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Sample records for magnetic moments close

  1. Moment free toroidal magnet

    DOEpatents

    Bonanos, Peter

    1983-01-01

    A toroidal magnet for confining a high magnetic field for use in fusion reactor research and nuclear particle detection. The magnet includes a series of conductor elements arranged about and fixed at its small major radius portion to the outer surface of a central cylindrical support each conductor element having a geometry such as to maintain the conductor elements in pure tension when a high current flows therein, and a support assembly which redistributes all or part of the tension which would otherwise arise in the small major radius portion of each coil element to the large major radius portion thereof.

  2. Magnetic moment nonconservation in magnetohydrodynamic turbulence models.

    PubMed

    Dalena, S; Greco, A; Rappazzo, A F; Mace, R L; Matthaeus, W H

    2012-07-01

    The fundamental assumptions of the adiabatic theory do not apply in the presence of sharp field gradients or in the presence of well-developed magnetohydrodynamic turbulence. For this reason, in such conditions the magnetic moment μ is no longer expected to be constant. This can influence particle acceleration and have considerable implications in many astrophysical problems. Starting with the resonant interaction between ions and a single parallel propagating electromagnetic wave, we derive expressions for the magnetic moment trapping width Δμ (defined as the half peak-to-peak difference in the particle magnetic moments) and the bounce frequency ω(b). We perform test-particle simulations to investigate magnetic moment behavior when resonance overlapping occurs and during the interaction of a ring-beam particle distribution with a broadband slab spectrum. We find that the changes of magnetic moment and changes of pitch angle are related when the level of magnetic fluctuations is low, δB/B(0) = (10(-3),10(-2)), where B(0) is the constant and uniform background magnetic field. Stochasticity arises for intermediate fluctuation values and its effect on pitch angle is the isotropization of the distribution function f(α). This is a transient regime during which magnetic moment distribution f(μ) exhibits a characteristic one-sided long tail and starts to be influenced by the onset of spatial parallel diffusion, i.e., the variance <(Δz)(2)> grows linearly in time as in normal diffusion. With strong fluctuations f(α) becomes completely isotropic, spatial diffusion sets in, and the f(μ) behavior is closely related to the sampling of the varying magnetic field associated with that spatial diffusion.

  3. Updating neutrino magnetic moment constraints

    NASA Astrophysics Data System (ADS)

    Cañas, B. C.; Miranda, O. G.; Parada, A.; Tórtola, M.; Valle, J. W. F.

    2016-02-01

    In this paper we provide an updated analysis of the neutrino magnetic moments (NMMs), discussing both the constraints on the magnitudes of the three transition moments Λi and the role of the CP violating phases present both in the mixing matrix and in the NMM matrix. The scattering of solar neutrinos off electrons in Borexino provides the most stringent restrictions, due to its robust statistics and the low energies observed, below 1 MeV. Our new limit on the effective neutrino magnetic moment which follows from the most recent Borexino data is 3.1 ×10-11μB at 90% C.L. This corresponds to the individual transition magnetic moment constraints: |Λ1 | ≤ 5.6 ×10-11μB, |Λ2 | ≤ 4.0 ×10-11μB, and |Λ3 | ≤ 3.1 ×10-11μB (90% C.L.), irrespective of any complex phase. Indeed, the incoherent admixture of neutrino mass eigenstates present in the solar flux makes Borexino insensitive to the Majorana phases present in the NMM matrix. For this reason we also provide a global analysis including the case of reactor and accelerator neutrino sources, presenting the resulting constraints for different values of the relevant CP phases. Improved reactor and accelerator neutrino experiments will be needed in order to underpin the full profile of the neutrino electromagnetic properties.

  4. Superconductivity from Emerging Magnetic Moments.

    PubMed

    Hoshino, Shintaro; Werner, Philipp

    2015-12-11

    Multiorbital Hubbard models are shown to exhibit a spatially isotropic spin-triplet superconducting phase, where equal-spin electrons in different local orbitals are paired. This superconducting state is stabilized in the spin-freezing crossover regime, where local moments emerge in the metal phase, and the pairing is substantially assisted by spin anisotropy. The phase diagram features a superconducting dome below a non-Fermi-liquid metallic region and next to a magnetically ordered phase. We suggest that this type of fluctuating-moment-induced superconductivity, which is not originating from fluctuations near a quantum critical point, may be realized in spin-triplet superconductors such as strontium ruthenates and uranium compounds. PMID:26705649

  5. Superconductivity from Emerging Magnetic Moments

    NASA Astrophysics Data System (ADS)

    Hoshino, Shintaro; Werner, Philipp

    2015-12-01

    Multiorbital Hubbard models are shown to exhibit a spatially isotropic spin-triplet superconducting phase, where equal-spin electrons in different local orbitals are paired. This superconducting state is stabilized in the spin-freezing crossover regime, where local moments emerge in the metal phase, and the pairing is substantially assisted by spin anisotropy. The phase diagram features a superconducting dome below a non-Fermi-liquid metallic region and next to a magnetically ordered phase. We suggest that this type of fluctuating-moment-induced superconductivity, which is not originating from fluctuations near a quantum critical point, may be realized in spin-triplet superconductors such as strontium ruthenates and uranium compounds.

  6. How to introduce the magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Bezerra, M.; Kort-Kamp, W. J. M.; Cougo-Pinto, M. V.; Farina, C.

    2012-09-01

    We show how the concept of the magnetic dipole moment can be introduced in the same way as the concept of the electric dipole moment in introductory courses on electromagnetism. Considering a localized steady current distribution, we make a Taylor expansion directly in the Biot-Savart law to obtain, explicitly, the dominant contribution of the magnetic field at distant points, identifying the magnetic dipole moment of the distribution. We also present a simple but general demonstration of the torque exerted by a uniform magnetic field on a current loop of general form, not necessarily planar. For pedagogical reasons we start by reviewing briefly the concept of the electric dipole moment.

  7. Magnetic moment distribution of magnetic cataclysmic variables

    NASA Technical Reports Server (NTRS)

    Wu, Kinwah; Wickramasinghe, Dayal T.

    1991-01-01

    A simulation study is made of the relative numbers of the AM Herculis binaries and the intermediate polars as a function of the orbital period using random variables subject to suitable constraints to describe the various parameters. It is shown that the observations can be matched by a single distribution in the magnetic moment equals 0.7 +/- 0.3. For such an ensemble, the intermediate polars are distributed in the log(Porb) - log(Ps) diagram about the critical disk line but with a larger scatter than observed.

  8. Magnetic moments in graphene with vacancies.

    PubMed

    Chen, Jing-Jing; Wu, Han-Chun; Yu, Da-Peng; Liao, Zhi-Min

    2014-08-01

    Vacancies can induce local magnetic moments in graphene, paving the way to make magnetic functional graphene. Due to the interaction between magnetic moments and conduction carriers, the magnetotransport properties of graphene can be modulated. Here, the effects of vacancy induced magnetic moments on the electrical properties of graphene are studied via magnetotransport measurements and spin-polarized density functional theory calculations. We show by quantum Hall measurements that a sharp resonant Vπ state is introduced in the midgap region of graphene with vacancies, resulting in the local magnetic moment. The coupling between the localized Vπ state and the itinerant carrier is tuned by varying the carrier concentration, temperature, magnetic field, and vacancy density, which results in a transition between hopping transport and the Kondo effect and a transition between giant negative magnetoresistance (MR) and positive MR. This modulated magnetotransport is valuable for graphene based spintronic devices.

  9. Magnetic moments in graphene with vacancies

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Jing; Wu, Han-Chun; Yu, Da-Peng; Liao, Zhi-Min

    2014-07-01

    Vacancies can induce local magnetic moments in graphene, paving the way to make magnetic functional graphene. Due to the interaction between magnetic moments and conduction carriers, the magnetotransport properties of graphene can be modulated. Here, the effects of vacancy induced magnetic moments on the electrical properties of graphene are studied via magnetotransport measurements and spin-polarized density functional theory calculations. We show by quantum Hall measurements that a sharp resonant Vπ state is introduced in the midgap region of graphene with vacancies, resulting in the local magnetic moment. The coupling between the localized Vπ state and the itinerant carrier is tuned by varying the carrier concentration, temperature, magnetic field, and vacancy density, which results in a transition between hopping transport and the Kondo effect and a transition between giant negative magnetoresistance (MR) and positive MR. This modulated magnetotransport is valuable for graphene based spintronic devices.

  10. Magnetic moments of light nuclei from lattice quantum chromodynamics

    DOE PAGES

    Beane, S.  R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H.  W.; Orginos, K.; Parreño, A.; Savage, M.  J.; Tiburzi, B.  C.

    2014-12-16

    We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to mπ ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. We find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures itsmore » dominant structure. Similarly a shell-model-like moment is found for the triton, μ3H ~ μp. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.« less

  11. Tensor charge and anomalous magnetic moment correlation

    SciTech Connect

    Mekhfi, Mustapha

    2005-12-01

    We propose a generalization of the upgraded Karl-Sehgal formula which relates baryon magnetic moments to the spin structure of constituent quarks, by adding anomalous magnetic moments of quarks. We first argue that the relativistic nature of quarks inside baryons requires the introduction of two kinds of magnetisms, one axial and the other tensorial. The first one is associated with integrated quark helicity distributions {delta}{sub i}-{delta}{sub i} (standard) and the second with integrated transversity distributions {delta}{sub i}-{delta}{sub i}. The weight of each contribution is controlled by the combination of two parameters, x{sub i} the ratio of the quark mass to the average kinetic energy and a{sub i} the quark anomalous magnetic moment. The quark anomalous magnetic moment is correlated to transversity, and both are necessary ingredients in describing relativistic quarks. The proposed formula, when confronted with baryon magnetic moments data with reasonable inputs, yields, besides quark magnetic densities, anomalous magnetic moments large enough not to be ignored.

  12. How to Introduce the Magnetic Dipole Moment

    ERIC Educational Resources Information Center

    Bezerra, M.; Kort-Kamp, W. J. M.; Cougo-Pinto, M. V.; Farina, C.

    2012-01-01

    We show how the concept of the magnetic dipole moment can be introduced in the same way as the concept of the electric dipole moment in introductory courses on electromagnetism. Considering a localized steady current distribution, we make a Taylor expansion directly in the Biot-Savart law to obtain, explicitly, the dominant contribution of the…

  13. Measurement of magnetic moment via optical transmission

    NASA Astrophysics Data System (ADS)

    Heidsieck, Alexandra; Schmid, Daniel; Gleich, Bernhard

    2016-03-01

    The magnetic moment of nanoparticles is an important property for drug targeting and related applications as well as for the simulation thereof. However, the measurement of the magnetic moment of nanoparticles, nanoparticle-virus-complexes or microspheres in solution can be difficult and often yields unsatisfying or incomparable results. To measure the magnetic moment, we designed a custom measurement device including a magnetic set-up to observe nanoparticles indirectly via light transmission in solution. We present a simple, cheap device of manageable size, which can be used in any laboratory as well as a novel evaluation method to determine the magnetic moment of nanoparticles via the change of the optical density of the particle suspension in a well-defined magnetic gradient field. In contrast to many of the established measurement methods, we are able to observe and measure the nanoparticle complexes in their natural state in the respective medium. The nanoparticles move along the magnetic gradient and thereby away from the observation point. Due to this movement, the optical density of the fluid decreases and the transmission increases over time at the measurement location. By comparing the measurement with parametric simulations, we can deduce the magnetic moment from the observed behavior.

  14. Determination of the Neutron Magnetic Moment

    DOE R&D Accomplishments Database

    Greene, G. L.; Ramsey, N. F.; Mampe, W.; Pendlebury, J. M.; Smith, K.; Dress, W. B.; Miller, P. D.; Perrin, P.

    1981-06-01

    The neutron magnetic moment has been measured with an improvement of a factor of 100 over the previous best measurement. Using a magnetic resonance spectrometer of the separated oscillatory field type capable of determining a resonance signal for both neutrons and protons (in flowing H{sub 2}O), we find ..mu..{sub n}/..mu..{sub p} = 0.68497935(17) (0.25 ppM). The neutron magnetic moment can also be expressed without loss of accuracy in a variety of other units.

  15. Detecting transition radiation from a magnetic moment.

    PubMed

    Ivanov, Igor P; Karlovets, Dmitry V

    2013-06-28

    Electromagnetic radiation can be emitted not only by particle charges but also by magnetic moments and higher electric and magnetic multipoles. However, experimental proofs of this fundamental fact are extremely scarce. In particular, the magnetic moment contribution has never been observed in any form of polarization radiation. Here, we propose to detect it using vortex electrons carrying large orbital angular momentum ℓ. The relative contribution of the orbital angular momentum-induced magnetic moment, ℓℏω/Ee, becomes much larger than the spin-induced contribution ℏω/E and it can be observed experimentally. As a particular example, we consider transition radiation from vortex electrons obliquely incident on an interface between a vacuum and a dispersive medium, in which the magnetic moment contribution manifests itself via a left-right angular asymmetry. For electrons with Ee=300  keV and ℓ=100-1000, we predict an asymmetry of the order of 0.1%-1%, which could be measured with existing technology. Thus, vortex electrons emerge as a new tool in the physics of electromagnetic radiation.

  16. Electrical and Thermal Control of Magnetic Moments

    NASA Astrophysics Data System (ADS)

    Barnaś, J.; Balaz, P.; Dyrdał, A.; Dugaev, V. K.

    Spin transport in a magnetically nonuniform structure can lead to transfer of angular momentum from conduction electrons to local magnetization. This, in turn, gives rise to a spin-transfer torque, which can modify magnetic state of the system. Another mechanism of current-induced spin torque relies on spin-orbit interactions. However, the spin torque can be induced not only by electric field driving the current, but also by a temperature gradient which drives a thermocurrent due to the thermoelectric phenomena. Both current- and thermallyinduced spin torques allow to control and manipulate magnetic moments.

  17. Interpreting magnetic data by integral moments

    NASA Astrophysics Data System (ADS)

    Tontini, F. Caratori; Pedersen, L. B.

    2008-09-01

    The use of the integral moments for interpreting magnetic data is based on a very elegant property of potential fields, but in the past it has not been completely exploited due to problems concerning real data. We describe a new 3-D development of previous 2-D results aimed at determining the magnetization direction, extending the calculation to second-order moments to recover the centre of mass of the magnetization distribution. The method is enhanced to reduce the effects of the regional field that often alters the first-order solutions. Moreover, we introduce an iterative correction to properly assess the errors coming from finite-size surveys or interaction with neighbouring anomalies, which are the most important causes of the failing of the method for real data. We test the method on some synthetic examples, and finally, we show the results obtained by analysing the aeromagnetic anomaly of the Monte Vulture volcano in Southern Italy.

  18. Noncommutative magnetic moment of charged particles

    SciTech Connect

    Adorno, T. C.; Gitman, D. M.; Shabad, A. E.; Vassilevich, D. V.

    2011-10-15

    It has been argued that in noncommutative field theories, the sizes of physical objects cannot be taken smaller than an ''elementary length'' related to noncommutativity parameters. By gauge covariantly extending field equations of noncommutative U(1){sub *} theory to cover the presence of external sources, we find electric and magnetic fields produced by an extended static charge. We find that such a charge, apart from being an ordinary electric monopole, is also a magnetic dipole. By writing off the existing experimental clearance in the value of the lepton magnetic moments for the present effect, we get the bound on noncommutativity at the level of 10{sup 4} TeV.

  19. Magnetic moments of light nuclei from lattice quantum chromodynamics

    SciTech Connect

    Beane, S.  R.; Chang, E.; Cohen, S.; Detmold, W.; Lin, H.  W.; Orginos, K.; Parreño, A.; Savage, M.  J.; Tiburzi, B.  C.

    2014-12-16

    We present the results of lattice QCD calculations of the magnetic moments of the lightest nuclei, the deuteron, the triton and 3He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to mπ ~ 800 MeV, reveal that the structure of these nuclei at unphysically heavy quark masses closely resembles that at the physical quark masses. We find that the magnetic moment of 3He differs only slightly from that of a free neutron, as is the case in nature, indicating that the shell-model configuration of two spin-paired protons and a valence neutron captures its dominant structure. Similarly a shell-model-like moment is found for the triton, μ3H ~ μp. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.

  20. Magnetic Moments of States in 110Sn.

    NASA Astrophysics Data System (ADS)

    Kumbartzki, G. J.

    2016-06-01

    The semi-magic Sn isotopes with Z = 50 are the subject of extensive experimental and theoretical studies. The measured B(E2) values to the 21 + states for the neutron-deficient side of the isotope chain suggest enhanced collectivity when fewer particles are available if the proton shell is not broken. Magnetic moments which are sensitive to proton and neutron contributions to the wave functions of the states could provide critical and relevant information. Magnetic moments were previously measured only for the even stable and a few neutron-rich unstable Sn isotopes. A measurement of the g factors of excited states in 110Sn using the transient field technique was performed at the 88-Inch Cyclotron at the LBNL in Berkeley. The 110Sn nuclei were produced via an α-particle transfer to 106Cd.

  1. Nuclear magnetic moments and related sum rules

    SciTech Connect

    Bentz, Wolfgang; Arima, Akito

    2011-05-06

    We first review the history and our present understanding of nuclear magnetic moments and Gamow-Teller transitions, with emphasis on the roles of configuration mixing and meson exchange currents. Then we discuss the renormalization of the orbital g-factor in nuclei, and its relation to the E1 sum rule for photoabsorption and the M1 sum rule for the scissors mode of deformed nuclei.

  2. Measurement of the Ω- magnetic moment

    NASA Astrophysics Data System (ADS)

    Diehl, H. T.; Teige, S.; Thomson, G. B.; Zou, Y.; James, C.; Luk, K. B.; Rameika, R.; Ho, P. M.; Longo, M. J.; Nguyen, A.; Duryea, J.; Guglielmo, G.; Johns, K.; Heller, K.; Thorne, K.

    1991-08-01

    A sample of 24 700 Ω- hyperons was produced by a prolarized neutral beam in a spin-transfer reaction. The Ω- polarizations are found to be -0.054+/-0.019 and -0.149+/-0.055 at mean Ω- momenta of 322 and 398 GeV/c, respectively. The directions of these polarizations give an Ω- magnetic moment of -(1.94+/-0.17+/-0.14)μN

  3. Nuclear magnetic moment of sup 106 Rh

    SciTech Connect

    Ohya, S.; Ashworth, C.J.; Nawaz, Z.; Stone, N.J.; Back, P.J. )

    1990-01-01

    Nuclear orientation and nuclear magnetic resonance measurements have been performed for {sup 106}Rh oriented at low temperature in iron and nickel hosts. From the results of the temperature dependence measurements of nuclear orientation, the magnetic moment of {sup 106}Rh was deduced as {vert bar}{mu}({sup 106}Rh,1{sup +}){vert bar}=2.52(5){mu}{sub {ital N}}, which is very different from the value of 3.07(9) {mu}{sub {ital N}} reported previously. From the nuclear magnetic resonance on oriented nuclei measurements of {sup 106}Rh{ital Ni}, the magnetic hyperfine splitting frequency {vert bar}{ital g}{mu}{sub {ital N}}B{sub HF}/h{vert bar} was determined to be 441.5(7) MHz. Using the hyperfine field {ital B}{sub HF} (Rh{ital Ni}) of {minus}22.49(5) T, the precise value of the magnetic moment of {sup 106}Rh was deduced: {vert bar}{mu}({sup 106}Rh,1{sup +}){vert bar} =2.575(7) {mu}{sub {ital N}}. The electric quadrupole interaction has been measured using modulated adiabatic passage on oriented nuclei in a nickel single-crystal host. A broad distribution of the quadrupole splitting {Delta}{nu}{sub {ital Q}} is found, extending from 0 to 300 kHz.

  4. Atomic electric dipole moment induced by the nuclear electric dipole moment: The magnetic moment effect

    SciTech Connect

    Porsev, S. G.; Ginges, J. S. M.; Flambaum, V. V.

    2011-04-15

    We have considered a mechanism for inducing a time-reversal violating electric dipole moment (EDM) in atoms through the interaction of a nuclear EDM d{sub N} with the hyperfine interaction, the ''magnetic moment effect''. We have derived the operator for this interaction and presented analytical formulas for the matrix elements between atomic states. Induced EDMs in the diamagnetic atoms {sup 129}Xe, {sup 171}Yb, {sup 199}Hg, {sup 211}Rn, and {sup 225}Ra have been calculated numerically. From the experimental limits on the atomic EDMs of {sup 129}Xe and {sup 199}Hg we have placed the following constraints on the nuclear EDMs, |d{sub N}({sup 129}Xe)|<1.1x10{sup -21}|e|cm and |d{sub N}({sup 199}Hg)|<2.8x10{sup -24}|e|cm.

  5. Magnetic resonance signal moment determination using the Earth's magnetic field.

    PubMed

    Fridjonsson, E O; Creber, S A; Vrouwenvelder, J S; Johns, M L

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  6. Magnetic resonance signal moment determination using the Earth's magnetic field

    NASA Astrophysics Data System (ADS)

    Fridjonsson, E. O.; Creber, S. A.; Vrouwenvelder, J. S.; Johns, M. L.

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system.

  7. Magnetic resonance signal moment determination using the Earth's magnetic field.

    PubMed

    Fridjonsson, E O; Creber, S A; Vrouwenvelder, J S; Johns, M L

    2015-03-01

    We demonstrate a method to manipulate magnetic resonance data such that the moments of the signal spatial distribution are readily accessible. Usually, magnetic resonance imaging relies on data acquired in so-called k-space which is subsequently Fourier transformed to render an image. Here, via analysis of the complex signal in the vicinity of the centre of k-space we are able to access the first three moments of the signal spatial distribution, ultimately in multiple directions. This is demonstrated for biofouling of a reverse osmosis (RO) membrane module, rendering unique information and an early warning of the onset of fouling. The analysis is particularly applicable for the use of mobile magnetic resonance spectrometers; here we demonstrate it using an Earth's magnetic field system. PMID:25700116

  8. Layer-Resolved Magnetic Moments in Ni/Pt Multilayers

    NASA Astrophysics Data System (ADS)

    Wilhelm, F.; Poulopoulos, P.; Ceballos, G.; Wende, H.; Baberschke, K.; Srivastava, P.; Benea, D.; Ebert, H.; Angelakeris, M.; Flevaris, N. K.; Niarchos, D.; Rogalev, A.; Brookes, N. B.

    2000-07-01

    The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically ``dead'' Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

  9. Pinned orbital moments – A new contribution to magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Audehm, P.; Schmidt, M.; Brück, S.; Tietze, T.; Gräfe, J.; Macke, S.; Schütz, G.; Goering, E.

    2016-05-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy.

  10. Magnetic moments and angular momenta of stars and planets

    NASA Technical Reports Server (NTRS)

    Arge, C. N.; Mullan, D. J.; Dolginov, A. Z.

    1995-01-01

    Using published data on magnetic fields, radii, masses, and rotation, we have compiled a data set of magnetic moments mu and angular momenta L for stars and planets. In our subsample of hotter stars (classes A, B, and O), there are 171 objects. In the subsample of cooler stars (classes F, G, K, and M), there are 54 objects. We include 33 white dwarfs, of which 19 are in cataclysmic variables. The pulsar subsample contains 32 pulsars in binaries and 429 isolated pulsars. Som subsamples exhibit significant empirical correlations between log mu and log L. For the hot and cool stars, the correlations are positive. However, the hot-star correlation is significantly shallower than for the cool stars. In the solar system subsample, the correlation has essentially the same slope as for the cool stars, although the magnetic moments are two to three orders of magnitude smaller for the solar system objects at a given L value. For isolated white dwarfs, the correlations are weak or absent. Pulsars and white dwarfs in close binaries show strong negative correlations: the results are quantitatively consistent with magnetically enforced synchronism with the orbital period. When we consider the centers of gravity of the different subsamples of objects, a significant positive correlation appears between log mu and log L.

  11. Tensor Charges, Quark Anomalous Magnetic Moments And Baryons

    SciTech Connect

    Mekhfi, M.

    2007-06-13

    We propose an 'ultimate' upgrade of the Karl- Sehgal (KS) formula which relates baryon magnetic moments to the spin structure of constituent quarks, by adding anomalous magnetic moments of quarks. We first argue that relativistic nature of quarks inside baryons requires introduction of two kinds of magnetisms, one axial and the other tensoriel. The first one is associated with integrated quark helicity distributions {delta}i - {delta}i-bar (standard ) and the second with integrated transversity distributions {delta}i - {delta}i-bar. The weight of each contribution is controlled by the combination of two parameters, xi the ratio of the quark mass to the average kinetic energy and ai the quark anomalous magnetic moment. The quark anomalous magnetic moment is thus shown to be correlated to transversity. The proposed formula confirms, with reasonable inputs that anomalous magnetic moments of quarks are unavoidable intrinsic properties.

  12. Numerical modeling of higher order magnetic moments in UXO discrimination

    USGS Publications Warehouse

    Sanchez, V.; Yaoguo, L.; Nabighian, M.N.; Wright, D.L.

    2008-01-01

    The surface magnetic anomaly observed in unexploded ordnance (UXO) clearance is mainly dipolar, and consequently, the dipole is the only magnetic moment regularly recovered in UXO discrimination. The dipole moment contains information about the intensity of magnetization but lacks information about the shape of the target. In contrast, higher order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and to show its potential utility in UXO clearance, we present a numerical modeling study of UXO and related metallic objects. The tool for the modeling is a nonlinear integral equation describing magnetization within isolated compact objects of high susceptibility. A solution for magnetization distribution then allows us to compute the magnetic multipole moments of the object, analyze their relationships, and provide a depiction of the anomaly produced by different moments within the object. Our modeling results show the presence of significant higher order moments for more asymmetric objects, and the fields of these higher order moments are well above the noise level of magnetic gradient data. The contribution from higher order moments may provide a practical tool for improved UXO discrimination. ?? 2008 IEEE.

  13. Enhanced orbital magnetic moments in magnetic heterostructures with interface perpendicular magnetic anisotropy.

    PubMed

    Ueno, Tetsuro; Sinha, Jaivardhan; Inami, Nobuhito; Takeichi, Yasuo; Mitani, Seiji; Ono, Kanta; Hayashi, Masamitsu

    2015-01-01

    We have studied the magnetic layer thickness dependence of the orbital magnetic moment in magnetic heterostructures to identify contributions from interfaces. Three different heterostructures, Ta/CoFeB/MgO, Pt/Co/AlOx and Pt/Co/Pt, which possess significant interface contribution to the perpendicular magnetic anisotropy, are studied as model systems. X-ray magnetic circular dichroism spectroscopy is used to evaluate the relative orbital moment, i.e. the ratio of the orbital to spin moments, of the magnetic elements constituting the heterostructures. We find that the relative orbital moment of Co in Pt/Co/Pt remains constant against its thickness whereas the moment increases with decreasing Co layer thickness for Pt/Co/AlOx, suggesting that a non-zero interface orbital moment exists for the latter system. For Ta/CoFeB/MgO, a non-zero interface orbital moment is found only for Fe. X-ray absorption spectra shows that a particular oxidized Co state in Pt/Co/AlOx, absent in other heterosturctures, may give rise to the interface orbital moment in this system. These results show element specific contributions to the interface orbital magnetic moments in ultrathin magnetic heterostructures. PMID:26456454

  14. Numerical modeling of magnetic moments for UXO applications

    USGS Publications Warehouse

    Sanchez, V.; Li, Y.; Nabighian, M.; Wright, D.

    2006-01-01

    The surface magnetic anomaly observed in UXO clearance is mainly dipolar and, consequently, the dipole is the only magnetic moment regularly recovered in UXO applications. The dipole moment contains information about intensity of magnetization but lacks information about shape. In contrast, higher-order moments, such as quadrupole and octupole, encode asymmetry properties of the magnetization distribution within the buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and its potential utility in UXO clearance, we present a 3D numerical modeling study for highly susceptible metallic objects. The basis for the modeling is the solution of a nonlinear integral equation describing magnetization within isolated objects. A solution for magnetization distribution then allows us to compute magnetic moments of the object, analyze their relationships, and provide a depiction of the surface anomaly produced by different moments within the object. Our modeling results show significant high-order moments for more asymmetric objects situated at depths typical of UXO burial, and suggest that the increased relative contribution to magnetic gradient data from these higher-order moments may provide a practical tool for improved UXO discrimination.

  15. Magnetic moments of octet baryons and sea antiquark polarizations

    SciTech Connect

    Bartelski, Jan; Tatur, Stanislaw

    2005-01-01

    Using generalized Sehgal equations for magnetic moments of baryon octet and taking into account {sigma}{sup 0}-{lambda} mixing and two particle corrections to independent quark contributions we obtain very good fit using experimental values for errors of such moments. We present sum rules for quark magnetic moments ratios and for integrated spin densities ratios. Because of the SU(3) structure of our equations the results for magnetic moments of quarks and their densities depend on two additional parameters. Using information from deep inelastic scattering and baryon {beta}-decays we discuss the dependence of antiquark polarizations on introduced parameters. For some plausible values of these parameters we show that these polarizations are small if we neglect angular momenta of quarks. Our very good fit to magnetic moments of baryon octet can still be improved by using specific model for angular momentum of quarks.

  16. Relative importance of magnetic moments in UXO clearance applications

    USGS Publications Warehouse

    Sanchez, V.; Li, Y.; Nabighian, M.; Wright, D.

    2006-01-01

    Surface magnetic anomaly observed in UXO clearance is mainly dipolar and, as a result, the dipole is the only moment used regularly in UXO applications. The dipole moment contains intensity of magnetization information but lacks shape information. Unlike dipole, higher-order moments, such as quadrupole and octupole, encode asymmetry properties of magnetization distribution within buried targets. In order to improve our understanding of magnetization distribution within UXO and non-UXO objects and its potential utility in UXO clearance, we present results of a 3D numerical modeling study for highly susceptible metallic objects. The basis for modeling is the solution of a nonlinear integral equation, describing magnetization within isolated objects, allowing us to compute magnetic moments of the object, analyze their relationships, and provide a depiction of the surface anomaly produced by the different moments within the object. Our modeling results show significant high-order moments for more asymmetric objects situated at typical UXO burial depths, and suggest that the increased relative contribution to magnetic gradient data from these higher-order moments may provide a practical tool for improved UXO discrimination. ?? 2005 Society of Exploration Geophysicists.

  17. The Determination of the Muon Magnetic Moment from Cosmic Rays

    ERIC Educational Resources Information Center

    Amsler, C.

    1974-01-01

    Describes an experiment suited for use in an advanced laboratory course in particle physics. The magnetic moment of cosmic ray muons which have some polarization is determined with an error of about five percent. (Author/GS)

  18. Magnetic moment softening and domain wall resistance in Ni nanowires.

    PubMed

    Burton, J D; Sabirianov, R F; Jaswal, S S; Tsymbal, E Y; Mryasov, O N

    2006-08-18

    We perform ab initio calculations of the electronic structure and conductance of atomic-size Ni nanowires with domain walls only a few atomic lattice constants wide. We show that the hybridization between noncollinear spin states leads to a reduction of the magnetic moments in the domain wall resulting in the enhancement of the domain wall resistance. Experimental studies of the magnetic moment softening may be feasible with modern techniques such as scanning tunneling spectroscopy. PMID:17026271

  19. Neutrino magnetic moment effects in neutrino nucleus reactions

    SciTech Connect

    Singh, S.K.; Athar, M.S.

    1995-10-01

    Some low energy neutrino nucleus reactions induced by neutrinos (antineutrinos) having a magnetic moment of the order of 10{sup {minus}9}{minus}10{sup {minus}10} Bohr magneton are studied. It is found that in the case of {sup 4}He, {sup 12}C, and {sup 16}O, the detection of very low energy scalar and isoscalar elastic and inelastic reactions induced by the isoscalar vector currents can provide a better limit on the neutrino magnetic moment.

  20. Pinned orbital moments – A new contribution to magnetic anisotropy

    PubMed Central

    Audehm, P.; Schmidt, M.; Brück, S.; Tietze, T.; Gräfe, J.; Macke, S.; Schütz, G.; Goering, E.

    2016-01-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy. PMID:27151436

  1. Pinned orbital moments - A new contribution to magnetic anisotropy.

    PubMed

    Audehm, P; Schmidt, M; Brück, S; Tietze, T; Gräfe, J; Macke, S; Schütz, G; Goering, E

    2016-01-01

    Reduced dimensionality and symmetry breaking at interfaces lead to unusual local magnetic configurations, such as glassy behavior, frustration or increased anisotropy. The interface between a ferromagnet and an antiferromagnet is such an example for enhanced symmetry breaking. Here we present detailed X-ray magnetic circular dichroism and X-ray resonant magnetic reflectometry investigations on the spectroscopic nature of uncompensated pinned magnetic moments in the antiferromagnetic layer of a typical exchange bias system. Unexpectedly, the pinned moments exhibit nearly pure orbital moment character. This strong orbital pinning mechanism has not been observed so far and is not discussed in literature regarding any theory for local magnetocrystalline anisotropy energies in magnetic systems. To verify this new phenomenon we investigated the effect at different temperatures. We provide a simple model discussing the observed pure orbital moments, based on rotatable spin magnetic moments and pinned orbital moments on the same atom. This unexpected observation leads to a concept for a new type of anisotropy energy. PMID:27151436

  2. Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface

    PubMed Central

    Berggren, P.; Fransson, J.

    2016-01-01

    We address electron spin resonance of single magnetic moments in a tunnel junction using time-dependent electric fields and spin-polarized current. We show that the tunneling current directly depends on the local magnetic moment and that the frequency of the external electric field mixes with the characteristic Larmor frequency of the local spin. The importance of the spin-polarized current induced anisotropy fields acting on the local spin moment is, moreover, demonstrated. Our proposed model thus explains the absence of an electron spin resonance for a half integer spin, in contrast with the strong signal observed for an integer spin. PMID:27156935

  3. Magnetic Moment Enhancement for Mn7 Cluster on Graphene

    SciTech Connect

    Liu, Xiaojie; Wang, Cai-Zhuang; Lin, Hai-Qing; Ho, Kai-Ming

    2014-08-21

    Mn7 cluster on graphene with different structural motifs and magnetic orders are investigated systematically by first-principles calculations. The calculations show that Mn7 on graphene prefers a two-layer motif and exhibits a ferrimagnetic coupling. The magnetic moment of the Mn7 cluster increases from 5.0 μB at its free-standing state to about 6.0 μB upon adsorption on graphene. Mn7 cluster also induces about 0.3 μB of magnetic moment in the graphene layer, leading to an overall enhancement of 1.3 μB magnetic moment for Mn7 on graphene. Detail electron transfer and bonding analysis have been carried out to investigate the origin of the magnetic enhancement.

  4. Magnetic Moment Quantifications of Small Spherical Objects in MRI

    PubMed Central

    Cheng, Yu-Chung N.; Hsieh, Ching-Yi; Tackett, Ronald; Kokeny, Paul; Regmi, Rajesh Kumar; Lawes, Gavin

    2014-01-01

    Purpose The purpose of this work is to develop a method for accurately quantifying effective magnetic moments of spherical-like small objects from magnetic resonance imaging (MRI). A standard 3D gradient echo sequence with only one echo time is intended for our approach to measure the effective magnetic moment of a given object of interest. Methods Our method sums over complex MR signals around the object and equates those sums to equations derived from the magnetostatic theory. With those equations, our method is able to determine the center of the object with subpixel precision. By rewriting those equations, the effective magnetic moment of the object becomes the only unknown to be solved. Each quantified effective magnetic moment has an uncertainty that is derived from the error propagation method. If the volume of the object can be measured from spin echo images, the susceptibility difference between the object and its surrounding can be further quantified from the effective magnetic moment. Numerical simulations, a variety of glass beads in phantom studies with different MR imaging parameters from a 1.5 T machine, and measurements from a SQUID (superconducting quantum interference device) based magnetometer have been conducted to test the robustness of our method. Results Quantified effective magnetic moments and susceptibility differences from different imaging parameters and methods all agree with each other within two standard deviations of estimated uncertainties. Conclusion An MRI method is developed to accurately quantify the effective magnetic moment of a given small object of interest. Most results are accurate within 10% of true values and roughly half of the total results are accurate within 5% of true values using very reasonable imaging parameters. Our method is minimally affected by the partial volume, dephasing, and phase aliasing effects. Our next goal is to apply this method to in vivo studies. PMID:25490517

  5. Field-enhanced magnetic moment in ellipsoidal nano-hematite

    NASA Astrophysics Data System (ADS)

    Malik, Vikash; Sen, Somaditya; Gelting, David R.; Gajdardziska-Josifovska, Marija; Schmidt, Marius; Guptasarma, Prasenjit

    2014-04-01

    Bulk hematite is a canted antiferromagnet at room temperature and displays weak magnetic coercivity above the Morin transition temperature T M ˜ 262 K. Below T M, hematite displays traditional antiferromagnetic behavior, with no net magnetic moment or magnetic hysteresis. Here, we report that ellipsoidal nanocrystals of hematite (ENH) display a significant field-enhanced magnetic moment (FEMM) upon being poled by a magnetic field. This poled moment displays a giant coercive field of nearly 6000 Oe at low temperature. Atomic resolution transmission electron microscopy indicates that the nanocrystals are single crystalline, and that the surfaces are bulk-terminated. The apical terminations include the <001> sets of planes, which are implicated in possible formation of FM-arrangements near the surface. We tentatively suggest that FEMM in ENH could also arise from uncompensated surface spins or a shell of ordered spins oriented and pinned near the surface by a magnetic field. The gradual loss of magnetic moment with increasing temperature could arise as a result of competition between surface pinning energy, and kT. The large coercive field points toward possible applications for ENH in digital magnetic recording.

  6. Systematic study of hypernuclear magnetic moments under a perturb treatment

    NASA Astrophysics Data System (ADS)

    Wang, X. S.; Sang, H. Y.; Lü, H. F.; Yao, J. M.; Sagawa, H.

    2013-08-01

    Hypernuclei ranged from light to heavy mass are systematically investigated using a relativistic mean-field (RMF) model with a novel proposed ωΛΛ tensor coupling interaction PK1-Y1. The tensor coupling effect on core polarization, and the orbital contribution to hyperon current are discussed. Contributions to the magnetic moment from pΛ and n -1 Λ systems are found to be opposite. An expression of the magnetic moment under perturb treatment is improved with an ωΛΛ tensor coupling and the core-polarized magnetic moment μ {/D pol.} is found to be approximately proportional to the coupling strength g ωN · g {ωλ/2}. Self-consistent calculations under a perturb treatment show a semi-linear relationship as μ {/D pol.} ˜ g ωλ when g ωN is fixed.

  7. The Magnetic Moments of the Proton and the Antiproton

    NASA Astrophysics Data System (ADS)

    Ulmer, Stefan; Smorra, Christian

    A comparison of the magnetic moments of the proton and the antiproton provides a sensitive test of matter-antimatter symmetry. While the magnetic moment of the proton is known with a relative precision of 10^{-8}, that of the antiproton is only known with moderate accuracy. Important progress towards a high-precision measurement of the particle's magnetic moment was reported in 2011 by a group at Mainz when spin transitions of a single proton stored in a cryogenic Penning trap were observed. To resolve the single-proton spin flips, the so-called 'continuous Stern-Gerlach effect' was utilized. Using this technique, the proton magnetic moment was measured by two groups at Mainz and Harvard with relative precisions of 8.9× 10^{-6} and 2.5× 10^{-6}, respectively. Currently, two collaborations at the CERN antiproton decelerator (AD)—a part of ATRAP and BASE—are pushing their efforts to apply the methods developed for the proton to measure the magnetic moment of the antiproton. Very recently, DiSciacca et al. reported on a measurement of the antiproton's magnetic moment with a relative precision of 4.4 ppm, which is a improvement of the formerly best value by about a factor of 680. Using the so-called double Penning trap technique, both collaborations aim for a precision measurement at the level of at least 10^{-9} in future experiments, which would provide a highly sensitive test of the CPT symmetry using baryons.

  8. Magnetic Moment of Proton Drip-Line Nucleus (9)C

    NASA Technical Reports Server (NTRS)

    Matsuta, K.; Fukuda, M.; Tanigaki, M.; Minamisono, T.; Nojiri, Y.; Mihara, M.; Onishi, T.; Yamaguchi, T.; Harada, A.; Sasaki, M.

    1994-01-01

    The magnetic moment of the proton drip-line nucleus C-9(I(sup (pi)) = 3/2, T(sub 1/2) = 126 ms) has been measured for the first time, using the beta-NMR detection technique with polarized radioactive beams. The measure value for the magnetic moment is 1mu(C-9)! = 1.3914 +/- 0.0005 (mu)N. The deduced spin expectation value of 1.44 is unusually larger than any other ones of even-odd nuclei.

  9. Precise Determination of the Strangeness Magnetic Moment of the Nucleon

    SciTech Connect

    Leinweber, D B; Boinepalli, S; Cloet, I C; Thomas, A W; Williams, A G; Young, R D; Zanotti, J M; Zhang, J B

    2005-06-01

    By combining the constraints of charge symmetry with new chiral extrapolation techniques and recent low mass lattice QCD simulations of the individual quark contributions to the magnetic moments of the nucleon octet, we obtain a precise determination of the strange magnetic moment of the proton. The result, namely G{sub M}{sup s} = -0.051 +/- 0.021 mu{sub N}, is consistent with the latest experimental measurements but an order of magnitude more precise. This poses a tremendous challenge for future experiments.

  10. Photoproduction of the rho meson and its magnetic moments

    SciTech Connect

    Kaneko, Hiromi; Hosaka, Atsushi; Scholten, Olaf

    2011-10-21

    We study photoproduction of {rho} meson in a model of hidden local symmetry. We introduce the {rho} meson on a hidden gauge boson and phenomenological {rho} meson-nucleon Lagrangian is constructed respecting chiral symmetry. It turns out that the {sigma}-exchange interaction plays an important role in neutral {rho} meson photoproduction to reproduce the experimental cross sections. In charged {rho} meson photoproduction, the model takes into account the {rho} meson magnetic moments from the three-point vertex in the kinetic terms. We show that the magnetic moment of the charged {rho} meson has a significant effect on the total cross sections in proportion to the photon energies.

  11. Photospheric Magnetic Diffusion by Measuring Moments of Active Regions

    NASA Astrophysics Data System (ADS)

    Engell, Alexander; Longcope, D.

    2013-07-01

    Photospheric magnetic surface diffusion is an important constraint for the solar dynamo. The HMI Active Region Patches (HARPs) program automatically identify all magnetic regions above a certain flux. In our study we measure the moments of ARs that are no longer actively emerging and can thereby give us good statistical constraints on photospheric diffusion. We also present the diffusion properties as a function of latitude, flux density, and single polarity (leading or following) within each HARP.

  12. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    SciTech Connect

    Córsico, A.H.; Althaus, L.G.; García-Berro, E. E-mail: althaus@fcaglp.unlp.edu.ar E-mail: kepler@if.ufrgs.br

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  13. Nonperturbative renormalization and the electron{close_quote}s anomalous moment in large-{alpha} QED

    SciTech Connect

    Hiller, J.R.; Brodsky, S.J.

    1999-01-01

    We study the physical electron in quantum electrodynamics expanded on the light-cone Fock space in order to address two problems: (1) the physics of the electron{close_quote}s anomalous magnetic moment a{sub e} in nonperturbative QED and (2) the practical problems of ultraviolet regularization and renormalization in truncated nonperturbative light-cone Hamiltonian theory. We present results for a{sub e} computed in a light-cone gauge Fock space truncated to include one bare electron and at most two photons, i.e., up to two photons in flight. The calculational scheme uses an invariant mass cutoff, discretized light-cone quantization (DLCQ), a Tamm-Dancoff truncation of the Fock space, and a photon mass regulator. We introduce new weighting methods which greatly improve convergence to the continuum within DLCQ. Nonperturbative renormalization of the coupling and electron mass are carried out, and a limit on the magnitude of the effective physical coupling strength is computed. A large renormalized coupling strength {alpha}{sub R}=0.1 is then used to make the nonperturbative effects in the electron anomalous moment from the one-electron, two-photon Fock state sector numerically detectable. {copyright} {ital 1998} {ital The American Physical Society}

  14. Nonadiabatic behavior of the magnetic moment of a charged particle in a dipole magnetic field

    NASA Technical Reports Server (NTRS)

    Murakami, Sadayoshi; Sato, Tetsuya; Hasegawa, Akira

    1990-01-01

    This paper investigates the dynamic behavior of the magnetic moment of a particle confined in a magnetic dipole field in the presence of a low-frequency electrostatic wave. It is shown that there exist two kinds of resonances (the bounce-E x B drift resonance and the wave-drift resonance) by which the adiabaticity of the magnetic moment is broken. The unstable conditions obtained by theoretical considerations showed good agreement with the numerical results.

  15. Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal

    PubMed Central

    Frietsch, B.; Bowlan, J.; Carley, R.; Teichmann, M.; Wienholdt, S.; Hinzke, D.; Nowak, U.; Carva, K.; Oppeneer, P. M.; Weinelt, M.

    2015-01-01

    The Heisenberg–Dirac intra-atomic exchange coupling is responsible for the formation of the atomic spin moment and thus the strongest interaction in magnetism. Therefore, it is generally assumed that intra-atomic exchange leads to a quasi-instantaneous aligning process in the magnetic moment dynamics of spins in separate, on-site atomic orbitals. Following ultrashort optical excitation of gadolinium metal, we concurrently record in photoemission the 4f magnetic linear dichroism and 5d exchange splitting. Their dynamics differ by one order of magnitude, with decay constants of 14 versus 0.8 ps, respectively. Spin dynamics simulations based on an orbital-resolved Heisenberg Hamiltonian combined with first-principles calculations explain the particular dynamics of 5d and 4f spin moments well, and corroborate that the 5d exchange splitting traces closely the 5d spin-moment dynamics. Thus gadolinium shows disparate dynamics of the localized 4f and the itinerant 5d spin moments, demonstrating a breakdown of their intra-atomic exchange alignment on a picosecond timescale. PMID:26355196

  16. Closing the hierarchy for non-Markovian magnetization dynamics

    NASA Astrophysics Data System (ADS)

    Tranchida, J.; Thibaudeau, P.; Nicolis, S.

    2016-04-01

    We propose a stochastic approach for the description of the time evolution of the magnetization of nanomagnets, that interpolates between the Landau-Lifshitz-Gilbert and the Landau-Lifshitz-Bloch approximations, by varying the strength of the noise. In addition, we take into account the autocorrelation time of the noise and explore the consequences, when it is finite, on the scale of the response of the magnetization, i.e. when it may be described as colored, rather than white, noise and non-Markovian features become relevant. We close the hierarchy for the moments of the magnetization, by introducing a suitable truncation scheme, whose validity is tested by direct numerical solution of the moment equations and compared to the average deduced from a numerical solution of the corresponding stochastic Langevin equation. In this way we establish a general framework that allows both coarse-graining simulations and faster calculations beyond the truncation approximation used here.

  17. Ground state magnetic dipole moment of {sup 35}K

    SciTech Connect

    Mertzimekis, T.J.; Mantica, P.F.; Liddick, S.N.; Tomlin, B.E.; Davies, A.D.

    2006-02-15

    The ground state magnetic moment of {sup 35}K has been measured using the technique of nuclear magnetic resonance on {beta}-emitting nuclei. The short-lived {sup 35}K nuclei were produced following the reaction of a {sup 36}Ar primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the {sup 35}K nuclei produced at 2 deg. relative to the normal primary beam axis was confirmed. Together with the mirror nucleus {sup 35}S, the measurement represents the heaviest T=3/2 mirror pair for which the spin expectation value has been obtained. A linear behavior of g{sub p} vs g{sub n} has been demonstrated for the T=3/2 known mirror moments and the slope and intercept are consistent with the previous analysis of T=1/2 mirror pairs.

  18. Top Quark Amplitudes with an Anomolous Magnetic Moment

    SciTech Connect

    Larkoski, Andrew J.; Peskin, Michael E.; /SLAC

    2011-06-23

    The anomalous magnetic moment of the top quark may be measured during the first run of the LHC at 7 TeV. For these measurements, it will be useful to have available tree amplitudes with t{bar t} and arbitrarily many photons and gluons, including both QED and color anomalous magnetic moments. In this paper, we present a method for computing these amplitudes using the Britto-Cachazo-Feng-Witten recursion formula. Because we deal with an effective theory with higher-dimension couplings, there are roadblocks to a direct computation with the Britto-Cachazo-Feng-Witten method. We evade these by using an auxiliary scalar theory to compute a subset of the amplitudes.

  19. Magnetic moments and non-Fermi-liquid behavior in quasicrystals

    NASA Astrophysics Data System (ADS)

    Andrade, Eric

    Motivated by the intrinsic non-Fermi-liquid behavior observed in the heavy-fermion quasicrystal Au51Al34Yb15, we study the low-temperature behavior of dilute magnetic impurities placed in metallic quasicrystals. We find that a large fraction of the magnetic moments are not quenched down to very low temperatures, leading to a power-law distribution of Kondo temperatures, accompanied by a non-Fermi-liquid behavior, in a remarkable similarity to the Kondo-disorder scenario found in disordered heavy-fermion metals. This work was supported by FAPESP (Brazil) Grant No. 2013/00681-8.

  20. General magnetic transition dipole moments for electron paramagnetic resonance.

    PubMed

    Nehrkorn, Joscha; Schnegg, Alexander; Holldack, Karsten; Stoll, Stefan

    2015-01-01

    We present general expressions for the magnetic transition rates in electron paramagnetic resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (S=5/2) Fe(III) in hemin from the polarization dependence of experimental EPR line intensities.

  1. Large transition magnetic moment of the neutrino from horizontal symmetry

    NASA Astrophysics Data System (ADS)

    Babu, K. S.; Mohapatra, Rabindra N.

    1990-12-01

    The apparent anticorrelation of the solar-neutrino signal with the 11-yr sunspot cycle observed by Davis can be understood if the electron neutrino has a large magnetic moment. We discuss extensions of the standard model, where the existence of a leptonic SU(2)H-horizontal symmetry between the electron and muon generations provides a way to understand such a large magnetic moment, while keeping the neutrino mass naturally small. A global le-lμ symmetry (li=ith lepton number) is maintained even after spontaneous gauge symmetry breaking, so that the neutrino is of Zeldovich-Konopinski-Mahmoud type with m2νe-m2νμ=0. This condition automatically guarantees that the neutrino spin precession in the magnetic field of the Sun is not suppressed. Of the two extensions of the standard model that we discuss, the first one is a local SU(2)H model with the horizontal symmetry broken completely at a TeV scale. We show how a global U(1)le-lμ can be maintained although le-lμ is a subgroup of the gauged SU(2)H. The second example is the minimal supersymmetric extension of the standard model with R-parity-violating [but (le-lμ)-conserving] interactions. An approximate SU(2)H symmetry between the e-μ families is imposed in order to suppress the neutrino mass, but not its magnetic moment. We provide a detailed theoretical and phenomenological investigation of these two models and discuss their tests at the colliders as well as in low-energy experiments. The models generally predict mνe~=1-10 eV and the existence of charged scalar particles in the mass range of 100 GeV.

  2. Precise measurement of the positive muon anomalous magnetic moment

    NASA Astrophysics Data System (ADS)

    Deng, Huaizhang

    A precise measurement of the anomalous magnetic moment, am = (g - 2)/2, for the positive muon has been made at the Brookhaven Alternating Gradient Synchrotron. Highly polarized m+ of 3.09 GeV/c from a secondary beam line are injected through a superconducting inflector into a storage ring 14.2 m in diameter. The superferric storage ring has a homogeneous magnetic field of 1.45 T, which is measured by an NMR (nuclear magnetic resonance) system relative to the free proton NMR angular frequency wp . The muon spin precesses faster than its momentum rotates by an angular frequency wa in the magnetic field. The frequency wa is determined by measuring the decay positrons from the stored muons. The value of the muon anomalous magnetic moment is obtained by am =wae mmcB , 1 where is the magnetic field weighted over the union distribution in space and time, e and mm are the charge and the the mass of the union, and c is the speed of light in vacuum. During the data-taking period in 1999, the number of collected positrons increased by a factor of 20 compared to the previous data-taking period in 1998. The result from the data taken in 1999, am+=11659 202146 x10-101.3 ppm, 2 is in good agreement with previous measurements and reduces the combined error by a factor of about 3. The difference between the weighted mean of all experimental results, am (exp) = 11 659 203(15) x 10-10, and the theoretical value from the standard model, am (SM) = 11 659 176.6(6.7) x 10-10, is amexp -amSM =2616x10-10 . 3 The error is the addition in quadrature of experimental and theoretical uncertainties. The difference is 1.6 times the stated error.

  3. Room-temperature ferromagnetism with high magnetic moment in Cu-doped AlN single crystal whiskers

    NASA Astrophysics Data System (ADS)

    Jiang, Liang-Bao; Liu, Yu; Zuo, Si-Bin; Wang, Wen-Jun

    2015-02-01

    Ferromagnetism is investigated in high-quality Cu-doped AlN single crystal whiskers. The whiskers exhibit room-temperature ferromagnetism with a magnetic moment close to the results from first-principles calculations. High crystallinity and low Cu concentrations are found to be indispensable for high magnetic moments. The difference between the experimental and theoretical moment values is explored in terms of the influence of nitrogen vacancies. The calculated results demonstrate that nitrogen vacancies can reduce the magnetic moments of Cu atom. Project supported by the National Basic Research Program of China (Grant No. 2013CB932901), the National Natural Science Foundation of China (Grant Nos. 51372267, 51210105026, and 51172270), the Funds from the Chinese Academy of Sciences, the International Centre for Diffraction Data, USA (2013 Ludo Frevel Crystallography Scholarship Award), and the Funds from the Ministry of Education of China (2012 Academic Scholarship Award for Doctoral Candidates).

  4. Nucleon-nucleon bremsstrahlung: Anomalous magnetic moment effects

    SciTech Connect

    Timmermans, R.G.E.; Penninga, T.D.; Gibson, B.F.; Liou, M.K.

    2006-03-15

    Background: Two soft-photon amplitudes, the two-u-two-t special (TuTts) amplitude and the Low amplitude, are known to produce quantitatively similar np{gamma} cross sections, but they predict quite different pp{gamma} cross sections for those kinematic conditions in which the nucleon scattering angles are small (less than 25 deg.). Purpose: These two amplitudes have been applied to systematically investigate three different nucleon-nucleon bremsstrahlung (NN{gamma}) processes: pp{gamma},np{gamma}, and nn{gamma}. The nn{gamma} process is explored for the first time. The primary focus of this work is to investigate the contribution of the proton and the neutron anomalous magnetic moments to all three NN{gamma} processes for projectile energies above 150 MeV and for laboratory scattering angles ({theta}{sub 1} and {theta}{sub 2}) lying between 8 deg. and 40 deg.. Method: A special soft-photon expansion in which the TuTts amplitude is expanded in terms of the Low amplitude plus additional amplitudes is utilized to explore the relationship between the TuTts and Low amplitudes and the reasons why they agree and disagree. We also used the TuTts amplitude to calculate the NN{gamma} cross section with and without the anomalous magnetic moment contributions to explore the importance of that element of the electromagnetic current. Results: The TuTts amplitude describes well the available pp{gamma} cross-section data. The anomalous magnetic moment contribution is (i) significant in the pp{gamma} process when each scattering angle is less than 25 deg. but insignificant when each scattering angle is 40 deg. or greater and (ii) insignificant in the np{gamma} process for all scattering angles. The nn{gamma} cross sections for the TuTts and Low amplitudes differ substantially for the kinematics investigated. Conclusions: In general, the Low amplitude agrees well with the TuTts amplitude when anomalous magnetic moment effects are not significant, but the two amplitudes can yield

  5. Anomalous magnetic moment of the muon in a dispersive approach

    NASA Astrophysics Data System (ADS)

    Pauk, Vladyslav; Vanderhaeghen, Marc

    2014-12-01

    We present a new general dispersive formalism for evaluating the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon. In the suggested approach, this correction is related to the imaginary part of the muon's electromagnetic vertex function. The latter may be directly related to measurable hadronic processes by means of unitarity and analyticity. As a test we apply the introduced formalism to the case of meson pole exchanges and find agreement with the direct two-loop calculation.

  6. A planar triangular Dy3 + Dy3 single-molecule magnet with a toroidal magnetic moment.

    PubMed

    Li, Xiao-Lei; Wu, Jianfeng; Tang, Jinkui; Le Guennic, Boris; Shi, Wei; Cheng, Peng

    2016-07-21

    A unique Dy6 complex with a planar Dy3 + Dy3 structure was assembled by delicately modifying the axial ligands. Single-molecule magnet behavior and meanwhile a toroidal magnetic moment in the ground state have been observed. PMID:27388113

  7. Magnetic moments in a helical edge can make weak correlations seem strong

    NASA Astrophysics Data System (ADS)

    Väyrynen, Jukka I.; Geissler, Florian; Glazman, Leonid I.

    2016-06-01

    We study the effect of localized magnetic moments on the conductance of a helical edge. Interaction with a local moment is an effective backscattering mechanism for the edge electrons. We evaluate the resulting differential conductance as a function of temperature T and applied bias V for any value of V /T . Backscattering off magnetic moments, combined with the weak repulsion between the edge electrons, results in a power-law temperature and voltage dependence of the conductance; the corresponding small positive exponent is indicative of insulating behavior. Local moments may naturally appear due to charge disorder in a narrow-gap semiconductor. Our results provide an alternative interpretation of the recent experiment by Li et al. [Phys. Rev. Lett. 115, 136804 (2015)], 10.1103/PhysRevLett.115.136804 where a power-law suppression of the conductance was attributed to strong electron repulsion within the edge, with the value of Luttinger-liquid parameter K fine tuned close to 1 /4 .

  8. Comparison of multi-fluid moment models with particle-in-cell simulations of collisionless magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Wang, Liang; Hakim, Ammar H.; Bhattacharjee, A.; Germaschewski, K.

    2015-01-01

    We introduce an extensible multi-fluid moment model in the context of collisionless magnetic reconnection. This model evolves full Maxwell equations and simultaneously moments of the Vlasov-Maxwell equation for each species in the plasma. Effects like electron inertia and pressure gradient are self-consistently embedded in the resulting multi-fluid moment equations, without the need to explicitly solving a generalized Ohm's law. Two limits of the multi-fluid moment model are discussed, namely, the five-moment limit that evolves a scalar pressures for each species and the ten-moment limit that evolves the full anisotropic, non-gyrotropic pressure tensor for each species. We first demonstrate analytically and numerically that the five-moment model reduces to the widely used Hall magnetohydrodynamics (Hall MHD) model under the assumptions of vanishing electron inertia, infinite speed of light, and quasi-neutrality. Then, we compare ten-moment and fully kinetic particle-in-cell (PIC) simulations of a large scale Harris sheet reconnection problem, where the ten-moment equations are closed with a local linear collisionless approximation for the heat flux. The ten-moment simulation gives reasonable agreement with the PIC results regarding the structures and magnitudes of the electron flows, the polarities and magnitudes of elements of the electron pressure tensor, and the decomposition of the generalized Ohm's law. Possible ways to improve the simple local closure towards a nonlocal fully three-dimensional closure are also discussed.

  9. Comparison of multi-fluid moment models with particle-in-cell simulations of collisionless magnetic reconnection

    SciTech Connect

    Wang, Liang Germaschewski, K.; Hakim, Ammar H.; Bhattacharjee, A.

    2015-01-15

    We introduce an extensible multi-fluid moment model in the context of collisionless magnetic reconnection. This model evolves full Maxwell equations and simultaneously moments of the Vlasov-Maxwell equation for each species in the plasma. Effects like electron inertia and pressure gradient are self-consistently embedded in the resulting multi-fluid moment equations, without the need to explicitly solving a generalized Ohm's law. Two limits of the multi-fluid moment model are discussed, namely, the five-moment limit that evolves a scalar pressures for each species and the ten-moment limit that evolves the full anisotropic, non-gyrotropic pressure tensor for each species. We first demonstrate analytically and numerically that the five-moment model reduces to the widely used Hall magnetohydrodynamics (Hall MHD) model under the assumptions of vanishing electron inertia, infinite speed of light, and quasi-neutrality. Then, we compare ten-moment and fully kinetic particle-in-cell (PIC) simulations of a large scale Harris sheet reconnection problem, where the ten-moment equations are closed with a local linear collisionless approximation for the heat flux. The ten-moment simulation gives reasonable agreement with the PIC results regarding the structures and magnitudes of the electron flows, the polarities and magnitudes of elements of the electron pressure tensor, and the decomposition of the generalized Ohm's law. Possible ways to improve the simple local closure towards a nonlocal fully three-dimensional closure are also discussed.

  10. Magnetic moments induce strong phonon renormalization in FeSi

    PubMed Central

    Krannich, S.; Sidis, Y.; Lamago, D.; Heid, R.; Mignot, J.-M.; Löhneysen, H. v.; Ivanov, A.; Steffens, P.; Keller, T.; Wang, L.; Goering, E.; Weber, F.

    2015-01-01

    The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron–phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron–phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe–Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin–phonon coupling and multiple interaction paths. PMID:26611619

  11. Magnetic moments induce strong phonon renormalization in FeSi.

    PubMed

    Krannich, S; Sidis, Y; Lamago, D; Heid, R; Mignot, J-M; Löhneysen, H v; Ivanov, A; Steffens, P; Keller, T; Wang, L; Goering, E; Weber, F

    2015-01-01

    The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths. PMID:26611619

  12. Medium effects of magnetic moments of baryons on neutron stars under strong magnetic fields

    SciTech Connect

    Ryu, C. Y.; Cheoun, Myung-Ki; Kim, K. S.

    2010-08-15

    We investigate medium effects caused by density-dependent magnetic moments of baryons on neutron stars under strong magnetic fields. If we allow the variation of anomalous magnetic moments (AMMs) of baryons in dense matter under strong magnetic fields, AMMs of nucleons are enhanced to be larger than those of hyperons. The enhancement naturally causes the chemical potentials of the baryons to be large and leads to the increase of the proton fraction. Consequently, it causes the suppression of hyperons, resulting in stiffness of the equation of state. Under the presumed strong magnetic fields, we evaluate the relevant particle populations, the equation of state, and the maximum masses of neutron stars by including density-dependent AMMs and compare them with those obtained from AMMs in free space.

  13. Probing neutrino magnetic moments at the Spallation Neutron Source facility

    NASA Astrophysics Data System (ADS)

    Kosmas, T. S.; Miranda, O. G.; Papoulias, D. K.; Tórtola, M.; Valle, J. W. F.

    2015-07-01

    Majorana neutrino electromagnetic properties are studied through neutral current coherent neutrino-nucleus scattering. We focus on the potential of the recently planned COHERENT experiment at the Spallation Neutron Source to probe muon-neutrino magnetic moments. The resulting sensitivities are determined on the basis of a χ2 analysis employing realistic nuclear structure calculations in the context of the quasiparticle random phase approximation. We find that they can improve existing limits by half an order of magnitude. In addition, we show that these facilities allow for standard model precision tests in the low energy regime, with a competitive determination of the weak mixing angle. Finally, they also offer the capability to probe other electromagnetic neutrino properties, such as the neutrino charge radius. We illustrate our results for various choices of experimental setup and target material.

