Magnetic moment generation from non-minimal couplings in a scenario with Lorentz-symmetry violation
NASA Astrophysics Data System (ADS)
Belich, H.; Colatto, L. P.; Costa-Soares, T.; Helayël-Neto, J. A.; Orlando, M. T. D.
2009-07-01
This paper deals with situations that illustrate how the violation of Lorentz symmetry in the gauge sector may contribute to magnetic moment generation of massive neutral particles with spin- frac {1}{2} and spin-1. The procedure we adopt here is based on Relativistic Quantum Mechanics. We work out the non-relativistic regime that follows from the wave equation corresponding to a certain particle coupled to an external electromagnetic field and a background that accounts for the Lorentz-symmetry violation, and we thereby read off the magnetic dipole moment operator for the particle under consideration. We keep track of the parameters that govern the non-minimal electromagnetic coupling and the breaking of Lorentz symmetry in the expressions we get for the magnetic moments in the different cases we contemplate. Our claim is that the tiny magnetic dipole moment of truly-elementary neutral particles might signal Lorentz-symmetry violation.
Chang, D. . Dept. of Physics and Astronomy Fermi National Accelerator Lab., Batavia, IL ); Senjanovic, G. . Dept. of Theoretical Physics)
1990-01-01
We review attempts to achieve a large neutrino magnetic moment ({mu}{sub {nu}} {le} 10{sup {minus}11}{mu}{sub B}), while keeping neutrino light or massless. The application to the solar neutrino puzzle is discussed. 24 refs.
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.
Superconductivity from Emerging Magnetic Moments.
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
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.
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.
Spacecraft Attitude Stabilization with Piecewise-Constant Magnetic Dipole Moment
NASA Astrophysics Data System (ADS)
Celani, Fabio
2016-05-01
In actual implementations of magnetic control laws for spacecraft attitude stabilization, the time in which Earth magnetic field is measured must be separated from the time in which magnetic dipole moment is generated. The latter separation translates into the constraint of being able to genere only piecewise-constant magnetic dipole moment. In this work we present attitude stabilization laws using only magnetic actuators that take into account of the latter aspect. Both a state feedback and an output feedback are presented, and it is shown that the proposed design allows for a systematic selection of the sampling period.
Tensor charge and anomalous magnetic moment correlation
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.
Magnetic Moment Distribution in Layered Materials
NASA Astrophysics Data System (ADS)
Nicholson, D. M. C.; Zhang, X.-G.; Wang, Y.; Shelton, W. A.; Butler, W. H.; Stocks, G. M.; MacLaren, J. M.
1996-03-01
Thin layers of magnetic material surrounded by non-magnetic layers display a reduced moment per atom relative to the bulk magnetic material. Plots of sturation magnetization versus magnetic layer thickness can be explained in terms of magnetically dead layers at interfaces. First principles calculations indicate a more complex distribution of magnetic moments. Moment distributions calculated in the local density approximation restricted to colinear spins and with unrestricted spin orientations will be presented for Cu/Ni/Cu, Cu/permalloy/Cu, and Mo/Ni/Mo structures. Work supported by Division of Materials Science, the Mathematical Information and Computational Science Division of the Office of Computational Technology Research, and by the Assistant Secretary of Defence Programs, Technology Management Group, Technology Transfer Initiative, US DOE under subcontract DEAC05-84OR21400 with Martin-Marietta Energy Systems, Inc.
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…
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.
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.
Near-Field Magnetic Dipole Moment Analysis
NASA Technical Reports Server (NTRS)
Harris, Patrick K.
2003-01-01
This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.
The photon magnetic moment problem revisited
NASA Astrophysics Data System (ADS)
Pérez Rojas, H.; Rodríguez Querts, E.
2014-06-01
The photon magnetic moment for radiation propagating in magnetized vacuum is defined as a pseudotensor quantity, proportional to the external electromagnetic field tensor. After expanding the eigenvalues of the polarization operator in powers of , we obtain approximate dispersion equations (cubic in ), and analytic solutions for the photon magnetic moment, valid for low momentum and/or large magnetic field. The paramagnetic photon experiences a redshift, with opposite sign to the gravitational one, which differs for parallel and perpendicular polarizations. It is due to the drain of photon transverse momentum and energy by the external field. By defining an effective transverse momentum, the constancy of the speed of light orthogonal to the field is guaranteed. We conclude that the propagation of the photon non-parallel to the magnetic direction behaves as if there is a quantum compression of the vacuum or a warp of space-time in an amount depending on its angle with regard to the field.
Rapid Characterization of Magnetic Moment of Cells for Magnetic Separation
Ooi, Chinchun; Earhart, Christopher M.; Wilson, Robert J.; Wang, Shan X.
2014-01-01
NCI-H1650 lung cancer cell lines labeled with magnetic nanoparticles via the Epithelial Cell Adhesion Molecule (EpCAM) antigen were previously shown to be captured at high efficiencies by a microfabricated magnetic sifter. If fine control and optimization of the magnetic separation process is to be achieved, it is vital to be able to characterize the labeled cells’ magnetic moment rapidly. We have thus adapted a rapid prototyping method to obtain the saturation magnetic moment of these cells. This method utilizes a cross-correlation algorithm to analyze the cells’ motion in a simple fluidic channel to obtain their magnetophoretic velocity, and is effective even when the magnetic moments of cells are small. This rapid characterization is proven useful in optimizing our microfabricated magnetic sifter procedures for magnetic cell capture. PMID:24771946
Rapid Characterization of Magnetic Moment of Cells for Magnetic Separation.
Ooi, Chinchun; Earhart, Christopher M; Wilson, Robert J; Wang, Shan X
2013-07-01
NCI-H1650 lung cancer cell lines labeled with magnetic nanoparticles via the Epithelial Cell Adhesion Molecule (EpCAM) antigen were previously shown to be captured at high efficiencies by a microfabricated magnetic sifter. If fine control and optimization of the magnetic separation process is to be achieved, it is vital to be able to characterize the labeled cells' magnetic moment rapidly. We have thus adapted a rapid prototyping method to obtain the saturation magnetic moment of these cells. This method utilizes a cross-correlation algorithm to analyze the cells' motion in a simple fluidic channel to obtain their magnetophoretic velocity, and is effective even when the magnetic moments of cells are small. This rapid characterization is proven useful in optimizing our microfabricated magnetic sifter procedures for magnetic cell capture. PMID:24771946
Status and perspectives of neutrino magnetic moments
NASA Astrophysics Data System (ADS)
Alexander, Studenikin
2016-05-01
Basic theoretical and experimental aspects of neutrino magnetic moments are reviewed, including the present best upper bounds from reactor experiments and astrophysics. An interesting effect of neutrino spin precession induced by the background matter transversal current or polarization is also discussed.
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.
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.
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
The generation of rolling moments with the superconducting solenoid model
NASA Technical Reports Server (NTRS)
Goodyear, M. J.
1985-01-01
The superconducting solenoid model is a pilot model core for levitation in a wind tunnel magnetic suspension system. This type of core would replace the ferromagnetic core typically installed in the model fuselage. For suspension purposes, the solenoid is operated upon by a set of electromagnets surrounding the wind tunnel which are to support and restrain the model at required positions and orientations under the influence of powerful aerodynamic disturbances. The subject of providing sources of magnets rolling moment for use when spanwise magnets, which can be used for winged models, are not available is covered. Several methods have emerged for generating a rolling moment based on the use of additional superconducting loops or magnetic poles positioned around or within the solenoid. Predictions of the moment capacities of superconducting loops in models sized for a large wind tunnel are presented. An existing prototype superconducting model proved a suitable vehicle for demonstrating and calibrating, at a smaller scale, some of the other roll elements based on magnetic pole devices. Calibration data are included.
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.
Development of a Thin Film Magnetic Moment Reference Material
Pappas, D. P.; Halloran, S. T.; Owings, R. R.; da Silva, F. C. S.
2008-01-01
In this paper we present the development of a magnetic moment reference material for low moment magnetic samples. We first conducted an inter-laboratory comparison to determine the most useful sample dimensions and magnetic properties for common instruments such as vibrating sample magnetometers (VSM), SQUIDs, and alternating gradient field magnetometers. The samples were fabricated and then measured using a vibrating sample magnetometer. Their magnetic moments were calibrated by tracing back to the NIST YIG sphere, SRM 2853. PMID:27096108
Development of a Thin Film Magnetic Moment Reference Material.
Pappas, D P; Halloran, S T; Owings, R R; da Silva, F C S
2008-01-01
In this paper we present the development of a magnetic moment reference material for low moment magnetic samples. We first conducted an inter-laboratory comparison to determine the most useful sample dimensions and magnetic properties for common instruments such as vibrating sample magnetometers (VSM), SQUIDs, and alternating gradient field magnetometers. The samples were fabricated and then measured using a vibrating sample magnetometer. Their magnetic moments were calibrated by tracing back to the NIST YIG sphere, SRM 2853. PMID:27096108
Magnetic resonance signal moment determination using the Earth's magnetic field.
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
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.
Neutrino magnetic moment, CP violation, and flavor oscillations in matter
NASA Astrophysics Data System (ADS)
Pehlivan, Y.; Balantekin, A. B.; Kajino, Toshitaka
2014-09-01
We consider collective oscillations of neutrinos, which are emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. We investigate the symmetries of the problem in the full three-flavor mixing scheme and in the exact many-body formulation by including the effects of CP violation and the neutrino magnetic moment. We show that, similar to the two-flavor scheme, several dynamical symmetries exist for three flavors in the single-angle approximation if the net electron background in the environment and the effects of the neutrino magnetic moment are negligible. Moreover, we show that these dynamical symmetries are present even when the CP symmetry is violated in neutrino oscillations. We explicitly write down the constants of motion through which these dynamical symmetries manifest themselves in terms of the generators of the SU(3) flavor transformations. We also show that the effects due to the CP-violating Dirac phase factor out of the many-body evolution operator and evolve independently of nonlinear flavor transformations if neutrino electromagnetic interactions are ignored. In the presence of a strong magnetic field, CP-violating effects can still be considered independently provided that an effective definition for the neutrino magnetic moment is used.
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.
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.
Tensor Charges, Quark Anomalous Magnetic Moments And Baryons
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.
Numerical modeling of higher order magnetic moments in UXO discrimination
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.
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
Numerical modeling of magnetic moments for UXO applications
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.
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.
Magnetic moments of octet baryons and sea antiquark polarizations
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.
Relative importance of magnetic moments in UXO clearance applications
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.
Ankle moment generation and maximum-effort curved sprinting performance.
Luo, Geng; Stefanyshyn, Darren
2012-11-15
Turning at high speed along acute curves is crucial for athletic performance. One determinant of curved sprinting speed is the ground reaction force that can be created by the supporting limb; the moment generated at the ankle joint may influence such force generation. Body lean associated with curved sprints positions the ankle joints in extreme in-/eversion, and may hinder the ankle moment generation. To examine the influence of ankle moment generation on curved sprinting performance, 17 male subjects performed maximum-effort curved sprints in footwear with and without a wedge. The wedged footwear was constructed with the intention to align the ankle joints closer to their neutral frontal-plane configuration during counter-clockwise curved sprints so greater joint moments might be generated. We found, with the wedged footwear, the average eversion angle of the inside leg ankle was reduced, and the plantarflexion moment generation increased significantly. Meanwhile, the knee extension moment remained unchanged. With the wedged footwear, stance-average centripetal ground reaction force increased significantly while no difference in the vertical ground reaction force was detected. The subjects created a greater centripetal ground reaction impulse in the wedged footwear despite a shortened stance phase when compared to the control. Stance-average curved sprinting speed improved by 4.3% with the wedged footwear. The changes in ankle moment and curved sprinting speed observed in the current study supports the notion that the moment generation at the ankle joint may be a performance constraint for curved sprinting. PMID:23022207
Lunar magnetic field - Permanent and induced dipole moments
NASA Technical Reports Server (NTRS)
Russell, C. T.; Coleman, P. J., Jr.; Schubert, G.
1974-01-01
Apollo 15 subsatellite magnetic field observations have been used to measure both the permanent and the induced lunar dipole moments. Although only an upper limit of 1.3 x 10 to the 18th gauss-cubic centimeters has been determined for the permanent dipole moment in the orbital plane, there is a significant induced dipole moment which opposes the applied field, indicating the existence of a weak lunar ionosphere.
Magnetic moments of light nuclei from lattice quantum chromodynamics
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
Duality and Electric Dipole Moment of Magnetic Monopole
NASA Astrophysics Data System (ADS)
Kobayashi, M.
After a few personal recollections on Professor Shoichi Sakata and thetheory group of Nagoya Univiersity, the electric dipole moment of magnetic monopoles is discussed. In the N = 2 supersymmetric gauge model, the explicit calculation shows that the fraction of the fermion contribution to the moment is given by a curious number.
A Classical Calculation of the Leptonic Magnetic Moment
NASA Astrophysics Data System (ADS)
Fabbri, Luca
2016-02-01
In this paper we will show that purely classical concepts based on a few heuristic considerations about extended field configurations are enough to compute the leptonic magnetic moment with corrections in α-power perturbative expansion.
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)
Neutrino magnetic moment effects in neutrino nucleus reactions
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.
Pinned orbital moments - A new contribution to magnetic anisotropy.
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
Pinned orbital moments – A new contribution to magnetic anisotropy
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
Magnetic dipole moment estimates for an ancient lunar dynamo
NASA Technical Reports Server (NTRS)
Anderson, K. A.
1983-01-01
The four measured planetary magnetic moments combined with a recent theoretical prediction for dynamo magnetic fields suggests that no dynamo exists in the moon's interior today. For the moon to have had a magnetic moment in the past of sufficient strength to account for at least some of the lunar rock magnetism, the rotation would have been about twenty times faster than it is today and the radius of the fluid, conducting core must have been about 750 km. The argument depends on the validity of the Busse solution to the validity of the MHD problem of planetary dynamos.
Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface.
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
Electron Paramagnetic Resonance of Single Magnetic Moment on a Surface
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
Right-handed neutrino magnetic moments
Aparici, Alberto; Santamaria, Arcadi; Kim, Kyungwook; Wudka, Jose
2009-07-01
We discuss the phenomenology of the most general effective Lagrangian, up to operators of dimension five, built with standard model fields and interactions including right-handed neutrinos. In particular, we find there is a dimension five electroweak moment operator of right-handed neutrinos, not discussed previously in the literature, which could have interesting phenomenological consequences.
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.
Magnetic Moment Enhancement for Mn7 Cluster on Graphene
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.
Magnetic dipole moment determination by near-field analysis
NASA Technical Reports Server (NTRS)
Eichhorn, W. L.
1972-01-01
A method for determining the magnetic moment of a spacecraft from magnetic field data taken in a limited region of space close to the spacecraft. The spacecraft's magnetic field equations are derived from first principles. With measurements of this field restricted to certain points in space, the near-field equations for the spacecraft are derived. These equations are solved for the dipole moment by a least squares procedure. A method by which one can estimate the magnitude of the error in the calculations is also presented. This technique was thoroughly tested on a computer. The test program is described and evaluated, and partial results are presented.
The permanent and induced magnetic dipole moment of the moon
NASA Technical Reports Server (NTRS)
Russell, C. T.; Coleman, P. J., Jr.; Lichtenstein, B. R.; Schubert, G.
1974-01-01
Magnetic field observations with the Apollo 15 subsatellite have been used to deduce the components of both the permanent and induced lunar dipole moments in the orbital plane. The present permanent lunar magnetic dipole moment in the orbital plane is less than 1.3 times ten to the eighteenth power gauss-cu cm. Any uniformly magnetized near surface layer is therefore constrained to have a thickness-magnetization product less than 2.5 emu-cm per g. The induced moment opposes the external field, implying the existence of a substantial lunar ionosphere with a permeability between 0.63 and 0.85. Combining this with recent measures of the ratio of the relative field strength at the ALSEP and Explorer 35 magnetometers indicates that the global lunar permeability relative to the plasma in the geomagnetic tail lobes is between 1.008 and 1.03.
Efficient Moment Matrix Generation for Arbitrary Chemical Networks
Smadbeck, P.; Kaznessis, Y. N.
2012-01-01
As stochastic simulations become increasingly common in biological research, tools for analysis of such systems are in demand. The deterministic analogue to stochastic models, a set of probability moment equations equivalent to the Chemical Master Equation (CME), offers the possibility of a priori analysis of systems without the need for computationally costly Monte Carlo simulations. Despite the drawbacks of the method, in particular non-linearity in even the simplest of cases, the use of moment equations combined with moment-closure techniques has been used effectively in many fields. The techniques currently available to generate moment equations rely upon analytical expressions that are not efficient upon scaling. Additionally, the resulting moment-dependent matrix is lower diagonal and demands massive memory allocation in extreme cases. Here it is demonstrated that by utilizing factorial moments and the probability generating function (the Z-transform of the probability distribution) a recursive algorithm is produced. The resulting method is scalable and particularly efficient when high-order moments are required. The matrix produced is banded and often demands substantially less memory resources. PMID:23175571
Quantum aspects of a moving magnetic quadrupole moment interacting with an electric field
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.
Variational master equation approach to dynamics of magnetic moments
NASA Astrophysics Data System (ADS)
Bogolubov, N. N.; Soldatov, A. V.
2016-07-01
Non-equilibrium properties of a model system comprised of a subsystem of magnetic moments strongly coupled to a selected Bose field mode and weakly coupled to a heat bath made of a plurality of Bose field modes was studied on the basis of non-equilibrium master equation approach combined with the approximating Hamiltonian method. A variational master equation derived within this approach is tractable numerically and can be readily used to derive a set of ordinary differential equations for various relevant physical variables belonging to the subsystem of magnetic moments. Upon further analysis of the thus obtained variational master equation, an influence of the macroscopic filling of the selected Bose field mode at low enough temperatures on the relaxation dynamics of magnetic moments was revealed.
Magnetic moment investigation by frequency mixing techniques.
Teliban, I; Thede, C; Chemnitz, S; Bechtold, C; Quadakkers, W J; Schütze, M; Quandt, E
2009-11-01
Gas turbines and other large industrial equipment are subjected to high-temperature oxidation and corrosion. Research and development of efficient protective coatings is the main task in the field. Also, knowledge about the depletion state of the coating during the operation time is important. To date, practical nondestructive methods for the measurement of the depletion state do not exist. By integrating magnetic phases into the coating, the condition of the coating can be determined by measuring its magnetic properties. In this paper, a new technique using frequency mixing is proposed to investigate the thickness of the coatings based on their magnetic properties. A sensor system is designed and tested on specific magnetic coatings. New approaches are proposed to overcome the dependency of the measurement on the distance between coil and sample that all noncontact techniques face. The novelty is a low cost sensor with high sensibility and selectivity which can provide very high signal-to-noise ratios. Prospects and limitations are discussed for future use of the sensor in industrial applications. PMID:19947756
Fractional impurity moments in two-dimensional noncollinear magnets.
Wollny, Alexander; Fritz, Lars; Vojta, Matthias
2011-09-23
We study dilute magnetic impurities and vacancies in two-dimensional frustrated magnets with noncollinear order. Taking the triangular-lattice Heisenberg model as an example, we use quasiclassical methods to determine the impurity contributions to the magnetization and susceptibility. Most importantly, each impurity moment is not quantized but receives nonuniversal screening corrections due to local relief of frustration. At finite temperatures, where bulk long-range order is absent, this implies an impurity-induced magnetic response of Curie form, with a prefactor corresponding to a fractional moment per impurity. We also discuss the behavior in an applied magnetic field, where we find a singular linear-response limit for overcompensated impurities. PMID:22026900
Effective particle magnetic moment of multi-core particles
NASA Astrophysics Data System (ADS)
Ahrentorp, Fredrik; Astalan, Andrea; Blomgren, Jakob; Jonasson, Christian; Wetterskog, Erik; Svedlindh, Peter; Lak, Aidin; Ludwig, Frank; van IJzendoorn, Leo J.; Westphal, Fritz; Grüttner, Cordula; Gehrke, Nicole; Gustafsson, Stefan; Olsson, Eva; Johansson, Christer
2015-04-01
In this study we investigate the magnetic behavior of magnetic multi-core particles and the differences in the magnetic properties of multi-core and single-core nanoparticles and correlate the results with the nanostructure of the different particles as determined from transmission electron microscopy (TEM). We also investigate how the effective particle magnetic moment is coupled to the individual moments of the single-domain nanocrystals by using different measurement techniques: DC magnetometry, AC susceptometry, dynamic light scattering and TEM. We have studied two magnetic multi-core particle systems - BNF Starch from Micromod with a median particle diameter of 100 nm and FeraSpin R from nanoPET with a median particle diameter of 70 nm - and one single-core particle system - SHP25 from Ocean NanoTech with a median particle core diameter of 25 nm.
Precise Determination of the Strangeness Magnetic Moment of the Nucleon
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.
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
Composite Higgs models, Technicolor and the muon anomalous magnetic moment
NASA Astrophysics Data System (ADS)
Doff, A.; Siqueira, Clarissa
2016-03-01
We revisit the muon magnetic moment (g - 2) in the context of Composite Higgs models and Technicolor, and provide general analytical expressions for computing the muon magnetic moment stemming from new fields such as, neutral gauge bosons, charged gauge bosons, neutral scalar, charged scalars, and exotic charged leptons type of particles. Under general assumptions we assess which particle content could address the g -2μ excess. Moreover, we take a conservative approach and derive stringent limits on the particle masses in case the anomaly is otherwise resolved and comment on electroweak and collider bounds. Lastly, for concreteness we apply our results to a particular Technicolor model.
Precise Determination of the Strangeness Magnetic Moment of the Nucleon
Leinweber, D.B.; Boinepalli, S.; Cloet, I.C.; Williams, A.G.; Young, R.D.; Zhang, J.B.; Thomas, A.W.; Zanotti, J.M.
2005-06-03
By combining the constraints of charge symmetry with new chiral extrapolation techniques and recent low mass quenched 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}=(-0.046{+-}0.019){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.
Photoproduction of the rho meson and its magnetic moments
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.
Berkolaiko, G.; Kuipers, J.
2013-12-15
Electronic transport through chaotic quantum dots exhibits universal behaviour which can be understood through the semiclassical approximation. Within the approximation, calculation of transport moments reduces to codifying classical correlations between scattering trajectories. These can be represented as ribbon graphs and we develop an algorithmic combinatorial method to generate all such graphs with a given genus. This provides an expansion of the linear transport moments for systems both with and without time reversal symmetry. The computational implementation is then able to progress several orders further than previous semiclassical formulae as well as those derived from an asymptotic expansion of random matrix results. The patterns observed also suggest a general form for the higher orders.
Magnetic moments of light nuclei from lattice quantum chromodynamics
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 ^{3}He, along with those of the neutron and proton. These calculations, performed at quark masses corresponding to m_{π} ~ 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 ^{3}He 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, μ_{3H} ~ μ_{p}. The deuteron magnetic moment is found to be equal to the nucleon isoscalar moment within the uncertainties of the calculations.
