and to develop

  7. Electron magnetic resonance and Moessbauer studies on iron doped SnO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Grecu, Maria Nicoleta, E-mail: mgrecu@infim.ro; Constantinescu, Serban Gr.; Ghica, Daniela; Tarabasanu-Mihaila, Doina; Diamandescu, Lucian [National Institute of Materials Physics (Romania)

    2012-03-15

    Iron doped (0.25-7.5% molar) hydrothermal nano-SnO{sub 2} was characterized by electron magnetic resonance (EMR) and Moessbauer spectroscopies. Only a small fraction of transition metal ions are in magnetic ordered state, contrary to the similar crystallographic compound TiO{sub 2}. Temperature dependences of spectra suggest that by increasing iron concentration, or annealing temperature, iron ions migrate to nanoparticles surfaces forming disordered iron oxides.

  8. The magnetic field generated by an electron bound in angular-momentum eigenstates

    CERN Document Server

    Ayuel, K

    1999-01-01

    The magnetic field generated by an electron bound in a spherically symmetric potential is calculated for eigenstates of the orbital and total angular momentum. General expressions are presented for the current density in such states and the magnetic field is calculated through the vector potential, which is obtained from the current density by direct integration. The method is applied to the hydrogen atom, for which we reproduce and extend known results.

  9. Electronic structure and magnetic properties of selected UTX compounds: LDA +U approach

    Energy Technology Data Exchange (ETDEWEB)

    Rusz, Jan; Divis, Martin [Department of Electronic Structures, Charles University, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic)

    2004-09-22

    We present calculations of a set of UTX compounds (where T is a transition metal and X is a p element) in the framework of density functional theory applying the LSDA +U exchange-correlation energy functional. As the parameters U and J for these compounds are not known, we varied them in effort to reproduce experimental uranium magnetic moments. Using the obtained electronic structures we discuss the magnetism and the effects of hybridization. Our results are in improved agreement with experimental findings.

  10. Acoustic solitons in a magnetized quantum electron-positron-ion plasma with relativistic degenerate electrons and positrons pressure

    Science.gov (United States)

    Abdikian, A.; Mahmood, S.

    2016-12-01

    The obliquely nonlinear acoustic solitary propagation in a relativistically quantum magnetized electron-positron (e-p) plasma in the presence of the external magnetic field as well as the stationary ions for neutralizing the plasma background was studied. By considering the dynamic of the fluid e-p quantum and by using the quantum hydrodynamics model and the standard reductive perturbation technique, the Zakharov-Kuznetsov (ZK) equation is derived for small but finite amplitude waves and the solitary wave solution for the parameters relevant to dense astrophysical objects such as white dwarf stars is obtained. The numerical results show that the relativistic effects lead to propagate the electrostatic bell shape structures in quantum e-p plasmas like those in classical pair-ion or pair species for relativistic plasmas. It is also observed that by increasing the relativistic effects, the amplitude and width of the e-p acoustic solitary wave will decrease. In addition, the wave amplitude increases as positron density decreases in magnetized e-p plasmas. It is indicated that by increasing the strength of the magnetic field, the width of the soliton reduces and it becomes sharper. At the end, we have analytically and numerically shown that the pulse soliton solution of the ZK equation is unstable and have traced the dependence of the instability growth rate on electron density. It is found that by considering the relativistic pressure, the instability of the soliton pulse can be reduced. The results can be useful to study the obliquely nonlinear propagation of small amplitude localized structures in magnetized quantum e-p plasmas and be applicable to understand the particle and energy transport mechanism in compact stars such as white dwarfs, where the effects of relativistic electron degeneracy become important.

  11. Electron g-factor in diluted magnetic semiconductor quantum well with parabolic potential in the presence of Rashba effect and magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Babanli, Arif M. [Azerbaijan National Academy of Sciences, Baku (Azerbaijan). Inst. of Physics; Sueleyman Demirel Univ., Isparta (Turkey). Dept. of Physics; Artunc, Ekrem [Sueleyman Demirel Univ., Isparta (Turkey). Dept. of Physics; Kasalak, Turgut F. [Akdeniz Univ., Antalya (Turkey). Dept. of Informatics

    2015-07-01

    We have studied the Rashba spin-orbital effect on a diluted magnetic semiconductor (DMS) quantum well with parabolic potential in the presence of a magnetic field parallel to the z axis, taking into account the Zeeman coupling and the s-d exchange interaction between the carriers and the magnetic ions. We have obtained an analytical expression for the electron energy spectrum, which depends on the magnetic ion concentration, temperature, and strength of magnetic field. By using the obtained energy spectrum, we calculated the electron effective g{sup *}-factor. We have found that effective g{sup *}-factor increases when the magnetic field increases; by increasing the strength of spin-orbit interaction, the electron g{sup *}-factor decreases and by increasing the temperature, the electron g{sup *}-factor increases.

  12. Zero-differential resistance state of two-dimensional electron systems in strong magnetic fields.

    Science.gov (United States)

    Bykov, A A; Zhang, Jing-qiao; Vitkalov, Sergey; Kalagin, A K; Bakarov, A K

    2007-09-14

    We report the observation of a zero-differential resistance state (ZDRS) in response to a direct current above a threshold value I>I th applied to a two-dimensional system of electrons at low temperatures in a strong magnetic field. Entry into the ZDRS, which is not observable above several Kelvins, is accompanied by a sharp dip in the differential resistance. Additional analysis reveals an instability of the electrons for I>I th and an inhomogeneous, nonstationary pattern of the electric current. We suggest that the dominant mechanism leading to the new electron state is a redistribution of electrons in energy space induced by the direct current.

  13. Spacecraft observations and analytic theory of crescent-shaped electron distributions in asymmetric magnetic reconnection

    CERN Document Server

    Egedal, J; Daughton, W; Wetherton, B; Cassak, P A; Chen, L -J; Lavraud, B; Trobert, R B; Dorelli, J; Gershman, D J; Avanov, L A

    2016-01-01

    Supported by a kinetic simulation, we derive an exclusion energy parameter $\\cal{E}_X$ providing a lower kinetic energy bound for an electron to cross from one inflow region to the other during magnetic reconnection. As by a Maxwell Demon, only high energy electrons are permitted to cross the inner reconnection region, setting the electron distribution function observed along the low density side separatrix during asymmetric reconnection. The analytic model accounts for the two distinct flavors of crescent-shaped electron distributions observed by spacecraft in a thin boundary layer along the low density separatrix.

  14. Parallel electric fields are inefficient drivers of energetic electrons in magnetic reconnection

    Science.gov (United States)

    Dahlin, J. T.; Drake, J. F.; Swisdak, M.