  14. Improved measurement of the positive muon anomalous magnetic moment

    NASA Astrophysics Data System (ADS)

    Brown, H. N.; Bunce, G.; Carey, R. M.; Cushman, P.; Danby, G. T.; Debevec, P. T.; Deng, H.; Deninger, W.; Dhawan, S. K.; Druzhinin, V. P.; Duong, L.; Earle, W.; Efstathiadis, E.; Fedotovich, G. V.; Farley, F. J.; Giron, S.; Gray, F.; Grosse-Perdekamp, M.; Grossmann, A.; Haeberlen, U.; Hare, M. F.; Hazen, E. S.; Hertzog, D. W.; Hughes, V. W.; Iwasaki, M.; Jungmann, K.; Kawall, D.; Kawamura, M.; Khazin, B. I.; Kindem, J.; Krienen, F.; Kronkvist, I.; Larsen, R.; Lee, Y. Y.; Logashenko, I.; McNabb, R.; Meng, W.; Mi, J.; Miller, J. P.; Morse, W. M.; Onderwater, C. J.; Orlov, Y.; Özben, C.; Polly, C.; Pai, C.; Paley, J. M.; Pretz, J.; Prigl, R.; Zu Putlitz, G.; Redin, S. I.; Rind, O.; Roberts, B. L.; Ryskulov, N.; Sedykh, S.; Semertzidis, Y. K.; Shatunov, Yu. M.; Solodov, E.; Sossong, M.; Steinmetz, A.; Sulak, L. R.; Timmermans, C.; Trofimov, A.; Urner, D.; von Walter, P.; Warburton, D.; Winn, D.; Yamamoto, A.; Zimmerman, D.

    2000-11-01

    A new measurement of the positive muon's anomalous magnetic moment has been made at the Brookhaven Alternating Gradient Synchrotron using the direct injection of polarized muons into the superferric storage ring. The angular frequency difference ωa between the angular spin precession frequency ωs and the angular orbital frequency ωc is measured as well as the free proton NMR frequency ωp. These determine R=ωa/ωp=3.707 201(19)×10-3. With μμ/μp=3.183 345 39(10) this gives aμ+=11 659 191(59)×10-10 (+/-5 ppm), in good agreement with the previous CERN and BNL measurements for μ+ and μ-, and with the standard model prediction.

  15. Magnetic moment of {sup 43m}S

    SciTech Connect

    Daugas, J. M.; Gaudefroy, L.; Meot, V.; Morel, P.; Rosse, B.; Hass, M.; Kumar, V.; Angelique, J. C.; Simpson, G. S.; Balabanski, D. L.; Fiori, E.; Georgiev, G.; Lozeva, R.; Force, C.; Grevy, S.; Stodel, Ch.; Thomas, J. C.; Kameda, D.; Matea, I.; Singh, B. S. Nara

    2008-11-11

    The gyromagnetic factor of the isomeric state of {sup 43}S has been measured using the Time Dependent Perturbed Angular Distribution (TDPAD) technique. The isomer was produced and spin aligned via the fragmentation of a 60 AMeV {sup 48}Ca beam at the GANIL facility. The deduced magnetic moment confirms the 7/2{sup -} spin/parity of the isomeric state and shows, for the first time, the intruder nature of the ground state. Comparison of the experimental values with Shell Model and mean-field based calculations were performed revealing a pronounced ground state deformation and a quasi-spherical isomeric state. A new isomeric state has been observed in the {sup 42}P.

  16. Experimental determination of the magnetic dipole moment of candidate magnetoreceptor cells in trout

    NASA Astrophysics Data System (ADS)

    Winklhofer, M.; Eder, S.; Cadioiu, H.; McNaughton, P. A.; Kirschvink, J. L.

    2011-12-01

    Based on histological, physiological, and physical evidence, Walker et al (1997) and Diebel et al (2000) have identified distinctive cells in the olfactory epithelium of the rainbow trout (Onchorynchus mykiss) that contain magnetite and are closely associated with neurons that respond to changes in magnetic field. To put biophysical constraints on the possible transduction mechanism of magnetic signals, and in particular, to find out if the intracellular magnet is free to rotate or rather firmly anchored within the cell body, we have studied the magneto-mechanical response of isolated candidate receptor cells in suspension using a light microscope equipped with two pairs of Helmholtz coils. From the characteristic re-orientation time of suspended cells after a change in magnetic field direction, we have determined the magnitude of the magnetic dipole moment of the cells in function of the external field strength (0.4 mT to 3.2 mT) in order to find out whether or not the natural magnetic moment is remanence-based or induced (i.e., single-domain vs. superparamagnetic/multi-domain). Results: 1) The mechanical response of isolated cells to a change in magnetic field direction was always immediate, irrespective of the direction of change, which implies that the intracellular magnet is not free to rotate in the cell, but rather rigidly attached, probably to the plasma membrane, which is also suggested by our confocal fluorescence-microscope studies. 2) The cellular dipole moment turned out to be independent of the external field strength. Thus, the natural magnetic dipole moment is based on magnetic remanence, which points to single-domain particles and corroborates the results by Diebel et al (2000), who obtained switching fields consistent with single-domain magnetite. 3). The magnetic dipole moment is found to be of the order of several tens of fAm2, which greatly exceeds previous estimates (0.5 fAm2), and thus is similar to values reported for the most strongly

  17. Three-body recombination for electrons in a strong magnetic field: Magnetic moment

    SciTech Connect

    Robicheaux, F.

    2006-03-15

    Using a classical Monte Carlo method, we have computed the three-body recombination (two free electrons and a proton scattering into one free electron and a hydrogen atom, e+e+p{yields}H+e) in strong magnetic fields. The proton is fixed in space but the electrons are allowed their full, three-dimensional motion. We investigate recombination for temperatures and fields similar to those used in recent experiments that generated antihydrogen. The present rate is compared to that when the electrons' motion is given by the guiding center approximation, validating previous results at low temperature and demonstrating the breakdown of this approximation at higher temperature. Unlike the B=0 case, strong B gives preferential recombination to atoms with positive magnetic moment. Also, the canonical angular momentum in the field direction is often negative even when the magnetic moment is negative. Both results affect the trapping of antihydrogen using spatially dependent magnetic fields.

  18. Aerodynamic Lift and Moment Calculations Using a Closed-Form Solution of the Possio Equation

    NASA Technical Reports Server (NTRS)

    Lin, Jensen; Iliff, Kenneth W.

    2000-01-01

    In this paper, we present closed-form formulas for the lift and moment coefficients of a lifting surface in two dimensional, unsteady, compressible, subsonic flow utilizing a newly developed explicit analytical solution of the Possio equation. Numerical calculations are consistent with previous numerical tables based on series expansions or ad hoc numerical schemes. More importantly, these formulas lend themselves readily to flutter analysis, compared with the tedious table-look-up schemes currently in use.

  19. Direct observation of depth profile of magnetic moment by magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Mun, Bongjin Simon; Yang, See-Hun; Mannella, Norman; Kay, Alex W.; Kim, Sang-Koog; Kortright, Jeffrey B.; Underwood, Jim H.; Hussain, Zahid; Fadley, Charles S.

    2001-03-01

    The magnetic properties at the interface between Fe and Cr wedge layers are investigated with a new depth-resolved soft x-ray photoemission spectroscopy (SXPS)[1], combined with magnetic circular dichroism (MCD). The layers of Fe (10 A)/ Cr (50 A wedge- shaped) are grown on a periodic multilayer (B 4 C(22.5A)/W(17.1 A)) _40, which provides the strong standing wave effects of 40 The unique angular dependence of photoelectron intensity of Fe and Cr has been observed at each different Cr wedge thickness and show excellent agreement with the theoretical calculation. To maximize the enhancement and contrast of standing wave effect inside of sample, the sample position is tuned to the Bragg angle position, at which the MCD measurement with SXPS along the different thickness of Cr wedge layer provides the depth profile of the magnetic moment of Fe and Cr. A strong antiparallel coupling across the interface of Cr magnetic moment is clearly resolved while the apparent reduction of Fe magnetic moment is observed near the interface. This observation is consistent with the other works on the same system [2] and even describes how the magnetic moment behaves inside of the sample from the top surface to the interface in one single sample preparation. In this experiment, a new depth-resolved SXPS has been successfully implemented to magnetic multilayer system and prove to be powerful technique to study the buried interface of magnetic system, as proposed by our former work [1]. [1] S.-H. Yang, B. S. Mun, A.W. Kay, S.-K. Kim, J. B. Kortright , J.H. Underwood, Z. Hussain, C. S. Fadley, Surf. Sci. 461 L557-L564 (2000) [2] G. Panaccione, F. Sirotti, E. Narducci, and G. Rossi, Phys. Rev. B 55, 389 (1997)

  20. Rabi, the proton magnetic moment, and the ‘2-wire' magnet, 1931-34

    NASA Astrophysics Data System (ADS)

    Forman, Paul

    2001-04-01

    With the assistance of Gregory Breit, I.I. Rabi, at Columbia University, worked out in 1931 a method to determine the spin (not the magnetic moment) of atomic nuclei by deflecting an atomic beam of the isotope in question in a weak, but long, inhomogeneous magnetic field. Crucial to this method was that it required no exact knowledge of that field. When the sensational result -- µp = 2.5µ_Bohr(m_e/m_p) -- from Otto Stern's deflection of a beam of hydrogen molecules in a strong magnetic field became known late in 1932, its confirmation by another laboratory, preferably by another method, seemed urgent. No one else had the refined technique to reproduce Stern's experiment. But because the hydrogen electronic wave function was known, the Breit-Rabi technique was susceptible of extension in this case to the measurement of the magnetic moment of the proton - - but only with accurate knowledge of the magnetic field and field gradient traversed by the atomic hydrogen beam. To this end Rabi introduced the '2-wire' magnet, producing a weak field and uniform gradient that could be calculated rather than measured. This field configuration quickly came to be used in all magnetic deflection experiments in Rabi's laboratory, first as produced directly by electric currents, and subsequently as emulated in iron electromagnets in order to achieve the higher magnetic fields required by molecular beam magnetic resonance experiments from 1937 onward.

  1. Rabi, the proton magnetic moment, and the ¡2-wire¢ magnet, 1931-34

    NASA Astrophysics Data System (ADS)

    Forman, Paul

    2001-04-01

    With the assistance of Gregory Breit, I.I. Rabi, at Columbia University, worked out in 1931 a method to determine the spin (not the magnetic moment) of atomic nuclei by deflecting an atomic beam of the isotope in question in a weak, but long, inhomogeneous magnetic field. Crucial to this method was that it required no exact knowledge of that field. When the sensational result: p = 2.5:_Bohr(m_e/m_p) from Otto Stern's deflection of a beam of hydrogen molecules in a strong magnetic field became known late in 1932, its confirmation by another laboratory, preferably by another method, seemed urgent. No one else had the refined technique to reproduce Stern's experiment. But because the hydrogen electronic wave function was known, the Breit Rabi technique was susceptible of extension in this case to the measurement of the magnetic moment of the proton but only with accurate knowledge of the magnetic field and field gradient traversed by the atomic hydrogen beam. To this end Rabi introduced the '2 wire' magnet, producing a weak field and uniform gradient that could be calculated rather than measured. This field configuration quickly came to be used in all magnetic deflection experiments in Rabi's laboratory, first as produced directly by electric currents, and subsequently as emulated in iron electromagnets in order to achieve the higher magnetic fields required by molecular beam magnetic resonance experiments from 1937 onward.

  2. Object representation and magnetic moments in thin alkali films

    NASA Astrophysics Data System (ADS)

    Garrett, Douglas C.

    2008-10-01

    impurities 1/taus and their magnetic cross section sigmas are calculated. We find that single V surface impurities are magnetic while single Mo and Co impurities are non-magnetic. Co surface clusters are magnetic. In chapter 7, thin films of Na, K, Rb and Cs are quench condensed, then covered with 1/100 of a mono-layer of Ti and finally covered with the original host. The magnetization of the films is measured by means of the anomalous Hall effect. An anomalous Hall resistance RAHE is observed for Ti on the surface of K, Rb and Cs and for Ti inside of Cs. Essentially the RAHE varies linearly with the magnetic field and is inversely proportional to the inverse temperature. A small non-linearity of RAHE suggests a Ti moment of about 1microB.

  3. -Interface effects on the magnetic moment of Co and Cu in CoCu granular alloys

    SciTech Connect

    Garcia Prieto, A.; Fdez-Gubieda, M.L.; Chaboy, J.; Laguna-Marco, M.A.; Muro, T.; Nakamura, T.

    2005-12-01

    We report on x-ray magnetic circular dichroism experiments performed on Co{sub 5}Cu{sub 95} annealed granular alloys with giant magnetoresistance. Results on the Co-L{sub 2,3} edge evidence a direct correlation between the Co orbital and spin magnetic moment and the Co clusters interfacial roughness. On the other hand, we have found dichroism on the Cu-L{sub 2,3} edge, revealing an induced magnetic polarization of the Cu interfacial atoms. The magnetic moment of the Cu atoms is mainly of spin character and is ferromagnetically coupled with the Co magnetic moment.

  4. Weak magnetic moment on IrMn exchange bias pinning layers

    SciTech Connect

    Hase, T. P. A.; Fulthorpe, B. D.; Wilkins, S. B.; Tanner, B. K.; Marrows, C. H.; Hickey, B. J.

    2001-08-13

    We present evidence from soft x-ray resonant magnetic scattering measurements at the Mn L{sub 3} edge for the existence of a small magnetic moment on the antiferromagnetic IrMn pinning layer in a NiFe/Cu/Co/IrMn spin valve structure. The variation of the signal in an applied magnetic field shows that the moment lies antiparallel to the Co moment. Changes in the Mn L{sub 3} edge signal as the Co moment is rotated into the hard direction are rapid and do not appear to be associated with thermal reordering of the antiferromagnetic domain structure. {copyright} 2001 American Institute of Physics.

  5. Relationship of magnetic moment of metallic alloys to image artifact during magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Zwarun, Andrew A.; Bourdillon, Antony J.; Button, Terry M.; Chaparali, Marali; Castro, Dan J.

    1992-06-01

    The embryonic area of interventional MRI, i.e. interstitial therapy under MR guidance, includes deep tissue laser ablation of lesions. Laser fibers can be located inside lesions by first inserting an MR-compatible cannula into the lesion and then inserting the laser fiber through the cannula into the lesion. Two factors are critical in selecting alloys for cannulae: the material should exhibit so little magnetic susceptibility that it will neither distort the MR image nor torque even at high field strengths, yet it should exhibit enough susceptibility defect that the cannula can be visualized by MR during positioning. Wires of metals and alloys were tested in a magnetometer to measure their magnetic moment, and imaged with spin echo and gradient echo MRI. Direct measurement of magnetic moment was a good indicator of MR- compatibility. Artifacts visualized with spin echo pulse sequences were smaller than those produced with gradient echo sequences.

  6. Spin and orbital magnetic moment anisotropies of monodispersed bis(phthalocyaninato)terbium on a copper surface.

    PubMed

    Stepanow, Sebastian; Honolka, Jan; Gambardella, Pietro; Vitali, Lucia; Abdurakhmanova, Nasiba; Tseng, Tzu-Chun; Rauschenbach, Stephan; Tait, Steven L; Sessi, Violetta; Klyatskaya, Svetlana; Ruben, Mario; Kern, Klaus

    2010-09-01

    The magnetic properties of isolated TbPc(2) molecules supported on a Cu(100) surface are investigated by X-ray magnetic circular dichroism at 8 K in magnetic fields up to 5 T. The crystal field and magnetic properties of single molecules are found to be robust upon adsorption on a metal substrate. The Tb magnetic moment has Ising-like magnetization; XMCD spectra combined with multiplet calculations show that the saturation orbital and spin magnetic moment values reach 3 and 6 mu(B), respectively.

  7. NiPt/Rh(111): A stable surface alloy with enhanced magnetic moments

    NASA Astrophysics Data System (ADS)

    Imam, Mighfar; Marathe, Madhura; Narasimhan, Shobhana

    2009-04-01

    We have performed ab initio density functional theory calculations to investigate the miscibility and magnetic properties of pseudomorphically grown monolayers of Ni xPt 1- x surface alloys on a Rh(111) substrate. We find that the formation of this alloy is energetically favored over phase-segregated forms, and its magnetic moment is also enhanced. A significant contribution to this enhanced magnetic moment is found to come from the induced moments on the otherwise non-magnetic elements Pt and Rh. A low concentration of Ni gives rise to a high magnetic moment per Ni atom. We find that a low effective coordination and a high non-spin-polarized density of states at the Fermi level are responsible for these enhanced moments.

  8. Anomalous Magnetic Moment of the W Boson in Different Models.

    NASA Astrophysics Data System (ADS)

    Couture, Gilles

    We consider the anomalous magnetic moment of the W boson, kappa, from an experimental and from a theoretical point of view. In the first chapter, we consider five experiments where this parameter could in principle be measured. Our results show that the W pair-production remains the best process to measure kappa. Single W production is very sensitive to kappa, but it is plagued by very small cross-sections. Photon-electron colliders can also be valuable for measuring kappa through single W production. In the second chapter, we consider a composite model where kappa is essentially free. We found that it is impossible to rule out such a model from a single measurement of kappa. We give detailed production rates for these processes. In the second half of the thesis, we set limits on the corrections to kappa at the one loop level; first in the minimal SM and then in a two -Higgs-doublet model. The main results are that measured corrections of 0.1 would clearly indicate non-perturbative physics while the minimal SM can accommodate corrections up to 0.02. Possible extensions of the SM cannot increase this figure by much: unless one is willing to introduce several extra weakly interacting families, it remains that 75%, or more, of the corrections will arise from the minimal SM.

  9. Magnetic moment orientation of nano-islands by electrostriction along two directions

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Chen, Y. W.; Cao, J. W.; Wang, T.; Bai, J. M.; Wei, F. L.

    2016-06-01

    This article introduces a new method to realize the 180° magnetic moment reversal of a ferromagnetic and ferroelectric heterostructure through electrostriction-induced magnetic anisotropy. A rectangular magnetic FeAl alloy island with a large magnetostrictive coefficient on a PZN (011) substrate was adopted in our investigation through micromagnetic simulation. Using electrostriction along the [11-1] and [1-11] directions, the magnetic moment was rotated from the long axis of the rectangular island to the direction of the strain and finally reversed to the opposite direction despite the strain sequence. The magnetic moment can be oriented to a certain direction through a certain sequence of strain if a several hundred Oe magnetic field is applied along the short axis of the island. The suitable stress-induced magnetic anisotropy energy and external magnetic field were also investigated. In consideration that a high magnetic field along the short axis leads to small thermal stability of the magnetic moment, the suitable value of stress-induced anisotropy energy is around the critical value where the stress can reverse the magnetic moment without a magnetic field. We compared the stress-induced magnetic reversal processes for same-sized semicircular, elliptical, and rectangular islands and found that the semicircular island can be more easily reversed.

  10. Mechanism of the formation of an uncompensated magnetic moment in bacterial ferrihydrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Balaev, D. A.; Dubrovskii, A. A.; Krasikov, A. A.; Stolyar, S. V.; Iskhakov, R. S.; Ladygina, V. P.; Khilazheva, E. D.

    2013-10-01

    The magnetic properties of antiferromagnetic nanoparticles of FeOOH · nH2O with sizes of 3-7 nm, which are products of vital functions of Klebsiella oxytoca bacteria, have been studied. Particles exhibit a superparamagnetic behavior. The characteristic blocking temperature is 23 K. Analysis of the magnetization curves shows that the mechanism of the formation of the uncompensated magnetic moment of particles is the random decompensation of magnetic moments of Fe3+ ions both on the surface and in the bulk of the antiferromagnetic particle. In this mechanism, the exchange coupling between the uncompensated magnetic moment of the particle and its antiferromagnetic "core" is implemented. It has been found that the temperature dependence of the uncompensated magnetic moment has the form 1 — const T 2.

  11. Gyrotropic Magnetic Effect and the Magnetic Moment on the Fermi Surface.

    PubMed

    Zhong, Shudan; Moore, Joel E; Souza, Ivo

    2016-02-19

    The current density j^{B} induced in a clean metal by a slowly-varying magnetic field B is formulated as the low-frequency limit of natural optical activity, or natural gyrotropy. Working with a multiband Pauli Hamiltonian, we obtain from the Kubo formula a simple expression for α_{ij}^{GME}=j_{i}^{B}/B_{j} in terms of the intrinsic magnetic moment (orbital plus spin) of the Bloch electrons on the Fermi surface. An alternate semiclassical derivation provides an intuitive picture of the effect, and takes into account the influence of scattering processes in dirty metals. This "gyrotropic magnetic effect" is fundamentally different from the chiral magnetic effect driven by the chiral anomaly and governed by the Berry curvature on the Fermi surface, and the two effects are compared for a minimal model of a Weyl semimetal. Like the Berry curvature, the intrinsic magnetic moment should be regarded as a basic ingredient in the Fermi-liquid description of transport in broken-symmetry metals. PMID:26943554

  12. Temperature dependence of magnetic moments of nanoparticles and their dipole interaction in magnetic fluids

    NASA Astrophysics Data System (ADS)

    Lebedev, A. V.

    2015-01-01

    Magnetic susceptibility measurements were carried out for magnetite-based fluids over a wide temperature range. The fluids were stabilized with commonly used surfactants (fatty acids) and new surfactants (polypropylene glycol and tallow acids). The coefficients of temperature dependence of the particle magnetic moments were determined by fitting of the measured and calculated values of magnetic susceptibility. The influence of the inter-particle dipole-dipole interaction on the susceptibility was taken into account in the framework of A.O. Ivanov's model. The corrections for thermal expansion were determined by density measurements of the carrier fluid. The obtained values of temperature coefficients correlate to the solidification temperature of the fluid samples. For fluids with a low solidification temperature the value of the temperature coefficient of particle magnetization coincides with its value for bulk magnetite.

  13. Fast inversion of Zeeman line profiles using central moments. II. Stokes V moments and determination of vector magnetic fields

    NASA Astrophysics Data System (ADS)

    Mein, P.; Uitenbroek, H.; Mein, N.; Bommier, V.; Faurobert, M.

    2016-06-01

    Context. In the case of unresolved solar structures or stray light contamination, inversion techniques using four Stokes parameters of Zeeman profiles cannot disentangle the combined contributions of magnetic and nonmagnetic areas to the observed Stokes I. Aims: In the framework of a two-component model atmosphere with filling factor f, we propose an inversion method restricting input data to Q , U, and V profiles, thus overcoming ambiguities from stray light and spatial mixing. Methods: The V-moments inversion (VMI) method uses shifts SV derived from moments of V-profiles and integrals of Q2, U2, and V2 to determine the strength B and inclination ψ of a magnetic field vector through least-squares polynomial fits and with very few iterations. Moment calculations are optimized to reduce data noise effects. To specify the model atmosphere of the magnetic component, an additional parameter δ, deduced from the shape of V-profiles, is used to interpolate between expansions corresponding to two basic models. Results: We perform inversions of HINODE SOT/SP data for inclination ranges 0 <ψ< 60° and 120 <ψ< 180° for the 630.2 nm Fe i line. A damping coefficient is fitted to take instrumental line broadening into account. We estimate errors from data noise. Magnetic field strengths and inclinations deduced from VMI inversion are compared with results from the inversion codes UNNOFIT and MERLIN. Conclusions: The VMI inversion method is insensitive to the dependence of Stokes I profiles on the thermodynamic structure in nonmagnetic areas. In the range of Bf products larger than 200 G, mean field strengths exceed 1000 G and there is not a very significant departure from the UNNOFIT results because of differences between magnetic and nonmagnetic model atmospheres. Further improvements might include additional parameters deduced from the shape of Stokes V profiles and from large sets of 3D-MHD simulations, especially for unresolved magnetic flux tubes.

  14. Probing the magnetic moment of FePt micromagnets prepared by focused ion beam milling

    SciTech Connect

    Overweg, H. C.; Haan, A. M. J. den; Eerkens, H. J.; Bossoni, L.; Oosterkamp, T. H.; Alkemade, P. F. A.; La Rooij, A. L.; Spreeuw, R. J. C.

    2015-08-17

    We investigate the degradation of the magnetic moment of a 300 nm thick FePt film induced by Focused Ion Beam (FIB) milling. A 1 μm × 8 μm rod is milled out of a film by a FIB process and is attached to a cantilever by electron beam induced deposition. Its magnetic moment is determined by frequency-shift cantilever magnetometry. We find that the magnetic moment of the rod is μ = 1.1 ± 0.1 × 10{sup −12} Am{sup 2}, which implies that 70% of the magnetic moment is preserved during the FIB milling process. This result has important implications for atom trapping and magnetic resonance force microscopy, which are addressed in this paper.

  15. Electronic structures and magnetic moments of Co{sub 3}FeN thin films grown by molecular beam epitaxy

    SciTech Connect

    Ito, Keita; Sanai, Tatsunori; Yasutomi, Yoko; Toko, Kaoru; Honda, Syuta; Suemasu, Takashi; Zhu, Siyuan; Kimura, Akio; Ueda, Shigenori; Takeda, Yukiharu; Saitoh, Yuji; Imai, Yoji

    2013-12-02

    We evaluated electronic structures and magnetic moments in Co{sub 3}FeN epitaxial films on SrTiO{sub 3}(001). The experimentally obtained hard x-ray photoemission spectra of the Co{sub 3}FeN film have a good agreement with those calculated. Site averaged spin magnetic moments deduced by x-ray magnetic circular dichroism were 1.52 μ{sub B} per Co atom and 2.08 μ{sub B} per Fe atom at 100 K. They are close to those of Co{sub 4}N and Fe{sub 4}N, respectively, implying that the Co and Fe atoms randomly occupy the corner and face-centered sites in the Co{sub 3}FeN unit cell.

  16. Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields

    SciTech Connect

    William Detmold; Tiburzi, Brian C.; Walker-Loud, Andre

    2010-03-01

    Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. We devise combinations of baryon two-point functions in external electric fields to isolate both observables. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how magnetic moments and electric polarizabilities can be determined from lattice QCD simulations in background electric fields. We obtain results for both the neutron and proton. Our study is currently limited to electrically neutral sea quarks.

  17. Planar Hall ring sensor for ultra-low magnetic moment sensing

    NASA Astrophysics Data System (ADS)

    Hung, Tran Quang; Terki, Ferial; Kamara, Souleymanne; Kim, Kunwoo; Charar, Salam; Kim, CheolGi

    2015-04-01

    The field sensitivity of a planar Hall effect (PHE) micro-ring type biosensor has been investigated as a function of magnetizing angle of the sensor material, for the sensing of low magnetic moment superparamagnetic labels. The field sensitivity is maximal at a magnetizing angle of α = 20°. At this optimized magnetizing angle, the field sensitivity of a PHE sensor is about 3.6 times higher than that measured at the conventional configuration, α = 90°. This optimization enables the PHE-ring sensor to detect superparamagnetic biolabels with ultra-low magnetic moments down to 4 × 10-13 emu.

  18. Re-creating Gauss's method for non-electrical absolute measurements of magnetic fields and moments

    NASA Astrophysics Data System (ADS)

    Van Baak, D. A.

    2013-10-01

    In 1832, Gauss made the first absolute measurements of magnetic fields and of magnetic moments in experiments that are straightforward and instructive to replicate. We show, using rare-earth permanent magnets and a variation of Gauss's technique, that the horizontal component of the ambient geomagnetic field, as well as the size of the magnetic moments of such magnets, can be found. The method shows the connection between the SI and cgs emu unit systems for these quantities and permits an absolute realization of the Ampere with considerable precision.

  19. Quantum tunneling of the magnetic moment in the S/F/S Josephson φ0 junction

    NASA Astrophysics Data System (ADS)

    Chudnovsky, Eugene M.

    2016-04-01

    We show that the S/F/S Josephson φ0 junction permits detection of macroscopic quantum tunneling and quantum oscillation of the magnetic moment by measuring the ac voltage across the junction. Exact expression for the tunnel splitting renormalized by the interaction with the superconducting order parameter is obtained. It is demonstrated that magnetic tunneling may become frozen at a sufficiently large φ0. The quality factor of quantum oscillations of the magnetic moment due to finite ohmic resistance of the junction is computed. It is shown that magnetic tunneling rate in the φ0 junction can be controlled by the bias current, with no need for the magnetic field.

  20. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu.

    PubMed

    Kukreja, R; Bonetti, S; Chen, Z; Backes, D; Acremann, Y; Katine, J A; Kent, A D; Dürr, H A; Ohldag, H; Stöhr, J

    2015-08-28

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10^{-5}μ_{B} on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10^{-3}μ_{B} per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow. PMID:26371670

  1. X-ray detection of transient magnetic moments induced by a spin current in Cu

    SciTech Connect

    Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J.; Kent, A. D.; Durr, H. A.; Ohldag, H.; Stohr, J.

    2015-08-24

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10–5μB on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott’s two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10–3μB per atom. As a result, this reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

  2. The investigation of giant magnetic moment in ultrathin Fe3O4 films

    NASA Astrophysics Data System (ADS)

    Guan, Xiaofen; Zhou, Guowei; Xue, Wuhong; Quan, Zhiyong; Xu, Xiaohong

    2016-03-01

    The magnetic and transport properties of Fe3O4 films with a series of thicknesses are investigated. For the films with thickness below 15 nm, the saturation magnetization (Ms) increases and the coercivity decreases with the decrease in films' thickness. The Ms of 3 nm Fe3O4 film is dramatically increased to 1017 emu/cm3. As for films' thickness more than 15 nm, Ms is tending to be close to the Fe3O4 bulk value. Furthermore, the Verwey transition temperature (Tv) is visible for all the films, but suppressed for 3 nm film. We also find that the ρ of 3 nm film is the highest of all the films. The suppressed Tv and high ρ may be related to the islands morphology in 3 nm film. To study the structure, magnetic, and transport properties of the Fe3O4 films, we propose that the giant magnetic moment most likely comes from the spin of Fe ions in the tetrahedron site switching parallel to the Fe ions in the octahedron site at the surface, interface, and grain boundaries. The above results are of great significance and also provide a promising future for either device applications or fundamental research.

  3. Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au

    NASA Astrophysics Data System (ADS)

    O'Farrell, E. C. T.; Tan, J. Y.; Yeo, Y.; Koon, G. K. W.; Ã-zyilmaz, B.; Watanabe, K.; Taniguchi, T.

    2016-08-01

    We intercalate a van der Waals heterostructure of graphene and hexagonal boron nitride with Au, by encapsulation, and show that the Au at the interface is two dimensional. Charge transfer upon current annealing indicates the redistribution of the Au and induces splitting of the graphene band structure. The effect of an in-plane magnetic field confirms that the splitting is due to spin splitting and that the spin polarization is in the plane, characteristic of a Rashba interaction with a magnitude of approximately 25 meV. Consistent with the presence of an intrinsic interfacial electric field we show that the splitting can be enhanced by an applied displacement field in dual gated samples. A giant negative magnetoresistance, up to 75%, and a field induced anomalous Hall effect at magnetic fields <1 T are observed. These demonstrate that the hybridized Au has a magnetic moment and suggests the proximity to the formation of a collective magnetic phase. These effects persist close to room temperature.

  4. Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au.

    PubMed

    O'Farrell, E C T; Tan, J Y; Yeo, Y; Koon, G K W; Özyilmaz, B; Watanabe, K; Taniguchi, T

    2016-08-12

    We intercalate a van der Waals heterostructure of graphene and hexagonal boron nitride with Au, by encapsulation, and show that the Au at the interface is two dimensional. Charge transfer upon current annealing indicates the redistribution of the Au and induces splitting of the graphene band structure. The effect of an in-plane magnetic field confirms that the splitting is due to spin splitting and that the spin polarization is in the plane, characteristic of a Rashba interaction with a magnitude of approximately 25 meV. Consistent with the presence of an intrinsic interfacial electric field we show that the splitting can be enhanced by an applied displacement field in dual gated samples. A giant negative magnetoresistance, up to 75%, and a field induced anomalous Hall effect at magnetic fields <1  T are observed. These demonstrate that the hybridized Au has a magnetic moment and suggests the proximity to the formation of a collective magnetic phase. These effects persist close to room temperature. PMID:27563982

  5. Vacancy-induced intrinsic magnetic impurity with quasilocalized spin moment in graphene

    NASA Astrophysics Data System (ADS)

    Li, Yang; He, Jing; Kong, Xiao; Kou, Su-Peng

    2014-11-01

    By considering the Hubbard model on a honeycomb lattice, we develop a theory for intrinsic magnetic impurities (MIs) with quasilocalized spin moments induced by the vacancies in graphene. Because the intrinsic MIs are characterized by the zero modes that are orthogonal to the itinerant electrons, their properties are significantly different from those of Anderson MIs with well-localized spin moments.

  6. Classical electrodynamics in material media and relativistic transformation of magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.

    2016-09-01

    We consider the relativistic transformation of the magnetic dipole moment and disclose its physical meaning, shedding light on the related difficulties in the physical interpretation of classical electrodynamics in material media.

  7. Systematic uncertainties in the precise determination of the strangeness magnetic moment of the nucleon

    SciTech Connect

    D.B. Leinweber; S. Boinepalli; A.W. Thomas; A.G. Williams; R.D. Young; J.B. Zhang; J.M. Zanotti

    2004-06-01

    Systematic uncertainties in the recent precise determination of the strangeness magnetic moment of the nucleon are identified and quantified. In summary, G{sub M}{sup s} = -0.046 {+-} 0.019 {micro}{sub N}.

  8. Contributions to the muon's anomalous magnetic moment from a hidden sector

    SciTech Connect

    McKeen, David

    2011-06-15

    Research Highlights: > Described scenario involving hidden and connector particles that couple to the standard model which could be relevant for dark matter. > Examined constraints on such particles in the case that the SM particle they couple to is the muon. > Found regions of couplings which could explain the discrepancy in the muon's anomalous magnetic moment which differ for different hidden and connector particles' spins. - Abstract: The measurement of the anomalous magnetic moment of the muon provides a stringent test of the standard model and of any physics that lies beyond it. There is currently a deviation of 3.1{sigma} between the standard model prediction for the muon's anomalous magnetic moment and its experimental value. We calculate the contribution to the anomalous magnetic moment in theories where the muon couples to a particle in a hidden sector (that is, uncharged under the standard model) and a connector (which has nontrivial standard model gauge and hidden sector quantum numbers).

  9. Robust magnetic moments on the basal plane of the graphene sheet effectively induced by OH groups

    PubMed Central

    Tang, Tao; Tang, Nujiang; Zheng, Yongping; Wan, Xiangang; Liu, Yuan; Liu, Fuchi; Xu, Qinghua; Du, Youwei

    2015-01-01

    Inducing robust magnetic moments on the basal plane of the graphene sheet is very difficult, and is one of the greatest challenges in the study of physical chemistry of graphene materials. Theoretical studies predicted that introduction of a kind of sp3-type defects formed by OH groups is an effective pathway to achieve this goal [Boukhvalov, D. W. & Katsnelson, M. I. ACS Nano 5, 2440–2446 (2011)]. Here we demonstrate that OH groups can efficiently induce robust magnetic moments on the basal plane of the graphene sheet. We show that the inducing efficiency can reach as high as 217 μB per 1000 OH groups. More interestingly, the magnetic moments are robust and can survive even at 900°C. Our findings highlight the importance of OH group as an effective sp3-type candidate for inducing robust magnetic moments on the basal plane of the graphene sheet. PMID:25677174

  10. Low magnetic moment PIN diodes for high field MRI surface coils.

    PubMed

    Voskoboynik, Pavel; Joos, Ronald D; Doherty, W E; Goldfarb, Ron B

    2006-12-01

    Positive-intrinsic-negative (PIN) silicon diodes are commonly used in magnetic resonance imaging (MRI) coils to perform active or passive blocking and detuning, or to disable circuit functions. However, diode packages with large magnetic moments are known to cause image artifacts in high field MRI systems. In this study, diode packages with low magnetic moment were designed by compensating components of ferromagnetic nickel and paramagnetic tungsten with diamagnetic silver. The new diodes have an initial positive susceptibility up to fields of 1 T and a negative susceptibility from 1 to 7 T. Their magnetic moments are one to two orders of magnitude smaller than those of standard diodes; moments as small as 20 nJ/T at 7 T were achieved. PMID:17278801

  11. Fully Relativistic Full-Potential Calculations of Magnetic Moments in Uranium Monochalcogenides with the Dirac Current

    NASA Astrophysics Data System (ADS)

    Shugo Suzuki,; Hidehisa Ohta,

    2010-07-01

    We study the orbital, spin, and total magnetic moments in uranium monochalcogenides, UX where X=S, Se, and Te, using the fully relativistic full-potential calculations based on the spin density functional theory. In particular, the orbital magnetic moments are calculated with the Dirac current. We employ two methods which adopt distinctly different basis sets; one is the fully relativistic full-potential linear-combination-of-atomic-orbitals (FFLCAO) method and the other is the fully relativistic full-potential mixed-basis (FFMB) method. Showing that the orbital magnetic moments calculated using the FFLCAO method and those calculated using the FFMB method agree very well with each other, we demonstrate that, in contrast to the conventional method, the method with the Dirac current enables us to calculate the orbital magnetic moments even if the basis set includes basis functions with no definite angular momenta, e.g., the plane waves in the FFMB method. Furthermore, it is found that the orbital magnetic moments obtained in this work are larger by nearly 0.4 μB than those obtained using the conventional method. This is crucial because the resultant differences in the total magnetic moments are about 30%. We compare the results of this work with those of previous theoretical and experimental studies.

  12. About the parametrizations utilized to perform magnetic moments measurements using the transient field technique

    NASA Astrophysics Data System (ADS)

    Gómez, A. M.; Torres, D. A.

    2016-07-01

    The experimental study of nuclear magnetic moments, using the Transient Field technique, makes use of spin-orbit hyperfine interactions to generate strong magnetic fields, above the kilo-Tesla regime, capable to create a precession of the nuclear spin. A theoretical description of such magnetic fields is still under theoretical research, and the use of parametrizations is still a common way to address the lack of theoretical information. In this contribution, a review of the main parametrizations utilized in the measurements of Nuclear Magnetic Moments will be presented, the challenges to create a theoretical description from first principles will be discussed.

  13. Dynamics of the magnetic moments for chain of dipoles in domain wall

    NASA Astrophysics Data System (ADS)

    Shutyıˇ, Anatoliy M.; Sementsov, Dmitriy I.

    2016-03-01

    We report on the dynamics of the magnetic moment numerically simulated for a chain of the magnetic nanodots coupled through the dipole-dipole interaction and in the presence of the magnetic anisotropy of various types. It is shown that a static field applied to the system causes specific fluctuations of the transverse components of the magnetic moment leading to a sequence of the oscillation trains observed in the domain wall. Various oscillation modes governed by the external alternating field are revealed. The influence of the unidirectional and uniaxial anisotropy ("easy-plane" and "easy axis" anisotropy) on the system behavior is described.

  14. Kapitza problem for the magnetic moments of synthetic antiferromagnetic systems

    SciTech Connect

    Dzhezherya, Yu. I.; Demishev, K. O.; Korenivskii, V. N.

    2012-08-15

    The dynamics of magnetization in synthetic antiferromagnetic systems with the magnetic dipole coupling in a rapidly oscillating field has been examined. It has been revealed that the system can behave similar to the Kapitza pendulum. It has been shown that an alternating magnetic field can be efficiently used to control the magnetic state of a cell of a synthetic antiferromagnet. Analytical relations have been obtained between the parameters of such an antiferromagnet and an external magnetic field at which certain quasistationary states are implemented.

  15. Origin of the giant magnetic moment in epitaxial Fe3O4 thin films

    NASA Astrophysics Data System (ADS)

    Orna, J.; Algarabel, P. A.; Morellón, L.; Pardo, J. A.; de Teresa, J. M.; López Antón, R.; Bartolomé, F.; García, L. M.; Bartolomé, J.; Cezar, J. C.; Wildes, A.

    2010-04-01

    We study the enhanced magnetic moment observed in epitaxial magnetite (Fe3O4) ultrathin films (t<15nm) grown on MgO (001) substrates by means of pulsed laser deposition. The Fe3O4 (001) thin films exhibit high crystallinity, low roughness, and sharp interfaces with the substrate, and the existence of the Verwey transition at thicknesses down to 4 nm. The evolution of the Verwey transition temperature with film thickness shows a dependence with the antiphase boundaries density. Superconducting quantum interference device (SQUID) and vibrating sample magnetometry measurements in ultrathin films show a magnetic moment much higher than the bulk magnetite value. In order to study the origin of this anomalous magnetic moment, polarized neutron reflectivity (PNR), and x-ray magnetic circular dichroism (XMCD) experiments have been performed, indicating a decrease in the magnetization with decreasing sample thickness. X-ray photoemission spectroscopy measurements show no metallic Fe clusters present in the magnetite thin films. Through inductively coupled plasma mass spectroscopy and SQUID magnetometry measurements performed in commercial MgO (001) substrates, the presence of Fe impurities embedded within the substrates has been observed. Once the substrate contribution has been corrected, a decrease in the magnetic moment of magnetite thin films with decreasing thickness is found, in good agreement with the PNR and XMCD measurements. Our experiments suggest that the origin of the enhanced magnetic moment is not intrinsic to magnetite but due to the presence of Fe impurities in the MgO substrates.

  16. Magnetization reversal of uncompensated Fe moments in exchangebiased Ni/FeF2 bilayers

    SciTech Connect

    Arenholz, Elke; Liu, Kai; Li, Zhipan; Schuller, Ivan K.

    2006-01-01

    The magnetization reversal of uncompensated Fe moments in exchange biased Ni/FeF{sub 2} bilayers was determined using soft x-ray magnetic circular and linear dichroism. The hysteresis loops resulting from the Fe moments are almost identical to those of the ferromagnetic Ni layer. However, a vertical loop shift indicates that some Fe moments are pinned in the antiferromagnetically ordered FeF{sub 2}. The pinned moments are oriented antiparallel to small cooling fields leading to negative exchange bias, but parallel to large cooling fields resulting in positive exchange bias. No indication for the formation of a parallel antiferromagnetic domain wall in the FeF{sub 2} layer upon magnetization reversal in the Ni layer was found.

  17. Classical Magnetic Dipole Moments for the Simulation of Vibrational Circular Dichroism by ab Initio Molecular Dynamics.

    PubMed

    Thomas, Martin; Kirchner, Barbara

    2016-02-01

    We present a new approach for calculating vibrational circular dichroism spectra by ab initio molecular dynamics. In the context of molecular dynamics, these spectra are given by the Fourier transform of the cross-correlation function of magnetic dipole moment and electric dipole moment. We obtain the magnetic dipole moment from the electric current density according to the classical definition. The electric current density is computed by solving a partial differential equation derived from the continuity equation and the condition that eddy currents should be absent. In combination with a radical Voronoi tessellation, this yields an individual magnetic dipole moment for each molecule in a bulk phase simulation. Using the chiral alcohol 2-butanol as an example, we show that experimental spectra are reproduced very well. Our approach requires knowing only the electron density in each simulation step, and it is not restricted to any particular electronic structure method. PMID:26771403

  18. The evolution of the magnetic moment in a corrugated magnetic field.

    PubMed

    Demokan, O.; Mirnov, V. V.

    1997-09-01

    In the first part, the equations of motion in a weakly corrugated, periodic magnetic field are linearized and solved by using paraxial approximation, to describe the model and the associated resonance condition. In the second part, the nonlinear evolution of the magnetic moment of resonant particles, in connection with their axial displacement is investigated analytically by using the multiple scale method. It is seen that the linear evolution is converted into a slow and periodic oscillation around the unperturbed value, with a considerable amplitude. The analytic expressions for the period and amplitude of the oscillations are derived and compared with the numerical simulations, which are also presented. Finally, the limitations of the paraxial approximation are concluded by investigating the numerical simulations, with actual field expressions. (c) 1997 American Institute of Physics.

  19. Direct high-precision measurement of the magnetic moment of the proton.

    PubMed

    Mooser, A; Ulmer, S; Blaum, K; Franke, K; Kracke, H; Leiteritz, C; Quint, W; Rodegheri, C C; Smorra, C; Walz, J

    2014-05-29

    One of the fundamental properties of the proton is its magnetic moment, µp. So far µp has been measured only indirectly, by analysing the spectrum of an atomic hydrogen maser in a magnetic field. Here we report the direct high-precision measurement of the magnetic moment of a single proton using the double Penning-trap technique. We drive proton-spin quantum jumps by a magnetic radio-frequency field in a Penning trap with a homogeneous magnetic field. The induced spin transitions are detected in a second trap with a strong superimposed magnetic inhomogeneity. This enables the measurement of the spin-flip probability as a function of the drive frequency. In each measurement the proton's cyclotron frequency is used to determine the magnetic field of the trap. From the normalized resonance curve, we extract the particle's magnetic moment in terms of the nuclear magneton: μp = 2.792847350(9)μN. This measurement outperforms previous Penning-trap measurements in terms of precision by a factor of about 760. It improves the precision of the forty-year-old indirect measurement, in which significant theoretical bound state corrections were required to obtain µp, by a factor of 3. By application of this method to the antiproton magnetic moment, the fractional precision of the recently reported value can be improved by a factor of at least 1,000. Combined with the present result, this will provide a stringent test of matter/antimatter symmetry with baryons.

  20. Wireless Magnetic-Based Closed-Loop Control of Self-Propelled Microjets

    PubMed Central

    Khalil, Islam S. M.; Magdanz, Veronika; Sanchez, Samuel; Schmidt, Oliver G.; Misra, Sarthak

    2014-01-01

    In this study, we demonstrate closed-loop motion control of self-propelled microjets under the influence of external magnetic fields. We control the orientation of the microjets using external magnetic torque, whereas the linear motion towards a reference position is accomplished by the thrust and pulling magnetic forces generated by the ejecting oxygen bubbles and field gradients, respectively. The magnetic dipole moment of the microjets is characterized using the U-turn technique, and its average is calculated to be 1.310−10 A.m2 at magnetic field and linear velocity of 2 mT and 100 µm/s, respectively. The characterized magnetic dipole moment is used in the realization of the magnetic force-current map of the microjets. This map in turn is used for the design of a closed-loop control system that does not depend on the exact dynamical model of the microjets and the accurate knowledge of the parameters of the magnetic system. The motion control characteristics in the transient- and steady-states depend on the concentration of the surrounding fluid (hydrogen peroxide solution) and the strength of the applied magnetic field. Our control system allows us to position microjets at an average velocity of 115 m/s, and within an average region-of-convergence of 365 m. PMID:24505244

  1. Tensions between opening up and closing down moments in transdisciplinary water research

    NASA Astrophysics Data System (ADS)

    Krueger, Tobias; Maynard, Carly; Carr, Gemma; Bruns, Antje; Mueller, Eva; Lane, Stuart

    2016-04-01

    Research on water is carried out by many disciplines that do not really talk to each other much, despite critical interactions of multiple social and biophysical processes in shaping how much and what kind of water is where, at what time and for whom. What is more, water has meaning to more than those who are scientists. And scientists are not so removed from the things they study as one might commonly believe. All these observations call for a transdisciplinary research agenda that brings together different scientific disciplines with the knowledge that other groups in society hold and that tries to be aware of its own limitations. The transdisciplinary perspective is especially pertinent to the scientific decade 2013-2022 of the International Association of Hydrological Sciences (IAHS) on change in hydrology and society, 'Panta Rhei,' for a balanced conceptualization and study of human-water relations. Transdisciplinarity is inherently about opening up traditional modes of knowledge production; in terms of framing the research problem, the methodology and the knowledge that is considered permissible. This should open up the range of options for management intervention, too. While decisions on how to intervene will inevitably close down the issue periodically, the point here is to leave alternative routes of action open long enough, or reopen them again, so as to counter unsustainable and inequitable path-dependencies and lock-ins. However, opening up efforts are frequently in conflict with factors that work to close down knowledge production. Among those are framings, path-dependencies, vested interests, researchers' positionalities, power, and scale. In this presentation, based on Krueger et al. (2016), we will reflect on the tensions between opening up and closing down moments in transdisciplinary water research and draw important practical lessons. References Krueger, T., Maynard, C.M., Carr, G., Bruns, A., Mueller, E.N. and Lane, S.N. (forthcoming in 2016) A

  2. Orbital magnetic moments in insulating Dirac systems: Impact on magnetotransport in graphene van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Grujić, Marko M.; Tadić, Milan Ž.; Peeters, François M.

    2014-11-01

    In honeycomb Dirac systems with broken inversion symmetry, orbital magnetic moments coupled to the valley degree of freedom arise due to the topology of the band structure, leading to valley-selective optical dichroism. On the other hand, in Dirac systems with prominent spin-orbit coupling, similar orbital magnetic moments emerge as well. These moments are coupled to spin, but otherwise have the same functional form as the moments stemming from spatial inversion breaking. After reviewing the basic properties of these moments, which are relevant for a whole set of newly discovered materials, such as silicene and germanene, we study the particular impact that these moments have on graphene nanoengineered barriers with artificially enhanced spin-orbit coupling. We examine transmission properties of such barriers in the presence of a magnetic field. The orbital moments are found to manifest in transport characteristics through spin-dependent transmission and conductance, making them directly accessible in experiments. Moreover, the Zeeman-type effects appear without explicitly incorporating the Zeeman term in the models, i.e., by using minimal coupling and Peierls substitution in continuum and the tight-binding methods, respectively. We find that a quasiclassical view is able to explain all the observed phenomena.

  3. Finite Volume Study of the Delta Magnetic Moments Using Dynamical Clover Fermions

    SciTech Connect

    Aubin, Christopher; Orginos, Konstantinos; Pascalutsa, Vladimir; Vanderhaeghen, Marc

    2009-01-01

    We calculate the magnetic dipole moment of the $\\Delta$ baryon using a background magnetic field on 2+1-flavors of clover fermions on anisotropic lattices. We focus on the finite volume effects that can be significant in background field studies, and thus we use two different spatial volumes in addition to several quark masses.

  4. Quantum aspects of a moving magnetic quadrupole moment interacting with an electric field

    SciTech Connect

    Fonseca, I. C.; Bakke, K.

    2015-06-15

    The quantum dynamics of a moving particle with a magnetic quadrupole moment that interacts with electric and magnetic fields is introduced. By dealing with the interaction between an electric field and the magnetic quadrupole moment, it is shown that an analogue of the Coulomb potential can be generated and bound state solutions can be obtained. Besides, the influence of the Coulomb-type potential on the harmonic oscillator is investigated, where bound state solutions to both repulsive and attractive Coulomb-type potentials are achieved and the arising of a quantum effect characterized by the dependence of the harmonic oscillator frequency on the quantum numbers of the system is discussed.

  5. Phonon coupling effects in magnetic moments of magic and semimagic nuclei

    NASA Astrophysics Data System (ADS)

    Saperstein, E. E.; Achakovskiy, O. I.; Kamerdzhiev, S. P.; Krewald, S.; Speth, J.; Tolokonnikov, S. V.

    2014-08-01

    Phonon coupling (PC) corrections to magnetic moments of odd neighbors of magic and semimagic nuclei are analyzed within the self-consistent Theory of Finite Fermi Systems (TFFS) based on the Energy Density Functional by S. A. Fayans et al. The perturbation theory in g {/L 2} is used where g L is the phonon-particle coupling vertex. A model is developed with separating non-regular PC contributions, the rest is supposed to be regular and included into the standard TFFS parameters. An ansatz is proposed to take into account the so-called tadpole term which ensures the total angular momentum conservation with g {/L 2} accuracy. An approximate method is suggested to take into account higher-order terms in g {/L 2}. Calculations are carried out for four odd-proton chains, the odd Tl, Bi, In, and Sb ones. Different PC corrections strongly cancel each other. In the result, the total PC correction to the magnetic moment in magic nuclei is, as a rule, negligible. In non-magic nuclei considered it is noticeable and, with only one exception, negative. On average it is of the order of -(0.1-0.5) µ N and improves the agreement of the theory with the data. Simultaneously we calculated the gyromagnetic ratios g {/L ph} of all low-lying phonons in 208Pb. For the 3{1/-} state it is rather close to the Bohr-Mottelson model prediction whereas for other L phonons, two 5- and six positive parity states, the difference from the Bohr-Mottelson values is significant.

  6. Dynamic characteristics of the rotor in a magnetically suspended control moment gyroscope with active magnetic bearing and passive magnetic bearing.

    PubMed

    Tang, Jiqiang; Xiang, Biao; Zhang, Yongbin

    2014-07-01

    For a magnetically suspended control moment gyroscope, stiffness and damping of magnetic bearing will influence modal frequency of a rotor. In this paper the relationship between modal frequency and stiffness and damping has been investigated. The mathematic calculation model of axial passive magnetic bearing (PMB) stiffness is developed. And PID control based on internal model control is introduced into control of radial active magnetic bearing (AMB), considering the radial coupling of axial PMB, a mathematic calculation model of stiffness and damping of radial AMB is established. According to modal analysis, the relationship between modal frequency and modal shapes is achieved. Radial vibration frequency is mainly influenced by stiffness of radial AMB; however, when stiffness increases, radial vibration will disappear and a high frequency bending modal will appear. Stiffness of axial PMB mainly affects the axial vibration mode, which will turn into high-order bending modal. Axial PMB causes bigger influence on torsion modal of the rotor.

  7. Enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 films

    NASA Astrophysics Data System (ADS)

    Moyer, J. A.; Vaz, C. A. F.; Kumah, D. P.; Arena, D. A.; Henrich, V. E.

    2012-11-01

    The effect of film thickness on the magnetic properties of ultrathin Fe-doped cobalt ferrite (Co1-xFe2+xO4) grown on MgO (001) substrates is investigated by superconducting quantum interference device magnetometry and x-ray magnetic linear dichroism, while the distribution of the Co2+ cations between the octahedral and tetrahedral lattice sites is studied with x-ray absorption spectroscopy. For films thinner than 10 nm, there is a large enhancement of the magnetic moment; conversely, the remanent magnetization and coercive fields both decrease, while the magnetic spin axes of all the cations become less aligned with the [001] crystal direction. In particular, at 300 K the coercive fields of the thinnest films vanish. The spectroscopy data show that no changes occur in the cation distribution as a function of film thickness, ruling this out as the origin of the enhanced magnetic moment. However, the magnetic measurements all support the possibility that these ultrathin Fe-doped CoFe2O4 films are transitioning into a superparamagnetic state, as has been seen in ultrathin Fe3O4. A weakening of the magnetic interactions at the antiphase boundaries, leading to magnetically independent domains within the film, could explain the enhanced magnetic moment in ultrathin Fe-doped CoFe2O4 and the onset of superparamagnetism at room temperature.

  8. Magnetic Moment Formation in Graphene Detected by Scattering of Pure Spin Currents

    NASA Astrophysics Data System (ADS)

    Swartz, Adrian; McCreary, Kathy; Chen, Jen-Ru; Han, Wei; Fabian, Jaroslav; Kawakami, Roland

    2013-03-01

    Graphene's 2D nature and high surface sensitivity have led to fascinating predictions for induced spin-based phenomena through careful control of adsorbates, including the extrinsic spin Hall effect, band gap opening, and induced magnetism. By taking advantage of atomic scale control provided by MBE, we have investigated deposition of adsorbates and their interactions with graphene. Spin transport measurements performed in-situ during systematic introduction of atomic hydrogen demonstrated that hydrogen adsorbed on graphene forms magnetic moments that couple via exchange to the injected spin current. The observed behavior is quantitatively explained utilizing a phenomenological theory for scattering of pure spin currents by localized magnetic moments. Lattice vacancies show similar behavior, indicating that the moments originate from so called pz-orbital defects. On the other hand, experiments with charge impurity scatterers such as Mg and Au, are noticeably absent of features related to magnetic moment formation. Furthermore, we observe gate dependent effective exchange fields due to the spin-spin coupling between conduction electrons and magnetic moments, which are of interest for novel phenomena and spintronic functionality but have not been seen previously in graphene.

  9. Phase formation, thermal stability and magnetic moment of cobalt nitride thin films

    SciTech Connect

    Gupta, Rachana; Pandey, Nidhi; Tayal, Akhil; Gupta, Mukul E-mail: dr.mukul.gupta@gmail.com

    2015-09-15

    Cobalt nitride (Co-N) thin films prepared using a reactive magnetron sputtering process are studied in this work. During the thin film deposition process, the relative nitrogen gas flow (R{sub N{sub 2}}) was varied. As R{sub N{sub 2}} increases, Co(N), Co{sub 4}N, Co{sub 3}N and CoN phases are formed. An incremental increase in R{sub N{sub 2}}, after emergence of Co{sub 4}N phase at R{sub N{sub 2}} = 10%, results in a linear increase of the lattice constant (a) of Co{sub 4}N. For R{sub N{sub 2}} = 30%, a maximizes and becomes comparable to its theoretical value. An expansion in a of Co{sub 4}N, results in an enhancement of the magnetic moment, to the extent that it becomes even larger than pure Co. Such larger than pure metal magnetic moment for tetra-metal nitrides (M{sub 4}N) have been theoretically predicted. Incorporation of N atoms in M{sub 4}N configuration results in an expansion of a (relative to pure metal) and enhances the itinerary of conduction band electrons leading to larger than pure metal magnetic moment for M{sub 4}N compounds. Though a higher (than pure Fe) magnetic moment for Fe{sub 4}N thin films has been evidenced experimentally, higher (than pure Co) magnetic moment is evidenced in this work.

  10. EM Induction Experiment to Determine the Moment of a Magnet

    ERIC Educational Resources Information Center

    Najiya Maryam, K. M.

    2014-01-01

    If we drop a magnet through a coil, an emf is induced in the coil according to Faraday's law of electromagnetic induction. Here, such an experiment is done using expEYES kit. The plot of emf versus time has a specific shape with two peaks. A theoretical analysis of this graph is discussed here for both short and long cylindrical magnets.…

  11. Dynamically fluctuating electric dipole moments in fullerene-based magnets

    PubMed Central

    Kambe, Takashi; Oshima, Kokichi

    2014-01-01

    We report here the direct evidence of the existence of a permanent electric dipole moment in both crystal phases of a fullerene-based magnet—the ferromagnetic α-phase and the antiferromagnetic α′-phase of tetra-kis-(dimethylamino)-ethylene-C60 (TDAE-C60)—as determined by dielectric measurements. We propose that the permanent electric dipole originates from the pairing of a TDAE molecule with surrounding C60 molecules. The two polymorphs exhibit clear differences in their dielectric responses at room temperature and during the freezing process with dynamically fluctuating electric dipole moments, although no difference in their room-temperature structures has been previously observed. This result implies that two polymorphs have different local environment around the molecules. In particular, the ferromagnetism of the α-phase is founded on the homogeneous molecule displacement and orientational ordering. The formation of the different phases with respect to the different rotational states in the Jahn–Teller distorted C60s is also discussed. PMID:25236361

  12. Vacuum effects in magnetic field with with account for fermion anomalous magnetic moment and axial-vector interaction

    NASA Astrophysics Data System (ADS)

    Bubnov, Andrey; Gubina, Nadezda; Zhukovsky, Vladimir

    2016-05-01

    We study vacuum polarization effects in the model of Dirac fermions with additional interaction of an anomalous magnetic moment with an external magnetic field and fermion interaction with an axial-vector condensate. The proper time method is used to calculate the one-loop vacuum corrections with consideration for different configurations of the characteristic parameters of these interactions.

  13. Excitation of local magnetic moments by tunneling electrons

    NASA Astrophysics Data System (ADS)

    Gauyacq, Jean-Pierre; Lorente, Nicolás; Novaes, Frederico Dutilh

    2012-05-01

    The advent of milli-kelvin scanning tunneling microscopes (STM) with inbuilt magnetic fields has opened access to the study of magnetic phenomena with atomic resolution at surfaces. In the case of single atoms adsorbed on a surface, the existence of different magnetic energy levels localized on the adsorbate is due to the breaking of the rotational invariance of the adsorbate spin by the interaction with its environment, leading to energy terms in the meV range. These structures were revealed by STM experiments in IBM Almaden in the early 2000s for atomic adsorbates on CuN surfaces. The experiments consisted in the study of the changes in conductance caused by inelastic tunneling of electrons (IETS, inelastic electron tunneling spectroscopy). Manganese and Iron adatoms were shown to have different magnetic anisotropies induced by the substrate. More experiments by other groups followed up, showing that magnetic excitations could be detected in a variety of systems: e.g. complex organic molecules showed that their magnetic anisotropy was dependent on the molecular environment, piles of magnetic molecules showed that they interact via intermolecular exchange interaction, spin waves were excited on ferromagnetic surfaces and in Mn chains, and magnetic impurities have been analyzed on semiconductors. These experiments brought up some intriguing questions: the efficiency of magnetic excitations was very high, the excitations could or could not involve spin flip of the exciting electron and singular-like behavior was sometimes found at the excitation thresholds. These facts called for extended theoretical analysis; perturbation theories, sudden-approximation approaches and a strong coupling scheme successfully explained most of the magnetic inelastic processes. In addition, many-body approaches were also used to decipher the interplay between inelastic processes and the Kondo effect. Spin torque transfer has been shown to be effective in changing spin orientations of an

  14. Orbital magnetic moment instability at the spin reorientation transition of Nd2Fe14B

    PubMed

    Garcia; Chaboy; Bartolome; Goedkoop

    2000-07-10

    Highly accurate soft-XMCD data recorded on a Nd2Fe14B single crystal, through the spin reorientation transition show that the average Fe orbital moment (a) is proportional to the macroscopic Fe anisotropy constant, and (b) diverges 15 K below the reorientation transition temperature. This divergence is indicative of a critical behavior and it is related to a tetragonal distortion. These results give experimental evidence of the mutual dependence between orbital moment, macroscopic magnetic anisotropy, and tetragonal distortion. Furthermore, it is argued that the critical behavior of the orbital moment is at the origin of similar divergences previously observed in Mossbauer and Hall-effect data.

  15. Discovery of Dicke superradiation by system of nuclear magnetic moments

    SciTech Connect

    Kiselev, J.F.; Prudkoglyad, A.F.; Shumovsky, A.S.; Yukalov, V.I. . Lab. of Theoretical Physics)

    1988-01-01

    Spontaneous generation of the Dicke superradiation (SR) state has been found in the system of inversely polarised proton spins with frozen polarisation. SR is observed at the moment when the Larmor frequency crosses the resonance frequency of the passive oscillatory circuit. SR arises from incoherent maser generation of spins. The frequency of a SR generator can be returned from several hundreds of kilohertz to hundreds of megahertz at very low temperatures. Dependence of incoherent and coherent radiation on the initial polarisation has been investigated. A radio frequency analogue of the optical SR laser is shown to be possible both for weak-amplifying and for strong-amplifying active media, depending on the factor of filling and polarisation of nuclei. SR-reverse of negative polarisation is observed in the latter case.

  16. An Alternate Set of Basis Functions for the Electromagnetic Solution of Arbitrarily-Shaped, Three-Dimensional, Closed, Conducting Bodies Using Method of Moments

    NASA Technical Reports Server (NTRS)

    Mackenzie, Anne I.; Baginski, Michael E.; Rao, Sadasiva M.

    2008-01-01

    In this work, we present an alternate set of basis functions, each defined over a pair of planar triangular patches, for the method of moments solution of electromagnetic scattering and radiation problems associated with arbitrarily-shaped, closed, conducting surfaces. The present basis functions are point-wise orthogonal to the pulse basis functions previously defined. The prime motivation to develop the present set of basis functions is to utilize them for the electromagnetic solution of dielectric bodies using a surface integral equation formulation which involves both electric and magnetic cur- rents. However, in the present work, only the conducting body solution is presented and compared with other data.

  17. Addendum to "Updating neutrino magnetic moment constraints" [Phys. Lett. B 753 (2016) 191-198

    NASA Astrophysics Data System (ADS)

    Cañas, B. C.; Miranda, O. G.; Parada, A.; Tórtola, M.; Valle, J. W. F.