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.
Implication of magnetic moments for the spin structure of baryons
Bajpai, R.P.; Choudhary, J.K.
1980-11-01
It is shown that the magnetic moments of baryon multiplet suggest that SU(3) is a correct symmetry scheme but that its extension to SU(6) is not justified. The new spin distribution among the different valence quarks, satisfying the SU(3) constraint, and consistent with the models of deep-inelastic scattering is obtained.
Neutrino transitional magnetic moment and non-Abelian discrete symmetry
Chang, D. Fermi National Laboratory, P.O. Box 500, Batavia, IL ); Keung, W. Fermi National Laboratory, P.O. Box 500, Batavia, IL ); Senjanovic, G. Bartol Research Institute, University of Delaware, Newark, DE )
1990-09-01
We propose a mechanism which naturally will give rise to a small mass but a large transitional magnetic moment for the neutrino such that the solar-neutrino deficit problem can be explained. The idea is a discrete version of Voloshin's SU(2) mechanism. An example of such a mechanism using the quaternion group is illustrated.
Constraining the neutrino magnetic dipole moment from white dwarf pulsations
NASA Astrophysics Data System (ADS)
Córsico, A. H.; Althaus, L. G.; Miller Bertolami, M. M.; Kepler, S. O.; García-Berro, E.
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 (μν) 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 (Pi dot) 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 Pi dot 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 μν lesssim 10-11 μB. 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.
Constraining the neutrino magnetic dipole moment from white dwarf pulsations
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.
Heo, Jae Ho
2009-08-01
The model (Lagrangian) with a peculiar extra U(1)[S. M. Barr and I. Dorsner, Phys. Rev. D 72, 015011 (2005); S. M. Barr and A. Khan, Phys. Rev. D 74, 085023 (2006)] is clearly presented. The assigned extra U(1) gauge charges give a strong constraint to build Lagrangians. The Z{sup '} discovery limits are estimated and predicted at the Tevatron and the LHC. The new contributions of the muon anomalous magnetic moment are investigated at one and two loops, and we predict that the deviation from the standard model may be explained. The electron electric dipole moment could also be generated because of the explicit CP-violation effect in the Higgs sector, and a sizable contribution is expected for a moderately sized CP phase [argument of the CP-odd Higgs], 0.1{<=}sin{delta}{<=}1[6 deg. {<=}arg(A){<=}90 deg.].
EM induction experiment to determine the moment of a magnet
NASA Astrophysics Data System (ADS)
Najiya Maryam, K. M.
2014-05-01
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. Mathematical expressions are derived for both. Knowing this equation, experiments to calculate the moment of a magnet can be devised. If we use a long conducting tube instead of a simple coil in this experiment, it can even help in measuring the eddy current damping coefficient k.
Krienin, Frank
1990-01-01
A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.
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
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).
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.
Plantar flexor moment arm and muscle volume predict torque-generating capacity in young men
Baxter, Josh R.
2013-01-01
Muscle volume is known to correlate with maximal joint torque in humans, but the role of muscle moment arm in determining maximal torque is less clear. Moderate correlations have been reported between maximal isometric knee extensor torque and knee extensor moment arm, but no such observations have been made for the ankle joint. It has been suggested that smaller muscle moment arms may enhance force generation at high rates of joint rotation, but this has not yet been observed for ankle muscles in vivo. The purpose of the present study was to correlate plantar flexor moment arm and plantar flexor muscle volume with maximal plantar flexor torque measured at different rates of plantar flexion. Magnetic resonance imaging was used to quantify the plantar flexor moment arm and muscle volume of the posterior compartment in 20 healthy young men. Maximal plantar flexor torque was measured isometrically and at three plantar flexion speeds using an isokinetic dynamometer. Plantar flexor torque was significantly correlated with muscle volume (0.222 < R2 < 0.322) and with muscle moment arm at each speed (0.323 < R2 < 0.494). While muscle volume was strongly correlated with body mass and stature, moment arm was not. The slope of the torque-moment arm regression line decreased as the rate of joint rotation increased, indicating that subjects with small moment arms experienced smaller reductions in torque at high speeds. The findings of this study suggest that plantar flexor moment arm is a determinant of joint strength that is at least as important as muscle size. PMID:24371016
Top Quark Amplitudes with an Anomolous Magnetic Moment
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.
Iodine magnetic moments measured by on-line nuclear orientation
NASA Astrophysics Data System (ADS)
Stone, N. J.; Rikovska, J.; Green, V. R.; Shaw, T. L.; Krane, K. S.; Walker, P. M.; Grant, I. S.
1987-03-01
On-Line measurements of magnetic dipole moments of117 122I are interpreted using coupling of the odd particles to a deformed core. The results show interesting effects of g7/2, d5/2 orbital admixtures in the odd-A isotopes, which are close to spherical. The odd-odd isotopes118, 120I show clear examples of shape co-existence.
Nuclear Magnetic Moment of the {sup 57}Cu Ground State
Minamisono, K.; Mertzimekis, T.J.; Pereira, J.; Mantica, P.F.; Pinter, J.S.; Stoker, J.B.; Tomlin, B.E.; Weerasiri, R.R.; Davies, A.D.; Hass, M.; Rogers, W.F.
2006-03-17
The nuclear magnetic moment of the ground state of {sup 57}Cu(I{sup {pi}}=3/2{sup -},T{sub 1/2}=196.3 ms) has been measured to be vertical bar {mu}({sup 57}Cu) vertical bar =(2.00{+-}0.05){mu}{sub N} using the {beta}-NMR technique. Together with the known magnetic moment of the mirror partner {sup 57}Ni, the spin expectation value was extracted as <{sigma}{sigma}{sub z}>=-0.78{+-}0.13. This is the heaviest isospin T=1/2 mirror pair above the {sup 40}Ca region for which both ground state magnetic moments have been determined. The discrepancy between the present results and shell-model calculations in the full fp shell giving {mu}({sup 57}Cu){approx}2.4{mu}{sub N} and <{sigma}{sigma}{sub z}>{approx}0.5 implies significant shell breaking at {sup 56}Ni with the neutron number N=28.
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.
General magnetic transition dipole moments for electron paramagnetic resonance.
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. PMID:25615456
Calculated magnetic moments of Nd2Fe14B
NASA Astrophysics Data System (ADS)
Nordström, Lars; Johansson, Börje; Brooks, M. S. S.
1991-04-01
A self-consistent spin-polarized band-structure calculation has been performed for the technically important permanent magnet compound Nd2Fe14B. In contrast to earlier calculations, the localized 4f states on the Nd sites are treated in a consistent way. They are not allowed to contribute to the bonding, but they produce a local exchange field, felt by the valence electrons, which is calculated from first-principles local density theory. Assuming a Russel-Saunders coupled Nd 4f moment of 3.3μB/atom, the total magnetic moment is calculated to be 38.1μB/formula unit, to be compared with the experimental value 37.1μB/formula unit [Givord, Li, and Perrier de la Bathie, Solid State Commun. 51, 857 (1984)]. The calculated local Fe moments are quite different on the different crystallographic sites, varying from 2.1μB to 2.9μB/atom.
Toroid dipole moment as a signature of hybridization, observability by magnetic neutron scattering
NASA Astrophysics Data System (ADS)
Buin, Andrei; de Chatel, Peter
2002-03-01
The current denstity generated by electrons in Russell-Saunders states within an l^n manifold comprises only even-parity multipoles: 'magnetic' dipoles, octopoles, etc. (L=1,3,...) and 'electric' quadrupoles, etc. (L=2,4,...). If inversion symmetry is broken, e.g., by an odd-parity order parameter, and hybridization between states of different parity becomes possible, odd-parity terms also emerge in the multipole expansion of the magnetic field. The L=1 'electric' term describes the field of toroidal currents, which can be modeled by a solenoid bent in a circle. The magnetic neutron scattering amplitude due to such toroidal currents (or, equivalently, ring-shaped magnetization patterns), has a distinct angular dependence on the scattering vector q. If data covering a sufficient variety of q vectors and neutron-spin orientations are available, magnetic and toroidal moments can be distinguished unambiguously. However, it can be shown that within a limited set of data, notably within a plane in q space, which contains the magnetic dipole moment that enables a satisfactory interpretation, a toroid moment can be found, which gives an equally satisfactory result. The possible relevance of this finding to the order parameter in URu2Si2 will be discussed.
Song, Zhigang; Quhe, Ruge; Liu, Shunquan; Li, Yan; Feng, Ji; Yang, Yingchang; Lu, Jing; Yang, Jinbo
2015-01-01
In this Letter, a tunable valley polarization is investigated for honeycomb systems with broken inversion symmetry such as transition-metal dichalcogenide MX2 (M = Mo, W; X = S, Se) monolayers through elliptical pumping. Compared to circular pumping, elliptical pumping is a more universal and effective method to create coherent valley polarization. When two valleys of MX2 monolayers are doped or polarized, a novel anomalous Hall effect (called valley orbital magnetic moment Hall effect) is predicted. Valley orbital magnetic moment Hall effect can generate an orbital magnetic moment current without the accompaniment of a charge current, which opens a new avenue for exploration of valleytronics and orbitronics. Valley orbital magnetic moment Hall effect is expected to overshadow spin Hall effect and is tunable under elliptical pumping. PMID:26358835
The Permanent and Inductive Magnetic Moments of Ganymede
NASA Technical Reports Server (NTRS)
Kivelson, M. G.; Khurana, K. K.; Volwerk, M.
2002-01-01
Data acquired by the Galileo magnetometer on five passes by Ganymede have been used to characterize Ganymede's internal magnetic moments. Three of the five passes were useful for determination of the internal moments through quadrupole order. Models representing the internal field as the sum of dipole and quadrupole terms or as the sum of a permanent dipole field upon which is superimposed an induced magnetic dipole driven by the time varying component of the externally imposed magnetic field of Jupiter's magnetosphere give equally satisfactory fits to the data. The permanent dipole moment has an equatorial field magnitude 719 nT and is tilted by 176 degrees from the spin axis with the pole in the southern hemisphere rotated by 24 degrees from the Jupiter-facing meridian plane towards the trailing hemisphere. The data are consistent with an inductive response of a good electrical conductor of radius approximately 1 Ganymede radius. Although the data do not enable us to establish the presence of an inductive response beyond doubt, we favor the inductive response model because it gives a good fit to the data using only 4 parameters to describe the internal sources of fields, whereas the equally good dipole plus quadrupole fit requires 8 parameters. An inductive response is consistent with a buried conducting shell, probably liquid water with dissolved electrolytes, somewhere in the first few hundred km below Ganymede's surface. The depth at which the ocean is buried beneath the surface is somewhat uncertain, but our favored model suggests a depth of order 150 kilometers. As both temperature and pressure increase with depth and the melting temperature of pure ice decreases to a minimum at approximately 170 kilometer depth, it seems possible that near this location, a layer of water would be sandwiched between layers of ice.
Tau anomalous magnetic moment in γγ colliders
NASA Astrophysics Data System (ADS)
Peressutti, Javier; Sampayo, Oscar A.
2012-08-01
We investigate the possibility of setting model independent limits for a nonstandard anomalous magnetic moment aτNP of the tau lepton, in future γγ colliders based on Compton backscattering. For a hypothetical collider we find that, at various levels of confidence, the limits for aτNP could be improved, compared to previous studies based on LEP1, LEP2 and SLD data. We show the results for a realistic range of the center of mass energy of the e+e- collider. As a more direct application, we also present the results of the simulation for the photon collider at the TESLA project.
Bounds on the magnetic moment of the W boson
Samuel, M.A.; Li, G. ); Sinha, N.; Sinha, R.; Sundaresan, M.K. )
1991-07-01
Using the preliminary results for {ital p{bar p}}{r arrow}{ital W}{gamma}{ital X} from the Collider Detector at Fermilab, we obtain information on the magnetic moment of the {ital W} boson. At 90% C.L. we find the bound {minus}9.9{le}{kappa}{le}12.3, which is consistent with the standard model value {kappa}=1. We also consider the radiative decay {ital W}{r arrow}{ital e}{nu}{gamma}.
A planar triangular Dy3 + Dy3 single-molecule magnet with a toroidal magnetic moment.
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
The structures and magnetic moments of Co-C clusters.
Ma, Qing-Min; Liu, Ying; Xie, Zun; Wang, Jing
2010-08-01
The geometries, binding energies, and magnetic moments of small CoC(N) (N = 1-8) and CO2C(N) (N = 1-6) clusters are studied systematically using all-electron density functional theory (DFT) with the generalized gradient approximation (GGA). The results indicate that, for the CoC(N) (N = 1-8) and Co2C(N) (N = 1-6) clusters, the lowest-energy structures are predicted to be linear structures except for CoC2 and CoC7. The ground states of the CoC(N) (N = 1-8) clusters are linear geometries (C(v)) with Co atom at one end. The ground states of the Co2C(N) (N = 1-6) clusters are linear geometries (D(h)) with the two Co atoms located at the two ends. For all the clusters, analysis of the Mülliken population shows that charge transfers from the Co atom(s) to the C atoms. The magnetic moment lies primarily on the Co atom(s). PMID:21125925
Magnetic moments induce strong phonon renormalization in FeSi
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
Magnetic moments induce strong phonon renormalization in FeSi.
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
High sensitivity detection of radio-frequency modulated magnetic moment in semiconductors.
Guite, Chinkhanlun; Venkataraman, V
2011-10-01
An experimental setup has been realized to measure weak magnetic moments which can be modulated at radio frequencies (~1-5 MHz). Using an optimized radio-frequency (RF) pickup coil and lock-in amplifier, an experimental sensitivity of 10(-15) Am(2) corresponding to 10(-18) emu has been demonstrated with a 1 s time constant. The detection limit at room temperature is 9.3 × 10(-16) Am(2)/√Hz limited by Johnson noise of the coil. The setup has been used to directly measure the magnetic moment due to a small number (~7 × 10(8)) of spin polarized electrons generated by polarization modulated optical radiation in GaAs and Ge. PMID:22047310
Anomalous Temperature Dependence of Magnetic Moment in Monodisperse Antiferromagnetic Nanoparticles
NASA Astrophysics Data System (ADS)
Gillaspie, Dane; Gu, B.; Wang, W.; Shen, J.
2005-03-01
1 Condensed Matter Sciences Division, Oak Ridge National Laboratory*, TN 37831 2 Department of Physics and Astronomy, The University of Tennessee, TN 37996 3 Environmental Sciences Division, Oak Ridge National Laboratory*, TN 37831 Recent experiments [1] and theory [2] from AFM nanoparticles showed that they exhibit sizable net magnetization, which increases with increasing temperature. In order to further understand such peculiar temperature dependence, we have measured the magnetic properties of monodisperse hematite (α-Fe2O3) nanoparticles, grown using a microemulsion precipitation technique, which minimizes the impact of the particle moment distribution on the measured properties of the samples. Our measured results indicate that the net magnetization of these nanoparticles, when small, indeed increases linearly with increasing temperature. This is in sharp contrast to the bulk-like behavior of α-Fe2O3, which was observed in particles with size larger than 120 nm. [1] M. Seehra et al, Phys. Rev. B 61, 3513 (2000) [2] S. Mørup, C. Frandsen, Phys. Rev. Lett. 92, 217201 (2004) *Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725
Magnetic dipole moments of {sup 57,58,59}Cu
Cocolios, T. E.; Andreyev, A. N.; Bastin, B.; Bree, N.; Buescher, J.; Elseviers, J.; Gentens, J.; Huyse, M.; Kudryavtsev, Yu.; Pauwels, D.; Bergh, P. Van den; Van Duppen, P.; Sonoda, T.
2010-01-15
In-gas-cell laser spectroscopy of the isotopes {sup 57,58,59,63,65}Cu has been performed at the LISOL facility using the 244.164-nm optical transition from the atomic ground state of copper. A detailed discussion on the hyperfine structure of {sup 63}Cu is presented. The magnetic dipole moments of the isotopes {sup 57,58,59,65}Cu are extracted based on that of {sup 63}Cu. The new value mu=+0.479(13)mu{sub N} is proposed for {sup 58}Cu, consistent with that of a pip{sub 3/2} x nup{sub 3/2} ground-state configuration. Spin assignments for the radioactive isotopes {sup 57,58,59}Cu are confirmed. The isotope shifts between the different isotopes are also given and discussed.
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.
Shell structure of potassium isotopes deduced from their magnetic moments
NASA Astrophysics Data System (ADS)
Papuga, J.; Bissell, M. L.; Kreim, K.; Barbieri, C.; Blaum, K.; De Rydt, M.; Duguet, T.; Garcia Ruiz, R. F.; Heylen, H.; Kowalska, M.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Rajabali, M. M.; Sánchez, R.; Smirnova, N.; Somà, V.; Yordanov, D. T.
2014-09-01
Background: Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. Purpose: Extend our knowledge about the evolution of the 1/2+ and 3/2+ states for K isotopes beyond the N =28 shell gap. Method: High-resolution collinear laser spectroscopy on bunched atomic beams. Results: From measured hyperfine structure spectra of K isotopes, nuclear spins, and magnetic moments of the ground states were obtained for isotopes from N =19 up to N =32. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton 1d3/2 and 2s1/2 in the shell model and ab initio framework is also presented. Conclusions: The dominant component of the wave function for the odd-A isotopes up to K45 is a π1d3/2-1 hole. For K47,49, the main component originates from a π2s1/2-1 hole configuration and it inverts back to the π1d3/2-1 in K51. For all even-A isotopes, the dominant configuration arises from a π1d3/2-1 hole coupled to a neutron in the ν1f7/2 or ν2p3/2 orbitals. Only for K48, a significant amount of mixing with π2s1/2-1⊗ν(pf) is observed leading to a Iπ=1- ground state. For K50, the ground-state spin-parity is 0- with leading configuration π1d3/2-1⊗ν2p3/2-1.
Gd-doped BaSnO3: A transparent conducting oxide with localized magnetic moments
NASA Astrophysics Data System (ADS)
Alaan, Urusa S.; Shafer, Padraic; N'Diaye, Alpha T.; Arenholz, Elke; Suzuki, Y.
2016-01-01
We have synthesized transparent, conducting, paramagnetic stannate thin films via rare-earth doping of BaSnO3. Gd3+ (4f7) substitution on the Ba2+ site results in optical transparency in the visible regime, low resistivities, and high electron mobilities, along with a significant magnetic moment. Pulsed laser deposition was used to stabilize epitaxial Ba0.96Gd0.04SnO3 thin films on (001) SrTiO3 substrates, and compared with Ba0.96La0.04SnO3 and undoped BaSnO3 thin films. Gd as well as La doping schemes result in electron mobilities at room temperature that exceed those of conventional complex oxides, with values as high as 60 cm2/V.s (n = 2.5 × 1020 cm-3) and 30 cm2/V.s (n = 1 × 1020 cm-3) for La and Gd doping, respectively. The resistivity shows little temperature dependence across a broad temperature range, indicating that in both types of films the transport is not dominated by phonon scattering. Gd-doped BaSnO3 films have a strong magnetic moment of ˜7 μB/Gd ion. Such an optically transparent conductor with localized magnetic moments may unlock opportunities for multifunctional devices in the design of next-generation displays and photovoltaics.
Observation of the Nuclear Magnetic Octupole Moment of 137Ba+
NASA Astrophysics Data System (ADS)
Hoffman, Matthew
Single trapped ions are ideal systems in which to test atomic physics at high precision, which can in turn be used for searches for violations of fundamental symmetries and physics beyond the standard model, in addition to quantum computation and a number of other applications. The ion is confined in ultra-high vacuum, is laser cooled to mK temperatures, and kept well isolated from the environment which allows these experimental efforts. In this thesis, a few diagnostic techniques will be discussed, covering a method to measure the linewidth of a narrowband laser in the presence of magnetic field noise, as well as a procedure to measure the ion's temperature using such a narrowband laser. This work has led to two precision experiments to measure atomic structure in 138Ba+, and 137Ba+ discussed here. First, employing laser and radio frequency spectroscopy techniques in 138Ba+, we measured the Lande- gJ factor of the 5D5/2 level at the part-per-million level, the highest precision to date. Later, the development of apparatus to efficiently trap and laser cool 137Ba+ has enabled a measurement of the hyperfine splittings of the 5D3/2 manifold, culminating in the observation of the nuclear magnetic octupole moment of 137Ba+.
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.
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.
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.
Estimation of scalar moments from explosion-generated surface waves
Stevens, J.L.
1985-04-01
Rayleigh waves from underground nuclear explosions are used to estimate scaler moments for 40 Nevada Test Site (NTS) explosions and 18 explosions at the Soviet East Kazakh test site. The Rayleigh wave spectrum is written as a product of functions that depend on the elastic structure of the travel path, the elastic structure of the source region and the Q structure of the path. Results are used to examine the worldwide variability of each factor and the resulting variability of surface wave amplitudes. The path elastic structure and Q structure are found by inversion of Rayleigh wave phase and group velocities and spectral amplitudes. The Green's function derived from this structure is used to estimate the moments of explosions observed along the same path. This procedure produces more consistent amplitude estimates than conventional magnitude measurements. Network scatter in log moment is typically 0.1. In contrast with time-domain amplitudes, the elastic structure of the travel path causes little variability in spectral amplitudes. When the mantle Q is constrained to a value of approximately 100 at depths greater than 120 km, the inversion for Q and moment produces moments that remain constant with distance. Based on the best models available, surface waves from NTS explosions should be larger than surface waves from East Kazakh explosions with the same moment. Estimated scaler moments for the largest East Kazakh explosions since 1976 are smaller than the estimated moments for the largest NTS explosions for the same time period.
NASA Astrophysics Data System (ADS)
Blum, T.; Boyle, P. A.; Izubuchi, T.; Jin, L.; Jüttner, A.; Lehner, C.; Maltman, K.; Marinkovic, M.; Portelli, A.; Spraggs, M.; Rbc; Ukqcd Collaborations
2016-06-01
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 483×96 physical-pion-mass lattice generated by the RBC and UKQCD Collaborations. We find the leading-order hadronic vacuum polarization aμHVP (LO )disc=-9.6 (3.3 )(2.3 )×10-10 , where the first error is statistical and the second systematic.
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
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.
Anomalous magnetic moments in Co/Nb multilayers
NASA Astrophysics Data System (ADS)
Chuang, T. M.; Lee, S. F.; Huang, S. Y.; Yao, Y. D.; Cheng, W. C.; Huang, G. R.
2002-02-01
Response of Co/Nb multilayers to external field near the superconducting transition temperature ( TC) was studied. The average moment of Co was suppressed with decreasing Co thickness. At 10 K, for Co thickness larger than 0.5 nm, the multilayers showed hysteresis and ferromagnetism. Some samples showed anomalous field-cooled paramagnetic moments, similar to Paramagnetic Meissner Effect (PME). This is attributed not to the Co moment but to the suppressed surface TC causing PME.