    2016-12-01

    We present two-dimensional kinetic simulations, with a broad range of initial guide fields, which isolate the role of parallel electric fields ( E∥ ) in energetic electron production during collisionless magnetic reconnection. In the strong guide field regime, E∥ drives essentially all of the electron energy gains, yet fails to generate an energetic component. We suggest that this is due to the weak energy scaling of particle acceleration from E∥ compared to that of a Fermi-type mechanism responsible for energetic electron production in the weak guide-field regime. This result has important implications for energetic electron production in astrophysical systems and reconnection-driven dissipation in turbulence.

  15. Ambipolar transport via trapped-electron whistler instability along open magnetic field lines.

    Science.gov (United States)

    Guo, Zehua; Tang, Xian-Zhu

    2012-09-28

    An open field line plasma is bounded by a chamber wall which intercepts the magnetic field. Steady state requires an upstream plasma source balancing the particle loss to the boundary. In cases where the electrons have a long mean free path, ambipolarity in parallel transport critically depends on collisionless detrapping of the electrons via wave-particle interaction. The trapped-electron whistler instability, whose nonlinear saturation produces a spectrum of whistler waves that is responsible for the electron detrapping flux, is shown to be an unusually robust kinetic instability, which is essential to the universality of the ambipolar constraint in plasma transport.

  16. First results of electron cyclotron emission measurements at the GDT magnetic mirror

    CERN Document Server

    Shalashov, A G; Gospodchikov, E D; Lubyako, L V; Yakovlev, D V; Bagryansky, P A

    2016-01-01

    This paper summarizes the results of experiments on electron cyclotron emission (ECE) measurements at the fundamental harmonic recently performed at the axially symmetric magnetic mirror device GDT (Budker Institute, Novosibirsk). New ECE diagnostics is installed to facilitate the successful electron cyclotron resonance heating experiment and operates in the vicinity of the heating frequency of 54.5 GHz. Besides expected emission of thermal electrons, a clearly resolved non-thermal ECE is observed indicating the presence of suprathermal electrons driven by high-power microwave heating. The particulars of plasma emission are studied experimentally in a broad range of discharge scenarios.

  17. Ground State Transitions of Four-Electron Quantum Dots in Zero Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    KANG Shuai; XIE Wen-Fang; LIU Yi-Ming; SHI Ting-Yun

    2008-01-01

    In this paper, we study four electrons confined in a parabolic quantum dot in the absence of magnetic field, by the exact diagonalization method. The ground-state electronic structures and orbital and spin angular momenta transitions as a function of the confined strength are investigated. We find that the confinement may cause accidental degeneracies between levels with different low-lying states and the inversion of the energy values. The present results are useful to understand the optical properties and internal electron-electron correlations of quantum dot materials.

  18. Modeling electron transport in the presence of electric and magnetic fields.

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Wesley C.; Drumm, Clifton Russell; Pautz, Shawn D.; Turner, C. David

    2013-09-01

    This report describes the theoretical background on modeling electron transport in the presence of electric and magnetic fields by incorporating the effects of the Lorentz force on electron motion into the Boltzmann transport equation. Electromagnetic fields alter the electron energy and trajectory continuously, and these effects can be characterized mathematically by differential operators in terms of electron energy and direction. Numerical solution techniques, based on the discrete-ordinates and finite-element methods, are developed and implemented in an existing radiation transport code, SCEPTRE.

  19. Magnetic susceptibility and electron magnetic resonance study of monovalent potassium doped manganites Pr{sub 0.6}Sr{sub 0.4−x}K{sub x}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Thaljaoui, R., E-mail: thaljaoui@gmail.com [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B.P. 1171, 3000 Sfax (Tunisia); Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Department of Chemistry, University of Warsaw, Al. Żwirki i Wigury 101, 02-089 Warsaw (Poland); Pękała, K. [Faculty of Physics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw (Poland); Pękała, M. [Department of Chemistry, University of Warsaw, Al. Żwirki i Wigury 101, 02-089 Warsaw (Poland); Boujelben, W. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B.P. 1171, 3000 Sfax (Tunisia); Szydłowska, J. [Department of Chemistry, University of Warsaw, Al. Żwirki i Wigury 101, 02-089 Warsaw (Poland); Fagnard, J.-F.; Vanderbemden, P. [SUPRATEC, Department of Electrical Engineering and Computer Science (B28), University of Liege (Belgium); Cheikhrouhou, A. [Laboratoire de Physique des Matériaux, Faculté des Sciences de Sfax, Université de Sfax, B.P. 1171, 3000 Sfax (Tunisia)

    2013-12-15

    Highlights: •Orthorhombic monovalent doped manganites Pr0.6Sr0.4-xKxMnO3 (x = 0.05 to 0.2). •Unit cell volume decreases with K content. •Curie temperature decreases with K content. •Electron magnetic resonance determines low temperature limit of paramagnetic phase. -- Abstract: The monovalent potassium doped manganites Pr{sub 0.6}Sr{sub 0.4−x}K{sub x}MnO{sub 3} (x = 0.05–0.2) are characterized using the complementary magnetic susceptibility and electron resonance methods. In paramagnetic phase the temperature variations of the inverse magnetic susceptibility and the inverse intensity of resonance signal obey the Curie–Weiss law. A similarity in temperature variation of resonance signal width and the adiabatic polaron conductivity points to the polaron mechanism controlling the resonance linewidth. The low temperature limit of the pure paramagnetic phase is determined from the electron resonance spectra revealing the mixed phase spread down to the Curie temperature.

  20. Electron Beam Dose Distribution in the Presence of Non-Uniform Magnetic Field

    Directory of Open Access Journals (Sweden)

    Mohamad Javad Tahmasebi-Birgani

    2014-04-01

    Full Text Available Introduction Magnetic fields are capable of altering the trajectory of electron beams andcan be used in radiation therapy.Theaim of this study was to produce regions with dose enhancement and reduction in the medium. Materials and Methods The NdFeB permanent magnets were arranged on the electron applicator in several configurations. Then, after the passage of the electron beams (9 and 15 MeV Varian 2100C/D through the non-uniform magnetic field, the Percentage Depth Dose(PDDs on central axis and dose profiles in three depths for each energy were measured in a 3D water phantom. Results For all magnet arrangements and for two different energies, the surface dose increment and shift in depth of maximum dose (dmax were observed. In addition, the pattern of dose distribution in buildup region was changed. Measurement of dose profile showed dose localization and spreading in some other regions. Conclusion The results of this study confirms that using magnetic field can alter the dose deposition patterns and as a result can produce dose enhancement as well as dose reduction in the medium using high-energy electron beams. These effects provide dose distribution with arbitrary shapes for use in radiation therapy.