    2016-06-01

    After the publication of this work we noticed that the uncertainties in the considered backgrounds in Borexino may affect our reported limit on the neutrino magnetic moment from Borexino data. Indeed, we have found that a more precise treatment of the uncertainties in the total normalization of these backgrounds results in a weaker sensitivity on the neutrino magnetic moment. This point will be hopefully improved in the near future thanks to the purification processes carried out in the second phase of the Borexino experiment. Meanwhile, however, we think it would be more reliable to adopt the bound on the neutrino magnetic moment reported by Borexino: μν < 5.4 ×10-11μB[1].

  18. Neutral current induced {pi}{sup 0} production and neutrino magnetic moment

    SciTech Connect

    Athar, M. Sajjad; Chauhan, S.; Singh, S. K.

    2008-08-01

    We have studied the total cross section, Q{sup 2}, momentum and angular distributions for pions in the {nu}({nu}) induced {pi}{sup 0} production from nucleons. The calculations have been done for the weak production induced by the neutral current in the standard model and the electromagnetic production induced by neutrino magnetic moment. It has been found that with the present experimental limits on the muon neutrino magnetic moment {mu}{sub {nu}{sub {mu}}}, the electromagnetic contribution to the cross section for the {pi}{sup 0} production is small. The neutrino induced neutral current production of {pi}{sup 0}, while giving an alternative method to study the magnetic moment of neutrino {mu}{sub {nu}{sub {mu}}}, does not provide any improvement over the present experimental limit on {mu}{sub {nu}{sub {mu}}} from the observation of this process in future experiments at T2K and NO{nu}A.

  19. Aharonov-Bohm scattering of relativistic Dirac particles with an anomalous magnetic moment

    SciTech Connect

    Lin Qionggui

    2005-10-15

    The Aharonov-Bohm scattering of relativistic spin-1/2 particles with an anomalous magnetic moment are studied. The scattering cross sections for unpolarized and polarized particles are obtained by solving the Dirac-Pauli equation. It is somewhat unexpected that the results are in general the same as those for particles without an anomalous magnetic moment. However, when the incident energy takes some special values, the cross section for polarized particles is dramatically changed. In these cases the helicity of scattered particles is not conserved. In particular, the helicity of particles scattered in the backward direction is all reversed. In the nonrelativistic limit, a very simple relation between the polarized directions of the incident and scattered particles is found, for both general and special incident energies. For particles without an anomalous magnetic moment this relation can be drawn from previous results but it appears to be unnoticed.

  20. A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors.

    PubMed

    Egan, R; Philippe, M; Wera, L; Fagnard, J F; Vanderheyden, B; Dennis, A; Shi, Y; Cardwell, D A; Vanderbemden, P

    2015-02-01

    We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm(3)) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m(2) (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K). PMID:25725888

  1. A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

    NASA Astrophysics Data System (ADS)

    Egan, R.; Philippe, M.; Wera, L.; Fagnard, J. F.; Vanderheyden, B.; Dennis, A.; Shi, Y.; Cardwell, D. A.; Vanderbemden, P.

    2015-02-01

    We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm3) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m2 (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K).

  2. Magnetic moment formation due to arsenic vacancies in LaFeAsO-derived superconductors.

    PubMed

    Kikoin, Konstantin; Drechsler, Stefan-Ludwig; Koepernik, Klaus; Málek, Jiři; van den Brink, Jeroen

    2015-07-14

    Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic vacancy orient ferromagnetically and cause a substantial enhancement of the paramagnetic susceptibility in both the normal and superconducting state. The qualitative model description is supported by first principles band structure calculations of the As-vacancy related defect spectrum within a larger supercell.

  3. Magnetic moment formation due to arsenic vacancies in LaFeAsO-derived superconductors

    PubMed Central

    Kikoin, Konstantin; Drechsler, Stefan-Ludwig; Koepernik, Klaus; Málek, Jiři; van den Brink, Jeroen

    2015-01-01

    Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic vacancy orient ferromagnetically and cause a substantial enhancement of the paramagnetic susceptibility in both the normal and superconducting state. The qualitative model description is supported by first principles band structure calculations of the As-vacancy related defect spectrum within a larger supercell. PMID:26169486

  4. Dynamic circuit and Fourier series methods for moment calculation in electrodynamic repulsive magnetic levitation systems

    NASA Astrophysics Data System (ADS)

    Knowles, R.

    1982-07-01

    A general theory of moments for electrodynamic magnetic levitation systems has been developed using double Fourier series and dynamic circuit principles. Both employ Parseval's theorem using either wave constant derivatives or the polar waveconstant principle of the Fourier-Bessel/double Fourier series equivalence. A method for calculating angular derivatives of moments and forces is explained, and for all of these methods comparisons are made with experimental results obtained for single and split rail configurations. Extensions of dynamic circuit theory for tilted nonflat and circular magnets are also explained.

  5. Magnetic moment formation due to arsenic vacancies in LaFeAsO-derived superconductors.

    PubMed

    Kikoin, Konstantin; Drechsler, Stefan-Ludwig; Koepernik, Klaus; Málek, Jiři; van den Brink, Jeroen

    2015-01-01

    Arsenic vacancies in LaFeAsO-derived superconductors are nominally non-magnetic defects. However, we find from a microscopic theory in terms of an appropriately modified Anderson-Wolff model that in their vicinity local magnetic moments form. They can arise because removing an arsenic atom breaks four strong, covalent bonds with the neighboring iron atoms. The moments emerging around an arsenic vacancy orient ferromagnetically and cause a substantial enhancement of the paramagnetic susceptibility in both the normal and superconducting state. The qualitative model description is supported by first principles band structure calculations of the As-vacancy related defect spectrum within a larger supercell. PMID:26169486

  6. Large anomalous magnetic moment in three-dimensional Dirac and Weyl semimetals

    NASA Astrophysics Data System (ADS)

    van der Wurff, E. C. I.; Stoof, H. T. C.

    2016-10-01

    We investigate the effect of Coulomb interactions on the electromagnetic response of three-dimensional Dirac and Weyl semimetals. In a calculation reminiscent of Schwinger's seminal work on quantum electrodynamics, we find three physically distinct effects for the anomalous magnetic moment of the relativisticlike quasiparticles in the semimetal. In the case of nonzero doping, the anomalous magnetic moment is finite at long wavelengths and typically orders of magnitude larger than Schwinger's result. We also find interesting effects of one of the three new Hamiltonian terms on the topological surface states at the interface between vacuum and a Weyl semimetal. We conclude that observation of these effects should be within experimental reach.

  7. Majorana neutrino magnetic moments in the gauge-mediated supersymmetry breaking MSSM

    SciTech Connect

    Gozdz, Marek; Kaminski, Wieslaw A.

    2009-04-01

    Supersymmetric models with broken R parity provide mechanisms that allow to generate Majorana neutrino masses and magnetic moments through virtual particle-sparticle loops. This constitutes an attractive alternative to the seesaw mechanism. In this paper, we present a detailed calculation of the transition magnetic moments of a Majorana neutrino in gauge-mediated supersymmetry breaking minimal supersymmetric standard model (MSSM) without R parity. We base our analysis on the renormalization group evolution of the MSSM parameters, which are unified at the grand unified theory scale.

  8. Prediction of magnetic moment collapse in ZrFe{sub 2} under hydrostatic pressure

    SciTech Connect

    Zhang, Wenxu; Zhang, Wanli

    2015-04-28

    Electronic structure and magnetic properties of ZrFe{sub 2} in the cubic Laves phase are investigated by calculations based on density functional theory. The magnetic moment decreases with the increase of the hydrostatic pressure in an unusual way: Two-step magnetic collapse is predicted. The first one is a continuous change from 1.53 μ{sub B}/Fe to 0.63 μ{sub B}/Fe at about 3.6 GPa, and the other is from 0.25 μ{sub B}/Fe to the nonmagnetic state at about 15 GPa in a first order manner under the local spin density approximation of the exchange correlation potential. A metastable state with intermediate spin moment about 0.15 μ{sub B}/Fe may exist before that. We understand this process by the changes of density of states during it. The magnetic moment decreases under the pressure in the vicinity of the experimental lattice constant with dlnm/dp=−0.038 GPa{sup −1}. The spontaneous volume magnetostriction is 3.6%, which is huge enough to find potential applications in magnetostriction actuators and sensors. We suggest that the Invar effect of this compound may be understood when considering the magnetic moment variation according to the magnetostrictive model of Invar.

  9. Nuclear Magnetic Dipole and Electric Quadrupole Moments: Their Measurement and Tabulation as Accessible Data

    SciTech Connect

    Stone, N. J.

    2015-09-15

    The most recent tabulations of nuclear magnetic dipole and electric quadrupole moments have been prepared and published by the Nuclear Data Section of the IAEA, Vienna [N. J. Stone, Report No. INDC(NDS)-0650 (2013); Report No. INDC(NDS)-0658 (2014)]. The first of these is a table of recommended quadrupole moments for all isotopes in which all experimental results are made consistent with a limited number of adopted standards for each element; the second is a combined listing of all measurements of both moments. Both tables cover all isotopes and energy levels. In this paper, the considerations relevant to the preparation of both tables are described, together with observations as to the importance and (where appropriate) application of necessary corrections to achieve the “best” values. Some discussion of experimental methods is included with emphasis on their precision. The aim of the published quadrupole moment table is to provide a standard reference in which the value given for each moment is the best available and for which full provenance is given. A table of recommended magnetic dipole moments is in preparation, with the same objective in view.

  10. Ni endohedral-doped C60 with duality of magnetic moments

    NASA Astrophysics Data System (ADS)

    Li, J. L.; Yang, G. W.

    2010-06-01

    We have performed the magnetic properties of Ni endohedral-doped C60 (Ni@C60) by the spin-polarized density functional calculations, and showed that there are three stable configurations depending on different sites of the doped Ni atoms. Due to the high hybridization and confinement effects, the magnetic moment of the Ni-encapsulated metallofullerenes has duality, i.e., altering between 2.02μB and zero, by positioning the Ni atom in the hollow cage of C60. These findings of the alternative magnetic moments of the Ni-encapsulated C60 implied that Ni@C60 could be expected to be promising as a single molecular magnetic switch.

  11. Multi-moment advection scheme in three dimension for Vlasov simulations of magnetized plasma

    SciTech Connect

    Minoshima, Takashi; Matsumoto, Yosuke; Amano, Takanobu

    2013-03-01

    We present an extension of the multi-moment advection scheme [T. Minoshima, Y. Matsumoto, T. Amano, Multi-moment advection scheme for Vlasov simulations, Journal of Computational Physics 230 (2011) 6800–6823] to the three-dimensional case, for full electromagnetic Vlasov simulations of magnetized plasma. The scheme treats not only point values of a profile but also its zeroth to second order piecewise moments as dependent variables, and advances them on the basis of their governing equations. Similar to the two-dimensional scheme, the three-dimensional scheme can accurately solve the solid body rotation problem of a gaussian profile with little numerical dispersion or diffusion. This is a very important property for Vlasov simulations of magnetized plasma. We apply the scheme to electromagnetic Vlasov simulations. Propagation of linear waves and nonlinear evolution of the electron temperature anisotropy instability are successfully simulated with a good accuracy of the energy conservation.

  12. Effect of longitudinal degree of freedom of magnetic moment in body-centered-cubic iron

    SciTech Connect

    Yin, Junqi; Eisenbach, Markus; Nicholson, Don M; Rusanu, Aurelian

    2013-01-01

    First principle calculations are performed to study the longitudinal degree of freedom of the magnetic moment in BCC iron. A model of the Heisenberg type of exchange interaction is proposed, which couples the spin and lattice degrees of freedom. Monte Carlo simulations are then applied to study the effect of thermal displacements on the magnetic phase transition in BCC Iron. The reason for the surprising success of fixed lattice Heisenberg models is explained.

  13. Deuteron and triton magnetic moments from NMR spectra of the hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Puchalski, Mariusz; Komasa, Jacek; Pachucki, Krzysztof

    2015-08-01

    We present a theory and calculations of the nuclear magnetic shielding with finite nuclear mass effects and determine the magnetic moments of deuteron and triton using the known NMR spectra of HD and HT molecules. The results μd=0.857 438 234 6 (53 ) μN and μt=2.978 962 471 (10 ) μN are more accurate and in good agreement with the currently accepted values.

  14. Sum rules for magnetic moments and polarizabilities in QED and chiral effective-field theory

    SciTech Connect

    Barry Holstein; Vladimir Pascalutsa; Marc Vanderhaeghen

    2005-08-01

    We elaborate on a recently proposed extension of the Gerasimov-Drell-Hearn (GDH) sum rule which is achieved by taking derivatives with respect to the anomalous magnetic moment. The new sum rule features a linear relation between the anomalous magnetic moment and the dispersion integral over a cross-section quantity. We find some analogy of the linearized form of the GDH sum rule with the ''sideways dispersion relations''. As an example, we apply the linear sum rule to reproduce the famous Schwinger's correction to the magnetic moment in QED from a tree-level cross-section calculation and outline the procedure for computing the two-loop correction from a one-loop cross-section calculation. The polarizabilities of the electron in QED are considered as well by using the other forward-Compton-scattering sum rules. We also employ the sum rules to study the magnetic moment and polarizabilities of the nucleon in a relativistic chiral EFT framework. In particular we investigate the chiral extrapolation of these quantities.

  15. A light Zeldovich-Konopinski-Mahmoud neutrino with a large magnetic moment

    NASA Astrophysics Data System (ADS)

    Ecker, G.; Grimus, W.; Neufeld, H.

    1989-11-01

    We propose a non-abelian extension of a Zeldovich-Konopinski-Mahmoud lepton number symmetry which gives rise to a naturally light Dirac neutrino with a magnetic moment of O(10 -11μB). The neutrino mass appears first at the two-loop level and is well below the experimental upper bound.

  16. High-precision evaluation of the magnetic moment of the helion

    SciTech Connect

    Neronov, Yu. I. Seregin, N. N.

    2012-11-15

    NMR spectra of samples containing a mixture of hydrogen deuteride HD with pressure of about 80 atm and helium-3 with partial pressure of about 1 atm are analyzed. The ratio of the resonance frequencies of the nuclei, F({sup 3}He)/F(H{sub 2}), is determined to be 0.761786594(2), which is equal to the magnetic moment of the helion (bound in a helium atom) in the units of the magnetic moment of a proton (bound in molecular hydrogen). The uncertainty of two digits in the last place corresponds to a relative error of {delta}[F({sup 3}He)/F(H{sub 2})] = 2.6 Multiplication-Sign 10{sup -9}. The use of the known calculated data on the shielding of nuclei in the helium-3 atom ({sigma}({sup 3}He) = 59924(2) Multiplication-Sign 10{sup -9}) and on the shielding of protons in hydrogen ({sigma}(H{sub 2}) = 26288(2) Multiplication-Sign 10{sup -9}) yields a value of {mu}({sup 3}He)/{mu}{sub p} = -0.761812217(3) for the free magnetic moment of the helion in the units of the proton magnetic moment.

  17. Yukawa coupling and anomalous magnetic moment of the muon: An update for the LHC era

    SciTech Connect

    Crivellin, Andreas; Girrbach, Jennifer; Nierste, Ulrich

    2011-03-01

    We study the interplay between a soft muon Yukawa coupling generated radiatively with the trilinear A-terms of the minimal supersymmetric standard model (MSSM) and the anomalous magnetic moment of the muon. In the absence of a tree-level muon Yukawa coupling the lightest smuon mass is predicted to be in the range between 600 GeV and 2200 GeV at 2{sigma}, if the bino mass M{sub 1} is below 1 TeV. Therefore, a detection of a smuon (in conjunction with a sub-TeV bino) at the LHC would directly imply a nonzero muon Yukawa coupling in the MSSM superpotential. Inclusion of slepton flavor mixing could in principle lower the mass of one smuonlike slepton below 600 GeV. However, the experimental bounds on radiative lepton decays instead strengthen the lower mass bound, with larger effects for smaller M{sub 1}, We also extend the analysis to the electron case and find that a light selectron close to the current experimental search limit may prove the MSSM electron Yukawa coupling to be nonzero.

  18. Electromagnetic Currents and Magnetic Moments in $\\chi$EFT

    SciTech Connect

    Saori Pastore, Luca Girlanda, Rocco Schiavilla, Michele Viviani, Robert Wiringa

    2009-09-01

    A two-nucleon potential and consistent electromagnetic currents are derived in chiral effective field theory ($\\chi$EFT) at, respectively, $Q^{\\, 2}$ (or N$^2$LO) and $e\\, Q$ (or N$^3$LO), where $Q$ generically denotes the low-momentum scale and $e$ is the electric charge. Dimensional regularization is used to renormalize the pion-loop corrections. A simple expression is derived for the magnetic dipole ($M1$) operator associated with pion loops, consisting of two terms, one of which is determined, uniquely, by the isospin-dependent part of the two-pion-exchange potential. This decomposition is also carried out for the $M1$ operator arising from contact currents, in which the unique term is determined by the contact potential. Finally, the low-energy constants (LEC's) entering the N$^2$LO potential are fixed by fits to the $np$ S- and P-wave phase shifts up to 100 MeV lab energies. Three additional LEC's are needed to completely specify the $M1$ operator at N$^3$L

  19. Search for Trapped Electrons and a Magnetic Moment at Mars by Mariner IV.

    PubMed

    O'gallagher, J J; Simpson, J A

    1965-09-10

    The Mariner IV spacecraft on 14-15 July 1965 passed within 9850 kilometers of Mars, carrying a solid-state charged-particle telescope which could detect electrons greater than 40 kiloelectron volts and protons greater than 1 million electron volts. The trajectory could have passed through a bow shock, a transition region, and a magnetospheric boundary where particles could be stably trapped for a wide range of Martian magnetic moments. No evidence of charged-particle radiation was found in any of these regions. In view of these results, an upper limit is established for the Martian magnetic moment provided it is assumed that the same physical processes leading to acceleration and trapping of electrons in Earth's magnetic field would be found in a Martian magnetic field. On this basis, the upper limit for the Martian magnetic moment is 0.1 percent that of Earth for a wide range of postulated orientations with respect to the rotational axis of Mars. The implications of these results for the physical and biological environment of Mars are briefly discussed.

  20. Evidence of Charge Transfer and Orbital Magnetic Moment in Multiferroic CuFeO2

    NASA Astrophysics Data System (ADS)

    Narumi, Yasuo; Nakamura, Tetsuya; Ikeno, Hidekazu; Terada, Noriki; Morioka, Takayuki; Saito, Kota; Kitazawa, Hideaki; Kindo, Koichi; Nojiri, Hiroyuki

    2016-11-01

    Soft X-ray absorption spectra (XAS) and magnetic circular dichroism (XMCD) of Fe and Cu L2,3 edges have been measured on the triangular lattice antiferromagnet CuFeO2. By applying sum rule analysis to the XMCD of Fe, the ratio of the orbital to spin magnetic moments is determined to be -0.071. Because the nominal valence of Fe in CuFeO2 was Fe3+ (3d5), the orbital magnetic moment was considered to be zero in the past. However, the present research demonstrates that the orbital magnetic moment of Fe takes a finite value and it is possibly due to Fe4+ (3d4), which is considered to be responsible for the strong magnetic anisotropy and the ferroelectricity. We compare the experimental results with the results of ab initio multiplet calculations based on the configuration interaction theory and discuss the anomalous electronic structures of Fe and Cu ions in CuFeO2.

  1. (129) Xe and (131) Xe nuclear magnetic dipole moments from gas phase NMR spectra.

    PubMed

    Makulski, Włodzimierz

    2015-04-01

    (3) He, (129) Xe and (131) Xe NMR measurements of resonance frequencies in the magnetic field B0=11.7586 T in different gas phase mixtures have been reported. Precise radiofrequency values were extrapolated to the zero gas pressure limit. These results combined with new quantum chemical values of helium and xenon nuclear magnetic shielding constants were used to determine new accurate nuclear magnetic moments of (129) Xe and (131) Xe in terms of that of the (3) He nucleus. They are as follows: μ((129) Xe) = -0.7779607(158)μN and μ((131) Xe) = +0.6918451(70)μN . By this means, the new 'helium method' for estimations of nuclear dipole moments was successfully tested. Gas phase NMR spectra demonstrate the weak intermolecular interactions observed on the (3) He and (129) Xe and (131) Xe shielding in the gaseous mixtures with Xe, CO2 and SF6 .

  2. Magnetic Moments of Delta and Omega- baryons with dynamical clover fermions

    SciTech Connect

    Aubin, Christopher; Orginos, Konstantinos; Pascalutsa, Vladimir; Vanderhaeghen, Marc

    2009-01-01

    We calculate the magnetic dipole moment of the Delta(1232) and Omega- baryons with 2+1-flavors of clover fermions on anisotropic lattices using a background magnetic field. This is the first dynamical calculation of these magnetic moments using a background field technique. The calculation for Omega- is done at the physical strange quark mass, with the result in units of the physical nuclear magneton µ_(Omega-) = -1.93(8)(12) (where the first error is statistical and the second is systematic) compared to the experimental number: -2.02(5). The Delta has been studied at three unphysical quark masses, corresponding to pion mass 366, 438, and 548 MeV. The pion-mass dependence is compared with the behavior obtained from chiral effective-field theory.

  3. Magnetic moments of octet baryons, angular momenta of quarks, and sea antiquark polarizations

    SciTech Connect

    Bartelski, Jan; Tatur, Stanislaw

    2010-03-01

    One can determine antiquark polarizations in a proton using the information from deep inelastic scattering, {beta} decays of baryons, orbital angular momenta of quarks, as well as their integrated magnetic distributions. The last quantities were determined previously by us performing a fit to magnetic moments of a baryon octet. However, because of the SU(3) symmetry our results depend on two parameters. The quantity {Gamma}{sub V}, measured recently in a COMPASS experiment, gives the relation between these parameters. We can fix the last unknown parameter using the ratio of up and down quark magnetic moments which one can get from the fit to radiative vector meson decays. We calculate antiquark polarizations with the orbital momenta of valence quarks that follow from lattice calculations. The value of the difference of up and down antiquark polarizations obtained in our calculations is consistent with the result obtained in a HERMES experiment.

  4. Decoherence-governed magnetic-moment dynamics of supported atomic objects

    NASA Astrophysics Data System (ADS)

    Gauyacq, Jean-Pierre; Lorente, Nicolás

    2015-11-01

    Due to the quantum evolution of molecular magnetic moments, the magnetic state of nanomagnets can suffer spontaneous changes. This process can be completely quenched by environment-induced decoherence. However, we show that for typical small supported atomic objects, the substrate-induced decoherence does change the magnetic-moment evolution but does not quell it. To be specific and to compare with experiment, we analyze the spontaneous switching between two equivalent magnetization states of atomic structures formed by Fe on Cu2N/Cu (1 0 0), measured by Loth et al (2012 Science 335 196-9). Due to the substrate-induced decoherence, the Rabi oscillations proper to quantum tunneling between magnetic states are replaced by an irreversible decay of long characteristic times leading to the observed stochastic magnetization switching. We show that the corresponding switching rates are small, rapidly decreasing with system’s size, with a 1/T thermal behavior and in good agreement with experiments. Quantum tunneling is recovered as the switching mechanism at extremely low temperatures below the μK range for a six-Fe-atom system and exponentially lower for larger atomic systems. The unexpected conclusion of this work is that experiments could detect the switching of these supported atomic systems because their magnetization evolution is somewhere between complete decoherence-induced stability and unobservably fast quantum-tunneling switching.

  5. Decoherence-governed magnetic-moment dynamics of supported atomic objects.

    PubMed

    Gauyacq, Jean-Pierre; Lorente, Nicolás

    2015-11-18

    Due to the quantum evolution of molecular magnetic moments, the magnetic state of nanomagnets can suffer spontaneous changes. This process can be completely quenched by environment-induced decoherence. However, we show that for typical small supported atomic objects, the substrate-induced decoherence does change the magnetic-moment evolution but does not quell it. To be specific and to compare with experiment, we analyze the spontaneous switching between two equivalent magnetization states of atomic structures formed by Fe on Cu2N/Cu (1 0 0), measured by Loth et al (2012 Science 335 196-9). Due to the substrate-induced decoherence, the Rabi oscillations proper to quantum tunneling between magnetic states are replaced by an irreversible decay of long characteristic times leading to the observed stochastic magnetization switching. We show that the corresponding switching rates are small, rapidly decreasing with system's size, with a 1/T thermal behavior and in good agreement with experiments. Quantum tunneling is recovered as the switching mechanism at extremely low temperatures below the μK range for a six-Fe-atom system and exponentially lower for larger atomic systems. The unexpected conclusion of this work is that experiments could detect the switching of these supported atomic systems because their magnetization evolution is somewhere between complete decoherence-induced stability and unobservably fast quantum-tunneling switching. PMID:26471260

  6. Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head.

    PubMed

    Tao, Y; Eichler, A; Holzherr, T; Degen, C L

    2016-01-01

    Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins and nanoscale magnetic resonance imaging. Here we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 μB Hz(-1/2), equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 × 10(6) T m(-1) and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with ∼10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation and mesoscopic physics. PMID:27647039

  7. Magnetic structure of Yb2Pt2Pb: Ising moments on the Shastry-Sutherland lattice

    DOE PAGES

    Miiller, W.; Zaliznyak, I.; Wu, L. S.; Kim, M. S.; Orvis, T.; Simonson, J. W.; Gamza, M.; McNally, D. M.; Nelson, C. S.; Ehlers, G.; et al

    2016-03-22

    Neutron diffraction measurements were carried out on single crystals and powders of Yb2Pt2Pb, where Yb moments form two interpenetrating planar sublattices of orthogonal dimers, a geometry known as Shastry-Sutherland lattice, and are stacked along the c axis in a ladder geometry. Yb2Pt2Pb orders antiferromagnetically at TN=2.07K, and the magnetic structure determined from these measurements features the interleaving of two orthogonal sublattices into a 5×5×1 magnetic supercell that is based on stripes with moments perpendicular to the dimer bonds, which are along (110) and (–110). Magnetic fields applied along (110) or (–110) suppress the antiferromagnetic peaks from an individual sublattice, butmore » leave the orthogonal sublattice unaffected, evidence for the Ising character of the Yb moments in Yb2Pt2Pb that is supported by point charge calculations. Furthermore, specific heat, magnetic susceptibility, and electrical resistivity measurements concur with neutron elastic scattering results that the longitudinal critical fluctuations are gapped with ΔE≃0.07meV.« less

  8. Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head

    PubMed Central

    Tao, Y.; Eichler, A.; Holzherr, T.; Degen, C. L.

    2016-01-01

    Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins and nanoscale magnetic resonance imaging. Here we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 μB Hz−1/2, equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 × 106 T m−1 and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with ∼10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation and mesoscopic physics. PMID:27647039

  9. Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head

    NASA Astrophysics Data System (ADS)

    Tao, Y.; Eichler, A.; Holzherr, T.; Degen, C. L.

    2016-09-01

    Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins and nanoscale magnetic resonance imaging. Here we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 μB Hz-1/2, equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 × 106 T m-1 and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with ~10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation and mesoscopic physics.

  10. Ultrasensitive mechanical detection of magnetic moment using a commercial disk drive write head.

    PubMed

    Tao, Y; Eichler, A; Holzherr, T; Degen, C L

    2016-09-20

    Sensitive detection of weak magnetic moments is an essential capability in many areas of nanoscale science and technology, including nanomagnetism, quantum readout of spins and nanoscale magnetic resonance imaging. Here we show that the write head of a commercial hard drive may enable significant advances in nanoscale spin detection. By approaching a sharp diamond tip to within 5 nm from a write pole and measuring the induced diamagnetic moment with a nanomechanical force transducer, we demonstrate a spin sensitivity of 0.032 μB Hz(-1/2), equivalent to 21 proton magnetic moments. The high sensitivity is enabled in part by the pole's strong magnetic gradient of up to 28 × 10(6) T m(-1) and in part by the absence of non-contact friction due to the extremely flat writer surface. In addition, we demonstrate quantitative imaging of the pole field with ∼10 nm spatial resolution. We foresee diverse applications for write heads in experimental condensed matter physics, especially in spintronics, ultrafast spin manipulation and mesoscopic physics.

  11. Magnetic moment of single vortices in YBCO nano-superconducting particle: Eilenberger approach

    NASA Astrophysics Data System (ADS)

    Zakharchuk, I.; Sharafeev, A.; Belova, P.; Safonchik, M.; Traito, K. B.; Lähderanta, E.

    2013-12-01

    Temperature dependence of single vortex magnetic moment in nanosize superconducting particles is investigated in the framework of quasiclassical Eilenberger approach. Such nanoparticles can be used for preparation of high-quality superconducting thin films with high critical current density. In contrast to bulk materials where the vortex magnetic moment is totally determined by flux quantum, in nano-sized specimens (with characteristic size, D, much less than effective penetration depth, λeff) the quantization rule is violated and magnetic moment is proportional to D2/λ2eff(T). Due to strong repulsion between vortices in nanoparticles only a single vortex can be trapped in them. Because of small size of particles the screening current of the vortex is located near the vortex core where the current is quite high and comparable to depairing currents. Therefore, the superconducting electron density, ns, depends on the current value and the distance from the vortex core. This effect is especially important for superconductors having gap nodes, such as YBCO. The current dependence of ns in nanoparticles is analogous to the Volovik effect in flux-line lattice in bulk samples. The magnitude of the effect can be obtained by comparing the temperature dependence of magnetic moment in the vortex and in the Meissner states. In the last case the value of screening current is small and superconducting response to the external field is determined by London penetration depth. Because of importance of nonlinear and nonlocal effects, the quantum mechanical Eilenberger approach is applied for description of the vortex in nanoparticles. The flattening of 1/λ2eff(T) dependence has been found. A comparison of the theoretical results with experimental magnetization data in Meissner and mixed states of YBCO nanopowders has been done. The presence of nonlinear and nonlocal effects in vortex current distribution is clearly visible. The obtained results are important for the description

  12. Large enhancement of magnetic moment in L1(0) ordered FePt thin films by Nd substitutional doping

    SciTech Connect

    Xu, D. B.; Sun, C J; Chen, J. S.; Heald, S M; Sanyal, B.; Rosenberg, R. A.; Zhou, T. J.; Chow, G. M.

    2015-07-01

    We studied L1(0) ordered Fe50Pt50-xNdx alloy films, which showed a large enhancement (similar to 18.4% at room temperature and similar to 11.7% at 10 K) of magnetic moment with 6 atomic % of Nd. Analysis of the x-ray magnetic circular dichroism spectra at the Fe L-3,L-2 edges and Nd M-5,M-4 edges in Fe50Pt44Nd6 films indicated a significant contribution of the Nd orbital moment. The origin of the large enhancement of magnetic moment was attributed to the effect of ferromagnetic coupling of the total magnetic moments between Fe and Nd. Density functional theory based first principles calculations supported the experimental observations of increasing moment due to Nd substitution of Pt.

  13. The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters.

    PubMed

    Meyer, Jennifer; Tombers, Matthias; van Wüllen, Christoph; Niedner-Schatteburg, Gereon; Peredkov, Sergey; Eberhardt, Wolfgang; Neeb, Matthias; Palutke, Steffen; Martins, Michael; Wurth, Wilfried

    2015-09-14

    We present size dependent spin and orbital magnetic moments of cobalt (Con (+), 8 ≤ n ≤ 22), iron (Fen (+), 7 ≤ n ≤ 17), and nickel cluster (Nin (+), 7 ≤ n ≤ 17) cations as obtained by X-ray magnetic circular dichroism (XMCD) spectroscopy of isolated clusters in the gas phase. The spin and orbital magnetic moments range between the corresponding atomic and bulk values in all three cases. We compare our findings to previous XMCD data, Stern-Gerlach data, and computational results. We discuss the application of scaling laws to the size dependent evolution of the spin and orbital magnetic moments per atom in the clusters. We find a spin scaling law "per cluster diameter," ∼n(-1/3), that interpolates between known atomic and bulk values. In remarkable contrast, the orbital moments do likewise only if the atomic asymptote is exempt. A concept of "primary" and "secondary" (induced) orbital moments is invoked for interpretation.

  14. The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters.

    PubMed

    Meyer, Jennifer; Tombers, Matthias; van Wüllen, Christoph; Niedner-Schatteburg, Gereon; Peredkov, Sergey; Eberhardt, Wolfgang; Neeb, Matthias; Palutke, Steffen; Martins, Michael; Wurth, Wilfried

    2015-09-14

    We present size dependent spin and orbital magnetic moments of cobalt (Con (+), 8 ≤ n ≤ 22), iron (Fen (+), 7 ≤ n ≤ 17), and nickel cluster (Nin (+), 7 ≤ n ≤ 17) cations as obtained by X-ray magnetic circular dichroism (XMCD) spectroscopy of isolated clusters in the gas phase. The spin and orbital magnetic moments range between the corresponding atomic and bulk values in all three cases. We compare our findings to previous XMCD data, Stern-Gerlach data, and computational results. We discuss the application of scaling laws to the size dependent evolution of the spin and orbital magnetic moments per atom in the clusters. We find a spin scaling law "per cluster diameter," ∼n(-1/3), that interpolates between known atomic and bulk values. In remarkable contrast, the orbital moments do likewise only if the atomic asymptote is exempt. A concept of "primary" and "secondary" (induced) orbital moments is invoked for interpretation. PMID:26374030

  15. The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters

    NASA Astrophysics Data System (ADS)

    Meyer, Jennifer; Tombers, Matthias; van Wüllen, Christoph; Niedner-Schatteburg, Gereon; Peredkov, Sergey; Eberhardt, Wolfgang; Neeb, Matthias; Palutke, Steffen; Martins, Michael; Wurth, Wilfried

    2015-09-01

    We present size dependent spin and orbital magnetic moments of cobalt (Con+, 8 ≤ n ≤ 22), iron (Fen+, 7 ≤ n ≤ 17), and nickel cluster (Nin+, 7 ≤ n ≤ 17) cations as obtained by X-ray magnetic circular dichroism (XMCD) spectroscopy of isolated clusters in the gas phase. The spin and orbital magnetic moments range between the corresponding atomic and bulk values in all three cases. We compare our findings to previous XMCD data, Stern-Gerlach data, and computational results. We discuss the application of scaling laws to the size dependent evolution of the spin and orbital magnetic moments per atom in the clusters. We find a spin scaling law "per cluster diameter," ˜n-1/3, that interpolates between known atomic and bulk values. In remarkable contrast, the orbital moments do likewise only if the atomic asymptote is exempt. A concept of "primary" and "secondary" (induced) orbital moments is invoked for interpretation.

  16. Research Update: Plentiful magnetic moments in oxygen deficient SrTiO{sub 3}

    SciTech Connect

    Lopez-Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter B.

    2015-10-01

    Correlated band theory is employed to investigate the magnetic and electronic properties of different arrangements of oxygen di- and tri-vacancy clusters in SrTiO{sub 3}. Hole and electron doping of oxygen deficient SrTiO{sub 3} yields various degrees of magnetization as a result of the interaction between localized magnetic moments at the defect sites. Different kinds of Ti atomic orbital hybridization are described as a function of the doping level and defect geometry. We find that magnetism in SrTiO{sub 3−δ} is sensitive to the arrangement of neighbouring vacancy sites, charge carrier density, and vacancy-vacancy interaction. Permanent magnetic moments in the absence of vacancy doping electrons are observed. Our description of the charged clusters of oxygen vacancies widens the previous descriptions of mono- and multi-vacancies and points out the importance of the controlled formation at the atomic level of defects for the realization of transition metal oxide based devices with a desirable magnetic performance.

  17. Plentiful magnetic moments in oxygen deficient SrTiO3.

    SciTech Connect

    Lopez Bezanilla, Alejandro; Ganesh, P.; Littlewood, Peter B.

    2015-10-01

    Correlated band theory is employed to investigate the magnetic and electronic properties of different arrangements of oxygen di- and tri-vacancy clusters in SrTiO3. Hole and electron doping of oxygen deficient SrTiO3 yields various degrees of magnetization as a result of the interaction between localized magnetic moments at the defected sites. Different kinds of Ti atomic orbital hybridization are described as a function of the doping level and defect geometry. We find that magnetism in SrTiO3-d is sensitive to the arrangement of neighbouring vacancy sites, charge carrier density, and vacancy-vacancy interaction. Permanent magnetic moments in the absence of vacancy doping electrons are observed. Our description of the charged clusters of oxygen vacancies widens the previous descriptions of mono and multi-vacancies and points out the importance of the controlled formation at the atomic level of defects for the realization of transition metal oxide based devices with a desirable magnetic performance.

  18. Mapping motion of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers.

    PubMed

    Zhou, X; Ma, L; Shi, Z; Fan, W J; Evans, R F L; Zheng, Jian-Guo; Chantrell, R W; Mangin, S; Zhang, H W; Zhou, S M

    2015-01-01

    In this work, disordered-IrMn3/insulating-Y3Fe5O12 exchange-biased bilayers are studied. The behavior of the net magnetic moment ΔmAFM in the antiferromagnet is directly probed by anomalous and planar Hall effects, and anisotropic magnetoresistance. The ΔmAFM is proved to come from the interfacial uncompensated magnetic moment. We demonstrate that the exchange bias and rotational hysteresis loss are induced by partial rotation and irreversible switching of the ΔmAFM. In the athermal training effect, the state of the ΔmAFM cannot be recovered after one cycle of hysteresis loop. This work highlights the fundamental role of the ΔmAFM in the exchange bias and facilitates the manipulation of antiferromagnetic spintronic devices.

  19. Analysis of Electric Field Induced by ELF Magnetic Field Utilizing Generalized Equivalent Multipole-Moment Method

    NASA Astrophysics Data System (ADS)

    Hamada, Shoji; Yamamoto, Osamu; Kobayashi, Tetsuo

    This paper presents a generalized equivalent multipole-moment method for calculating three-dimensional Laplacian fields in multi-spherical system. The Greengard & Rokhlin's M2M, M2L, and L2L formulae enable the multipole-moment method to calculate the fields in general arrangement of multi-spheres, which involve exclusive and multi-layered spherical arrangement. We applied this method to electric field calculation in biological structures induced by ELF magnetic fields. The induced electric fields in a three eccentric and exclusive spheres system, which models human head with two eyeballs, are calculated under the application of homogeneous and magnetic-dipole fields. The validity of this method is successfully confirmed by comparing the calculated fields with those by the fast-multipole surface-charge-simulation method.

  20. Orbital magnetic moment and extrinsic spin Hall effect for iron impurities in gold

    NASA Astrophysics Data System (ADS)

    Shick, Alexander B.; Kolorenč, Jindřich; Janiš, Václav; Lichtenstein, Alexander I.

    2011-09-01

    We report electronic structure calculations of an iron impurity in a gold host. The spin, orbital, and dipole magnetic moments were investigated using the local density approximation (LDA) + U correlated band theory. We show that the around-mean-field LDA + U reproduces the x-ray magnetic circular dichroism (XMCD) experimental data well and does not lead to the formation of a large orbital moment on the Fe atom. Furthermore, exact diagonalization of the multiorbital Anderson impurity model with the full Coulomb interaction matrix and the spin-orbit coupling is performed in order to estimate the spin Hall angle. The obtained value γS≈0.025 suggests that there is no giant extrinsic spin Hall effect due to scattering on iron impurities in gold.

  1. Neutrino Scattering on Atomic Electrons in Searches for the Neutrino Magnetic Moment

    SciTech Connect

    Voloshin, M. B.

    2010-11-12

    The scattering of a neutrino on atomic electrons is considered in the situation where the energy transferred to the electrons is comparable to the characteristic atomic energies, as relevant to the current experimental search for the neutrino magnetic moment. The process is induced by the standard electroweak interaction as well as by the possible neutrino magnetic moment. Quantum-mechanical sum rules are derived for the inclusive cross section at a fixed energy deposited in the atomic system, and it is shown that the differential over the energy transfer cross section is given, modulo very small corrections, by the same expression as for free electrons, once all possible final states of the electronic system are taken into account. Thus, the atomic effects effectively cancel in the inclusive process.

  2. Mapping motion of antiferromagnetic interfacial uncompensated magnetic moment in exchange-biased bilayers

    PubMed Central

    Zhou, X.; Ma, L.; Shi, Z.; Fan, W. J.; Evans, R. F. L.; Zheng, Jian-Guo; Chantrell, R. W.; Mangin, S.; Zhang, H. W.; Zhou, S. M.

    2015-01-01

    In this work, disordered-IrMn3/insulating-Y3Fe5O12 exchange-biased bilayers are studied. The behavior of the net magnetic moment ΔmAFM in the antiferromagnet is directly probed by anomalous and planar Hall effects, and anisotropic magnetoresistance. The ΔmAFM is proved to come from the interfacial uncompensated magnetic moment. We demonstrate that the exchange bias and rotational hysteresis loss are induced by partial rotation and irreversible switching of the ΔmAFM. In the athermal training effect, the state of the ΔmAFM cannot be recovered after one cycle of hysteresis loop. This work highlights the fundamental role of the ΔmAFM in the exchange bias and facilitates the manipulation of antiferromagnetic spintronic devices. PMID:25777540

  3. Rotating effects on the Landau quantization for an atom with a magnetic quadrupole moment.

    PubMed

    Fonseca, I C; Bakke, K

    2016-01-01

    Based on the single particle approximation [Dmitriev et al., Phys. Rev. C 50, 2358 (1994) and C.-C. Chen, Phys. Rev. A 51, 2611 (1995)], the Landau quantization associated with an atom with a magnetic quadrupole moment is introduced, and then, rotating effects on this analogue of the Landau quantization is investigated. It is shown that rotating effects can modify the cyclotron frequency and breaks the degeneracy of the analogue of the Landau levels.

  4. The measurement of the anomalous magnetic moment of the muon at Fermilab

    SciTech Connect

    Logashenko, I.

    2015-06-17

    The anomalous magnetic moment of the muon is one of the most precisely measured quantities in experimental particle physics. Its latest measurement at Brookhaven National Laboratory deviates from the Standard Model expectation by approximately 3.5 standard deviations. The goal of the new experiment, E989, now under construction at Fermilab, is a fourfold improvement in precision. Furthermore, we discuss the details of the future measurement and its current status.

  5. Leading-order hadronic contributions to the electron and tau anomalous magnetic moments

    NASA Astrophysics Data System (ADS)

    Burger, Florian; Jansen, Karl; Petschlies, Marcus; Pientka, Grit

    2016-08-01

    The leading hadronic contributions to the anomalous magnetic moments of the electron and the τ -lepton are determined by a four-flavour lattice QCD computation with twisted mass fermions. The results presented are based on the quark-connected contribution to the hadronic vacuum polarisation function. The continuum limit is taken and systematic uncertainties are quantified. Full agreement with results obtained by phenomenological analyses is found.

  6. Hyperfine field of einsteinium in iron and nuclear magnetic moment of Es254

    NASA Astrophysics Data System (ADS)

    Severijns, N.; Belyaev, A. A.; Erzinkyan, A. L.; Eversheim, P.-D.; Filimonov, V. T.; Golovko, V. V.; Gurevich, G. M.; Herzog, P.; Kraev, I. S.; Lukhanin, A. A.; Noga, V. I.; Parfenova, V. P.; Phalet, T.; Rusakov, A. V.; Tandecki, M.; Toporov, Yu. G.; Tramm, C.; Traykov, E.; Gorp, S. Van; Vyachin, V. N.; Wauters, F.; Zákoucký, D.; Zotov, E.

    2009-06-01

    The angular distributions of γ rays and α particles from oriented Bk250, Es253,254, and Fm255 nuclei were investigated to extract hyperfine interaction information for these actinide impurities in an iron host lattice. The hyperfine field of einsteinium in iron was found to be |Bhf(EsFe̲|)=396(32) T. With this value the magnetic moment of Es254 was then determined as |μ|=4.35(41)μN.

  7. Effective Lagrangian approach to precision measurements: Anomalous magnetic moment of the muon

    SciTech Connect

    Arzt, C.; Einhorn, M.B. Randall Laboratory of Physics, University of Michigan, Ann Arbor, Michigan 48109-1120 ); Wudka, J. )

    1994-02-01

    We investigate the use of effective Lagrangians to describe the effects on high-precision observables of physics beyond the standard model. Using the anomalous magnetic moment of the muon as an example, we detail the use of effective vertices in loop calculations. We then provide estimates of the sensitivity of new experiments measuring the muon's [ital g][minus]2 to the scale of physics underlying the standard model.

  8. Z =50 core stability in 110Sn from magnetic-moment and lifetime measurements

    NASA Astrophysics Data System (ADS)

    Kumbartzki, G. J.; Benczer-Koller, N.; Speidel, K.-H.; Torres, D. A.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; Bevins, J. E.; Crawford, H. L.; Guevara, Z. E.; Gürdal, G.; Hurst, A. M.; Kirsch, L.; Laplace, T. A.; Lo, A.; Matthews, E. F.; Mayers, I.; Phair, L. W.; Ramirez, F.; Robinson, S. J. Q.; Sharon, Y. Y.; Wiens, A.

    2016-04-01

    Background: The structure of the semimagic 50Sn isotopes were previously studied via measurements of B (E 2 ;21+→01+ ) and g factors of 21+ states. The values of the B (E 2 ;21+ ) in the isotopes below midshell at N = 66 show an enhancement in collectivity, contrary to predictions from shell-model calculations. Purpose: This work presents the first measurement of the 2 1+ and 4 1+ states' magnetic moments in the unstable neutron-deficient 110Sn. The g factors provide complementary structure information to the interpretation of the observed B (E 2 ) values. Methods: The 110Sn nuclei have been produced in inverse kinematics in an α -particle transfer reaction from 12C to 106Cd projectiles at 390, 400, and 410 MeV. The g factors have been measured with the transient field technique. Lifetimes have been determined from line shapes using the Doppler-shift attenuation method. Results: The g factors of the 21+ and 41+ states in 110Sn are g (21+) = +0.29(11) and g (41+) = +0.05(14), respectively. In addition, the g (41+) = +0.27(6) in 106Cd has been measured for the first time. A line-shape analysis yielded τ (110Sn ; 21+) = 0.81(10) ps and a lifetime of τ (110Sn ; 31-) = 0.25(5) ps was calculated from the fully Doppler-shifted γ line. Conclusions: No evidence has been found in 110Sn that would require excitation of protons from the closed Z =50 core.

  9. Leading-order hadronic contributions to the lepton anomalous magnetic moments from the lattice

    NASA Astrophysics Data System (ADS)

    Burger, Florian; Feng, Xu; Jansen, Karl; Petschlies, Marcus; Pientka, Grit; Renner, Dru B.

    2016-04-01

    The hadronic leading-order (hlo) contribution to the lepton anomalous magnetic moments alhlo of the Standard Model leptons still accounts for the dominant source of the uncertainty of the Standard Model estimates. We present the results of an investigation of the hadronic leading order anomalous magnetic moments of the electron, muon and tau lepton from first principles in twisted mass lattice QCD. With lattice data for multiple pion masses in the range 230MeV ≲ mPS ≲ 490 MeV, multiple lattice volumes and three lattice spacings we perform the extrapolation to the continuum and to the physical pion mass and check for all systematic uncertainties in the lattice calculation. As a result we calculate alhlo for the three Standard Model leptons with controlled statistical and systematic error in agreement with phenomenological determinations using dispersion relations and experimental data. In addition, we also give a first estimate of the hadronic leading order anomalous magnetic moments from simulations directly at the physical value of the pion mass.

  10. LaCoO3 (LCO) - Dramatic changes in Magnetic Moment in fields to 500T

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Harmon, B. N.

    LCO has attracted great attention over the years (>2000 publications) because of its unusual magnetic properties; although in its ground state at low temperatures it is non-magnetic. A recent experiment[1] in pulsed fields to 500T showed a moment of ~1.3μB above 140T, and above ~270T the magnetization rises, reaching ~3.8μB by 500T. We have performed first principles DFT calculations for LCO in high fields. Our earlier calculations[2] explained the importance of a small rhombohedral distortion in the ground state that leads to a suppression of the 1.3μB moment for fields below ~140T. By allowing fairly large atomic displacements in high fields, moments of ~4μB are predicted. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Materials Science and Engineering Division under Contract No. DE-AC02-07CH11358.

  11. Leptophilic dark matter and the anomalous magnetic moment of the muon

    DOE PAGES

    Agrawal, Prateek; Chacko, Zackaria; Verhaaren, Christopher B.

    2014-08-26

    We consider renormalizable theories such that the scattering of dark matter off leptons arises at tree level, but scattering off nuclei only arises at loop. In this framework, the various dark matter candidates can be classified by their spins and by the forms of their interactions with leptons. In this study, we determine the corrections to the anomalous magnetic moment of the muon that arise from its interactions with dark matter. We then consider the implications of these results for a set of simplified models of leptophilic dark matter. When a dark matter candidate reduces the existing tension between themore » standard model prediction of the anomalous magnetic moment and the experimental measurement, the region of parameter space favored to completely remove the discrepancy is highlighted. Conversely, when agreement is worsened, we place limits on the parameters of the corresponding simplified model. These bounds and favored regions are compared against the experimental constraints on the simplified model from direct detection and from collider searches. Although these constraints are severe, we find there do exist limited regions of parameter space in these simple theories that can explain the observed anomaly in the muon magnetic moment while remaining consistent with all experimental bounds.« less

  12. Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2

    SciTech Connect

    Wu, Sanfeng; Ross, Jason; Liu, G. B.; Aivazian, Grant; Jones, Aaron; Fei, Zaiyao; Zhu, Wenguang; Xiao, Di; Yao, Wang; Cobden, David; Xu, Xiaodong

    2013-01-01

    Crystal symmetry governs the nature of electronic Bloch states. For example, in the presence of time-reversal symmetry, the orbital magnetic moment and Berry curvature of the Bloch states must vanish unless inversion symmetry is broken1. In certain two-dimensional electron systems such as bilayer graphene, the intrinsic inversion symmetry can be broken simply by applying a perpendicular electric field2,3. In principle, this offers the possibility of switching on/off and continuously tuning the magnetic moment and Berry curvature near the Dirac valleys by reversible electrical control4,5. Here we investigate this possibility using polarization-resolved photoluminescence of bilayer MoS2, which has the same symmetry as bilayer graphene but has a bandgap in the visible spectrum6,7 allowing direct optical probing5,8 12. We find that in bilayer MoS2 the circularly polarized photoluminescence can be continuously tuned from 15% to 15% as a function of gate voltage, whereas in structurally non-centrosymmetric monolayer MoS2 the photoluminescence polarization is gate independent. The observations are well explained as resulting from the continuous variation of orbital magnetic moments between positive and negative values through symmetry control.

  13. Leptophilic dark matter and the anomalous magnetic moment of the muon

    SciTech Connect

    Agrawal, Prateek; Chacko, Zackaria; Verhaaren, Christopher B.

    2014-08-26

    We consider renormalizable theories such that the scattering of dark matter off leptons arises at tree level, but scattering off nuclei only arises at loop. In this framework, the various dark matter candidates can be classified by their spins and by the forms of their interactions with leptons. In this study, we determine the corrections to the anomalous magnetic moment of the muon that arise from its interactions with dark matter. We then consider the implications of these results for a set of simplified models of leptophilic dark matter. When a dark matter candidate reduces the existing tension between the standard model prediction of the anomalous magnetic moment and the experimental measurement, the region of parameter space favored to completely remove the discrepancy is highlighted. Conversely, when agreement is worsened, we place limits on the parameters of the corresponding simplified model. These bounds and favored regions are compared against the experimental constraints on the simplified model from direct detection and from collider searches. Although these constraints are severe, we find there do exist limited regions of parameter space in these simple theories that can explain the observed anomaly in the muon magnetic moment while remaining consistent with all experimental bounds.

  14. The qqqqq components and hidden flavor contributions to the baryon magnetic moments

    SciTech Connect

    An, C. S.; Li, Q. B.; Riska, D. O.; Zou, B. S.

    2006-11-15

    The contributions from the qqqqq components to the magnetic moments of the octet as well as the {delta}{sup ++} and {omega}{sup -} decuplet baryons are calculated for the configurations that are expected to have the lowest energy if the hyperfine interaction depends on both spin and flavor. The contributions from the uu,dd, and the ss components are given separately. It is shown that addition of qqqqq admixtures to the ground state baryons can improve the overall description of the magnetic moments of the baryon octet and decuplet in the quark model without SU(3) flavor symmetry breaking, beyond that of the different constituent masses of the strange and light-flavor quarks. The explicit flavor (and spin) wave functions for all the possible configurations of the qqqqq components with light and strange qq pairs are given for the baryon octet and decuplet. Admixtures of {approx}10% of the qqqqq configuration where the flavor-spin symmetry is [4]{sub FS}[22]{sub F}[22]{sub S}, which is likely to have the lowest energy, in particular reduces the deviation from the empirical values of the magnetic moments {sigma}{sup -} and the {xi}{sup 0} compared with the static qqq quark model.

  15. Analyzing power in pion-proton bremsstrahlung, and the. Delta. sup ++ (1232) magnetic moment

    SciTech Connect

    Bosshard, A.; Amsler, C.; Doebeli, M.; Doser, M.; Schaad, M.; Riedlberger, J.; Truoel, P. ); Bistirlich, J.A.; Crowe, K.M.; Ljungfelt, S.; Meyer, C.A. ); van den Brandt, B.; Konter, J.A.; Mango, S.; Renker, D. ); Loude, J.F.; Perroud, J.P. ); Haddock, R.P. ); Sober, D.I. )

    1991-10-01

    We report on a first measurement of the polarized-target asymmetry of the pion-proton bremsstrahlung cross section ({pi}{sup +}{ital p}{r arrow}{pi}{sup {minus}}{ital p}{gamma}). As in previous cross section measurements the pion energy (298 MeV) and the detector geometry for this experiment was chosen to optimize the sensitivity to the radiation from the magnetic dipole moment of the {Delta}{sup ++}(1232) resonance {mu}{sub {Delta}}. Comparison to a recent isobar model for pion-nucleon bremsstrahlung yields {mu}{sub {Delta}}=(1.62{plus minus}0.18){mu}{sub {ital p}}, where {mu}{sub {ital p}} is the proton magnetic moment. Since the asymmetry depends less than the cross section on the choice of the other input parameters for the model, their uncertainties affect this analysis by less than the experimental error. However the theory fails to represent both the cross section and the asymmetry data at the highest photon energies. Hence further improvements in the calculations are needed before the model dependence of the magnetic moment analysis can be fully assessed. The present result agrees with bag-model corrections to the SU(6) prediction {mu}{sub {Delta}}=2{mu}{sub {ital p}}. As a by-product, the analyzing power for elastic {pi}{sup +}{ital p} scattering at 415 MeV/{ital c} was also measured. This second result is in good agreement with phase shift calculations.

  16. Nuclear Magnetic Moment of {sup 210}Fr: A Combined Theoretical and Experimental Approach

    SciTech Connect

    Gomez, E.; Aubin, S.; Sprouse, G. D.; Orozco, L. A.; Iskrenova-Tchoukova, E.; Safronova, M. S.

    2008-05-02

    We measure the hyperfine splitting of the 9S{sub 1/2} level of {sup 210}Fr, and find a magnetic dipole hyperfine constant A=622.25(36) MHz. The theoretical value, obtained using the relativistic all-order method from the electronic wave function at the nucleus, allows us to extract a nuclear magnetic moment of 4.38(5){mu}{sub N} for this isotope, which represents a factor of 2 improvement in precision over previous measurements. The same method can be applied to other rare isotopes and elements.

  17. Regular and chaotic dynamics of a chain of magnetic dipoles with moments of inertia

    SciTech Connect

    Shutyi, A. M.

    2009-05-15

    The nonlinear dynamic modes of a chain of coupled spherical bodies having dipole magnetic moments that are excited by a homogeneous ac magnetic field are studied using numerical analysis. Bifurcation diagrams are constructed and used to find conditions for the presence of several types of regular, chaotic, and quasi-periodic oscillations. The effect of the coupling of dipoles on the excited dynamics of the system is revealed. The specific features of the Poincare time sections are considered for the cases of synchronous chaos with antiphase synchronization and asynchronous chaos. The spectrum of Lyapunov exponents is calculated for the dynamic modes of an individual dipole.

  18. Probing the Pu4 + magnetic moment in PuF4 with 19F NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Capan, Cigdem; Dempsey, Richard J.; Sinkov, Sergey; McNamara, Bruce K.; Cho, Herman

    2016-06-01

    The magnetic fields produced by Pu4 + centers have been measured by 19F NMR spectroscopy to elucidate the Pu-F electronic interactions in polycrystalline PuF4. Spectra acquired at applied fields of 2.35 and 7.05 T reveal a linear scaling of the 19F line shape. A model is presented that treats the line broadening and shifts as due to dipolar fields produced by Pu valence electrons in localized noninteracting orbitals. Alternative explanations for the observed line shape involving covalent Pu-F bonding, superexchange interactions, and electronic configurations with enhanced magnetic moments are considered.

  19. Lifting particle coordinate changes of magnetic moment type to Vlasov-Maxwell Hamiltonian dynamics

    SciTech Connect

    Morrison, P. J.; Vittot, M.; Guillebon, L. de

    2013-03-15

    Techniques for coordinate changes that depend on both dependent and independent variables are developed and applied to the Maxwell-Vlasov Hamiltonian theory. Particle coordinate changes with a new velocity variable dependent on the magnetic field, with spatial coordinates unchanged, are lifted to the field theoretic level, by transforming the noncanonical Poisson bracket and Hamiltonian structure of the Vlasov-Maxwell dynamics. Several examples are given including magnetic coordinates, where the velocity is decomposed into components parallel and perpendicular to the local magnetic field, and the case of spherical velocity coordinates. An example of the lifting procedure is performed to obtain a simplified version of gyrokinetics, where the magnetic moment is used as a coordinate and the dynamics is reduced by elimination of the electric field energy in the Hamiltonian.

  20. THE INTERSTELLAR MAGNETIC FIELD CLOSE TO THE SUN. II

    SciTech Connect

    Frisch, P. C.; Andersson, B-G; Berdyugin, A.; Piirola, V.; DeMajistre, R.; Funsten, H. O.; Magalhaes, A. M.; Seriacopi, D. B.; McComas, D. J.; Schwadron, N. A.; Slavin, J. D.; Wiktorowicz, S. J.

    2012-12-01

    The magnetic field in the local interstellar medium (ISM) provides a key indicator of the galactic environment of the Sun and influences the shape of the heliosphere. We have studied the interstellar magnetic field (ISMF) in the solar vicinity using polarized starlight for stars within 40 pc of the Sun and 90 Degree-Sign of the heliosphere nose. In Frisch et al. (Paper I), we developed a method for determining the local ISMF direction by finding the best match to a group of interstellar polarization position angles obtained toward nearby stars, based on the assumption that the polarization is parallel to the ISMF. In this paper, we extend the analysis by utilizing weighted fits to the position angles and by including new observations acquired for this study. We find that the local ISMF is pointed toward the galactic coordinates l, b =47 Degree-Sign {+-} 20 Degree-Sign , 25 Degree-Sign {+-} 20 Degree-Sign . This direction is close to the direction of the ISMF that shapes the heliosphere, l, b =33 Degree-Sign {+-} 4 Degree-Sign , 55 Degree-Sign {+-} 4 Degree-Sign , as traced by the center of the 'Ribbon' of energetic neutral atoms discovered by the Interstellar Boundary Explorer (IBEX) mission. Both the magnetic field direction and the kinematics of the local ISM are consistent with a scenario where the local ISM is a fragment of the Loop I superbubble. A nearby ordered component of the local ISMF has been identified in the region l Almost-Equal-To 0 Degree-Sign {yields} 80 Degree-Sign and b Almost-Equal-To 0 Degree-Sign {yields} 30 Degree-Sign , where PlanetPol data show a distance-dependent increase of polarization strength. The ordered component extends to within 8 pc of the Sun and implies a weak curvature in the nearby ISMF of {approx}0.{sup 0}25 pc{sup -1}. This conclusion is conditioned on the small sample of stars available for defining this rotation. Variations from the ordered component suggest a turbulent component of {approx}23 Degree-Sign . The ordered

  1. Ratio of Isoscalar to Isovector Core Polarization Contributions to Magnetic Moments

    NASA Astrophysics Data System (ADS)

    Robinson, Shadow; Zamick, Larry; Sharon, Yitzhak

    2010-11-01

    We found that large scale calculations of isoscalar magnetic moments of odd-odd N=Z nuclei yielded results remarkably similar to those of simple single j calculations. To understand why we use a delta interaction times (1+xPs) where Ps is the spin exchange operator, to calculate the ratio IS/IV of the core polarization contributions to the magnetic moments. The spin exchange contributes a factor (1-2x) to this ratio. A popular choice is x=1/3 for which (1-2x) is also 1/3. Another contribution comes from the fact that the coupling of j=l+1/2 to j'=l-1/2 via the magnetic moment operator is proportional to (gs-gl). The IS values are gl=0.5 gs=0.88; the IV values are 0.5 and 4.71. This yields a (gs-gl) ratio of 0.09 which together with the 1/3 from spin exchange tells us that the isoscalar core polarization is a mere 3% of isovector. If we further divide by single j values to get effective charge corrections then the ration IS/IV ends up being 0.06 (or 6%). We thus gain understanding of the resuts in ref [1] of the near equality of large scale and single j results for IS moments.[4pt] [1] S.Yeager, S.J.Q. Robinson, L.Zamick and Y.Y.Sharon, EPL 88, 52001 (2009)

  2. Collinear laser spectroscopy of atomic cadmium. Extraction of nuclear magnetic dipole and electric quadrupole moments

    NASA Astrophysics Data System (ADS)

    Frömmgen, Nadja; Balabanski, Dimiter L.; Bissell, Mark L.; Bieroń, Jacek; Blaum, Klaus; Cheal, Bradley; Flanagan, Kieran; Fritzsche, Stephan; Geppert, Christopher; Hammen, Michael; Kowalska, Magdalena; Kreim, Kim; Krieger, Andreas; Neugart, Rainer; Neyens, Gerda; Rajabali, Mustafa M.; Nörtershäuser, Wilfried; Papuga, Jasna; Yordanov, Deyan T.

    2015-06-01

    Hyperfine structure A and B factors of the atomic 5 s5 p 3P2 → 5 s6 s 3S1 transition are determined from collinear laser spectroscopy data of 107-123Cd and 111 m-123 m Cd. Nuclear magnetic moments and electric quadrupole moments are extracted using reference dipole moments and calculated electric field gradients, respectively. The hyperfine structure anomaly for isotopes with s 1/2 and d 5/2 nuclear ground states and isomeric h 11/2 states is evaluated and a linear relationship is observed for all nuclear states except s 1/2. This corresponds to the Moskowitz-Lombardi rule that was established in the mercury region of the nuclear chart but in the case of cadmium the slope is distinctively smaller than for mercury. In total four atomic and ionic levels were analyzed and all of them exhibit a similar behaviour. The electric field gradient for the atomic 5 s5 p 3P2 level is derived from multi-configuration Dirac-Hartree-Fock calculations in order to evaluate the spectroscopic nuclear quadrupole moments. The results are consistent with those obtained in an ionic transition and based on a similar calculation.

  3. Evidence of half-metallic interface magnetism via local moment formation in Co based Heusler alloys

    SciTech Connect

    Telling, N. D.; Keatley, P.S.; van der Laan, G.; Hicken, R.J.; Arenholz, E.; Sakuraba, Y.; Oogane, M.; Ando, Y.; Miyazaki, T.