Meson exchange current effects on magnetic dipole moments of p -shell nuclei
Booten, J.G.L.; van Hees, A.G.M.; Glaudemans, P.W.M. ); Wervelman, R. )
1991-01-01
It is shown that addition of a two-body magnetic dipole operator arising from the exchange of the isovector pion and rho meson to the well-known one-body operator can give important corrections to the magnetic dipole moments of the {ital A}=4--16 nuclei. We performed shell-model calculations in complete 0{h bar}{omega} and (0+2){h bar}{omega} model spaces, thus investigating simultaneously the effects of extension of the model space and meson exchange currents on the magnetic moments. In the enlarged model space a significant improvement on the description of the magnetic moments is obtained by including exchange currents.
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.
Gyrotropic Magnetic Effect and the Magnetic Moment on the Fermi Surface.
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
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.
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.
Enhanced magnetic moment of ultrathin Co films measured by in situ electrodeposition in a SQUID
NASA Astrophysics Data System (ADS)
Topolovec, Stefan; Krenn, Heinz; Würschum, Roland
2016-01-01
A special electrochemical cell enabling in situ electrodeposition in a SQUID magnetometer is applied to study the magnetic moment of ultrathin Co films during growth on an Au(111) substrate. The in situ electrodeposition approach allows a total elimination of the magnetic background signal of the substrate, thus the magnetic moment which arises exclusively from the deposited Co film could be measured with monolayer sensitivity. The average thickness of the deposited Co films dav as determined from the transferred charge can be adjusted easily by varying the parameters of the electrodeposition. Hence, the magnetic moment of Co thin films could be determined in absolute terms as a function of the film thickness dav. For the first few atomic layers an enhancement of the magnetic moment per Co atom compared to the bulk could be observed, which increases steadily with lowering dav, reaching up to 40%.
Probing the magnetic moment of FePt micromagnets prepared by focused ion beam milling
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.
Probing the magnetic moment of FePt micromagnets prepared by focused ion beam milling
NASA Astrophysics Data System (ADS)
Overweg, H. C.; den Haan, A. M. J.; Eerkens, H. J.; Alkemade, P. F. A.; La Rooij, A. L.; Spreeuw, R. J. C.; Bossoni, L.; Oosterkamp, T. H.
2015-08-01
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 × 10-12 Am2, 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.
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.
X-ray detection of transient magnetic moments induced by a spin current in Cu
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^{–5}_{μB} 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}_{μB} 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.
X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu.
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
X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu
NASA Astrophysics Data System (ADS)
Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J. A.; Kent, A. D.; Dürr, H. A.; Ohldag, H.; Stöhr, J.
2015-08-01
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. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.
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.
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.
Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment
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
Four-flavour leading-order hadronic contribution to the muon anomalous magnetic moment
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, aμ^{hvp}, arising from quark-connected Feynman graphs. It is based on ensembles featuring N_{f}=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 μ^{hvp}. The final result involving an estimate of the systematic uncertainty a_{μ}^{hvp}=6.74 (21)(18) 10^{-8} shows a good overall agreement with these computations.
Transition magnetic moment of {Lambda}{yields}{Sigma}{sup 0} in QCD sum rules
Lee, Frank X.; Wang Lai
2011-05-01
The {Lambda}{yields}{Sigma}{sup 0} transition magnetic moment is computed in the QCD sum rules approach. Three independent tensor structures are derived in the external-field method using generalized interpolating fields. They are analyzed together with the {Lambda} and {Sigma}{sup 0} mass sum rules using a Monte-Carlo-based analysis, with attention to operator product expansion convergence, ground-state dominance, and the role of the transitions in the intermediate states. Relations between sum rules for magnetic moments of {Lambda} and {Sigma}{sup 0} and sum rules for transition magnetic moment of {Lambda}{yields}{Sigma}{sup 0} are also examined. Our best prediction for the transition magnetic moment is {mu}{sub {Sigma}}{sup 0}{sub {Lambda}=}1.60{+-}0.07{mu}{sub N}. A comparison is made with other calculations in the literature.
NASA Astrophysics Data System (ADS)
Hwang, C. S.; Yeh, Shuting; Teng, P. K.; Uen, T. M.
1996-05-01
A highly automatic system with a three-angle rotation mechanism has been designed and constructed to measure several thousand permanent magnet blocks. The system's main features include its high speed, highly automatic measurement, and the ease with which the different size magnet blocks can be installed and removed. This system provides precise and accurate measurements of the three orthogonal magnetic moment components to accurately characterize each block, as deemed necessary to assess the field quality of undulators and wigglers. A three-angle in rotation mechanism, together with a simple mathematical algorithm is used to measure and analyze the magnetic moments of the magnet block. The system includes the Helmholtz coil pair, block holder, the three-degree rotation mechanism, and the control and data acquisition system. A power train system consists of one motor coupled with a nonmagnetic stainless steel for 360° rotation and two motors individually coupled with two groups of nonmagnetic time belts for rotation angles of 0°, 180°, 0°, and 90°. The control system uses a microcomputer together with a stepping motor control card and a digital fluxmeter connected by the general purpose interface bus. The measurement speed of this system is 40 blocks per h. One reference magnet was measured, with those results verifying the long term precision of the order of 0.04% for the easy component and 0.02° for two minor components. The coil-pair geometry factor is calibrated via the voltage-field reciprocity principle, indicating that the system absolute accuracy is around 0.43%.
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.
NASA Astrophysics Data System (ADS)
Abgaryan, V. S.; Ananikian, N. S.; Ananikyan, L. N.; Hovhannisyan, V.
2015-02-01
Thermal entanglement, magnetic and quadrupole moments properties of the mixed spin-1/2 and spin-1 Ising-Heisenberg model on a diamond chain are considered. Magnetization and quadrupole moment plateaus are observed for the antiferromagnetic couplings. Thermal negativity as a measure of quantum entanglement of the mixed spin system is calculated. Different behavior for the negativity is obtained for the various values of Heisenberg dipolar and quadrupole couplings. The intermediate plateau of the negativity has been observed at the absence of the single-ion anisotropy and quadrupole interaction term. When dipolar and quadrupole couplings are equal there is a similar behavior of negativity and quadrupole moment.
NASA Astrophysics Data System (ADS)
Pisane, K. L.; Despeaux, E. C.; Seehra, M. S.
2015-06-01
The role of particle size distribution inherently present in magnetic nanoparticles (NPs) is examined in considerable detail in relation to the measured magnetic properties of oleic acid-coated maghemite (γ-Fe2O3) NPs. Transmission electron microscopy (TEM) of the sol-gel synthesized γ-Fe2O3 NPs showed a log-normal distribution of sizes with average diameter
NASA Astrophysics Data System (ADS)
Zhao, Guo-Meng; Wang, Jun; Ren, Yang; Beeli, Pieder
2012-02-01
We report high-temperature (300-1120 K) magnetic properties of Fe and Fe3O4 nanoparticles embedded in multi-walled carbon nanotubes. We unambiguously show that the magnetic moments of Fe and Fe3O4 nanoparticles are seemingly enhanced by a factor of about 3 compared with what they would be expected to have for free (unembedded) magnetic nanoparticles. What is more intriguing is that the enhanced moments were completely lost when the sample was heated up to 1120 K and the lost moments at 1120 K were completely recovered through several thermal cycles below 1020 K. The anomalous thermal hysteresis of the high-field magnetic moments is unlikely to be explained by existing physical models except for the high-field paramagnetic Meissner effect due to the existence of ultrahigh temperature superconductivity in the multi-walled carbon nanotubes.
Emergence of local magnetic moments in doped graphene-related materials
NASA Astrophysics Data System (ADS)
Venezuela, P.; Muniz, R. B.; Costa, A. T.; Edwards, D. M.; Power, S. R.; Ferreira, M. S.
2009-12-01
Motivated by recent studies reporting the formation of localized magnetic moments in doped graphene, we investigate the energetic cost for spin polarizing isolated impurities embedded in this material. When a well-known criterion for the formation of local magnetic moments in metals is applied to graphene we are able to predict the existence of magnetic moments in cases that are in clear contrast to previously reported density-functional theory (DFT) results. When generalized to periodically repeated impurities, a geometry so commonly used in most DFT calculations, this criterion shows that the energy balance involved in such calculations contains unavoidable contributions from the long-ranged pairwise magnetic interactions between all impurities. This proves the fundamental inadequacy of the DFT assumption of independent unit cells in the case of magnetically doped low-dimensional graphene-based materials. We show that this can be circumvented if more than one impurity per unit cell is considered, in which case the DFT results agree perfectly well with the criterion-based predictions for the onset of localized magnetic moments in graphene. Furthermore, the existence of such a criterion determining whether or not a magnetic moment is likely to arise within graphene will be instrumental for predicting the ideal materials for future carbon-based spintronic applications.
Kapitza problem for the magnetic moments of synthetic antiferromagnetic systems
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.
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
Magnetization reversal of uncompensated Fe moments in exchangebiased Ni/FeF2 bilayers
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.
Constraining Neutrino Magnetic Moments with Solar and Reactor Neutrino Data
NASA Astrophysics Data System (ADS)
Tórtola, M. A.
We use the latest solar neutrino data, combined with the results of the reactor experiment KamLAND, to derive stringent bounds on Majorana neutrino transition moments (TMs). Furthermore, we show how the inclusion of data from the reactor experiments Rovno, MUNU and TEXONO in our analysis improves significantly the current constraints on TMs. Finally, we perform a simulation of the future Borexino experiment and show that it will improve the bounds from today's data by one order of magnitude.
Finite Volume Study of the Delta Magnetic Moments Using Dynamical Clover Fermions
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.
Majorana neutrino magnetic moment and neutrino decoupling in big bang nucleosynthesis
NASA Astrophysics Data System (ADS)
Vassh, N.; Grohs, E.; Balantekin, A. B.; Fuller, G. M.
2015-12-01
We examine the physics of the early universe when Majorana neutrinos (νe, νμ, ντ) possess transition magnetic moments. These extra couplings beyond the usual weak interaction couplings alter the way neutrinos decouple from the plasma of electrons/positrons and photons. We calculate how transition magnetic moment couplings modify neutrino decoupling temperatures, and then use a full weak, strong, and electromagnetic reaction network to compute corresponding changes in big bang nucleosynthesis abundance yields. We find that light element abundances and other cosmological parameters are sensitive to magnetic couplings on the order of 1 0-10μB. Given the recent analysis of sub-MeV Borexino data which constrains Majorana moments to the order of 1 0-11μB or less, we find that changes in cosmological parameters from magnetic contributions to neutrino decoupling temperatures are below the level of upcoming precision observations.
Magnetic Field Generation in Stars
NASA Astrophysics Data System (ADS)
Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan
2015-10-01
Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence, in the generation and stability of neutron star fields.
Covariant Spectator Theory of np scattering: Deuteron magnetic moment and form factors
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.
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.
Phase formation, thermal stability and magnetic moment of cobalt nitride thin films
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.
Study of cation magnetic moment directions in Cr (Co) doped nickel ferrites
NASA Astrophysics Data System (ADS)
Lang, L. L.; Xu, J.; Qi, W. H.; Li, Z. Z.; Tang, G. D.; Shang, Z. F.; Zhang, X. Y.; Wu, L. Q.; Xue, L. C.
2014-09-01
Powder samples of the ferrites MxNi1-xFe2O4 (M = Cr, Co and 0.0 ≤ x ≤ 0.3) were prepared using a chemical co-precipitation method. X-ray diffraction analysis showed that the two series of samples had a single-phase cubic spinel structure. It was found that the magnetic moments (μexp) per formula of samples measured at 10 K decreased when Cr substituted for Ni, but increased when Co substituted for Ni, in spite of the fact that the magnetic moments of Cr2+ (4 μB) and Co2+ (3 μB) are higher than that of Ni2+ (2 μB). With the assumption that the magnetic moments of Cr2+ and Cr3+ lie antiparallel to those of the Fe, Co, and Ni cations in the same sublattices of spinel ferrites, the dependences on the Cr (Co) doping level of the sample magnetic moments at 10 K were fitted successfully, using the quantum-mechanical potential barrier model earlier proposed by our group. For the two series of samples, the fitted magnetic moments are close to the experimental results.
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.…
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.
Marcucci, L. E.; Pervin, Muslema; Pieper, Steven C.; Wiringa, R. B.; Schiavilla, R.
2008-12-15
Green's function Monte Carlo calculations of magnetic moments and M1 transitions including two-body meson-exchange current (MEC) contributions are reported for A{<=}7 nuclei. The realistic Argonne v{sub 18} two-nucleon and Illinois-2 three-nucleon potentials are used to generate the nuclear wave functions. The two-body meson-exchange operators are constructed to satisfy the continuity equation with the Argonne v{sub 18} potential. The MEC contributions increase the A=3,7 isovector magnetic moments by 16% and the A=6,7 M1 transition rates by 17-34%, bringing them into very good agreement with the experimental data.
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
Estimation of magnetic moment and anisotropy energy of magnetic markers for biosensing application
NASA Astrophysics Data System (ADS)
Enpuku, K.; Sasayama, T.; Yoshida, T.
2016-05-01
We present a method to evaluate the magnetic moment (m) and the anisotropy energy (E) of magnetic markers, which are the key parameters employed in biosensing applications. The distributions of the m and E values in the marker are evaluated by analyzing the static magnetization (M-H) curve of the suspended markers and the frequency dependence of the AC susceptibility of the immobilized markers, respectively. Then, we obtain the relationship between m and E. In the experiment, four markers made of multicore and single core nanoparticles are examined. We obtain distributions of the m and E values, which show the particular characteristics of each marker. Although the m and E values are widely distributed in the marker, a clear relationship is obtained between the values. Therefore, the obtained m-E curve, as well as the distribution of the m and E values, provides a framework to discuss the dynamic behavior of the immobilized markers. The difference in the estimated m-E curves between the markers is also discussed.
NASA Astrophysics Data System (ADS)
Smits, Janis; Berzins, Andris; Gahbauer, Florian H.; Ferber, Ruvin; Erglis, Kaspars; Cebers, Andrejs; Prikulis, Juris
2016-02-01
We have used a synthetic diamond with a layer of nitrogen-vacancy (NV) centres to image the magnetic field distributions of magnetic particles on the surface of the diamond. Magnetic field distributions of 4 µm and 2 µm ferromagnetic and 500 nm diameter superparamagnetic particles were obtained by measuring the position of the optically detected magnetic resonance peak in the fluorescence emitted by the NV centres for each pixel. We fitted the results to a model in order to determine the magnetic moment of the particles from the magnetic field image and compared the results to the measured magnetic moment of the particles. The best-fit magnetic moment differed from the value expected based on measurements by a vibrating sample magnetometer, which implies that further work is necessary to understand the details of magnetic field measurements on the micro scale. However, the measurements of two different types of ferromagnetic particle gave internally consistent results.
Ionospheric plasma escape by high-altitude electric fields: Magnetic moment ''pumping''
Lundin, R.; Hultqvist, B.
1989-06-01
Measurements of electric fields and the composition of upward flowing ionospheric ions by the Viking spacecraft have provided further insight into the mass dependent plasma escape process taking place in the upper ionosphere. The Viking results of the temperature and mass-composition of individual ion beams suggest that upward flowing ion beams can be generated by a magnetic moment ''pumping'' mechanism caused by low-frequency transverse electric field fluctuations, in addition to a field aligned ''quasi-electrostatic'' acceleration process. Magnetic moment ''pumping'' within transverse electric field gradients can be described as a conversion of electric drift velocity to cyclotron velocity by the inertial drift in time-dependent electric field. This gives an equal cyclotron velocity gain for all plasma species, irrespective of mass. Oxygen ions thus gain 16 times as much transverse energy as protons. In addition to a transverse energy gain above the escape energy, a field-aligned quasi-electrostatic acceleration is considered primarily responsible for the collimated upward flow of ions. The field-aligned acceleration adds a constant parallel energy to escaping ionospheric ions. Thus, ion beams at high altitudes can be explained by a bimodal acceleration from both a transverse (equal velocity) and a parallel (equal energy) acceleration process. The Viking observations also show that the thermal energy of ion beams, and the ion beam width are mass dependent. The average O/sup +//H/sup +/ ''temperature ratio has been found to be 4.0 from the Viking observations. This is less than the factor of 16 anticipated from a coherent transverse electric field acceleration but greater than the factor of 1 (or even less than 1) expected from a turbulent acceleration process. /copyright/ American Geophysical Union 1989
Neutral current induced {pi}{sup 0} production and neutrino magnetic moment
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.
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].
Induced magnetic moment of Eu3+ ions in GaN
Kachkanov, V.; Wallace, M. J.; van der Laan, G.; Dhesi, S. S.; Cavill, S. A.; Fujiwara, Y.; O'Donnell, K. P.
2012-01-01
Magnetic semiconductors with coupled magnetic and electronic properties are of high technological and fundamental importance. Rare-earth elements can be used to introduce magnetic moments associated with the uncompensated spin of 4f-electrons into the semiconductor hosts. The luminescence produced by rare-earth doped semiconductors also attracts considerable interest due to the possibility of electrical excitation of characteristic sharp emission lines from intra 4f-shell transitions. Recently, electroluminescence of Eu-doped GaN in current-injection mode was demonstrated in p-n junction diode structures grown by organometallic vapour phase epitaxy. Unlike most other trivalent rare-earth ions, Eu3+ ions possess no magnetic moment in the ground state. Here we report the detection of an induced magnetic moment of Eu3+ ions in GaN which is associated with the 7F2 final state of 5D0→7F2 optical transitions emitting at 622 nm. The prospect of controlling magnetic moments electrically or optically will lead to the development of novel magneto-optic devices. PMID:23236589
Cavity-mediated coherent coupling of magnetic moments
NASA Astrophysics Data System (ADS)
Lambert, N. J.; Haigh, J. A.; Langenfeld, S.; Doherty, A. C.; Ferguson, A. J.
2016-02-01
We demonstrate the long-range strong coupling of magnetostatic modes in spatially separated ferromagnets mediated by a microwave frequency cavity. Two spheres of yttrium iron garnet are embedded in the cavity and their magnetostatic modes probed using a dispersive measurement technique. We find they are strongly coupled to each other even when detuned from the cavity modes, and investigate the dependence of the magnet-magnet coupling on the cavity detuning. Dark states of the coupled magnetostatic modes of the system are observed, and ascribed to mismatches between the symmetries of the modes and the drive field.
Magnetic moment interactions in the e -- e + system
NASA Astrophysics Data System (ADS)
Geiger, K.; Reinhardt, J.; Müller, B.; Greiner, W.
1988-03-01
We have studied the possible existence of quasibound states of an electron-positron pair due to their magnetic interaction in the framework of the equations suggested by Barut et al. [5]. We derive radial equations for all angular quantum numbers of the e -- e + system and show, in detail, that Barut's equations doe not give a consistent, physically satisfactory description of positronium, except in the non-relativistic approximation (up to terms of order m α2). Moreover, we do not find evidence that the effective potentials occurring in the radial equations support magnetic resonances of the e-- e + system at short particle distances (“micropositronium”).
Octet baryon magnetic moments in the chiral quark model with configuration mixing
Linde, J.; Ohlsson, T.; Snellman, H.
1998-01-01
The Coleman{endash}Glashow sum-rule for magnetic moments is always fulfilled in the chiral quark model, independently of SU(3) symmetry breaking. This is due to the structure of the wave functions, coming from the non-relativistic quark model. Experimentally, the Coleman{endash}Glashow sum-rule is violated by about ten standard deviations. To overcome this problem, two models of wave functions with configuration mixing are studied. One of these models violates the Coleman{endash}Glashow sum-rule to the right degree and also reproduces the octet baryon magnetic moments rather accurately. {copyright} {ital 1997} {ital The American Physical Society}
Magnetic moment formation at a dilute 140Ce impurity in RCo2 compounds
NASA Astrophysics Data System (ADS)
de Oliveira, A. L.; Chaves, C. M.; de Oliveira, N. A.; Troper, A.
2010-05-01
A great deal of experimental work using perturbed angular correlation has succeed in measuring hyperfine fields in Ce diluted in metallic systems, thus allowing the determination of the local impurity moment at low temperatures. Motivated by such experimental work on C140e placed on a R site of the rare earth (R =Gd,Tb,Dy,Ho,Er) in RCo2, we theoretically discuss, within a simple model, the local magnetic moments and, thereby, calculate the magnetic hyperfine fields. The results are in good agreement with the experimental data. For the sake of comparison we recall our previous results on Ta d-impurity embedded in the same hosts.
Magnetic moment formation due to arsenic vacancies in LaFeAsO-derived superconductors
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
Shedding light on dark matter: A Faraday rotation experiment to limit a dark magnetic moment
Gardner, Susan
2009-03-01
A Faraday rotation experiment can set limits on the magnetic moment of a electrically-neutral, dark-matter particle, and the limits increase in stringency as the candidate-particle mass decreases. Consequently, if we assume the dark-matter particle to be a thermal relic, our most stringent constraints emerge at the keV mass scale. We discuss how such an experiment could be realized and determine the limits on the magnetic moment as a function of mass which follow given demonstrated experimental capacities.
Prediction of magnetic moment collapse in ZrFe{sub 2} under hydrostatic pressure
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.
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.
Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal.
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
Disparate ultrafast dynamics of itinerant and localized magnetic moments in gadolinium metal
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
Multi-moment advection scheme in three dimension for Vlasov simulations of magnetized plasma
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.
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.
Effective Action for Fermions with Anomalous Magnetic Moment from Foldy-Wouthuysen Transformation
NASA Astrophysics Data System (ADS)
Barducci, A.; Giachetti, R.
2013-03-01
In this paper, we calculate the effective action for neutral particles with anomalous magnetic moment in an external magnetic and electric field. We show that we can take advantage from the Foldy-Wouthuysen transformation (FWT) for such systems, determined in our previous works: indeed, by this transformation we have explicitly evaluated the diagonalized Hamiltonian, allowing to present a closed form for the corresponding effective action and for the partition function at finite temperature from which the thermodynamical potentials can be calculated.
Effect of longitudinal degree of freedom of magnetic moment in body-centered-cubic iron
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.
Masses and magnetic moments of heavy flavour baryons in hyper central model
NASA Astrophysics Data System (ADS)
Patel, Bhavin; Raiyz, Ajay Kumar; Vinodkumar, P. C.
2008-05-01
We employ the hyper central approach to study the masses and magnetic moments of the baryons constituting single charm and beauty quark. The confinement potential is assumed in the hyper central co-ordinates of the coulomb plus power potential form.
Half-Life and Magnetic Moment of the First Excited State in ^132I
NASA Astrophysics Data System (ADS)
Izumi, S.; Tanigaki, M.; Ouchi, H.; Sasaki, A.; Hoshino, S.; Miyashita, Y.; Sato, N.; Shimada, K.; Wakui, T.; Shinozuka, T.; Ohkubo, Y.