  1. Probing Nanoscale Electronic and Magnetic Interaction with Scanning Tunneling Spectroscopy

    DEFF Research Database (Denmark)

    Bork, Jakob

    coverage the silver preferably nucleates on top of the bilayer high cobalt islands compared to directly on the Cu(111) substrate. Furthermore, the silver forms a combination of a reconstruction and a Moire pattern which is investigated with low-energy electron diraction and spectroscopic STM mapping at 6....... The heterostructure is found to have very interesting electronic properties. The d-related state from the now buried cobalt island is visible through the silver capping layer, but the silver Moire pattern modulates the spin-polarized cobalt d-related state in amplitude, energy position and width. This is related......, but the Fano line ii shape changes continuously from a dip to a peak. In the antiferromagnetic regime, inelastic spin-ip excitations reveal a splitting with a continuous increase in energy levels when pushing the atoms further together. This is supported by numerical renormalization group calculations...

  2. Extreme electron-phonon coupling in magnetic rubidium sesquioxide

    Science.gov (United States)

    de Groot, Robert; Attema, Jisk; Riyadi, S.; Blake, Greame; de Wijs, Gilles; Palstra, Thomas

    2008-03-01

    Rb2O3 is a black, opaque oxide. Early work suggests that the stability range of the sesquioxide phase in the rubidium-oxygen phase diagram is rather broad. Rb2O3 remains cubic down to the lowest temperature measured (5 K). The oxygens form dumbbells with interatomic distances in between those of peroxide and superoxide anions, and strong athermal motion persists down to low temperatures. [1] Electronic-structure calculations show that the dynamics at low temperature is caused by 6 phonon modes of zero frequency, which induce a very strong electron-phonon interaction. The softness of half of these modes is suppressed by the application of pressure. Calculated using the average oxygen positions, rubidium sesquioxide is a half-metallic ferromagnet. [2] [1] CR CHIM (11-13): 591-594 NOV 1999[2] JACS 127 (46): 16325-16328 NOV 23 2005

  3. A study of magnetic properties of hard and soft magnetic materials by Lorentz transmission electron microscopy and magnetic x-ray circular dichroism

    CERN Document Server

    Pickford, R A

    2001-01-01

    iron spin and orbital magnetic moments were found to decrease with increasing iron content. In collaboration with CEA Saclay, Paris, a set of cobalt elements were patterned by electron beam lithography. The elements were designed to isolate domain walls and to monitor their movement in an applied field. The shape anisotropy of the element was found to be too large for the insitu magnetic field to flip the magnetisation. The domain walls found in the as received magnetic state were associated with defects in the structure of the element. The magnetisation process was compared to micromagnetic simulations, A further study of magnetic elements was made to study the competition of anisotropy in patterned cobalt dots. The shape anisotropy was calculated and the crystalline anisotropy of the cobalt film was measured. The dots (rectangles) were patterned so that the shape anisotropy was comparable to the crystalline anisotropy of the cobalt. The dots were patterned at 45 degrees to the crystalline anisotropy. This t...

  4. Quantitative in situ magnetization reversal studies in Lorentz microscopy and electron holography.

    Science.gov (United States)

    Rodríguez, L A; Magén, C; Snoeck, E; Gatel, C; Marín, L; Serrano-Ramón, L; Prieto, J L; Muñoz, M; Algarabel, P A; Morellon, L; De Teresa, J M; Ibarra, M R

    2013-11-01

    A generalized procedure for the in situ application of magnetic fields by means of the excitation of the objective lens for magnetic imaging experiments in Lorentz microscopy and electron holography is quantitatively described. A protocol for applying magnetic fields with arbitrary in-plane magnitude and orientation is presented, and a freeware script for Digital Micrograph(™) is provided to assist the operation of the microscope. Moreover, a method to accurately reconstruct hysteresis loops is detailed. We show that the out-of-plane component of the magnetic field cannot be always neglected when performing quantitative measurements of the local magnetization. Several examples are shown to demonstrate the accuracy and functionality of the methods. © 2013 Elsevier B.V. All rights reserved.

  5. Electron Heating, Magnetic Field Amplification, and Cosmic Ray Precursor Length at Supernova Remnant Shocks

    CERN Document Server

    Laming, J Martin; Ghavamian, Parviz; Rakowski, Cara

    2014-01-01

    We investigate the observability, by direct and indirect means, of a shock precursor arising from magnetic field amplification by cosmic rays. We estimate the depth of such a precursor under conditions of nonresonant amplification, which can provide magnetic field strengths comparable to those inferred for supernova remnants. Magnetic field generation occurs as the streaming cosmic rays induce a plasma return current, and may be quenched either by nonresonant or resonant channels. In the case of nonresonant saturation, the cosmic rays become magnetized and amplification saturates at higher magnetic fields. The precursor can extend out to $10^{17} - 10^{18}$ cm and is potentially detectable. If resonant saturation occurs, the cosmic rays are scattered by turbulence and the precursor length will likely be much smaller. The dependence of precursor length on shock velocity has implications for electron heating. In the case of resonant saturation, this dependence is similar to that in the more familiar resonantly ...

  6. Ion and electron heating characteristics of magnetic reconnection in a two flux loop merging experiment.

    Science.gov (United States)

    Ono, Y; Tanabe, H; Hayashi, Y; Ii, T; Narushima, Y; Yamada, T; Inomoto, M; Cheng, C Z

    2011-10-28

    Characteristics of the high-power reconnection heating were measured for the first time directly by two-dimensional measurements of ion and electron temperatures. While electrons are heated mainly inside the current sheet by the Ohmic heating power, ions are heated mainly by fast shock or viscosity damping of the reconnection outflow in the two downstream areas. The magnetic reconnection converts the energy of reconnecting magnetic field B(p) mostly to the ion thermal energy, indicating that the reconnection heating energy is proportional to B(p)(2).

  7. Electronic and magnetic properties of the spinel semiconductor CdCr2Se4

    Science.gov (United States)

    Continenza, Alessandra; de Pascale, Teresa; Meloni, Franco; Serra, Marina

    1994-01-01

    We present a first-principles study of the electronic and magnetic properties of the chromium spinel CdCr2Se4, a ferromagnetic semiconductor, which, for its interesting magnetic and electric properties has been the object of many experimental studies. Using calculations based on the full-potential linearized augmented plane wave relativistic scheme we are able to reproduce the structural equilibrium properties and to explain many of the features measured by resonant photoemission spectroscopy. In particular, we analyze the contribution of the Cr 3d electrons in a density-of-states study including the two spin orientations and a comparison with the binary analog CdSe.

  8. Research on Proximity Magnetic Field Influence in Measuring Error of Active Electronic Current Transformers

    Directory of Open Access Journals (Sweden)

    Wu Weijiang

    2016-01-01

    Full Text Available The principles of the active electronic current transformer (ECT are introduced, and the mechanism of how a proximity magnetic field can influence the measuring of errors is analyzed from the perspective of the sensor section of the ECT. The impacts on active ECTs created by three-phase proximity magnetic field with invariable distance and variable distance are simulated and analyzed. The theory and simulated analysis indicate that the active ECTs are sensitive to proximity magnetic field under certain conditions. According to simulated analysis, a product structural design and the location of transformers at substation sites are suggested for manufacturers and administration of power supply, respectively.