    2008-08-18

    In this work we use a combination of x-ray magnetic circular and linear dichroism (XMCD and XMLD) techniques to examine the formation of local moments in Heusler alloys of the composition Co{sub 2}MnX (where X=Si or Al). The existence of local moments in a half-metallic system is reliant upon the band gap in the minority-spin states. By utilizing the element-specific nature of x-ray techniques we are able to explore the origin of the minority-spin band gap in the partial density of states (PDOS), via the degree of localization of moments on Co and Mn atoms. We observe a crucial difference in the localization of the Co moment when comparing Co{sub 2}MnSi (CMS) and Co{sub 2}MnAl (CMA) films that is consistent with the predicted larger minority-spin gap in the Co PDOS for CMS. These results provide important evidence for the dominant role of the Co minority-spin states in realizing half-metallic ferromagnetism (HMF) in these Heusler alloys. They also demonstrate a direct method for measuring the degree of interfacial HMF in the raw materials without the need for fabricating spin-transport devices.

  4. Insignificance of the anomalous magnetic moment of charged fermions for the equation of state of a magnetized and dense medium

    NASA Astrophysics Data System (ADS)

    Ferrer, E. J.; de la Incera, V.; Paret, D. Manreza; Martínez, A. Pérez; Sanchez, A.

    2015-04-01

    We investigate the effects of the anomalous magnetic moment (AMM) in the equation of state (EOS) of a system of charged fermions at finite density in the presence of a magnetic field. In the region of strong magnetic fields (e B >m2 ), the AMM is found from the one-loop fermion self-energy. In contrast to the weak-field AMM found by Schwinger, in the strong magnetic field region the AMM depends on the Landau level and decreases with it. The effects of the AMM in the EOS of a dense medium are investigated at strong and weak fields using the appropriate AMM expression for each case. In contrast with what has been reported in other works, we find that the AMM of charged fermions makes no significant contribution to the EOS at any field value.

  5. Switchable magnetic moment in cobalt-doped graphene bilayer on Cu(111): An ab initio study

    NASA Astrophysics Data System (ADS)

    Souza, Everson S.; Scopel, Wanderlã L.; Miwa, R. H.

    2016-06-01

    In this work, we have performed an ab initio theoretical investigation of substitutional cobalt atoms in the graphene bilayer supported on the Cu(111) surface (Co/GBL/Cu). Initially, we examined the separated systems, namely, graphene bilayer adsorbed on Cu(111) (GBL/Cu) and a free standing Co-doped GBL (Co/GBL). In the former system, the GBL becomes n -type doped, where we map the net electronic charge density distribution along the GBL-Cu(111) interface. The substitutional Co atom in Co/GBL lies between the graphene layers, and present a net magnetic moment mostly due to the unpaired Co-3 dz2 electrons. In Co/GBL/Cu, we found that the Cu(111) substrate rules (i) the energetic stability, and (ii) the magnetic properties of substitutional Co atoms in the graphene bilayer. In (i), the substitutional Co atom becomes energetically more stable lying on the GBL surface, and in (ii), the magnetic moment of Co/GBL has been quenched due to the Cu(111) → Co/GBL electronic charge transfer. We verify that such a charge transfer can be tuned upon the application of an external electric field, and thus mediated by a suitable change on the electronic occupation of the Co-dz2 orbitals, we found a way to switch-on and -off the magnetization of the Co-doped GBL adsorbed on the Cu(111) surface.

  6. Remote sensing of the magnetic moment of uranus: predictions for voyager.

    PubMed

    Hill, T W; Dessler, A J

    1985-03-22

    Power is supplied to a planet's magnetosphere from the kinetic energy of planetary spin and the energy flux of the impinging solar wind. A fraction of this power is available to drive numerous observable phenomena, such as polar auroras and planetary radio emissions. In this report our present understanding of these power transfer mechanisms is applied to Uranus to make specific predictions of the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and ultraviolet spectrometer (UVS) instruments aboard the Voyager spacecraft before its encounter with Uranus at the end of January 1986. The power available for these two phenomena is (among other factors) a function of the magnetic moment of Uranus. The date of earliest detectability also depends on whether the predominant power source for the magnetosphere is planetary spin or solar wind. The magnetic moment of Uranus is derived for each power source as a function of the date of first detection of radio emissions by the PRA instrument or auroral emissions by the UVS instrument. If we accept the interpretation of ultraviolet observations now available from the Earth-orbiting International Ultraviolet Explorer satellite, Uranus has a surface magnetic field of at least 0.6 gauss, and more probably several gauss, making it the largest or second-largest planetary magnetic field in the solar system. PMID:17777779

  7. Remote sensing of the magnetic moment of uranus: predictions for voyager.

    PubMed

    Hill, T W; Dessler, A J

    1985-03-22

    Power is supplied to a planet's magnetosphere from the kinetic energy of planetary spin and the energy flux of the impinging solar wind. A fraction of this power is available to drive numerous observable phenomena, such as polar auroras and planetary radio emissions. In this report our present understanding of these power transfer mechanisms is applied to Uranus to make specific predictions of the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and ultraviolet spectrometer (UVS) instruments aboard the Voyager spacecraft before its encounter with Uranus at the end of January 1986. The power available for these two phenomena is (among other factors) a function of the magnetic moment of Uranus. The date of earliest detectability also depends on whether the predominant power source for the magnetosphere is planetary spin or solar wind. The magnetic moment of Uranus is derived for each power source as a function of the date of first detection of radio emissions by the PRA instrument or auroral emissions by the UVS instrument. If we accept the interpretation of ultraviolet observations now available from the Earth-orbiting International Ultraviolet Explorer satellite, Uranus has a surface magnetic field of at least 0.6 gauss, and more probably several gauss, making it the largest or second-largest planetary magnetic field in the solar system.

  8. Nd-doped ZnO monolayer: High Curie temperature and large magnetic moment

    NASA Astrophysics Data System (ADS)

    Tan, Changlong; Sun, Dan; Zhou, Long; Tian, Xiaohua; Huang, Yuewu

    2016-10-01

    We performed first-principles calculations within density-functional theory to study the structural, electronic, and magnetic properties of Nd-doped ZnO monolayer. The calculated results reveal that Nd-doped ZnO monolayer exhibits stable room temperature ferromagnetism with a large saturation magnetic moment of 3.99 μB per unit in ZnO monolayer. The magnetic property is contributed to the localized f sates of Nd atoms. When two Zn atoms are substituted by two Nd dopants, they tend to form ferromagnetic (FM) coupling and the estimated Curie temperature is higher than room temperature. More interesting, the impurity bands appear within the band gap of ZnO monolayer due to the introduction of Nd dopant. Our results may provide a reference for modifying the material property of ZnO monolayer and are promising as nanoscale building block in spintronic devices.

  9. Itinerancy-enhanced quantum fluctuation of magnetic moments in iron-based superconductors.

    PubMed

    Tam, Yu-Ting; Yao, Dao-Xin; Ku, Wei

    2015-09-11

    We investigate the influence of itinerant carriers on the dynamics and fluctuation of local moments in Fe-based superconductors, via linear spin-wave analysis of a spin-fermion model containing both itinerant and local degrees of freedom. Surprisingly, against the common lore, instead of enhancing the (π,0) order, itinerant carriers with well-nested Fermi surfaces are found to induce a significant amount of spatial and temporal quantum fluctuation that leads to the observed small ordered moment. Interestingly, the underlying mechanism is shown to be an intrapocket nesting-associated long-range coupling rather than the previously believed ferromagnetic double-exchange effect. This challenges the validity of ferromagnetically compensated first-neighbor coupling reported from short-range fitting to the experimental dispersion, which turns out to result instead from the ferro-orbital order that is also found instrumental in stabilizing the magnetic order. PMID:26406850

  10. Realizing high magnetic moments in fcc Fe nanoparticles through atomic structure stretch.

    PubMed

    Baker, S H; Roy, M; Thornton, S C; Binns, C

    2012-05-01

    We describe the realization of a high moment state in fcc Fe nanoparticles through a controlled change in their atomic structure. Embedding Fe nanoparticles in a Cu(1-x)Au(x) matrix causes their atomic structure to switch from bcc to fcc. Extended x-ray absorption fine structure (EXAFS) measurements show that the structure in both the matrix and the Fe nanoparticles expands as the amount of Au in the matrix is increased, with the data indicating a tetragonal stretch in the Fe nanoparticles. The samples were prepared directly from the gas phase by co-deposition, using a gas aggregation source and MBE-type sources respectively for the nanoparticle and matrix materials. The structure change in the Fe nanoparticles is accompanied by a sharp increase in atomic magnetic moment, ultimately to values of ~2.5 ± 0.3 μ(B)/atom .

  11. Itinerancy enhanced quantum fluctuation of magnetic moments in iron-based superconductors

    SciTech Connect

    Tam, Yu -T.; Ku, W.; Yao, D. -X.

    2015-09-10

    We investigate the influence of itinerant carriers on dynamics and fluctuation of local moments in Fe-based superconductors, via linear spin-wave analysis of a spin-fermion model containing both itinerant and local degrees of freedom. Surprisingly against the common lore, instead of enhancing the (π,0) order, itinerant carriers with well nested Fermi surfaces is found to induce significant amount of spatial and temporal quantum fluctuation that leads to the observed small ordered moment. Interestingly, the underlying mechanism is shown to be intra-pocket nesting-associated long-range coupling, rather than the previously believed ferromagnetic double-exchange effect. This challenges the validity of ferromagnetically compensated first-neighbor coupling reported from short-range fitting to the experimental dispersion, which turns out to result instead from the ferro-orbital order that is also found instrumental in stabilizing the magnetic order.

  12. Itinerancy enhanced quantum fluctuation of magnetic moments in iron-based superconductors

    DOE PAGES

    Tam, Yu -T.; Ku, W.; Yao, D. -X.

    2015-09-10

    We investigate the influence of itinerant carriers on dynamics and fluctuation of local moments in Fe-based superconductors, via linear spin-wave analysis of a spin-fermion model containing both itinerant and local degrees of freedom. Surprisingly against the common lore, instead of enhancing the (π,0) order, itinerant carriers with well nested Fermi surfaces is found to induce significant amount of spatial and temporal quantum fluctuation that leads to the observed small ordered moment. Interestingly, the underlying mechanism is shown to be intra-pocket nesting-associated long-range coupling, rather than the previously believed ferromagnetic double-exchange effect. This challenges the validity of ferromagnetically compensated first-neighbor couplingmore » reported from short-range fitting to the experimental dispersion, which turns out to result instead from the ferro-orbital order that is also found instrumental in stabilizing the magnetic order.« less

  13. Hamiltonian description of closed configurations of the vacuum magnetic field

    SciTech Connect

    Skovoroda, A. A.

    2015-05-15

    Methods of obtaining and using the Hamiltonians of closed vacuum magnetic configurations of fusion research systems are reviewed. Various approaches to calculate the flux functions determining the Hamiltonian are discussed. It is shown that the Hamiltonian description allows one not only to reproduce all traditional results, but also to study the behavior of magnetic field lines by using the theory of dynamic systems. The potentialities of the Hamiltonian formalism and its close relation to traditional methods are demonstrated using a large number of classical examples adopted from the fundamental works by A.I. Morozov, L.S. Solov’ev, and V.D. Shafranov.

  14. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    DOE PAGES

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  15. NMR absolute shielding scale and nuclear magnetic dipole moment of (207)Pb.

    PubMed

    Adrjan, Bożena; Makulski, Włodzimierz; Jackowski, Karol; Demissie, Taye B; Ruud, Kenneth; Antušek, Andrej; Jaszuński, Michał

    2016-06-28

    An absolute shielding scale is proposed for (207)Pb nuclear magnetic resonance (NMR) spectroscopy. It is based on ab initio calculations performed on an isolated tetramethyllead Pb(CH3)4 molecule and the assignment of the experimental resonance frequency from the gas-phase NMR spectra of Pb(CH3)4, extrapolated to zero density of the buffer gas to obtain the result for an isolated molecule. The computed (207)Pb shielding constant is 10 790 ppm for the isolated molecule, leading to a shielding of 10799.7 ppm for liquid Pb(CH3)4 which is the accepted reference standard for (207)Pb NMR spectra. The new experimental and theoretical data are used to determine μ((207)Pb), the nuclear magnetic dipole moment of (207)Pb, by applying the standard relationship between NMR frequencies, shielding constants and nuclear moments of two nuclei in the same external magnetic field. Using the gas-phase (207)Pb and (reference) proton results and the theoretical value of the Pb shielding in Pb(CH3)4, we find μ((207)Pb) = 0.59064 μN. The analysis of new experimental and theoretical data obtained for the Pb(2+) ion in water solutions provides similar values of μ((207)Pb), in the range of 0.59000-0.59131 μN. PMID:27265668

  16. Effect of core polarization on magnetic dipole moments in deformed odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Bonneau, L.; Minkov, N.; Duc, Dao Duy; Quentin, P.; Bartel, J.

    2015-05-01

    Magnetic properties of deformed odd-mass nuclei are studied within a nonrelativistic mean-field-plus-pairing approach, namely the Skyrme-Hartree-Fock-BCS approach with self-consistent blocking. For an odd number of nucleons these approaches lead to the breaking of the time-reversal invariance. The deviation from the Schmidt values of the isoscalar magnetic dipole moment is known to result from a subtle balance between core-polarization effects and meson-exchange current effects. However, the former are usually calculated in the random phase approximation without time-reversal symmetry breaking at the mean-field level. In this work we show that if one takes into account this symmetry breaking already in the mean-field solution, the correction from core polarization yields a significant contribution to the empirical quenching of the spin gyromagnetic ratios as compared to the free values in deformed odd-mass nuclei. Moreover, we calculate magnetic dipole moments in the Bohr and Mottelson unified-model description with self-consistent blocked mean-field intrinsic states. The obtained results in the A ˜100 and A ˜180 mass regions as well as for three actinide nuclei compare favorably with experimental data.

  17. (83)Kr nuclear magnetic moment in terms of that of (3)He.

    PubMed

    Makulski, Włodzimierz

    2014-08-01

    High resolution NMR spectroscopy was applied to precisely determine the (83)Kr nuclear magnetic dipole moment on the basis of new results available for nuclear magnetic shielding in krypton and helium-3 atoms. Small amounts of (3)He as the solutes and (83)Kr as the buffer gas were observed in (3)He and (83)Kr NMR spectra at the constant external field, B0 = 11.7578 T. In each case, the resonance frequencies (ν(He) and ν(Kr)) were linearly dependent on the density of gaseous solvent. The extrapolation of experimental points to the zero density of gaseous krypton allowed for the evaluation of both resonance frequencies free from intermolecular interactions. By combining these measurements with the recommended (83)Kr chemical shielding value, the nuclear magnetic moment could be determined with much better precision than ever before, μ((83)Kr) = -0.9707297(32)μN, with the improvement due to the greater accuracy of the spectral data.

  18. (83)Kr nuclear magnetic moment in terms of that of (3)He.

    PubMed

    Makulski, Włodzimierz

    2014-08-01

    High resolution NMR spectroscopy was applied to precisely determine the (83)Kr nuclear magnetic dipole moment on the basis of new results available for nuclear magnetic shielding in krypton and helium-3 atoms. Small amounts of (3)He as the solutes and (83)Kr as the buffer gas were observed in (3)He and (83)Kr NMR spectra at the constant external field, B0 = 11.7578 T. In each case, the resonance frequencies (ν(He) and ν(Kr)) were linearly dependent on the density of gaseous solvent. The extrapolation of experimental points to the zero density of gaseous krypton allowed for the evaluation of both resonance frequencies free from intermolecular interactions. By combining these measurements with the recommended (83)Kr chemical shielding value, the nuclear magnetic moment could be determined with much better precision than ever before, μ((83)Kr) = -0.9707297(32)μN, with the improvement due to the greater accuracy of the spectral data. PMID:24842240

  19. Multiferroicity and spiral magnetism in FeVO{sub 4} with quenched Fe orbital moments

    SciTech Connect

    Daoud-Aladine, A.; Chapon, L. C.; Kundys, B.; Martin, C.; Simon, C.; Radaelli, P. G.; Brown, P. J.

    2009-12-01

    FeVO{sub 4} has been studied by heat capacity, magnetic susceptibility, electric polarization and single-crystal neutron-diffraction experiments. The triclinic crystal structure is made of S-shaped clusters of six Fe{sup 3+} ions, linked by VO{sub 4}{sup 3-} groups. Two long-range magnetic ordering transitions occur at T{sub N1}=22 K and T{sub N2}=15 K. Both magnetic structures are incommensurate and below T{sub N2}, FeVO{sub 4} becomes weakly ferroelectric coincidentally with the loss of the collinearity of the magnetic structure in a very similar fashion than in the classical TbMnO{sub 3} multiferroic material. However we argue that the symmetry considerations and the mechanisms invoked to explain these properties in TbMnO{sub 3} do not straightforwardly apply to FeVO{sub 4}. First, the magnetic structures, even the collinear structure, are all acentric so that ferroelectricity in FeVO{sub 4} is not correlated with the fact magnetic ordering is breaking inversion symmetry. Regarding the mechanism, FeVO{sub 4} has quenched orbital moments that questions the exact role of the spin-orbit interactions.

  20. Hyperfine field of einsteinium in iron and nuclear magnetic moment of {sup 254}Es

    SciTech Connect

    Severijns, N.; Kraev, I. S.; Phalet, T.; Tandecki, M.; Traykov, E.; Gorp, S. Van; Wauters, F.; Belyaev, A. A.; Lukhanin, A. A.; Noga, V. I.; Erzinkyan, A. L.; Parfenova, V. P.; Eversheim, P.-D.; Herzog, P.; Tramm, C.; Filimonov, V. T.; Toporov, Yu. G.; Zotov, E.; Golovko, V. V.; Gurevich, G. M.

    2009-06-15

    The angular distributions of {gamma} rays and {alpha} particles from oriented {sup 250}Bk, {sup 253,254}Es, and {sup 255}Fm nuclei were investigated to extract hyperfine interaction information for these actinide impurities in an iron host lattice. The hyperfine field of einsteinium in iron was found to be |B{sub hf}(EsFe{sub lowbar|})=396(32) T. With this value the magnetic moment of {sup 254}Es was then determined as |{mu}|=4.35(41) {mu}{sub N}.

  1. Calculation of the Hadronic Vacuum Polarization Disconnected Contribution to the Muon Anomalous Magnetic Moment.

    PubMed

    Blum, T; Boyle, P A; Izubuchi, T; Jin, L; Jüttner, A; Lehner, C; Maltman, K; Marinkovic, M; Portelli, A; Spraggs, M

    2016-06-10

    We report the first lattice QCD calculation of the hadronic vacuum polarization (HVP) disconnected contribution to the muon anomalous magnetic moment at physical pion mass. The calculation uses a refined noise-reduction technique that enables the control of statistical uncertainties at the desired level with modest computational effort. Measurements were performed on the 48^{3}×96 physical-pion-mass lattice generated by the RBC and UKQCD Collaborations. We find the leading-order hadronic vacuum polarization a_{μ}^{HVP(LO)disc}=-9.6(3.3)(2.3)×10^{-10}, where the first error is statistical and the second systematic. PMID:27341226

  2. Magnetic moment of the majorana neutrino in the left-right symmetric model

    SciTech Connect

    Boyarkin, O. M. Boyarkina, G. G.

    2013-04-15

    Corrections to the neutrino magnetic dipole moment from the singly charged Higgs bosons h{sup ({+-})} and {delta}-tilde{sup (}{+-}) were calculated within the left-right symmetric model involving Majorana neutrinos. It is shown that, if the h{sup ({+-})} and {delta}-tilde{sup (}{+-}) bosons lie at the electroweak scale, the contributions from Higgs sector are commensurate with the contribution of charged gauge bosons or may even exceed it. The behavior of the neutrino flux inmatter and in amagnetic field was studied. It was found that resonance transitions between light and heavy neutrinos are forbidden.

  3. Hadronic light-by-light scattering contribution to the muon anomalous magnetic moment from lattice QCD

    SciTech Connect

    Blum, Thomas; Chowdhury, Saumitra; Hayakawa, Masashi; Izubuchi, Taku

    2015-01-07

    The form factor that yields the light-by-light scattering contribution to the muon anomalous magnetic moment is computed in lattice QCD+QED and QED. A non-perturbative treatment of QED is used and is checked against perturbation theory. The hadronic contribution is calculated for unphysical quark and muon masses, and only the diagram with a single quark loop is computed. Statistically significant signals are obtained. Initial results appear promising, and the prospect for a complete calculation with physical masses and controlled errors is discussed.

  4. Calculation of the Hadronic Vacuum Polarization Disconnected Contribution to the Muon Anomalous Magnetic Moment.

    PubMed

    Blum, T; Boyle, P A; Izubuchi, T; Jin, L; Jüttner, A; Lehner, C; Maltman, K; Marinkovic, M; Portelli, A; Spraggs, M

    2016-06-10

    We report the first lattice QCD calculation of the hadronic vacuum polarization (HVP) disconnected contribution to the muon anomalous magnetic moment at physical pion mass. The calculation uses a refined noise-reduction technique that enables the control of statistical uncertainties at the desired level with modest computational effort. Measurements were performed on the 48^{3}×96 physical-pion-mass lattice generated by the RBC and UKQCD Collaborations. We find the leading-order hadronic vacuum polarization a_{μ}^{HVP(LO)disc}=-9.6(3.3)(2.3)×10^{-10}, where the first error is statistical and the second systematic.

  5. Lattice calculation of hadronic light-by-light contribution to the muon anomalous magnetic moment

    DOE PAGES

    Blum, Thomas; Christ, Norman; Hayakawa, Masashi; Izubuchi, Taku; Jin, Luchang; Lehner, Christoph

    2016-01-12

    The quark-connected part of the hadronic light-by-light scattering contribution to the muon’s anomalous magnetic moment is computed using lattice QCD with chiral fermions. Here we report several significant algorithmic improvements and demonstrate their effectiveness through specific calculations which show a reduction in statistical errors by more than an order of magnitude. The most realistic of these calculations is performed with a near-physical 171 MeV pion mass on a (4.6 fm)3 spatial volume using the 323×64 Iwasaki+DSDR gauge ensemble of the RBC/UKQCD Collaboration.

  6. Leading SU(3)-breaking corrections to the baryon magnetic moments in chiral perturbation theory.

    PubMed

    Geng, L S; Camalich, J Martin; Alvarez-Ruso, L; Vacas, M J Vicente

    2008-11-28

    We calculate the baryon magnetic moments using covariant chiral perturbation theory (chiPT) within the extended-on-mass-shell renormalization scheme. By fitting the two available low-energy constants, we improve the Coleman-Glashow description of the data when we include the leading SU(3)-breaking effects coming from the lowest-order loops. This success is in dramatic contrast with previous attempts at the same order using heavy-baryon chiPT and covariant infrared chiPT. We also analyze the source of this improvement with particular attention to the comparison between the covariant results.

  7. A 17 keV neutrino and large magnetic moment solution of the solar neutrino puzzle

    NASA Astrophysics Data System (ADS)

    Akhmedov, E. Kh.; Senjanovic, G.; Tao, Zhijian; Berezhiani, Z. G.

    1992-08-01

    Zee-type models with Majorons naturally incorporate the 17 keV neutrino but in their minimal version fail to simultaneously solve the solar neutrino puzzle. If there is a sterile neutrino state, a particularly simple solution is found to the solar neutrino problem, which besides nu(sub 17) predicts a light Zeldovich-Konopinski-Mahmoud neutrino nu(sub light) = nu(sub e) + nu(sub mu)(sup c) with a magnetic moment being easily as large as 10(exp -11)(mu)(sub B) through the Barr-Freire-Zee mechanism.

  8. 17 keV neutrino and large magnetic moment solution of the solar neutrino puzzle

    NASA Astrophysics Data System (ADS)

    Akhmedov, Eugeni Kh.; Berezhiani, Zurab G.; Senjanović, Goran; Tao, Zhijian

    1993-01-01

    Zee-type models with majorons naturally incorporate the 17 keV neutrino but in their minimal version fail to simultaneously solve the solar neutrino puzzle. If there is a sterile neutrino state, we find a particularly simple solution to the solar neutrino problem, which besides ν17 predicts a light Zeldovich-Konopinski-Mahmoud neutrino νlight = νe + νcμ with a magnetic moment being easily as large as 10 -11μB through the Barr-Freire-Zee mechanism.

  9. Ionization of helium atoms under the effect of the antineutrino magnetic moment

    SciTech Connect

    Martemyanov, V. P. Tsinoev, V. G.

    2011-12-15

    Differential cross sections for inelastic antineutrino interaction with a helium atom are calculated. It is shown that, in the energy-transfer range extending up to 1 keV, the cross sections in question are considerably enhanced in the electromagnetic-interaction channel in relation to the cross sections for elastic scattering on a free electron. Absolute cross-section values are of interest in searches for the antineutrino magnetic moment, provided that its value in Bohr magneton units falls within the range (10{sup -13}-10{sup -12}){sub Micro-Sign B}.

  10. Stuart Pittel and the f7/2Shell Revisited: Magnetic Moments in the Ca Isotopes

    NASA Astrophysics Data System (ADS)

    Benczer-Koller, N.; Kumbartzki, G.; Mertzimekis, T. J.; Sharon, Y. Y.; Speidel, K.-H.; Taylor, M. J.; Zamick, L.

    2004-09-01

    The study of the structure of the Ca isotopes occupied Stuart Pittel for many years at the beginning of his career. In spite of many experiments and theoretical investigations over the last thirty years, the Ca isotopes still provide considerable surprises. Recently, magnetic moments of 21+ states in 42,44,46Ca have been measured and will be discussed in terms of a model encompassing a two-component wave function representing particle-hole excitations of the 40Ca core and single particle configurations.

  11. Using baryon octet magnetic moments and masses to fix the pion cloud contribution

    DOE PAGES

    Franz L. Gross; Ramalho, Gilberto T. F.; Tsushima, Kazuo

    2010-05-12

    In this study, using SU(3) symmetry to constrain themore » $$\\pi BB'$$ couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at $Q^2=0$.« less

  12. Using baryon octet magnetic moments and masses to fix the pion cloud contribution

    SciTech Connect

    Franz L. Gross; Ramalho, Gilberto T. F.; Tsushima, Kazuo

    2010-05-12

    In this study, using SU(3) symmetry to constrain the $\\pi BB'$ couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at $Q^2=0$.

  13. Unquenched quark model for baryons: Magnetic moments, spins, and orbital angular momenta

    SciTech Connect

    Bijker, R.; Santopinto, E.

    2009-12-15

    We present an unquenched quark model for baryons in which the effects of the quark-antiquark pairs (uu, dd, and ss) are taken into account in an explicit form via a microscopic, QCD-inspired, quark-antiquark creation mechanism. In the present approach, the contribution of the quark-antiquark pairs can be studied for any inital baryon and for any flavor of the qq pairs. It is shown that, while the inclusion of the qq pairs does not affect the baryon magnetic moments, it leads to a sizable contribution of the orbital angular momentum to the spin of the proton and the {lambda} hyperon.

  14. Z = 50 core stability in 110Sn from magnetic-moment and lifetime measurements

    DOE PAGES

    Kumbartzki, G. J.; Benczer-Koller, N.; Speidel, K. -H.; Torres, D. A.; Allmond, James M.; Fallon, P.; Abramovic, I.; L. A. Bernstein; Bevins, J. E.; Crawford, H. L.; et al

    2016-04-18

    In this study, the structure of the semimagic Sn50 isotopes were previously studied via measurements of B(E2;21+ → 01+) and g factors of 21+ states. The values of the B(E2;21+) in the isotopes below midshell at N = 66 show an enhancement in collectivity, contrary to predictions from shell-model calculations. This work presents the first measurement of the 21+ and 41+ states' magnetic moments in the unstable neutron-deficient 110Sn. The g factors provide complementary structure information to the interpretation of the observed B(E2) values.

  15. Remote sensing of the magnetic moment of Uranus - Predictions for Voyager

    NASA Astrophysics Data System (ADS)

    Hill, T. W.; Dessler, A. J.

    1985-03-01

    The current understanding of the power transfer mechanisms by which power is supplied to a planet's magnetosphere by the kinetic energy of planetary spin and the energy flux of the impinging solar wind is applied to the case of Uranus, in order to predict the detectability of radio and auroral emissions by the planetary radio astronomy (PRA) and UV spectrometer (UVS) instruments of the Voyager spacecraft. The power available for the two energy transfer phenomena cited is a function of Uranus' magnetic moment, which is presently derived for each power source as a function of the date of first detection of radio emissions by the PRA or auroral emissions by the UVS.

  16. Bootstrap current close to magnetic axis in tokamaks

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.

    1996-12-01

    It is shown that the bootstrap current density close to the magnetic axis in tokamaks does not vanish in simple electron-ion plasmas because the fraction of the trapped particles is finite. The magnitude of the current density could be comparable to that in the outer core region. This may reduce or even eliminate the need of the seed current.

  17. Moment enhancement in dilute magnetic semiconductors: MnxSi1-x with x = 0.1%

    SciTech Connect

    Shaughnessy, M; Fong, C Y; Snow, R; Liu, K; Pask, J E; Yang, L H

    2009-03-12

    The experimentally determined magnetic moments/Mn, M, in Mn{sub x}Si{sub 1-x} are considered, with particular attention to the case with 5.0 {micro}{sub B}/Mn, obtained for x = 0.1%. The existing theoretical M values for neutral Mn range from 2.83 to 3.78 {micro}B/Mn. To understand the observed M = 5.0 {micro}{sub B}/Mn, we investigated Mn{sub x}Si{sub 1-x} for a series of Mn concentrations and defect configurations using a first-principles density functional method. We find a structure in which the moment is enhanced. It has 5.0 {micro}B/Mn, the Mn at a substitutional site, and a Si at a second-neighbor interstitial site in a large unit cell. Subsequent analysis shows that the observed large moment can be understood as a consequence of the weakened d-p hybridization resulting from the introduction of the second-neighbor interstitial Si and substantial isolation of the Mn-second-neighbor Si complex at such concentrations.

  18. Electron magnetic moment from geonium spectra: Early experiments and background concepts

    NASA Astrophysics Data System (ADS)

    van Dyck, Robert S., Jr.; Schwinberg, Paul B.; Dehmelt, Hans G.

    1986-08-01

    The magnetic moment of a free electron has been measured by observing both its low-energy spin and cyclotron resonances (at νs=ωs/2π and νc=ωc/2π, respectively) by means of a sensitive frequency-shift technique. Using radiation and tuned-circuit damping of a single electron, isolated in a special anharmonicity-compensated Penning trap, also cooled to 4 K, the electron's motion is brought nearly to rest, thus preparing it in a cold quasipermanent state of the geonium ``atom.'' The magnetic-coupling scheme, described as a continuous Stern-Gerlach effect, is made possible through a weak Lawrence magnetic bottle which causes the very narrow axial resonance, at νz=ωz/2π for the harmonically bound electron, to change in frequency by a small fixed amount δ per unit change in magnetic quantum number. Spin flips are indirectly induced by a scheme which weakly drives the axial motion at the νa=ωa/2π spin-cyclotron difference frequency within the inhomogeneous magnetic field, thus yielding a measure of ωa≡ωs-ωc. The magnetic moment μs in terms of the Bohr magneton μB equals (1/2) the spin's g factor, which in turn is described by ωs and ωc: g=2μs/μB=2ωs/ωc. In a Penning trap, however, these resonance frequencies are obtained from the observed cyclotron frequency at ω'c=ωc-δe and the observed anomaly frequency at ω'a=ωs-ω'c, which are related by the small electric shift δe computed using the measured axial frequency and 2δeω'c=ωz 2. This last expression, derived for a perfectly axially symmetric trap, happens to be practically invariant against small imperfections in the electric quadrupole field (error in ωc<10-16). The magnetic-bottle-determined line shapes are analyzed and found to have sharp low-frequency edge features which correspond to the electron being temporarily at the trap center and at the bottom of the magnetic well. Relativistic shifts are considered and found to be <10-11. Our result at the time of submission, g/2=1.001 159

  19. High-Precision Microwave Spectroscopy of Muonium for Determination of Muonic Magnetic Moment

    NASA Astrophysics Data System (ADS)

    Torii, H. A.; Higashi, Y.; Higuchi, T.; Matsuda, Y.; Mizutani, T.; Tajima, M.; Tanaka, K. S.; Ueno, Y.; Fukao, Y.; Iinuma, H.; Ikedo, Y.; Kadono, R.; Kawamura, N.; Koda, A.; Kojima, K. M.; Mibe, T.; Miyake, Y.; Nagamine, K.; Nishiyama, K.; Ogitsu, T.; Okubo, R.; Saito, N.; Sasaki, K.; Shimomura, K.; Strasser, P.; Sugano, M.; Toyoda, A.; Ueno, K.; Yamamoto, A.; Yoshida, M.; Ishida, K.; Iwasaki, M.; Kamigaito, O.; Tomono, D.; Kanda, S.; Kubo, K.; Aoki, M.; Torikai, E.; Kawall, D.

    2016-02-01

    The muonium atom is a system suitable for precision measurements for determination of muon’s fundamental properties as well as for the test of quantum electrodynamics (QED). A microwave spectroscopy experiment of this exotic atom is being prepared at J-PARC, jointly operated by KEK and JAEA in Japan, aiming at an improved relative precision at a level of 10-8 in determination of the muonic magnetic moment. A major improvement of statistical uncertainty is expected with the higher muon intensity of the pulsed beam at J-PARC, while reduction of various sources of systematic uncertainties are being studied: those arising from microwave power fluctuations, magnetic field inhomogeneity, muon stopping distribution and atomic collisional shift of resonance frequencies. Experimental strategy and methods are presented in this paper, with an emphasis on our recent development of apparatuses and evaluation of systematic uncertainties.

  20. Concentration dependence of magnetic moment in Ce1-xFexO2

    NASA Astrophysics Data System (ADS)

    Beausoleil, Geoffrey L.; Thurber, Aaron; Rao, S. S.; Alanko, Gordon; Hanna, C. B.; Punnoose, Alex

    2012-04-01

    In this study, we examined the impact of iron doping on the structural, chemical, and magnetic properties of ceria (Ce1-xFexO2). Samples were produced in triplicate through a coprecipitation approach in a forced hydrolysis synthesis that yielded consistently sized nanocrystals using three different cerium precursors: cerium chloride, cerium ammonium nitrate, and cerium nitrate. Particles were characterized by x ray diffraction (XRD), x ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR) spectroscopy, and vibrating sample magnetometry (VSM). XPS and EPR data shows iron to be in the Fe3+ state and confirms the nominal dopant concentration. The moment per Fe ion found was largest at the lowest dopant concentrations, and quickly decreased as the concentration was increased. We used XPS to estimate the Ce3+/Ce4+ ratio and observed a linear relation between the saturation magnetization and the Ce3+/Ce4+ ratio.

  1. New Measurement of the Anomalous Magnetic Moment of the Positive Muon

    NASA Astrophysics Data System (ADS)

    Carey, R. M.; Earle, W.; Efstathiadis, E.; Hare, M. F.; Hazen, E. S.; Hughes, B. J.; Krienen, F.; Miller, J. P.; Monich, V.; Ouyang, J.; Rind, O.; Roberts, B. L.; Sulak, L. R.; Trofimov, A.; Varner, G.; Worstell, W. A.; Benedict, E.; Logashenko, I.; Benante, J.; Brown, H. N.; Bunce, G.; Cullen, J.; Danby, G. T.; Geller, J.; Hseuh, H.; Jackson, J. W.; Jia, L.; Kochis, S.; Larsen, R.; Lee, Y. Y.; Mapes, M.; Meng, W.; Morse, W. M.; Pai, C.; Pearson, C.; Polk, I.; Prigl, R.; Rankowitz, S.; Sandberg, J.; Semertzidis, Y. K.; Shutt, R.; Snydstrup, L.; Soukas, A.; Stillman, A.; Tallerico, T.; Tanaka, M.; Toldo, F.; von Lintig, D.; Warburton, D.; Woodle, K.; Chertovskikh, A.; Druzhinin, V. P.; Fedotovich, G. V.; Grigorev, D. N.; Golubev, V. B.; Khazin, B. I.; Maksimov, A.; Merzliakov, Yu.; Ryskulov, N.; Serednyakov, S.; Shatunov, Yu. M.; Solodov, E.; Orlov, Y.; Winn, D.; Grossmann, A.; Gerhaeuser, J.; Jungmann, K.; von Walter, P.; Zu Putlitz, G.; Bunker, B.; Deninger, W.; Debevec, P. T.; Hertzog, D. W.; Jones, T. D.; Polly, C.; Sedykh, S.; Urner, D.; Haeberlen, U.; Endo, K.; Hirabayashi, H.; Kurokawa, S.; Yamamoto, A.; Green, M. A.; Cushman, P.; Kindem, J.; Duong, L.; Giron, S.; McNabb, R.; Miller, D.; Timmermans, C.; Zimmerman, D.; Mizumachi, Y.; Iwasaki, M.; Ahn, H. E.; Deng, H.; Dhawan, S. K.; Disco, A.; Farley, F. J.; Fei, X.; Grosse-Perdekamp, M.; Hughes, V. W.; Kawall, D.; Redin, S. I.; Steinmetz, A.

    1999-02-01

    The muon anomalous magnetic moment has been measured in a new experiment at Brookhaven. Polarized muons were stored in a superferric ring, and the angular frequency difference, ωa, between the spin precession and orbital frequencies was determined by measuring the time distribution of high-energy decay positrons. The ratio R of ωa to the Larmor precession frequency of free protons, ωp, in the storage-ring magnetic field was measured. We find R = 3.707 220\\(48\\)×10-3. With μμ/μp = 3.183 345 47\\(47\\) this gives aμ+ = 1 165 925\\(15\\)×10-9 ( +/-13 ppm), in good agreement with the previous CERN measurements for μ+ and μ- and of approximately the same precision.

  2. Muon anomalous magnetic moment and penguin loops in warped extra dimensions

    NASA Astrophysics Data System (ADS)

    Beneke, M.; Moch, P.; Rohrwild, J.

    2014-08-01

    We describe the computation of the one-loop muon anomalous magnetic moment and radiative penguin transitions in the minimal and custodially protected Randall-Sundrum model. A fully five-dimensional (5D) framework is employed to match the 5D theory onto the Standard Model extended by dimension-six operators. The additional contribution to the anomalous magnetic moment from the gauge-boson exchange contributions is $Δ aμ ≈ 8.8 (27.2) ḑot 10-11 × (1 TeV/T)2 ,$ where the first (second) number refers to the minimal (custodially-protected) model. Here 1/T denotes the location of the TeV brane in conformal coordinates, and is related to the mass of the lowest gauge-boson KK excitation by MKK≈2.35T. We also determine the Higgs-exchange contribution, which depends on the 5D Yukawa structure and the precise interpretation of the localization of the Higgs field near or at the TeV brane.

  3. Hadronic light-by-light scattering contribution to the muon anomalous magnetic moment from lattice QCD.

    PubMed

    Blum, Thomas; Chowdhury, Saumitra; Hayakawa, Masashi; Izubuchi, Taku

    2015-01-01

    The most compelling possibility for a new law of nature beyond the four fundamental forces comprising the standard model of high-energy physics is the discrepancy between measurements and calculations of the muon anomalous magnetic moment. Until now a key part of the calculation, the hadronic light-by-light contribution, has only been accessible from models of QCD, the quantum description of the strong force, whose accuracy at the required level may be questioned. A first principles calculation with systematically improvable errors is needed, along with the upcoming experiments, to decisively settle the matter. For the first time, the form factor that yields the light-by-light scattering contribution to the muon anomalous magnetic moment is computed in such a framework, lattice QCD+QED and QED. A nonperturbative treatment of QED is used and checked against perturbation theory. The hadronic contribution is calculated for unphysical quark and muon masses, and only the diagram with a single quark loop is computed for which statistically significant signals are obtained. Initial results are promising, and the prospect for a complete calculation with physical masses and controlled errors is discussed.

  4. Improvement of magnetic hardness at finite temperatures: Ab initio disordered local-moment approach for YCo5

    NASA Astrophysics Data System (ADS)

    Matsumoto, Munehisa; Banerjee, Rudra; Staunton, Julie B.

    2014-08-01

    Temperature dependence of the magnetocrystalline anisotropy energy and magnetization of the prototypical rare-earth magnet YCo5 is calculated from first principles, utilizing the relativistic disordered local-moment approach. We discuss a strategy to enhance the finite-temperature anisotropy field by hole doping, paving the way for an improvement of the coercivity near room temperature or higher.

  5. Large anisotropic Fe orbital moments in perpendicularly magnetized Co2FeAl Heusler alloy thin films revealed by angular-dependent x-ray magnetic circular dichroism

    NASA Astrophysics Data System (ADS)

    Okabayashi, Jun; Sukegawa, Hiroaki; Wen, Zhenchao; Inomata, Koichiro; Mitani, Seiji

    2013-09-01

    Perpendicular magnetic anisotropy (PMA) in Heusler alloy Co2FeAl thin films sharing an interface with a MgO layer is investigated by angular-dependent x-ray magnetic circular dichroism. Orbital and spin magnetic moments are deduced separately for Fe and Co 3d electrons. In addition, the PMA energies are estimated using the orbital magnetic moments parallel and perpendicular to the film surfaces. We found that PMA in Co2FeAl is determined mainly by the contribution of Fe atoms with large orbital magnetic moments, which are enhanced at the interface between Co2FeAl and MgO. Furthermore, element specific magnetization curves of Fe and Co are found to be similar, suggesting the existence of ferromagnetic coupling between Fe and Co PMA directions.

  6. Influence of additional load on the moments of the agonist and antagonist muscle groups at the knee joint during closed chain exercise.

    PubMed

    Rao, Guillaume; Amarantini, David; Berton, Eric

    2009-06-01

    The present study investigated the influence of additional loads on the knee net joint moment, flexor and extensor muscle group moments, and cocontraction index during a closed chain exercise. Loads of 8, 28, or 48 kg (i.e., respectively, 11.1+/-1.5%, 38.8+/-5.3%, and 66.4+/-9.0% of body mass) were added to subjects during dynamic half squats. The flexor and extensor muscular moments and the amount of cocontraction were estimated at the knee joint using an EMG-and-optimization model that includes kinematics, ground reaction, and EMG measurements as inputs. In general, our results showed a significant influence of the Load factor on the net knee joint moment, the extensor muscular moment, and the flexor muscle group moment (all Anova p<.05). Hence we confirmed an increase in muscle moments with increasing load and moreover, we also showed an original "more than proportional" evolution of the flexor and extensor muscle group moments relative to the knee net joint moment. An influence of the Phase (i.e., descent vs. ascent) factor was also seen, revealing different activation strategies from the central nervous system depending on the mode of contraction of the agonist muscle group. The results of the present work could find applications in clinical fields, especially for rehabilitation protocols.

  7. Bonding, moment formation, and magnetic interactions in Ca14MnBi11 and Ba14MnBi11

    NASA Astrophysics Data System (ADS)

    Sánchez-Portal, D.; Martin, Richard M.; Kauzlarich, S. M.; Pickett, W. E.

    2002-04-01

    ``14-1-11'' phase compounds, based on magnetic Mn ions and typified by Ca14MnBi11 and Ba14MnBi11, show an unusual magnetic behavior, but the large number (104) of atoms in the primitive cell has precluded any previous full electronic structure study. Using an efficient, local-orbital-based method within the local-spin-density approximation to study the electronic structure, we find a gap between a bonding valence-band complex and an antibonding conduction-band continuum. The bonding bands lack one electron per formula unit of being filled, making them low carrier density p-type metals. The hole resides in the MnBi4 tetrahedral unit, and partially compensates for the high-spin d5 Mn moment, leaving a net spin near 4μB that is consistent with experiment. These manganites are composed of two disjoint but interpenetrating ``jungle gym'' networks of spin-4/2 MnBi9-4 units with ferromagnetic interactions within the same network, and weaker couplings between the networks whose sign and magnitude is sensitive to materials parameters. Ca14MnBi11 is calculated to be ferromagnetic as observed, while for Ba14MnBi11 (which is antiferromagnetic) the ferromagnetic and antiferromagnetic states are calculated to be essentially degenerate. The band structure of the ferromagnetic states is very close to half metallic.

  8. A Comparison of Methods to Measure the Magnetic Moment of Magnetotactic Bacteria through Analysis of Their Trajectories in External Magnetic Fields

    PubMed Central

    Fradin, Cécile

    2013-01-01

    Magnetotactic bacteria possess organelles called magnetosomes that confer a magnetic moment on the cells, resulting in their partial alignment with external magnetic fields. Here we show that analysis of the trajectories of cells exposed to an external magnetic field can be used to measure the average magnetic dipole moment of a cell population in at least five different ways. We apply this analysis to movies of Magnetospirillum magneticum AMB-1 cells, and compare the values of the magnetic moment obtained in this way to that obtained by direct measurements of magnetosome dimension from electron micrographs. We find that methods relying on the viscous relaxation of the cell orientation give results comparable to that obtained by magnetosome measurements, whereas methods relying on statistical mechanics assumptions give systematically lower values of the magnetic moment. Since the observed distribution of magnetic moments in the population is not sufficient to explain this discrepancy, our results suggest that non-thermal random noise is present in the system, implying that a magnetotactic bacterial population should not be considered as similar to a paramagnetic material. PMID:24349185

  9. Closed expressions for the magnetic field of toroidal multipole configurations

    SciTech Connect

    Sheffield, G.V.

    1983-04-01

    Closed analytic expressions for the vector potential and the magnetic field for the lower order toroidal multipoles are presented. These expressions can be applied in the study of tokamak plasma cross section shaping. An example of such an application is included. These expressions also allow the vacuum fields required for plasma equilibrium to be specified in a general form independent of a particular coil configuration.

  10. Magnetization, magnetic susceptibility, effective magnetic moment of Fe{sup 3+} ions in Bi{sub 25}FeO{sub 39} ferrite

    SciTech Connect

    Zatsiupa, A.A.; Bashkirov, L.A.; Troyanchuk, I.O.; Petrov, G.S.; Galyas, A.I.; Lobanovsky, L.S.; Truhanov, S.V.

    2014-04-01

    Magnetic susceptibility for ferrite Bi{sub 25}FeO{sub 39} is measured at 5–950 K in the magnetic field of 0.86 T. It is shown that Bi{sub 25}FeO{sub 39} is paramagnetic in the temperature range 5−950 K. The saturation magnetization is equal to 5.04μ{sub B} per formula unit at 5 K in a magnetic field of 10 T. It is found that at 5−300 K the effective magnetic moment of Fe{sup 3+} ions in Bi{sub 25}FeO{sub 39} is equal to 5.82μ{sub B}. - Graphical abstract: The dependence of the magnetization (n, μ{sub B}) on the magnetic field for one formula unit of Bi{sub 25}FeO{sub 39} at 5 K. - Highlights: • Magnetic susceptibility for Bi{sub 25}FeO{sub 39} is measured at 5–950 K in the magnetic field of 0.86 T. • It is shown that Bi{sub 25}FeO{sub 39} is paramagnetic in the temperature range 5−950 K. • The saturation magnetization is equal to 5.04μ{sub B} per formula unit at 5 K in a magnetic field of 10 T.

  11. QPNM calculation for the ground state magnetic moments of odd-mass deformed nuclei: 157-167Er isotopes

    NASA Astrophysics Data System (ADS)

    Yakut, H.; Guliyev, E.; Guner, M.; Tabar, E.; Zenginerler, Z.

    2012-08-01

    A new microscopic method has been developed in the framework of the Quasiparticle-Phonon Nuclear Model (QPNM) in order to investigate spin polarization effects on the magnetic properties such as magnetic moment, intrinsic magnetic moment and effective gs factor of the ground state of odd-mass 157-167Er isotopes. The calculations were performed using both Tamm-Dancoff Approximation (TDA) and Quasiparticle Random-Phase Approximation (QRPA). Reasonably good agreement has been obtained between the QRPA results and the relevant experimental data. Furthermore the variation of the intrinsic magnetic moment gK values with the mass number A exhibits similar behavior for both theoretical and experimental results. From the compression of the calculated intrinsic magnetic moment values with the experimental data the spin-spin interaction parameter has been found as χ=(30/A) MeV for odd-mass 157-167Er isotopes. Our results clarify the possibility of using this new method to describe the magnetic properties of odd-mass deformed nuclei.

  12. Covariant Spectator Theory of np scattering: Deuteron magnetic moment and form factors

    SciTech Connect

    Gross, Franz L.

    2014-06-01

    The deuteron magnetic moment is calculated using two model wave functions obtained from 2007 high precision fits to $np$ scattering data. Included in the calculation are a new class of isoscalar $np$ interaction currents which are automatically generated by the nuclear force model used in these fits. After normalizing the wave functions, nearly identical predictions are obtained: model WJC-1, with larger relativistic P-state components, gives 0.863(2), while model WJC-2 with very small $P$-state components gives 0.864(2) These are about 1\\% larger than the measured value of the moment, 0.857 n.m., giving a new prediction for the size of the $\\rho\\pi\\gamma$ exchange, and other purely transverse interaction currents that are largely unconstrained by the nuclear dynamics. The physical significance of these results is discussed, and general formulae for the deuteron form factors, expressed in terms of deuteron wave functions and a new class of interaction current wave functions, are given.

  13. Itinerancy-Enhanced Quantum Fluctuation of Magnetic Moments in Iron-Based Superconductors

    NASA Astrophysics Data System (ADS)

    Tam, Yu-Ting; Yao, Dao-Xin; Ku, Wei

    We investigate the influence of itinerant carriers on dynamics and fluctuation of local moments in Fe-based superconductors, via linear spin-wave analysis of a spin-fermion model containing both itinerant and local degrees of freedom.Surprisingly against the common lore, instead of enhancing the (π,0) order, itinerant carriers with well nested Fermi surfaces are found to induce a significant amount of spatial and temporal quantum fluctuation that leads to the observed small ordered moment. Interestingly, the underlying mechanism is shown to be intra-pocket nesting-associated long-range coupling rather than the previously believed ferromagnetic double-exchange effect. This challenges the validity of ferromagnetically compensated first-neighbor coupling reported from short-range fitting to the experimental dispersion, which turns out to result instead from the ferro-orbital order that is also found instrumental in stabilizing the magnetic order. *Y.-T. Tam, D.-X. Yao and W. Ku, Phys. Rev. Lett. 115, 117001 (2015) Work supported by US DOE No.DE-AC02-98CH10886 and CHN No. NBRPC-2012CB821400, No. NSFC-11275279.

  14. Validity of closed periodic magnetic focusing for sheet electron beams

    SciTech Connect

    Zhao Ding

    2009-11-15

    Theoretical analyses and numerical calculations have demonstrated that a closed periodic cusped magnetic (PCM) field can effectively confine a sheet electron beam in two transverse directions (i.e., in the wide and narrow dimensions, simultaneously) for stable long distance transport in which the sizes of the beam cross section are set by referring to the present state of the art. Moreover, the method for matching the transverse magnetic focusing force and the inner space charge force in the wide dimension of the sheet electron beam is given, and the longitudinal periodic length and the cross sectional shape of the closed PCM focusing structure can be determined. Calculations also demonstrate that the optimum focusing state can be attained by adjusting the wide dimension on the transverse section of the closed PCM structure independently. The work presented in this paper indicates that the closed PCM structure is very promising for the confinement of the sheet electron beam, and it can be helpful for guiding practical engineering design.

  15. The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters

    SciTech Connect

    Meyer, Jennifer; Tombers, Matthias; Wüllen, Christoph van; Niedner-Schatteburg, Gereon; Peredkov, Sergey; Eberhardt, Wolfgang; Neeb, Matthias; Palutke, Steffen; Martins, Michael; Wurth, Wilfried

    2015-09-14

    We present size dependent spin and orbital magnetic moments of cobalt (Co{sub n}{sup +}, 8 ≤ n ≤ 22), iron (Fe{sub n}{sup +}, 7 ≤ n ≤ 17), and nickel cluster (Ni{sub n}{sup +}, 7 ≤ n ≤ 17) cations as obtained by X-ray magnetic circular dichroism (XMCD) spectroscopy of isolated clusters in the gas phase. The spin and orbital magnetic moments range between the corresponding atomic and bulk values in all three cases. We compare our findings to previous XMCD data, Stern-Gerlach data, and computational results. We discuss the application of scaling laws to the size dependent evolution of the spin and orbital magnetic moments per atom in the clusters. We find a spin scaling law “per cluster diameter,” ∼n{sup −1/3}, that interpolates between known atomic and bulk values. In remarkable contrast, the orbital moments do likewise only if the atomic asymptote is exempt. A concept of “primary” and “secondary” (induced) orbital moments is invoked for interpretation.

  16. Bound on the tau neutrino magnetic moment from the TRISTAN experiments

    NASA Astrophysics Data System (ADS)

    Tanimoto, N.; Nakano, I.; Sakuda, M.

    2000-04-01

    We set limits on the magnetic moment and charge radius of the tau neutrino by examining an extra contribution to the electroweak process e+e--->ννoverlineγ using VENUS, TOPAZ and AMY results. We find that κ(ντ)<9.1×10-6 (i.e. μ(ντ)<9.1×10-6μB, μB=e/2me) and <3.1×10-31 cm2 with Poisson statistics by combining their results. Whereas, similar to this method, with the Unified Approach we find that κ(ντ)<8.0×10-6 and <2.7×10-31 cm2.

  17. Magnetic moment and plasma environment of HD 209458b as determined from Lyα observations

    NASA Astrophysics Data System (ADS)

    Kislyakova, Kristina G.; Holmström, Mats; Lammer, Helmut; Odert, Petra; Khodachenko, Maxim L.

    2014-11-01

    Transit observations of HD 209458b in the stellar Lyman-α(Lyα) line revealed strong absorption in both blue and red wings of the line interpreted as hydrogen atoms escaping from the planet’s exosphere at high velocities. The following sources for the absorption were suggested: acceleration by the stellar radiation pressure, natural spectral line broadening, or charge exchange with the stellar wind. We reproduced the observation by means of modeling that includes all aforementioned processes. Our results support a stellar wind with a velocity of ≈400 kilometers per second at the time of the observation and a planetary magnetic moment of ≈1.6 × 1026 amperes per square meter.

  18. Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment

    DOE PAGES

    Burger, Florian; Feng, Xu; Hotzel, Grit; Jansen, Karl; Petschlies, Marcus; Renner, Dru B.

    2014-02-24

    We present a four-flavour lattice calculation of the leading-order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon, aμhvp, arising from quark-connected Feynman graphs. It is based on ensembles featuring Nf=2+1+1 dynamical twisted mass fermions generated by the European Twisted Mass Collaboration (ETMC). Several light quark masses are used in order to yield a controlled extrapolation to the physical pion mass. We employ three lattice spacings to examine lattice artefacts and several different volumes to check for finite-size effects. Including the complete first two generations of quarks allows for a direct comparison with phenomenological determinations of amore » μhvp. The final result involving an estimate of the systematic uncertainty aμhvp=6.74 (21)(18) 10-8 shows a good overall agreement with these computations.« less

  19. Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Braumüller, Jochen; Sandberg, Martin; Vissers, Michael R.; Schneider, Andre; Schlör, Steffen; Grünhaupt, Lukas; Rotzinger, Hannes; Marthaler, Michael; Lukashenko, Alexander; Dieter, Amadeus; Ustinov, Alexey V.; Weides, Martin; Pappas, David P.

    2016-01-01

    We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a straightforward fabrication process using Al evaporation and lift-off lithography, we observe qubit lifetimes and coherence times in the order of 10 μ s . We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. Due to the large loop size, the presented qubit architecture features a strongly increased magnetic dipole moment as compared to conventional transmon designs. This renders the concentric transmon a promising candidate to establish a site-selective passive direct Z ̂ coupling between neighboring qubits, being a pending quest in the field of quantum simulation.

  20. Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment

    SciTech Connect

    Burger, Florian; Feng, Xu; Hotzel, Grit; Jansen, Karl; Petschlies, Marcus; Renner, Dru B.

    2014-02-24

    We present a four-flavour lattice calculation of the leading-order hadronic vacuum polarisation contribution to the anomalous magnetic moment of the muon, aμhvp, arising from quark-connected Feynman graphs. It is based on ensembles featuring Nf=2+1+1 dynamical twisted mass fermions generated by the European Twisted Mass Collaboration (ETMC). Several light quark masses are used in order to yield a controlled extrapolation to the physical pion mass. We employ three lattice spacings to examine lattice artefacts and several different volumes to check for finite-size effects. Including the complete first two generations of quarks allows for a direct comparison with phenomenological determinations of a μhvp. The final result involving an estimate of the systematic uncertainty aμhvp=6.74 (21)(18) 10-8 shows a good overall agreement with these computations.

  1. Finite-element quantum electrodynamics: Canonical formulation, unitarity, and the magnetic moment of the electron

    SciTech Connect

    Miller, D.; Milton, K.A.; Siegemund-Broka, S. )

    1992-07-15

    This is the first in a series of papers dealing with four-dimensional quantum electrodynamics on a finite-element lattice. We begin by studying the canonical structure of the theory without interactions. This tells us how to construct momentum expansions for the field operators. Next we examine the interaction term in the Dirac equation. We construct the transfer matrix explicitly in the temporal gauge, and show that it is unitary. Therefore, fermion canonical anticommutation relations hold at each lattice site. Finally, we expand the interaction term to second order in the temporal-lattice spacing and deduce the magnetic moment of the electron in a background field, consistent with the continuum value of {ital g}=2.

  2. Dark matter, LFV and neutrino magnetic moment in the radiative seesaw model with fermion triplet

    NASA Astrophysics Data System (ADS)

    Chao, Wei

    2015-01-01

    In this paper we work in the framework of a radiative seesaw model with triplet fermion Σ. Due to the Z2 discrete flavor symmetry, the lightest neutral component of Σ is stable and thus can be a dark matter candidate. Its mass can be solely determined by the dark matter relic abundance, which is bout 2.594 TeV. It can still constitute 30% of the dark matter when considering constraints from dark matter indirect detection experiments. The model also predict a dark matter-nucleus scattering cross-section that would be accessible with future dark matter direct detection searches. We further investigate constraints on the parameter space of the model from the lepton-flavor-violating processes and neutrino transition magnetic moments, induced by the Yukawa interaction of the Σ with the left-handed lepton doublets.

  3. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

    NASA Astrophysics Data System (ADS)

    White, B. D.; Yazici, D.; Ho, P.-C.; Kanchanavatee, N.; Pouse, N.; Fang, Y.; Breindel, A. J.; Friedman, A. J.; Maple, M. B.

    2015-08-01

    We report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of  ˜6.7-6.8 Å between Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya-Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4 f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order; however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.

  4. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

    DOE PAGES

    White, B. D.; Yazici, D.; Ho, P. -C.; Kanchanavatee, N.; Pouse, N.; Fang, Y.; Breindel, A. J.; Friedman, A. J.; Maple, M. B.

    2015-07-20

    Here, we report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of ~6.7- 6.8 Å between Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya- Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order;more » however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.« less

  5. Status of Works on A-40-MCI-Activity Tritium Source for the Measurement of the Antineutrino Magnetic Moment

    SciTech Connect

    Yukhimchuk, A.A.; Vinogradov, Yu.I.; Golubkov, A.N.; Grishechkin, S.K.; Il'kaev, R.I.; Kuryakin, A.V.; Lebedev, B.L.; Lobanov, V.N.; Mikhailov, V.N.; Tumkin, D.P.; Bogdanova, L.N.

    2005-07-15

    For the experiment on the measurement of the electron antineutrino magnetic moment we suggest a new approach to the tritium source design, namely, a configuration of annular cells filled with TiT{sub 2} that are stacked into a hollow cylinder. Detectors are mounted in the hole inside.We present results of the optimization of geometrical and physical parameters of the source with respect to its experimental effectiveness and safety guaranty at all stages of its lifecycle. We discuss the choice of the construction materials and specify technological issues relevant to radiation purity of the source, being of the special concern in the experiment on the electron antineutrino magnetic moment measurement.

  6. Magnetic moment enhancement and spin polarization switch of the manganese phthalocyanine molecule on an IrMn(100) surface

    NASA Astrophysics Data System (ADS)

    Sun, X.; Wang, B.; Pratt, A.; Yamauchi, Y.

    2014-07-01

    The geometric, electronic, and magnetic structures of a manganese phthalocyanine (MnPc) molecule on an antiferromagnetic IrMn(100) surface are studied by density functional theory calculations. Two kinds of orientation of the adsorbed MnPc molecule are predicted to coexist due to molecular self-assembly on the surface—a top-site geometry with the Mn-N bonds aligned along the ⟨100⟩ direction, and a hollow-site orientation in which the Mn-N bonds are parallel to the ⟨110⟩ direction. The MnPc molecule is antiferromagnetically coupled to the substrate at the top site with a slight reduction in the magnetic moment of the Mn atom of the MnPc molecule (Mnmol). In contrast, the magnetic moment of the Mnmol is enhanced to 4.28 μB at the hollow site, a value larger than that in the free MnPc molecule (3.51 μB). Molecular distortion induced by adsorption is revealed to be responsible for the enhancement of the magnetic moment. Furthermore, the spin polarization of the Mnmol atom at around the Fermi level is found to change from negative to positive through an elongation of the Mn-N bonds of the MnPc. We propose that a reversible switch of the low/high magnetic moment and negative/positive spin polarization might be realized through some mechanical engineering methods.

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

    NASA Astrophysics Data System (ADS)

    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) .

  8. Estimate of the hadronic vacuum polarization disconnected contribution to the anomalous magnetic moment of the muon from lattice QCD

    NASA Astrophysics Data System (ADS)

    Chakraborty, Bipasha; Davies, C. T. H.; Koponen, J.; Lepage, G. P.; Peardon, M. J.; Ryan, S. M.

    2016-04-01

    The quark-line disconnected diagram is a potentially important ingredient in lattice QCD calculations of the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon. It is also a notoriously difficult one to evaluate. Here, for the first time, we give an estimate of this contribution based on lattice QCD results that have a statistically significant signal, albeit at one value of the lattice spacing and an unphysically heavy value of the u /d quark mass. We use HPQCD's method of determining the anomalous magnetic moment by reconstructing the Adler function from time moments of the current-current correlator at zero spatial momentum. Our results lead to a total (including u , d and s quarks) quark-line disconnected contribution to aμ of -0.15 % of the u /d hadronic vacuum polarization contribution with an uncertainty which is 1% of that contribution.

  9. Coronal Jets in Closed Magnetic Regions on the Sun

    NASA Astrophysics Data System (ADS)

    Wyper, Peter Fraser; DeVore, C. R.

    2015-04-01

    Coronal jets are dynamic, collimated structures observed in solar EUV and X-ray emission. They appear predominantly in the open field of coronal holes, but are also observed in areas of closed field, especially active regions. A common feature of coronal jets is that they originate from the field above a parasitic polarity of opposite sign to the surrounding field. Some process - such as instability onset or flux emergence - induces explosive reconnection between the closed “anemone” field and the surrounding open field that generates the jet. The lesser number of coronal jets in closed-field regions suggests a possible stabilizing effect of the closed configuration with respect to coronal jet formation. If the scale of the jet region is small compared with the background loop length, as in for example type II spicules, the nearby magnetic field may be treated as locally open. As such, one would expect that if a stabilizing effect exists it becomes most apparent as the scale of the anemone region approaches that of the background coronal loops.To investigate if coronal jets are indeed suppressed along shorter coronal loops, we performed a number of simulations of jets driven by a rotation of the parasitic polarity (as in the previous open-jet calculations by Pariat et. al 2009, 2010, 2015) embedded in a large-scale closed bipolar field. The simulations were performed with the state of the art Adaptively Refined Magnetohydrodynamics Solver. We will report here how the magnetic configuration above the anemone region determines the nature of the jet, when it is triggered, and how much of the stored magnetic energy is released. We show that regions in which the background field and the parasitic polarity region are of comparable scale naturally suppress explosive energy release. We will also show how in the post-jet relaxation phase a combination of confined MHD waves and weak current layers are generated by the jet along the background coronal loops, both of which

  10. Two-dimensional molecular magnets with weak topological invariant magnetic moments: mathematical prediction of targets for chemical synthesis

    PubMed Central

    Packwood, D. M.; Reaves, K. T.; Federici, F. L.; Katzgraber, H. G.; Teizer, W.