2009-10-01
The half-life and the magnetic moment of the first excited state in ^132I are reported. There have been a long time confusion on the half-life measurements of the first excited state in ^132I. Several groups performed the lifetime measurements, but the reported values range from 1 ns to 7 ns. The only reported value of the magnetic moment for this state was measured by Singh, but their result should be treated as unreliable because the time-integral perturbed angular correlation technique (TIPAC), which requires the life time data of this state, was used in their measurement. From this point of view, the half-life and the magnetic moment of this state were measured. ^132I was obtained as the radioactive beam of ^132Te and ^132Sb from the newly developed RF-IGISOL (Radio Frequency IGISOL system) at Tohoku University. The half-life for this state was determined to be 1.120 ± 0.015 ns by a conventional coincidence technique with a pair of BaF2 detectors. The TDPAC measurement for the ^132I implanted kinematically into nickel was performed with the help of a strong hyperfine field at iodine site in nickel, and the magnetic moment of this state was determined to be μ=+ (2.06 ± 0.18)μN. The configuration of this state based on the present results will be discussed.
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.
High-precision evaluation of the magnetic moment of the helion
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.
Mechanism of magnetic moment collapse under pressure in ferropericlase
NASA Astrophysics Data System (ADS)
Skorikov, N. A.; Shorikov, A. O.; Skornyakov, S. L.; Korotin, M. A.; Anisimov, V. I.
2015-07-01
We propose a new scenario for the magnetic collapse under pressure in ferropericlase (FP) (\\text{F}{{\\text{e}}1/4}\\text{M}{{\\text{g}}3/4} )O without the presence of intermediate spin state, which contradicts the mechanism proposed in (2013 Phys. Rev. B 87 165113). This scenario is supported by results of combined local density approximation + dynamical mean-field theory method calculations for the paramagnetic phase at ambient and high pressures. At ambient pressure, calculation gave (\\text{F}{{\\text{e}}1/4}\\text{M}{{\\text{g}}3/4} )O as an insulator with Fe 3d-shell in high-spin state. Experimentally observed high-spin to low-spin state transition of the \\text{F}{{\\text{e}}2+} ion in the pressure range of 35-75 GPa is successfully reproduced in our calculations. The spin crossover is characterized by coexistence of \\text{F}{{\\text{e}}2+} ions in high and low spin state but intermediate spin state is absent in the whole pressure range. Moreover, the probability of Fe ion {{\\text{d}}7} configuration with S=1 grows with pressure due to shortening of metal-oxygen distance. Also, no metal-insulator transition was obtained up to the pressure 140 GPa in agreement with experiment.
Electromagnetic Currents and Magnetic Moments in $\\chi$EFT
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
Constraining natural SUSY via the Higgs coupling and the muon anomalous magnetic moment measurements
NASA Astrophysics Data System (ADS)
Li, Tianjun; Raza, Shabbar; Wang, Kechen
2016-03-01
We use the Higgs coupling and the muon anomalous magnetic moment measurements to constrain the parameter space of the natural supersymmetry in the generalized minimal supergravity (GmSUGRA) model. We scan the parameter space of the GmSUGRA model with small electroweak fine-tuning measure (ΔEW≤100 ). The parameter space after applying various sparticle mass bounds; Higgs mass bounds; B-physics bounds; the muon magnetic moment constraint; and the Higgs coupling constraint from measurements at HL-LHC, ILC, and CEPC is shown in the planes of various interesting model parameters and sparticle masses. Our study indicates that the Higgs coupling and muon anomalous magnetic moment measurements can constrain the parameter space effectively. It is shown that ΔEW˜30 , consistent with all constraints, and having supersymmetric contributions to the muon anomalous magnetic moment within 1 σ can be achieved. The precision of kb and kτ measurements at CEPC can bound mA to be above 1.2 TeV and 1.1 TeV respectively. The combination of the Higgs coupling measurement and muon anomalous magnetic moment measurement constrain the e˜R mass to be in the range from 0.6 TeV to 2 TeV. The range of both e˜L and ν˜e masses is 0.4 TeV-1.2 TeV. In all cases, the χ˜10 mass needs to be small (mostly ≤400 GeV ). The comparison of bounds in the tan β -mA plane shows that the Higgs coupling measurement is complementary to the direct collider searches for heavy Higgs when constraining the natural SUSY. A few mass spectra in the typical region of parameter space after applying all constraints are shown as well.
Updating the neutron electric dipole moment in a fourth generation standard model
Hisano, Junji; Hou, Wei-Shu; Xu Fanrong
2011-11-01
A fourth generation of quarks, if it exists, may provide sufficient CP violation for the baryon asymmetry of the Universe. We estimate the neutron electric dipole moment in the presence of a fourth generation and find it would be dominated by the strange quark chromoelectric dipole moment, assuming it does not get wiped out by a Peccei-Quinn symmetry. Both the three electroweak loop and the two-loop electroweak/one-loop gluonic contributions are considered. With m{sub b'}, m{sub t'} at 500 GeV or so that can be covered at the LHC, and with a Jarlskog CP violation factor that is consistent with hints of New Physics in b{yields}s transitions, the neutron electric dipole moment is found around 10{sup -31}e cm, still far below the 10{sup -28}e cm reach of the new experiments being planned or under construction.
Marcucci, Laura; Pervin, Muslema; Pieper, Steven; Schiavilla, Rocco; Wiringa, Robert
2008-12-01
Green's function Monte Carlo calculations of magnetic moments and $M1$ transitions including two-body meson-exchange current (MEC) contributions are reported for $A\\leq7$ nuclei. The realistic Argonne $v_{18}$ two-nucleon and Illinois-2 three-nucleon potentials are used to generate the nuclear wave functions. The two-body meson-exchange operators are constructed to satisfy the continuity equation with the Argonne $v_{18}$ potential. The MEC contributions increase the $A$=3,7 isovector magnetic moments by 16\\% and the $A$=6,7 transition rates by 17--34\\%, bringing them into very good agreement with the experimental data.
Search for Trapped Electrons and a Magnetic Moment at Mars by Mariner IV.
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. PMID:17747452
Magnetic moments of octet baryons, angular momenta of quarks, and sea antiquark polarizations
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.
Magnetic moment of the 3/2 + state in 165Ho
NASA Astrophysics Data System (ADS)
Tanigaki, M.; Ohkubo, Y.; Taniguchi, A.; Izumi, S.; Shinozuka, T.
2010-06-01
The Larmor precession for the 362 keV state in 165Ho( I π = 3/2 + , T 1/2 = 1.512 μs) in Dy2O3 with an external magnetic field of 0.3 T was determined to be - 32.3 ± 0.6 MHz by use of the perturbed angular correlation technique, intending to determine the magnetic moment and apply it to the measurement of the hyperfine field at Ho in Fe. The magnetic moment for this state was tentatively deduced under the assumption that the paramagnetic correction factor for a free Ho3 + ion is applicable to the present case. The independent A 22 measurement for the 633 - 362 keV γ cascade for the sign assignment of the Larmor frequency is inconsistent with that from known multipolarities and mixing ratios for this cascade, implying that the mixing ratios may be different from the reported values.
Magnetic Moments of Delta and Omega- baryons with dynamical clover fermions
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 Âµ_(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.
Moment Approach to Deriving a Unified Parallel Viscous Stress in Magnetized Plasmas
NASA Astrophysics Data System (ADS)
Ji, Jeong-Young; Held, Eric D.
2009-06-01
In the moment approach, a parallel heat flux and a viscous stress are derived for arbitrary collisionality, which is becoming increasingly important in emerging concept devices. This derivation improves upon previous derivations by using the full linearized collision operators instead of the pitch-angle scattering operator and also by including the ion-electron collision operator. The parallel viscous stress can be computed by integrating thermodynamic drives along a magnetic field line weighted by kernel functions that are simple linear combinations of exponential functions. The convergence of the ion viscous stress is verified for sinusoidally varying drives with increasing number of moments.
Yukawa coupling and anomalous magnetic moment of the muon: An update for the LHC era
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.
Improved convergence of Monte Carlo generated multi-group scattering moments
Nelson, A. G.; Martin, W. R.
2013-07-01
This paper introduces an improved method of obtaining multi-group scattering moments from a Monte Carlo neutron transport code for use in deterministic transport solvers. The new method increases the information obtained from scattering events and therefore has more useful convergence characteristics than the currently used analog techniques. A prototype of the improved method was implemented in the OpenMC Monte Carlo transport code to compare the accuracy and convergence characteristics of the new method. The prototype showed that accuracy was retained (or improved) while increasing the figure-of-merit for the generation of multi-group scattering moments. (authors)
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.
Decoherence-governed magnetic-moment dynamics of supported atomic objects.
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
The influence of nonlinear magnetic pull on hydropower generator rotors
NASA Astrophysics Data System (ADS)
Gustavsson, Rolf. K.; Aidanpää, Jan-Olov
2006-11-01
In large electrical machines the electromagnetic forces can in some situations have a strong influence on the rotor dynamics. One such case is when the rotor is eccentrically displaced in the generator bore. A strong unbalanced magnetic pull will then appear in the direction of the smallest air-gap. In this paper, the influence of nonlinear magnetic pull is studied for a hydropower generator where the generator spider hub does not coincide with the centre of the generator rim. The generator model consists of a four-degree-of-freedom rigid body, which is connected to an elastic shaft supported by isotropic bearings. The influence of magnetic pull is calculated for the case when the generator spider hub deviates from the centre of the generator rim. A nonlinear model of the magnetic pull is introduced to the model by radial forces and transverse moments. In the numerical analysis input parameters typical for a 70 MW hydropower generator are used. Results are presented in stability and response diagrams. The results show that this type of rotor configuration can in some cases become unstable. Therefore, it is important to consider the distance between the centreline of generator spider hub and the centreline of generator rim.
Pion-proton bremsstrahlung calculation and the ``experimental'' magnetic moment of Δ++(1232)
NASA Astrophysics Data System (ADS)
Lin, Dahang; Liou, M. K.; Ding, Z. M.
1991-11-01
A bremsstrahlung amplitude in the special two-energy-two-angle (TETAS) approximation, which is relativistic, gauge invariant, and consistent with the soft-photon theorem, is derived for the pion-proton bremsstrahlung (π+pγ) process near the Δ++(1232) resonance. In order to take into account bremsstrahlung emission from an internal Δ++ line with both charge and the anomalous magnetic moment λΔ, we have applied a radiation decomposition identity to modify Low's standard prescription for constructing a soft-photon amplitude. This modified procedure is very general; it can be used to derive the TETAS amplitude for any bremsstrahlung process with resonance. The derived TETAS amplitude is applied to calculate all π+pγ cross sections which can be compared with the experimental data. Treating λΔ as a free parameter in these calculations, we extract the ``experimental'' magnetic moment of the Δ++, μΔ, from recent data. The extracted values of μΔ are (3.7-4.2)e/(2mp) from the University of California, Los Angeles data and (4.6-4.9)e/(2mp) from the Paul Scherrer Institute data. Here, mp is the proton mass. These values are smaller than the value 5.58e/(2mp), the ``bare'' magnetic moment predicted by the SU(6) model or the quark model, but they are close to the value 4.25e/(2mp) predicted by the modified SU(6) model of Beg and Pais and to the value (4.41-4.89)e/(2mp) predicted by the corrected bag-model of Brown, Rho, and Vento. Using the extracted μΔ as an input for calculating π+pγ cross sections, we show that the overall agreement between the theoretical predictions calculated with the extracted μΔ and the experimental measurements is excellent. This agreement demonstrates that the TETAS amplitude can be used to describe almost all the available π+pγ data. Finally, we also treat λΔ as a complex quantity, λΔ=λR+iλI, in order to estimate the contribution from the imaginary part λI. The best fit to the data gives λI~=0, independent of the choice
NASA Astrophysics Data System (ADS)
Kota, Yohei; Sakuma, Akimasa
2012-08-01
The magnetocrystalline anisotropy energy and orbital magnetic moment in L10-type transition metal alloys such as FePt, FePd, FeNi, CoPt, CoPd, and MnAl are evaluated while continuously varying the degree of order. The electronic structure with spin--orbit interaction is calculated by employing the tight-binding linear muffin-tin orbital method based on the local spin-density approximation. To control the degree of order, we consider a substitutional disorder and then adopt the coherent potential approximation. The magnetocrystalline anisotropy energy Δ E is roughly proportional to the power of the long-range order parameter S, i.e., Δ E \\propto Sn (n ˜ 1.6{--}2.4). We also discuss the relationship between the magnetocrystalline anisotropy energy and the orbital magnetic moment. In the same compositional system with different degrees of order, the difference between the orbital magnetic moment in the magnetic easy axis and that in the hard one is proportional to Δ E. However, the coefficient corresponding to the effective spin--orbit coupling is inconsistent with the intrinsic one in some cases.
Magnetic structure of Yb2Pt2Pb: Ising moments on the Shastry-Sutherland lattice
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
Large enhancement of magnetic moment in L1(0) ordered FePt thin films by Nd substitutional doping
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.
Large enhancement of magnetic moment in L10 ordered FePt thin films by Nd substitutional doping
NASA Astrophysics Data System (ADS)
Xu, D. B.; Sun, C. J.; Chen, J. S.; Heald, S. M.; Sanyal, B.; Rosenberg, R. A.; Zhou, T. J.; Chow, G. M.
2015-06-01
We studied L10 ordered Fe50Pt50-xNdx alloy films, which showed a large enhancement (~18.4% at room temperature and ~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 L3,2 edges and Nd M5,4 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.
The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters.
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
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 .
W radiative decays and the determination of magnetic dipole and electric quadrupole moments of the W
Samuel, M.A. ); Sinha, N.; Sinha, R.; Sundaresan, M.K. )
1991-10-01
The magnetic dipole moment of the {ital W} boson is given by {mu}={ital e}(1+{kappa}+{lambda})/2{ital M}{sub {ital W}} and its electric quadrupole moment is given by {ital Q}={minus}{ital e}({kappa}{minus}{lambda})/{ital M}{sub {ital W}}{sup 2}. A nonstandard magnetic dipole moment and a nonstandard electric quadrupole moment lead to different differential decay distributions in the radiative decays of {ital W}{sup {plus minus}}, {ital W}{sup {minus}}{r arrow}{ital e}{bar {nu}}{gamma} and {ital W}{sup {minus}}{r arrow}{ital d{bar u}}{gamma}. While hard photons are characteristic signatures of {kappa}{ne}1 there is no such explicit signal for {lambda}{ne}0. We present a technique for the determination of the values of {kappa} and {lambda} by measuring the total number of events in two regions of phase space. This experiment could be done at the CERN {ital e}{sup +}{ital e{minus}} collider LEP II, where a clean source of {ital W} bosons will be available.
Research Update: Plentiful magnetic moments in oxygen deficient SrTiO{sub 3}
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.
Research Update: Plentiful magnetic moments in oxygen deficient SrTiO3
NASA Astrophysics Data System (ADS)
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 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 SrTiO3-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.
Plentiful magnetic moments in oxygen deficient SrTiO_{3}.
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_{3}. Hole and electron doping of oxygen deficient SrTiO_{3} 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 SrTiO_{3}-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.
The MOMENT Magnetic-Mapping Mission: A Nanosatellite for the Scientific Exploration of Mars
NASA Astrophysics Data System (ADS)
Eagleson, S.; Mauthe, S.; Sarda, K.; Spencer, H.; Zee, R. E.; Arkani-Hammed, J.
2008-08-01
MOMENT (Magnetic Observations of Mars Enabled by Nanosatellite Technology) is a nanosatellite that will obtain high-resolution maps of remnant magnetic fields present in the southern highlands of Mars. A European-developed magnetometer accurate to bet- ter than 0.5 nT and employed in a highly elliptical orbit with a relatively low, 100 km night-side, periapsis will provide much greater spatial resolution and delineation of local magnetic anomalies than is available from the initial surveys performed by Mars Global Surveyor (MGS). During the aerobraking phase of the MGS mission, low-altitude measurements were corrupted by solar wind because they were acquired under sunlit conditions where solar winds interacted with the crustal magnetic fields. During the mapping phase of the mission, spatial resolution was limited to about 400 km. Both of these issues will be overcome by MOMENT's low-altitude, night-side, observing strategy. The resulting magnetic-field maps, for the key areas of interest, will allow detailed studies of regional tectonics and the history of the planet's now- inactive core dynamo. MOMENT's design is based on the Space Flight Laboratory's Generic Nanosatellite Bus (GNB), which is also being developed for the BRITE space-astronomy and CanX-4&5 formation- flight missions. Nominally a 30 x 30 x 30 cm cube on the order of 10 kg mass, MOMENT uses as much GNB technology as possible to provide a rapid and cost-effective mission. The implementation of the mission requires payload space on a larger carrier spacecraft and the use of existing and future Martian communication relays for the transfer of information to and from Earth, necessitating a high level of international co-operation. MOMENT is otherwise fully independent and autonomous, even during scientific operations. This paper describes the conceptual (Canadian Space Agency funded) MOMENT mission and presents a strong case for the use of nanosatellite technology as a relatively simple and cost
Finite-volume effects in the muon anomalous magnetic moment on the lattice
NASA Astrophysics Data System (ADS)
Aubin, Christopher; Blum, Thomas; Chau, Peter; Golterman, Maarten; Peris, Santiago; Tu, Cheng
2016-03-01
We investigate finite-volume effects in the hadronic vacuum polarization, with an eye toward the corresponding systematic error in the muon anomalous magnetic moment. We consider both recent lattice data as well as lowest-order, finite-volume chiral perturbation theory, in order to get a quantitative understanding. Even though leading-order chiral perturbation theory does not provide a good description of the hadronic vacuum polarization, it turns out that it gives a good representation of finite-volume effects. We find that finite-volume effects cannot be ignored when the aim is a few percent level accuracy for the leading-order hadronic contribution to the muon anomalous magnetic moment, even when using ensembles with mπL ≳4 and mπ˜200 MeV .
Aharonov-Anandan quantum phases and Landau quantization associated with a magnetic quadrupole moment
NASA Astrophysics Data System (ADS)
Fonseca, I. C.; Bakke, K.
2015-12-01
The arising of geometric quantum phases in the wave function of a moving particle possessing a magnetic quadrupole moment is investigated. It is shown that an Aharonov-Anandan quantum phase (Aharonov and Anandan, 1987) can be obtained in the quantum dynamics of a moving particle with a magnetic quadrupole moment. In particular, it is obtained as an analogue of the scalar Aharonov-Bohm effect for a neutral particle (Anandan, 1989). Besides, by confining the quantum particle to a hard-wall confining potential, the dependence of the energy levels on the geometric quantum phase is discussed and, as a consequence, persistent currents can arise from this dependence. Finally, an analogue of the Landau quantization is discussed.
First result for the neutrino magnetic moment from measurements with the GEMMA spectrometer
Beda, A. G.; Brudanin, V. B.; Demidova, E. V.; Vylov, C.; Gavrilov, M. G.; Egorov, V. G.; Starostin, A. S.; Shirchenko, M. V.
2007-11-15
The first result obtained in the measurements of the neutrino magnetic moment at the Kalinin nuclear power plant with the GEMMA spectrometer is presented. A high-purity germanium detector of mass 1.5 kg placed at a distance of 13.9 m from the reactor core is used in the spectrometer. The antineutrino flux at the detector position is 2.73 x 10{sup 13{nu}}-bar/(cm{sup 2} s). The differential method is used to select events of electromagnetic antineutrino-electron scattering. The spectra taken in the reactor-on and reactor-off modes over 6200 and 2064 h, respectively, are compared. On the basis of a data analysis, an upper limit of 5.8 x 10{sup -11} {mu}B was set on the neutrino magnetic moment {mu}{sub {nu}}at a 90% C.L.
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
NASA Astrophysics Data System (ADS)
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.
2015-03-01
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.
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
The Generation of Forces and Moments during Visual-Evoked Steering Maneuvers in Flying Drosophila
Sugiura, Hiroki; Dickinson, Michael H.
2009-01-01
Sideslip force, longitudinal force, rolling moment, and pitching moment generated by tethered fruit flies, Drosophila melanogaster, were measured during optomotor reactions within an electronic flight simulator. Forces and torques were acquired by optically measuring the angular deflections of the beam to which the flies were tethered using a laser and a photodiode. Our results indicate that fruit flies actively generate both sideslip and roll in response to a lateral focus of expansion (FOE). The polarity of this behavior was such that the animal's aerodynamic response would carry it away from the expanding pattern, suggesting that it constitutes an avoidance reflex or centering response. Sideslip forces and rolling moments were sinusoidal functions of FOE position, whereas longitudinal force was proportional to the absolute value of the sine of FOE position. Pitching moments remained nearly constant irrespective of stimulus position or strength, with a direction indicating a tonic nose-down pitch under tethered conditions. These experiments expand our understanding of the degrees of freedom that a fruit fly can actually control in flight. PMID:19300507
Dependence of high-order-harmonic generation on dipole moment in Si O2 crystals
NASA Astrophysics Data System (ADS)
Yu, Chao; Zhang, Xirui; Jiang, Shicheng; Cao, Xu; Yuan, Guanglu; Wu, Tong; Bai, Lihua; Lu, Ruifeng
2016-07-01
High-order-harmonic generation in α-quartz Si O2 is theoretically investigated under a strong laser field by solving the extended semiconductor Bloch equations. The accurate band structures as well as dipole moments between different bands are obtained from state-of-the-art first-principles calculations. We find that the shapes of k -space-dependent dipole moments play an important role in harmonic generation. The calculated results show that harmonic conversion efficiency is significantly enhanced and the cutoff energy is distinctly increased when the dipole moments change greatly along a valley in the k direction in the solid. Based on that dependence on the dipole moment, we also show that symmetry groups greatly affect the harmonic spectra from the solid materials. Moreover, a two-color synthesized field is used to achieve a supercontinuum harmonic spectrum near the cutoff region, and isolated attosecond pulses can be obtained directly by filtering out the harmonic radiation. We hope the contribution presented in this work provides a useful reference for future studies on laser-crystal interactions.
The measurement of the anomalous magnetic moment of the muon at Fermilab
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.