  9. Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

    Energy Technology Data Exchange (ETDEWEB)

    Lollobrigida, V. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F. [Istituto Nazionale di Ricerca Metrologica (INRIM), I-10135 Torino (Italy); Borgatti, F. [CNR, Istituto per lo Studio dei Materiali Nanostrutturati (ISMN), I-40129 Bologna (Italy); Torelli, P.; Panaccione, G. [CNR, Istituto Officina dei Materiali (IOM), Lab. TASC, I-34149 Trieste (Italy); Tortora, L. [Laboratorio di Analisi di Superficie, Dipartimento di Matematica e Fisica, Università Roma Tre, I-00146 Rome (Italy); Dipartimento di Ingegneria Meccanica, Università Tor Vergata, I-00133 Rome (Italy); Stefani, G.; Offi, F. [Dipartimento di Scienze, Università Roma Tre, I-00146 Rome (Italy)

    2014-05-28

    We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

  10. Electron beam focusing in a racetrack microtron by means of rotated two-sector dipole magnets

    Science.gov (United States)

    Delhez, J. L.; Webers, G. A.; Botman, J. I. M.; Hagedoorn, H. L.; Muzio, D.; Timmermans, C. J.

    1992-05-01

    We present an unconventional method of electron beam focusing in a racetrack microtron (RTM). The RTM bending magnets have a two-sector shape (valley and hill) and are slightly rotated in their median plane in order to guarantee closed orbits. Then, isochronism is automatically fulfilled. Comparison between this new arrangement and a previous three-sector design, inspired by Froelich [1], shows that the focusing properties are greatly improved, e.g. regarding beam acceptance and construction sensitivity. We will give a detailed description of the two-sector layout, make a comparison with the three-sector magnet (acceptance and sensitivity) and give magnet parameters for optimum performance.

  11. Electronic and magnetic structure of GaxFe1-x thin films

    Energy Technology Data Exchange (ETDEWEB)

    Arenholz, E.; van der Laan, G.; McClure, A.; Idzerda, Y.

    2010-09-08

    The electronic as well as magnetic properties of Ga{sub x}Fe{sub 1-x} films were studied by soft x-ray measurements. Using x-ray magnetic circular dichroism the Fe majority-spin band was found to be completely filled for x {approx} 0.3. With further enhanced Ga content, the Fe moment as well as the angular dependence of the x-ray magnetic linear dichroism decrease strongly, which we attribute to the formation of D0{sub 3} precipitates. Moreover, the magnetocrystalline anisotropy drops significantly.

  12. Terahertz Induced Photoconductivity of 2D Electron System in HEMT at Low Magnetic Field

    OpenAIRE

    Chebotarev, Andrey; Chebotareva, Galina

    2004-01-01

    A few results of our study of two-dimensional electron system (2DES) in low magnetic fields in GaAs/GaAlAs heterostructures by cyclotron resonance (CR) and photoconductivity techniques are presented. We have first discovered "CR-vanishing effect"in 2DES as well-defined crevasse on CR line in low magnetic fields, when Hall resistance is not quantized. "CR-vanishing effect" indicates vanishing longitudinal resistance & conductivity in these magnetic fields. Observed "CR-vanishing effect" demons...

  13. First-principles studies of BN sheets with absorbed transition metal single atoms or dimers: stabilities, electronic structures, and magnetic properties.

    Science.gov (United States)

    Ma, Dongwei; Lu, Zhansheng; Ju, Weiwei; Tang, Yanan

    2012-04-11

    BN sheets with absorbed transition metal (TM) single atoms, including Fe, Co, and Ni, and their dimers have been investigated by using a first-principles method within the generalized gradient approximation. All of the TM atoms studied are found to be chemically adsorbed on BN sheets. Upon adsorption, the binding energies of the Fe and Co single atoms are modest and almost independent of the adsorption sites, indicating the high mobility of the adatoms and isolated particles to be easily formed on the surface. However, Ni atoms are found to bind tightly to BN sheets and may adopt a layer-by-layer growth mode. The Fe, Co, and Ni dimers tend to lie (nearly) perpendicular to the BN plane. Due to the wide band gap of the pure BN sheet, the electronic structures of the BN sheets with TM adatoms are determined primarily by the distribution of TM electronic states around the Fermi level. Very interesting spin gapless semiconductors or half-metals can be obtained in the studied systems. The magnetism of the TM atoms is preserved well on the BN sheet, very close to that of the corresponding free atoms and often weakly dependent on the adsorption sites. The present results indicate that BN sheets with adsorbed TM atoms have potential applications in fields such as spintronics and magnetic data storage due to the special spin-polarized electronic structures and magnetic properties they possess.

  14. Defect induced electronic states and magnetism in ball-milled graphite.

    Science.gov (United States)

    Milev, Adriyan; Dissanayake, D M A S; Kannangara, G S K; Kumarasinghe, A R

    2013-10-14

    The electronic structure and magnetism of nanocrystalline graphite prepared by ball milling of graphite in an inert atmosphere have been investigated using valence band spectroscopy (VB), core level near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and magnetic measurements as a function of the milling time. The NEXAFS spectroscopy of graphite milled for 30 hours shows simultaneous evolution of new states at ~284.0 eV and at ~290.5 eV superimposed upon the characteristic transitions at 285.4 eV and 291.6 eV, respectively. The modulation of the density of states is explained by evolution of discontinuities within the sheets and along the fracture lines in the milled graphite. The magnetic measurements in the temperature interval 2-300-2 K at constant magnetic field strength show a correlation between magnetic properties and evolution of the new electronic states. With the reduction of the crystallite sizes of the graphite fragments, the milled material progressively changes its magnetic properties from diamagnetic to paramagnetic with contributions from both Pauli and Curie paramagnetism due to the evolution of new states at ~284 and ~290.5 eV, respectively. These results indicate that the magnetic behaviour of ball-milled graphite can be manipulated by changing the milling conditions.

  15. Electron Cloud Generation and Trapping in a Quadrupole Magnet at the Los Alamos Proton Storage Ring

    Energy Technology Data Exchange (ETDEWEB)

    Macek, Robert J.; Browman, Andrew A.; Ledford, John E.; /TechSource, Santa Fe /Los Alamos; Borden, Michael J.; O' Hara, James F.; McCrady, Rodney C.; Rybarcyk, Lawrence J.; Spickermann, Thomas; Zaugg, Thomas J.; /Los Alamos; Pivi, Mauro T.F.; /SLAC

    2008-03-17

    Recent beam physics studies on the two-stream e-p instability at the LANL proton storage ring (PSR) have focused on the role of the electron cloud generated in quadrupole magnets where primary electrons, which seed beam-induced multipacting, are expected to be largest due to grazing angle losses from the beam halo. A new diagnostic to measure electron cloud formation and trapping in a quadrupole magnet has been developed, installed, and successfully tested at PSR. Beam studies using this diagnostic show that the 'prompt' electron flux striking the wall in a quadrupole is comparable to the prompt signal in the adjacent drift space. In addition, the 'swept' electron signal, obtained using the sweeping feature of the diagnostic after the beam was extracted from the ring, was larger than expected and decayed slowly with an exponential time constant of 50 to 100 {micro}s. Other measurements include the cumulative energy spectra of prompt electrons and the variation of both prompt and swept electron signals with beam intensity. Experimental results were also obtained which suggest that a good fraction of the electrons observed in the adjacent drift space for the typical beam conditions in the 2006 run cycle were seeded by electrons ejected from the quadrupole.