    2013-01-01

    An open problem in applied mathematics is to predict interesting molecules that are realistic targets for chemical synthesis. In this paper, we use a spin Hamiltonian-type model to predict molecular magnets (MMs) with magnetic moments that are intrinsically robust under random shape deformations to the molecule. Using the concept of convergence in probability, we show that for MMs in which all spin centres lie in-plane and all spin centre interactions are ferromagnetic, the total spin of the molecule is a ‘weak topological invariant’ when the number of spin centres is sufficiently large. By weak topological invariant, we mean that the total spin of the molecule depends only upon the arrangement of spin centres in the molecule, and is unlikely to change under shape deformations to the molecule. Our calculations show that only between 20 and 50 spin centres are necessary for the total spin of these MMs to be a weak topological invariant. The robustness effect is particularly enhanced for two-dimensional ferromagnetic MMs that possess a small number of spin rings in the structure. PMID:24353469

  11. First principles density functional calculation of magnetic moment and hyperfine fields of dilute transition metal impurities in Gd host

    NASA Astrophysics Data System (ADS)

    Mohanta, S. K.; Mishra, S. N.; Srivastava, S. K.

    2014-04-01

    We present first principles calculations of electronic structure and magnetic properties of dilute transition metal (3d, 4d and 5d) impurities in a Gd host. The calculations have been performed within the density functional theory using the full potential linearized augmented plane wave technique and the GGA+U method. The spin and orbital contributions to the magnetic moment and the hyperfine fields have been computed. We find large magnetic moments for 3d (Ti-Co), 4d (Nb-Ru) and 5d (Ta-Os) impurities with magnitudes significantly different from the values estimated from earlier mean field calculation [J. Magn. Magn. Mater. 320 (2008) e446-e449]. The exchange interaction between the impurity and host Gd moments is found to be positive for early 3d elements (Sc-V) while in all other cases an anti-ferromagnetic coupling is observed. The trends for the magnetic moment and hyperfine field of d-impurities in Gd show qualitative difference with respect to their behavior in Fe, Co and Ni. The calculated total hyperfine field, in most cases, shows excellent agreement with the experimental results. A detailed analysis of the Fermi contact hyperfine field has been made, revealing striking differences for impurities having less or more than half filled d-shell. The impurity induced perturbations in host moments and the change in the global magnetization of the unit cell have also been computed. The variation within each of the d-series is found to correlate with the d-d hybridization strength between the impurity and host atoms.

  12. Nuclear magnetic moments of the ground states of sup 124 I, sup 126 I, and sup 130 I

    SciTech Connect

    Ohya, S.; Yamazaki, T.; Harasawa, T.; Katsurayama, M.; Mutsuro, N. ); Muto, S.; Heiguchi, K. )

    1992-01-01

    The nuclear magnetic moments of {sup 124}I, {sup 126}I, and {sup 130}I have been measured by the techniques of low-temperature nuclear orientation and nuclear magnetic resonance on oriented nuclei. The magnetic hyperfine splitting frequency {vert bar}{ital g}{mu}{sub {ital N}BHF}/{ital h}{vert bar} for {sup 124}I{ital Fe} was determined to be 630.2(2) MHz from a field-shift analysis of the measured resonances at the external field of 0.1, 0.2, 0.4, 0.6, and 0.8 T. The resonances for {sup 126}I{ital Fe} and {sup 130}I{ital Fe} were observed in an external magnetic field of 0.2 T at {nu}({sup 126}I{ital Fe})=627.7(2) MHz and {nu}({sup 130}I{ital Fe})=585.7(2) MHz, respectively. Using the recalculated hyperfine field of {ital B}{sub HF}({sup 131}I{ital Fe})=114.50(5) T, the magnetic moments were deduced: {vert bar}{mu}({sup 124}I,2{sup {minus}}){vert bar}=1.444(4){mu}{sub {ital N}}, {vert bar}{mu}({sup 126}I,2{sup {minus}}){vert bar}=1.436(5){mu}{sub {ital N}}, and {vert bar}{mu}({sup 130}I,5{sup +}){vert bar}=3.349(7){mu}{sub {ital N}}. The present value of the magnetic moment of {sup 124}I is very different from the value of 1.14(8){mu}{sub {ital N}} reported previously. The measured values of the magnetic moments are discussed using Lande formula.

  13. Prospects for ultracold polar and magnetic chromium-closed-shell-atom molecules

    NASA Astrophysics Data System (ADS)

    Tomza, Michał

    2013-07-01

    The properties of the electronic ground state of the polar and paramagnetic chromium-closed-shell-atom molecules have been investigated. State-of-the-art ab initio techniques have been applied to compute the potential energy curves for the chromium-alkaline-earth-metal-atom, CrX (X=Be, Mg, Ca, Sr, Ba), and chromium-ytterbium, CrYb, molecules in the Born-Oppenheimer approximation for the high-spin X7Σ+ electronic ground state. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), was employed and the scalar relativistic effects within the Douglas-Kroll-Hess Hamiltonian or energy-consistent pseudopotentials were included. The permanent electric dipole moments and static electric dipole polarizabilities were computed. The leading long-range coefficients describing the dispersion interaction between the atoms at large interatomic distances C6 are also reported. The molecules under investigation are examples of species possessing both large magnetic and electric dipole moments making them potentially interesting candidates for ultracold many-body physics studies.

  14. Magnetic moments around the Z =40 shell closure: sup 91 Y sup m , sup 95 Zr, and sup 97 Nb

    SciTech Connect

    Berkes, I.; De Jesus, M.; Hlimi, B.; Massaq, M.; Sayouty, E.H. ); Heyde, K. )

    1991-07-01

    Magnetic moments around the {ital Z}=40 shell closure have been established using nuclear magnetic resonance on oriented nuclei in iron. From the resonance frequencies we established {vert bar}{mu}({sup 91}Y;9/2{sup +}){vert bar}=6.01({sub {minus}15}{sup +31}){mu}{sub {ital N}}, {vert bar}{mu}({sup 95}Zr; 5/2{sup +}){vert bar}=1.103(23){mu}{sub {ital N}}, {vert bar}{mu}({sup 97}Nb;9/2{sup +}){vert bar}=6.153(5){mu}{sub {ital N}}. The results obtained are discussed in the framework of particle-core coupling and, in more detail, using the Nilsson deformed single-particle model. It is shown that for certain deformation regions the measurement of the magnetic moment can give information on the nuclear quadrupole deformation.

  15. Single-Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln4 Squares.

    PubMed

    Das, Chinmoy; Vaidya, Shefali; Gupta, Tulika; Frost, Jamie M; Righi, Mattia; Brechin, Euan K; Affronte, Marco; Rajaraman, Gopalan; Shanmugam, Maheswaran

    2015-10-26

    Three cationic [Ln4 ] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy4 (μ4 -OH)(HL)(H2 L)3 (H2 O)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)8 (1), [Tb4 (μ4 -OH)(HL)(H2 L)3 (MeOH)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)4 (2) and [Gd4 (μ4 -OH)(HL)(H2 L)3 (H2 O)2 (MeOH)2 ]Br2 ⋅(CH3 OH)4 ⋅(H2 O)3 (3). The structures are described as hydroxo-centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H2 L(2-) ligand. Alternating current magnetic susceptibility measurements show frequency-dependent out-of-phase signals with two different thermally assisted relaxation processes for 1, whereas no maxima in χM " appears above 2.0 K for complex 2. For 1, the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J1 =+0.01 and J2 =-0.01 cm(-1) for 1 as the two distinct exchange interactions between the Dy(III) ions. Similar parameters are also obtained for complex 1 (and 2) from specific heat measurements. A very weak antiferromagnetic super-exchange interaction (J1 =-0.043 cm(-1) and g=1.99) is observed between the metal centers in 3. The magnetocaloric effect (MCE) was estimated by using field-dependent magnetization and temperature-dependent heat-capacity measurements. An excellent agreement is found for the -ΔSm values extracted from these two measurements for all three complexes. As expected, 3 shows the largest -ΔSm variation (23 J Kg(-1)  K(-1) ) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super-exchange interaction facilitates dense population of low-lying excited states, all of

  16. Single-Molecule Magnetism, Enhanced Magnetocaloric Effect, and Toroidal Magnetic Moments in a Family of Ln4 Squares.

    PubMed

    Das, Chinmoy; Vaidya, Shefali; Gupta, Tulika; Frost, Jamie M; Righi, Mattia; Brechin, Euan K; Affronte, Marco; Rajaraman, Gopalan; Shanmugam, Maheswaran

    2015-10-26

    Three cationic [Ln4 ] squares (Ln=lanthanide) were isolated as single crystals and their structures solved as [Dy4 (μ4 -OH)(HL)(H2 L)3 (H2 O)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)8 (1), [Tb4 (μ4 -OH)(HL)(H2 L)3 (MeOH)4 ]Cl2 ⋅(CH3 OH)4 ⋅(H2 O)4 (2) and [Gd4 (μ4 -OH)(HL)(H2 L)3 (H2 O)2 (MeOH)2 ]Br2 ⋅(CH3 OH)4 ⋅(H2 O)3 (3). The structures are described as hydroxo-centered squares of lanthanide ions, with each edge of the square bridged by a doubly deprotonated H2 L(2-) ligand. Alternating current magnetic susceptibility measurements show frequency-dependent out-of-phase signals with two different thermally assisted relaxation processes for 1, whereas no maxima in χM " appears above 2.0 K for complex 2. For 1, the estimated effective energy barrier for these two relaxation processes is 29 and 100 K. Detailed ab initio studies reveal that complex 1 possesses a toroidal magnetic moment. The ab initio calculated anisotropies of the metal ions in complex 1 were employed to simulate the magnetic susceptibility by using the Lines model (POLY_ANISO) and this procedure yields J1 =+0.01 and J2 =-0.01 cm(-1) for 1 as the two distinct exchange interactions between the Dy(III) ions. Similar parameters are also obtained for complex 1 (and 2) from specific heat measurements. A very weak antiferromagnetic super-exchange interaction (J1 =-0.043 cm(-1) and g=1.99) is observed between the metal centers in 3. The magnetocaloric effect (MCE) was estimated by using field-dependent magnetization and temperature-dependent heat-capacity measurements. An excellent agreement is found for the -ΔSm values extracted from these two measurements for all three complexes. As expected, 3 shows the largest -ΔSm variation (23 J Kg(-1)  K(-1) ) among the three complexes. The negligible magnetic anisotropy of Gd indeed ensures near degeneracy in the (2S+1) ground state microstates, and the weak super-exchange interaction facilitates dense population of low-lying excited states, all of

  17. Enhancement of magnetic moment in ZnxFe3-xO4 thin films with dilute Zn substitution

    NASA Astrophysics Data System (ADS)

    Yuan, Honglei; Liu, Er; Yin, Yuli; Zhang, Wen; Wong, P. K. Johnny; Zheng, Jian-Guo; Huang, Zhaocong; Ou, Huiling; Zhai, Ya; Xu, Qingyu; Du, Jun; Zhai, Hongru

    2016-06-01

    Highly (111)-textured ZnxFe3-xO4 thin films were grown by pulsed laser deposition on silicon substrates. The spin and orbital magnetic moments of the ZnxFe3-xO4 thin films have been obtained by X-ray magnetic circular dichroism (XMCD) and sum rule analysis. The total magnetic moments thus extracted are in good agreement with the values obtained by vibrating sample magnetometer. Both the unquenched orbital moment and the ratio of orbital-to-spin moment first increase significantly with increasing Zn substitution at a low concentration range ( 0 ≤x ≤0.1 ), and then decrease at a higher concentration (x = 0.3). The underlying site-specific doping mechanisms involved here have been elucidated by detailed analysis of the XMCD of ZnxFe3-xO4 films. Our work demonstrates a practical means to manipulate the spin-orbit coupling in the ZnxFe3-xO4 thin films via Zn impurity doping.

  18. CP-violating effect of the Th nuclear magnetic quadrupole moment: accurate many-body study of ThO.

    PubMed

    Skripnikov, L V; Petrov, A N; Titov, A V; Flambaum, V V

    2014-12-31

    Investigations of CP violation in the hadron sector may be done using measurements in the ThO molecule. Recent measurements in this molecule improved the limit on the electron electric dipole moment (EDM) by an order of magnitude. Another time-reversal (T) and parity (P)-violating effect in 229ThO is induced by the nuclear magnetic quadrupole moment. We perform nuclear and molecular calculations to express this effect in terms of the strength constants of T, P-odd nuclear forces, neutron EDM, QCD vacuum angle θ, quark EDM, and chromo-EDM.

  19. Gas-phase NMR measurements, absolute shielding scales, and magnetic dipole moments of 29Si and 73Ge nuclei.

    PubMed

    Makulski, W; Jackowski, K; Antusek, A; Jaszuński, M

    2006-10-12

    New gas-phase NMR measurements of the shielding constants of 29Si, 73Ge, and 1H nuclei in SiH4 and GeH4 are reported. The results, extrapolated to zero density, provide accurate isolated molecule values, best suited for comparison with theoretical calculations. Using the recent ab initio results for these molecules and the measured chemical shifts, we determine the absolute shielding scales for 29Si and 73Ge. This allows us to provide new values of the nuclear magnetic dipole moments for these two nuclei; in addition, we examine the dipole moments of 13C and 119Sn.

  20. A new software for the measurement of magnetic moments using SQUID and spinner magnetometers

    NASA Astrophysics Data System (ADS)

    Wack, M.

    2010-09-01

    A new software package, called CryoMag, facilitates the measurement of magnetic moments using both 3-component (i.e. Superconducting QUantum Interference Device) and 2-component (i.e. spinner) magnetometers. The measurement process is optimized for, but not limited to, stepwise demagnetization experiments commonly used in paleomagnetism. A graphical representation of the data is always visible to the user in the form of orthogonal, stereonet and decay diagrams, which can be represented in in situ, geographic or tilt corrected coordinates and can be saved as graphics files. Instrument specific settings, as well as arbitrary measurement positions, can be easily customized in a single configuration file. A comprehensive record of detailed measurement and statistical data is stored in XML (eXtensible Markup Language) based data files (*.cmag.xml). The final results of the measurements can be exported to several common file formats for further processing. The software is written in Python, an open source, cross-platform programming language and can therefore be used on popular operating systems like Windows, Linux and MacOS X. The complete source code is available on request from the author. The CryoMag open-source allows anyone to adapt the software to their specific equipment, file format and experimental requirements.

  1. A new software for the measurement of magnetic moments using a SQUID magnetometer

    NASA Astrophysics Data System (ADS)

    Wack, M.

    2009-12-01

    A new software package called CryoMag to carry out measurements of magnetic moments is presented. It is designed to work with SQUID magnetometers manufactured by 2G Enterprises, but the modular design allows easy adaption to other instruments like spinner magnetometers as well. The measurement process is optimized for, but not limited to, stepwise demagnetization experiments commonly used in paleomagnetism. A graphical representation of the data is always visible to the user in the form of orthogonal, stereographic and decay plots, which can be represented in in-situ, geographic or tilt corrected coordinates and can be saved to graphics files. Measurement positions can be easily customized. A comprehensive record of detailed measurement and statistical data is stored in XML (eXtensible Markup Language) based data files (*.cmag.xml). The final results of the measurements can be exported to various common file formats for further processing. The software is written in Python, an open source, cross-platform programming language and can therefore be used on all major operating systems like Windows, Linux and MacOS X (not tested).

  2. CPT Test with (anti)proton Magnetic Moments Based on Quantum Logic Cooling and Readout

    NASA Astrophysics Data System (ADS)

    Niemann, M.; Paschke, A.-G.; Dubielzig, T.; Ulmer, S.; Ospelkaus, C.

    2014-01-01

    Dehmelt and VanDyck's famous 1987 measurement of the electron and positron g-factor is still the most precise g-factor comparison in the lepton sector, and a sensitive test of possible CPT violation. A complementary g-factor comparison between the proton and the antiproton is highly desirable to test CPT symmetry in the baryon sector. Current experiments, based on Dehmelt's continuous Stern-Gerlach effect and the double Penning-trap technique, are making rapid progress. They are, however, extremely difficult to carry out because ground state cooling using cryogenic techniques is virtually impossible for heavy baryons, and because the continous Stern-Gerlach effect scales as μ/m, where m is the mass of the particle and μ its magnetic moment. Both difficulties will ultimately limit the accuracy. We discuss experimental prospects of realizing an alternative approach to a g-factor comparison with single (anti)protons, based on quantum logic techniques proposed by Heinzen and Wineland and by Wineland et al. The basic idea is to cool, control and measure single (anti)protons through interaction with a well-controlled atomic ion.

  3. Macroscopic kinematics of the Hall electric field under influence of carrier magnetic moments

    NASA Astrophysics Data System (ADS)

    Sakai, Masamichi

    2016-06-01

    The relativistic effect on electromagnetic forces yields two types of forces which depend on the velocity of the relevant particles: (i) the usual Lorentz force exerted on a moving charged particle and (ii) the apparent Lorentz force exerted on a moving magnetic moment. In sharp contrast with type (i), the type (ii) force originates due to the transverse field induced by the Hall effect (HE). This study incorporates both forces into a Drude-type equation with a fully spin-polarized condition to investigate the effects of self-consistency of the source and the resultant fields on the HE. We also examine the self-consistency of the carrier kinematics and electromagnetic dynamics by simultaneously considering the Drude type equation and Maxwell equations at low frequencies. Thus, our approach can predict both the dc and ac characteristics of the HE, demonstrating that the dc current condition solely yields the ordinary HE, while the ac current condition yields generation of both fundamental and second harmonic modes of the HE field. When the magnetostatic field is absent, the simultaneous presence of dc and ac longitudinal currents generates the ac HE that has both fundamental frequency and second harmonic.

  4. Magnetic moment enhancement and spin polarization switch of the manganese phthalocyanine molecule on an IrMn(100) surface

    SciTech Connect

    Sun, X.; Wang, B.; Pratt, A.; Yamauchi, Y.

    2014-07-21

    The geometric, electronic, and magnetic structures of a manganese phthalocyanine (MnPc) molecule on an antiferromagnetic IrMn(100) surface are studied by density functional theory calculations. Two kinds of orientation of the adsorbed MnPc molecule are predicted to coexist due to molecular self-assembly on the surface—a top-site geometry with the Mn–N bonds aligned along the 〈100〉 direction, and a hollow-site orientation in which the Mn–N bonds are parallel to the 〈110〉 direction. The MnPc molecule is antiferromagnetically coupled to the substrate at the top site with a slight reduction in the magnetic moment of the Mn atom of the MnPc molecule (Mn{sub mol}). In contrast, the magnetic moment of the Mn{sub mol} is enhanced to 4.28 μB at the hollow site, a value larger than that in the free MnPc molecule (3.51 μB). Molecular distortion induced by adsorption is revealed to be responsible for the enhancement of the magnetic moment. Furthermore, the spin polarization of the Mn{sub mol} atom at around the Fermi level is found to change from negative to positive through an elongation of the Mn–N bonds of the MnPc. We propose that a reversible switch of the low/high magnetic moment and negative/positive spin polarization might be realized through some mechanical engineering methods.

  5. Measurement of a false electric dipole moment signal from 199Hg atoms exposed to an inhomogeneous magnetic field

    NASA Astrophysics Data System (ADS)

    Afach, S.; Baker, C. A.; Ban, G.; Bison, G.; Bodek, K.; Chowdhuri, Z.; Daum, M.; Fertl, M.; Franke, B.; Geltenbort, P.; Green, K.; van der Grinten, M. G. D.; Grujic, Z.; Harris, P. G.; Heil, W.; Hélaine, V.; Henneck, R.; Horras, M.; Iaydjiev, P.; Ivanov, S. N.; Kasprzak, M.; Kermaïdic, Y.; Kirch, K.; Knowles, P.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Lemière, Y.; Mtchedlishvili, A.; Naviliat-Cuncic, O.; Pendlebury, J. M.; Piegsa, F. M.; Pignol, G.; Prashant, P. N.; Quéméner, G.; Rebreyend, D.; Ries, D.; Roccia, S.; Schmidt-Wellenburg, P.; Severijns, N.; Weis, A.; Wursten, E.; Wyszynski, G.; Zejma, J.; Zenner, J.; Zsigmond, G.

    2015-10-01

    We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for 199Hg atoms contained in a volume permeated with aligned magnetic and electric fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.

  6. Itinerant and localized magnetic moments in ferrimagnetic Mn{sub 2}CoGa thin films identified with x-ray magnetic linear dichroism: experiment and ab initio theory

    SciTech Connect

    Meinert, M.; Schmalhorst, J; Klewe, C.; Reiss, G.; Arenholz, E.; Bohnert, T.; Nielsch, K.

    2011-08-08

    Epitaxial thin films of the half-metallic X{sub a}-compound Mn{sub 2}CoGa (Hg{sub 2}CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality lms with a bulk magnetization of 1.95(5) {mu}{sub }B per unit cell were obtained. The average Mn magnetic moment and the Co moment are parallel, in agreement with theory. The x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory and reveal the antiparallel alignment of the two inequivalent Mn moments. X-ray magnetic linear dichroism allows to distinguish between itinerant and localized Mn moments. It is shown that one of the two Mn moments has localized character, whereas the other Mn moment and the Co moment are itinerant.

  7. Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field

    SciTech Connect

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

    In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.

  8. Anomalous magnetic moment contributions to NN bremsstrahlung in the soft-photon approximation

    SciTech Connect

    Gibson, B.F.; Penninga, T.D.; Timmermans, R.G.E.; Liou, M.K.

    2005-05-06

    The soft photon approximation (SPA), which is relativistic and based upon a fundamental theorem for photon emission, is applied to explore two separate nucleon-nucleon bremsstrahlung (NN{gamma}) processes: pp{gamma} and np{gamma}. They are examined together in an effort to understand the mechanism which governs photon emission from these basic two-nucleon systems. In this investigation we focus upon the effect of the anomalous magnetic moments of the proton ({kappa}p) and the neutron ({kappa}n). In our SPA calculation we use the standard Low amplitude M{sub {mu}}{sup Low} as derived by Nyman plus the more recently developed amplitude M{sub {mu}}{sup TuTts}, referred to as the two-u-two-t special (TuTts) amplitude. The amplitude M{sub {mu}}{sup TuTts} is identical to the amplitude M{sub {mu}}{sup Low} through order K0 in the soft-photon expansion. However, M{sub {mu}}{sup TuTts} includes an additional term M{sub {mu}}{sup (3)}(K{sup 1}; {kappa}) (plus higher order terms). The term M{sub {mu}}{sup (3)}(K{sup 1}; {kappa}) is of order K1 in the soft-photon expansion and it is a function of {kappa}p and {kappa}n. Using the amplitudes M{sub {mu}}{sup TuTts} and M{sub {mu}}{sup Low}, we have calculated pp{gamma} and np{gamma} cross sections as a function of photon angle {psi}{gamma} with and without contributions from {kappa}p and {kappa}n. Comparison with available pp{gamma} data has been made; in particular, the contribution from M{sub {mu}}{sup (3)}(K{sup 1}; {kappa}) has been investigated. Results will be presented and discussed which relate to the following: (i) The anomalous magnetic moment effect is significant in pp{gamma}; however, it is small in np{gamma}. That is, the two amplitudes M{sub {mu}}{sup TuTts} and M{sub {mu}}{sup Low} yield very similar np{gamma} cross sections, but they predict very different pp{gamma} cross sections. (ii) M{sub {mu}}{sup TuTts} appears to provide a better SPA than M{sub {mu}}{sup Low} in the case of pp{gamma}. Because {kappa

  9. Predictions for Uranus from a radiometric Bode's law. [planetary magnetic moment estimated from radio emission flux density

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Kaiser, M. L.

    1984-01-01

    Determinations by spacecraft of the low-frequency radio spectra and radiation beam geometry of the magnetospheres of earth, Jupiter, and Saturn now permit a reliable assessment of the overall efficiency of the solar wind in stimulating intense, nonthermal radio bursts from these magnetospheres. It is found that earlier estimates of how magnetospheric radio output scales with the solar wind energy input must be greatly revised, with the result that, while the efficiency is much lower than previously thought, it is remarkably uniform from planet to planet. A 'radimetric Bode's law' is formulated from which a planet's magnetic moment can be estimated from its radio emission output. This law is applied to estimate the low-frequency radio power likely to be measured for Uranus by Voyager 2. It is shown how measurements of Uranus's radio flux can be used to estimate the planetary magnetic moment and solar wind stand-off distance before the in situ measurements.

  10. Magnetic moment and lifetime measurements of Coulomb-excited states in Cd106

    DOE PAGES

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K. -H.; Torres, D. A.; Robinson, S. J. Q.; Sharon, Y. Y.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; et al

    2016-09-06

    The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. As a result, the g factorsmore » of the 2+1 and 4+1 states in 106Cd were measured to be g(2+1) = +0.398(22) and g(4+1) = +0.23(5). A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ(106Cd; 2+1) = 7.0(3) ps and τ(106Cd; 4+1) = 2.5(2) ps. The mean life τ(106Cd; 2+2) = 0.28(2) ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ(106Cd; 4+3) = 1.1(1) ps and τ(106Cd; 3–1) = 0.16(1) ps were determined for the first time. In conclusion, the newly measured g(4+1) of 106Cd is found to be only 59% of the g(2+1). This difference cannot be explained by either shell-model or collective-model calculations.« less

  11. Magnetic moment and lifetime measurements of Coulomb-excited states in 106Cd

    NASA Astrophysics Data System (ADS)

    Benczer-Koller, N.; Kumbartzki, G. J.; Speidel, K.-H.; Torres, D. A.; Robinson, S. J. Q.; Sharon, Y. Y.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bernstein, L. A.; Bevins, J. E.; Crawford, H. L.; Guevara, Z. E.; Hurst, A. M.; Kirsch, L.; Laplace, T. A.; Lo, A.; Matthews, E. F.; Mayers, I.; Phair, L. W.; Ramirez, F.; Wiens, A.

    2016-09-01

    Background: The Cd isotopes are well studied, but experimental data for the rare isotopes are sparse. At energies above the Coulomb barrier, higher states become accessible. Purpose: Remeasure and supplement existing lifetimes and magnetic moments of low-lying states in 106Cd. Methods: In an inverse kinematics reaction, a 106Cd beam impinging on a 12C target was used to Coulomb excite the projectiles. The high recoil velocities provide a unique opportunity to measure g factors with the transient-field technique and to determine lifetimes from lineshapes by using the Doppler-shift-attenuation method. Large-scale shell-model calculations were carried out for 106Cd. Results: The g factors of the 21+ and 41+ states in 106Cd were measured to be g (21+)=+0.398 (22 ) and g (41+)=+0.23 (5 ) . A lineshape analysis yielded lifetimes in disagreement with published values. The new results are τ (106Cd;21+)=7.0 (3 )ps and τ (106Cd;41+)=2.5 (2 )ps . The mean life τ (106Cd;22+)=0.28 (2 )ps was determined from the fully-Doppler-shifted γ line. Mean lives of τ (106Cd;43+)=1.1 (1 )ps and τ (106Cd;31-)=0.16 (1 )ps were determined for the first time. Conclusions: The newly measured g (41+) of 106Cd is found to be only 59% of the g (21+) . This difference cannot be explained by either shell-model or collective-model calculations.

  12. Evolution of calculations of the virtual dipole moment of the Earth for reconstructing the oceanic inversion magnetic layer's parameters

    NASA Astrophysics Data System (ADS)

    Schreider, A. A.; Ignatova, A. A.; Schreider, Al. A.; Sajneva, A. E.; Varga, P.; Denis, C.

    2016-05-01

    The VDM (virtual dipole moment) is one of the most significant characteristics describing the behavior of the time evolution of the terrestrial magnetic field. However, we have revealed that the formulas with which VDM calculations are performed often do not coincide with each other in various literature sources. Hence, results are obtained from these calculations that cannot be identical. Their correctness is verified by comparing the dimension and obtained results with the known value of the VDM for our time.

  13. Magnetic moment for the negative parity Λ → Σ0 transition in light cone QCD sum rules

    NASA Astrophysics Data System (ADS)

    Aliev, T. M.; Savcı, M.

    2016-07-01

    The magnetic moment of the Λ →Σ0 transition between negative parity baryons is calculated in framework of the QCD sum rules approach by using the general form of the interpolating currents. The pollution arising from the positive-to-positive, and positive-to-negative parity baryons is eliminated by constructing the sum rules for different Lorentz structures. A comparison of our result with the predictions of the results of other approaches for the positive parity baryons is presented.

  14. Production polarization and magnetic moment of Ξ¯+ antihyperons produced by 800-GeV/c protons

    NASA Astrophysics Data System (ADS)

    Ho, P. M.; Longo, M. J.; Nguyen, A.; Luk, K. B.; James, C.; Rameika, R.; Duryea, J.; Guglielmo, G.; Heller, K.; Johns, K.; Diehl, H. T.; Teige, S.; Thomson, G. B.; Zou, Y.

    1990-10-01

    The polarization of Ξ¯ + hyperons produced by 800-GeV/c protons in the inclusive reaction p+Be-->Ξ¯ ++X has been measured. The average polarization of the Ξ¯ +, at a mean xF=0.39 and pt=0.76 GeV/c, is -0.097+/-0.012+/-0.009. The magnetic moment of the Ξ¯ + is 0.657+/-0.028+/-0.020 nuclear magneton.

  15. Effects of shape and edge-passivation on magnetic moments in graphene nanomesh by first-principles investigation

    NASA Astrophysics Data System (ADS)

    Yang, Hongxin; Chshiev, Mairbek; Spintec Team

    2011-03-01

    First-principles calculations of electronic and magnetic properties of pure and H-terminated graphene nanomesh (GNM) are presented. We found stable antiferromagnetic and non-magnetic ground state for GNM with balanced zigzag and armchair-type edge structures, respectively. At the same time, a band gap opening in the balanced zigzag edge GNMs which can reach up to 0.40 eV is also found. Interestingly, GNM with unbalanced edge structure shows stable ferrimagnetic state giving rise to a net moment up to 4 Bohr magnetons per unit cell, and the exchange energy between ferrimagnetic state and paramagnetic state is larger than 1 eV per unit cell providing potential for high Curie temperature in this material. Furthermore, we found that the ground states for H-terminated GNM strongly depend on the hole symmetry: large spin polarization ground state is found for GNMs with triangle and pentagon hole shapes, while for GNMs with parallelogram and hexagon shaped holes the ground states are paramagnetic. Finally, we found that the magnetization of the GNM structure is strongly affected by the hole size: the larger hole size attains large moments, while small one may even kill all the moments.

  16. Ultrafast dynamics of localized magnetic moments in the unconventional Mott insulator Sr2IrO4.

    PubMed

    Krupin, O; Dakovski, G L; Kim, B J; Kim, J W; Kim, Jungho; Mishra, S; Chuang, Yi-De; Serrao, C R; Lee, W-S; Schlotter, W F; Minitti, M P; Zhu, D; Fritz, D; Chollet, M; Ramesh, R; Molodtsov, S L; Turner, J J

    2016-08-17

    We report a time-resolved study of the ultrafast dynamics of the magnetic moments formed by the [Formula: see text] states in Sr2IrO4 by directly probing the localized iridium 5d magnetic state through resonant x-ray diffraction. Using optical pump-hard x-ray probe measurements, two relaxation time scales were determined: a fast fluence-independent relaxation is found to take place on a time scale of 1.5 ps, followed by a slower relaxation on a time scale of 500 ps-1.5 ns. PMID:27310659

  17. Ultrafast dynamics of localized magnetic moments in the unconventional Mott insulator Sr2IrO4

    NASA Astrophysics Data System (ADS)

    Krupin, O.; Dakovski, G. L.; Kim, B. J.; Kim, J. W.; Kim, Jungho; Mishra, S.; Chuang, Yi-De; Serrao, C. R.; Lee, W.-S.; Schlotter, W. F.; Minitti, M. P.; Zhu, D.; Fritz, D.; Chollet, M.; Ramesh, R.; Molodtsov, S. L.; Turner, J. J.

    2016-08-01

    We report a time-resolved study of the ultrafast dynamics of the magnetic moments formed by the {{J}\\text{eff}}=1/2 states in Sr2IrO4 by directly probing the localized iridium 5d magnetic state through resonant x-ray diffraction. Using optical pump–hard x-ray probe measurements, two relaxation time scales were determined: a fast fluence-independent relaxation is found to take place on a time scale of 1.5 ps, followed by a slower relaxation on a time scale of 500 ps–1.5 ns.

  18. Using magnetic circular dichroism for the study of the magnetization and the magnetic moments of atoms in Nd(3)Fe(27.5)Ti(1.5).

    PubMed

    Sarafidis, C; Wilhelm, F; Rogalev, A; Gjoka, M; Kalogirou, O

    2009-06-10

    An element-specific study of the Nd(3)Fe(27.5)Ti(1.5) compound using the hard x-ray magnetic circular dichroism (XMCD) technique is presented. The Nd L(2) and L(3) edge XMCD, as well as the Fe K edge XMCD, were measured in a magnetically oriented sample, parallel and perpendicular to its alignment direction. The XMCD spectra were recorded at three different temperatures, above, below and in between the characteristic peaks that the specific compound presents in AC susceptibility measurements. By probing the Nd L edges and the Fe K edge XMCD, we found that the dipolar R(5d)-Fe(3d) exchange interaction behaves differently with temperature change than the Fe-Fe magnetic interaction. Those differences appear to be in the vicinity of the AC susceptibility characteristic peaks. An XMCD signal was recorded at the Ti K edge, revealing a small orbital polarization due to the hybridization with Fe atomic states. This demonstrates the existence of a small finite magnetic moment in Ti atoms. PMID:21825598

  19. Trapping neutral particles endowed with a magnetic moment by an electromagnetic wave carrying orbital angular momentum: Semiclassical theory

    NASA Astrophysics Data System (ADS)

    Bialynicki-Birula, Iwo; RadoŻycki, Tomasz

    2016-06-01

    The motion of a neutral atom endowed with a magnetic moment interacting with the magnetic field is determined from the Ehrenfest-like equations of motion. These equations for the average values of the translational and spin degrees of freedom are derived from the Schrödinger-Pauli wave equation, and they form a set of nine coupled nonlinear evolution equations. The numerical and analytic solutions of these equations are obtained for the combination of the rotating magnetic field of a wave carrying orbital angular momentum and a static magnetic field. The running wave traps the atom only in the transverse direction, while the standing wave traps the atom also in the direction of the beam.

  20. Local magnetic moment formation at 119Sn Mössbauer impurity in RCo2 (R=Gd,Tb,Dy,Ho,Er) Laves phase compounds

    NASA Astrophysics Data System (ADS)

    de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

    2008-04-01

    In this work, we theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a Mösbauer Sn119 impurity diluted at the R site (R=Gd,Tb,Dy,Ho,Er) of the cubic Laves phase intermetallic compounds RCo2. One considers that the magnetic hyperfine fields have two contributions, (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24, 1601 (1963)] model, and (ii) the contribution from the induced magnetic moments arising from the Co neighboring sites. Our calculated self-consistent total magnetic hyperfine fields are in a good agreement with recent experimental data.

  1. Optical control of Magnetic Feshbach Resonances using Closed Channel EIT

    NASA Astrophysics Data System (ADS)

    Jagannathan, Arunkumar; Arunkumar, Nithya; Joseph, James; Thomas, John

    2016-05-01

    Optical techniques can provide rapid temporal control and high-resolution spatial control of interactions in cold gases enabling the study of non-equilibrium strongly interacting Fermi gases. We use electromagnetically induced transparency (EIT) in the closed channel to control magnetic Feshbach resonances in an optically-trapped mixture of the two lowest hyperfine states of a 6 Li Fermi gas. In our experiments, the narrow Feshbach resonance is tuned by up to 3 G. For the broad resonance, the spontaneous lifetime is increased to 0.4 s at the dark state resonance, compared to 0.5 ms for single field tuning. We present a new model of light-induced loss spectra, employing continuum-dressed basis states, that agrees in shape and magnitude with loss measurements for both broad and narrow resonances. Using this model, we predict the trade-off between tunability and loss for the broad resonance in 6 Li, showing that our two-field method substantially reduces the two-body loss rate compared to single field methods for same tuning range. This research is supported by AFOSR, NSF, ARO, and DOE.

  2. Magnetic Dipole Moment Measurements of Picosecond States in Even and Odd Heavy Nuclei

    NASA Astrophysics Data System (ADS)

    Ballon, Douglas Jude

    The perturbed angular correlation and transient field technique is used to measure the precession of nuclear magnetic moments of low lying excited states in isotopes of silver, neodymium, samarium, and gadolinium. The precession measurements are used to explore three main areas of study. First, from the measurements made on ('150)Sm traversing gadolinium targets, the temperature dependence of the transient hyperfine field is deduced at ('150)Sm nuclei traveling at 2 < v/v(,0) < 4. These are compared with similar measurements made using iron targets. Second, the deduced values of the g-factors of the 2(,1)('+) states in even neodymium, samarium and gadolinium isotopes are discussed in connection with a possible proton shell closure at Z = 64. Third, the deduced values of the g-factors of the 3/2(,1)('-) and 5/2(,1)('-) states of ('107,109)Ag are compared to various theoretical predictions in order to explore any simple relationships that may exist between these states and the first 2(,1)('+) states of neighboring even-even nuclei. The following is a list of g-factors that were measured during the course of this work: (UNFORMATTED TABLE FOLLOWS). g(('107)Ag, 3/2(,1)('-)) = 0.607 (119). g(('109)Ag, 3/2(,1)('-)) = 0.661 (105). g(('107)Ag, 5/2(,1)('-)) = 0.409 (66). g(('109)Ag, 5/2(,1)('-)) = 0.287 (57). g(('144)Nd, 2(,1)('+)) = 0.166 (41). g(('146)Nd, 2(,1)('+)) = 0.312 (49). g(('148)Nd, 2(,1)('+)) = 0.411 (42). g(('150)Nd,2(,1)('+)) = 0.418 (38). g(('148)Sm, 2(,1)('+)) = 0.301 (33). g(('150)Sm, 2(,1)('+)) = 0.381 (27). g(('152)Gd, 2(,1)('+)) = 0.444 (40). (TABLE ENDS). The results of the temperature dependence experiment show deviations from an earlier measurement made using thulium in iron. The g-factors measured in the lighter isotopes of neodymium and samarium are significantly below the collective Z/A value. Fair agreement with the data can be obtained if proton shell closure is assumed at Z = 64 for N < 88. The measured g-factors in the silver isotopes

  3. Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute

    SciTech Connect

    Afach, S.; Fertl, M.; Franke, B. E-mail: bernhard.lauss@psi.ch; Kirch, K.; Bison, G.; Burri, F.; Chowdhuri, Z.; Daum, M.; Henneck, R.; Lauss, B. E-mail: bernhard.lauss@psi.ch; Meier, M.; Schmidt-Wellenburg, P.; Zsigmond, G.; Bodek, K.; Zejma, J.; Grujic, Z.; Kasprzak, M.; Weis, A.; Hélaine, V.; Koch, H.-C.; and others

    2014-08-28

    The Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5 m × 2.5 m × 3 m, disturbances of the magnetic field are attenuated by factors of 5–50 at a bandwidth from 10{sup −3} Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the neutron electric dipole moment measurement. These shielding factors apply to random environmental noise from arbitrary sources. This is achieved via a proportional-integral feedback stabilization system that includes a regularized pseudoinverse matrix of proportionality factors which correlates magnetic field changes at all sensor positions to current changes in the SFC coils.

  4. Monolayer magnetism of 3d transition metals in Ag, Au, Pd, and Pt hosts: Systematics of local moment variation

    NASA Astrophysics Data System (ADS)

    McHenry, M. E.; MacLaren, J. M.; Clougherty, D. P.

    1991-11-01

    Electronic and magnetic properties of T/Aun, T/Agn (T=Cr, Mn, Fe, Co, and Ni), Fe/Pdn and Fe/Ptn multilayers and sandwiches have been computed using the layer Korringa-Kohn-Rostoker (LKKR) band-structure technique. Enhanced (as compared with bulk) 2D T magnetism is observed in all Cr, Mn, and Fe/host configurations, consistent with weak coupling between Cr, Mn, and Fe d bands and those of the noble metal (NM) hosts and consequently d bandwidths which are exceeded by the exchange splitting. Fe and Cr moments vary systematically with the number of mediating Ag or Au planes and the Fermi energy of the system. These systematics are explained by considering the variation of the Fermi energy (EF) with composition as well as constraints of charge neutrality and strong (single-band) ferromagnetism. For Fe in Pt and Pd hosts, d-d hybridization leads to a nearly invariant Fe moment as a function of the number of mediating Pd or Pt planes but with large induced moments on the host.

  5. Disorder dependence of the magnetic moment of the half-metallic ferromagnet NiMnSb from first principles

    SciTech Connect

    Orgassa, D.; Fujiwara, H.; Schulthess, T. C.; Butler, W. H.

    2000-05-01

    Using half-metallic ferromagnets in spin-dependent devices, like spin valves and ferromagnetic tunnel junctions, is expected to increase the device performance. However, using the half-metallic ferromagnet NiMnSb in such devices led to much less than ideal results. One of the possible sources for this behavior is atomic disorder. First-principles calculations of the influence of atomic disorder on the electronic structure of NiMnSb underline the sensitivity of half-metallic properties in NiMnSb to atomic disorder. In this article, we report on the disorder dependence of the total magnetic moment calculated by applying the layer Korringa-Kohn-Rostoker method in conjunction with the coherent potential approximation. We consider the following types of disorder: (1) intermixing of Ni and Mn, (2) partial occupancy of a normally vacant lattice site by Ni and Mn, and (3) partial occupancy of this site by Mn and Sb. In all cases the composition is kept stoichiometric. All three types of disorder decrease the moment monotonically with increasing disorder levels. For the experimentally seen disorder of 5% Mn and 5% Sb on the normally vacant lattice site, the total moment is decreased by 4.1%. The results suggest that precise measurement of the saturation magnetization of NiMnSb thin films can give information on the disorder. (c) 2000 American Institute of Physics.

  6. Orbital and spin moments of 5 to 11 nm Fe{sub 3}O{sub 4} nanoparticles measured via x-ray magnetic circular dichroism

    SciTech Connect

    Cai, Y. P.; Chesnel, K. Trevino, M.; Westover, A.; Turley, S.; Harrison, R. G.; Hancock, J. M.; Scherz, A.; Reid, A.; Wu, B.; Graves, C.; Wang, T.; Liu, T.; Dürr, H.

    2014-05-07

    The orbital and spin contributions to the magnetic moment of Fe in Fe{sub 3}O{sub 4} nanoparticles were measured using X-ray magnetic circular dichroism (XMCD). Nanoparticles of different sizes, ranging from 5 to 11 nm, were fabricated via organic methods and their magnetic behavior was characterized by vibrating sample magnetometry (VSM). An XMCD signal was measured for three different samples at 300 K and 80 K. The extracted values for the orbital and spin contributions to the magnetic moment showed a quenching of the orbital moment and a large spin moment. The calculated spin moments appear somewhat reduced compared to the value expected for bulk Fe{sub 3}O{sub 4}. The spin moments measured at 80 K are larger than at 300 K for all the samples, revealing significant thermal fluctuations effects in the nanoparticle assemblies. The measured spin moment is reduced for the smallest nanoparticles, suggesting that the magnetic properties of Fe{sub 3}O{sub 4} nanoparticles could be altered when their size reaches a few nanometers.

  7. Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.

    PubMed

    Jaouen, M; Bugnet, M; Jaouen, N; Ohresser, P; Mauchamp, V; Cabioc'h, T; Rogalev, A

    2014-04-30

    From x-ray magnetic circular dichroism experiments performed at low temperature on Cr2AlC and Cr2GeC thin films, it is evidenced that Cr atoms carry a net magnetic moment in these ternary phases. It is shown that the Cr magnetization of the Al-based compound nearly vanished at 100 K in agreement with what has been recently observed on bulk. X-ray linear dichroism measurements performed at various angles of incidence and temperatures clearly demonstrate the existence of a charge ordering along the c axis of the structure of Cr2AlC. All these experimental observations support, in part, theoretical calculations claiming that Cr dd correlations have to be considered to correctly describe the structure and properties of these Cr-based ternary phases. PMID:24721758

  8. Characterization of the magnetic moment distribution in low-concentration solutions of iron oxide nanoparticles by a high-T{sub c} superconducting quantum interference device magnetometer

    SciTech Connect

    Saari, M. M. Sakai, K.; Kiwa, T.; Tsukada, K.; Sasayama, T.; Yoshida, T.

    2015-05-07

    We developed a highly sensitive AC/DC magnetometer using a high-temperature superconductor superconducting quantum interference device for the evaluation of magnetic nanoparticles in solutions. Using the developed system, we investigated the distribution of magnetic moments of iron oxide multi-core particles of 100 nm at various iron concentrations that are lower than 96 μg/ml by analyzing the measured magnetization curves. Singular value decomposition and non-regularized non-negative least-squares methods were used during the reconstruction of the distribution. Similar distributions were obtained for all concentrations, and the iron concentration could be determined from the measured magnetization curves. The measured harmonics upon the excitation of AC and DC magnetic fields curves agreed well with the harmonics simulated based on the reconstructed magnetization curves, implying that the magnetization curves of magnetic nanoparticles were successfully obtained as we will show in the article. We compared the magnetization curves between multi-core particles of 100 nm and 130 nm, composed of 12-nm iron oxide nanoparticles. A distinctive magnetic property between the 100 nm and 130 nm particles in low-concentration solutions was successfully characterized. The distribution characteristic of magnetic moments suggests that the net magnetic moment in a multi-core particle is affected by the size of the magnetic cores and their degree of aggregation. Exploration of magnetic properties with high sensitivity can be expected using the developed system.

  9. Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism

    SciTech Connect

    Jamer, M. E.; Assaf, B. A.; Sterbinsky, G. E.; Arena, D. A.; Heiman, D.

    2014-12-05

    Spin gapless semiconductors are known to be strongly affected by structural disorder when grown epitaxially as thin films. The magnetic properties of Mn2CoAl thin films grown on GaAs (001) substrates are investigated here as a function of annealing. This study investigates the atomic-specific magnetic moments of Mn and Co atoms measured through X-ray magnetic circular dichroism as a function of annealing and the consequent structural ordering. Results indicate that the structural distortion mainly affects the Mn atoms as seen by the reduction of the magnetic moment from its predicted value.

  10. Microscopic description of ground state magnetic moment and low-lying magnetic dipole excitations in heavy odd-mass 181Ta nucleus

    NASA Astrophysics Data System (ADS)

    Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar

    2016-07-01

    The ground state magnetic moments and the low-lying magnetic dipole (Ml) transitions from the ground to excited states in heavy deformed odd-mass 181Ta have been microscopically investigated on the basis of the quasiparticle-phonon nuclear model (QPNM). The problem of the spurious state mixing in M1 excitations is overcome by a restoration method allowing a self-consistent determination of the separable effective restoration forces. Due to the self-consistency of the method, these effective forces contain no arbitrary parameters. The results of calculations are compared with the available experimental data, the agreement being reasonably satisfactory.

  11. Limit on the muon neutrino magnetic moment and a measurement of the CCPIP to CCQE cross section ratio

    SciTech Connect

    Ouedraogo, Serge Aristide

    2008-12-01

    A search for the muon neutrino magnetic moment was conducted using the Mini-BooNE low energy neutrino data. The analysis was performed by analyzing the elastic scattering interactions of muon neutrinos on electrons. The analysis looked for an excess of elastic scattering events above the Standard Model prediction from which a limit on the neutrino magnetic could be set. In this thesis, we report an excess of 15.3 ± 6.6(stat)±4.1(syst) vμe events above the expected background. At 90% C.L., we derived a limit on the muon neutrino magnetic moment of 12.7 x 10-10 μB. The other analysis reported in this thesis is a measurement of charged current single pion production (CCπ+) to charged current quasi elastic (CCQE) interactions cross sections ratio. This measurement was performed with two different fitting algorithms and the results from both fitters are consistent with each other.

  12. Anomalous tensor magnetic moments and form factors of the proton in the self-consistent chiral quark-soliton model

    SciTech Connect

    Ledwig, Tim; Silva, Antonio

    2010-09-01

    We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/N{sub c} rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: {kappa}{sub T}{sup u}=3.56 and {kappa}{sub T}{sup d}=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be {kappa}{sub T}{sup s}=0.2{approx}-0.2, that is compatible with zero. We also calculate the corresponding form factors {kappa}{sub T}{sup q}(Q{sup 2}) up to a momentum transfer Q{sup 2{<=}}1 GeV{sup 2} at a renormalization scale of 0.36 GeV{sup 2}.

  13. Out-of-Plane Magnetic Moment and Lattice Distortion in Sputtered Ge Added Fe3O4 Thin Film.

    PubMed

    Watanabe, Masato; Abe, Seishi

    2016-03-01

    Fe3O4 has been known to have attractive physical properties for spintronic applications such as half-metallicity, however, its complicated magnetism has yet to be elucidated fully. We investigated the sputtered polycrystalline Fe3O4 thin film in which Ge was added for stabilization of the spinal structure. From X-ray photoelectron and Raman spectroscopies, major part of added Ge is found to be quadrivalent and considered to be incorporated in the spinel structure. Out-of-plane alignment of the local moment was confirmed by conversion electron Mössbauer spectroscopy and magnetization measurements with an applied field up to 70 kOe also support it. The Pawley refinement of the X-ray diffraction profile with a series of possible space groups in the spinel structure suggests that the crystal symmetry is reduced from cubic to tetragonal or orthorhombic spinels with (100) or (010) strains up to -0.231%. The uniaxial anisotropy constants K(u) for the tetragonally distorted cases estimated from the evaluated strains and the ab-initio calculation were found to be around 1.05 x 10(6) erg/cm3. We consider that the magnetic anisotropy induced by the lattice distortion contributes to the out-of-plane alignment of local moments in addition to the previously reported effect by the exchange coupling across crystallographic defects of the antiphase boundaries. PMID:27455663

  14. Multiple degree-of-freedom force and moment measurement for static propulsion testing using magnetic suspension technology

    NASA Technical Reports Server (NTRS)

    Stuart, Keith; Bartosh, Blake

    1993-01-01

    Innovative Information Systems (IIS), Inc. is in the process of designing and fabricating a high bandwidth force and moment measuring device (i.e. the Magnetic Thruster Test Stand). This device will use active magnetic suspension to allow direct measurements of the forces and torques generated by the rocket engines of the missile under test. The principle of operation of the Magnetic Thruster Test Stand (MTTS) is based on the ability to perform very precise, high bandwidth force and position measurements on an object suspended in a magnetic field. This ability exists due to the fact that the digital servo control mechanism that performs the magnetic suspension uses high bandwidth (10 kHz) position data (via an eddy-current proximity sensor) to determine the amount of force required to maintain stable suspension at a particular point. This force is converted into required electromagnet coil current, which is then output to a current amplifier driving the coils. A discussion of how the coil current and magnetic gap distance (the distance between the electromagnet and the object being suspended) is used to determine the forces being applied from the suspended assembly is presented.

  15. Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field

    PubMed Central

    2014-01-01

    Co-doped SnO2 thin films were grown by sputtering technique on SiO2/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (HTT) were performed in vacuum at 600°C for 20 min. HTT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μB/Co at. is obtained when HTT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co+2 from 0.06 to 0.42 μB/Co at. for the sample on which HTT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co+2 ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO2 nanocrystals, which is proposed to be the easy magnetization axis. PMID:25489286

  16. Methods for Computing Accurate Atomic Spin Moments for Collinear and Noncollinear Magnetism in Periodic and Nonperiodic Materials.

    PubMed

    Manz, Thomas A; Sholl, David S

    2011-12-13

    The partitioning of electron spin density among atoms in a material gives atomic spin moments (ASMs), which are important for understanding magnetic properties. We compare ASMs computed using different population analysis methods and introduce a method for computing density derived electrostatic and chemical (DDEC) ASMs. Bader and DDEC ASMs can be computed for periodic and nonperiodic materials with either collinear or noncollinear magnetism, while natural population analysis (NPA) ASMs can be computed for nonperiodic materials with collinear magnetism. Our results show Bader, DDEC, and (where applicable) NPA methods give similar ASMs, but different net atomic charges. Because they are optimized to reproduce both the magnetic field and the chemical states of atoms in a material, DDEC ASMs are especially suitable for constructing interaction potentials for atomistic simulations. We describe the computation of accurate ASMs for (a) a variety of systems using collinear and noncollinear spin DFT, (b) highly correlated materials (e.g., magnetite) using DFT+U, and (c) various spin states of ozone using coupled cluster expansions. The computed ASMs are in good agreement with available experimental results for a variety of periodic and nonperiodic materials. Examples considered include the antiferromagnetic metal organic framework Cu3(BTC)2, several ozone spin states, mono- and binuclear transition metal complexes, ferri- and ferro-magnetic solids (e.g., Fe3O4, Fe3Si), and simple molecular systems. We briefly discuss the theory of exchange-correlation functionals for studying noncollinear magnetism. A method for finding the ground state of systems with highly noncollinear magnetism is introduced. We use these methods to study the spin-orbit coupling potential energy surface of the single molecule magnet Fe4C40H52N4O12, which has highly noncollinear magnetism, and find that it contains unusual features that give a new interpretation to experimental data.

  17. From pure superparamagnetic regime to glass collective state of magnetic moments in γ-Fe2O3 nanoparticle assemblies

    NASA Astrophysics Data System (ADS)

    Dormann, J. L.; Cherkaoui, R.; Spinu, L.; Noguès, M.; Lucari, F.; D'Orazio, F.; Fiorani, D.; Garcia, A.; Tronc, E.; Jolivet, J. P.

    1998-08-01

    Studies of the frequency dependence of the temperature of the AC susceptibility peak, of the thermal variation of the nonlinear DC susceptibility, and of ageing effects on the magnetization relaxation in γ-Fe2O3 4.7 nm nanoparticle assemblies with interparticle interactions of varying strength, give evidence of three magnetic regimes: pure superparamagnetic, superparamagnetic modified by the interactions, and collective. The properties of the latter regime, called glass collective state, are close to those of a canonical spin glass.

  18. Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

    SciTech Connect

    Thersleff, Thomas; Rusz, Jan; Rubino, Stefano; Hjörvarsson, Björgvin; Ito, Yasuo; J. Zaluzec, Nestor; Leifer, Klaus

    2015-08-17

    Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magnetic orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features.

  19. Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

    PubMed Central

    Thersleff, Thomas; Rusz, Jan; Rubino, Stefano; Hjörvarsson, Björgvin; Ito, Yasuo; J. Zaluzec, Nestor; Leifer, Klaus

    2015-01-01

    Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magnetic orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features. PMID:26278134

  20. Low moment NiCr radio frequency magnetic films for multiferroic heterostructures with strong magnetoelectric coupling

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Beguhn, S.; Lou, J.; Rand, S.; Li, M.; Yang, X.; Li, S. D.; Liu, M.; Sun, N. X.

    2012-05-01

    Magnetic/piezoelectric multiferroic heterostructures with a magnetic thin film on a piezoelectric slab provides a great opportunity to achieve a strong converse magnetoelectric coupling with great potential for voltage tunable magnetic devices. Efforts have been made in developing highly magnetostrictive RF magnetic materials with low magnetization using magnetic/piezoelectric heterostructures to generate large electric-field induced effective magnetic fields. In this work, we report on NiCr films having low magnetization and relatively large magnetostriction. Strong converse magnetoelectric coupling and large electric field tunable ferromagnetic resonance (FMR) bandwidths are achieved in layered NiCr/lead zirconate titanate (PZT) and NiCr/lead zinc niobate lead titanate (PZN-PT) multiferroic heterostructures. A large electric field induced effective magnetic field of 260 Oe for NiCr/PZT and 756 Oe for NiCr/PZN-PT was observed, corresponding to a giant magnetoelectric coupling coefficient of 13 Oe cm/kV in NiCr/PZT and 75.6 Oe cm/kV in NiCr/PZN-PT multiferroic heterostructures. A high voltage tunable FMR frequency range was observed, with fmax/fmin being 124 and 325% for NiCr/PZT and NiCr/PZN-PT. The strong converse magnetoelectric coupling of NiCr/PZT and NiCr/PZN-PT heterostructures provide great opportunities for electric field tunable RF magnetic devices.

  1. An investigation into force-moment calibration techniques applicable to a magnetic suspension and balance system. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Eskins, Jonathan

    1988-01-01

    The problem of determining the forces and moments acting on a wind tunnel model suspended in a Magnetic Suspension and Balance System is addressed. Two calibration methods were investigated for three types of model cores, i.e., Alnico, Samarium-Cobalt, and a superconducting solenoid. Both methods involve calibrating the currents in the electromagnetic array against known forces and moments. The first is a static calibration method using calibration weights and a system of pulleys. The other method, dynamic calibration, involves oscillating the model and using its inertia to provide calibration forces and moments. Static calibration data, found to produce the most reliable results, is presented for three degrees of freedom at 0, 15, and -10 deg angle of attack. Theoretical calculations are hampered by the inability to represent iron-cored electromagnets. Dynamic calibrations, despite being quicker and easier to perform, are not as accurate as static calibrations. Data for dynamic calibrations at 0 and 15 deg is compared with the relevant static data acquired. Distortion of oscillation traces is cited as a major source of error in dynamic calibrations.

  2. Research developing closed loop roll control for magnetic balance systems

    NASA Technical Reports Server (NTRS)

    Covert, E. E.; Haldeman, C. W.

    1981-01-01

    Computer inputs were interfaced to the magnetic balance outputs to provide computer position control and data acquisition. The use of parameter identification of a means of determining dynamic characteristics was investigated. The thyraton and motor generator power supplies for the pitch and yaw degrees of freedom were repaired. Topics covered include: choice of a method for handling dynamic system data; applications to the magnetic balance; the computer interface; and wind tunnel tests, results, and error analysis.

  3. Correlated oscillations of the magnetic anisotropy energy and orbital moment anisotropy in thin films: The role of quantum well states

    NASA Astrophysics Data System (ADS)

    Sandratskii, L. M.

    2015-10-01

    We report the first-principles study of the correlated behavior of the magnetic anisotropy energy (MAE) and orbital moment anisotropy (OMA) as the functions of the thickness N of the Fe film. The work is motivated by recent experimental studies combining photoemission, x-ray magnetic circular dichroism, and magnetic anisotropy measurements. In agreement with experiment, the correlated oscillations of MAE (N ) and OMA (N ) are obtained that have their origin in the formation of the 3d quantum well states (QWS) confined in the films. The main contribution to the oscillation amplitude comes from the surface layer. This is an interesting feature of the phenomenon consisting in the peculiar dependence of the physical quantities on the thickness of the film. We demonstrate that the band structure of the bulk Fe does not reflect adequately the properties of the 3d QWS in thin films and, therefore, does not provide the basis for understanding the oscillations of MAE (N ) and OMA (N ) . A detailed point-by-point analysis in the two-dimensional (2D) Brillouin zone (BZ) of the film shows that the contribution of the Γ point, contrary to a rather common expectation, does not play an important role in the formation of the oscillations. Instead, the most important contributions come from a broad region of the 2D BZ distant from the center of the BZ. Combining symmetry arguments and direct calculations we show that orbital moments of the electronic states possess nonzero transverse components orthogonal to the direction of the spin magnetization. The account for this feature is crucial in the point-by-point analysis of the OMA. On the basis of the calculations for noncollinear spin configurations we suggest interpretations of two interesting experimental findings: fast temperature decay of the oscillation amplitude in MAE (N ) and unexpectedly strong spin mixing of the initial states of the photoemission process.

  4. Increased magnetic moment induced by lattice expansion from α-Fe to α′-Fe{sub 8}N

    SciTech Connect

    Dirba, Imants Komissinskiy, Philipp; Alff, Lambert; Gutfleisch, Oliver

    2015-05-07

    Buffer-free and epitaxial α-Fe and α′-Fe{sub 8}N{sub x} thin films have been grown by RF magnetron sputtering onto MgO (100) substrates. The film thicknesses were determined with high accuracy by evaluating the Kiessig fringes of X-ray reflectometry measurements allowing a precise volume estimation. A gradual increase of the nitrogen content in the plasma led to an expansion of the iron bcc unit cell along the [001] direction resulting finally in a tetragonal distortion of about 10% corresponding to the formation of α′-Fe{sub 8}N. The α-Fe lattice expansion was accompanied by an increase in magnetic moment to 2.61 ± 0.06μ{sub B} per Fe atom and a considerable increase in anisotropy. These experiments show that—without requiring any additional ordering of the nitrogen atoms—the lattice expansion of α-Fe itself is the origin of the increased magnetic moment in α′-Fe{sub 8}N.

  5. Interface magnetic moments enhancement of FePt-L10/MgO(001): An ab initio study

    NASA Astrophysics Data System (ADS)

    Cuadrado, R.; Chantrell, R. W.

    2014-03-01

    The interface between FePt-L10 and MgO(001) alloys has been studied using density-functional calculations. Because the stacking of the face-centered tetragonal L10 phase is formed by alternating Fe and Pt planes, both the Fe- and Pt-terminated contact layers were studied. Furthermore, due to the large mismatch between the in-plane lattice constants of both systems, we have chosen some common a values for both alloys in order to explore in detail the adsorption energy, the electronic structure, and the interface magnetism. The adsorption energy has been calculated by subtracting the energy of clean FePt and MgO alloys from the total energy. The preferred adsorbed geometric sites for Fe/Pt atoms are when they lie on top of the O species, having a smaller adsorption energy for the remaining positions. We found that expanding the MgO lattice enhances the magnetic moment of the Fe species but the Pt moments remain almost constant.

  6. Quantitative analysis of magnetic spin and orbital moments from an oxidized iron (1 1 0) surface using electron magnetic circular dichroism

    DOE PAGES

    Thersleff, Thomas; Rusz, Jan; Rubino, Stefano; Hjörvarsson, Björgvin; Ito, Yasuo; J. Zaluzec, Nestor; Leifer, Klaus

    2015-08-17

    Understanding the ramifications of reduced crystalline symmetry on magnetic behavior is a critical step in improving our understanding of nanoscale and interfacial magnetism. However, investigations of such effects are often controversial largely due to the challenges inherent in directly correlating nanoscale stoichiometry and structure to magnetic behavior. Here, we describe how to use Transmission Electron Microscope (TEM) to obtain Electron Magnetic Circular Dichroism (EMCD) signals as a function of scattering angle to locally probe the magnetic behavior of thin oxide layers grown on an Fe (1 1 0) surface. Experiments and simulations both reveal a strong dependence of the magneticmore » orbital to spin ratio on its scattering vector in reciprocal space. We exploit this variation to extract the magnetic properties of the oxide cladding layer, showing that it locally may exhibit an enhanced orbital to spin moment ratio. This finding is supported here by both spatially and angularly resolved EMCD measurements, opening up the way for compelling investigations into how magnetic properties are affected by nanoscale features.« less

  7. Itinerant and localized magnetic moments in ferrimagnetic Mn{sub 2}CoGa thin films probed by x-ray magnetic linear dichroism: Experiment and ab initio theory

    SciTech Connect

    Meinert, Markus; Schmalhorst, Jan-Michael; Klewe, Christoph; Reiss, Guenter; Arenholz, Elke; Boehnert, Tim; Nielsch, Kornelius

    2011-10-01

    Epitaxial thin films of the half-metallic X{sub a} compound Mn{sub 2}CoGa (Hg{sub 2}CuTi prototype) were prepared by dc magnetron co-sputtering with different heat treatments on MgO (001) substrates. High-quality films with a bulk magnetization of 1.95(5) {mu}{sub B} per unit cell were obtained. The L{sub 3,2} x-ray magnetic circular dichroism spectra agree with calculations based on density functional theory (DFT) and reveal the antiparallel alignment of the two inequivalent Mn moments. X-ray magnetic linear dichroism, in good agreement with theory as well, allows us to distinguish between itinerant and local Mn moments. Based on noncollinear spin DFT, it is shown that one of the two Mn moments has local character, whereas the other Mn moment and the Co moment are itinerant.