The Measurement of the Anomalous Magnetic Moment of the Muon at Fermilab a)
NASA Astrophysics Data System (ADS)
Logashenko, I.; Grange, J.; Winter, P.; Carey, R. M.; Hazen, E.; Kinnaird, N.; Miller, J. P.; Mott, J.; Roberts, B. L.; Crnkovic, J.; Morse, W. M.; Sayed, H. Kamal; Tishchenko, V.; Druzhinin, V. P.; Shatunov, Y. M.; Bjorkquist, R.; Chapelain, A.; Eggert, N.; Frankenthal, A.; Gibbons, L.; Kim, S.; Mikhailichenko, A.; Orlov, Y.; Rider, N.; Rubin, D.; Sweigart, D.; Allspach, D.; Barzi, E.; Casey, B.; Convery, M. E.; Drendel, B.; Freidsam, H.; Johnstone, C.; Johnstone, J.; Kiburg, B.; Kourbanis, I.; Lyon, A. L.; Merritt, K. W.; Morgan, J. P.; Nguyen, H.; Ostiguy, J.-F.; Para, A.; Polly, C. C.; Popovic, M.; Ramberg, E.; Rominsky, M.; Soha, A. K.; Still, D.; Walton, T.; Yoshikawa, C.; Jungmann, K.; Onderwater, C. J. G.; Debevec, P.; Leo, S.; Pitts, K.; Schlesier, C.; Anastasi, A.; Babusci, D.; Corradi, G.; Hampai, D.; Palladino, A.; Venanzoni, G.; Dabagov, S.; Ferrari, C.; Fioretti, A.; Gabbanini, C.; Di Stefano, R.; Marignetti, S.; Iacovacci, M.; Mastroianni, S.; Di Sciascio, G.; Moricciani, D.; Cantatore, G.; Karuza, M.; Giovanetti, K.; Baranov, V.; Duginov, V.; Khomutov, N.; Krylov, V.; Kuchinskiy, N.; Volnykh, V.; Gaisser, M.; Haciomeroglu, S.; Kim, Y.; Lee, S.; Lee, M.; Semertzidis, Y. K.; Won, E.; Fatemi, R.; Gohn, W.; Gorringe, T.; Bowcock, T.; Carroll, J.; King, B.; Maxfield, S.; Smith, A.; Teubner, T.; Whitley, M.; Wormald, M.; Wolski, A.; Al-Kilani, S.; Chislett, R.; Lancaster, M.; Motuk, E.; Stuttard, T.; Warren, M.; Flay, D.; Kawall, D.; Meadows, Z.; Syphers, M.; Tarazona, D.; Chupp, T.; Tewlsey-Booth, A.; Quinn, B.; Eads, M.; Epps, A.; Luo, G.; McEvoy, M.; Pohlman, N.; Shenk, M.; de Gouvea, A.; Welty-Rieger, L.; Schellman, H.; Abi, B.; Azfar, F.; Henry, S.; Gray, F.; Fu, C.; Ji, X.; Li, L.; Yang, H.; Stockinger, D.; Cauz, D.; Pauletta, G.; Santi, L.; Baessler, S.; Frlez, E.; Pocanic, D.; Alonzi, L. P.; Fertl, M.; Fienberg, A.; Froemming, N.; Garcia, A.; Hertzog, D. W.; Kammel, P.; Kaspar, J.; Osofsky, R.; Smith, M.; Swanson, E.; Lynch, K.
2015-09-01
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. Here, we discuss the details of the future measurement and its current status.
The Measurement of the Anomalous Magnetic Moment of the Muon at Fermilab
Logashenko, I.; et al.
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. Here, we discuss the details of the future measurement and its current status.
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.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
Franz Gross, Gilberto Ramalho, Kazuo Tsushima
2010-06-01
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 $Q^2=0$.
Analyzing power in pion-proton bremsstrahlung, and the. Delta. sup ++ (1232) magnetic moment
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.
Self-organization of magnetic moments in dipolar chains with restricted degrees of freedom
NASA Astrophysics Data System (ADS)
Pshenichnikov, Alexander F.; Kuznetsov, Andrey A.
2015-10-01
Equilibrium behavior of a single chain of dipolar spheres is investigated by the method of molecular dynamics in a wide range of the dipolar coupling constant λ . Two cases are considered: rodlike and flexible chains. In the first case, particle centers are immovably fixed on one axis, but their magnetic moments retain absolute orientational freedom. It has been found that at λ ≳1.5 particle moments are chiefly aligned parallel to the chain axis, but the total moment of the chain continuously changes its sign with some mean frequency, which exponentially decreases with the growth of λ . Such behavior of the rodlike chain is analogous to the Néel relaxation of a superparamagnetic particle with a finite energy of magnetic anisotropy. In the flexible chain particles are able to move in the three-dimensional space, but the distance between centers of the first-nearest neighbors never exceeds a given limiting value rmax. If rmax≃d (d is the particle diameter) then the most probable shape of the chain of five or more particles at λ ≳6 is that of a ring. The behavior of chains with rmax≥2 d is qualitatively different: At λ ≃4 long chains collapse into dense quasispherical globules and at λ ≳8 these globules take toroidal configuration with a spontaneous azimuthal ordering of magnetic dipoles. With the increase of rmax to larger values (rmax>10 d ) globules expand and break down to form separate rings.
Electrical tuning of valley magnetic moment through symmetry control in bilayer MoS2
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.
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.
Leptophilic dark matter and the anomalous magnetic moment of the muon
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.
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.
Leptophilic dark matter and the anomalous magnetic moment of the muon
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
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.
Regular and chaotic dynamics of a chain of magnetic dipoles with moments of inertia
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.
Nuclear Magnetic Moment of {sup 210}Fr: A Combined Theoretical and Experimental Approach
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.
Flipping of magnetic moments induced by the first-order phase transition in MnAs disks on GaAs(001)
NASA Astrophysics Data System (ADS)
Takagaki, Y.; Herfort, J.; Däweritz, L.; Ploog, K. H.
2006-12-01
The relaxation of magnetization in MnAs nanomagnets fabricated on GaAs(001) substrates consists of three exponential decays that are associated with the first-order phase transition between the ferromagnetic and nonmagnetic phases of MnAs and fast and slow flipping processes of magnetic moments. Not only the phase-transition component but also the fast-relaxation component become appreciable in the narrow temperature range of the thermal hysteresis of the phase transition. The magnetic moments are suggested to be rotated by virtual phase-transition processes. A brief expansion of the lattice constants of MnAs through the magnetic-field-induced phase transition is found to generate a memory effect and permanently elongate the decay times.
Density functional study on d-orbital characters of the Fe magnetic moment in BaFe2As2
NASA Astrophysics Data System (ADS)
Oh, Hyungju; Choi, Hyoung Joon
2012-02-01
There have been many published papers related on the orbital characters of band structures in the iron-based superconductors. However, the orbital characters of the Fe magnetic moment still remain unrevealed. By performing first-principles calculations of the electronic and magnetic properties with constraint on the real space shape of Fe magnetic moments, we study the d-orbital characters of the Fe magnetic moment in BaFe2As2. We compare obtained band structures with published angle-resolved photoemission spectroscopy (ARPES) result, and propose that the Fe magnetic moment in BaFe2As2 has in-plane dxy character. This work was supported by the NRF of Korea (Grant Nos. 2009-0081204 and 2011-0018306). Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2011-C3-05)
NASA Astrophysics Data System (ADS)
Granroth, G. E.; Aczel, A. A.; Fernandez-Baca, J. A.; Nagler, S. E.
2013-03-01
Many experimental features in magnetic superconductors are also present when these complex materials are in the normal state. Therefore studies of simpler itinerant magnets may help provide understanding of these phenomena. We chose to study Gd as it is has an ~ 0 . 6μB itinerant moment in addition to a ~ 7 . 0μB localized moment. The SEQUOIA spectrometer, at the Spallation Neutron Source at Oak Ridge National Laboratory, was used in fine resolution mode with Ei=50 meV neutrons, to measure the magnetic excitations in a 12 gm 160Gd single crystal. The crystal was mounted with the h 0 l plane horizontal and rotated around the vertical axis to map out the excitations. The measured magnetic structure factor for the acoustic modes in the hh 0 direction has an intensity step at h ~ 0 . 3 . Electronic band structure calculations (W. M. Temmerman and P. A. Sterne, J. Phys: Condes. Matter,2, 5529 (1990)) show this Q position to be near several band crossings of the Fermi surface. A detailed analysis, including instrumental resolution, is presented to clarify any relationship between the magnetic structure factor and the electronic band structure. This work was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.
Chiral structures and tunable magnetic moments in 3d transition metal doped Pt6 clusters
NASA Astrophysics Data System (ADS)
Zhang, Xiu-Rong; Yang, Xing; Ding, Xun-Lei
2012-09-01
The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt6 (M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) are systematically studied by using the relativistic all-electron density functional theory with the generalized gradient approximation. Most of the doped clusters show larger binding energies than the pure Pt7 cluster, which indicates that the doping of the transition metal atom can stabilize the pure platinum cluster. The results of the highest occupied molecular orbital (HOMO)—lowest unoccupied molecular orbital (LUMO) gaps suggest that the doped clusters can have higher chemical activities than the pure Pt7 cluster. The magnetism calculations demonstrate that the variation range of the magnetic moments of the MPt6 clusters is from 0 μB to 7 μB, revealing that the MPt6 clusters have potential utility in designing new spintronic nanomaterials with tunable magnetic properties.
NASA Astrophysics Data System (ADS)
Roshanzamir-Nikou, M.; Goudarzi, H.
2016-02-01
A strong magnetic field significantly affects the intrinsic magnetic moment of fermions. In quantum electrodynamics, it was shown that the anomalous magnetic moment of an electron arises kinematically, while it results from a dynamical interaction with an external magnetic field for hadrons (proton). Taking the anomalous magnetic moment of a fermion into account, we find an exact expression for the boundstate energy and the corresponding eigenfunctions of a two-dimensional nonrelativistic spin-1/2 harmonic oscillator with a centripetal barrier (known as the isotonic oscillator) including an Aharonov-Bohm term in the presence of a strong magnetic field. We use the Laplace transform method in the calculations. We find that the singular solution contributes to the phase of the wave function at the origin and the phase depends on the spin and magnetic flux.
Remote sensing of the magnetic moment of uranus: predictions for voyager.
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
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.
Itinerancy enhanced quantum fluctuation of magnetic moments in iron-based superconductors
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
Itinerancy enhanced quantum fluctuation of magnetic moments in iron-based superconductors
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.
Itinerancy-enhanced quantum fluctuation of magnetic moments in iron-based superconductors.
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
Itinerancy-Enhanced Quantum Fluctuation of Magnetic Moments in Iron-Based Superconductors
NASA Astrophysics Data System (ADS)
Tam, Yu-Ting; Yao, Dao-Xin; Ku, Wei
2015-09-01
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.
The electrostatic potential generated by topological atoms. II. Inverse multipole moments.
Rafat, M; Popelier, P L A
2005-11-22
Quantum chemical topology defines finite atoms, whose bounded electron density generates a well-defined electrostatic potential. A multipole expansion based on spherical tensors provides a potential that is formally convergent outside the divergence sphere. Part I of this series [P. L. A. Popelier and M. Rafat, Chem. Phys. Lett.376, 148 (2003)] showed that a continuous multipole expansion expands the convergence region, thereby allowing the electrostatic potential to be evaluated at short range. Here, we propose a different method, based on "inverse" multipole moments, enabling an expansion that converges everywhere. These moments are defined by inverse (i.e., negative) powers of the magnitude of the position vector describing the electron density inside the atom. We illustrate this technique on nitrogen in N(2), oxygen in H(2)O, and oxygen in the phenolic group of the amino acid tyrosine. The proposed method constitutes a considerable advance over the method presented in Part I. PMID:16351236
NASA Astrophysics Data System (ADS)
Vas'kovskiy, V. O.; Adanakova, O. A.; Balymov, K. G.; Kulesh, N. A.; Svalov, A. V.; Stepanova, E. A.
2015-06-01
A systematic investigation of the magnetic properties of amorphous films in ( RE) x Co100 - x binary systems in the ground state with rare-earth elements ( RE) of different types has been performed. The concentration dependences of the average atomic magnetic moments of cobalt ( m Co), gadolinium ( m Gd), and terbium ( m Tb) have been determined from the analysis of the spontaneous magnetization of the films with a nonmagnetic rare-earth element (La), a rare-earth element with a spherical electron shell (Gd), and a rareearth element with a large orbital magnetic moment (Tb). It has been shown that, in the range 0 < x < 50 at %, the magnetic moment m Co decreases from 1.7 μB to zero, the magnetic moment m Gd remains unchanged and almost coincides with the magnetic moment of the free atom (7 μB), and the value of m Tb decreases monotonically, but the rate of decrease depends on the method of the sample preparation. The revealed regularities are associated with the concentration change in the electronic structure of cobalt and with the specificity of the magnetic structure of the films, which has a ferromagnetic, ferrimagnetic, or sperimagnetic character for samples containing La, Gd, or Tb, respectively.
Atomic moments in Mn2CoAl thin films analyzed by X-ray magnetic circular dichroism
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.
Gravitational electrical generator on magnetic fluid cushion
NASA Astrophysics Data System (ADS)
Călin Popa, Nicolae; Siblini, Ali; Jorat, Luc
1999-07-01
The paper describes the possibility to capture the energy of the vertical movement of the ocean waves, using a gravitational electrical generator on magnetic fluid cushion. This is constructed from a permanent magnet in a magnetic fluid shell, which, under the ocean waves action, is moving by translation inside a hermetically sealed tube.
Magnetic moment of the 2083 keV level of 140Ce
NASA Astrophysics Data System (ADS)
Ohkubo, Y.; Taniguchi, A.; Xu, Q.; Tanigaki, M.; Shimizu, N.; Otsuka, T.
2013-04-01
For the magnetic moment of the 2083 keV level of 140Ce, there are four published data, all obtained by applying an external magnetic field of less than 5 T to a liquid sample containing 140La using the time-differential perturbed angular correlation (TDPAC) technique. Although these four values are consistent within two times their uncertainties (2σ), the range of values in 2σ extends from μ=+3.0 to +5.2 (in units of nuclear magneton, μN). This time, the TDPAC technique was successfully applied to the 2083 keV level of 140Ce implanted in an Fe foil. The magnetic moment of this level was determined to be μ=+4.00(20)μN, employing the known hyperfine field at 141Ce in Fe, -41(2) T, which agrees very well with one of the values, μ=+4.06(15)μN. The present value is compared with two shell-model calculations.
NASA Astrophysics Data System (ADS)
Deák, A.; Simon, E.; Balogh, L.; Szunyogh, L.; dos Santos Dias, M.; Staunton, J. B.
2014-06-01
We develop a self-consistent relativistic disordered local moment (RDLM) scheme aimed at describing finite-temperature magnetism of itinerant metals from first principles. Our implementation in terms of the Korringa-Kohn-Rostoker multiple-scattering theory and the coherent potential approximation allows us to relate the orientational distribution of the spins to the electronic structure, thus a self-consistent treatment of the distribution is possible. We present applications for bulk bcc Fe, L10-FePt, and FeRh ordered in the CsCl structure. The calculations for Fe show significant variation of the local moments with temperature, whereas according to the mean-field treatment of the spin fluctuations the Curie temperature is overestimated. The magnetic anisotropy of FePt alloys is found to depend strongly on intermixing between nominally Fe and Pt layers, and it shows a power-law behavior as a function of magnetization for a broad range of chemical disorder. In the case of FeRh we construct a lattice constant vs temperature phase diagram and determine the phase line of metamagnetic transitions based on self-consistent RDLM free-energy curves.
NMR absolute shielding scale and nuclear magnetic dipole moment of (207)Pb.
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
(83)Kr nuclear magnetic moment in terms of that of (3)He.
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
Kong, Dali; Lin, Wei; Pan, Yongxin; Zhang, Keke
2014-01-01
We investigate the swimming motion of rod-shaped magnetotactic bacteria affiliated with the Nitrospirae phylum in a viscous liquid under the influence of an externally imposed, time-dependent magnetic field. By assuming that fluid motion driven by the translation and rotation of a swimming bacterium is of the Stokes type and that inertial effects of the motion are negligible, we derive a new system of the twelve coupled equations that govern both the motion and orientation of a swimming rod-shaped magnetotactic bacterium with a growing magnetic moment in the laboratory frame of reference. It is revealed that the initial pattern of swimming motion can be strongly affected by the rate of the growing magnetic moment. It is also revealed, through comparing mathematical solutions of the twelve coupled equations to the swimming motion observed in our laboratory experiments with rod-shaped magnetotactic bacteria, that the laboratory trajectories of the swimming motion can be approximately reproduced using an appropriate set of the parameters in our theoretical model. PMID:24523716
Kong, Dali; Lin, Wei; Pan, Yongxin; Zhang, Keke
2014-01-01
We investigate the swimming motion of rod-shaped magnetotactic bacteria affiliated with the Nitrospirae phylum in a viscous liquid under the influence of an externally imposed, time-dependent magnetic field. By assuming that fluid motion driven by the translation and rotation of a swimming bacterium is of the Stokes type and that inertial effects of the motion are negligible, we derive a new system of the twelve coupled equations that govern both the motion and orientation of a swimming rod-shaped magnetotactic bacterium with a growing magnetic moment in the laboratory frame of reference. It is revealed that the initial pattern of swimming motion can be strongly affected by the rate of the growing magnetic moment. It is also revealed, through comparing mathematical solutions of the twelve coupled equations to the swimming motion observed in our laboratory experiments with rod-shaped magnetotactic bacteria, that the laboratory trajectories of the swimming motion can be approximately reproduced using an appropriate set of the parameters in our theoretical model. PMID:24523716
NASA Astrophysics Data System (ADS)
Alling, B.; Körmann, F.; Grabowski, B.; Glensk, A.; Abrikosov, I. A.; Neugebauer, J.
2016-06-01
We study the impact of lattice vibrations on magnetic and electronic properties of paramagnetic bcc and fcc iron at finite temperature, employing the disordered local moments molecular dynamics (DLM-MD) method. Vibrations strongly affect the distribution of local magnetic moments at finite temperature, which in turn correlates with the local atomic volumes. Without the explicit consideration of atomic vibrations, the mean local magnetic moment and mean field derived magnetic entropy of paramagnetic bcc Fe are larger compared to paramagnetic fcc Fe, which would indicate that the magnetic contribution stabilizes the bcc phase at high temperatures. In the present study we show that this assumption is not valid when the coupling between vibrations and magnetism is taken into account. At the γ -δ transition temperature (1662 K), the lattice distortions cause very similar magnetic moments of both bcc and fcc structures and hence magnetic entropy contributions. This finding can be traced back to the electronic densities of states, which also become increasingly similar between bcc and fcc Fe with increasing temperature. Given the sensitive interplay of the different physical excitation mechanisms, our results illustrate the need for an explicit consideration of vibrational disorder and its impact on electronic and magnetic properties to understand paramagnetic Fe. Furthermore, they suggest that at the γ -δ transition temperature electronic and magnetic contributions to the Gibbs free energy are extremely similar in bcc and fcc Fe.
Multiferroicity and spiral magnetism in FeVO{sub 4} with quenched Fe orbital moments
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.
Measurement of the magnetic moment of the 10{sup +} isomer in {sup 132}Ba
Harissopulos, S.; Gelberg, A.; Dewald, A.; Hass, M.; Weissman, L.; Broude, C.
1995-10-01
The magnetic moment of the 10{sup +} isomeric state of {sup 132}Ba at 3115 keV was measured as {ital g}={minus}0.156(11). A 60 MeV {sup 12}C beam from the Koffler Pelletron accelerator at the Weizmann Institute was used in the reaction {sup 124}Sn({sup 12}C,4{ital n}){sup 132}Ba. The measured {ital g} factor confirms the ({nu}{ital h}{sub 11/2}){sup {minus}2} configuration of the level. The result is compared with other {ital g} factors in neighboring {ital N}=76 isotones.
Z = 50 core stability in 110Sn from magnetic-moment and lifetime measurements
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.
Magnetic Moments measurement and rare isotope beams: one example ^126Sn
NASA Astrophysics Data System (ADS)
Kumbartzki, Gerfried; Benczer-Koller, Noemie
2012-10-01
An assessment of the current state of measurements of magnetic moments of ps excited states with low intensity rare isotope beams will be given. ^126Sn was our last experiment before HRIBF/Oak Ridge ceased operation. Results of only a few experiments using the transient field technique and/or recoil in vacuum attenuation have been published. Each experiment posed special challenges and required specific modifications to the setup. The challenges and limitations learned and an outlook for future experiments will be presented.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
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 $Q^2=0$.
Using baryon octet magnetic moments and masses to fix the pion cloud contribution
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
Green's function theory of orbital magnetic moment of interacting electrons in solids
NASA Astrophysics Data System (ADS)
Aryasetiawan, F.; Karlsson, K.; Miyake, T.
2016-04-01
A general formula for the orbital magnetic moment of interacting electrons in solids is derived using the many-electron Green's function method. The formula factorizes into two parts, a part that contains the information about the one-particle band structure of the system and a part that contains the effects of exchange and correlations carried by the Green's function. The derived formula provides a convenient yet rigorous means of including the effects of exchange and correlations beyond the commonly used local density approximation of density functional theory.
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.
Lattice calculation of hadronic light-by-light contribution to the muon anomalous magnetic moment
NASA Astrophysics Data System (ADS)
Blum, Thomas; Christ, Norman; Hayakawa, Masashi; Izubuchi, Taku; Jin, Luchang; Lehner, Christoph
2016-01-01
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. 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.
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.
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.
Lattice calculation of hadronic light-by-light contribution to the muon anomalous magnetic moment
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.
Magnetic moment of the majorana neutrino in the left-right symmetric model
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.
Hyperfine field of einsteinium in iron and nuclear magnetic moment of {sup 254}Es
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}.
Electron Anomalous Magnetic Moment in Basis Light-Front Quantization Approach
Zhao, Xingbo; Honkanen, Heli; Maris, Pieter; Vary, James P.; Brodsky, Stanley J.; /SLAC
2012-02-17
We apply the Basis Light-Front Quantization (BLFQ) approach to the Hamiltonian field theory of Quantum Electrodynamics (QED) in free space. We solve for the mass eigenstates corresponding to an electron interacting with a single photon in light-front gauge. Based on the resulting non-perturbative ground state light-front amplitude we evaluate the electron anomalous magnetic moment. The numerical results from extrapolating to the infinite basis limit reproduce the perturbative Schwinger result with relative deviation less than 1.2%. We report significant improvements over previous works including the development of analytic methods for evaluating the vertex matrix elements of QED.
Magnetic moment of the 4/sub 1//sup +/ state in /sup 20/Ne
Bright, T.; Ballon, D.; Saxena, R.J.; Niv, Y.; Benczer-Koller, a.N.
1984-08-01
The magnetic moment of the 4/sub 1//sup +/ state in /sup 20/Ne was measured by the transient field technique, and the transient field was calibrated in a simultaneous measurement on the 2/sub 1//sup +/ state. The resulting g(4/sub 1//sup +/) = 0.49 +- 0.34 is in agreement with the shell model description of /sup 20/Ne. The magnitude of the transient field measured in previous experiments on O, Ne, and Mg ions traversing iron foils was reexamined and appears to be in good agreement with the results of this experiment.
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.
Baryon magnetic moments in alternate 1/N{sub c} expansions
Lebed, Richard F.; TerBeek, Russell H.
2011-01-01
Recent work shows not only the necessity of a 1/N{sub c} expansion to explain the observed mass spectrum of the lightest baryons, but also that at least two distinct large N{sub c} expansions, in which quarks transform under either the color-fundamental or the two-index antisymmetric representation of SU(N{sub c}), work comparably well. Here we show that the baryon magnetic moments do not support this ambivalence; they strongly prefer the color-fundamental 1/N{sub c} expansion, providing experimental evidence that nature decisively distinguishes among 1/N{sub c} expansions for this observable.