  16. TSUBASA (MDS-1) observations of energetic electrons and magnetic field variations in outer radiation belt

    Science.gov (United States)

    Nakamura, M.; Matsuoka, H.; Liu, H.; Koshiishi, H.; Koga, K.; Matsumoto, H.; Goka, T.

    2002-12-01

    We have investigated variations of energetic electrons (> 0.4 MeV) and magnetic field in the radiation belt obtained from the Standard DOse Monitor (SDOM) and the MAgnetoMeter (MAM) of the Space Environment Data Acquisition equipment (SEDA) onboard TSUBASA (the Mission Demonstration Test Satellite (MDS)-1) launched on February 4, 2002. Since TSUBASA is operated in the geostationary transfer orbit, it has provided rare opportunities of directly observing near-equatorial radiation belt plasma particles and magnetic field, having already included several large magnetic storms. The energetic electrons in the outer radiation belt are contributors to the total radiation dose deposited in lightly shielded spacecraft electronics for high altitude orbits and are known to have a drastic variability associated with geomagnetic storm and high speed solar wind streams. The abrupt energetic electron flux decreases in the outside of outer radiation belt show characteristic variations of in situ magnetic field. These observations have implications for the possible mechanisms of the depletion and the following recovery and/or buildup of energetic electrons in the outer radiation belt.

  17. Direct laser acceleration of electrons in a strong azimuthal magnetic field

    Science.gov (United States)

    Wang, Tao; Toncian, Toma; Stark, David; Arefiev, Alexey

    2016-10-01

    Recently published particle-in-cell simulations indicate that a high-intensity laser irradiating an over-critical plasma can induce relativistic transparency and drive a Megatesla magnetic field while propagating into the plasma. At the same time, the quasi-static electric field in this regime is an order of magnitude weaker than the quasi-static magnetic field as a result of ion mobility and the fact that electrons are irradiated by a high intensity laser pulse. We have examined analytically and numerically direct laser acceleration of electrons in such an azimuthal magnetic field. We have considered a general case of a laser beam propagating with a superluminal phase velocity and compared the results to those for a luminal case. Our key finding is that the maximum gamma-factor that can be attained by electrons has a pronounced threshold, with a significant enhancement of the electron energy taking place above the threshold. The threshold is a function of the azimuthal magnetic field and of the initial transverse electron momentum. This work was supported by the National Science Foundation under Grant No. 1632777.

  18. Bifurcated structure of the electron diffusion region in three-dimensional magnetic reconnection.

    Science.gov (United States)

    Liu, Yi-Hsin; Daughton, W; Karimabadi, H; Li, H; Roytershteyn, V

    2013-06-28

    Three-dimensional kinetic simulations of magnetic reconnection reveal that the electron diffusion region is composed of two or more current sheets in regimes with weak magnetic shear angles ϕ≲80°. This new morphology is explained by oblique tearing modes which produce flux ropes while simultaneously driving enhanced current at multiple resonance surfaces. This physics persists into the nonlinear regime leading to multiple electron layers embedded within a larger Alfvénic inflow and outflow. Surprisingly, the thickness of these layers and the reconnection rate both remain comparable to two-dimensional models. The parallel electric fields are supported predominantly by the electron pressure tensor and electron inertia, while turbulent dissipation remains small.

  19. 3D simulations of gyrosynchrotron emission from mildly anisotropic nonuniform electron distributions in symmetric magnetic loops

    CERN Document Server

    Kuznetsov, Alexey A; Fleishman, Gregory D

    2011-01-01

    Microwave emission of solar flares is formed primarily by incoherent gyrosynchrotron radiation generated by accelerated electrons in coronal magnetic loops. The resulting emission depends on many factors, including pitch-angle distribution of the emitting electrons and the source geometry. In this work, we perform systematic simulations of solar microwave emission using recently developed tools (GS Simulator and fast gyrosynchrotron codes) capable of simulating maps of radio brightness and polarization as well as spatially resolved emission spectra. A 3D model of a symmetric dipole magnetic loop is used. We compare the emission from isotropic and anisotropic (of loss-cone type) electron distributions. We also investigate effects caused by inhomogeneous distribution of the emitting particles along the loop. It is found that effect of the adopted moderate electron anisotropy is the most pronounced near the footpoints and it also depends strongly on the loop orientation. Concentration of the emitting particles a...

  20. Debye scale turbulence within the electron diffusion layer during magnetic reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Jara-Almonte, J.; Ji, H. [Center for Magnetic Self-Organization, Max-Planck/Princeton Center for Plasma Physics, Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-03-15

    During collisionless, anti-parallel magnetic reconnection, the electron diffusion layer is the region of both fieldline breaking and plasma mixing. Due to the in-plane electrostatic fields associated with collisionless reconnection, the inflowing plasmas are accelerated towards the X-line and form counter-streaming beams within the unmagnetized diffusion layer. This configuration is inherently unstable to in-plane electrostatic streaming instabilities provided that there is sufficient scale separation between the Debye length λ{sub D} and the electron skin depth c/ω{sub pe}. This scale separation has hitherto not been well resolved in kinetic simulations. Using both 2D fully kinetic simulations and a simple linear model, we demonstrate that these in-plane streaming instabilities generate Debye scale turbulence within the electron diffusion layer at electron temperatures relevant to magnetic reconnection both in the magnetosphere and in laboratory experiments.

  1. Effect of the Electron-Phonon Coupling on Barrier D- Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    XIE Wen-Fang

    2002-01-01

    The influence of the electron-phonon coupling on the energy of low-lying states of the barrier D- center,which consists of a positive ion located on the z-axis at a distance from the two-dimensional quantum dot plane and two electrons in the dot plane bound by the ion, is investigated at arbitrary strength of magnetic field by making use of the method of few-body physics. Discontinuous ground-state energy transitions induced by the magnetic field are reported.The dependence of the binding energy of the D- ground state on the quantum dot radius is obtained. A considerable enhancement of the binding is found for the D- ground state, which results from the confinement of electrons and electron-phonon coupling.

  2. Analysis of drifting electron concentration in a self-magnetically insulated ion diode

    Science.gov (United States)

    Pushkarev, A. I.; Pak, V. G.