  8. Close-in planet migration due to magnetic torques

    NASA Astrophysics Data System (ADS)

    Strugarek, Antoine; Brun, Allan Sacha; Matt, Sean; Réville, Victor

    2015-08-01

    The diversity of masses, sizes and orbits of known exoplanets has prompted recent efforts in the scientific community to explore the broad range of interactions that can exist between planets and their host stars. In addition to tidal interactions, planets orbiting inside the stellar wind Alfv ´en radius can magnetically interact with their host. These interactions could lead to an angular momentum transfer between the planet and its host, resulting in a substantial planetary migration and participating in the dynamical (in)stability of the system. Among the star-planet interaction (SPI) models that have been developed, magnetohydrodynamic (MHD) simulations combine state of the art numerical models of cool star magnetospheres with simplified models of planets. The advantage of these global, dynamical models is the ability to assess the effects of SPI in a self-consistent way, by modelling the full interaction channel from the planetary magnetosphere down to the lower stellar corona.We will present our study of global magnetic SPI using the PLUTO code. We first give an overview of different types of interactions, depending on the stellar wind and orbital properties. Based on our previous exploratory 2D axisymmetric study, we develop our magnetic interaction model in 3D to tackle the full geometry of the star-wind- planet connection. We study the formation of Aflv ´en wings and parametrize the key physical ingredients (magnetic field strength and topology, orbital distance, stellar wind mass and angular momentum loss rates) controlling the magnetic torques which lead to planet migration. These torques are shown to operate on time-scales comparable to tidal torques for sufficiently compact systems and favorable magnetic topologies.

  9. Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.

    PubMed

    Baumann, S; Donati, F; Stepanow, S; Rusponi, S; Paul, W; Gangopadhyay, S; Rau, I G; Pacchioni, G E; Gragnaniello, L; Pivetta, M; Dreiser, J; Piamonteze, C; Lutz, C P; Macfarlane, R M; Jones, B A; Gambardella, P; Heinrich, A J; Brune, H

    2015-12-01

    We report on the magnetic properties of individual Fe atoms deposited on MgO(100) thin films probed by x-ray magnetic circular dichroism and scanning tunneling spectroscopy. We show that the Fe atoms have strong perpendicular magnetic anisotropy with a zero-field splitting of 14.0±0.3  meV/atom. This is a factor of 10 larger than the interface anisotropy of epitaxial Fe layers on MgO and the largest value reported for Fe atoms adsorbed on surfaces. The interplay between the ligand field at the O adsorption sites and spin-orbit coupling is analyzed by density functional theory and multiplet calculations, providing a comprehensive model of the magnetic properties of Fe atoms in a low-symmetry bonding environment.

  10. The magnetic moment enigma in Fe-based high temperature superconductors.

    PubMed

    Mannella, Norman

    2014-11-26

    The determination of the most appropriate starting point for the theoretical description of Fe-based materials hosting high-temperature superconductivity remains among the most important unsolved problem in this relatively new field. Most of the work to date has focused on the pnictides, with LaFeAsO, BaFe(2)As(2) and LiFeAs being representative parent compounds of three families known as 1111, 122 and 111, respectively. This topical review examines recent progress in this area, with particular emphasis on the implication of experimental data which have provided evidence for the presence of electron itinerancy and the detection of local spin moments. In light of the results presented, the necessity of a theoretical framework contemplating the presence and the interplay between itinerant electrons and large spin moments is discussed. It is argued that the physics at the heart of the macroscopic properties of pnictides Fe-based high-temperature superconductors appears to be far more complex and interesting than initially predicted. PMID:25352180

  11. Closed loop control of the induction heating process using miniature magnetic sensors

    DOEpatents

    Bentley, Anthony E.; Kelley, John Bruce; Zutavern, Fred J.

    2003-05-20

    A method and system for providing real-time, closed-loop control of the induction hardening process. A miniature magnetic sensor located near the outer surface of the workpiece measures changes in the surface magnetic field caused by changes in the magnetic properties of the workpiece as it heats up during induction heating (or cools down during quenching). A passive miniature magnetic sensor detects a distinct magnetic spike that appears when the saturation field, B.sub.sat, of the workpiece has been exceeded. This distinct magnetic spike disappears when the workpiece's surface temperature exceeds its Curie temperature, due to the sudden decrease in its magnetic permeability. Alternatively, an active magnetic sensor can measure changes in the resonance response of the monitor coil when the excitation coil is linearly swept over 0-10 MHz, due to changes in the magnetic permeability and electrical resistivity of the workpiece as its temperature increases (or decreases).

  12. Paramagnons in the PrNi system with an induced magnetic moment

    SciTech Connect

    Tiden, N. N. Clement'ev, E. S.; Alekseev, P. A.; Gvasaliya, S. N.; Nefedova, E. V.; Lazukov, V. N.; Sadikov, I. P.

    2006-12-15

    The recent studies of the PrNi system have shown that, at a temperature slightly higher than the ferromagnetic ordering temperature (T{sub C} {approx} 21 K), softening of some part of magnetic excitations occurs near the {gamma} point of the Brillouin zone. The magnetic modes observed have been qualitatively described by a model taking into account the crystal field and the exchange interaction within the mean-field random-phase approximation. To refine the model parameters and obtain a complete set of excitation modes, inelastic neutron scattering measurements on PrNi single crystals and polycrystals have been performed at T = 23 K. An acoustic branch related to the level with high excitation energy has been observed for the first time. The character of its dispersion suggests that the low-energy acoustic mode is responsible for the magnetic phase transition.

  13. Exact closed-form expressions for the performance of the split-symbol moments estimator of signal-to-noise ratio

    NASA Technical Reports Server (NTRS)

    Dolinar, S.

    1990-01-01

    Previously, the performance of the split-symbol moments estimator (SSME) of signal-to-noise ratio (SNR) has been evaluated by means of approximate expressions for the estimator mean and variance. These are asymptotic formulas in the sense that they become accurate as the number of estimator samples gets large. Here, exact closed-form expressions are obtained for the same quantities. These expressions confirm the accuracy of the previously derived asymptotic results, and, unlike the asymptotic formulas, they are useful even when the number of samples is small. It is also shown that the conventional split-symbol estimator can be trivially scaled to form a signal-to-noise ratio estimator which is precisely unbiased (as long as the estimate is based on more than two split-symbols).

  14. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

    NASA Astrophysics Data System (ADS)

    White, Benjamin; Yazici, Duygu; Ho, Pei-Chun; Kanchanavatee, Noravee; Pouse, Naveen; Friedman, Aaron; Maple, M. Brian

    2015-03-01

    Large Ce-Ce distances of 6.7-6.8 Åand weak hybridization between Ce 4 f and itinerant electron states act to promote stable localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd), but also conspire to severely limit the strength of the Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic exchange interaction that couples them. As a consequence, measurements of electrical resistivity, performed on single-crystalline samples of these new Cd-based compounds down to 0.138 K, were unable to resolve any evidence for magnetic order. In this presentation, we will compare measurements of the physical properties of CeT2Cd20 (T = Ni, Pd) under ambient and applied pressures with the reported properties of the isostructural compounds CeT2X20 (T = transition metal; X = Al, Zn). We will use these comparisons to discuss the interplay of unit cell volume, hybridization, and the RKKY interaction and its role in establishing the ground states of the Ce-based ``1-2-20'' compounds. Sample synthesis and physical properties measurements were supported by the U.S. DOE under Grant No. DE-FG02-04-ER46105. Measurements of electrical resistivity below 1 K were supported by the NSF under Grants No. DMR-1206553 and No. DMR-1104544.

  15. Magnetic moments of JP=3/2+ decuplet baryons using effective quark masses in a chiral constituent quark model

    NASA Astrophysics Data System (ADS)

    Girdhar, Aarti; Dahiya, Harleen; Randhawa, Monika

    2015-08-01

    The magnetic moments of JP=3/2+ decuplet baryons have been calculated in the chiral constituent quark model (χ CQM ) with explicit results for the contribution coming from the valence quark polarizations, sea quark polarizations, and their orbital angular momentum. Since the JP=3/2+ decuplet baryons have short lifetimes, the experimental information about them is limited. The χ CQM has important implications for chiral symmetry breaking as well as SU(3) symmetry breaking since it works in the region between the QCD confinement scale and the chiral symmetry breaking scale. The predictions in the model not only give a satisfactory fit when compared with the experimental data but also show improvement over the other models. The effect of the confinement on quark masses has also been discussed in detail and the results of χ CQM are found to improve further with the inclusion of effective quark masses.

  16. Effect of spin-orbit nuclear charge density corrections due to the anomalous magnetic moment on halonuclei

    SciTech Connect

    Ong, A.; Berengut, J. C.; Flambaum, V. V.

    2010-07-15

    In this paper we consider the contribution of the anomalous magnetic moments of protons and neutrons to the nuclear charge density. We show that the spin-orbit contribution to the mean-square charge radius, which has been neglected in recent nuclear calculations, can be important in light halonuclei. We estimate the size of the effect in helium, lithium, and beryllium nuclei. It is found that the spin-orbit contribution represents a approx2% correction to the charge density at the center of the {sup 7}Be nucleus. We derive a simple expression for the correction to the mean-square charge radius due to the spin-orbit term and find that in light halonuclei it may be larger than the Darwin-Foldy term and comparable to finite size corrections. A comparison of experimental and theoretical mean-square radii including the spin-orbit contribution is presented.

  17. Measurement of the polarization and magnetic moment of Ξ¯+ antihyperons produced by 800-GeV/c protons

    NASA Astrophysics Data System (ADS)

    Ho, P. M.; Longo, M. J.; Nguyen, A.; Luk, K. B.; James, C.; Rameika, R.; Duryea, J.; Guglielmo, G.; Heller, K.; Johns, K.; Diehl, H. T.; Teige, S.; Thomson, G. B.; Zou, Y.

    1991-12-01

    The polarization of Ξ¯ + hyperons produced by 800-GeV/c protons in the inclusive reaction p+Be-->Ξ¯ ++X has been measured using a sample of 70 000 Ξ¯ + decays. The average polarization of the Ξ¯ +, at a mean xF=0.39 and pt=0.76 GeV/c, is -0.097+/-0.012+/-0.009, compared to -0.102+/-0.012+/-0.010 for the Ξ-. The large polarization found for the Ξ¯ + is not expected in any model for polarization of inclusively produced hyperons. The magnetic moment of the Ξ¯ + was measured to be 0.657+/-0.028+/-0.020 nuclear magnetons (μN), compared to (-0.674+/-0.021+/-0.020)μN for the Ξ-, in good agreement with CPT invariance.

  18. Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)

    SciTech Connect

    White, B. D.; Yazici, D.; Ho, P. -C.; Kanchanavatee, N.; Pouse, N.; Fang, Y.; Breindel, A. J.; Friedman, A. J.; Maple, M. B.

    2015-07-20

    Here, we report the physical properties of single crystals of the compounds CeT2Cd20 (T = Ni, Pd) that were grown in a molten Cd flux. Large separations of ~6.7- 6.8 Å between Ce ions favor the localized magnetic moments that are observed in measurements of the magnetization. The strength of the Ruderman-Kittel-Kasuya- Yosida magnetic exchange interaction between the localized moments is severely limited by the large Ce-Ce separations and by weak hybridization between localized Ce 4f and itinerant electron states. Measurements of electrical resistivity performed down to 0.138 K were unable to observe evidence for the emergence of magnetic order; however, magnetically-ordered ground states with very low transition temperatures are still expected in these compounds despite the isolated nature of the localized magnetic moments. Such a fragile magnetic order could be highly susceptible to tuning via applied pressure, but evidence for the emergence of magnetic order has not been observed so far in our measurements up to 2.5 GPa.

  19. Constraint on the magnetic dipole moment of neutrinos by the tip-RGB luminosity in ω-Centauri

    NASA Astrophysics Data System (ADS)

    Arceo-Díaz, S.; Schröder, K.-P.; Zuber, K.; Jack, D.

    2015-10-01

    In this work, we use models constructed with the Eggleton code for stellar evolution, along with the photometric data of the super-rich globular cluster ω-Centauri (Sollima et al., 2004), to put a constraint on the magnetic dipole moment of neutrinos. We begin with a review of the idea proposed by Raffelt and Dearborn (1988), in which, as a consequence of a non-zero magnetic dipole moment, the tip-RGB luminosity of low mass stars gets increased over its standard value. First, we measure the dependence of the He-core mass and bolometric luminosity, at the tip-RGB, on the existing fits to characterize plasmon decay into neutrinos, namely those from Itoh et al. (1992), Haft et al. (1994), and the more recent results from Kantor and Gushakov (2007). Then, stating our definition of the tip-RGB, we revise multiple theoretical aspects: the consequences of non-standard neutrino emission on the internal structure of stellar models, its impact on the calibration of the Reimers mass-loss rate and later evolutionary phases and the influence of initial Helium abundance, metallicity, convection theory and opacities. Finally, we consider the specific case of ω-Cen. Using our tip-RGB models, and the bolometric correction obtained by the PHOENIX code for stellar atmospheres, to estimate the luminosity for canonical and non-standard evolution, also measuring the impact of the reported chemical spread in ω-Cen on our results. We find that the upper limit μν ≤ 2.2 ×10-12μB is already well constrained by observations. This result compares with the one obtained by Viaux et al. (2013), μν ≤ 2.6 ×10-12μB , from photometric study of the globular cluster M5.

  20. Impact of fluorine based reactive chemistry on structure and properties of high moment magnetic material

    SciTech Connect

    Yang, Xiaoyu Chen, Lifan; Han, Hongmei; Fu, Lianfeng; Sun, Ming; Liu, Feng; Zhang, Jinqiu

    2014-05-07

    The impact of the fluorine-based reactive ion etch (RIE) process on the structural, electrical, and magnetic properties of NiFe and CoNiFe-plated materials was investigated. Several techniques, including X-ray fluorescence, 4-point-probe, BH looper, transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS), were utilized to characterize both bulk film properties such as thickness, average composition, Rs, ρ, Bs, Ms, and surface magnetic “dead” layers' properties such as thickness and element concentration. Experimental data showed that the majority of Rs and Bs changes of these bulk films were due to thickness reduction during exposure to the RIE process. ρ and Ms change after taking thickness reduction into account were negligible. The composition of the bulk films, which were not sensitive to surface magnetic dead layers with nano-meter scale, showed minimum change as well. It was found by TEM and EELS analysis that although both before and after RIE there were magnetic dead layers on the top surface of these materials, the thickness and element concentration of the layers were quite different. Prior to RIE, dead layer was actually native oxidation layers (about 2 nm thick), while after RIE dead layer consisted of two sub-layers that were about 6 nm thick in total. Sub-layer on the top was native oxidation layer, while the bottom layer was RIE “damaged” layer with very high fluorine concentration. Two in-situ RIE approaches were also proposed and tested to remove such damaged sub-layers.

  1. The permanent electric dipole moments and magnetic g(e)-factors of praseodymium monoxide (PrO).

    PubMed

    Wang, Hailing; Linton, Colan; Ma, Tongmei; Steimle, Timothy C

    2009-11-26

    The R(4.5) and P(6.5) branch features of the XX (0, 0) band of praseodymium monoxide (PrO) have been studied at a resolution of approximately 50 MHz field free and in the presence of static electric and magnetic fields. The permanent electric dipole moments, mu(el), of 3.01(6) D and 4.72(5) D for the X(2) (Omega = 4.5) and [18.1] (Omega = 5.5) states, respectively, were determined from the analysis of the Stark spectra. The magnetic g(e)-factors of 4.48(8) and 5.73(6) for the X(2) (Omega = 4.5) and [18.1] (Omega = 5.5) states, respectively, were determined from the analysis of the Zeeman spectra. The g(e)-factors are compared with those computed using wave functions predicted from ligand field theory and ab initio calculations. The mu(el) value for the X(2) (Omega = 4.5) state is compared to ab initio and density functional predicted values and with the experimental values of other lanthanide monoxides.

  2. Performance Testing of a Magnetically Suspended Double Gimbal Control Moment Gyro Based on the Single Axis Air Bearing Table

    PubMed Central

    Cui, Peiling; Zhang, Huijuan; Yan, Ning; Fang, Jiancheng

    2012-01-01

    Integrating the advantage of magnetic bearings with a double gimble control moment gyroscope (DGCMG), a magnetically suspended DGCMG (MSDGCMG) is an ideal actuator in high-precision, long life, and rapid maneuver attitude control systems. The work presented here mainly focuses on performance testing of a MSDGCMG independently developed by Beihang University, based on the single axis air bearing table. In this paper, taking into sufficient consideration to the moving-gimbal effects and the response bandwidth limit of the gimbal, a special MSDGCMG steering law is proposed subject to the limits of gimbal angle rate and angle acceleration. Finally, multiple experiments are carried out, with different MSDGCMG angular momenta as well as different desired attitude angles. The experimental results indicate that the MSDGCMG has a good gimbal angle rate and output torque tracking capabilities, and that the attitude stability with MSDGCMG as actuator is superior to 10−3°/s. The MSDGCMG performance testing in this paper, carried out under moving-base condition, will offer a technique base for the future research and application of MSDGCMGs. PMID:23012536

  3. Itinerant electrons, local moments, and magnetic correlations in the pnictide superconductors CeFeAsO₁₋xFxand Sr(Fe₁₋xCox)₂As₂

    DOE PAGES

    Vilmercati, Paolo; Fedorov, Alexei; Bondino, Federica; Offi, Francesco; Panaccione, Giancarlo; Lacovig, Paolo; Simonelli, Laura; McGuire, Michael A.; Sefat, Athena S. M.; Mandrus, David; et al

    2012-06-15

    A direct and element-specific measurement of the local Fe spin moment has been provided by analyzing the Fe 3s core level photoemission spectra in the parent and optimally doped CeFeAsO₁₋xFx (x = 0, 0.11) and Sr(Fe₁₋xCox)2As2 (x = 0, 0.10) pnictides. The rapid time scales of the photoemission process allowed the detection of large local spin moments fluctuating on a 10⁻¹⁵ s time scale in the paramagnetic, antiferromagnetic, and superconducting phases, indicative of the occurrence of ubiquitous strong Hund's magnetic correlations. The magnitude of the spin moment is found to vary significantly among different families, 1.3μB in CeFeAsO and 2.1μBmore » in SrFe₂As₂. Surprisingly, the spin moment is found to decrease considerably in the optimally doped samples, 0.9μB in CeFeAsO₀.₈₉F₀.₁₁ and 1.3μB in Sr(Fe₀.₉Co₀.₁)₂As₂. The strong variation of the spin moment against doping and material type indicates that the spin moments and the motion of itinerant electrons are influenced reciprocally in a self-consistent fashion, reflecting the strong competition between the antiferromagnetic superexchange interaction among the spin moments and the kinetic energy gain of the itinerant electrons in the presence of a strong Hund's coupling. By describing the evolution of the magnetic correlations concomitant with the appearance of superconductivity, these results constitute a fundamental step toward attaining a correct description of the microscopic mechanisms shaping the electronic properties in the pnictides, including magnetism and high-temperature superconductivity.« less

  4. Magnetic moment collapse induced axial alternative compressibility of Cr2TiAlC2 at 420 GPa from first principle

    NASA Astrophysics Data System (ADS)

    Ze-Jin, Yang; Rong-Feng, Linghu; Qing-He, Gao; Heng-Na, Xiong; Zhi-Jun, Xu; Ling, Tang; Guo-Zhu, Jia; Yun-Dong, Guo

    2016-09-01

    The electronic structure and thermodynamical properties of Cr2TiAlC2 are studied by first principles under pressure. The obtained results observed that the ferromagnetic order is the most stable ground state and the magnetic moment will collapse at about 50 GPa. As a result, the lattice a axis becomes stiffer above about 420 GPa, ultimately presenting the same axial compressibility trends with those of nonmagnetic compounds Mo2TiAlC2 and hypothetical Cr2TiAlC2. The elastic constants and phonon dispersion curves demonstrate the structural stability during the disappearance of magnetic moment and occurrence of axial alternative compressibility. The density of states and energy band calculations confirmed the existence of magnetic moment of Cr2TiAlC2 at 0 GPa and disappearance at high pressures above 50 GPa. Evolutions of magnetic moment collapse with pressure are confirmed by a variety of properties. The obtained grüneisen parameter and thermal expansion coefficients show the maximum value among the known MAX phases, to date and to the author’s knowledge.

  5. Magnetic moment collapse induced axial alternative compressibility of Cr2TiAlC2 at 420 GPa from first principle

    PubMed Central

    Ze-Jin, Yang; Rong-Feng, Linghu; Qing-He, Gao; Heng-Na, Xiong; Zhi-Jun, Xu; Ling, Tang; Guo-Zhu, Jia; Yun-Dong, Guo

    2016-01-01

    The electronic structure and thermodynamical properties of Cr2TiAlC2 are studied by first principles under pressure. The obtained results observed that the ferromagnetic order is the most stable ground state and the magnetic moment will collapse at about 50 GPa. As a result, the lattice a axis becomes stiffer above about 420 GPa, ultimately presenting the same axial compressibility trends with those of nonmagnetic compounds Mo2TiAlC2 and hypothetical Cr2TiAlC2. The elastic constants and phonon dispersion curves demonstrate the structural stability during the disappearance of magnetic moment and occurrence of axial alternative compressibility. The density of states and energy band calculations confirmed the existence of magnetic moment of Cr2TiAlC2 at 0 GPa and disappearance at high pressures above 50 GPa. Evolutions of magnetic moment collapse with pressure are confirmed by a variety of properties. The obtained grüneisen parameter and thermal expansion coefficients show the maximum value among the known MAX phases, to date and to the author’s knowledge. PMID:27666292

  6. Close correlation between magnetic properties and the soft phonon mode of the structural transition in BaFe2As2 and SrFe2As2

    DOE PAGES

    Parshall, D.; Pintschovius, L.; Niedziela, Jennifer L.; Castellan, J. -P.; Lamago, D.; Mittal, R.; Wolf, Th.; Reznik, Dmitry

    2015-04-27

    Pmore » arent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of TA phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe2As2 and SrFe2As2. We found that acoustic phonons at small wave vectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuating magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Finally, our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.« less

  7. Magnetic Moments in the Past: developing archaeomagnetic dating in the UK

    NASA Astrophysics Data System (ADS)

    Outram, Zoe; Batt, Catherine M.; Linford, Paul

    2010-05-01

    Magnetic studies of archaeological materials have a long history of development in the UK and the data produced by these studies is a key component of global models of the geomagnetic field. However, archaeomagnetic dating is not a widely used dating technique in UK archaeology, despite the potential to produce archaeologically significant information that directly relates to human activity. This often means that opportunities to improve our understanding of the past geomagnetic field are lost, because archaeologists are unaware of the potential of the method. This presentation discusses a project by the University of Bradford, UK and English Heritage to demonstrate and communicate the potential of archaeomagnetic dating of archaeological materials for routine use within the UK. The aims of the project were achieved through the production of a website and a database for all current and past archaeomagnetic studies carried out in the UK. The website provides archaeologists with the information required to consider the use of archaeomagnetic dating; including a general introduction to the technique, the features that can be sampled, the precision that can be expected from the dates and how much it costs. In addition, all archaeomagnetic studies carried out in the UK have been collated into a database, allowing similar studies to be identified on the basis of the location of the sites, the archaeological period and type of feature sampled. This clearly demonstrates how effective archaeomagnetic dating has been in different archaeological situations. The locations of the sites have been mapped using Google Earth so that studies carried out in a particular region, or from a specific time period can be easily identified. The database supports the continued development of archaeomagnetic dating in the UK, as the data required to construct the secular variation curves can be extracted easily. This allows the curves to be regularly updated following the production of new

  8. Local magnetic moment formation at 119Sn Mössbauer impurity in RFe2 ( R=rare-earth metals) Laves phases compounds

    NASA Astrophysics Data System (ADS)

    de Oliveira, A. L.; de Oliveira, N. A.; Troper, A.

    2010-05-01

    The purpose of the present work is to theoretically study the local magnetic moment formation and the systematics of the magnetic hyperfine fields at a non-magnetic s-p Mössbauer 119Sn impurity diluted on R sites ( R=rare-earth metals) of the cubic Laves phases intermetallic compounds RFe2. One considers that the magnetic hyperfine field has two contributions (i) the contribution from R ions, calculated via an extended Daniel-Friedel [J. Phys. Chem. Solids 24 (1963) 1601] model and (ii) the contribution from the induced magnetic moments arising from the Fe neighboring sites. We have in this case a two-center Blandin-Campbell-like [Phys. Rev. Lett. 31 (1973) 51; J. Magn. Magn. Mater. 1 (1975) 1] problem, where a magnetic 3d-element located at a distance from the 119Sn impurity gives an extra magnetization to a polarized electron gas which is strongly charge perturbed at the 119Sn impurity site. We also include in the model, the nearest-neighbor perturbation due to the translational invariance breaking introduced by the impurity. Our self-consistent total magnetic hyperfine field calculations are in a very good agreement with recent experimental data.

  9. Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere.

    PubMed

    Fear, R C; Milan, S E; Maggiolo, R; Fazakerley, A N; Dandouras, I; Mende, S B

    2014-12-19

    The structure of Earth's magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs. PMID:25525244

  10. Direct observation of closed magnetic flux trapped in the high-latitude magnetosphere.

    PubMed

    Fear, R C; Milan, S E; Maggiolo, R; Fazakerley, A N; Dandouras, I; Mende, S B

    2014-12-19

    The structure of Earth's magnetosphere is poorly understood when the interplanetary magnetic field is northward. Under this condition, uncharacteristically energetic plasma is observed in the magnetotail lobes, which is not expected in the textbook model of the magnetosphere. Using satellite observations, we show that these lobe plasma signatures occur on high-latitude magnetic field lines that have been closed by the fundamental plasma process of magnetic reconnection. Previously, it has been suggested that closed flux can become trapped in the lobe and that this plasma-trapping process could explain another poorly understood phenomenon: the presence of auroras at extremely high latitudes, called transpolar arcs. Observations of the aurora at the same time as the lobe plasma signatures reveal the presence of a transpolar arc. The excellent correspondence between the transpolar arc and the trapped closed flux at high altitudes provides very strong evidence of the trapping mechanism as the cause of transpolar arcs.

  11. Open and closed string vertices for branes with magnetic field and T-duality

    NASA Astrophysics Data System (ADS)

    Pesando, Igor

    2010-02-01

    We discuss carefully the vertices which describe the dipole open strings and closed strings on a D-brane with magnetic flux on a torus. Translation invariance along closed cycles forces surprisingly closed string vertices written in open string formalism to acquire Chan-Paton like matrices. Moreover the one loop amplitudes have a single trace for the part of gauge group with the magnetic flux. These peculiarities are also required by consistency of the action of T-duality in the open string sector. In this way we can show to all orders in perturbation theory the equivalence of the T-dual open string theories, gravitational interactions included. We provide also a new and direct derivation of the bosonic boundary state in presence of constant magnetic and Kalb-Ramond background based on Sciuto-Della Selva-Saito vertex formalism.

  12. Effects of the Index Finger Position and Force Production on the Flexor Digitorum Superficialis Moment Arms at the Metacarpophalangeal Joints- an Magnetic Resonance Imaging Study

    PubMed Central

    Martin, Joel R.; Latash, Mark L.; Zatsiorsky, Vladimir M.

    2011-01-01

    Background The purpose of this study was to use magnetic resonance imaging to measure the moment arm of the flexor digitorum superficialis tendon about the metacarpophalangeal joint of the index, middle, ring, and little fingers when the position and force production level of the index finger was altered. A secondary goal was to create regression models using anthropometric data to predict moment arms of the flexor digitorum superficialis about the metacarpophalangeal joint of each finger. Methods The hands of subjects were scanned using a 3.0T magnetic resonance imaging scanner. The metacarpophalangeal joint of the index finger was placed in: flexion, neutral, and extension. For each joint configuration subjects produced no active force (passive condition) and exerted a flexion force to resist a load at the fingertip (active condition). Results The following was found: (1) The moment arm of the flexor digitorum superficialis at the metacarpophalangeal joint of the index finger (a) increased with the joint flexion and stayed unchanged with finger extension; and (b) decreased with the increase of force at the neutral and extended finger postures and did not change at the flexed posture. (2) The moment arms of the flexor digitorum superficialis tendon of the middle, ring, and little fingers (a) did not change when the index metacarpophalangeal joint position changed (p > 0.20); and (b) The moment arms of the middle and little fingers increased when the index finger actively produced force at the flexed metacarpophalangeal joint posture. (4) The moment arms showed a high correlation with anthropometric measurements. Interpretation Moment arms of the flexor digitorum superficialis change due to both changes in joint angle and muscle activation; they scale with various anthropometric measures. PMID:22192658

  13. Subtle Interplay between Localized Magnetic Moments and Itinerant Electrons in LaAlO3/SrTiO3 Heterostructures.

    PubMed

    Hu, Hai-Long; Zeng, Rong; Pham, Anh; Tan, Thiam Teck; Chen, Zhigang; Kong, Charlie; Wang, Danyang; Li, Sean

    2016-06-01

    Clarification of the role of magnetic ordering and scattering in two-dimensional electron gas has become increasingly important to understand the transport and magnetic behavior in the LaAlO3 (LAO)/SrTiO3 (STO) heterostructures. In this work, we report the sheet resistance of the LAO/STO heterostructures as functions of temperature, magnetic field, and field orientation. An unexpected resistance minimum was discovered at ∼10 K under a sufficiently high in-plane magnetic field. An anisotropic magnetoresistance (MR) is clearly identified, indicating the presence of magnetic scattering which may be related to the interaction between itinerant electrons and localized magnetic moments in the LaAlO3/SrTiO3 heterostructures. It is believed that the high concentration of oxygen vacancies induced by the ultralow oxygen partial pressure during the deposition process plays a predominant role in the occurrence of the anisotropic MR. PMID:27186855

  14. Magnetic moment directions and distributions of cations in Cr (Co) substituted spinel ferrites Ni{sub 0.7}Fe{sub 2.3}O{sub 4}

    SciTech Connect

    Xue, L. C.; Lang, L. L.; Li, Z. Z.; Qi, W. H.; Tang, G. D. Wu, L. Q.; Xu, J.

    2015-09-15

    Powder samples of the spinel ferrites M{sub x}Ni{sub 0.7−x}Fe{sub 2.3}O{sub 4} (M = Cr, Co and 0.0 ≤ x ≤ 0.3) and Cr{sub x}Ni{sub 0.7}Fe{sub 2.3−x}O{sub 4} (0.0 ≤ x ≤ 0.3) were synthesized using the chemical co-precipitation method. The XRD spectra confirmed that the samples had a single-phase cubic spinel structure. Magnetic measurements showed that the magnetic moments (μ{sub exp}) per formula both at 10 K and 300 K increased with Co substitution, while the values of μ{sub exp} decreased with Cr substitution. Applying the assumption that the magnetic moments of Cr{sup 2+} and Cr{sup 3+} lie antiparallel to those of the divalent and trivalent Fe, Co, and Ni cations in the same sublattice of spinel ferrites, these interesting behaviors could be easily interpreted. The cation distributions of the three series of samples were estimated successfully by fitting the dependences of μ{sub exp}, measured at 10 K, on the doping level x, using a quantum-mechanical potential barrier model earlier proposed by our group. The results obtained for the Cr cation distributions at the (A) and [B] sites are very close to those obtained elsewhere using neutron diffraction.

  15. Closed magnetic structures in the chromosphere and in the transition region

    NASA Technical Reports Server (NTRS)

    Malherbe, J. M. (Editor); Schmieder, B.; Simon, G.; Mein, P.; Tandberg-Hanssen, E.

    1987-01-01

    Using simultaneous observations of the same solar regions in the lines H-alpha and C IV 1548 A, schematic models of closed magnetic lines have been derived from dynamical constraints. It is concluded that the magnetic loops are closed at higher levels above facular than above nonfacular regions. This result remains valid whatever are the assumed density models and even if the 3-min oscillations are taken into account. The center-to-limb behavior is well predicted by taking into account the relative opacity in the chromosphere and transition region.

  16. A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF

    NASA Astrophysics Data System (ADS)

    Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter

    2011-01-01

    Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings.

  17. Failure-tolerant control for small agile satellites using single-gimbal control moment gyros and magnetic torquers

    NASA Astrophysics Data System (ADS)

    Meng, Tao; Matunaga, Saburo

    2012-04-01

    This paper focuses on the attitude control problem of small agile satellites using single-gimbal control moment gyros (CMG) and magnetic torquers (MTQ). CMGs are regarded as effective torque generators for agile satellites because of their torque amplification capability. However, they are vulnerable to failure due to their complex inner mechanism. In this paper, different failure cases of CMGs are analyzed. A flexible failure-tolerant control strategy is developed by automatically redistributing the required control torque among the operating CMGs and MTQs, with a variable limiter to accommodate the actuator dynamics changes introduced by CMG failures. The performances of maneuvers about different directions under different failure cases are also discussed and examined. Numerical simulations demonstrate that the proposed strategy maintains certain agility in the cases of one or two CMGs failing. Moreover, a survival strategy with only one CMG left is also verified. Both sun-pointing stabilization and earth-pointing stabilization can be achieved in this case, which fulfill some basic mission requirements.

  18. A to Z of the muon anomalous magnetic moment in the MSSM with Pati-Salam at the GUT scale

    NASA Astrophysics Data System (ADS)

    Belyaev, Alexander S.; Camargo-Molina, José E.; King, Steve F.; Miller, David J.; Morais, António P.; Schaefers, Patrick B.

    2016-06-01

    We analyse the low energy predictions of the minimal supersymmetric standard model (MSSM) arising from a GUT scale Pati-Salam gauge group further constrained by an A 4 × Z 5 family symmetry, resulting in four soft scalar masses at the GUT scale: one left-handed soft mass m 0 and three right-handed soft masses m 1 , m 2 , m 3, one for each generation. We demonstrate that this model, which was initially developed to describe the neutrino sector, can explain collider and non-collider measurements such as the dark matter relic density, the Higgs boson mass and, in particular, the anomalous magnetic moment of the muon ( g - 2) μ . Since about two decades, ( g - 2) μ suffers a puzzling about 3 σ excessoftheexperimentallymeasuredvalueoverthetheoreticalprediction,whichour model is able to fully resolve. As the consequence of this resolution, our model predicts specific regions of the parameter space with the specific properties including light smuons and neutralinos, which could also potentially explain di-lepton excesses observed by CMS and ATLAS.

  19. Transition magnetic moments of Majorana neutrinos in supersymmetry without R-parity in light of neutrino oscillations

    SciTech Connect

    Gozdz, Marek; Kaminski, Wieslaw A.; Simkovic, Fedor; Faessler, Amand

    2006-09-01

    The transition magnetic moments of Majorana neutrinos {mu}{sub {nu}{sub ij}} (ij=e{mu}, e{tau}, {mu}{tau}) are calculated in grand unified theory (GUT) constrained Minimal Supersymmetric Standard Model (MSSM) with explicit R-parity violation. It is assumed that neutrinos acquire masses via one-loop (quark-squark and lepton-slepton) radiative corrections. The mixing of squarks, sleptons, and quarks is considered explicitly. The connection between {mu}{sub {nu}{sub ij}} and the entries of neutrino mass matrix is studied. The current upper limits on {mu}{sub {nu}{sub ij}} are deduced from the elements of phenomenological neutrino mass matrix, which is reconstructed using the neutrino oscillation data and the lower bound on the neutrinoless double beta decay half-life. Further, the results for {mu}{sub {nu}{sub e}{sub {mu}}}, {mu}{sub {nu}{sub e}{sub {tau}}} and {mu}{sub {nu}{sub {mu}}{sub {tau}}} are presented for the cases of inverted and normal hierarchy of neutrino masses and different SUSY scenarios. The largest values are of the order of 10{sup -17} in units of Bohr magneton.

  20. Informatics Moments

    ERIC Educational Resources Information Center

    Williams, Kate

    2012-01-01

    The informatics moment is the moment when a person seeks help in using some digital technology that is new to him or her. This article examines the informatics moment in people's everyday lives as they sought help at a branch public library. Four types of literacy were involved: basic literacy (reading and writing), computer literacy (use of a…

  1. Structural Origin of the Anomalous Temperature Dependence of the Local Magnetic Moments in the CaFe2As2 Family of Materials

    NASA Astrophysics Data System (ADS)

    Ortenzi, L.; Gretarsson, H.; Kasahara, S.; Matsuda, Y.; Shibauchi, T.; Finkelstein, K. D.; Wu, W.; Julian, S. R.; Kim, Young-June; Mazin, I. I.; Boeri, L.

    2015-01-01

    We report a combination of Fe K β x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2(As1-xPx) 2 . The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2As2 [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in CaFe2(As1-xPx) 2 . We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2(As1-xPx) 2 (x =0.055 ) and Ca0.78La0.22Fe2As2 at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the c -axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2As2 family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides.

  2. Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe2As2 family of materials.

    PubMed

    Ortenzi, L; Gretarsson, H; Kasahara, S; Matsuda, Y; Shibauchi, T; Finkelstein, K D; Wu, W; Julian, S R; Kim, Young-June; Mazin, I I; Boeri, L

    2015-01-30

    We report a combination of Fe Kβ x-ray emission spectroscopy and density functional reduced Stoner theory calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe2(As1-xPx)2. The puzzling temperature behavior of the local moment found in rare earth-doped CaFe2As2 [H. Gretarsson et al., Phys. Rev. Lett. 110, 047003 (2013)] is also observed in CaFe2(As1-xPx)2. We explain this phenomenon based on first-principles calculations with scaled magnetic interaction. One scaling parameter is sufficient to describe quantitatively the magnetic moments in both CaFe2(As1-xPx)2 (x=0.055) and Ca0.78La0.22Fe2As2 at all temperatures. The anomalous growth of the local moments with increasing temperature can be understood from the observed large thermal expansion of the c-axis lattice parameter combined with strong magnetoelastic coupling. These effects originate from the strong tendency to form As-As dimers across the Ca layer in the CaFe2As2 family of materials. Our results emphasize the dual local-itinerant character of magnetism in Fe pnictides. PMID:25679903

  3. Correlation of electronic structure and magnetic moment in Ga1-xMnxN : First-principles, mean field and high temperature series expansions calculations

    NASA Astrophysics Data System (ADS)

    Masrour, R.; Hlil, E. K.

    2016-08-01

    Self-consistent ab initio calculations based on density-functional theory and using both full potential linearized augmented plane wave and Korring-Kohn-Rostoker-coherent potential approximation methods, are performed to investigate both electronic and magnetic properties of the Ga1-xMnxN system. Magnetic moments considered to lie along (001) axes are computed. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters such as the magnetic phase diagram and the critical exponent. The increasing of the dilution x in this system has allowed to verify a series of HTSEs predictions on the possibility of ferromagnetism in dilute magnetic insulators and to demonstrate that the interaction changes from antiferromagnetic to ferromagnetic passing through the spins glace phase.

  4. Single axis controlled hybrid magnetic bearing for left ventricular assist device: hybrid core and closed magnetic circuit.

    PubMed

    da Silva, Isaias; Horikawa, Oswaldo; Cardoso, Jose R; Camargo, Fernando A; Andrade, Aron J P; Bock, Eduardo G P

    2011-05-01

    In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD. PMID:21595710

  5. Single axis controlled hybrid magnetic bearing for left ventricular assist device: hybrid core and closed magnetic circuit.

    PubMed

    da Silva, Isaias; Horikawa, Oswaldo; Cardoso, Jose R; Camargo, Fernando A; Andrade, Aron J P; Bock, Eduardo G P

    2011-05-01

    In previous studies, we presented main strategies for suspending the rotor of a mixed-flow type (centrifugal and axial) ventricular assist device (VAD), originally presented by the Institute Dante Pazzanese of Cardiology (IDPC), Brazil. Magnetic suspension is achieved by the use of a magnetic bearing architecture in which the active control is executed in only one degree of freedom, in the axial direction of the rotor. Remaining degrees of freedom, excepting the rotation, are restricted only by the attraction force between pairs of permanent magnets. This study is part of a joint project in development by IDPC and Escola Politecnica of São Paulo University, Brazil. This article shows advances in that project, presenting two promising solutions for magnetic bearings. One solution uses hybrid cores as electromagnetic actuators, that is, cores that combine iron and permanent magnets. The other solution uses actuators, also of hybrid type, but with the magnetic circuit closed by an iron core. After preliminary analysis, a pump prototype has been developed for each solution and has been tested. For each prototype, a brushless DC motor has been developed as the rotor driver. Each solution was evaluated by in vitro experiments and guidelines are extracted for future improvements. Tests have shown good results and demonstrated that one solution is not isolated from the other. One complements the other for the development of a single-axis-controlled, hybrid-type magnetic bearing for a mixed-flow type VAD.

  6. Closed-loop magnetic separation of nanoparticles on a packed bed of spheres

    NASA Astrophysics Data System (ADS)

    Magnet, Cécilia; Akouala, Mesferdon; Kuzhir, Pavel; Bossis, Georges; Zubarev, Andrey; Wereley, Norman M.

    2015-05-01

    In this work, we consider magnetic separation of iron oxide nanoparticles when a nanoparticle suspension (diluted ferrofluid) passes through a closed-loop filter composed of a packed bed of micro-beads magnetized by an externally applied magnetic field. We show that the capture of nanoparticles of a size as small as 60 nm is easily achieved at low-to-moderate magnetic fields (16-32 kA/m) thanks to relatively strong magnetic interactions between them. The key parameter governing the capture process is the Mason number—the ratio of hydrodynamic-to-magnetic forces exerted to nanoparticles. The filter efficiency, Λ, defined through the ratio of the inlet-to-outlet concentration shows a power-law dependency on Mason number, Λ∝M a-0.83 , in the range of 102magnetic nanoparticles, followed by magnetic separation of the nanoparticles.

  7. Bound states for a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field

    SciTech Connect

    Bakke, K.

    2014-02-15

    We discuss the arising of bound states solutions of the Schrödinger equation due to the presence of a Coulomb-type potential induced by the interaction between a moving electric quadrupole moment and a magnetic field. Furthermore, we study the influence of the Coulomb-type potential on the harmonic oscillator by showing a quantum effect characterized by the dependence of the angular frequency on the quantum numbers of the system, whose meaning is that not all values of the angular frequency are allowed. -- Highlights: • Interaction between a moving electric quadrupole moment and a magnetic field. • Arising of bound states solutions due to the presence of a Coulomb-type potential. • Influence of the Coulomb-type potential on the harmonic oscillator. • Dependence of the angular frequency on the quantum numbers of the system.

  8. Unitary model for the {gamma}p {yields} {gamma}{pi}{sup 0}p reaction and the magnetic dipole moment of the {Delta}{sup +}(1232)

    SciTech Connect

    W.T. Chiang; Marc Vanderhaeghen; S.N. Yang; D. Drechsel

    2004-09-01

    Radiative pion photoproduction in the {Delta}(1232) resonance region is studied with the aim to access the {Delta}{sup +}(1232) magnetic dipole moment. We present a unitary model of the {gamma}p {yields} {gamma}{pi}N ({pi}N) = ({pi}{sup 0}p, {pi}{sup +}n) reactions, where the {pi}N rescattering is included in an on-shell approximation. In this model, the low energy theorem which couples the {gamma}p {yields} {gamma}{pi}N process in the limit of a soft final photon to the {gamma}p {yields} {pi}N process is exactly satisfied. We study the sensitivity of the {gamma}p {yields} {gamma}{pi}{sup 0}p process at higher values of the final photon energy to the {Delta}{sup +}(1232) magnetic dipole moment. We compare our results with existing data and give predictions for forthcoming measurements of angular and energy distributions. It is found that the photon asymmetry and a helicity cross section are particularly sensitive to the {Delta}{sup +} magnetic dipole moment.

  9. Studies of Dynamic, Radiative Macroscopic Magnetized HED Plasmas with Closed B-Field Lines

    SciTech Connect

    Frese, Michael H.; Frese, Sherry D.

    2013-11-01

    The purpose of this research has been to study the physics of macroscopic magnetized high-energy-density laboratory plasmas (HEDLPs) created through the compression of a high-beta compact toroid (CT) plasma having closed magnetic field lines. The high-beta CT chosen for this work is a field-reversed configuration (FRC). The basic approach is to investigate CT plasmas as they are compressed to a HED state by the electromagnetic implosion of a surrounding metallic shell or solid liner (Figure 1). The shell provides an axisymmetric, electrically-conducting boundary around the plasma and its supporting magnetic field and is imploded by means of the magnetic pressure force arising from axial current flow in the liner interacting with its associated azimuthal magnetic field. Compression of the CT will bring the plasma to fusion temperatures at higher densities and magnetic fields (multi-MegaGauss [MG]) than have previously been present in conventional magnetic fusion approaches. The resulting energy densities will be ~1 Mbar or greater and thus will place the plasma in a parameter space intermediate to MFE and IFE. This work has been a collaboration between the Air Force Research Laboratory, Los Alamos National Laboratory, and NumerEx, LLC.

  10. On the diversity of magnetic interactions in close-in star-planet systems

    SciTech Connect

    Strugarek, A.; Brun, A. S.; Réville, V.

    2014-11-01

    Magnetic interactions between close-in planets and their host star can play an important role in the secular orbital evolution of the planets, as well as the rotational evolution of their host. As long as the planet orbits inside the Alfvén surface of the stellar wind, the magnetic interaction between the star and the planet can modify the wind properties and also lead to direct angular momentum transfers between the two. We model these star-planet interactions using compressible magnetohydrodynamic (MHD) simulations, and quantify the angular momentum transfers between the star, the planet, and the stellar wind. We study the cases of magnetized and non-magnetized planets and vary the orbital radius inside the Alfvén surface of the stellar wind. Based on a grid of numerical simulations, we propose general scaling laws for the modification of the stellar wind torque, for the torque between the star and the planet, and for the planet migration associated with the star-planet magnetic interactions. We show that when the coronal magnetic field is large enough and the star is rotating sufficiently slowly, the effect of the magnetic star-planet interaction is comparable to tidal effects and can lead to a rapid orbital decay.

  11. The Effects of Close Companions on the Magnetic Activity of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Morgan, D. P.; West, A. A.; Silvestri, N. M.

    2011-12-01

    We present a study of close white dwarf and M dwarf (WD+dM) binary systems that examines the effects that close companions have on magnetic field generation in M dwarfs. We used a base sample of 1602 white dwarf -- main seqeuence (WDMS) binaries from Rebassa-Mansergas et al. to determine a set of color cuts in u, g, r, i, and z. Then using the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) we constructed a sample of 2292 WD+dM pairs. We separated the dM and WD from each combined spectrum using an iterative technique that compared the WD and dM components to best-fit templates. Using the absolute height above the Galactic Plane as a proxy for age, and the Hα emission line as an indicator for magnetic activity, we investigated the age-activity relation for our sample; spectral types ≤M5. Our results show that early-type M dwarfs in close binary systems have increased magnetic activity in both magnitude and duration compared to their field counterparts. However, we begin to see a transition at spectral type M5 (just past the onset of full convection in M dwarfs), where the magnitude and duration in close WD+dM binary systems become more comparable to that of the field M dwarfs.

  12. The possibility to measure the magnetic moments of short-lived particles (charm and beauty baryons) at LHC and FCC energies using the phenomenon of spin rotation in crystals

    NASA Astrophysics Data System (ADS)

    Baryshevsky, V. G.

    2016-06-01

    The use of spin rotation effect in bent crystals for measuring the magnetic moment of short-lived particles in the range of LHC and FCC energies is considered. It is shown that the estimated number of produced baryons that are captured into a bent crystal grows as ∼γ 3 / 2 with increasing particle energy. Hence it may be concluded that the experimental measurement of magnetic moments of short-lived particles using the spin rotation effect is feasible at LHC and higher energies (for LHC energies, e.g., the running time required for measuring the magnetic moment of Λc+ is 2 ÷ 16 hours).

  13. The New (g-2) Experiment: A proposal to measure the muon anomalous magnetic moment to +-0.14 ppm precision

    SciTech Connect

    Carey, R.M.; Lynch, K.R.; Miller, J.P.; Roberts, B.L.; Morse, W.M.; Semertzides, Y.K.; Druzhinin, V.P.; Khazin, B.I.; Koop, I.A.; Logashenko, I.; Redin, S.I.; /Boston U. /Brookhaven /Novosibirsk, IYF /Cornell U., CIHEP /Fermilab /Frascati /Illinois U., Urbana /James Madison U. /Groningen, KVI /KEK, Tsukuba /Kentucky U.

    2009-02-01

    We propose to measure the muon anomalous magnetic moment, a{sub {mu}}, to 0.14 ppm-a fourfold improvement over the 0.54 ppm precision obtained in the BNL experiment E821. The muon anomaly is a fundamental quantity and its precise determination will have lasting value. The current measurement was statistics limited, suggesting that greater precision can be obtained in a higher-rate, next-generation experiment. We outline a plan to use the unique FNAL complex of proton accelerators and rings to produce high-intensity bunches of muons, which will be directed into the relocated BNL muon storage ring. The physics goal of our experiment is a precision on the muon anomaly of 16 x 10{sup -11}, which will require 21 times the statistics of the BNL measurement, as well a factor of 3 reduction in the overall systematic error. Our goal is well matched to anticipated advances in the worldwide effort to determine the standard model (SM) value of the anomaly. The present comparison, {Delta}a{sub {mu}} (Expt: -SM) = (295 {+-} 81) x 10{sup -11}, is already suggestive of possible new physics contributions to the muon anomaly. Assuming that the current theory error of 51 x 10{sup -11} is reduced to 30 x 10{sup -11} on the time scale of the completion of our experiment, a future {Delta}a{sub {mu}} comparison would have a combined uncertainty of {approx} 34 x 10{sup -11}, which will be a sensitive and complementary benchmark for proposed standard model extensions. The experimental data will also be used to improve the muon EDM limit by up to a factor of 100 and make a higher-precision test of Lorentz and CPT violation. We describe in this Proposal why the FNAL complex provides a uniquely ideal facility for a next-generation (g-2) experiment. The experiment is compatible with the fixed-target neutrino program; indeed, it requires only the unused Booster batch cycles and can acquire the desired statistics in less than two years of running. The proton beam preparations are largely aligned

  14. The Effect of Close Companions on the Magnetic Activity of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Morgan, Dylan; West, A. A.; Silvestri, N. M.

    2011-05-01

    We used close white dwarf and M dwarf (WD+dM) binary systems as a method to understand the effect that close companions have on magnetic field generation in M dwarfs. We used a base sample of 1602 white dwarf - main sequence (WDMS) binaries from Rebassa-Mansergas et al. (2010) to aid in determining a set of color cuts using GALEX, SDSS, 2MASS, and UKIDSS colors. Using the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8) we constructed a sample of 1800 WD+dM pairs. We separated the dM and WD from each combined spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age and the Hα emission line as an indicator for magnetic activity, we investigated the age-activity relation for our sample. Our results show that M dwarfs in close binary systems have increased magnetic activity in both magnitude and duration compared to their field counterparts.

  15. The Effects of Close Companions (and Rotation) on the Magnetic Activity of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Morgan, Dylan P.; West, Andrew A.; Garcés, Ane; Catalán, Silvia; Dhital, Saurav; Fuchs, Miriam; Silvestri, Nicole M.

    2012-10-01

    We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the Hα emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types <= M7. Our results show that early-type M dwarfs (<=M4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems become more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully convective stars. Using the WD components of the pairs, we find WD cooling ages to use as an additional constraint on the age-activity relation for our sample. We find that, on average, active early-type dMs tend to be younger and that active late-type dMs span a much broader age regime making them

  16. THE EFFECTS OF CLOSE COMPANIONS (AND ROTATION) ON THE MAGNETIC ACTIVITY OF M DWARFS

    SciTech Connect

    Morgan, Dylan P.; West, Andrew A.; Dhital, Saurav; Fuchs, Miriam; Garces, Ane; Catalan, Silvia; Silvestri, Nicole M.

    2012-10-01

    We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf main-sequence binaries from Rebassa-Mansergas et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space. Then using the SDSS Data Release 8 spectroscopic database, we construct a sample of 1756 WD+dM high-quality pairs from our color cuts and previous catalogs. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types {<=} M7. Our results show that early-type M dwarfs ({<=}M4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just past the onset of full convection in M dwarfs), the activity fraction and lifetimes of WD+dM binary systems become more comparable to that of the field M dwarfs. One of the implications of having a close binary companion is presumed to be increased stellar rotation through disk disruption, tidal effects, or angular momentum exchange. Thus, we interpret the similarity in activity behavior between late-type dMs in WD+dM pairs and late-type field dMs to be due to a decrease in sensitivity in close binary companions (or stellar rotation), which has implications for the nature of magnetic activity in fully convective stars. Using the WD components of the pairs, we find WD cooling ages to use as an additional constraint on the age-activity relation for our sample. We find that, on average, active early-type dMs tend to be younger and that active late-type dMs span a much broader age regime making them

  17. Differing long-term evolutions of the solar open and closed magnetic fields

    NASA Astrophysics Data System (ADS)

    Dudok de Wit, Thierry; Watermann, Jurgen; Vieira, Luis Eduardo; Mursula, Kalevi

    During the last decade, there has been an ongoing debate around a possible tripling of the solar open magnetic flux over the 20th century. This result is based on 150 years of observations of the aa geomagnetic index, from which the open magnetic flux can be inferred. The aa index actually reveals the existence of two simultaneous 11-year cycles, as shown by Simon and Legrand in the 1980's. By studying the transfer function between the Sun and these two cycles, the relative contribution of both the solar open and closed magnetic fields can be inferred. Interestingly, the two exhibit quite different long-term evolutions. This may explain discrepancies between long-term reconstructions of solar activity based on sunspot numbers and on cosmogenic isotopes..

  18. Braiding, Turbulent 3D Reconnection and Impulsive Heating of the Magnetically Closed Corona

    NASA Astrophysics Data System (ADS)

    Russell, A. J. B.; Hornig, G.; Yeates, A.

    2015-12-01

    Magnetic braiding is one of the leading theories for heating the magnetically closed corona, however, understanding of the central processes has changed dramatically in recent years. In particular, it is now recognized that braided fields allow impulsive heating via the formation of large numbers of turbulently forming and evolving reconnection regions, which are volume filling and inherently 3D, and it is no longer necessary to invoke topological discontinuities to dissipate stored energy. It has also become clear that turbulent reconnection produces structures that are inconsistent with a Taylor relaxation model, raising questions about how much stored energy is available for heating and particle acceleration. Here, we look at recent progress that has been made in dealing with this complex heating mechanism and present a new advance that greatly improves estimates of the magnetic energy available for heating and particle acceleration.

  19. Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

    PubMed

    Yang, X F; Wraith, C; Xie, L; Babcock, C; Billowes, J; Bissell, M L; Blaum, K; Cheal, B; Flanagan, K T; Garcia Ruiz, R F; Gins, W; Gorges, C; Grob, L K; Heylen, H; Kaufmann, S; Kowalska, M; Kraemer, J; Malbrunot-Ettenauer, S; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Sánchez, R; Yordanov, D T

    2016-05-01

    Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence.

  20. Isomer Shift and Magnetic Moment of the Long-Lived 1/2^{+} Isomer in _{30}^{79}Zn_{49}: Signature of Shape Coexistence near ^{78}Ni.

    PubMed

    Yang, X F; Wraith, C; Xie, L; Babcock, C; Billowes, J; Bissell, M L; Blaum, K; Cheal, B; Flanagan, K T; Garcia Ruiz, R F; Gins, W; Gorges, C; Grob, L K; Heylen, H; Kaufmann, S; Kowalska, M; Kraemer, J; Malbrunot-Ettenauer, S; Neugart, R; Neyens, G; Nörtershäuser, W; Papuga, J; Sánchez, R; Yordanov, D T

    2016-05-01

    Collinear laser spectroscopy is performed on the _{30}^{79}Zn_{49} isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in ^{79}Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I=9/2 and I=1/2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (^{79}Zn)=-1.1866(10)μ_{N}, confirms the spin-parity 9/2^{+} with a νg_{9/2}^{-1} shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (^{79m}Zn)=-1.0180(12)μ_{N} supports a positive parity for the isomer, with a wave function dominated by a 2h-1p neutron excitation across the N=50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ⟨r_{c}^{2}⟩^{79,79m}=+0.204(6)  fm^{2}, providing first evidence of shape coexistence. PMID:27203317

  1. Isomer Shift and Magnetic Moment of the Long-Lived 1 /2+ Isomer in 30,79Zn49: Signature of Shape Coexistence near 78Ni

    NASA Astrophysics Data System (ADS)

    Yang, X. F.; Wraith, C.; Xie, L.; Babcock, C.; Billowes, J.; Bissell, M. L.; Blaum, K.; Cheal, B.; Flanagan, K. T.; Garcia Ruiz, R. F.; Gins, W.; Gorges, C.; Grob, L. K.; Heylen, H.; Kaufmann, S.; Kowalska, M.; Kraemer, J.; Malbrunot-Ettenauer, S.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Papuga, J.; Sánchez, R.; Yordanov, D. T.

    2016-05-01

    Collinear laser spectroscopy is performed on the 30,79Zn49 isotope at ISOLDE-CERN. The existence of a long-lived isomer with a few hundred milliseconds half-life is confirmed, and the nuclear spins and moments of the ground and isomeric states in 79Zn as well as the isomer shift are measured. From the observed hyperfine structures, spins I =9 /2 and I =1 /2 are firmly assigned to the ground and isomeric states. The magnetic moment μ (79Zn)=-1.1866 (10 )μN , confirms the spin-parity 9 /2+ with a ν g9/2 -1 shell-model configuration, in excellent agreement with the prediction from large scale shell-model theories. The magnetic moment μ (Znm79)=-1.0180 (12 )μN supports a positive parity for the isomer, with a wave function dominated by a 2 h -1 p neutron excitation across the N =50 shell gap. The large isomer shift reveals an increase of the intruder isomer mean square charge radius with respect to that of the ground state, δ ⟨rc2⟩79 ,79 m=+0.204 (6 ) fm2 , providing first evidence of shape coexistence.

  2. Local magnetic moments in a dinuclear Co{sup 2+} complex as seen by polarized neutron diffraction:Beyond the effective spin-(1/2) model

    SciTech Connect

    Borta, Ana; Luneau, Dominique; Jeanneau, Erwann; Gillon, Beatrice; Gukasov, Arsen; Cousson, Alain; Ciumacov, Iurii; Sakiyama, Hiroshi; Tone, Katsuya; Mikuriya, Masahiro

    2011-05-01

    Polarized neutron diffraction investigations of a paramagnetic molecular dinuclear Co{sup 2+} complex, using the local site susceptibility method, show that the Co{sup 2+} ions carry opposite magnetic moments of 3.1(1) and 3.2(1) {mu}{sub B}, making an angle of 37(1) deg. which is in agreement with the value (39 deg.) provided by the theoretical analysis of the magnetic susceptibility using the model of effective spin 1/2. Polarized neutron diffraction (PND) shows that this dinuclear Co{sup 2+} complex behaves more like a system of two antiferromagnetically coupled ions with spin 3/2, the directions of which are imposed by the distortion axis of the octahedra around each Co{sup 2+} ion due to ligand field. This first application of the local susceptibility tensor method to a molecular compound demonstrates the efficiency of the PND method as a tool for exploring magnetic anisotropy in molecular paramagnets.

  3. Physical properties of iron-nitride films epitaxially grown on silicon (001) by sputtering and assessment of giant magnetic moment in the alpha''-iron nitride phase

    NASA Astrophysics Data System (ADS)

    Brewer, Marilee Ann

    Intense scientific and technological interest in iron nitrides has persisted since saturation magnetizations much larger than that of alpha-Fe (1708 emu/cmsp3) were reported for the metastable alphasp{''}-Fesb{16}Nsb2 phase (2300 emu/cmsp3) grown by MBE on lattice-matched substrates. Most attempts at growing alphasp{''} using technologically-relevant deposition processes and substrates have resulted in only a modest enhancement in moment, and are complicated by competition from more stable FeN phases. Furthermore, conventional band theory calculations for alphasp{''} (1780 emu/cmsp3) do not predict a "giant" magnetic moment. We have grown several phases of FeN on Si(001) by lattice matching on Ag underlayers. Optimization of reactive Nsb2 sputtering parameters has led to the growth of alpha-Fe, gammasp''-Fesb4N and alphasp'-Fesb8N films. Annealing of N-disordered alphasp'-Fesb8N films resulted in partial transformation to N-ordered alphasp{''}-Fesb{16}Nsb2. Quantification of X-ray diffraction peak intensities determined that the alphasp'/alphasp{''} mixtures contained 48 vol% alphasp{''} (remaining alphasp'). Selected-area diffraction (SAD) in the TEM determined that the orientation relationships of the alpha,\\ alphasp', and alphasp{''} phases were FeN(001)VertAg(001)VertSi(001) and FeN(100) VertAg(110) VertSi(100), while the in-plane orientation of gammasp'(001) was FeN(110) VertAg(110) VertSi(100). Electron energy-loss spectroscopy (EELS) determined that the FeN films were stoichiometrically correct and there was no significant change in N content with annealing. Vibrating-sample magnetometry of the alphasp' and alphasp'/alphasp{''} films measured a saturation magnetization of 1780 emu/cmsp3 for both phases; there was no change in the magnetization with increasing N order and no giant moment. Mossbauer spectroscopy of the alphasp'/alphasp{''} films confirmed the presence of three chemically-inequivalent iron sites with the expected occupancy ratio for Fe

  4. Electromagnetic Steering of a Magnetic Cylindrical Microrobot Using Optical Feedback Closed-Loop Control

    NASA Astrophysics Data System (ADS)

    Ghanbari, Ali; Chang, Pyung H.; Nelson, Bradley J.; Choi, Hongsoo

    2014-04-01

    Control of small magnetic machines in viscous fluids may enable new medical applications of microrobots. Small-scale viscous environments lead to low Reynolds numbers, and although the flow is linear and steady, the magnetic actuation introduces a dynamic response that is nonlinear. We account for these nonlinearities, and the uncertainties in the dynamic and magnetic properties of the microrobot, by using time-delay estimation. The microrobot consists of a cylindrical magnet, 1 mm long and 500 µm in diameter, and is tracked using a visual feedback system. The microrobot was placed in silicone oil with a dynamic viscosity of 1 Pa.s, and followed step inputs with rise times of 0.45 s, 0.51 s, and 1.77 s, and overshoots of 37.5%, 33.3%, and 34.4% in the x, y, and z directions, respectively. In silicone oil with a viscosity of 3 Pa.s, the rise times were 1.04 s, 0.72 s, and 2.19 s, and the overshoots were 47.8%, 48.5%, and 86.8%. This demonstrates that closed-loop control of the magnetic microrobot was better in the less viscous fluid.