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.
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.
A linear magnetic motor and generator
NASA Technical Reports Server (NTRS)
Studer, P. A.
1980-01-01
In linear magnetic motor and generator suitable for remote and hostile environments, magnetic forces drive reciprocating shaft along its axis. Actuator shaft is located in center of cylindrical body and may be supported by either contacting or noncontacting bearings. When device operates as bidirectional motor, drive coil selectively adds and subtracts magnetic flux to and from flux paths, producing forces that drive actuator along axis. When actuator is driven by external reciprocating engine, device becomes ac generator.
NASA Technical Reports Server (NTRS)
Srnka, L. J.
1976-01-01
The acquisition of thermoremanent magnetization (TRM) by a cooling spherical shell is studied for internal magnetizing dipole fields, using Runcorn's (1975) theorems on magnetostatics. If the shell cools progressively inward, inner regions acquire TRM in a net field composed of the dipole source term plus a uniform field due to the outer magnetized layers. In this case, the global dipole moment and external remanent field are nonzero when the whole shell has cooled below the Curie point and the source dipole has disappeared. The remanent field outside the shell is found to depend on the thickness, radii, and cooling rate of the shell, as well as the coefficient of TRM and the intensity of the magnetizing field. Some implications for the moon's remanent dipole moment are discussed.
Moment enhancement in dilute magnetic semiconductors: MnxSi1-x with x = 0.1%
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.
Time-reversal symmetry violation in molecules induced by nuclear magnetic quadrupole moments.
Flambaum, V V; DeMille, D; Kozlov, M G
2014-09-01
Recent measurements in paramagnetic molecules improved the limit on the electron electric dipole moment (EDM) by an order of magnitude. Time-reversal (T) and parity (P) symmetry violation in molecules may also come from their nuclei. We point out that nuclear T, P-odd effects are amplified in paramagnetic molecules containing deformed nuclei, where the primary effects arise from the T, P-odd nuclear magnetic quadrupole moment (MQM). We perform calculations of T, P-odd effects in the molecules TaN, ThO, ThF+, HfF+, YbF, HgF, and BaF induced by MQMs. We compare our results with those for the diamagnetic TlF molecule, where the T, P-odd effects are produced by the nuclear Schiff moment. We argue that measurements in molecules with MQMs may provide improved limits on the strength of T, P-odd nuclear forces, on the proton, neutron, and quark EDMs, on quark chromo-EDMs, and on the QCD θ term and CP-violating quark interactions. PMID:25238355
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
NASA Astrophysics Data System (ADS)
Sveshnikov, K. A.; Khomovskii, D. I.
2013-03-01
The behavior of electron energy levels in hydrogen-like atoms is studied while taking into account the nonperturbative interaction between the radiative component of the magnetic moment of a free electron Δ g free and the Coulomb field of an atomic nucleus with charge Z, including those with Z > 137. It is shown that for Zα ≪ 1 the energy-level shift is rather effectively determined through the matrix elements of the corresponding Dirac-Pauli operator with relativistic Coulomb wave functions. At the same time, for superheavy nuclei with Z ˜ 170, this shift, generated by Δ g free, is genuinely nonperturbative, behaves like ˜ Z 5 near the threshold of negative continuum, exceeds all the estimates of radiative corrections coming from vacuum polarization and electron self-energy known so far, and turns out to be at least of the same order as the effects of nuclear charge screening by filled electron shells.
Non-Fermi-Liquid Behavior in Metallic Quasicrystals with Local Magnetic Moments.
Andrade, Eric C; Jagannathan, Anuradha; Miranda, Eduardo; Vojta, Matthias; Dobrosavljević, Vladimir
2015-07-17
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 T, leading to a power-law distribution of Kondo temperatures P(T(K))∼T(K)(α-1), with a nonuniversal exponent α, in a remarkable similarity to the Kondo-disorder scenario found in disordered heavy-fermion metals. For α<1, the resulting singular P(T(K)) induces non-Fermi-liquid behavior with diverging thermodynamic responses as T→0. PMID:26230810
Non-Fermi-Liquid Behavior in Metallic Quasicrystals with Local Magnetic Moments
NASA Astrophysics Data System (ADS)
Andrade, Eric C.; Jagannathan, Anuradha; Miranda, Eduardo; Vojta, Matthias; Dobrosavljević, Vladimir
2015-07-01
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 T , leading to a power-law distribution of Kondo temperatures P (TK)˜TKα -1, with a nonuniversal exponent α , in a remarkable similarity to the Kondo-disorder scenario found in disordered heavy-fermion metals. For α <1 , the resulting singular P (TK) induces non-Fermi-liquid behavior with diverging thermodynamic responses as T →0 .
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.
Determination of the Magnetic Structure of Yb3Pt4:a k=0 Local-moment Antiferromagnet
Janssen, T.; Kim, M.S.; Park, K.S.; Wu, L.; Marques, C.; Bennett, M.C.; Chen, Y.; Li, J.; Huang, Q.; Lynn, J.W.; Aronson, M.C.
2010-02-01
We have used neutron-diffraction measurements to study the zero-field magnetic structure of the intermetallic compound Yb{sub 3}Pt{sub 4}, which was earlier found to order antiferromagnetically at the Neel temperature T{sub N} = 2.4 K, and displays a field-driven quantum-critical point at 1.6 T. In Yb{sub 3}Pt{sub 4}, the Yb moments sit on a single low-symmetry site in the rhombohedral lattice with space group R{bar 3}. The Yb ions form octahedra with edges that are twisted with respect to the hexagonal unit cell, a twisting that results in every Yb ion having exactly one Yb nearest neighbor. Below T{sub N}, we found new diffracted intensity due to a k=0 magnetic structure. This magnetic structure was compared to all symmetry-allowed magnetic structures and was subsequently refined. The best-fitting magnetic-structure model is antiferromagnetic and involves pairs of Yb nearest neighbors on which the moments point almost exactly toward each other. This structure has moment components within the ab plane as well as parallel to the c axis although the easy magnetization direction lies in the ab plane. Our magnetization results suggest that besides the crystal-electric-field anisotropy, anisotropic exchange favoring alignment along the c axis is responsible for the overall direction of the ordered moments. The magnitude of the ordered Yb moments in Yb{sub 3}Pt{sub 4} is 0.81 {mu}{sub B}/Yb at 1.4 K. The analysis of the bulk properties, the size of the ordered moment, and the observation of well-defined crystal-field levels argue that the Yb moments are spatially localized in zero field.
Magnetic g_e-FACTORS and Electric Dipole Moments of Lanthanide Monoxides: PrO
NASA Astrophysics Data System (ADS)
Wang, Hailing; Steimle, Timothy C.; Linton, Colan
2009-06-01
The very complex optical spectra of the lanthanide monoxides are caused by the insensitivity of the electronic energies to the numerous possible arrangements of the Ln^{2+} electrons in the 4f and 6s orbitals. Disentangling the complex optical spectra may be aided by using simple Ligand Field Theory(LFT) to establish the global electronic structure for the low-lying electronic states. A comparison of experimentally determined permanent electric dipole moments, μ_{el}, and magnetic dipole moments, μ_{m}, is an effective means of sorting this myriad of states and assessing the quality of LFT and other electronic structure methodologies. Here we report on the determination of the permanent electric dipole moments, μ_{el}, and magnetic g{_e}-factors for the X_{2}(Ω = 4.5) and [18.1] (Ω = 5.5) states of PrO from the analysis of the optical Stark and Zeeman spectra. The g_{e}-factors are compared with those computed using wavefunctions predicted from ligand field theory. The μ_{el} value for the X_{2}(Ω = 4.5) state is compared to ab initio, and density functional predictions and with the experimental values of other lanthanide monoxides. A phenomenological fit of μ_{el} for the entire series of LnO is used to predict μ_{el} for the isovalent actinide monoxide series. Carette, P.,; Hocquet,A. J. Mol. Spectrosc. 131 301, 1988. Dolg, M.; Stoll, H. Theor. Chim. Acta. 75,369, 1989. Wu, Z.; Guan, W. Meng, J. Su, Z. J. Cluster Science 18 444, 2007.
Electron contribution to the muon anomalous magnetic moment at four loops
NASA Astrophysics Data System (ADS)
Kurz, Alexander; Liu, Tao; Marquard, Peter; Smirnov, Alexander V.; Smirnov, Vladimir A.; Steinhauser, Matthias
2016-03-01
We present results for the QED contributions to the anomalous magnetic moment of the muon containing closed electron loops. The main focus is on perturbative corrections at four-loop order where the external photon couples to the external muon. Furthermore, all four-loop contributions involving simultaneously a closed electron and tau loop are computed. In combination with our recent results on the light-by-light-type corrections (see Ref. [1]), the complete four-loop electron-loop contribution to the anomalous magnetic moment of the muon has been obtained with an independent calculation. Our calculation is based on an asymptotic expansion in the ratio of the electron and the muon mass and shows the importance of higher-order terms in this ratio. We perform a detailed comparison with results available in the literature and find good numerical agreement. As a byproduct, we present analytic results for the on-shell muon mass and wave function renormalization constants at three-loop order including massive closed electron and tau loops, which we also calculated using the method of asymptotic expansion.
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.
Magnetic moments of JP = {{3}/{2}} + decuplet baryons using the statistical model
NASA Astrophysics Data System (ADS)
Kaur, Amanpreet; Upadhyay, Alka
2016-04-01
A suitable wave function for the baryon decuplet is framed with the inclusion of the sea containing quark-gluon Fock states. Relevant operator formalism is applied to calculate the magnetic moments of J P = {{3}/{2}} + baryon decuplet. The statistical model assumes the decomposition of the baryonic state in various quark-gluon Fock states and is used in combination with the detailed balance principle to find the relative probabilities of these Fock states in flavor, spin and color space. The upper limit to the gluon is restricted to three with the possibility of emission of quark-antiquark pairs. We study the importance of strangeness in the sea (scalar, vector and tensor) and its contribution to the magnetic moments. Our approach has confirmed the scalar-tensor sea dominancy over the vector sea. Various modifications in the model are used to check the validity of the statistical approach. The results are matched with the available theoretical data. A good consistency with the experimental data has been achieved for Δ^{{++}}_{} , Δ^{{+}}_{} and Ω^{{-}}_{}.
Lin, D.; Liou, M.K. ); Ding, Z.M. Department of Physics, Normandale Community College, Bloomington, Minnesota )
1991-11-01
A bremsstrahlung amplitude in the special two-energy-two-angle (TETAS) approximation, which is relativistic, gauge invariant, and consistent with the soft-photon theorem, is derived for the pion-proton bremsstrahlung ({pi}{sup +}{ital p}{gamma}) process near the {Delta}{sup ++}(1232) resonance. In order to take into account bremsstrahlung emission from an internal {Delta}{sup ++} line with both charge and the anomalous magnetic moment {lambda}{sub {Delta}}, we have applied a radiation decomposition identity to modify Low's standard prescription for constructing a soft-photon amplitude. This modified procedure is very general; it can be used to derive the TETAS amplitude for any bremsstrahlung process with resonance. The derived TETAS amplitude is applied to calculate all {pi}{sup +}{ital p}{gamma} cross sections which can be compared with the experimental data. Treating {lambda}{sub {Delta}} as a free parameter in these calculations, we extract the experimental'' magnetic moment of the {Delta}{sup ++}, {mu}{sub {Delta}}, from recent data. The extracted values of {mu}{sub {Delta}} are (3.7--4.2){ital e}/(2{ital m}{sub {ital p}}) from the University of California, Los Angeles data and (4.6--4.9){ital e}/(2{ital m}{sub {ital p}}) from the Paul Scherrer Institute data. Here, {ital m}{sub {ital p}} is the proton mass.
Limit on the electron neutrino magnetic moment from the kuo-sheng reactor neutrino experiment.
Li, H B; Li, J; Wong, H T; Chang, C Y; Chen, C P; Fang, J M; Hu, C H; Kuo, W S; Lai, W P; Lee, F S; Lee, S C; Lin, S T; Luo, C S; Liu, Y; Qiu, J F; Sheng, H Y; Singh, V; Su, R F; Teng, P K; Tong, W S; Wang, S C; Xin, B; Yeh, T R; Yue, Q; Zhou, Z Y; Zhuang, B A
2003-04-01
A search of neutrino magnetic moment was carried out at the Kuo-Sheng Nuclear Power Station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg(-1) keV(-1) day(-1) at 12-60 keV were achieved. Based on 4712 and 1250 h of reactor ON and OFF data, respectively, the limit on the neutrino magnetic moment of mu(nu;(e))<1.3x10(-10)mu(B) at 90% confidence level was derived. An indirect bound of the nu;(e) radiative lifetime of m(3)(nu)tau(nu)>2.8x10(18) eV(3) s can be inferred. PMID:12689275
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.
NASA Technical Reports Server (NTRS)
Studer, P. A. (Inventor)
1982-01-01
A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.
Spin torque-generated magnetic droplet solitons.
Mohseni, S M; Sani, S R; Persson, J; Nguyen, T N Anh; Chung, S; Pogoryelov, Ye; Muduli, P K; Iacocca, E; Eklund, A; Dumas, R K; Bonetti, S; Deac, A; Hoefer, M A; Akerman, J
2013-03-15
Dissipative solitons have been reported in a wide range of nonlinear systems, but the observation of their magnetic analog has been experimentally challenging. Using spin transfer torque underneath a nanocontact on a magnetic thin film with perpendicular magnetic anisotropy (PMA), we have observed the generation of dissipative magnetic droplet solitons and report on their rich dynamical properties. Micromagnetic simulations identify a wide range of automodulation frequencies, including droplet oscillatory motion, droplet "spinning," and droplet "breather" states. The droplet can be controlled by using both current and magnetic fields and is expected to have applications in spintronics, magnonics, and PMA-based domain-wall devices. PMID:23493707
Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au.
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
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.
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.
The magnetic moments of vanadium impurities in alkali hosts and induced spin current in alkali films
NASA Astrophysics Data System (ADS)
Song, Funing
Thin quench-condensed films of Na, K, Rb, and Cs are covered with 1/100 of a monolayer of Vanadium. Then the V impurities are covered with several atomic layers of the host. The magnetization of the sandwiches is measured by means of the anomalous Hall effect. For V impurities on the surface of Na and K, a magnetic moment of 7 Bohr magnetons is observed. After coverage with the host, the V moment became 6.5muB for the Na host. These results contradict the favored atomic model (predicting 0.6muB) and the resonance model. The V moment on the surface and in the bulk of Rb and Cs is about 4muB and considerably smaller than the measured moments of V in Na. Furthermore, the sign of the anomalous Hall resistance changes from negative for the Na host to positive for the Cs host. This indicates a change of the electronic structure of the impurity (plus host environment) when going from Na to Cs hosts. Sandwiches of FeK and FeCs are prepared at helium temperature and under ultra-high vacuum. The mean free path within these sandwiches can exceed the film thickness by a factor of five. This implies almost perfect specular reflection of the electrons at the interfaces. Therefore, the mean free path of the film is strongly dependent on the degree of the specular reflection. Furthermore, the experiments suggest that the specular reflections for spin-up and spin-down electrons are different at the Fe interface, resulting in a spin current in the alkali films. In order to detect this current, dilute Pb impurities are condensed on top of the free surface of the alkali films. Strong spin-orbit scatterers, such as Pb, introduce an anomalous Hall effect in the presence of a spin current, which can be detected through straightforward Hall measurements. The results of the AHE experiments clearly indicate the existence of a local spin current.
Marcucci, L. E.; Pervin, M.; Pieper, S. C.; Schiavilla, R.; Wiringa, R. B.; Physics; Univ. of Pisa; Jefferson Lab.; Old Dominion Univ.
2008-01-01
Green's function Monte Carlo calculations of magnetic moments and M1 transitions including two-body meson-exchange current (MEC) contributions are reported for A 7 nuclei. The realistic Argonne v{sub 18} two-nucleon and Illinois-2 three-nucleon potentials are used to generate the nuclear wave functions. The two-body meson-exchange operators are constructed to satisfy the continuity equation with the Argonne v{sub 18} potential. The MEC contributions increase the A = 3,7 isovector magnetic moments by 16% and the A = 6,7 M1 transition rates by 17-34%, bringing them into very good agreement with the experimental data.
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
Magnetic flux transport and the sun's dipole moment - New twists to the Babcock-Leighton model
NASA Technical Reports Server (NTRS)
Wang, Y.-M.; Sheeley, N. R., Jr.
1991-01-01
The mechanisms that give rise to the sun's large-scale poloidal magnetic field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed.
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.
NASA Technical Reports Server (NTRS)
Russell, C. T.; Coleman, P. J., Jr.; Goldstein, B. E.
1982-01-01
Apollo 15 and 16 subsatellite fluxgate magnetometer data have been analyzed for all intervals in which the moon was in the lobes of the geomagnetic tail to obtain an improved estimate of the average magnitude of the induced dipole moment of the moon. The resulting set of estimates yields an induced magnetic moment of -4.23 x 10 to the 22nd Gauss-cu cm per Gauss of applied field, corresponding to a G-factor of -0.008 + or - 0.001. These measurements do not place strong constraints on the conductivity of the lunar core. The observed effects would be detected as long as the core conductivity was greater than about 10 mho/m. If the outer cool layers of the moon that are at temperatures below the effective Curie point contain little or no free iron, then these measurements are consistent with the presence of a conducting core whose radius is slightly larger than 400 km. If these outer layers of the moon contain significant amounts of free iron and hence exhibit the paramagnetism expected in such a situation the core size could be even greater.
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.
The spin and orbital contributions to the total magnetic moments of free Fe, Co, and Ni clusters
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.
Measuring the muon's anomalous magnetic moment to 0.14 ppm
NASA Astrophysics Data System (ADS)
Gray, Frederick; New (g-2 Collaboration
2011-09-01
The anomalous magnetic moment (g-2) of the muon was measured with a precision of 0.54 ppm in Experiment 821 at Brookhaven National Laboratory. A difference of 3.2 standard deviations between this experimental value and the prediction of the Standard Model has persisted since 2004; in spite of considerable experimental and theoretical effort, there is no consistent explanation for this difference. This comparison hints at physics beyond the Standard Model, but it also imposes strong constraints on those possibilities, which include supersymmetry and extra dimensions. The collaboration is preparing to relocate the experiment to Fermilab to continue towards a proposed precision of 0.14 ppm. This will require 20 times more recorded decays than in the previous measurement, with corresponding improvements in the systematic uncertainties. We describe the theoretical developments and the experimental upgrades that provide a compelling motivation for the new measurement.
Neutrino transition magnetic moments within the non-standard neutrino-nucleus interactions
NASA Astrophysics Data System (ADS)
Papoulias, D. K.; Kosmas, T. S.
2015-07-01
Tensorial non-standard neutrino interactions are studied through a combined analysis of nuclear structure calculations and a sensitivity χ2-type of neutrino events expected to be measured at the COHERENT experiment, recently planned to operate at the Spallation Neutron Source (Oak Ridge). Potential sizeable predictions on transition neutrino magnetic moments and other electromagnetic parameters, such as neutrino milli-charges, are also addressed. The non-standard neutrino-nucleus processes, explored from nuclear physics perspectives within the context of quasi-particle random phase approximation, are exploited in order to estimate the expected number of events originating from vector and tensor exotic interactions for the case of reactor neutrinos, studied with TEXONO and GEMMA neutrino detectors.
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.
Using magnetic moments to study the nuclear structure of I{>=} 2 states
Torres, D. A.
2013-05-06
The experimental study of magnetic moments for nuclear states near the ground state, I{>=} 2, provides a powerful tool to test nuclear structure models. Traditionally, the use of Coulomb excitation reactions have been utilized to study low spin states, mostly I= 2. The use of alternative reaction channels, such as {alpha} transfer, for the production of radioactive species that, otherwise, will be only produced in future radioactive beam facilities has proved to be an alternative to measure not only excited states with I > 2, but to populate and study long-live radioactive nuclei. This contribution will present the experimental tools and challenges for the use of the transient field technique for the measurement of g factors in nuclear states with I{>=} 2, using Coulomb excitation and {alpha}-transfer reactions. Recent examples of experimental results near the N= 50 shell closure, and the experimental challenges for future implementations with radioactive beams, will be discussed.
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.
Kumar, Ashok; Scott, J. F.; Katiyar, R. S.
2011-01-01
Here, we report the tuning of room-temperature magnon frequencies from 473 GHz to 402 GHz (14%) and magnetic moment from 4 to 18 emu∕cm3 at 100 Oe under the application of external electric fields (E) across interdigital electrodes in BiFeO3 (BFO) thin films. A decrease in magnon frequencies and increase in phonon frequencies were observed with Magnon and phonon Raman intensities are asymmetric with polarity, decreasing with positive E (+E) and increasing with negative E (−E) where polarity is with respect to in-plane polarization P. The magnetoelectric coupling (α) is proved to be linear and a rather isotropic α = 8.5 × 10−12 sm−1. PMID:21901050
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.
Search for high moment soft magnetic materials: FeZrN (abstract)
Chakraborty, A.; Bellesis, G.H.; Mountfield, K.R.; Lambeth, D.N.; Kryder, M.H.
1996-04-01
FeN materials exhibiting high moment, low coercivity and small magnetostriction have previously been reported. Zr has been known to reduce the magnetostriction in other Fe alloys. The criteria for an ideal recording head pole material as well as shields for magnetroresistive sensors include high moment, low coercivity, high permeability, and zero magnetostriction. We present here the properties of half micrometer thick rf sputtered FeZrN films on glass coupons. The films were deposited at a pressure of 3 mTorr using a Perkin{endash}Elmer sputtering system. The target was composed of Fe with Zr chips covering approximately 2{percent} of the surface area. The properties were measured as a function of the N{sub 2} partial pressure. The saturation magnetization of the as-sputtered films was approximately 20 kG. The easy axis and the hard axis coercivities show minima at approximately 7{percent}{endash}10{percent} N{sub 2} partial pressure of approximately 1.8 and 0.6 G, respectively. The magnetic anisotropy is approximately 5 G yielding a dc permeability of approximately 4000 along the hard axis. X-ray data reveal a systematic change in the ratio of {alpha}-Fe and {gamma}-Fe{sub 4}N; the amount of the {gamma}-Fe{sub 4}N phase increases with increasing N{sub 2} flow rate. The magnetostriction increases with increasing N{sub 2} content crossing zero at approximately 6{percent}. The grain size as probed by atomic force microscopy is an increasing function of the N{sub 2} partial pressure, from a few nm for a N{sub 2} partial pressure of 5{percent} to as large as 50 nm for a N{sub 2} partial pressure of 15{percent}. {copyright} {ital 1996 American Institute of Physics.}
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.
Sunquake Generation by Coronal Magnetic Restructuring
NASA Astrophysics Data System (ADS)
Russell, A. J. B.; Mooney, M.; Leake, J. E.; Hudson, H. S.