    2015-02-01

    The drifting electron concentration in a self-magnetically insulated ion diode is analyzed using a TEMP-4M accelerator operating in a double bipolar pulse regime with the first pulse (300-600 ns and 150-200 kV) being negative and the second (120 ns and 250-300 kV) being positive. The electron concentration in the drift region is shown to be 1013-1014 cm-3. It is established that the Lorentz force acting on electrons in crossed electric and magnetic fields is 150-200 times greater than the Coulomb repulsion force, which ensures a higher electron concentration in the drift region as compared with the space charge region.

  3. Experimental demonstration of the role of electron pressure in fast magnetic reconnection with a guide field

    Science.gov (United States)

    Fox, W.; Sciortino, F.; von Stechow, A.; Jara-Almonte, J.; Yoo, J.; Ji, H.; Yamada, M.

    2016-10-01

    We report detailed laboratory observations of the structure of reconnection current sheets in a two-fluid plasma regime with a guide magnetic field, conducted on the Magnetic Reconnection Experiment. We observe in the laboratory for the first time the quadrupolar electron pressure variation in the ion-diffusion region, as originally predicted by extended MHD simulation. We quantitatively analyze the parallel and perpendicular force balance, and observe the projection of the electron pressure gradient parallel to the B field balances the parallel electric field. The resulting cross-field electron jets in the reconnection layer are diamagnetic in origin. Electron density variations are observed to dominate temperature variations and may provide a new diagnostic of reconnection with finite guide field for fusion experiments and spacecraft missions. Supported by Max-Planck Princeton Center for Plasma Physics.

  4. Electron acoustic waves in a magnetized plasma with kappa distributed ions

    Energy Technology Data Exchange (ETDEWEB)

    Devanandhan, S.; Lakhina, G. S. [Indian Institute of Geomagnetism, Navi Mumbai (India); Singh, S. V. [Indian Institute of Geomagnetism, Navi Mumbai (India); School of Physics, University of Kwazulu-Natal, Durban (South Africa); Bharuthram, R. [University of the Western Cape, Bellville (South Africa)

    2012-08-15

    Electron acoustic solitary waves in a two component magnetized plasma consisting of fluid cold electrons and hot superthermal ions are considered. The linear dispersion relation for electron acoustic waves is derived. In the nonlinear regime, the energy integral is obtained by a Sagdeev pseudopotential analysis, which predicts negative solitary potential structures. The effects of superthermality, obliquity, temperature, and Mach number on solitary structures are studied in detail. The results show that the superthermal index {kappa} and electron to ion temperature ratio {sigma} alters the regime where solitary waves can exist. It is found that an increase in magnetic field value results in an enhancement of soliton electric field amplitude and a reduction in soliton width and pulse duration.

  5. Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

    CERN Document Server

    Wang, Yi; Yang, Zhiyong; Zhang, Huang; Ding, Hengsong; Yang, Anmin; Wang, Minhong

    2016-01-01

    The energy-spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator is measured using the method of energy dispersion in the magnetic field. A sector magnet is applied for energy analyzing of the electron beam, which has a bending radius of 300 mm and a deflection angle of 90 degrees. For each pulse, both the time-resolved and the integral images of the electron position at the output port of the bending beam line are recorded by a streak camera and a CCD camera, respectively. Experimental results demonstrate an energy-spread of less than +-2.0% for the electron pulses. The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.

  6. Influence of the Hall effect and electron inertia in collisionless magnetic reconnection

    CERN Document Server

    Andrés, Nahuel; Gómez, Daniel

    2015-01-01

    We study the role of the Hall current and electron inertia in collisionless magnetic reconnection within the framework of full two-fluid MHD. At spatial scales smaller than the electron inertial length, a topological change of magnetic field lines exclusively due to electron inertia becomes possible. Assuming stationary conditions, we derive a theoretical scaling for the reconnection rate, which is simply proportional to the Hall parameter. Using a pseudo-spectral code with no dissipative effects, our numerical results confirm this theoretical scaling. In particular, for a sequence of different Hall parameter values, our numerical results show that the width of the current sheet is independent of the Hall parameter while its thickness is of the order of the electron inertial range, thus confirming that the stationary reconnection rate is proportional to the Hall parameter.

  7. Three-Dimensional Simulations of Electron Beams Focused by Periodic Permanent Magnets

    Science.gov (United States)

    Kory, Carol L.

    1999-01-01

    A fully three-dimensional (3D) model of an electron beam focused by a periodic permanent magnet (PPM) stack has been developed. First, the simulation code MAFIA was used to model a PPM stack using the magnetostatic solver. The exact geometry of the magnetic focusing structure was modeled; thus, no approximations were made regarding the off-axis fields. The fields from the static solver were loaded into the 3D particle-in-cell (PIC) solver of MAFIA where fully 3D behavior of the beam was simulated in the magnetic focusing field. The PIC solver computes the time-integration of electromagnetic fields simultaneously with the time integration of the equations of motion of charged particles that move under the influence of those fields. Fields caused by those moving charges are also taken into account; thus, effects like space charge and magnetic forces between particles are fully simulated. The electron beam is simulated by a number of macro-particles. These macro-particles represent a given charge Q amounting to that of several million electrons in order to conserve computational time and memory. Particle motion is unrestricted, so particle trajectories can cross paths and move in three dimensions under the influence of 3D electric and magnetic fields. Correspondingly, there is no limit on the initial current density distribution of the electron beam, nor its density distribution at any time during the simulation. Simulation results including beam current density, percent ripple and percent transmission will be presented, and the effects current, magnetic focusing strength and thermal velocities have on beam behavior will be demonstrated using 3D movies showing the evolution of beam characteristics in time and space. Unlike typical beam optics models, this 3D model allows simulation of asymmetric designs such as non- circularly symmetric electrostatic or magnetic focusing as well as the inclusion of input/output couplers.

  8. Magnetic induction technique for mapping vertical conductive fractures: electronic design

    Energy Technology Data Exchange (ETDEWEB)

    Landt, J.A.; Koelle, A.R.; Trump, M.A.; Nickell, J.D. Jr.

    1978-09-01

    This report is the last in a series that describes the preliminary design of an instrument capable of mapping conductive fractures deep below the surface of the earth. Earlier reports dealt with theoretical analysis, the general status of the instrument development, and materials vendor searches. Here, attention is focused on the electronics design and prototype hardware to perform the mapping task. A phase-sensitive detector is described that has a sensitivity in the tens of nanovolts. Coil-switching circuitry is also described, as well as a downhole data link tailor-made for this particular instrument's needs.