  5. Closed electron drift in a self-magnetically insulated ion diode

    SciTech Connect

    Pushkarev, A. I.; Isakova, Y. I.

    2013-05-15

    The paper investigates a spiral geometry self-magnetically insulated ion diode with an explosive-emission cathode made from graphite. The experiments have been carried out using the TEMP-4M accelerator, with the accelerator configured to operate in double-pulse mode: the first negative pulse (300–500 ns, 100–150 kV) and the second positive pulse (150 ns, 250–300 kV). The ion beam energy density was 0.4–0.8 J/cm{sup 2} and the beam was composed of carbon ions (80%–85%) and protons. In order to increase the efficiency of ion current generation, we have developed a new diode with a spiral-shaped grounded electrode. Using this geometry, it seems possible to realize closed electron drift in a diode with self-magnetic insulation. In the spiral diode, the efficiency of accelerated ions is increased from 5%–9% (conventional self-insulated diodes) up to 30%–40%. The realization of closed electron drift in the diode increases the efficiency of C{sup +} ion generation up to 40–50 times the Childe-Langmuir limit, which is more than 4 times higher than with other known constructions of self-magnetically insulated diodes.

  6. Dynamic effects of restoring footpoint symmetry on closed magnetic field lines

    NASA Astrophysics Data System (ADS)

    Reistad, J. P.; Østgaard, N.; Tenfjord, P.; Laundal, K. M.; Snekvik, K.; Haaland, S.; Milan, S. E.; Oksavik, K.; Frey, H. U.; Grocott, A.

    2016-05-01

    Here we present an event where simultaneous global imaging of the aurora from both hemispheres reveals a large longitudinal shift of the nightside aurora of about 3 h, being the largest relative shift reported on from conjugate auroral imaging. This is interpreted as evidence of closed field lines having very asymmetric footpoints associated with the persistent positive y component of the interplanetary magnetic field before and during the event. At the same time, the Super Dual Auroral Radar Network observes the ionospheric nightside convection throat region in both hemispheres. The radar data indicate faster convection toward the dayside in the dusk cell in the Southern Hemisphere compared to its conjugate region. We interpret this as a signature of a process acting to restore symmetry of the displaced closed magnetic field lines resulting in flux tubes moving faster along the banana cell than the conjugate orange cell. The event is analyzed with emphasis on Birkeland currents (BC) associated with this restoring process, as recently described by Tenfjord et al. (2015). Using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during the same conditions as the presented event, the large-scale BC pattern associated with the event is presented. It shows the expected influence of the process of restoring symmetry on BCs. We therefore suggest that these observations should be recognized as being a result of the dynamic effects of restoring footpoint symmetry on closed field lines in the nightside.

  7. Subtractive procedure for calculating the anomalous electron magnetic moment in QED and its application for numerical calculation at the three-loop level

    NASA Astrophysics Data System (ADS)

    Volkov, S. A.

    2016-06-01

    A new subtractive procedure for canceling ultraviolet and infrared divergences in the Feynman integrals described here is developed for calculating QED corrections to the electron anomalous magnetic moment. The procedure formulated in the form of a forest expression with linear operators applied to Feynman amplitudes of UV-diverging subgraphs makes it possible to represent the contribution of each Feynman graph containing only electron and photon propagators in the form of a converging integral with respect to Feynman parameters. The application of the developed method for numerical calculation of two- and threeloop contributions is described.

  8. Leading-order hadronic contribution to the anomalous magnetic moment of the muon from N_f=2+1+1 twisted mass fermions

    SciTech Connect

    Burger, Florian; Feng, Xu; Hotzel, Grit; Jansen, Karl; Petschlies, Marcus; Renner, Dru B.

    2013-11-01

    We present results for the leading order QCD correction to the anomalous magnetic moment of the muon including the first two generations of quarks as dynamical degrees of freedom. Several light quark masses are examined in order to yield a controlled extrapolation to the physical pion mass. We analyse ensembles for three different lattice spacings and several volumes in order to investigate lattice artefacts and finite-size effects, respectively. We also provide preliminary results for this quantity for two flavours of mass-degenerate quarks at the physical value of the pion mass.

  9. Open and Closed Magnetic Confinement Systems: Is There a Fundamental Difference in Their Transport Properties?

    SciTech Connect

    Post, R F

    2001-02-27

    The results of five decades of experimental investigations of open-ended and closed magnetic confinement geometries are examined to see if intrinsic topology-dependent differences in their cross-field transport can be discerned. The evidence strongly supports a picture in which closed systems (stellarators, tokamaks, reversed-field pinches, etc.) are in all cases studied to date characterized by some level of plasma turbulence, leading to substantial deviations from purely classical cross-field transport. This transport is often describable as a Bohm-like scaling with plasma temperature and magnetic field intensity. By contrast, open systems have in many significant examples been able to approach closely to classically predicted cross-field transport, including cases where the transport appeared to be more than five orders of magnitude slower than the Bohm-diffusion rate. To explain these differences the following tentative hypothesis is put forward: The differences arise from two sources: (1) differences in the instability driving terms arising from free-energy sources, such as current flow along the field lines, etc. and, (2) differences in the nature of the boundary conditions for the various unstable waves that may be stimulated by these free energy sources within the plasma. By analogy with a laser, closed systems, with their flux tubes returning on themselves, resemble a ring resonator, while open systems either have or can be arranged to have absorptive (or low reflectivity) end boundary conditions for unstable waves. It is suggested that if the hypothesis is a valid one it further enhances the desirability of devoting more effort to the investigation of open-ended systems than is now being allotted.

  10. New Measurement of the Electron Magnetic Moment and the Fine Structure Constant: A First Application of a One-Electron Quantum Cyclotron

    ScienceCinema

    Gabrielse, Gerald [Harvard University, Cambridge, Massachusetts, United States

    2016-07-12

    Remarkably, the famous UW measurement of the electron magnetic moment has stood since 1987. With QED theory, this measurement has determined the accepted value of the fine structure constant. This colloquium is about a new Harvard measurement of these fundamental constants. The new measurement has an uncertainty that is about six times smaller, and it shifts the values by 1.7 standard deviations. One electron suspended in a Penning trap is used for the new measurement, like in the old measurement. What is different is that the lowest quantum levels of the spin and cyclotron motion are resolved, and the cyclotron as well as spin frequencies are determined using quantum jump spectroscopy. In addition, a 0.1 mK Penning trap that is also a cylindrical microwave cavity is used to control the radiation field, to suppress spontaneous emission by more than a factor of 100, to control cavity shifts, and to eliminate the blackbody photons that otherwise stimulate excitations from the cyclotron ground state. Finally, great signal-to-noise for one-quantum transitions is obtained using electronic feedback to realize the first one-particle self-excited oscillator. The new methods may also allow a million times improved measurement of the 500 times small antiproton magnetic moment.

  11. Collapse of the magnetic moment under pressure of AFe2 (A=Y, Zr, Lu and Hf) in the cubic Laves phase

    NASA Astrophysics Data System (ADS)

    Zhang, Wenxu; Zhang, Wanli

    2016-04-01

    The electronic structures of four Laves phase iron compounds (e.g. YFe2, ZrFe2, LuFe2 and HfFe2) have been calculated with a state-of-the-art full potential electronic structure code. Our theoretical work predicted that the magnetic moments collapse under hydrostatic pressure. This feature is found to be universal in these materials. Its electronic origin is provided by the sharp peaks in the density of states near the Fermi level. It is shown that a first order quantum phase transition can be expected under pressure in Y(Zr, or Lu)Fe2, while a second order one in HfFe2. The bonding characteristics are discussed to elucidate the equilibrium lattice constant variation. The large spontaneous volume magnetostriction gives one of the most important characteristics of these compounds. Invar anomalies in these compounds can be partly explained by the current work when the fast continuous magnetic moment decrease with the decrease of the lattice constant was properly considered. This work may be as a first insight into the rich world of quantum phase transition and Invar mechanism in these Laves phase compounds.

  12. Effect of reactive gas (oxygen/chlorine/fluorine) etching on the magnetic flux of a high moment write pole material

    SciTech Connect

    Zhang Jinqiu; Liu Feng; Chen Lifan; Miloslavsky, Lena

    2010-05-15

    Effect of reactive gas (oxygen/chlorine/fluorine) etching on NiFe magnetic properties was investigated. Experimental data showed 40% magnetic property degradation for F-containing gas etching, 10% degradation for O-containing gas etching, and 5% degradation for Cl-containing gas etching processes. X-ray diffraction analysis indicated that the crystallographic orientation remained the same upon the reactive gas etching, which is due to the low ion energy in plasma etching process as opposed to ion milling process with high input energy. It is proposed that the reported magnetic property degradation was mainly caused by the nonmagnetic dead layer formation, rather than the changes in the crystallographic orientation. The dead layer was determined by the NiFe thickness dependence of remnant magnetic flux variations between pre-etched and postetched samples. The dead layer remained nearly constant for O-containing gas etching process with increasing plasma processing time. The nonmagnetic dead layer of {approx}40-50 A formed in O-containing etching gas was observed in transmission electron microscopy cross-sectional image and was in very good agreement with the calculated value based on magnetic flux measurements. Combined magnetic and physical characterizations suggest that the dead layer thickness saturates at the initial stage of the plasma etching and magnetic property remained unchanged with increasing etching duration upon formation of the dead layer.

  13. Proposed chiral texture of the magnetic moments of unit-cell loop currents in the pseudogap phase of cuprate superconductors.

    PubMed

    Pershoguba, Sergey S; Kechedzhi, Kostyantyn; Yakovenko, Victor M

    2013-07-26

    We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment N and exhibits the magnetoelectric effect. We propose a helical structure where the vector N(n) in the layer n is twisted by the angle π/2 relative to N(n-1), thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect.

  14. Intrinsic Gilbert Damping in Metallic Ferromagnets in Ballistic Regime and the Effect of Inelastic Electron Scattering from Magnetic Moments: A Time Dependent Keldysh Green Function Approach

    NASA Astrophysics Data System (ADS)

    Mahfouzi, Farzad; Kioussis, Nicholas

    Gilbert damping in metallic ferromagnets is mainly governed by the exchange coupling between the electrons and the magnetic degree of freedom, where the time dependent evolution of the magnetization leads to the excitation of electrons and loss of energy as a result of flow of spin and charge currents. However, it turns out that when the magnetization evolves slowly in time, in the presence of spin-orbit interaction (SOI), the resonant electronic excitations has a major contribution to the damping which leads to infinite result in ballistic regime. In this work we consider the inelastic spin-flip scattering of electrons from the magnetic moments and show that in the presence of SOI it leads to the relaxation of the excited electrons. We show that in the case of clean crystal systems such scattering leads to a linear dependence of the Gilbert on the SOI strength and in the limit of diffusive systems we get the Gilbert damping expression obtained from Kambersky's Fermi breathing approach. This research was supported by NSF-PREM Grant No. DMR-1205734

  15. Dynamics of magnetic flux tubes in close binary stars. I. Equilibrium and stability properties

    NASA Astrophysics Data System (ADS)

    Holzwarth, V.; Schüssler, M.

    2003-07-01

    Surface reconstructions of active close binary stars based on photometric and spectroscopic observations reveal non-uniform starspot distributions, which indicate the existence of preferred spot longitudes (with respect to the companion star). We consider the equilibrium and linear stability of toroidal magnetic flux tubes in close binaries to examine whether tidal effects are capable to initiate the formation of rising flux loops at preferred longitudes near the bottom of the stellar convection zone. The tidal force and the deviation of the stellar structure from spherical symmetry are treated in lowest-order perturbation theory assuming synchronised close binaries with orbital periods of a few days. The frequency, growth time, and spatial structure of linear eigenmodes are determined by a stability analysis. We find that, despite their small magnitude, tidal effects can lead to a considerable longitudinal asymmetry in the formation probability of flux loops, since the breaking of the axial symmetry due to the presence of the companion star is reinforced by the sensitive dependence of the stability properties on the stellar stratification and by resonance effects. The orientation of preferred longitudes of loop formation depends on the equilibrium configuration and the wave number of the dominating eigenmode. The change of the growth times of unstable modes with respect to the case of a single star is very small.

  16. Relationship between the magnetic moment of Lu and the magnetic behavior of (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} from x-ray absorption spectroscopy and x-ray magnetic circular dichroism

    SciTech Connect

    Chaboy, J.; Piquer, C.; Laguna-Marco, M. A.; Kawamura, N.; Suzuki, M.; Takagaki, M.

    2007-02-01

    We present an x-ray magnetic circular dichroism (XMCD) study performed at both the Co K edge and the Lu L{sub 2,3} edges on (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} systems. The XMCD spectra reflect the different magnetic character of these systems, allowing us to monitor the transition from weak to strong ferromagnetism. The XMCD at the Lu L{sub 2,3} edges indicates the existence of an ordered 5d moment at the lutetium sites that is coupled antiparallel to the Co moment. Estimates of the magnetic moment of Lu have been obtained by applying the XMCD sum rules. Our results show that there is a correlation between the Lu 5d-induced magnetic moment and the magnetic character of the (Y{sub y}Lu{sub 1-y})(Co{sub 1-x}Al{sub x}){sub 2} compounds. These results suggest that the developing of the Lu moment plays an important role in reinforcing the magnetic interactions and favoring the ferromagnetic character of the Lu-rich compounds.

  17. Methods of Using a Magnetic Field Response Sensor Within Closed, Electrically Conductive Containers

    NASA Technical Reports Server (NTRS)

    Woodward, Stanley E.; Taylor, Bryant D.

    2010-01-01

    Magnetic field response sensors are a class of sensors that are powered via oscillating magnetic fields, and when electrically active, respond with their own magnetic fields with attributes dependent upon the magnitude of the physical quantity being measured. A magnetic field response recorder powers and interrogates the magnetic sensors [see Magnetic-Field-Response Measurement- Acquisition System, NASA Tech Briefs Vol. 30, No, 6 (June 2006, page 28)]. Electrically conductive containers have low transmissivity for radio frequency (RF) energy and thus present problems for magnetic field response sensors. It is necessary in some applications to have a magnetic field response sensor s capacitor placed in these containers. Proximity to conductive surfaces alters the inductance and capacitance of the sensors. As the sensor gets closer to a conductive surface, the electric field and magnetic field energy of the sensor is reduced due to eddy currents being induced in the conductive surface. Therefore, the capacitors and inductors cannot be affixed to a conductive surface or embedded in a conductive material. It is necessary to have a fixed separation away from the conductive material. The minimum distance for separation is determined by the desired sensor response signal to noise ratio. Although the inductance is less than what it would be if it were not in proximity to the conductive surface, the inductance is fixed. As long as the inductance is fixed, all variations of the magnetic field response are due to capacitance changes. Numerous variations of inductor mounting can be utilized, such as providing a housing that provides separation from the conductive material as well as protection from impact damage. The sensor can be on the same flexible substrate with a narrow throat portion of the sensor between the inductor and the capacitor, Figure 1. The throat is of sufficient length to allow the capacitor to be appropriately placed within the container and the inductor

  18. Effects of orbit squeezing on ion transport processes close to magnetic axis

    SciTech Connect

    Shaing, K.C.; Hazeltine, R.D.; Zarnstorff, M.C.

    1997-01-01

    It is shown that ion thermal conductivity close to the magnetic axis in tokamaks is reduced by a factor of {vert_bar}S{vert_bar}{sup 5/3} if (M{sub i}/M{sub e}){sup 2/3}(T{sub e}/T{sub i}){sup 4/3}/{vert_bar}S{vert_bar}{sup 5/3} {much_gt} 1. Here, S is the orbit squeezing factor, M{sub i}(M{sub e}) is the ion (electron) mass, and T{sub i}(Te{sub e}) is the ion (electron) temperature. The reduction reflects both the increase of the fraction of trapped particles by a factor of {vert_bar}S{vert_bar}{sup 1/3}, and the decrease of the orbit size in units of the poloidal flux {psi} by a factor of {vert_bar}S{vert_bar}{sup 2/3}.

  19. Measurement of electric dipole moments at storage rings

    NASA Astrophysics Data System (ADS)

    Jörg Pretz JEDI Collaboration

    2015-11-01

    The electric dipole moment (EDM) is a fundamental property of a particle, like mass, charge and magnetic moment. What makes this property in particular interesting is the fact that a fundamental particle can only acquire an EDM via {P} and {T} violating processes. EDM measurements contribute to the understanding of the matter over anti-matter dominance in the universe, a question closely related to the violation of fundamental symmetries. Up to now measurements of EDMs have concentrated on neutral particles. Charged particle EDMs can be measured at storage ring. Plans at Forschungszentrum Jülich and results of first test measurements at the COoler SYnchrotron COSY will be presented.

  20. A measurement of the magnetic dipole moment of the. delta. /sup + +/(1232) from the bremsstrahlung process. pi. p. -->. pi. p. gamma

    SciTech Connect

    Meyer, C.A.

    1987-06-01

    We have measured the cross section from the bremsstrahlung process ..pi../sup +/p ..-->.. ..pi../sup +/p..gamma.. for incident pions of energy 299 MeV. We detected the out going pion in the angular range from 55 to 95/sup 0/ in the lab, and photons were detected near 240/sup 0/ in the lab. We compare this measured cross-section to the MIT theory in order to extract a measurement of the magnetic dipole moment of the ..delta../sup + +/(1232), ..mu../sub ..delta../. In order to compare our results with the MIT theory, we have folded the MIT theory into the acceptance of our apparatus. We find that for pion angles between 55 and 75/sup 0/ the theory gives us a dipole moment of: 2.3..mu../sub p/ < ..mu../sub ..delta../ < 3.3..mu../sup p/ where the quoted error arises from an experimental uncertainty of +-0.25..mu../sub p/ and from theoretical uncertainties of +-0.25 ..mu../sub p/. However, for pion angles between 75 and 95/sup 0/ we find that the MIT theory predicts a cross-section which is larger than our measured cross-section, and makes it difficult to extract a value of ..mu../sub ..delta../. This over prediction is not understood, but consistent with a similar effect when the MIT theory is fit to previous data. 78 figs., 29 tabs.

  1. Acceleration of plasma flows in the closed magnetic fields: Simulation and analysis

    SciTech Connect

    Mahajan, Swadesh M.; Shatashvili, Nana L.; Mikeladze, Solomon V.; Sigua, Ketevan I.

    2006-06-15

    Within the framework of a two-fluid description, possible pathways for the generation of fast flows (dynamical as well as steady) in the closed magnetic fields are established. It is shown that a primary plasma flow (locally sub-Alfvenic) is accelerated while interacting with ambient arcade-like closed field structures. The time scale for creating reasonably fast flows (> or approx. 100 km/s) is dictated by the initial ion skin depth, while the amplification of the flow depends on local plasma {beta}. It is shown that distances over which the flows become 'fast' are {approx}0.01R{sub 0} from the interaction surface (R{sub 0} being a characteristic length of the system); later, the fast flow localizes (with dimensions < or approx. 0.05R{sub 0}) in the upper central region of the original arcade. For fixed initial temperature, the final speed (> or approx. 500 km/s) of the accelerated flow and the modification of the field structure are independent of the time duration (lifetime) of the initial flow. In the presence of dissipation, these flows are likely to play a fundamental role in the heating of the finely structured stellar atmospheres; their relevance to the solar wind is also obvious.

  2. An assessment of the performance of the Spanwise Iron Magnet rolling moment generating system for magnetic suspension and balance systems using the finite element computer program GFUN

    NASA Technical Reports Server (NTRS)

    Britcher, C. P.

    1982-01-01

    The development of a powerful method of magnetic roll torque generation is essential before construction of a large magnetic suspension and balance system (LMSBS) can be undertaken. Some preliminary computed data concerning a relatively new dc scheme, referred to as the spanwise iron magnet scheme are presented. Computations made using the finite element computer program 'GFUN' indicate that adequate torque is available for at least a first generation LMSBS. Torque capability appears limited principally by current electromagnet technology.

  3. Electron's anomalous magnetic-moment effects on electron-hydrogen elastic collisions in the presence of a circularly polarized laser field

    SciTech Connect

    Elhandi, S.; Taj, S.; Attaourti, Y.; Manaut, B.; Oufni, L.

    2010-04-15

    The effect of the electron's anomalous magnetic moment on the relativistic electronic dressing for the process of electron-hydrogen atom elastic collisions is investigated. We consider a laser field with circular polarization and various electric field strengths. The Dirac-Volkov states taking into account this anomaly are used to describe the process in the first order of perturbation theory. The correlation between the terms coming from this anomaly and the electric field strength gives rise to the strong dependence of the spinor part of the differential cross section (DCS) with respect to these terms. A detailed study has been devoted to the nonrelativistic regime as well as the moderate relativistic regime. Some aspects of this dependence as well as the dynamical behavior of the DCS in the relativistic regime have been addressed.

  4. Hadron production in e+e- annihilation at BABAR, and implication for the muon anomalous magnetic moment

    SciTech Connect

    Porter, Frank C.

    2015-04-29

    The BABAR collaboration has an extensive program of studying hadronic cross sections in low-energy e+e- collisions, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for illuminating the current 3.6 sigma difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state. We report here the results of recent studies with final states that constitute the main contribution to the hadronic cross section in the energy region between 1 and 3 GeV, as e+e- → K+K-, π+π-, and e+e- → 4 hadrons

  5. ATOMIC AND MOLECULAR PHYSICS: Unique Magnetic Moment and Electronic Properties for Fe(MgO)n(n = 1-8) Clusters: First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Ge, Gui-Xian; Jing, Qun; Yang, Zeng-Qiang; Luo, You-Hua

    2009-08-01

    The geometries and electronic properties of Fe(MgO)n are systematically investigated by the density functional theory. The results show that the doped Fe atom is prone to bond with the O atom, and Fe almost does not disturb the frame of (MgO)n. The second-order energy difference, the fragmentation energies and the electron affinities show that Fe(MgO)4 and Fe(MgO)6 possess relatively higher stabilities. The HOMO-LUMO gaps of Fe(MgO)n decrease obviously as compared with (MgO)n. Almost equal unpaired electrons of the 3d state of the Fe atom in Fe(MgO)n result in a nearly equal magnetic moment of Fe(MgO)n.

  6. Magnetic order close to superconductivity in the iron-based layered LaO1-xFxFeAs systems

    SciTech Connect

    de la Cruz, Clarina; Huang, Q.; Lynn, J. W.; Li, Jiying; RatcliffIII, W; Zarestky, Jerel L.; Mook Jr, Herbert A; Chen, G. F,; Luo, J. L.; Wang, N. L.; Dai, Pengcheng

    2008-01-01

    Since the discovery of long-range antiferromagnetic (AF) order in the parent compounds of high-transition temperature (high-Tc) copper oxides,1,2 there have been tremendous efforts to understand the role of magnetism in the superconducting mechanism because superconductivity occurs when mobile electrons or holes are doped into the AF parent compounds. Much like high-Tc copper oxides, superconductivity in the newly discovered the rare-earth (R) ironbased oxide systems [ROFeAs] are derived from either electron3,4,5,6,7 or hole 8 doping of their nonsuperconducting parent compounds. The parent (nonsuperconducting)LaOFeAs material is metallic but shows anomalies near 150 K in both resistivity and dc magnetic susceptibility3. While optical conductivity and theoretical calculations suggest that LaOFeAs exhibits a spin-density-wave(SDW)instability that is suppressed by doping electrons to form superconductivity9, there has been no direct evidence of SDW order. Here we use neutron scattering to demonstrate that LaOFeAs undergoes an abrupt structural distortion below ~150 K, changing the symmetry from tetragonal (space group P4/nmm) to monoclinic (space group P112/n) at low temperatures, and then followed by the development of long range SDW-type AF order at ~137 K with a small moment but simple magnetic structure9. Doping the system with flourine suppresses both the magnetic order and structural distortion in favor of superconductivity. Therefore, much like high-Tc copper oxides, the superconducting regime in these Fe-based materials occurs in close proximity to a long-range ordered AF ground state.

  7. Itinerant electrons, local moments, and magnetic correlations in the pnictide superconductors CeFeAsO₁₋xFxand Sr(Fe₁₋xCox)₂As₂

    SciTech Connect

    Vilmercati, Paolo; Fedorov, Alexei; Bondino, Federica; Offi, Francesco; Panaccione, Giancarlo; Lacovig, Paolo; Simonelli, Laura; McGuire, Michael A.; Sefat, Athena S. M.; Mandrus, David; Sales, Brian C.; Egami, Takeshi; Ku, Wei; Mannella, Norman

    2012-06-15

    A direct and element-specific measurement of the local Fe spin moment has been provided by analyzing the Fe 3s core level photoemission spectra in the parent and optimally doped CeFeAsO₁₋xFx (x = 0, 0.11) and Sr(Fe₁₋xCox)2As2 (x = 0, 0.10) pnictides. The rapid time scales of the photoemission process allowed the detection of large local spin moments fluctuating on a 10⁻¹⁵ s time scale in the paramagnetic, antiferromagnetic, and superconducting phases, indicative of the occurrence of ubiquitous strong Hund's magnetic correlations. The magnitude of the spin moment is found to vary significantly among different families, 1.3μB in CeFeAsO and 2.1μB in SrFe₂As₂. Surprisingly, the spin moment is found to decrease considerably in the optimally doped samples, 0.9μB in CeFeAsO₀.₈₉F₀.₁₁ and 1.3μB in Sr(Fe₀.₉Co₀.₁)₂As₂. The strong variation of the spin moment against doping and material type indicates that the spin moments and the motion of itinerant electrons are influenced reciprocally in a self-consistent fashion, reflecting the strong competition between the antiferromagnetic superexchange interaction among the spin moments and the kinetic energy gain of the itinerant electrons in the presence of a strong Hund's coupling. By describing the evolution of the magnetic correlations concomitant with the appearance of superconductivity, these results constitute a fundamental step toward attaining a correct description of the microscopic mechanisms shaping the electronic properties in the pnictides, including magnetism and high-temperature superconductivity.

  8. A compact high-voltage pulse generator based on pulse transformer with closed magnetic core.

    PubMed

    Zhang, Yu; Liu, Jinliang; Cheng, Xinbing; Bai, Guoqiang; Zhang, Hongbo; Feng, Jiahuai; Liang, Bo

    2010-03-01

    A compact high-voltage nanosecond pulse generator, based on a pulse transformer with a closed magnetic core, is presented in this paper. The pulse generator consists of a miniaturized pulse transformer, a curled parallel strip pulse forming line (PFL), a spark gap, and a matched load. The innovative design is characterized by the compact structure of the transformer and the curled strip PFL. A new structure of transformer windings was designed to keep good insulation and decrease distributed capacitance between turns of windings. A three-copper-strip structure was adopted to avoid asymmetric coupling of the curled strip PFL. When the 31 microF primary capacitor is charged to 2 kV, the pulse transformer can charge the PFL to 165 kV, and the 3.5 ohm matched load can deliver a high-voltage pulse with a duration of 9 ns, amplitude of 84 kV, and rise time of 5.1 ns. When the load is changed to 50 ohms, the output peak voltage of the generator can be 165 kV, the full width at half maximum is 68 ns, and the rise time is 6.5 ns.

  9. The Influence of Magnetic Field Geometry on the Formation of Close-in Exoplanets

    NASA Astrophysics Data System (ADS)

    Simon, Jacob B.

    2016-08-01

    Approximately half of Sun-like stars harbor exoplanets packed within a radius of ˜0.3 au, but the formation of these planets and why they form in only half of known systems are still not well understood. We employ a one-dimensional steady-state model to gain physical insight into the origin of these close-in exoplanets. We use Shakura & Sunyaev α values extracted from recent numerical simulations of protoplanetary disk accretion processes in which the magnitude of α, and thus the steady-state gas surface density, depend on the orientation of large-scale magnetic fields with respect to the disk’s rotation axis. Solving for the metallicity as a function of radius, we find that for fields anti-aligned with the rotation axis, the inner regions of our model disk often fall within a region of parameter space that is not suitable for planetesimal formation, whereas in the aligned case, the inner disk regions are likely to produce planetesimals through some combination of streaming instability and gravitational collapse, though the degree to which this is true depends on the assumed parameters of our model. More robustly, the aligned field case always produces higher concentrations of solids at small radii compared to the anti-aligned case. In the in situ formation model, this bimodal distribution of solid enhancement leads directly to the observed dichotomy in exoplanet orbital distances.

  10. Third Elementary Dipole Moment: Toroidal

    NASA Astrophysics Data System (ADS)

    Cordrey, Vincent; Eshete, Amanuel; Majewski, Walerian

    2015-04-01

    In this paper we study the generally unknown characteristics of toroids, magnets without magnetic poles. Toroids have never seemed interesting enough to be studied for their physical features in labs due to the fact that they have no magnetic fields on the outside, but rather a very strong magnetic field trapped inside. Toroidal solenoids or magnets (rings magnetized circumferentially) interact with the external magnetic field only through its curl, which can be created either by an electric current, or by a time-dependent electric flux. We confirmed a theoretical prediction, that a toroid would not interact with the curl-less magnetic field of a current-carrying wire running outside of the torus's hole. We used our toroids as magnetic curlmeters, measuring the torque on the toroid, when the current-carrying wire runs through the toroid. From this torque we found the toroidal dipole moment. We are experimenting on detecting the escape of the inner magnetic field of the toroid outside of it, when magnetic toroid rotates or when electric toroid is driven by AC voltage. We also will discuss toroidal (or anapole) moments of fundamental particles, nuclei and atoms, and toroids' applications in metamaterials.

  11. Construction and calibration of a 12 T pulsed magnet integrated with a 4 K closed-cycle refrigerator.

    PubMed

    Murthy, O V S N; Venkataraman, V

    2007-11-01

    A low cost 12 T pulsed magnet system has been integrated with a closed-cycle helium refrigerator for performing magnetotransport measurements. Minimal delay between pulses and ac current excitation with software lock-in to reduce noise enables quick but accurate measurements to be performed at temperatures of 4-300 K up to 12 T. An additional pulsed magnet operating with a liquid nitrogen cryostat extends the range up to 19 T. The instrument has been calibrated against a commercial superconducting magnet by comparing quantum Hall effect data in a p-channel SiGe/Si heterostructure, and common issues arising out of pulsed magnet usage have been addressed. The versatility of the system is demonstrated through magnetotransport measurements in a variety of samples such as heterostructures, narrow gap semiconductors, and those exhibiting giant magnetoresistance.

  12. Determination of the optimal first-order gradient moment for flow-sensitive dephasing magnetization-prepared 3D noncontrast MR angiography.

    PubMed

    Fan, Zhaoyang; Zhou, Xiangzhi; Bi, Xiaoming; Dharmakumar, Rohan; Carr, James C; Li, Debiao

    2011-04-01

    Flow-sensitive dephasing (FSD) magnetization preparation has been developed for black-blood vessel wall MRI and noncontrast MR angiography. The first-order gradient moment, m(1) , is a measure of the flow-sensitization imparted by an FSD preparative module. Determination of the optimal m(1) for each individual is highly desirable for FSD-prepared MR angiography. This work developed a 2D m(1)-scouting method that evaluates a range of m(1) values for their effectiveness in blood signal suppression in a single scan. The feasibility of using the 2D method to predict blood signal suppression in 3D FSD-prepared imaging was validated on a flow phantom and the popliteal arteries of 5 healthy volunteers. Excellent correlation of the blood signal measurements between the 2D scouting and 3D FSD imaging was obtained. Therefore, the optimal m(1) determined from the 2D m(1)-scouting scan may be directly translated to 3D FSD-prepared imaging. In vivo studies of additional 10 healthy volunteers and 2 patients have demonstrated the proposed method can help significantly improve the signal performance of FSD MR angiography, indicating its potential to enhance diagnostic confidence. Further systematic studies in patients are warranted to evaluate its clinical value.

  13. Impurity-induced magnetic moments on the graphene-lattice Hubbard model: An inhomogeneous cluster dynamical mean-field theory study

    NASA Astrophysics Data System (ADS)

    Charlebois, M.; Sénéchal, D.; Gagnon, A.-M.; Tremblay, A.-M. S.

    2015-01-01

    Defect-induced magnetic moments are at the center of the research effort on spintronic applications of graphene. Here, we study the problem of a nonmagnetic impurity in graphene with a new theoretical method, inhomogeneous cluster dynamical mean-field theory (I-CDMFT), which takes into account interaction-induced short-range correlations while allowing long-range inhomogeneities. The system is described by a Hubbard model on the honeycomb lattice. The impurity is modeled by a local potential. For a large enough potential, interactions induce local antiferromagnetic correlations around the impurity and a net total spin 1/2 appears, in agreement with Lieb's theorem. Bound states caused by the impurity are visible in the local density of states (LDOS) and have their energies shifted by interactions in a spin-dependent way, leading to the antiferromagnetic correlations. Our results take into account dynamical correlations; nevertheless they qualitatively agree with previous mean-field and density functional theory (DFT) studies. Moreover, they provide a relation between impurity potential and on-site repulsion U that could in principle be used to determine experimentally the value of U .

  14. Predictive Capability for Strongly Correlated Systems: Mott Transition in MnO, Multielectron Magnetic Moments, and Dynamics Effects in Correlated Materials

    SciTech Connect

    Krakauer, Henry; Zhang, Shiwei

    2013-02-21

    There are classes of materials that are important to DOE and to the science and technology community, generically referred to as strongly correlated electron systems (SCES), which have proven very difficult to understand and to simulate in a material-specific manner. These range from actinides, which are central to the DOE mission, to transition metal oxides, which include the most promising components of new spin electronics applications as well as the high temperature superconductors, to intermetallic compounds whose heavy fermion characteristics and quantum critical behavior has given rise to some of the most active areas in condensed matter theory. The objective of the CMSN cooperative research team was to focus on the application of these new methodologies to the specific issue of Mott transitions, multi-electron magnetic moments, and dynamical properties correlated materials. Working towards this goal, the W&M team extended its first-principles phaseless auxiliary-field quantum Monte Carlo (AFQMC) method to accurately calculate structural phase transitions and excited states.

  15. MAGNETIC RECONNECTION: FROM 'OPEN' EXTREME-ULTRAVIOLET LOOPS TO CLOSED POST-FLARE ONES OBSERVED BY SDO

    SciTech Connect

    Zhang, Jun; Yang, Shuhong; Li, Ting; Zhang, Yuzong; Li, Leping; Jiang, Chaowei E-mail: shuhongyang@nao.cas.cn E-mail: yuzong@nao.cas.cn E-mail: cwjiang@spaceweather.ac.cn

    2013-10-10

    We employ Solar Dynamics Observatory observations and select three well-observed events including two flares and one extreme-ultraviolet (EUV) brightening. During the three events, the EUV loops clearly changed. One event was related to a major solar flare that took place on 2012 July 12 in active region NOAA AR 11520. 'Open' EUV loops rooted in a facula of the AR deflected to the post-flare loops and then merged with them while the flare ribbon approached the facula. Meanwhile, 'open' EUV loops rooted in a pore disappeared from top to bottom as the flare ribbon swept over the pore. The loop evolution was similar in the low-temperature channels (e.g., 171 Å) and the high-temperature channels (e.g., 94 Å). The coronal magnetic fields extrapolated from the photospheric vector magnetograms also show that the fields apparently 'open' prior to the flare become closed after it. The other two events were associated with a B1.1 flare on 2010 May 24 and an EUV brightening on 2013 January 03, respectively. During both of these two events, some 'open' loops either disappeared or darkened before the formation of new closed loops. We suggest that the observations reproduce the picture predicted by the standard magnetic reconnection model: 'open' magnetic fields become closed due to reconnection, manifesting as a transformation from 'open' EUV loops to closed post-flare ones.

  16. Electromagnetic moments of quasistable particle

    SciTech Connect

    Ledwig, Tim; Pascalutsa, Vladimir; Vanderhaeghen, Marc

    2010-11-01

    We deal with the problem of assigning electromagnetic moments to a quasistable particle (i.e., a particle with mass located at the particle's decay threshold). In this case, an application of a small external electromagnetic field changes the energy in a nonanalytic way, which makes it difficult to assign definitive moments. On the example of a spin-1/2 field with mass M{sub *} interacting with two fields of masses M and m, we show how a conventionally defined magnetic dipole moment diverges at M{sub *}=M+m. We then show that the conventional definition makes sense only when the values of the applied magnetic field B satisfy |eB|/2M{sub *}<<|M{sub *}-M-m|. We discuss implications of these results to existing studies in electroweak theory, chiral effective-field theory, and lattice QCD.

  17. Scalar relaxation of the second kind - a potential source of information on the dynamics of molecular movements. 2. Magnetic dipole moments and magnetic shielding of bromine nuclei.

    PubMed

    Gryff-Keller, Adam; Molchanov, Sergey; Wodyński, Artur

    2014-01-01

    In this paper, we continue the exploration of possibilities, limitations, and methodological problems of the studies based on measurements of the nuclear spin relaxation rates running via the scalar relaxation of the second kind (SC2) mechanism. The attention has been focused on the (13)C-(79)Br and (13)C-(81)Br systems in organic bromo compounds, which are characterized by exceptionally small differences of Larmor frequencies, ΔωCBr, of the coupled nuclei. This unique property enables experimental observation of longitudinal SC2 relaxation of (13)C nuclei, which makes investigation of the SC2 relaxation rates an attractive experimental method of determination of spin-spin coupling constants and relaxation rates of quadrupole bromine nuclei, both types of parameters being hardly accessible by direct measurements. A careful examination of the methodology used in SC2 relaxation studies of carbon-bromine systems reveals, however, some disturbing facts that could burden the results with systematic inaccuracies. Namely, the way of calculating the Larmor frequency differences between (13)C and bromine isotopes, ΔωCBr, may cause some reservations. In this work, the values of (79)Br and (81)Br magnetogyric ratios have been rechecked using bromine NMR data for the KBr·Kryptofix 222 complex in acetonitrile solution and the results of the advanced calculations of the magnetic shielding of the bromine nucleus in the Br(-) anion. Moreover, it has been pointed out that in the case of (13)C-(79)Br, the magnetic shielding of the bromine nucleus in the investigated molecule must not be neglected during the calculation of the ΔωCBr parameter. Some recommendations concerning the exploitation of available theoretical methods to calculate bromine shielding constants for bromo compounds have also been formulated, keeping in mind relativistic effects.

  18. Shielding of longitudinal magnetic fields with thin, closely, spaced concentric cylindrical shells with applications to atomic clocks

    NASA Technical Reports Server (NTRS)

    Wolf, S. A.; Gubser, D. U.; Cox, J. E.

    1978-01-01

    A general formula is given for the longitudinal shielding effectiveness of N closed concentric cylinders. The use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental results on three sets of shields fabricated by three manufacturers are presented. Two of the sets were designed employing the techniques described. Agreement between the experimental results and the design calculations is then demonstrated.

  19. Magnetic structure and frequency scaling of limit-cycle oscillations close to L- to H-mode transitions

    NASA Astrophysics Data System (ADS)

    Birkenmeier, G.; Cavedon, M.; Conway, G. D.; Manz, P.; Stroth, U.; Fischer, R.; Fuchert, G.; Happel, T.; Laggner, F. M.; Maraschek, M.; Medvedeva, A.; Nikolaeva, V.; Prisiazhniuk, D.; Pütterich, T.; Ryter, F.; Shao, L. M.; Willensdorfer, M.; Wolfrum, E.; Zohm, H.; the ASDEX Upgrade Team

    2016-08-01

    Limit-cycle oscillations (LCOs) close to the power threshold of L- to H-mode transitions are investigated in plasmas of ASDEX Upgrade. During this phase, referred to as I-phase, a strong magnetic activity in the poloidal magnetic field {{\\overset{\\centerdot}{{B}} }θ} with an up–down asymmetry is found. In some cases, the regular LCOs during I-phase transition smoothly into a phase with intermittent bursts which have similar properties to type-III edge localised modes (ELMs). Indications of precursors during the intermittent phase as well as in the regular LCO phase point to a common nature of the I-phase and type-III ELMs. The LCO frequency measured in a set of discharges with different plasma currents and magnetic fields scales as f∼ ≤ft(B\\text{t}1/2I\\text{p}3/2\\right)/(nT) .

  20. Relativistic unitary coupled-cluster study of the electric quadrupole moment and magnetic dipole hyperfine constants of {sup 199}Hg{sup +}

    SciTech Connect

    Sur, Chiranjib; Chaudhuri, Rajat K.

    2007-09-15

    Searching for an accurate optical clock which can serve as a better time standard than the present-day atomic clock is highly demanding from several areas of science and technology. Several attempts have been made to build more accurate clocks with different ion species. In this paper, we discuss the electric quadrupole and hyperfine shifts in the 5d{sup 9}6s{sup 2} {sup 2}D{sub 5/2}(F=0,m{sub F}=0){r_reversible}5d{sup 10}6s {sup 2}S{sub 1/2}(F=2,m{sub F}=0) clock transition in {sup 199}Hg{sup +}, one of the most promising candidates for next-generation optical clocks. We have applied Fock-space unitary coupled-cluster theory to study the electric quadrupole moment of the 5d{sup 9}6s{sup 2} {sup 2}D{sub 5/2} state and magnetic dipole hyperfine constants of 5d{sup 9}6s{sup 2} {sup 2}D{sub 3/2,5/2} and 5d{sup 10}6s{sup 1} {sup 2}S{sub 1/2} states, respectively, of {sup 199}Hg{sup +}. We have also compared our results with available data. To the best of our knowledge, this is the first time a variant of coupled-cluster theories has been applied to study these kinds of properties of Hg{sup +} and is the most accurate estimate of these quantities to date.

  1. Investigation of measurement distortion and application of finite element modeling to magnetic material characterization in a closed-circuit

    NASA Astrophysics Data System (ADS)

    Pugh, Barry Kevin

    While open-circuit magnetic measurements are noted to involve distortions related to the image effect and, most significantly, the sample's demagnetizing factor, closed-circuit measurements are generally considered to be free of these distortions. However, it has been reported and observed within this research that for certain sample geometries and materials operating near the magnetic saturation of the electromagnet poles, there are observed distortions of up to 40.7% of the maximum magnetization at a field level of 25 kiloOersteds for a cylindrical sample with an L/D ratio of 0.2. This observed distortion in the magnetic measurement in a closed-circuit has been referred to in the literature as an "apparent image effect" error. The intent of this research is to apply finite element modeling (FEM) to replicate original experimental and published data for cylindrical samples of both hard and soft magnetic material and to observe the phenomenology of the error within the results of the model. The hard magnetic material of interest is NdFeB and the soft magnetic material used is 1018 steel. Additionally, the sample data base is extended to rectangular prisms with data generated both experimentally and with FEM. Using a validated model it is possible to develop a corrective methodology and equations to address the magnetization measurement errors noted at high field levels within both the first and third quadrants of the hysteresis curve. The methodology developed through this research produced corrective surfaces with two dimensional polynomial fits with average adjusted R-values of 0.97. As a fault study secondary to the development of the corrective methodology, this project investigated the significance of the sample's surface mating to the poles of the hysteresigraph. It was determined that a 5° partial misalignment air gap has only approximately 0.5% variation in magnetization, 4thMmax, from the baseline of an ungapped sample. It is indicated that the sample gap

  2. A uniform parametrization of moment tensors

    NASA Astrophysics Data System (ADS)

    Tape, Walter; Tape, Carl

    2015-09-01

    A moment tensor is a 3 × 3 symmetric matrix that expresses an earthquake source. We construct a parametrization of the 5-D space of all moment tensors of unit norm. The coordinates associated with the parametrization are closely related to moment tensor orientations and source types. The parametrization is uniform, in the sense that equal volumes in the coordinate domain of the parametrization correspond to equal volumes of moment tensors. Uniformly distributed points in the coordinate domain therefore give uniformly distributed moment tensors. A cartesian grid in the coordinate domain can be used to search efficiently over moment tensors. We find that uniformly distributed moment tensors have uniformly distributed orientations (eigenframes), but that their source types (eigenvalue triples) are distributed so as to favour double couples.

  3. Theoretical analysis of resonance conditions in magnetized plasmas when the plasma/gyro frequency ratio is close to an integer

    NASA Astrophysics Data System (ADS)

    Osherovich, V. A.; Fainberg, J.; Benson, R. F.; Stone, R. G.

    1997-12-01

    We study cylindrical oscillations of electrons in a plasma where the background magnetic field is parallel to the axis of a cylinder and the ion background is taken to have a constant positive density. Assuming self-similarity, we reduce the problem to two second order nonlinear differential equations, relating fluctuations of electron density and fluctuations of magnetic field. The system studied is shown to have two fundamental frequencies. In the linear domain, these frequencies correspond to the Z and X cold plasma wave cutoff frequencies (R = 0 and L = 0 conditions in the notation of Stix (1992), respectively). Thus they differ by the gyrofrequency. In the nonlinear domain, these frequencies change and resonances at harmonics and at the sum and difference frequencies appear. When the plasma/gyro frequency ratio is close to an integer, our results indicate special resonance conditions which are characterized by an increase of the amplitude and a narrowing of the fundamental resonances.

  4. Closed bore XMR (CBXMR) systems for aortic valve replacement: active magnetic shielding of x-ray tubes.

    PubMed

    Bracken, John A; DeCrescenzo, Giovanni; Komljenovic, Philip; Lillaney, Prasheel V; Fahrig, Rebecca; Rowlands, J A

    2009-05-01

    Hybrid closed bore x-ray/MRI systems are being developed to improve the safety and efficacy of percutaneous aortic valve replacement procedures by harnessing the complementary strengths of the x-ray and MRI modalities in a single interventional suite without requiring patient transfer between two rooms. These systems are composed of an x-ray C-arm in close proximity (approximately 1 m) to an MRI scanner. The MRI magnetic fringe field can cause the electron beam in the x-ray tube to deflect. The deflection causes the x-ray field of view to shift position on the detector receptacle. This could result in unnecessary radiation exposure to the patient and the staff in the cardiac catheterization laboratory. Therefore, the electron beam deflection must be corrected. The authors developed an active magnetic shielding system that can correct for electron beam deflection to within an accuracy of 5% without truncating the field of view or increasing exposure to the patient. This system was able to automatically adjust to different field strengths as the external magnetic field acting on the x-ray tube was changed. Although a small torque was observed on the shielding coils of the active shielding system when they were placed in a magnetic field, this torque will not impact their performance if they are securely mounted on the x-ray tube and the C-arm. The heating of the coils of the shielding system for use in the clinic caused by electric current was found to be slow enough not to require a dedicated cooling system for one percutaneous aortic valve replacement procedure. However, a cooling system will be required if multiple procedures are performed in one session. PMID:19544789

  5. Closed bore XMR (CBXMR) systems for aortic valve replacement: Active magnetic shielding of x-ray tubes

    PubMed Central

    Bracken, John A.; DeCrescenzo, Giovanni; Komljenovic, Philip; Lillaney, Prasheel V.; Fahrig, Rebecca; Rowlands, J. A.

    2009-01-01

    Hybrid closed bore x-ray∕MRI systems are being developed to improve the safety and efficacy of percutaneous aortic valve replacement procedures by harnessing the complementary strengths of the x-ray and MRI modalities in a single interventional suite without requiring patient transfer between two rooms. These systems are composed of an x-ray C-arm in close proximity (≈1 m) to an MRI scanner. The MRI magnetic fringe field can cause the electron beam in the x-ray tube to deflect. The deflection causes the x-ray field of view to shift position on the detector receptacle. This could result in unnecessary radiation exposure to the patient and the staff in the cardiac catheterization laboratory. Therefore, the electron beam deflection must be corrected. The authors developed an active magnetic shielding system that can correct for electron beam deflection to within an accuracy of 5% without truncating the field of view or increasing exposure to the patient. This system was able to automatically adjust to different field strengths as the external magnetic field acting on the x-ray tube was changed. Although a small torque was observed on the shielding coils of the active shielding system when they were placed in a magnetic field, this torque will not impact their performance if they are securely mounted on the x-ray tube and the C-arm. The heating of the coils of the shielding system for use in the clinic caused by electric current was found to be slow enough not to require a dedicated cooling system for one percutaneous aortic valve replacement procedure. However, a cooling system will be required if multiple procedures are performed in one session. PMID:19544789

  6. Effects and Correction of Closed Orbit Magnet Errors in the SNS Ring

    SciTech Connect

    Bunch, S.C.; Holmes, J.

    2004-01-01

    We consider the effect and correction of three types of orbit errors in SNS: quadrupole displacement errors, dipole displacement errors, and dipole field errors. Using the ORBIT beam dynamics code, we focus on orbit deflection of a standard pencil beam and on beam losses in a high intensity injection simulation. We study the correction of these orbit errors using the proposed system of 88 (44 horizontal and 44 vertical) ring beam position monitors (BPMs) and 52 (24 horizontal and 28 vertical) dipole corrector magnets. Correction is carried out numerically by adjusting the kick strengths of the dipole corrector magnets to minimize the sum of the squares of the BPM signals for the pencil beam. In addition to using the exact BPM signals as input to the correction algorithm, we also consider the effect of random BPM signal errors. For all three types of error and for perturbations of individual magnets, the correction algorithm always chooses the three-bump method to localize the orbit displacement to the region between the magnet and its adjacent correctors. The values of the BPM signals resulting from specified settings of the dipole corrector kick strengths can be used to set up the orbit response matrix, which can then be applied to the correction in the limit that the signals from the separate errors add linearly. When high intensity calculations are carried out to study beam losses, it is seen that the SNS orbit correction system, even with BPM uncertainties, is sufficient to correct losses to less than 10-4 in nearly all cases, even those for which uncorrected losses constitute a large portion of the beam.

  7. Moment-to-Moment Emotions during Reading

    ERIC Educational Resources Information Center

    Graesser, Arthur C.; D'Mello, Sidney

    2012-01-01

    Moment-to-moment emotions are affective states that dynamically change during reading and potentially influence comprehension. Researchers have recently identified these emotions and the emotion trajectories in reading, tutoring, and problem solving. The primary learning-centered emotions are boredom, frustration, confusion, flow (engagement),…

  8. Doubly charged Higgsino contribution to the decays {mu}{r_arrow}e{gamma} and {mu}{r_arrow}3e and to the anomalous magnetic moment of the muon {Delta}a{sub {mu}} within the left-right supersymmetric model

    SciTech Connect

    Couture, G.; Koenig, H.; Frank, M.; Koenig, H.

    1997-10-01

    We present a detailed and complete calculation of the doubly charged Higgsino contribution to the decays {mu}{r_arrow}e{gamma} and {mu}{r_arrow}3e and to the anomalous magnetic moment of the muon {Delta}a{sub {mu}} within the left-right supersymmetric model. We include the mixing of the scalar partners of the left- and right-handed leptons, and show that it leads to a strong enhancement of the decay modes in certain scenarios. We find that the contribution of the doubly charged Higgsino can be close to the known experimental values and is reachable by future experiments. {copyright} {ital 1997} {ital The American Physical Society}

  9. Specific features of spontaneous reorientation of the magnetic moment in a single-crystal thin plate of the iron garnet Tb0.2Y2.8Fe5O12

    NASA Astrophysics Data System (ADS)

    Niyazov, L. N.; Sokolov, B. Yu.; Sharipov, M. Z.

    2012-09-01

    The Faraday effect, light scattering, and changes in the domain structure of a single-crystal thin plate of the iron garnet Tb0.2Y2.8Fe5O12 cut parallel to the (110) crystallographic plane have been experimentally investigated in the temperature range of the spontaneous magnetic orientational phase transition. It has been established that the transformation of the domain structure of the studied sample due to the orientational phase transition is accompanied by a significant temperature hysteresis. A model of the spontaneous reorientation of the magnetic moment vector of the crystal has been proposed by analyzing the results of visual observations of the domain structure and the temperature dependences of the Faraday effect and light scattering. In the proposed model, preference is given to the spin wave mechanism of nucleation of domains of the equilibrium magnetic phases.

  10. Closing the spin gap in the Kondo insulator Ce3Bi4Pt3 at high magnetic fields

    PubMed

    Jaime; Movshovich; Stewart; Beyermann; Berisso; Hundley; Canfield; Sarrao

    2000-05-11

    Kondo insulator materials--such as CeRhAs, CeRhSb, YbB12, Ce3Bi4Pt3 and SmB6--are 3d, 4f and 5f intermetallic compounds that have attracted considerable interest in recent years. At high temperatures, they behave like metals. But as temperature is reduced, an energy gap opens in the conduction band at the Fermi energy and the materials become insulating. This contrasts with other f-electron compounds, which are metallic at all temperatures. The formation of the gap in Kondo insulators has been proposed to be a consequence of hybridization between the conduction band and the f-electron levels, giving a 'spin' gap. If this is indeed the case, metallic behaviour should be recovered when the gap is closed by changing external parameters, such as magnetic field or pressure. Some experimental evidence suggests that the gap can be closed in SmB6 (refs 5, 8) and YbB12 (ref. 9). Here we present specific-heat measurements of Ce3Bi4Pt3 in d.c. and pulsed magnetic fields up to 60 tesla. Numerical results and the analysis of our data using the Coqblin-Schrieffer model demonstrate unambiguously a field-induced insulator-to-metal transition. PMID:10821266

  11. A DETERMINATION OF THE NORTH–SOUTH HELIOSPHERIC MAGNETIC FIELD COMPONENT FROM INNER CORONA CLOSED-LOOP PROPAGATION

    SciTech Connect

    Jackson, B. V.; Hick, P. P.; Buffington, A.; Yu, H.-S.; Bisi, M. M.; Tokumaru, M.; Zhao, X. E-mail: pphick@ucsd.edu E-mail: hsyu@ucsd.edu

    2015-04-10

    A component of the magnetic field measured in situ near the Earth in the solar wind is present from north–south fields from the low solar corona. Using the Current-sheet Source Surface model, these fields can be extrapolated upward from near the solar surface to 1 AU. Global velocities inferred from a combination of interplanetary scintillation observations matched to in situ velocities and densities provide the extrapolation to 1 AU assuming mass and mass flux conservation. The north–south field component is compared with the same ACE in situ magnetic field component—the Normal (Radial Tangential Normal) Bn coordinate—for three years throughout the solar minimum of the current solar cycle. We find a significant positive correlation throughout this period between this method of determining the Bn field compared with in situ measurements. Given this result from a study during the latest solar minimum, this indicates that a small fraction of the low-coronal Bn component flux regularly escapes from closed field regions. The prospects for Space Weather, where the knowledge of a Bz field at Earth is important for its geomagnetic field effects, is also now enhanced. This is because the Bn field provides the major portion of the Geocentric Solar Magnetospheric Bz field coordinate that couples most closely to the Earth’s geomagnetic field.

  12. Relativistic corrections to the nuclear Schiff moment

    SciTech Connect

    Dmitriev, V.F.; Flambaum, V.V.

    2005-06-01

    Parity- and time-invariance-violating (P,T-odd) atomic electric dipole moments (EDM) are induced by the interaction between atomic electrons and nuclear P,T-odd moments, which are themselves produced by P,T-odd nuclear forces. The nuclear EDM is screened by atomic electrons. The EDM of a nonrelativistic atom with closed electron subshells is induced by the nuclear Schiff moment. For heavy relativistic atoms EDM is induced by the nuclear local dipole moments, which differ by 10-50% from the Schiff moments calculated previously. We calculate the local dipole moments for {sup 199}Hg and {sup 205}Tl where the most accurate atomic [Romalis et al., Phys. Rev. Lett. 86, 2505 (2001)] and molecular [Cho et al., Phys. Rev. Lett. 63, 2559 (1989); Phys. Rev. A 44, 2783 (1991)] EDM measurements have been performed.

  13. Determination of magnetic-field components from inner-corona closed-loop propagation and IPS analysis

    NASA Astrophysics Data System (ADS)

    Jackson, Bernard; Tokumaru, Munetoshi; Gonzalez-Esparza, Americo; Hick, P.; Buffington, Andrew; Hong, Sunhak; Bisi, Mario M.; Kim, Jaehun; Yu, Hsiu-Shan

    2016-07-01

    We find that a portion of the interplanetary magnetic field measured in situ near Earth is present from a direct outward mapping of closed fields from the low solar corona. The Current-Sheet Source Surface (CSSS) model (Zhao & Hoeksema, 1995 JGR 100, 19), extrapolate magnetogram-derived fields upward from near the solar surface. Global velocities and densities inferred from a combination of observations of interplanetary scintillation (IPS), matched to in-situ velocities and densities measured by spacecraft instrumentation, then provide an accurate outward timing to 1 AU using the UCSD tomography model that assumes conservation of mass and mass flux. All three field components at 1 AU are present including the north-south (or Bn) component field, and are compared with the appropriate ACE magnetometer in-situ (RTN) field coordinate. A significant positive daily correlation variation sometimes as high as 0.8 exists between these closed loop components and those determined by in-situ measurement over the last ten years for individual Carrington rotations. We determine that a consistent small fraction of the static low-coronal component flux (˜2%), that includes the Bn component, regularly escapes from closed-field regions. However, this percentage of closed projected fields relative to those measured in situ at Earth varies somewhat, indicating that a more efficient process for this flux propagation exists at the peak of the solar cycle than at its minimum. Since the Bn field provides the major portion of the Geocentric Solar Magnetospheric (GSM) Bz field component that couples most closely to the Earth's geomagnetic field, the prospects of using this technique for space weather predictions are being actively developed.

  14. The classical model for moment tensors

    NASA Astrophysics Data System (ADS)

    Tape, W.; Tape, C.

    2013-12-01

    A seismic moment tensor is a description of an earthquake source, but the description is indirect. The moment tensor describes seismic radiation rather than the actual physical process that initiates the radiation. A moment tensor 'model' then ties the physical process to the moment tensor. The model is not unique, and the physical process is therefore not unique. In the classical moment tensor model (Aki and Richards, 1980), an earthquake arises from slip along a planar fault, but with the slip not necessarily in the plane of the fault. The model specifies the resulting moment tensor in terms of the slip vector, the fault normal vector, and the Lame elastic parameters, assuming isotropy. We review the classical model in the context of the fundamental lune. The lune is closely related to the space of moment tensors, and it provides a setting that is conceptually natural as well as pictorial. In addition to the classical model, we consider a crack plus double couple model (CDC model) in which a moment tensor is regarded as the sum of a crack tensor and a double couple. A compilation of full moment tensors from the literature reveals large deviations in Poisson's ratio as implied by the classical model. Either the classical model is inadequate or the published full moment tensors have very large uncertainties. We question the common interpretation of the isotropic component as a volume change in the source region.

  15. Determination of the North-South Heliospheric Magnetic-Field Component from Inner-Corona Closed-Loop Propagation

    NASA Astrophysics Data System (ADS)

    Jackson, B. V.; Yu, H. S.; Hick, P. P.; Buffington, A.; Bisi, M. M.; Tokumaru, M.; Kim, J.; Hong, S.; Lee, B.; Yi, J.; Yun, J.

    2015-12-01

    We find that a portion of the north-south interplanetary magnetic field measured in situ near Earth is present from a direct outward mapping of closed fields from the low solar corona. Using the Current-Sheet Source Surface (CSSS) model (Zhao & Hoeksema, 1995 JGR 100, 19), these lower coronal fields are extrapolated upward from near the solar surface. Global velocities inferred from a combination of observations of interplanetary scintillation (IPS) matched to in-situ velocities and densities measured by spacecraft instrumentation provide an accurate outward timing to 1 AU from a model assuming conservation of mass and mass flux. The north-south field component at 1 AU is compared with the appropriate ACE magnetometer in-situ Normal (RTN) or Bn field coordinate (Jackson et al., 2015, ApJL, 803:L1). From a significant positive correlation between this method of determining the Bn field compared with in-situ measurements over a three-year period during the last solar minimum, we find that a small fraction of the low-coronal Bn component flux (~1%) regularly escapes from closed-field regions. Since the Bn field provides the major portion of the Geocentric Solar Magnetospheric (GSM) Bz field component that couples most closely to the Earth's geomagnetic field, the prospects for its determination using this technique for space weather use are being actively developed by our many colleague groups.

  16. Ab initio calculations of NMR shielding of Sc3+, Y3+ and La3+ ions in the water solution and 45Sc, 89Y, 138La and 139La nuclear magnetic dipole moments

    NASA Astrophysics Data System (ADS)

    Antušek, Andrej; Šulka, Martin

    2016-09-01

    Ab initio calculations of NMR shielding constants for water solvated trivalent scandium, yttrium and lanthanum cations are presented. The solvent effects of the first solvation shell are calculated explicitly using coupled cluster theory. The relativistic correction is calculated at non-correlated level. The influence of the second solvation shell is estimated at DFT level. The final NMR shielding constants define new NMR absolute shielding scales of scandium, yttrium and lanthanum and these shieldings were used for re-derivation of the nuclear magnetic dipole moments, eliminating long standing errors of ≈ 0.005μN .

  17. Role of anion size, magnetic moment, and disorder on the properties of the organic conductor κ-(BETS)2Ga1-xFexCl4-yBry

    NASA Astrophysics Data System (ADS)

    Steven, E.; Cui, H. B.; Kismarahardja, A.; Brooks, J. S.; Graf, D.; Kobayashi, H.

    2010-06-01

    Shubnikov-de Haas and angular dependent magnetoresistance oscillations have been used to explore the role of anion size, magnetic moment, and disorder in the organic conductors κ-(BETS)2GaBr4 and κ-(BETS)2FeCl2Br2 in the isomorphic class κ-(BETS)2GaFexClBry. The results, combined with previous work, show correlations between the anion composition (GaFexClBry) and the superconducting transition temperature, effective mass, Fermi surface topology, and the mean free path.

  18. Probing of the neutrino magnetic moment at the level of 10{sup -22} μ{sub B} with an intense tritium source of (anti)neutrino and helium target (project)

    SciTech Connect

    Martemyanov, V.P.; Aleshin, V.I.; Tarasenko, V.G.; Tsinoev, V.G.; Sabelnikov, A.A.; Yukhimchuk, A.A.; Popov, V.V.; Baluev, V.V.; Golubkov, A.N.; Klevtsov, V.G.; Kuryakin, A.V.; Sitdikov, D.T.; Bogdanova, L.N.

    2015-03-15

    We present research results of the preparation project for the experimental measurement of the (anti)neutrino magnetic moment at the level of 10{sup -12} μ{sub B} using an intense tritium source of antineutrinos and a liquid helium scintillation detector. The neutrino detection in the scintillation detector is based on the scattering of neutrinos by the electrons of the helium atoms that produces fast electrons able to ionize and exciting helium atoms. The detection of the atomic radiation emitted during the relaxation process of the helium atoms and the knowledge of its parameters will allow us to conclude on the neutrino properties.

  19. Helium-Liquefaction by a Cryocooler in Closed-Loop Cooling System for 21 T Ft-Icr Magnets

    NASA Astrophysics Data System (ADS)

    Choi, Y. S.; Painter, T. A.; Kim, D. L.; Lee, B. S.; Yang, H. S.

    2008-03-01

    The helium liquefaction system using a two-stage pulse tube cryocooler is developed. The main objective of this study is to confirm the feasibility of our recently proposed cryogenic design for a 21 T FT-ICR superconducting magnet system by the closed-loop concept without any replenishment of cryogen. Since the cold surface of a cryocooler is very limited, a cylindrical copper fin is thermally anchored to the first and second stage coldheads in order to extend the available heat transfer surface. A heat exchange tube is soldered on the outer surface of each cylindrical fin and heat exchange occurs between the tube and helium which is passing through the tube. The temperature distributions along the copper cylinder and heat exchanger are analyzed by the numerical method taking into account the fin efficiency of the extended surface. The effect of helium gas flow on the temperature distribution during cool-down process is also presented.