2015-12-01
Solar flares and coronal mass ejections are powered by major restructurings of the coronal magnetic field, which appear to strongly perturb the magnetic field in the photosphere as well. Could the associated Lorentz forces generate sunquakes, as suggested by Hudson et al. 2008? Here, we present the first MHD simulations of sunquake generation by magnetic field perturbations, and explore the details of this mechanism. The downgoing magnetic field change is modelled as an Alfven wave, which propagates into the lower atmosphere. When it reaches the vicinity of the beta=1 layer (where the Alfven and sound speeds are equal), non-linear coupling excites a downgoing acoustic wave, which we interpret as a sunquake. The amplitude of the acoustic wave increases nonlinearly with the amplitude of the magnetic perturbation, reaching a limit where around 35% of the injected Poynting flux is transferred to the seismic wave - enough energy to match sunquake observations.
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.
Weak hybridization and isolated localized magnetic moments in the compounds CeT2Cd20 (T = Ni, Pd)
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
Weak hybridization and isolated localized magnetic moments in the compounds CeT₂Cd₂₀ (T = Ni, Pd).
White, B D; Yazici, D; Ho, P-C; Kanchanavatee, N; Pouse, N; Fang, Y; Breindel, A J; Friedman, A J; Maple, M B
2015-08-12
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. PMID:26189502
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.
Realizing a high magnetic moment in Gd/Cr/FeCo: The role of the rare earth
NASA Astrophysics Data System (ADS)
Ward, C.; Scheunert, G.; Hendren, W. R.; Hardeman, R.; Gubbins, M. A.; Bowman, R. M.
2013-03-01
The search for materials or systems exhibiting a high magnetic saturation has been of longstanding importance. It has been suggested that increased saturation could be achieved by coupling a transition metal via a spacer to a rare earth. We report Gd/Cr/Fe70Co30 multilayer stacks and find reduced yet modulating magnetic moment as a function of Cr thickness. Through a micro structural analysis, the lowered moment is indicated by the nucleation of the ultrathin Gd films into a face-centered cubic (fcc) phase. We discuss the possible solution in terms of quasi-perfect lattice match seed material to promote growth of hcp Gd.
NASA Astrophysics Data System (ADS)
N. Kawasaki; Oka, T.; Fukui, S.; Ogawa, J.; Sato, T.; Terasawa, T.; Itoh, Y.
A demagnetized Nd-Fe-B permanent magnet was scanned in the strong magnetic field space just above the magnetic pole containing a HTS bulk magnet which generates the magnetic field 3.4 T. The magnet sample was subsequently found to be fully magnetized in the open space of the static magnetic fields. The finite element method was carried out for the static field magnetization of a permanent magnet using a HTS bulk magnet. Previously, our research group experimentally demonstrated the possibility of full magnetization of rare earth permanent magnets with high-performance magnetic properties with use of the static field of HTS bulk magnets. In the present study, however, we succeeded for the first time in visualizing the behavior of the magnetizing field of the bulk magnet during the magnetization process and the shape of the magnetic field inside the body being magnetized. By applying this kind of numerical analysis to the magnetization for planned motor rotors which incorporate rare-earth permanent magnets, we hope to study the fully magnetized regions for the new magnetizing method using bulk magnets and to give motor designing a high degree of freedom.
Synthesis of high magnetic moment soft magnetic nanocomposite powders for RF filters and antennas
NASA Astrophysics Data System (ADS)
Chinnasamy, Chins; Malallah, Yaaqoub; Jasinski, Melania M.; Daryoush, Afshin S.
2015-04-01
Fe60Co40 alloy nanoparticles with an average particle size of 30 nm were successfully synthesized in gram scale batches using the modified polyol process. The X-ray diffraction and microstructure studies clearly show the formation of the alloy nanoparticles. The saturation magnetization for the gram scale synthesized Fe60Co40 alloy nanoparticles is in the range of 190-205 emu/g at room temperature. The as-synthesized nanoparticles were used to fabricate transmission lines on FR4 substrate to perform radio frequency (RF) characterization of the nanoparticles at ISM RF bands of interest (all in GHz range). The complex permeability extraction of composite Fe60Co40 nanoparticles were performed using perturbation technique applied to microstrip transmission lines by relative measurement of full two port scattering parameter with respect to a baseline FR4 substrate. The extracted results show attractive characteristics for small size antennas and filters.
Localized versus itinerant magnetic moments in Na0.7CoO2
NASA Astrophysics Data System (ADS)
Gavilano, J. L.; Pedrini, B.; Magishi, K.; Hinderer, J.; Weller, M.; Ott, H. R.; Kazakov, S. M.; Karpinski, J.
2006-08-01
Based on experimental Co59 -NMR data in the temperature range between 0.1 and 300K , we address the problem of the character of the Co 3d -electron based magnetism in Na0.7CoO2 . Temperature-dependent Co59 -NMR spectra reveal different Co environments below 300K and their differentiation increases with decreasing temperature. We show that the Na23 - and Co59 -NMR data may consistently be interpreted by assuming that below room temperature the Co 3d electrons are itinerant. We also argue that the Co59 -NMR response is inconsistent with well-defined local magnetic moments on the Co sites. We identify a substantial orbital contribution χorb to the d -electron susceptibility. At low temperatures χorb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T1-1(T) confirms significant variations in the dynamics of this electronic subsystem between 250 and 300K , as previously suggested. Below 100K , Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1K , but this scenario still leaves a number of open questions.
Channel-wing System for Thrust Deflection and Force/Moment Generation
NASA Technical Reports Server (NTRS)
Englar, Robert J. (Inventor); Bushnell, Dennis M. (Inventor)
2006-01-01
An aircraft comprising a Channel Wing having blown c h - ne1 circulation control wings (CCW) for various functions. The blown channel CCW includes a channel that has a rounded or near-round trailing edge. The channel further has a trailing-edge slot that is adjacent to the rounded trailing edge of the channel. The trailing-edge slot has an inlet connected to a source of pressurized air and is capable of tangentially discharging pressurized air over the rounded trailing edge. The aircraft further has a propeller that is located in the channel and ahead of the rounded trailing edge of the channel. The propeller provides a propeller thrust exhaust stream across the channel wing to propel the aircraft through the air and to provide high lift. The pressurized air being discharged over the rounded trailing edge provides a high lift that is obtained independent of an aircraft angle of attack, thus preventing the asymmetry. separated flow, and stall experienced by the CC wing at the high angle of attack it required for high lift generation. The aircraft can further include blown outboard circulation control wings (CCW) that are synergistically connected to the blown channel CCWs. The blown outboard CCWs provide additional high lift, control thrust/drag interchange, and can provide all three aerodynamic moments when differential blowing is applied front-to-rear or left-to-right. Both the blown channel CCW and the outboard CCW also have leading-edge blowing slots to prevent flow separation or to provide aerodynamic moments for control.
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.
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.
Hurd, Wendy J.; Kaufman, Kenton R.; Murthy, Naveen S.
2014-01-01
Background Medial elbow distraction during pitching as the primary mechanism contributing to adaptations in ulnar collateral ligament (UCL) appearance during magnetic resonance imaging (MRI) evaluation has not been established. Hypothesis Uninjured high school–aged pitchers with unilateral adaptations of the UCL exhibit a higher peak internal elbow adduction moment than those without UCL adaptations. Study Design Cohort study (Prevalence); Level of evidence, 2. Methods Twenty uninjured, asymptomatic high school–aged pitchers underwent bilateral elbow MRI examinations. Three-dimensional motion analysis testing was performed to collect throwing arm biomechanics as participants pitched from an indoor mound. Nonparametric tests were performed to compare peak internal elbow adduction moment in uninjured participants with and without adaptations in UCL appearance and to determine the nature of the relationship between the peak internal adduction moment and UCL appearance. Results Uninjured participants with UCL thickening exhibited a higher peak internal elbow adduction moment of 53.3 ± 6.8 N·m compared with uninjured participants without adaptations in UCL appearance, 38.8 ± 10.9 N·m (P = .05), as higher moments were correlated with ligament thickening (correlation coefficient, 0.45) (P = .02). Conclusion This study establishes the association between medial elbow distraction captured by the internal adduction moment during pitching and UCL adaptations visible during MRI evaluation. PMID:21335342
Aubin, C.; Orginos, K.; Pascalutsa, V.; Vanderhaeghen, M.
2009-03-01
We calculate the magnetic dipole moment of the {delta}(1232) and {omega}{sup -} 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}{sup -} is done at the physical strange quark mass, with the result in units of the physical nuclear magneton {mu}{sub {omega}{sup -}}=-1.93{+-}0.08{+-}0.12 (where the first error is statistical and the second is systematic) compared to the experimental number: -2.02{+-}0.05. The {delta} has been studied at three unphysical quark masses, corresponding to pion mass m{sub {pi}}=366, 438, and 548 MeV. The pion mass dependence is compared with the behavior obtained from chiral effective field theory.
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Silva, Antonio; Kim, Hyun-Chul
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/Nc 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: κTu=3.56 and κTd=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be κTs=0.2˜-0.2, that is compatible with zero. We also calculate the corresponding form factors κTq(Q2) up to a momentum transfer Q2≤1GeV2 at a renormalization scale of 0.36GeV2.
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.
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.
Magnetic Field Analysis of a Permanent-Magnet Induction Generator
NASA Astrophysics Data System (ADS)
Tsuda, Toshihiro; Fukami, Tadashi; Kanamaru, Yasunori; Miyamoto, Toshio
The permanent-magnet induction generator (PMIG) is a new type of induction machine that has a permanent-magnet rotor inside a squirrel-cage rotor. In this paper, a new technique for the magnetic field analysis of the PMIG is proposed. The proposed technique is based on the PMIG's equivalent circuit and the two-dimensional finite-element analysis (2D-FEA). To execute the 2D-FEA, the phasors of primary and secondary currents are calculated from the equivalent circuit, and the input data for the 2D-FEA is found by converting these phasors into the space vectors. As a result, the internal magnetic fields of the PMIG can be easily analyzed without complicated calculations.
CP-violating effect of the Th nuclear magnetic quadrupole moment: accurate many-body study of ThO.
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. PMID:25615324
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
Average magnetic moments of pre-yrast high spin states in {sup 166,165}Hf
Weissman, L.; Hass, M.; Broude, C.
1996-01-01
The average magnetic moments of high spin states in Hf isotopes were determined in a transient field measurement at the 14 MV Koffler accelerator of the Weizmann Institute. The reaction {sup 130}Te({sup 40}Ca,{ital xn}){sup 166,165}Hf at beam energies from 167 to 182.5 MeV was used to populate different high spin regions and provide the recoiling Hf nuclei with sufficient velocity to traverse the 2.9 mg/cm{sup 2} Gd ferromagnetic layer. Standard double ratios and angular distributions for various low level transitions were measured to determine precession angles. These carry information regarding the average {ital g} factor of unobservable transitions at medium excitation. To obtain a more quantitative analysis regarding the time-decay history of the {gamma} cascade, Monte Carlo simulations of the cascade were carried out. The significance of the results for understanding the single particle nature of these pre-yrast levels is discussed. {copyright} {ital 1996 The American Physical Society.}
Measuring the Nuclear Magnetic Octupole Moment of a Single Trapped Barium-137 Ion
NASA Astrophysics Data System (ADS)
Kleczewski, Adam; Fortson, Norval; Blinov, Boris
2009-05-01
Recent measurements of hyperfine structure in the cesium-133 atom resolved a nuclear magnetic octupole moment φ much larger than expected from the nuclear shell model[1]. To explore this issue further, we are undertaking an experiment to measure the hyperfine structure in the 5D manifold of a single trapped barium-137 ion which, together with reliable calculations in alkali-like Ba^+, should resolve φ with sensitivity better than the shell model value [2]. We use a TmHo:YLF laser tuned to 2051 nm and a fiber laser tuned to 1762 nm to drive the 6S1/2 to 5D3/2 and 6S1/2 to 5D5/2 electric quadrupole transitions. These lasers allow us to selectively populate any hyperfine sub-level in the 5D manifold. We will then perform RF spectroscopy on the 5D states to make a precision measurement of the hyperfine frequency intervals. We report on the development of the laser and RF spectroscopy systems. [1] V. Gerginov, A. Derevianko, and C. E. Tanner, Phys. Rev. Lett. 91, 072501 [2] K. Beloy, A. Derevianko, V. A. Dzuba, G. T. Howell, B. B. Blinov, E. N. Fortson, arXiv:0804.4317v1 [physics.atom-ph] 28 Apr 2008
Magnetic Moments of the 21+ and 41+ States in 110SN
NASA Astrophysics Data System (ADS)
Kumbartzki, Gerfried; Benczer-Koller, N.; Bernstein, L.; Torres, D. A.; Speidel, K.-H.; Allmond, J. M.; Fallon, P.; Abramovic, I.; Bevins, J. M.; Hurst, A.; Guevara, Z. E.; Gürdal, G.; Kirsch, L.; Laplace, T.; Lo, A.; Crawford, H. L.; Matthew, E.; Meyers, I.; Phair, L.; Ramirez, F.; Sharon, Y. Y.; Wiens, A.
2015-10-01
The structure of the Sn isotopes has been studied via measurements of B(E2;21+->01+) transition rates and g factors of 21+ states. Values of B(E2)'s in the lighter isotopes show an increase in collectivity below midshell, contrary to predictions from shell model calculations. In order to better establish the structure of these neutron-deficient isotopes, measurements of g factors in 110Sn, where the neutrons might occupy both the g7 / 2 and d5 / 2 orbitals, have been carried out. The states of interest were populated in the reaction 12C(106Cd, 2 α)110Sn, at the LBNL 88 inch cyclotron. The γ rays were detected in ORNL and LBNL clover detectors. The transient field technique was used to obtain magnetic moments. The details of the experiment and the results will be presented. The authors acknowledge support from the US NSF and DoE, the Colombia Colciencias and the German DFG.
Magnetic dipole moment measurements of picosecond states in even and odd heavy nuclei
Ballon, D.J.
1985-01-01
The perturbed angular correlation 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 /sup 150/Sm transversing gadolinium targets, the temperature dependence of the transient hyperfine field is deduced at /sup 150/Sm nuclei traveling at 2 < v/v/sub 0/ < 4. These are compared with similar measurements made using iron targets. Second, the deduced values of the g-factors of the 2/sub 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/sub 1/- and 5/2/sub 1/- states of /sup 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/sub 1/+ states of neighboring even-even nuclei.
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.
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.
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.
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.
Instrument Records Magnetic Fields Generated By Lightning
NASA Technical Reports Server (NTRS)
Medelius, Pedro J.; Simpson, Howard James
1995-01-01
Portable, self-contained, compact instrument measures and records transient magnetic fields particularly those generated by nearby lightning strikes. Designed to be placed near sensitive electronic equipment in anticipation of thunderstorms. Data recorded during thunderstorms analyzed afterward to determine whether magnetic effects of lightning strong enough to have damaged and/or affected operation of sensitive equipment. Provides data helping engineers decide whether sensitive equipment should be tested for damage and/or other effects caused by lightning. Typical installations in which instrument beneficial include outdoor sensing equipment, computer rooms, broadcasting stations, and powerplant control rooms.
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 #12;lms with a bulk magnetization of 1.95(5) {mu}{sub #22;}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.
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.
SEED BANKS FOR MAGNETIC FLUX COMPRESSION GENERATORS
Fulkerson, E S
2008-05-14
In recent years the Lawrence Livermore National Laboratory (LLNL) has been conducting experiments that require pulsed high currents to be delivered into inductive loads. The loads fall into two categories (1) pulsed high field magnets and (2) the input stage of Magnetic Flux Compression Generators (MFCG). Three capacitor banks of increasing energy storage and controls sophistication have been designed and constructed to drive these loads. One bank was developed for the magnet driving application (20kV {approx} 30kJ maximum stored energy.) Two banks where constructed as MFCG seed banks (12kV {approx} 43kJ and 26kV {approx} 450kJ). This paper will describe the design of each bank including switching, controls, circuit protection and safety.
NASA Astrophysics Data System (ADS)
Iwao, S.
1991-07-01
The quenching phenomena on the magnetic moments of odd A nuclei have been studied by assuming the shell model configuration of nucleons and SU_{2} quantum universal enveloping (QUE) algebra. In order to test a q deformation observed from this analysis is universal or not, we have analyzed the magnetic moments of odd-odd nuclei in the same approach, by taking the experimental data of relevant pair of odd A nuclei close in nature as inputs for the chosen odd-odd one. The additional and reasonable values of q deformation found there clearly indicate that the QUE-algebraic angular-momentum coupling rule is realized in nature at least for the composite system. It is pointed out that the Delta (1232) will contribute so as to smooth out the q to a common finite-ranged value of it.
Dru Renner, Xu Feng, Karl Jansen, Marcus Petschlies
2011-08-01
We present a reliable nonperturbative calculation of the QCD correction, at leading-order in the electromagnetic coupling, to the anomalous magnetic moment of the electron, muon and tau leptons using two-flavor lattice QCD. We use multiple lattice spacings, multiple volumes and a broad range of quark masses to control the continuum, infinite-volume and chiral limits. We examine the impact of the commonly ignored disconnected diagrams and introduce a modification to the previously used method that results in a well-controlled lattice calculation. We obtain 1.513 (43) 10^-12, 5.72 (16) 10^-8 and 2.650 (54) 10^-6 for the leading-order QCD correction to the anomalous magnetic moment of the electron, muon and tau respectively, each accurate to better than 3%.
Magnetic moment and lifetime measurements of Coulomb-excited states in Cd106
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
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.
Tenth-order electron anomalous magnetic moment: Contribution of diagrams without closed lepton loops
NASA Astrophysics Data System (ADS)
Aoyama, Tatsumi; Hayakawa, Masashi; Kinoshita, Toichiro; Nio, Makiko
2015-02-01
This paper presents a detailed account of the evaluation of the electron anomalous magnetic moment ae which arises from a gauge-invariant set, called Set V, consisting of 6354 tenth-order Feynman diagrams without closed lepton loops. The latest value of the sum of Set V diagrams evaluated by the Monte Carlo integration routine VEGAS is 8.726 (336 )(α /π )5 , which replaces the very preliminary value reported in 2012. Combining it with 6318 previously published tenth-order diagrams, we obtain 7.795 (336 )(α /π )5 as the complete mass-independent tenth-order term. Together with the improved value of the eighth-order term this leads to ae(theory)=1 159 652 181.643 (25 )(23 )(16 )(763 )×1 0-12 , where the first three uncertainties are from the eighth-order, tenth-order, and hadronic and elecroweak terms. The fourth and largest uncertainty is from α-1=137.035 999 049 (90 ) , the fine-structure constant derived from the rubidium recoil measurement. Thus, ae(experiment)-ae(theory)=-0.91 (0.82 )×1 0-12 . Assuming the validity of the standard model, we obtain the fine-structure constant α-1(ae)=137.035 999 1570 (29 )(27 )(18 )(331 ) , where uncertainties are from the eighth-order, tenth-order, and hadronic and electroweak terms, and the measurement of ae. This is the most precise value of α available at present and provides a stringent constraint on possible theories beyond the standard model.
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.
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.
Magnetic dipole moments of {sup 58}Cu and {sup 59}Cu by in-source laser spectroscopy
Stone, N. J.; Koester, U.; Stone, J. Rikovska; Fedorov, D. V.; Fedoseyev, V. N.; Flanagan, K. T.; Hass, M.; Lakshmi, S.
2008-06-15
Online measurements of the magnetic dipole moments and isotope shifts of {sup 58}Cu and {sup 59}Cu by the in-source laser spectroscopy method are reported. The results for the magnetic moments are {mu} ({sup 58}Cu) =+0.52(8) {mu}{sub N},{mu}({sup 59}Cu) =+1.84(3) {mu}{sub N} and for the isotope shifts {delta}{nu}{sup 59,65}=1.72(22) GHz and {delta}{nu}{sup 58,65}=1.99(30) GHz in the transition from the 3d{sup 10}4s {sup 2}S{sub 1/2} ground state to the 3d{sup 10}4p {sup 2}P{sub 1/2} state in Cu I. The magnetic moment of {sup 58}Cu is discussed in the context of the strength of the subshell closure at {sup 56}Ni, additivity rules and large-scale shell model calculations.
Ultrafast dynamics of localized magnetic moments in the unconventional Mott insulator Sr2IrO4.
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
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.
Forces and moments generated by the human arm: Variability and control
Xu, Y; Terekhov, AV; Latash, ML; Zatsiorsky, VM
2012-01-01
This is an exploratory study of the accurate endpoint force vector production by the human arm in isometric conditions. We formulated three common-sense hypotheses and falsified them in the experiment. The subjects (n=10) exerted static forces on the handle in eight directions in a horizontal plane for 25 seconds. The forces were of 4 magnitude levels (10 %, 20%, 30% and 40% of individual MVC). The torsion moment on the handle (grasp moment) was not specified in the instruction. The two force components and the grasp moment were recorded, and the shoulder, elbow, and wrist joint torques were computed. The following main facts were observed: (a) While the grasp moment was not prescribed by the instruction, it was always produced. The moment magnitude and direction depended on the instructed force magnitude and direction. (b) The within-trial angular variability of the exerted force vector (angular precision) did not depend on the target force magnitude (a small negative correlation was observed). (c) Across the target force directions, the variability of the exerted force magnitude and directional variability exhibited opposite trends: In the directions where the variability of force magnitude was maximal, the directional variability was minimal and vice versa. (d) The time profiles of joint torques in the trials were always positively correlated, even for the force directions where flexion torque was produced at one joint and extension torque was produced at the other joint. (e) The correlations between the grasp moment and the wrist torque were negative across the tasks and positive within the individual trials. (f) In static serial kinematic chains, the pattern of the joint torques distribution could not be explained by an optimization cost function additive with respect to the torques. Plans for several future experiments have been suggested. PMID:23080084
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.
Resistive Magnetic Field Generation at Cosmic Dawn
NASA Astrophysics Data System (ADS)
Miniati, Francesco; Bell, A. R.
2011-03-01
Relativistic charged particles (CRs for cosmic rays) produced by supernova explosion of the first generation of massive stars that are responsible for the reionization of the universe escape into the intergalactic medium, carrying an electric current. Charge imbalance and induction give rise to a return current, \\vec{j}_t, carried by the cold thermal plasma which tends to cancel the CR current. The electric field, \\vec{E}=η\\vec{j}_t, required to draw the collisional return current opposes the outflow of low-energy CRs and ohmically heats the cold plasma. Owing to inhomogeneities in the resistivity, η(T), caused by a structure in the temperature, T, of the intergalactic plasma, the electric field possesses a rotational component which sustains Faraday's induction. It is found that a magnetic field is robustly generated throughout intergalactic space at a rate of 10-17 to 10-16 G Gyr-1, until the temperature of the intergalactic medium is raised by cosmic reionization. The magnetic field may seed the subsequent growth of magnetic fields in the intergalactic environment. The role of CR-driven instabilities is discussed, and nonlinear effects are briefly considered.
A deep dynamo generating Mercury's magnetic field.