  9. Dynamical nonlocal coherent-potential approximation for itinerant electron magnetism.

    Science.gov (United States)

    Rowlands, D A; Zhang, Yu-Zhong

    2014-11-26

    A dynamical generalisation of the nonlocal coherent-potential approximation is derived based upon the functional integral approach to the interacting electron problem. The free energy is proven to be variational with respect to the self-energy provided a self-consistency condition on a cluster of sites is satisfied. In the present work, calculations are performed within the static approximation and the effect of the nonlocal physics on the formation of the local moment state in a simple model is investigated. The results reveal the importance of the dynamical correlations.

  10. Studies of suprathermal electron loss in the magnetic ripple of Tore Supra

    Energy Technology Data Exchange (ETDEWEB)

    Basiuk, V.; Lipa, M.; Martin, G.; Chantant, M.; Guilhem, D.; Imbeaux, F.; Mitteau, R.; Peysson, Y.; Surle, F. [Association Euratom-CEA sur la fusion, CEA Cadarache, 13108 St. Paul-Lez-Durance (France)

    2000-03-01

    A new prototype of protection against fast electron trapped in the magnetic ripple was installed on Tore-Supra in 1998. It was designed to support the high flux of fast electron generated by lower hybrid in the CIEL project (up to 6 MW/m{sup 2}) during steady state experiments. So it is actively cooled and allows a direct measurement of the energy lost in the ripple. (author)

  11. Ion acoustic solitons and supersolitons in a magnetized plasma with nonthermal hot electrons and Boltzmann cool electrons

    Energy Technology Data Exchange (ETDEWEB)

    Rufai, O. R., E-mail: rajirufai@gmail.com; Bharuthram, R., E-mail: rbharuthram@uwc.ac.za [University of the Western Cape, Belville (South Africa); Singh, S. V., E-mail: satyavir@iigs.iigm.res.in; Lakhina, G. S., E-mail: lakhina@iigs.iigm.res.in [Indian Institute of Geomagnetism, New Panvel (W), Navi Mumbai (India)

    2014-08-15

    Arbitrary amplitude, ion acoustic solitons, and supersolitons are studied in a magnetized plasma with two distinct groups of electrons at different temperatures. The plasma consists of a cold ion fluid, cool Boltzmann electrons, and nonthermal energetic hot electrons. Using the Sagdeev pseudo-potential technique, the effect of nonthermal hot electrons on soliton structures with other plasma parameters is studied. Our numerical computation shows that negative potential ion-acoustic solitons and double layers can exist both in the subsonic and supersonic Mach number regimes, unlike the case of an unmagnetized plasma where they can only exist in the supersonic Mach number regime. For the first time, it is reported here that in addition to solitions and double layers, the ion-acoustic supersoliton solutions are also obtained for certain range of parameters in a magnetized three-component plasma model. The results show good agreement with Viking satellite observations of the solitary structures with density depletions in the auroral region of the Earth's magnetosphere.

  12. Electronic and magnetic functions of nanographene-based host-guest system

    Science.gov (United States)

    Enoki, Toshiaki

    2009-03-01

    The electronic structure of nanographene having open edges crucially depends on its edge shape. According to theoretical predictions, nanographene has nonbonding π-electron state (edge state) localized in zigzag edges. We investigated the electronic structure of graphene edges, the magnetism of the edge-state spins in nanographene and the effect of host-guest interaction on the magnetism. For magnetic investigations, we employed nanoporous activated carbon fiber (ACF) having a 3D disordered network of nanographite domains, each of which is a stack of 3-4 nanographene sheets. STM/STS investigations of hydrogen-terminated graphene edges confirm the presence of edge states around zigzag edges, in good agreement with theoretical works. The feature of the edge state depends on the detailed geometry of the edge structures. The magnetism of nanographene in ACF has a ferrimagnetism feature with a net magnetic moment, for which the cooperation of ferromagnetic intra-zigzag-edge and ferromagntic/antiferromagnetic inter-zigzag-edge interactions is responsible. Heat-treatment, which induces an insulator-metal transition, brings about spin glass state of the edge-state spins in the vicinity of the transition. Physisorption of guest species such as water, organic molecules, rare gas in the ACF nanopores generates a high-spin/low-spin magnetic switching phenomenon, in which a discontinuous reduction of the magnetic moment takes place. This is explained in terms of the strengthening of the inter-graphene-sheet antiferromagnetic interaction, which is induced by the mechanical compression of nanographite domains by the condensed guest molecules. The magnetic oxygen molecules physisorbed in the nanopores work seriously to decrease the magnetoresistance in ACF as a consequence of the interaction between the oxygen molecule spins and edge-state spins.

  13. Electronic Energy Band and Transport Properties in Monolayer Graphene with Periodically Modulated Magnetic Vector Potential and Electrostatic Potential

    Institute of Scientific and Technical Information of China (English)

    刘正方; 伍清萍; 刘念华

    2012-01-01

    We investigated the electronic energy band and transport features of graphene superlattice with periodically modulated magnetic vector potential and electrostatic potential. It is found that both parallel magnetic vector potential and electrostatic potential can decisively shift Dirac point in a different way, which may be an efficient way to achieve electron or hole filter. We a/so find that applying modulated parallel and anti-parallel magnetic vector potential to the electrons can efficiently change electronic states between pass and stop states, which can be useful in designing electron or hole switches and lead to large magneto-resistance.

  14. BRIEF COMMUNICATION: Electron acceleration by whistler-mode waves around the magnetic null during 3D reconnection

    Science.gov (United States)

    Xiao, Fuliang; Zong, Qiugang; Pu, Zuyin; Su, Zhenpeng; Cao, Jinbin; He, Jiansen; Wang, Yongfu; Zheng, Huinan

    2010-05-01

    The magnetic field configuration around a magnetic null pair and its associated electron behavior during 3D magnetic reconnection have recently been reported from in situ observations. Electrons are suggested to be temporarily trapped in the central reconnection region as indicated by an electron density peak observed near the magnetic null (He J-S et al 2008 Geophys. Res. Lett. 35 L14104). It is highly interesting that energetic electron beams of a few kiloelectronvolts are found to be related to the magnetic null structure. However, the acceleration mechanism is still not fully understood. In this paper, we show that strong whistler-mode electromagnetic waves are indeed found around the magnetic null. Further we propose a new electron acceleration scenario of trapped electrons near the magnetic null points driven by the whistler-mode waves, which is confirmed by numerical results. It is demonstrated that whistler waves can enhance the phase space density (PSD) of electrons for energies of ~2 keV by a factor of 100 at lower pitch angles very rapidly, typically within 2 s. The accelerated electrons may escape from the loss cone of the magnetic cusp mirrors around the magnetic null, leading to the observed energetic beams.