  20. Effects of the interplanetary magnetic field on the location of the open-closed field line boundary

    NASA Astrophysics Data System (ADS)

    Wang, C.; Wang, J. Y.; Lopez, R. E.; Zhang, L. Q.; Tang, B. B.; Sun, T. R.; Li, H.

    2016-07-01

    Using global magnetohydrodynamic(MHD) simulation, we investigate the effect of the interplanetary magnetic field (IMF) on the location of the open-closed field line boundary(OCB), in particular the duskside and dawnside OCB and their asymmetry. We first model the typical OCB-crossing events on 22 October 2001 and 24 October 2002 observed by DMSP. The MHD model presents a good estimate of OCB location under quasi-steady magnetospheric conditions. We then systemically study the location of the OCB under different IMF conditions. The model results show that the dawnside and duskside OCBs respond differently to IMF conditions when BY is present. An empirical expression describing the relationship between the OCB latitudes and IMF conditions has been obtained. It is found that the IMF conditions play an important role in determining the dawn-dusk OCB asymmetry, which is due to the magnetic reconnection at the dayside magnetopause. The differences between the dawn and dusk OCB latitudes from MHD predictions are in good agreement with the observations.

  1. A uniform parameterization of moment tensors

    NASA Astrophysics Data System (ADS)

    Tape, C.; Tape, W.

    2015-12-01

    A moment tensor is a 3 x 3 symmetric matrix that expresses an earthquake source. We construct a parameterization of the five-dimensional space of all moment tensors of unit norm. The coordinates associated with the parameterization are closely related to moment tensor orientations and source types. The parameterization is uniform, in the sense that equal volumes in the coordinate domain of the parameterization correspond to equal volumes of moment tensors. Uniformly distributed points in the coordinate domain therefore give uniformly distributed moment tensors. A cartesian grid in the coordinate domain can be used to search efficiently over moment tensors. We find that uniformly distributed moment tensors have uniformly distributed orientations (eigenframes), but that their source types (eigenvalue triples) are distributed so as to favor double couples. An appropriate choice of a priori moment tensor probability is a prerequisite for parameter estimation. As a seemingly sensible choice, we consider the homogeneous probability, in which equal volumes of moment tensors are equally likely. We believe that it will lead to improved characterization of source processes.

  2. An online database of nuclear electromagnetic moments

    NASA Astrophysics Data System (ADS)

    Mertzimekis, T. J.; Stamou, K.; Psaltis, A.

    2016-01-01

    Measurements of nuclear magnetic dipole and electric quadrupole moments are considered quite important for the understanding of nuclear structure both near and far from the valley of stability. The recent advent of radioactive beams has resulted in a plethora of new, continuously flowing, experimental data on nuclear structure - including nuclear moments - which hinders the information management. A new, dedicated, public and user friendly online database

  3. Inversion of triton moments

    NASA Astrophysics Data System (ADS)

    Clare, R. B.; Levinger, J. S.

    1981-02-01

    We use the formalism of hyperspherical harmonics to calculate several moments for the triton photoeffect, for a Volkov spin-independent potential. First, we improve the accuracy of Maleki's calculations of the moments σ2 and σ3 by including more terms in the hyperspherical expansion. We also calculate moments σ0 and σ1 for a Serber mixture. We find reasonable agreement between our moments found by sum rules and those found from the cross sections calculated by Fang et al. and Levinger-Fitzgibbon. We then develop a technique of inversion of a finite number of moments by making the assumption that the cross section can be written as a sum of several Laguerre polynomials multiplied by a decreasing exponential. We test our inversion technique successfully on several model potentials. We then modify it and apply it to the five moments (σ-1 to σ3) for a force without exchange, and find fair agreement with Fang's values of the cross section. Finally, we apply the inversion technique to our three moments (σ-1,σ0,and σ1) for a Serber mixture, and find reasonable agreement with Gorbunov's measurements of the 3He photoeffect. NUCLEAR REACTIONS Triton photoeffects, hyperspherical harmonics, moments of photoeffect, inversion of moments.

  4. Electromagnetic moments of odd-A Po193-203,211 isotopes

    NASA Astrophysics Data System (ADS)

    Seliverstov, M. D.; Cocolios, T. E.; Dexters, W.; Andreyev, A. N.; Antalic, S.; Barzakh, A. E.; Bastin, B.; Büscher, J.; Darby, I. G.; Fedorov, D. V.; Fedosseev, V. N.; Flanagan, K. T.; Franchoo, S.; Huber, G.; Huyse, M.; Keupers, M.; Köster, U.; Kudryavtsev, Yu.; Marsh, B. A.; Molkanov, P. L.; Page, R. D.; Sjödin, A. M.; Stefan, I.; Van Duppen, P.; Venhart, M.; Zemlyanoy, S. G.

    2014-03-01

    Hyperfine splitting parameters have been measured for the neutron-deficient odd-mass polonium isotopes and isomers Po193-203g,m, Po209,211. The measurement was performed at the ISOLDE (CERN) online mass separator using the in-source resonance ionization spectroscopy technique. The magnetic dipole moments μ and spectroscopic electric quadrupole moments QS have been deduced. Their implication for the understanding of nuclear structure in the vicinity of the closed proton shell at Z =82 and the neutron mid-shell at N =104 is discussed. For the most neutron-deficient nuclei (A =193,195,197), a deviation of μ and QS from the nearly constant values for heavier polonium nuclei was observed. Particle-plus-rotor calculations with static oblate deformation describe the electromagnetic moments for these nuclei well, provided a gradual increase of a mean deformation when going to lighter masses is assumed for the polonium nuclei with A <198.

  5. Detailed discussion of a linear electric field frequency shift induced in confined gases by a magnetic field gradient: Implications for neutron electric-dipole-moment experiments

    NASA Astrophysics Data System (ADS)

    Lamoreaux, S. K.; Golub, R.

    2005-03-01

    The search for particle electric dipole moments (EDM’s) is one of the best places to look for physics beyond the standard model of electroweak interaction because the size of time reversal violation predicted by the standard model is incompatible with present ideas concerning the creation of the baryon-antibaryon asymmetry. As the sensitivity of these EDM searches increases more subtle systematic effects become important. We develop a general analytical approach to describe a systematic effect recently observed in an electric dipole moment experiment using stored particles [J. M. Pendlebury , Phys. Rev. A 70, 032102 (2004)]. Our approach is based on the relationship between the systematic frequency shift and the velocity autocorrelation function of the resonating particles. Our results, when applied to well-known limiting forms of the correlation function, are in good agreement with both the limiting cases studied in recent work that employed a numerical and heuristic analysis. Our general approach explains some of the surprising results observed in that work and displays the rich behavior of the shift for intermediate frequencies, which has not been studied previously.

  6. A global wave-driven magnetohydrodynamic solar model with a unified treatment of open and closed magnetic field topologies

    SciTech Connect

    Oran, R.; Van der Holst, B.; Landi, E.; Jin, M.; Sokolov, I. V.; Gombosi, T. I.

    2013-12-01

    We describe, analyze, and validate the recently developed Alfvén Wave Solar Model, a three-dimensional global model starting from the top of the chromosphere and extending into interplanetary space (out to 1-2 AU). This model solves the extended, two-temperature magnetohydrodynamics equations coupled to a wave kinetic equation for low-frequency Alfvén waves. In this picture, heating and acceleration of the plasma are due to wave dissipation and to wave pressure gradients, respectively. The dissipation process is described by a fully developed turbulent cascade of counterpropagating waves. We adopt a unified approach for calculating the wave dissipation in both open and closed magnetic field lines, allowing for a self-consistent treatment in any magnetic topology. Wave dissipation is the only heating mechanism assumed in the model; no geometric heating functions are invoked. Electron heat conduction and radiative cooling are also included. We demonstrate that the large-scale, steady state (in the corotating frame) properties of the solar environment are reproduced, using three adjustable parameters: the Poynting flux of chromospheric Alfvén waves, the perpendicular correlation length of the turbulence, and a pseudoreflection coefficient. We compare model results for Carrington rotation 2063 (2007 November-December) with remote observations in the extreme-ultraviolet and X-ray ranges from the Solar Terrestrial Relations Observatory, Solar and Heliospheric Observatory, and Hinode spacecraft and with in situ measurements by Ulysses. The results are in good agreement with observations. This is the first global simulation that is simultaneously consistent with observations of both the thermal structure of the lower corona and the wind structure beyond Earth's orbit.

  7. The classical model for moment tensors

    NASA Astrophysics Data System (ADS)

    Tape, Walter; Tape, Carl

    2013-12-01

    A seismic moment tensor is a description of an earthquake source, but the description is indirect. The moment tensor describes seismic radiation rather than the actual physical process that initiates the radiation. A moment tensor `model' then ties the physical process to the moment tensor. The model is not unique, and the physical process is therefore not unique. In the classical moment tensor model, an earthquake arises from slip along a planar fault, but with the slip not necessarily in the plane of the fault. The model specifies the resulting moment tensor in terms of the slip vector, the fault normal vector and the Lamé elastic parameters, assuming isotropy. We review the classical model in the context of the fundamental lune. The lune is closely related to the space of moment tensors, and it provides a setting that is conceptually natural as well as pictorial. In addition to the classical model, we consider a crack plus double-couple model (CDC model) in which a moment tensor is regarded as the sum of a crack tensor and a double couple.

  8. Nuclear Anapole Moments

    SciTech Connect

    Michael Ramsey-Musolf; Wick Haxton; Ching-Pang Liu

    2002-03-29

    Nuclear anapole moments are parity-odd, time-reversal-even E1 moments of the electromagnetic current operator. Although the existence of this moment was recognized theoretically soon after the discovery of parity nonconservation (PNC), its experimental isolation was achieved only recently, when a new level of precision was reached in a measurement of the hyperfine dependence of atomic PNC in 133Cs. An important anapole moment bound in 205Tl also exists. In this paper, we present the details of the first calculation of these anapole moments in the framework commonly used in other studies of hadronic PNC, a meson exchange potential that includes long-range pion exchange and enough degrees of freedom to describe the five independent S-P amplitudes induced by short-range interactions. The resulting contributions of pi-, rho-, and omega-exchange to the single-nucleon anapole moment, to parity admixtures in the nuclear ground state, and to PNC exchange currents are evaluated, using configuration-mixed shell-model wave functions. The experimental anapole moment constraints on the PNC meson-nucleon coupling constants are derived and compared with those from other tests of the hadronic weak interaction. While the bounds obtained from the anapole moment results are consistent with the broad ''reasonable ranges'' defined by theory, they are not in good agreement with the constraints from the other experiments. We explore possible explanations for the discrepancy and comment on the potential importance of new experiments.

  9. Fermion dipole moment and holography

    NASA Astrophysics Data System (ADS)

    Kulaxizi, Manuela; Rahman, Rakibur

    2015-12-01

    In the background of a charged AdS black hole, we consider a Dirac particle endowed with an arbitrary magnetic dipole moment. For non-zero charge and dipole coupling of the bulk fermion, we find that the dual boundary theory can be plagued with superluminal modes. Requiring consistency of the dual CFT amounts to constraining the strength of the dipole coupling by an upper bound. We briefly discuss the implications of our results for the physics of holographic non-Fermi liquids.

  10. Electromagnetic moments of 22F

    NASA Astrophysics Data System (ADS)

    Mihara, M.; Matsuta, K.; Komurasaki, J.; Hirano, H.; Nishimura, D.; Momota, S.; Ohtsubo, T.; Izumikawa, T.; Shimbara, Y.; Kubo, T.; Kameda, D.; Zhou, Dongmei; Zheng, Yongnan; Yuan, Daqing; Zhu, Shengyun; Kitagawa, A.; Kanazawa, M.; Torikoshi, M.; Sato, S.; Nagatomo, T.; Matsumiya, R.; Ishikawa, D.; Fukuda, M.; Minamisono, T.; Nojiri, Y.; Alonso, J. R.; Crebs, G. F.; Symons, T. J. M.

    2010-03-01

    The magnetic dipole (μ) and electric quadrupole (Q) moments of short-lived nucleus 22F (Iπ=4+, T=4.2s) have been measured for the first time by means of the β-NMR technique. A spin polarized 22F beam was produced through the charge exchange reaction of 22Ne and was implanted into single crysltals of NaF and MgF2 for μ and Q measurements, respectively. As a result, |μ(F22)|=(2.69443±0.00039)μ and |Q(F22)|=(3±2)mb was obtained. These values are well reproduced by the shell model calculations.

  11. The magnetic field in the very close neighborhood of Mars according to data from the Mars 2 and Mars 3 spacecraft

    NASA Technical Reports Server (NTRS)

    Dolginov, S. S.; Yeroshenko, Y. G.; Zhuzgov, L. N.

    1972-01-01

    The magnetic field in the close proximity of planet Mars according to data from Mars 2 and Mars 3 spacecraft is discussed. The magnetometers on the spacecraft detected a field whose intensity near the orbital periapses was 7 to 10 times higher than the interplanetary field at the distance of the Martian orbit. The nature of the observed field is described.

  12. Moment inference from tomograms

    USGS Publications Warehouse

    Day-Lewis, F. D.; Chen, Y.; Singha, K.

    2007-01-01

    Time-lapse geophysical tomography can provide valuable qualitative insights into hydrologic transport phenomena associated with aquifer dynamics, tracer experiments, and engineered remediation. Increasingly, tomograms are used to infer the spatial and/or temporal moments of solute plumes; these moments provide quantitative information about transport processes (e.g., advection, dispersion, and rate-limited mass transfer) and controlling parameters (e.g., permeability, dispersivity, and rate coefficients). The reliability of moments calculated from tomograms is, however, poorly understood because classic approaches to image appraisal (e.g., the model resolution matrix) are not directly applicable to moment inference. Here, we present a semi-analytical approach to construct a moment resolution matrix based on (1) the classic model resolution matrix and (2) image reconstruction from orthogonal moments. Numerical results for radar and electrical-resistivity imaging of solute plumes demonstrate that moment values calculated from tomograms depend strongly on plume location within the tomogram, survey geometry, regularization criteria, and measurement error. Copyright 2007 by the American Geophysical Union.

  13. Absolute shielding scales for Al, Ga, and In and revised nuclear magnetic dipole moments of {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In nuclei

    SciTech Connect

    Antušek, A. Holka, F.

    2015-08-21

    We present coupled cluster calculations of NMR shielding constants of aluminum, gallium, and indium in water-ion clusters. In addition, relativistic and dynamical corrections and the influence of the second solvation shell are evaluated. The final NMR shielding constants define new absolute shielding scales, 600.0 ± 4.1 ppm, 2044.4 ± 31.4 ppm, and 4507.7 ± 63.7 ppm for aluminum, gallium, and indium, respectively. The nuclear magnetic dipole moments for {sup 27}Al, {sup 69}Ga, {sup 71}Ga, {sup 113}In, and {sup 115}In isotopes are corrected by combining the computed shielding constants with experimental NMR frequencies. The absolute magnitude of the correction increases along the series and for indium isotopes it reaches approximately −8.0 × 10{sup −3} of the nuclear magneton.

  14. Nuclear spins and moments: Fundamental structural information

    SciTech Connect

    Semmes, P.B.

    1991-01-01

    Predictions for the low energy structure of well deformed odd-A Pm and Sm nuclei in the A {approx} 130 region are given, based on the particle-rotor model. Distinctive magnetic dipole properties (static moments and transition rates) are expected for certain Nilsson configurations, and comparisons to recent data are made for {sup 133}Pm, {sup 135}Sm and {sup 133}Sm.

  15. Nuclear spins and moments: Fundamental structural information

    SciTech Connect

    Semmes, P.B.

    1991-12-31

    Predictions for the low energy structure of well deformed odd-A Pm and Sm nuclei in the A {approx} 130 region are given, based on the particle-rotor model. Distinctive magnetic dipole properties (static moments and transition rates) are expected for certain Nilsson configurations, and comparisons to recent data are made for {sup 133}Pm, {sup 135}Sm and {sup 133}Sm.

  16. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  17. Nature of the boundary between open and closed magnetic field line regions at the Sun revealed by composition data and numerical models

    NASA Astrophysics Data System (ADS)

    Posner, Arik; Zurbuchen, Thomas H.; Schwadron, Nathan A.; Fisk, Lennard A.; Gloeckler, George; Linker, Jon A.; Mikić, Zoran; Riley, Pete

    2001-08-01

    Recently, Fisk et al. [1999] have presented a theory that describes a number of features of the large-scale coronal and heliospheric magnetic field. This theory predicts large-scale transport of magnetic flux across the boundaries of the polar coronal holes, which leads to reconnection processes of open field lines with preliminary closed magnetic structures. Reconnection processes reveal themselves in solar wind composition data: Plasma released out of previously closed magnetic field structures exhibits hotter charge state distributions and has a tendency to be enriched by elements with low first ionization potentials. The idea of reconnection at the boundaries of coronal holes is not new. For example, Wang and Sheeley [1993] and Luhmann et al. [1999] found evidence for that mechanism by comparison of observations of the rotation and evolution of coronal holes with potential field models of the solar corona. We use Ulysses Solar Wind Ion Composition Spectrometer composition measurements and sophisticated numerical models [Linker et al., 1999; Riley et al., 1999] to accurately map these observations back to the solar surface. We then constrain the thickness of the stream interface at the Sun and compare the location of the source region with SOHO observations of the low corona. The results are discussed in the context of the global structure of the heliospheric magnetic field.

  18. Temperature dependence of the magnetic moment relaxation rate of the organic superconductor x-(BEDT-TFF){sub 2}Cu[N(CN){sub 2}]Cl{sub 0.5}Br{sub 0.5}

    SciTech Connect

    Primenko, A.E.; Kuznetsov, V.D.; Metlushko, V.V.; Mendeleev, D.V.; Kushch, N.D.; Yagubskii, E.B.

    1994-06-01

    The authors have investigated relaxation of the residual magnetic moment of x-(BEDT-TTF){sub 2}Cu[N(CN){sub 2}]Cl{sub 0.5}Br{sub 0.5}, an organic superconductor, in the temperature range 2.4 to 9.5 K. In these investigations, they observed that the reduced relaxation rate S=d 1n P{sub m}/dt ln t remains constant for T/T{sub c} < 0.7, and then increases rapidly with T. They also determined the temperature dependence of the critical current density in zero magnetic field. In comparing the functions s(T) and J{sub c}(T) for this superconductor with their counterparts for single-crystal high-temperature superconductors, they have found that their behavior is most analogous to that of s(T) and J{sub c}(T) for YBaCuO. Using the relaxation curves, they have calculated the current-voltage characteristics E(J), which are well-described by a power law function of the type E{proportional_to}J{sup n}. 15 refs., 7 figs.

  19. A mechanism for the dynamo terms to sustain closed-flux current, including helicity balance, by driving current which crosses the magnetic field

    SciTech Connect

    Jarboe, T. R.; Nelson, B. A.; Sutherland, D. A.

    2015-07-15

    An analysis of imposed dynamo current drive (IDCD) [T.R. Jarboe et al., Nucl. Fusion 52 083017 (2012)] reveals: (a) current drive on closed flux surfaces seems possible without relaxation, reconnection, or other flux-surface-breaking large events; (b) the scale size of the key physics may be smaller than is often computationally resolved; (c) helicity can be sustained across closed flux; and (d) IDCD current drive is parallel to the current which crosses the magnetic field to produce the current driving force. In addition to agreeing with spheromak data, IDCD agrees with selected tokamak data.

  20. Absence of exchange interaction between localized magnetic moments and conduction-electrons in diluted Er{sup 3+} gold-nanoparticles

    SciTech Connect

    Lesseux, G. G. Urbano, R. R.; Iwamoto, W.; García-Flores, A. F.; Rettori, C.

    2014-05-07

    The Electron Spin Resonance (ESR) of diluted Er{sup 3+} magnetic ions in Au nanoparticles (NPs) is reported. The NPs were synthesized by reducing chloro triphenyl-phosphine gold(I) and erbium(III) trifluoroacetate. The Er{sup 3+} g-value along with the observed hyperfine splitting indicate that the Er{sup 3+} impurities are in a local cubic symmetry. Furthermore, the Er{sup 3+} ESR spectra show that the exchange interaction between the 4f and the conduction electrons (ce) is absent or negligible in Au{sub 1–x}Er{sub x} NPs, in contrast to the ESR results in bulk Au{sub 1–x}Er{sub x}. Therefore, the nature of this interaction needs to be reexamined at the nano scale range.

  1. Inverse moments equilibria for helical anisotropic systems

    NASA Astrophysics Data System (ADS)

    Cooper, W. A.; Hirshman, S. P.; Depassier, M. C.

    1987-11-01

    An energy functional is devised for magnetic confinement schemes that have anisotropic plasma pressure. The minimization of this energy functional is demonstrated to reproduce components of the magnetohydrodynamic (MHD) force balance relation in systems with helical symmetry. An iterative steepest descent procedure is applied to the Fourier moments of the inverse magnetic flux coordinates to minimize the total energy and thus generate anisotropic pressure MHD equilibria. Applications to straight ELMO Snaky Torus (NTIS Document No. DE-84002406) configurations that have a magnetic well on the outermost flux surfaces have been obtained.

  2. THE POSSIBLE ROLE OF CORONAL STREAMERS AS MAGNETICALLY CLOSED STRUCTURES IN SHOCK-INDUCED ENERGETIC ELECTRONS AND METRIC TYPE II RADIO BURSTS

    SciTech Connect

    Kong, Xiangliang; Chen, Yao; Feng, Shiwei; Wang, Bing; Du, Guohui; Guo, Fan; Li, Gang

    2015-01-10

    Two solar type II radio bursts, separated by ∼24 hr in time, are examined together. Both events are associated with coronal mass ejections (CMEs) erupting from the same active region (NOAA 11176) beneath a well-observed helmet streamer. We find that the type II emissions in both events ended once the CME/shock fronts passed the white-light streamer tip, which is presumably the magnetic cusp of the streamer. This leads us to conjecture that the closed magnetic arcades of the streamer may play a role in electron acceleration and type II excitation at coronal shocks. To examine such a conjecture, we conduct a test-particle simulation for electron dynamics within a large-scale partially closed streamer magnetic configuration swept by a coronal shock. We find that the closed field lines play the role of an electron trap via which the electrons are sent back to the shock front multiple times and therefore accelerated to high energies by the shock. Electrons with an initial energy of 300 eV can be accelerated to tens of keV concentrating at the loop apex close to the shock front with a counter-streaming distribution at most locations. These electrons are energetic enough to excite Langmuir waves and radio bursts. Considering the fact that most solar eruptions originate from closed field regions, we suggest that the scenario may be important for the generation of more metric type IIs. This study also provides an explanation of the general ending frequencies of metric type IIs at or above 20-30 MHz and the disconnection issue between metric and interplanetary type IIs.

  3. Hybrid of Quantum Phases for Induced Dipole Moments

    NASA Astrophysics Data System (ADS)

    Ma, Kai

    2016-09-01

    The quantum phase effects for induced electric and magnetic dipole moments are investigated. It is shown that the phase shift received by induced electric dipole has the same form with the one induced by magnetic dipole moment, therefore the total phase is a hybrid of these two types of phase. This feature indicates that in order to have a decisive measurement on either one of these two phases, it is necessary to measure the velocity dependence of the observed phase.

  4. The Teachable Moment.

    ERIC Educational Resources Information Center

    Goodrow, Mary Ellen

    2000-01-01

    Details how an unplanned activity involving spinning wool presented a teachable moment for children in a family child care setting. Notes how activities related to farming, spinning wool, and using wool cloth resulted from following the children's lead. Concludes that everyday activities provide opportunities to listen to children, learn about…

  5. The Humanist Moment

    ERIC Educational Resources Information Center

    Higgins, Chris

    2014-01-01

    In "The Humanist Moment," Chris Higgins sets out to recover a tenable, living humanism, rejecting both the version vilified by the anti-humanists and the one sentimentalized by the reactionary nostalgists. Rescuing humanism from such polemics is only the first step, as we find at least nine rival, contemporary definitions of humanism.…

  6. Moments with Youth

    ERIC Educational Resources Information Center

    Child & Youth Services, 2004

    2004-01-01

    This chapter presents additional stories and interpretations by John Korsmo, Molly Weingrod, Joseph Stanley, Quinn Wilder, Amy Evans, Rick Flowers, Arcelia Martinez, and Pam Ramsey. The stories and interpretations are presented as teachable moments that are examples of how people are learning to understand youthwork and, as such, are open to…

  7. Ultra-high sensitivity moment magnetometry of geological samples

    NASA Astrophysics Data System (ADS)

    Andrade Lima, E.; Weiss, B. P.

    2012-12-01

    Scanning SQUID microscopy offers a unique combination of high spatial resolution and magnetic field sensitivity that allows for the detection of magnetic moments as weak as 10^-16 Am2. This opens the possibility of extending paleomagnetic analyses to samples that have not been accessible to standard moment magnetometry, for which the detection limit is 10^-12 Am2. Of particular interest are individual terrestrial and extraterrestrial particles of small size (< 500 μm) that may preserve records of planetary dynamos and early nebular magnetic fields. Example targets include impact melt spherules, zircon and other silicate crystals, micrometeorites, cosmic dust, chondrules and refractory inclusions. These grains may be adequately modeled as small uniformly magnetized volumes, such that retrieving their magnetic moments from measured magnetic field maps does not require solving non-unique inverse problems. As a consequence, SQUID microscopes can be utilized as ultra-high sensitivity moment magnetometers. We show alternating field and thermal demagnetization data for several grains that demonstrate the performance of this technique. In addition, we compare scanning SQUID microscopy data with net moment measurements of the same samples performed by a commercial superconducting rock magnetometer. The results agree for stronger moments, as expected, but rapidly diverge as net moments fall below the lower 10^-10 Am2 range. These studies underscore the inability of conventional instruments not only to detect very weak moments but also to isolate contamination originating from background sources such as sample holders and mounts. We expect ultra-high sensitivity moment magnetometry using scanning SQUID microscopy will be a powerful tool in helping elucidate the formation of the solar system and planetary history.

  8. Magnetic cooling close to a quantum phase transition—The case of Er2Ti2O7

    NASA Astrophysics Data System (ADS)

    Wolf, B.; Tutsch, U.; Dörschug, S.; Krellner, C.; Ritter, F.; Assmus, W.; Lang, M.

    2016-10-01

    Magnetic cooling, first introduced in the late twenties of last century, has regained considerable interest recently as a cost-efficient and easy-to-handle alternative to 3He-based refrigeration techniques. Especially, adiabatic demagnetization of paramagnets—the standard materials for magnetic refrigeration—has become indispensable for the present space applications. To match the growing demand for increasing the efficiency in these applications, a new concept for magnetic cooling based on many-body effects around a quantum-critical-point has been introduced and successfully tested [B. Wolf et al., Proc. Natl. Acad. Sci. U.S.A. 108, 6862 (2011)]. By extending this concept to three-dimensional magnetic systems, we present here the magnetothermal response of the cubic pyrochlore material Er2Ti2O7 in the vicinity of its B-induced quantum-critical point which is located around 1.5 T. We discuss performance characteristics such as the range of operation, the efficiency, and the hold time. These figures are compared with those of state-of-the-art paramagnetic coolants and with other quantum-critical systems which differ by the dimensionality of the magnetic interactions and the degree of frustration.

  9. Ferroelectricity with Ferromagnetic Moment in Orthoferrites

    NASA Astrophysics Data System (ADS)

    Tokunaga, Yusuke

    2010-03-01

    Exotic multiferroics with gigantic magnetoelectric (ME) coupling have recently been attracting broad interests from the viewpoints of both fundamental physics and possible technological application to next-generation spintronic devices. To attain a strong ME coupling, it would be preferable that the ferroelectric order is induced by the magnetic order. Nevertheless, the magnetically induced ferroelectric state with the spontaneous ferromagnetic moment is still quite rare apart from a few conical-spin multiferroics. To further explore multiferroic materials with both the strong ME coupling and spontaneous magnetization, we focused on materials with magnetic structures other than conical structure. In this talk we present that the most orthodox perovskite ferrite systems DyFeO3 and GdFeO3 have ``ferromagnetic-ferroelectric,'' i.e., genuinely multiferroic states in which weak ferromagnetic moment is induced by Dzyaloshinskii-Moriya interaction working on Fe spins and electric polarization originates from the striction due to symmetric exchange interaction between Fe and Dy (Gd) spins [1] [2]. Both materials showed large electric polarization (>0.1 μC/cm^2) and strong ME coupling. In addition, we succeeded in mutual control of magnetization and polarization with electric- and magnetic-fields in GdFeO3, and attributed the controllability to novel, composite domain wall structure. [4pt] [1] Y. Tokunaga et al., Phys. Rev. Lett. 101, 097205 (2008). [0pt] [2] Y. Tokunaga et al., Nature Mater. 8, 558 (2009).

  10. Additional calculations of triton moments

    NASA Astrophysics Data System (ADS)

    Lally, D. F.; Levinger, J. S.

    1982-02-01

    The formalism of hyperspherical harmonics is used to calculate several moments of the triton photoeffect for a Volkov potential with Serber exchange. The accuracy of Clare's calculations of moments σ0 and σ1 is improved by including more terms in the hyperspherical harmonic expansion of the potential and of the ground state wave function. The moment σ2=8.9×104 MeV3 mb is calculated using one term in the hyperspherical harmonic expansions of the potential and wave function. We invert four moments and find reasonable agreement with Gorbunov's measurements of the 3He photoeffect. NUCLEAR REACTIONS Triton photoeffect, hyperspherical harmonics, moments of photoeffect, inversion of moments.

  11. Some closed-form solutions of the temperature field due to bending magnet and undulator heating in APS

    SciTech Connect

    Sheng, I.C.; Nian, T.

    1993-07-01

    Several temperature field solutions due to bending magnet and undulator x-ray heating are developed and presented in this paper. The Gaussian power distribution is simulated as the bending magnet whereas a Guassian-parabolic type of power distribution is used for the undulator/wiggler heating. The heating on a two-dimensional plane, three-dimensional block, thin disk, infinite wedge plane, infinite wedge block, and beryllium-copper composite are analyzed. Parametric studies are also included to determine the optimized temperature.

  12. Possible Role of Coronal Streamer as Magnetically-closed Structure in Shock-induced Energetic Electrons and Metric Type II Radio Bursts

    NASA Astrophysics Data System (ADS)

    Kong, X.; Chen, Y.; Guo, F.; Li, G.

    2014-12-01

    Solar type II radio bursts are excited by energetic electrons accelerated at coronal eruption-driven shocks. Streamers are quasi-steady and dense, and magnetically-closed structures in the corona, where the Alfven speed is much lower and plasma outflow is much slower than that of the surroundings, therefore are expected to facilitate the formation/enhancement of shocks. In recent studies, streamers have been suspected to be important on the generation of type II radio bursts and the morphology of radio dynamic spectra. In this study, we first present two type II events in which the type II ends upon the CME front (shock) passing by the streamer tip (cusp). The observations lead us to conjecture that the large-scale closed magnetic field of the streamer may be important to electron acceleration at coronal shocks and excitation of type II bursts. To validate this physical implication, we develop a streamer-shock model consisting of a streamer and an outward-propagating shock, and perform a test-particle simulation. It shows that only those electrons that are injected within the closed field regions can be accelerated efficiently, and the trapping effect via closed field lines allows the trapped electrons to return to the shock front multiple times and be repetitively accelerated. We suggest that the scenario may be potentially important to the generation of more metric type IIs considering the fact that most solar eruptions originate from closed field regions. This scenario also provides an explanation to the ending frequencies of many metric type IIs and the long-standing issue of the disconnection between metric and interplanetary type II bursts.

  13. Boundary effects in welded steel moment connections

    NASA Astrophysics Data System (ADS)

    Lee, Kyoung-Hyeog

    Unprecedented widespread failure of welded moment connections in steel frames caused by the 1994 Northridge and the 1995 Kobe earthquakes have alarmed the engineering communities throughout the world. Welded moment connections in steel frames have been traditionally designed by using the classical beam theory which leads to assumptions that the flanges transfer moment while the web connection primarily resists the shear force. However, this study shows that the magnitude and direction of the principal stresses in the connection region are better approximated by using truss analogy rather than the classical beam theory. Accordingly, both the bending moment and the shear force are transferred across the connection near the beam flanges through diagonal strut action. Thus, the beam flange region of the traditionally designed connection is overloaded. This conclusion explains, to a large extent, the recently observed steel moment connection failures. In this study, detailed finite element analyses were carried out for a representative beam-to-column subassemblage with fully welded connection. The stress distribution in the beam web and flanges in the vicinity of the connection were closely studied. The factors responsible for stress redistribution and concentration were identified by using fundamental principles of mechanics. It was concluded that peak resultant stresses can exceed the values used in simple design calculations by large margins. Using the finite element analysis results and the truss analogy to establish a realistic load path in the connection, a practical and more rational analysis and design procedure was developed. The proposed design procedure and the new connection details were successfully validated through cyclic load testing of a nearly full size specimen. The truss model represented the force transmission around the beam-to-column moment connection region very well. Results of the finite element analyses and the laboratory testing showed

  14. The Magnetic Torque Oscillator and the Magnetic Piston

    ERIC Educational Resources Information Center

    Connors, Martin; Al-Shamali, Farook

    2007-01-01

    A magnet suspended in a uniform magnetic field like that of the Earth can be made to oscillate about the field. The frequency of oscillation depends on the strength (magnetic moment) of the magnet, that of the external field, and the moment of inertia of the magnet. It is easily shown and verified by experiment that a simple but nontrivial…

  15. BIG KARL and COSY: Examples for high performance magnet design taught by {open_quotes}Papa Klaus{close_quotes}

    SciTech Connect

    Bechtstedt, U.; Hacker, U.; Maier, R.; Martin, S.; Berg, G.P.A.; Hardt, A.; Huerlimann, W.; Meissburger, J.; Roemer, J.G.M.

    1995-02-01

    The past decades have seen a tremendous development in nuclear, middle, and high energy physics. This advance was in a great part promoted by the availability of newer and more powerful instruments. Over time, these instruments grew in size as well as in sophistication and precision. Nearly all these devices had one fundamental thing in common - magnetic fields produced with currents and iron. The precision demanded by the new experiments and machines did bring the magnet technology to new frontiers requiring the utmost in the accuracy of magnetic fields. The complex properties of the iron challenged innumerable physicists in the attempt to force the magnetic fields into the desired shape. Experience and analytical insight were the pillars for coping with those problems and only few mastered the skills and were in addition able to communicate their intricate knowledge. It was a fortuitous situation that the authors got to know Klaus Halbach who belonged to those few and who shared his knowledge contributing thus largely to the successful completion of two large instruments that were built at the Forschungszentrum Juelich, KFA, for nuclear and middle energy physics. In one case the efforts went to the large spectrometer named BIG KARL whose design phase started in the early 70`s. In the second case the work started in the early 80`s with the task to build a high precision 2.5 GeV proton accelerator for cooled stored and extracted beams known as COSY-Juelich.

  16. The geometrical-optics law of reflection for electromagnetic waves in magnetically confined plasmas: Specular reflection of rays at the last closed flux surface

    SciTech Connect

    Bizarro, Joao P. S.

    2010-10-15

    Within the geometrical-optics approximation, it is shown that the reflection of rays describing the propagation of electromagnetic waves in fusion-grade, magnetically confined plasmas and impinging on the last closed flux surface, or plasma surface, is necessarily specular or mirror-like. More precisely, the component of the wave vector tangential to that surface does not change, whereas the component normal to it reverses its sign while keeping its magnitude. The well-known law of reflection, stating that the angle of incidence equals that of reflection, is thus generalized to anisotropic media.

  17. Evidence for {open_quotes}magnetic rotation{close_quotes} in nuclei: New results on the M1-bands of {sup 198,199}Pb

    SciTech Connect

    Clark, R.M.

    1996-12-31

    Lifetimes of states in four of the M1-bands in {sup 198,199}Pb have been determined through a Doppler Shift Attenuation Method measurement performed using the Gammasphere array. The deduced B(M1) values, which are a sensitive probe of the underlying mechanism for generating these sequences, show remarkable agreement with Tilted Axis Cranking (TAC) calculations. Evidence is also presented for the possible termination of the bands. The results represent clear evidence for a new concept in nuclear excitations: {open_quote}magnetic rotation{close_quote}.

  18. Collapse of composite tubes under end moments

    NASA Technical Reports Server (NTRS)

    Stockwell, Alan E.; Cooper, Paul A.

    1992-01-01

    Cylindrical tubes of moderate wall thickness such as those proposed for the original space station truss, may fail due to the gradual collapse of the tube cross section as it distorts under load. Sometimes referred to as the Brazier instability, it is a nonlinear phenomenon. This paper presents an extension of an approximate closed form solution of the collapse of isotropic tubes subject to end moments developed by Reissner in 1959 to include specially orthotropic material. The closed form solution was verified by an extensive nonlinear finite element analysis of the collapse of long tubes under applied end moments for radius to thickness ratios and composite layups in the range proposed for recent space station truss framework designs. The finite element analysis validated the assumption of inextensional deformation of the cylindrical cross section and the approximation of the material as specially orthotropic.

  19. Anomalous magnetic moment at Ba in Au

    NASA Astrophysics Data System (ADS)

    Bhati, A. K.; Kaur, J.; Bansal, N.; Negi, D.; Kumar, R.; Bhowmik, R. K.; Kumar, V.; Dey, C. C.

    2015-04-01

    The Time differential perturbed angular distribution (TDPAD) technique is employed to measure the local susceptibility at the recoil implanted Ba ions in Au following the nuclear reaction 120Sn(12C, 3nγ)129Ba. We have observed first time the local paramagnetic susceptibility of 5.26(18) at Ba ions comparable to 4f-ions in any non-ferromagnetic metal at room temperature which seems to be related to the electronic s-d and s-f transfer at positive lattice pressure.

  20. Moments in Time

    PubMed Central

    Wittmann, Marc

    2011-01-01

    It has been suggested that perception and action can be understood as evolving in temporal epochs or sequential processing units. Successive events are fused into units forming a unitary experience or “psychological present.” Studies have identified several temporal integration levels on different time scales which are fundamental for our understanding of behavior and subjective experience. In recent literature concerning the philosophy and neuroscience of consciousness these separate temporal processing levels are not always precisely distinguished. Therefore, empirical evidence from psychophysics and neuropsychology on these distinct temporal processing levels is presented and discussed within philosophical conceptualizations of time experience. On an elementary level, one can identify a functional moment, a basic temporal building block of perception in the range of milliseconds that defines simultaneity and succession. Below a certain threshold temporal order is not perceived, individual events are processed as co-temporal. On a second level, an experienced moment, which is based on temporal integration of up to a few seconds, has been reported in many qualitatively different experiments in perception and action. It has been suggested that this segmental processing mechanism creates temporal windows that provide a logistical basis for conscious representation and the experience of nowness. On a third level of integration, continuity of experience is enabled by working memory in the range of multiple seconds allowing the maintenance of cognitive operations and emotional feelings, leading to mental presence, a temporal window of an individual’s experienced presence. PMID:22022310

  1. An efficient method for tracking a magnetic target using scalar magnetometer array.

    PubMed

    Fan, Liming; Kang, Chong; Zhang, Xiaojun; Zheng, Quan; Wang, Ming

    2016-01-01

    The position of a magnetic target can be obtained through magnetic anomaly which is measured by a magnetic sensor. Comparing with vector magnetic sensor, the measurement value of the scalar magnetic sensor is almost not influenced by its orientation in measurement coordinate axes. Therefore, scalar magnetic sensors can be easily assembled into an array. Based on analysis of the total scalar magnetic anomaly measured by scalar magnetometer, we present an efficient method for tracking a magnetic target using scalar magnetometer array. In this method, we separate the position information and magnetic moment information of magnetic target by matrix transformation. Then, we can obtain the position of the magnetic target in real time by a scalar magnetometer array and a particle swarm optimization algorithm. In addition, the magnetic moment of the target can be estimated when the target's position had been calculated. The simulation shows that the position of the target can be calculated accurately and the relative error of the position is <5 %. The calculated magnetic moment of the target is close to the theoretical value. In addition, execution time of each calculation is <1 s. Thus, the position of the magnetic target can be obtained in real-time through this method. PMID:27186466

  2. An efficient method for tracking a magnetic target using scalar magnetometer array.

    PubMed

    Fan, Liming; Kang, Chong; Zhang, Xiaojun; Zheng, Quan; Wang, Ming

    2016-01-01

    The position of a magnetic target can be obtained through magnetic anomaly which is measured by a magnetic sensor. Comparing with vector magnetic sensor, the measurement value of the scalar magnetic sensor is almost not influenced by its orientation in measurement coordinate axes. Therefore, scalar magnetic sensors can be easily assembled into an array. Based on analysis of the total scalar magnetic anomaly measured by scalar magnetometer, we present an efficient method for tracking a magnetic target using scalar magnetometer array. In this method, we separate the position information and magnetic moment information of magnetic target by matrix transformation. Then, we can obtain the position of the magnetic target in real time by a scalar magnetometer array and a particle swarm optimization algorithm. In addition, the magnetic moment of the target can be estimated when the target's position had been calculated. The simulation shows that the position of the target can be calculated accurately and the relative error of the position is <5 %. The calculated magnetic moment of the target is close to the theoretical value. In addition, execution time of each calculation is <1 s. Thus, the position of the magnetic target can be obtained in real-time through this method.

  3. Multipole moments of bumpy black holes

    SciTech Connect

    Vigeland, Sarah J.

    2010-11-15

    General relativity predicts the existence of black holes, compact objects whose spacetimes depend only on their mass, spin, and charge in vacuum (the 'no-hair' theorem). As various observations probe deeper into the strong fields of black hole candidates, it is becoming possible to test this prediction. Previous work suggested that such tests can be performed by measuring whether the multipolar structure of black hole candidates has the form that general relativity demands, and introduced a family of 'bumpy black hole' spacetimes to be used for making these measurements. These spacetimes have generalized multipoles, where the deviation from the Kerr metric depends on the spacetime's 'bumpiness'. In this paper, we show how to compute the Geroch-Hansen moments of a bumpy black hole, demonstrating that there is a clean mapping between the deviations used in the bumpy black hole formalism and the Geroch-Hansen moments. We also extend our previous results to define bumpy black holes whose current moments, analogous to magnetic moments of electrodynamics, deviate from the canonical Kerr value.

  4. Gradient moment nulling in fast spin echo.

    PubMed

    Hinks, R S; Constable, R T

    1994-12-01

    The fast spin echo sequence combines data from many echo signals in a Carr-Purcell-Meiboom-Gill echo train to form a single image. Much of the signal in the second and later echoes results from the coherent addition of stimulated echo signal components back to the spin echo signal. Because stimulated echoes experience no dephasing effects during the time that they are stored as Mz magnetization, they experience a different gradient first moment than does the spin echo. This leads to flow-related phase differences between different echo components and results in flow voids and ghosting, even when the first moment is nulled for the spin echo signal. A method of gradient moment nulling that correctly compensates both spin echo and stimulated echo components has been developed. The simplest solution involves nulling the first gradient moment at least at the RF pulses and preferably at both the RF pulses and the echoes. Phantom and volunteer studies demonstrate good suppression of flow-related artifacts.

  5. Microscopic magnetic properties of an oxygen-doped Tb-Fe thin film by magnetic Compton scattering

    SciTech Connect

    Agui, Akane; Unno, Tomoya; Matsumoto, Sayaka; Suzuki, Kousuke; Sakurai, Hiroshi; Koizumi, Akihisa

    2013-11-14

    The magnetic Compton scattering of a Tb{sub 32}Fe{sub 55}O{sub 13} film was measured in order to investigate the microscopic magnetization processes (i.e., the spin moment, orbital moment, and element specific moments). The trend of the spin magnetic moment was the same as that of the total magnetic moment but opposite to the orbital magnetic moment. In the low magnetic field region, the magnetic moments were not perfectly aligned perpendicular to the film surface, and the perpendicular components were found to mainly arise from the magnetic moment of Tb. Oxygen atoms hinder long range magnetic interaction and hence also affect the magnetization process of the magnetic moments of Tb and Fe.

  6. Close correlation between magnetic properties and the soft phonon mode of the structural transition in BaFe2As2 and SrFe2As2

    SciTech Connect

    Parshall, D.; Pintschovius, L.; Niedziela, Jennifer L.; Castellan, J. -P.; Lamago, D.; Mittal, R.; Wolf, Th.; Reznik, Dmitry

    2015-04-27

    Parent compounds of Fe-based superconductors undergo a structural phase transition from a tetragonal to an orthorhombic structure. We investigated the temperature dependence of the frequencies of TA phonons that extrapolate to the shear vibrational mode at the zone center, which corresponds to the orthorhombic deformation of the crystal structure at low temperatures in BaFe2As2 and SrFe2As2. We found that acoustic phonons at small wave vectors soften gradually towards the transition from high temperatures, tracking the increase of the size of slowly fluctuating magnetic domains. On cooling below the transition to base temperature the phonons harden, following the square of the magnetic moment (which we find is proportional to the anisotropy gap). Finally, our results provide evidence for close correlation between magnetic and phonon properties in Fe-based superconductors.

  7. Anomalous magnetization of a carbon nanotube as an excitonic insulator

    NASA Astrophysics Data System (ADS)

    Rontani, Massimo

    2014-11-01

    We show theoretically that an undoped carbon nanotube might be an excitonic insulator—the long-sought phase of matter proposed by Keldysh, Kohn, and others fifty years ago. We predict that the condensation of triplet excitons, driven by intervalley exchange interaction, spontaneously occurs at equilibrium if the tube radius is sufficiently small. The signatures of exciton condensation are its sizable contributions to both the energy gap and the magnetic moment per electron. The increase of the gap might have already been measured, albeit with a different explanation [V. V. Deshpande, B. Chandra, R. Caldwell, D. S. Novikov, J. Hone, and M. Bockrath, Science 323, 106 (2009), 10.1126/science.1165799]. The enhancement of the quasiparticle magnetic moment is a pair-breaking effect that counteracts the weak paramagnetism of the ground-state condensate of excitons. This property could rationalize the anomalous magnitude of magnetic moments recently observed in different devices close to charge neutrality.

  8. Atmosphere Expansion and Mass Loss of Close-orbit Giant Exoplanets Heated by Stellar XUV. II. Effects of Planetary Magnetic Field; Structuring of Inner Magnetosphere

    NASA Astrophysics Data System (ADS)

    Khodachenko, M. L.; Shaikhislamov, I. F.; Lammer, H.; Prokopov, P. A.

    2015-11-01

    This is the second paper in a series where we build a self-consistent model to simulate the mass-loss process of a close-orbit magnetized giant exoplanet, so-called hot Jupiter (HJ). In this paper we generalize the hydrodynamic (HD) model of an HJ's expanding hydrogen atmosphere, proposed in the first paper, to include the effects of intrinsic planetary magnetic field. The proposed self-consistent axisymmetric 2D magnetohydrodynamics model incorporates radiative heating and ionization of the atmospheric gas, basic hydrogen chemistry for the appropriate account of major species composing HJ's upper atmosphere and related radiative energy deposition, and {{{H}}}3+ and Lyα cooling processes. The model also takes into account a realistic solar-type X-ray/EUV spectrum for calculation of intensity and column density distribution of the radiative energy input, as well as gravitational and rotational forces acting in a tidally locked planet-star system. An interaction between the expanding atmospheric plasma and an intrinsic planetary magnetic dipole field leads to the formation of a current-carrying magnetodisk that plays an important role for topology and scaling of the planetary magnetosphere. A cyclic character of the magnetodisk behavior, composed of consequent phases of the disk formation followed by the magnetic reconnection with the ejection of a ring-type plasmoid, has been discovered and investigated. We found that the mass-loss rate of an HD 209458b analog planet is weakly affected by the equatorial surface field <0.3 G, but is suppressed by an order of magnitude at the field of 1 G.

  9. Zigzag type magnetic structure of the spin J eff = ½ compound α-RuCl3 as determined by neutron powder diffraction

    NASA Astrophysics Data System (ADS)

    Ritter, C.

    2016-09-01

    Using high intensity powder neutron diffraction the magnetic structure of a-RuCl3 has been determined. Following the magnetic propagation vector κ = (½, 0, ½) the J eff = ½ spins of Ru3+ adopt a Zigzag type arrangement on the honeycomb lattice of the layered P3112 structure. The magnetic moments are oriented perpendicular to the trigonal axis. Similarities and differences to previously published single crystal data are discussed. The low value of the magnetic moments, μRu = 0.5(1) μB indicates a possible closeness of α-RuCl3 to the Kitaev spin liquid state.

  10. Investigation of influence of hypomagnetic conditions closely similar to interplanetary magnetic filed on behavioral and vegetative reactions of higher mammals

    NASA Astrophysics Data System (ADS)

    Krivova, Natalie; Trukhanov, Kiril; Zamotshina, Tatyana; Zaeva, Olga; Khodanovich, Marina; Misina, Tatyana; Tukhvatulin, Ravil; Suhko, Valery

    To study the influence of long being under reduced magnetic field on behavioral and vegetative reactions of higher mammals the white rat males were put into the 700-1000 times reduced geomagnetic field (50-70 nT) for 25 days. Such field was obtained by using automatic compensation of the horizontal and vertical components of the GMF at a frequencies up to 10 Hz by means of solenoids of the experimental magnetic system. Control animals were located in the same room under usual laboratory GMF conditions (52 uT). Two days before the experiment the behavioral reactions were studied in the "open field" by means of a set of tests, characterizing the level of emotionality, moving and orientational-investigative activities of the animals under conditions of unimpeded behavior. 60 white underbred rat males with the initial body mass of 200 g were divided into three clusters. Animals with average indices were selected for the experiment. We have judged behavioral reaction disturbances of the rats under hypomagnetic conditions using videotape recordings carried out in the entire course of the chronic experiment. According to the obtained results during the period of maximum activity (from 230 to 330 a.m.) the number of interrelations between the individuals increased appreciably for experimental rats including interrelations with aggressive character. This was real during all 25 days of observation. We observed a certain dynamics of this index differed from that of the control group. We have also analyzed the final period of observation from the 21th to the 25th days. In this period we studied the 24 hours' dynamics of interrelations which were noted during 5 minutes in every hour around the clock. In the control group the number of interrelation was at a constantly low level. For experimental animals the number of interrelations was higher in the night hours than in the day ones. Moreover it exceeded the similar indexes observed from the 1st to the 20th day. For example from

  11. Impurity-induced moments in underdoped cuprates

    SciTech Connect

    Khaliullin, G. |; Kilian, R.; Krivenko, S.; Fulde, P.

    1997-11-01

    We examine the effect of a nonmagnetic impurity in a two-dimensional spin liquid in the spin-gap phase, employing a drone-fermion representation of spin-1/2 operators. The properties of the local moment induced in the vicinity of the impurity are investigated and an expression for the nuclear-magnetic-resonance Knight shift is derived, which we compare with experimental results. Introducing a second impurity into the spin liquid an antiferromagnetic interaction between the moments is found when the two impurities are located on different sublattices. The presence of many impurities leads to a screening of this interaction as is shown by means of a coherent-potential approximation. Further, the Kondo screening of an impurity-induced local spin by charge carriers is discussed. {copyright} {ital 1997} {ital The American Physical Society}

  12. Magnetic resonance imaging of blood brain/nerve barrier dysfunction and leukocyte infiltration: closely related or discordant?

    PubMed

    Weise, Gesa; Stoll, Guido

    2012-01-01

    Unlike other organs the nervous system is secluded from the rest of the organism by the blood brain barrier (BBB) or blood nerve barrier (BNB) preventing passive influx of fluids from the circulation. Similarly, leukocyte entry to the nervous system is tightly controlled. Breakdown of these barriers and cellular inflammation are hallmarks of inflammatory as well as ischemic neurological diseases and thus represent potential therapeutic targets. The spatiotemporal relationship between BBB/BNB disruption and leukocyte infiltration has been a matter of debate. We here review contrast-enhanced magnetic resonance imaging (MRI) as a non-invasive tool to depict barrier dysfunction and its relation to macrophage infiltration in the central and peripheral nervous system under pathological conditions. Novel experimental contrast agents like Gadofluorine M (Gf) allow more sensitive assessment of BBB dysfunction than conventional Gadolinium (Gd)-DTPA enhanced MRI. In addition, Gf facilitates visualization of functional and transient alterations of the BBB remote from lesions. Cellular contrast agents such as superparamagnetic iron oxide particles (SPIO) and perfluorocarbons enable assessment of leukocyte (mainly macrophage) infiltration by MR technology. Combined use of these MR contrast agents disclosed that leukocytes can enter the nervous system independent from a disturbance of the BBB, and vice versa, a dysfunctional BBB/BNB by itself is not sufficient to attract inflammatory cells from the circulation. We will illustrate these basic imaging findings in animal models of multiple sclerosis, cerebral ischemia, and traumatic nerve injury and review corresponding findings in patients.

  13. Magnetic Resonance Imaging of Blood Brain/Nerve Barrier Dysfunction and Leukocyte Infiltration: Closely Related or Discordant?

    PubMed Central

    Weise, Gesa; Stoll, Guido

    2012-01-01

    Unlike other organs the nervous system is secluded from the rest of the organism by the blood brain barrier (BBB) or blood nerve barrier (BNB) preventing passive influx of fluids from the circulation. Similarly, leukocyte entry to the nervous system is tightly controlled. Breakdown of these barriers and cellular inflammation are hallmarks of inflammatory as well as ischemic neurological diseases and thus represent potential therapeutic targets. The spatiotemporal relationship between BBB/BNB disruption and leukocyte infiltration has been a matter of debate. We here review contrast-enhanced magnetic resonance imaging (MRI) as a non-invasive tool to depict barrier dysfunction and its relation to macrophage infiltration in the central and peripheral nervous system under pathological conditions. Novel experimental contrast agents like Gadofluorine M (Gf) allow more sensitive assessment of BBB dysfunction than conventional Gadolinium (Gd)-DTPA enhanced MRI. In addition, Gf facilitates visualization of functional and transient alterations of the BBB remote from lesions. Cellular contrast agents such as superparamagnetic iron oxide particles (SPIO) and perfluorocarbons enable assessment of leukocyte (mainly macrophage) infiltration by MR technology. Combined use of these MR contrast agents disclosed that leukocytes can enter the nervous system independent from a disturbance of the BBB, and vice versa, a dysfunctional BBB/BNB by itself is not sufficient to attract inflammatory cells from the circulation. We will illustrate these basic imaging findings in animal models of multiple sclerosis, cerebral ischemia, and traumatic nerve injury and review corresponding findings in patients. PMID:23267343

  14. Paleomagnetism on submillimeter scales with scanning magnetic microscopy

    NASA Astrophysics Data System (ADS)

    Andrade Lima, E.; Weiss, B. P.; Fu, R. R.; Suavet, C. R.; Bruno, A. C.

    2013-12-01

    The development of superconducting moment magnetometers three decades ago enabled paleomagnetic studies to be extended to previously inaccessible weakly magnetic samples like sediments, single silicate crystals, and lunar rocks. However, there still are a number of very important questions in geomagnetism and planetary magnetism that have remained unsolved owing to insufficient moment sensitivity and spatial resolution. Examples include retrieving records of magnetic fields in the primitive solar nebula from single meteorite grains, establishing when the geodynamo originated from individual zircon crystals, and understanding the complex magnetostatic interactions in metal grains that plague paleointensity studies of extraterrestrial rocks. Here we describe how we are tackling these problems using two new techniques in scanning magnetic microscopy: SQUID microscopy and magnetic tunnel junction (MTJ) microscopy. Scanning SQUID microscopes offer unparalleled moment sensitivity, but spatial resolution is limited to ~100 μm due to cryogenic constraints. On the other hand, scanning MTJ microscopes operate at room temperature and achieve much higher spatial resolutions (< 10 μm) at the expense of decreased field sensitivity. However, because the MTJ sensor can be placed at very close proximity to the sample, the effective magnetic moment sensitivity is often sufficient for many applications. SQUID microscopes can be utilized as ultra-high sensitivity moment magnetometers (better than 10^-15 Am2) and are particularly powerful to analyze unresolved weak sources such as individual chondrules and single-crystal zircons. The high spatial resolution of MTJ microscopes makes them especially suited to identifying the spatial distribution of magnetic minerals in rocks with complex compositions, such as meteorites and lunar rocks. We present recent results from our paleo- and rock magnetic studies of zircon crystals using SQUID microscopy and briefly discuss the fundamental

  15. Inquiry-Based Science: Turning Teachable Moments into Learnable Moments

    ERIC Educational Resources Information Center

    Haug, Berit S.

    2014-01-01

    This study examines how an inquiry-based approach to teaching and learning creates teachable moments that can foster conceptual understanding in students, and how teachers capitalize upon these moments. Six elementary school teachers were videotaped as they implemented an integrated inquiry-based science and literacy curriculum in their…

  16. Magnetic-Field-Assisted Assembly of Anisotropic Superstructures by Iron Oxide Nanoparticles and Their Enhanced Magnetism.

    PubMed

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W T

    2016-12-01

    Magnetic nanoparticle superstructures with controlled magnetic alignment and desired structural anisotropy hold promise for applications in data storage and energy storage. Assembly of monodisperse magnetic nanoparticles under a magnetic field could lead to highly ordered superstructures, providing distinctive magnetic properties. In this work, a low-cost fabrication technique was demonstrated to assemble sub-20-nm iron oxide nanoparticles into crystalline superstructures under an in-plane magnetic field. The gradient of the applied magnetic field contributes to the anisotropic formation of micron-sized superstructures. The magnitude of the applied magnetic field promotes the alignment of magnetic moments of the nanoparticles. The strong dipole-dipole interactions between the neighboring nanoparticles lead to a close-packed pattern as an energetically favorable configuration. Rod-shaped and spindle-shaped superstructures with uniform size and controlled spacing were obtained using spherical and polyhedral nanoparticles, respectively. The arrangement and alignment of the superstructures can be tuned by changing the experimental conditions. The two types of superstructures both show enhancement of coercivity and saturation magnetization along the applied field direction, which is presumably associated with the magnetic anisotropy and magnetic dipole interactions of the constituent nanoparticles and the increased shape anisotropy of the superstructures. Our results show that the magnetic-field-assisted assembly technique could be used for fabricating nanomaterial-based structures with controlled geometric dimensions and enhanced magnetic properties for magnetic and energy storage applications.

  17. Cosmic ray impact on extrasolar earth-like planets in close-in habitable zones.

    PubMed

    Griessmeier, J-M; Stadelmann, A; Motschmann, U; Belisheva, N K; Lammer, H; Biernat, H K

    2005-10-01

    Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 15% of the Earth's current magnetic moment. Therefore, close-in extrasolar planets seem not to be protected by extended Earth-like magnetospheres, and cosmic rays can reach almost the whole surface area of the upper atmosphere. Primary cosmic ray particles that interact with the atmosphere generate secondary energetic particles, a so-called cosmic ray shower. Some of the secondary particles can reach the surface of terrestrial planets when the surface pressure of the atmosphere is on the order of 1 bar or less. We propose that, depending on atmospheric pressure, biological systems on the surface of Earth-like extrasolar planets at close-in orbital distances can be strongly influenced by secondary cosmic rays.

  18. Computing moment-to-moment BOLD activation for real-time neurofeedback.

    PubMed

    Hinds, Oliver; Ghosh, Satrajit; Thompson, Todd W; Yoo, Julie J; Whitfield-Gabrieli, Susan; Triantafyllou, Christina; Gabrieli, John D E

    2011-01-01

    Estimating moment-to-moment changes in blood oxygenation level dependent (BOLD) activation levels from functional magnetic resonance imaging (fMRI) data has applications for learned regulation of regional activation, brain state monitoring, and brain-machine interfaces. In each of these contexts, accurate estimation of the BOLD signal in as little time as possible is desired. This is a challenging problem due to the low signal-to-noise ratio of fMRI data. Previous methods for real-time fMRI analysis have either sacrificed the ability to compute moment-to-moment activation changes by averaging several acquisitions into a single activation estimate or have sacrificed accuracy by failing to account for prominent sources of noise in the fMRI signal. Here we present a new method for computing the amount of activation present in a single fMRI acquisition that separates moment-to-moment changes in the fMRI signal intensity attributable to neural sources from those due to noise, resulting in a feedback signal more reflective of neural activation. This method computes an incremental general linear model fit to the fMRI time series, which is used to calculate the expected signal intensity at each new acquisition. The difference between the measured intensity and the expected intensity is scaled by the variance of the estimator in order to transform this residual difference into a statistic. Both synthetic and real data were used to validate this method and compare it to the only other published real-time fMRI method.

  19. Geomagnetic dipole moment collapse by convective mixing in the core

    NASA Astrophysics Data System (ADS)

    Liu, Lijun; Olson, Peter

    2009-05-01

    Convective mixing in the fluid outer core can induce rapid transient decrease of the geomagnetic dipole. Here we determine rates of dipole moment decrease as a function of magnetic Reynolds number following convective instability in a numerical dynamo and in axisymmetric kinematic flows. Our calculations show that mixing flows induce reversed magnetic flux on the core-mantle boundary through expulsion of mostly poloidal magnetic field by convective upwellings. The dipole field collapse is accelerated by enhanced radial diffusion and meridional advection of magnetic flux below the core-mantle boundary. Magnetic energy cascades from the dipole to smaller scales during mixing, producing a filamentary magnetic field structure on the core-mantle boundary. We find that the maximum rate of dipole moment decrease on century time scales is weakly sensitive to the mixing flow pattern but varies with the velocity of the flow approximately as cRm β , with Rm the magnetic Reynolds number and (c, β) ≈ (0.2 ± 0.07, 0.78 ± 0.05). According to our calculations, a mixing flow in the outer core with Rm in the range of 200-300 can account for the historically-measured rate of decrease of the geomagnetic dipole moment, although it is unlikely that a single mixing flow event with this intensity would cause a full dipole collapse or polarity reversal.

  20. Magnetic microgels, a promising candidate for enhanced magnetic adsorbent particles in bioseparation: synthesis, physicochemical characterization, and separation performance.

    PubMed

    Turcu, Rodica; Socoliuc, Vlad; Craciunescu, Izabell; Petran, Anca; Paulus, Anja; Franzreb, Matthias; Vasile, Eugeniu; Vekas, Ladislau

    2015-02-01

    For specific applications in the field of high gradient magnetic separation of biomaterials, magnetic nanoparticle clusters of controlled size and high magnetic moment in an external magnetic field are of particular interest. We report the synthesis and characterization of magnetic microgels designed for magnetic separation purposes, as well as the separation efficiency of the obtained microgel particles. High magnetization magnetic microgels with superparamagnetic behaviour were obtained in a two-step synthesis procedure by a miniemulsion technique using highly stable ferrofluid on a volatile nonpolar carrier. Spherical clusters of closely packed hydrophobic oleic acid-coated magnetite nanoparticles were coated with cross linked polymer shells of polyacrylic acid, poly-N-isopropylacrylamide, and poly-3-acrylamidopropyl trimethylammonium chloride. The morphology, size distribution, chemical surface composition, and magnetic properties of the magnetic microgels were determined using transmission electron microscopy, X-ray photoelectron spectroscopy, and vibrating sample magnetometry. Magnetically induced phase condensation in aqueous suspensions of magnetic microgels was investigated by optical microscopy and static light scattering. The condensed phase consists of elongated oblong structures oriented in the direction of the external magnetic field and may grow up to several microns in thickness and tens or even hundreds of microns in length. The dependence of phase condensation magnetic supersaturation on the magnetic field intensity was determined. The experiments using high gradient magnetic separation show high values of separation efficiency (99.9-99.97%) for the magnetic microgels. PMID:25519891