  15. Partial magnetic order in the itinerant-electron magnet MnSi

    Indian Academy of Sciences (India)

    L Pintschovius; D Reznik; C Pfleiderer; H v Löhneysen

    2004-07-01

    MnSi is an itinerant ferromagnet with a long-wavelength helical modulation of the spin structure. Macroscopic measurements suggest that the ordering temperature c is reduced with increasing pressure from c = 30 K at = 0 to zero at the critical pressure c = 14.6 kbar. Resistivity measurements show that MnSi enters a non-Fermi liquid state at c, which remains to be understood. Neutron scattering techniques have been used to investigate the magnetic structure at and above c, i.e. triple-axis spectrometry and small angle neutron scattering. Surprisingly, sizeable quasi-static moments were found to survive to pressures considerably above c. They are, however, organized in a highly unusual way such that the magnetic Bragg reflections are sharp in the longitudinal direction but are very broad in the transverse direction, implying a partial magnetic order that was never seen before.

  16. A proline-based aminophenol ligand: synthesis, iron complexation, magnetic, electronic and redox investigation.

    Science.gov (United States)

    Sheykhi, Hamid; Safaei, Elham

    2014-01-24

    A new proline-based aminophenol ligand was synthesized by a convenient procedure. The ligand was characterized by (1)H NMR, (13)C NMR and IR spectroscopies, elemental analysis and optical activity measurements. Mononuclear iron(III) complex (FeL(Pro)) of this ligand was synthesized and characterized by IR, UV-vis, ESI-MS, magnetic susceptibility studies and cyclic voltammetry techniques. The equilibrium formation constant of FeL(Pro) and the pure UV-vis spectral profile of the complex was determined by multivariate hard modeling method. The molecular structure of FeL(Pro) determined by ESI-MS consist of two aminophenolate ligands. The variation of magnetic susceptibility with temperature indicates paramagnetic iron(III) in the monomeric complex. FeL(Pro) complex undergo metal-centered reduction, and ligand-centered oxidation. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Improved $\\alpha^4$ Term of the Electron Anomalous Magnetic Moment

    CERN Document Server

    Kinoshita, T

    2006-01-01

    We report a new value of electron $g-2$, or $a_e$, from 891 Feynman diagrams of order $\\alpha^4$. The FORTRAN codes of 373 diagrams containing closed electron loops have been verified by at least two independent formulations. For the remaining 518 diagrams, which have no closed lepton loop, verification by a second formulation is not yet attempted because of the enormous amount of additional work required. However, these integrals have structures that allow extensive cross-checking as well as detailed comparison with lower-order diagrams through the renormalization procedure. No algebraic error has been uncovered for them. The numerical evaluation of the entire $\\alpha^4$ term by the integration routine VEGAS gives $-1.7283 (35) (\\alpha/\\pi)^4$, where the uncertainty is obtained by careful examination of error estimates by VEGAS. This leads to $a_e = 1 159 652 175.86 (0.10) (0.26) (8.48) \\times 10^{-12}$, where the uncertainties come from the $\\alpha^4$ term, the estimated uncertainty of $\\alpha^5$ term, and ...

  18. Scattering-induced quantum correlation in electronic waveguides with static magnetic impurities

    Science.gov (United States)

    Ghanbari-Adivi, E.; Soltani, M.; Alami, Z.; Sheikhali, M.

    2016-10-01

    Entanglement generation due to low-energy scattering of the transporting electrons in an electronic waveguide by a quantum dot magnetic impurity is theoretically investigated. The transverse confining potential of the waveguide is considered as a two-dimensional harmonic potential, and the interaction of the electron with the impurity is described by a zero-range pseudopotential modulated by an Ising or a Heisenberg spin interaction. Our calculation shows that the scattering process leads to creation of a considerable amount of entanglement in the state of the reflected and transmitted electrons. The situation is extended to the scattering of the electrons by two well-separated magnetic impurities localized on the nanowire axis. It is shown that the scattering process causes the magnetic impurities embedded in the nanowire to share their quantum information; subsequently, they can be entangled by spin interaction with the injected electron. The created entanglement between the impurities is calculated and discussed. It is shown that the exact three-dimensional problem can be approximated as a one-dimensional problem under certain circumstances. The approximate results are compared to exact calculations and discussed.

  19. Separation of image-distortion sources and magnetic-field measurement in scanning electron microscope (SEM).

    Science.gov (United States)

    Płuska, Mariusz; Czerwinski, Andrzej; Ratajczak, Jacek; Katcki, Jerzy; Oskwarek, Lukasz; Rak, Remigiusz

    2009-01-01

    The electron-microscope image distortion generated by electromagnetic interference (EMI) is an important problem for accurate imaging in scanning electron microscopy (SEM). Available commercial solutions to this problem utilize sophisticated hardware for EMI detection and compensation. Their efficiency depends on the complexity of distortions influence on SEM system. Selection of a proper method for reduction of the distortions is crucial. The current investigations allowed for a separation of the distortions impact on several components of SEM system. A sum of signals from distortion sources causes wavy deformations of specimen shapes in SEM images. The separation of various reasons of the distortion is based on measurements of the periodic deformations of the images for different electron beam energies and working distances between the microscope final aperture and the specimen. Using the SEM images, a direct influence of alternating magnetic field on the electron beam was distinguished. Distortions of electric signals in the scanning block of SEM were also separated. The presented method separates the direct magnetic field influence on the electron beam below the SEM final aperture (in the chamber) from its influence above this aperture (in the electron column). It also allows for the measurement of magnetic field present inside the SEM chamber. The current investigations gave practical guidelines for selecting the most efficient solution for reduction of the distortions.

  20. Lateral shifts of spin electron beams in antiparallel double {delta}-magnetic-barrier nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Kong Yonghong [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China); Lu Maowang, E-mail: m_w_lu@126.com [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China); Chen Saiyan; Zhang Guilian [Department of Electronic Engineering, Hunan University Science and Engineering, Hunan 425100 (China)

    2012-08-15

    We investigate the Goos-Haenchen (GH) effect of spin electron beams in a magnetic-barrier (MB) nanostructure consisting of antiparallel double {delta}-MBs, which can be experimentally realized by depositing two ferromagnetic (FM) stripes on top and bottom of the semiconductor heterostructure. GH shifts for spin electron beams across this type of MB nanostructures, is derived exactly, with the help of the stationary phase method. It is shown that GH shifts depend strongly on the spin directions for double {delta}-MBs with unidentical magnetic strengths, giving rise to a considerable spin polarization effect. It also is shown that spin polarization of GH shifts is closely relative to the separation and magnetic-strength difference of two {delta}-MBs. These interesting properties may provide an alternative scheme to spin-polarize electrons into the semiconductor, and the devices can serve as tunable spin beam splitters. - Highlights: Black-Right-Pointing-Pointer Spin Goos-Haenchen effect of electron beams through a kind of MB nanostructures. Black-Right-Pointing-Pointer GH shift depends greatly on electron-spins, which is used to spin polarize electrons in semiconductor. Black-Right-Pointing-Pointer Spin polarization in GH shift is tunable. Black-Right-Pointing-Pointer A tunable spin beam splitter is achieved.