Christensen, Ulrich R
2006-12-21
Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned. PMID:17183319
Aubin, C.; Blum, T.
2007-06-01
We present a lattice calculation of the hadronic vacuum polarization and the lowest order hadronic contribution (HLO) to the muon anomalous magnetic moment, a{sub {mu}}=(g-2)/2, using 2+1 flavors of improved staggered fermions. A precise fit to the low-q{sup 2} region of the vacuum polarization is necessary to accurately extract the muon g-2. To obtain this fit, we use staggered chiral perturbation theory, including a model to incorporate the vector particles as resonances, and compare these to polynomial fits to the lattice data. We discuss the fit results and associated systematic uncertainties, paying particular attention to the relative contributions of the pions and vector mesons. Using a single lattice spacing ensemble generated by the MILC Collaboration (a=0.086 fm), light quark masses as small as roughly one-tenth the strange quark mass, and volumes as large as (3.4 fm){sup 3}, we find a{sub {mu}}{sup HLO}=(713{+-}15)x10{sup -10} and (748{+-}21)x10{sup -10} where the error is statistical only and the two values correspond to linear and quadratic extrapolations in the light quark mass, respectively. Considering various systematic uncertainties not eliminated in this study (including a model of vector resonances used to fit the lattice data and the omission of disconnected quark contractions in the vector-vector correlation function), we view this as agreement with the current best calculations using the experimental cross section for e{sup +}e{sup -} annihilation to hadrons (692.4{+-}5.9{+-}2.4)x10{sup -10}, and including the experimental decay rate of the tau lepton to hadrons (711.0{+-}5.0{+-}0.8{+-}2.8)x10{sup -10}. We discuss several ways to improve the current lattice calculation.
Generation of squeezing: magnetic dipoles on cantilevers
NASA Astrophysics Data System (ADS)
Seok, Hyojun; Singh, Swati; Steinke, Steven; Meystre, Pierre
2011-05-01
We investigate the generation of motional squeezed states in a nano-mechanical cantilever. Our model system consists of a nanoscale cantilever - whose center-of-mass motion is initially cooled to its quantum mechanical ground state - magnetically coupled a classically driven mechanical tuning fork. We show that the magnetic dipole-dipole interaction can produce significant phonon squeezing of the center-of-mass motion of the cantilever, and evaluate the effect of various dissipation channels, including the coupling of the cantilever to a heat bath and phase and amplitude fluctuations in the oscillating field driving the tuning fork. US National Science Foundation, the US Army Research Office, DARPA ORCHID program through a grant from AFOSR.
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.
Spin and orbital magnetic moments of Fe in the n-type ferromagnetic semiconductor (In,Fe)As
Kobayashi, M. Oshima, M.; Anh, L. D.; Hai, P. N.; Tanaka, M.; Takeda, Y.; Okane, T.; Saitoh, Y.; Yamagami, H.; Sakamoto, S.; Kadono, T.; Fujimori, A.; Harada, Y.
2014-07-21
The electronic and magnetic properties of Fe atoms in the ferromagnetic semiconductor (In,Fe)As codoped with Be have been studied by x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) at the Fe L{sub 2,3} edge. The XAS and XMCD spectra showed simple spectral line shapes similar to Fe metal, but the ratio of the orbital and spin magnetic moments (M{sub orb}/M{sub spin}) estimated using the XMCD sum rules was significantly larger than that of Fe metal, indicating a significant orbital moment of Fe 3d electrons in (In,Fe)As:Be. The positive value of M{sub orb}/M{sub spin} implies that the Fe 3d shell is more than half-filled, which arises from the hybridization of the Fe{sup 3+} (d{sup 5}) state with the charge-transfer d{sup 6}L{sub ¯} states, where L{sub ¯} is a ligand hole in the host valence band. The XMCD intensity as a function of magnetic field indicated hysteretic behavior of the superparamagnetic-like component due to discrete ferromagnetic domains.
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.
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.
Vortex flow generated by a magnetic stirrer
NASA Astrophysics Data System (ADS)
Halász, Gábor; Gyüre, Balázs; Jánosi, Imre M.; Szabó, K. Gábor; Tél, Tamás
2007-12-01
We investigate the flow generated by a magnetic stirrer in cylindrical containers by optical observations, particle image velocimetry measurements, and particle and dye tracking methods. The tangential flow is that of an ideal vortex outside a core, but inside downwelling occurs with a strong jet in the very middle. In the core region dye patterns remain visible over minutes indicating inefficient mixing in this region. The results of quantitative measurements can be described by simple relations that depend on the stirring bar's rotation frequency. The tangential flow is similar to that of large atmospheric vortices such as dust devils and tornadoes.
3.5 keV X-ray line signal from decay of right-handed neutrino due to transition magnetic moment
NASA Astrophysics Data System (ADS)
Modak, Kamakshya Prasad
2015-03-01
We consider the dark matter model with radiative neutrino mass generation where the Standard Model is extended with three right-handed singlet neutrinos ( N 1, N 2 and N 3) and one additional SU(2) L doublet scalar η. One of the right-handed neutrinos ( N 1), being lightest among them, is a leptophilic fermionic dark matter candidate whose stability is ensured by the imposed symmetry on this model. The second lightest right-handed neutrino ( N 2) is assumed to be nearly degenerated in mass with the lightest one enhancing the co-annihilation between them. The effective interaction term among the lightest, second lightest right-handed neutrinos and photon containing transition magnetic moment is responsible for the decay of heavier right-handed neutrino to the lightest one and a photon ( N 2 → N 1 + γ). This radiative decay of heavier right-handed neutrino with charged scalar and leptons in internal lines could explain the X-ray line signal ˜ 3 .5 keV recently claimed by XMM-Newton X-ray observatory from different galaxy clusters and Andromeda galaxy (M31). The value of the transition magnetic moment is computed and found to be several orders of magnitude below the current reach of various direct dark matter searches. The other parameter space in this framework in the light of the observed signal is further investigated.
NASA Astrophysics Data System (ADS)
Machavariani, A. I.; Faessler, Amand
2011-03-01
Our previous paper (Machavariani and Faessler 2010 J. Phys. G: Nucl. Part. Phys. 37 075004) is generalized within the field-theoretical formulation with the quark-gluon degrees of freedom (Huang and Weldon 1975 Phys. Rev. D11 257; Haag 1958 Phys. Rev. 112 669; Nishijima 1958 Phys. Rev. 111 995; Zimmermann 1958 Nuovo Cimento 10 598), where pions and nucleons are treated as the bound (cluster) systems of quarks. It is shown that current conservation for the on-shell πN bremsstrahlung amplitude with the composite nucleons and pions has the same form as in the usual quantum field theory (Itzykson and Zuber 1980 Quantum Field Theory (New York: McGraw-Hill); Bjorken and Drell 1965 Relativistic Quantum Fields (New York: McGraw-Hill)) without quark-gluon degrees of freedom (Machavariani and Faessler 2010). The model-independent representation of the Δ - γ'Δ vertex through the π - γ'π', N - γ'N', Δ - πN vertices remain the same in the quantum field theory with the quark-gluon degrees of freedom. Correspondingly, the magnetic dipole moments of the Δ+ and Δ++ resonances in the field-theoretical formulations with and without quark-gluons are identical. These results are extended for the magnetic dipole moments of the Δo and Δ- resonances which are determined via the anomalous magnetic moment of the neutron μn as \\mu _{\\Delta ^o}={ {M_{\\Delta }}\\over {m_p}} \\mu _n and \\mu _{\\Delta ^{-}}={3\\over 2}\\mu _{\\Delta ^o}.
Experimental evidence of Cr magnetic moments at low temperature in Cr2A(A=Al, Ge)C.
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
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.
Jafri, Sadaf Fatima; Koumousi, Evangelia S; Sainctavit, Philippe; Juhin, Amélie; Schuler, Vivien; Bun U, Oana; Mitcov, Dmitri; Dechambenoit, Pierre; Mathonière, Corine; Clérac, Rodolphe; Otero, Edwige; Ohresser, Philippe; Cartier Dit Moulin, Christophe; Arrio, Marie-Anne
2016-07-18
Photomagnetism in three-dimensional Co/Fe Prussian blue analogues is a complex phenomenon, whose detailed mechanism is not yet fully understood. Recently, researchers have been able to prepare molecular fragments of these networks using a building block synthetic approach from mononuclear precursors. The main objective in this strategy is to isolate the smallest units that show an intramolecular electron transfer to have a better understanding of the electronic processes. A prior requirement to the development of this kind of system is to understand to what extent electronic and magnetic properties are inherited from the corresponding precursors. In this work, we investigate the electronic and magnetic properties of the FeTp precursor (N(C4H9)4)[TpFe(III)(CN)3], (Tp being tris-pyrazolyl borate) of a recently reported binuclear cyanido-bridged Fe/Co complex. X-ray absorption spectroscopy and X-ray magnetic circular dichroism measurements at the Fe L2,3 edges (2p → 3d) supported by ligand field multiplet calculations have allowed to determine the spin and orbit magnetic moments. Inaccuracy of the spin sum rule in the case of low-spin Fe(III) ion was demonstrated. An exceptionally large value of the orbital magnetic moment is found (0.9 μB at T = 2 K and B = 6.5 T) that is likely to play an important role in the magnetic and photomagnetic properties of molecular Fe/Co Prussian blue analogues. PMID:27385292
Atomic moments in Mn_{2}CoAl thin films analyzed by X-ray magnetic circular dichroism
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 Mn_{2}CoAl 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.
Primordial magnetic field generated in natural inflation
NASA Astrophysics Data System (ADS)
AlMuhammad, Anwar S.; Lopez-Mobilia, Rafael
2015-11-01
We study the simple gauge invariant model {f^2}FF as a way to generate primordial magnetic fields (PMF) in natural inflation (NI). We compute both magnetic and electric spectra generated by the {f^2}FF model in NI for different values of model parameters and find that both de Sitter and power law expansion lead to the same results at sufficiently large number of e-foldings. We also find that the necessary scale invariance property of the PMF cannot be obtained in NI in first order of slow roll limits under the constraint of inflationary potential, V( 0 ) ˜eq 0. Furthermore, if this constraint is relaxed to achieve scale invariance, then the model suffers from the backreaction problem for the co-moving wave number, k ≲ 8.0× 10^{-7} {Mpc^{-1}} and Hubble parameter, H_i ≳ 1.25× 10^{-3} {M_{Pl}}. The former can be considered as a lower bound of k and the later as an upper bound of H_i for a model which is free from the backreaction problem. Further, we show that there is a narrow range of the height of the potential Λ around {Λ _{min}} ≈ 0.00874{M_{{Pl}}} and of k around {k_{min}} ˜ 0.0173{Mp}{{c}^{ - 1}}, at which the energy of the electric field can fall below the energy of the magnetic field. The range of k lies within some observable scales. However, the relatively short range of k presents a challenge to the viability of this model.
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.
Out-of-Plane Magnetic Moment and Lattice Distortion in Sputtered Ge Added Fe3O4 Thin Film.
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
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) v_{μ}e 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} μ_{B}. 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.
Loya-Mancilla, Sagrario M; Poddar, Pankaj; Das, Raja; Ponce, Hilda E Esparza; Templeton-Olivares, Ivan L; Solis-Canto, Oscar O; Ornelas-Gutierrez, Carlos E; Espinosa-Magaña, Francisco; Olive-Méndez, Sion F
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
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
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
Sharma, Neetika; Dahiya, Harleen; Chatley, P. K.; Gupta, Manmohan
2010-04-01
Magnetic moments of the low lying and charmed spin (1/2){sup +} and spin (3/2){sup +} baryons have been calculated in the SU(4) chiral constituent quark model ({chi}CQM) by including the contribution from cc fluctuations. Explicit calculations have been carried out for the contribution coming from the valence quarks, ''quark sea'' polarizations and their orbital angular momentum. The implications of such a model have also been studied for magnetic moments of the low lying spin (3/2){sup +{yields}}(1/2){sup +} and (1/2){sup +{yields}}(1/2){sup +} transitions as well as the transitions involving charmed baryons. The predictions of {chi}CQM not only give a satisfactory fit for the baryons where experimental data is available but also show improvement over the other models. In particular, for the case of {mu}(p), {mu}({Sigma}{sup +}), {mu}({Xi}{sup 0}), {mu}({Lambda}), Coleman-Glashow sum rule for the low lying spin (1/2){sup +} baryons and {mu}({Delta}{sup +}), {mu}({Omega}{sup -}) for the low lying spin (3/2){sup +} baryons, we are able to achieve an excellent agreement with data. For the spin (1/2){sup +} and spin (3/2){sup +} charmed baryon magnetic moments, our results are consistent with the predictions of the QCD sum rules, light cone sum rules and spectral sum rules. For the cases where light quarks dominate in the valence structure, the sea and orbital contributions are found to be fairly significant however, they cancel in the right direction to give the correct magnitude of the total magnetic moment. On the other hand, when there is an excess of heavy quarks, the contribution of the quark sea is almost negligible, for example, {mu}({Omega}{sub c}{sup 0}), {mu}({Lambda}{sub c}{sup +}), {mu}({Xi}{sub c}{sup +}), {mu}({Xi}{sub c}{sup 0}), {mu}({Omega}{sub cc}{sup +}), {mu}({Omega}{sup -}), {mu}({Omega}{sub c}*{sup 0}), {mu}({Omega}{sub cc}*{sup +}), and {mu}({Omega}{sub ccc}*{sup ++}). The effects of configuration mixing and quark masses have also been
Fluorescent lamp with static magnetic field generating means
Moskowitz, Philip E.; Maya, Jakob
1987-01-01
A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed.
Fluorescent lamp with static magnetic field generating means
Moskowitz, P.E.; Maya, J.
1987-09-08
A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed. 2 figs.
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.
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.
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
Physics of heat generation using magnetic nanoparticles for hyperthermia.
Dennis, Cindi L; Ivkov, Robert
2013-12-01
Magnetic nanoparticle hyperthermia and thermal ablation have been actively studied experimentally and theoretically. In this review, we provide a summary of the literature describing the properties of nanometer-scale magnetic materials suspended in biocompatible fluids and their interactions with external magnetic fields. Summarised are the properties and mechanisms understood to be responsible for magnetic heating, and the models developed to understand the behaviour of single-domain magnets exposed to alternating magnetic fields. Linear response theory and its assumptions have provided a useful beginning point; however, its limitations are apparent when nanoparticle heating is measured over a wide range of magnetic fields. Well-developed models (e.g. for magnetisation reversal mechanisms and pseudo-single domain formation) available from other fields of research are explored. Some of the methods described include effects of moment relaxation, anisotropy, nanoparticle and moment rotation mechanisms, interactions and collective behaviour, which have been experimentally identified to be important. Here, we will discuss the implicit assumptions underlying these analytical models and their relevance to experiments. Numerical simulations will be discussed as an alternative to these simple analytical models, including their applicability to experimental data. Finally, guidelines for the design of optimal magnetic nanoparticles will be presented. PMID:24131317
Relativistic generation of vortex and magnetic field
Mahajan, S. M.; Yoshida, Z.
2011-05-15
The implications of the recently demonstrated relativistic mechanism for generating generalized vorticity in purely ideal dynamics [Mahajan and Yoshida, Phys. Rev. Lett. 105, 095005 (2010)] are worked out. The said mechanism has its origin in the space-time distortion caused by the demands of special relativity; these distortions break the topological constraint (conservation of generalized helicity) forbidding the emergence of magnetic field (a generalized vorticity) in an ideal nonrelativistic dynamics. After delineating the steps in the ''evolution'' of vortex dynamics, as the physical system goes from a nonrelativistic to a relativistically fast and hot plasma, a simple theory is developed to disentangle the two distinct components comprising the generalized vorticity--the magnetic field and the thermal-kinetic vorticity. The ''strength'' of the new universal mechanism is, then, estimated for a few representative cases; in particular, the level of seed fields, created in the cosmic setting of the early hot universe filled with relativistic particle-antiparticle pairs (up to the end of the electron-positron era), are computed. Possible applications of the mechanism in intense laser produced plasmas are also explored. It is suggested that highly relativistic laser plasma could provide a laboratory for testing the essence of the relativistic drive.
Change in the magnetic moment of a ferromagnetic nanoparticle under polarized current
NASA Astrophysics Data System (ADS)
Kozhushner, M. A.; Gatin, A. K.; Grishin, M. V.; Shub, B. R.; Kim, V. P.; Khomutov, G. B.; Trakhtenberg, L. I.
2016-02-01
The magnetization reversal of a ferromagnetic Fe3O4 nanoparticle with a volume of the order of several thousands of cubic nanometers under the influence of spin-polarized current has been investigated on a high-vacuum scanning tunneling microscope, where one of the electrodes is a magnetized iron wire needle and the second electrode is a ferromagnetic nanoparticle on a graphite substrate. The measured threshold current of magnetization reversal, i.e., the lowest value of the current corresponding to the magnetization reversal, is found to be I thresh ≈ 9 nA. A change in the magnetization of a nanoparticle is revealed using the giant magnetoresistance effect, i.e., the dependence of the weak polarized current ( I < I thresh) on the relative orientation of the magnetizations of the electrodes.
Can basal magma oceans generate magnetic fields?
NASA Astrophysics Data System (ADS)
Stegman, D. R.; Ziegler, L. B.; Davies, C.
2015-12-01
Earth's magnetic field is very old, with recent data now showing the field possibly extended back to 4.1 billion years ago (Tarduno et al., Science, 2015). Yet, based upon our current knowledge there are difficulties in sustained a core dynamo over most of Earth's history. Moreover, recent estimates of thermal and electrical conductivity of liquid iron at core conditions from mineral physics experiments indicate that adiabatic heat flux is approximately 15 TW, nearly 3 times larger than previously thought, exacerbating difficulties for driving a core dynamo by convective core cooling alone throughout Earth history. A long-lived basal magma ocean in the lowermost mantle has been proposed to exist in the early Earth, surviving perhaps into the Archean. While the modern, solid lower mantle is an electromagnetic insulator, electrical conductivities of silicate melts are known to be higher, though as yet they are unconstrained for lowermost mantle conditions. Here we explore the geomagnetic consequences of a basal magma ocean layer for a range of possible electrical conductivities. For the highest electrical conductivities considered, we find a basal magma ocean could be a primary dynamo source region. This would suggest the proposed three magnetic eras observed in paleomagnetic data originate from distinct sources for dynamo generation: from 4.5-2.45 Ga within a basal magma ocean, from 2.25-0.4 Ga within a superadiabatically cooled liquid core, and from 0.4-present within a quasi-adiabatic core that includes a solidifying inner core. We have extended this work by developing a new code, Dynamantle, which is a model with an entropy-based approach, similar to those commonly used in core dynamics models. We present new results using this code to assess the conditions under which basal magma oceans can generate positive ohmic dissipation. This is more generally useful than just considering the early Earth, but also for many silicate exoplanets in which basal magma oceans
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.
Wong, H. T.; Li, H. B.; Lee, F. S.; Wu, S. C.; Chen, C. P.; Chou, M. H.; Jon, G. C.; Lai, W. P.; Lee, S. C.; Lin, F. K.; Lin, S. K.; Lin, S. T.; Chang, H. M.; Liao, H. Y.; Singh, V.; Chang, C. Y.; Deniz, M.; Fang, J. M.; Su, R. F.; Hu, C. H.
2007-01-01
A search of neutrino magnetic moments was carried out at the Kuo-Sheng nuclear power station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1 kg{sup -1} keV{sup -1} day{sup -1} near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding, and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron antineutrino flux of 6.4x10{sup 12} cm{sup -2} s{sup -1}, the limit on the neutrino magnetic moments of {mu}{sub {nu}{sub e}}<7.4x10{sup -11}{mu}{sub B} at 90% confidence level was derived. Indirect bounds on the {nu}{sub e} radiative decay lifetimes were inferred.
Increased magnetic moment induced by lattice expansion from α-Fe to α′-Fe{sub 8}N
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.
NASA Astrophysics Data System (ADS)
Wong, H. T.; Li, H. B.; Lin, S. T.; Lee, F. S.; Singh, V.; Wu, S. C.; Chang, C. Y.; Chang, H. M.; Chen, C. P.; Chou, M. H.; Deniz, M.; Fang, J. M.; Hu, C. H.; Huang, H. X.; Jon, G. C.; Kuo, W. S.; Lai, W. P.; Lee, S. C.; Li, J.; Liao, H. Y.; Lin, F. K.; Lin, S. K.; Lu, J. Q.; Sheng, H. Y.; Su, R. F.; Tong, W. S.; Xin, B.; Yeh, T. R.; Yue, Q.; Zhou, Z. Y.; Zhuang, B. A.
2007-01-01
A search of neutrino magnetic moments was carried out at the Kuo-Sheng nuclear power station at a distance of 28 m from the 2.9 GW reactor core. With a high purity germanium detector of mass 1.06 kg surrounded by scintillating NaI(Tl) and CsI(Tl) crystals as anti-Compton detectors, a detection threshold of 5 keV and a background level of 1kg-1keV-1day-1 near threshold were achieved. Details of the reactor neutrino source, experimental hardware, background understanding, and analysis methods are presented. Based on 570.7 and 127.8 days of Reactor ON and OFF data, respectively, at an average Reactor ON electron antineutrino flux of 6.4×1012cm-2s-1, the limit on the neutrino magnetic moments of μν¯e<7.4×10-11μB at 90% confidence level was derived. Indirect bounds on the ν¯e radiative decay lifetimes were inferred.
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
Optical generation of intense ultrashort magnetic pulses at the nanoscale
NASA Astrophysics Data System (ADS)
Tsiatmas, Anagnostis; Atmatzakis, Evangelos; Papasimakis, Nikitas; Fedotov, Vassili; Luk'yanchuk, Boris; Zheludev, Nikolay I.; García de Abajo, F. Javier
2013-11-01
Generating, controlling and sensing strong magnetic fields at ever shorter time and length scales is important for both fundamental solid-state physics and technological applications such as magnetic data recording. Here, we propose a scheme for producing strong ultrashort magnetic pulses localized at the nanoscale. We show that a bimetallic nanoring illuminated by femtosecond laser pulses responds with transient thermoelectric currents of picosecond duration, which in turn induce Tesla-scale magnetic fields in the ring cavity. Our method provides a practical way of generating intense nanoscale magnetic fields with great potential for materials characterization, terahertz radiation generation and data storage applications.
Second-harmonic generation with magnetic-field controllability.
Ju, Sheng; Cai, Tian-Yi; Wei, Chi-I; Guo, Guang-Yu
2009-12-15
Based on density functional theory with the generalized gradient approximation plus on-site Coulomb repulsion method, we study the magnetic-ordering dependence of second-harmonic generation (SHG) in a polar magnet BiCoO(3). The large second-order optical susceptibility, which can reach 3.7x10(-7) esu, exhibits a strong magnetic-ordering dependence, giving rise to magnetic-field controllable SHG response in polar magnets. PMID:20016638
Evidence for Local Moment Magnetism in Superconducting Bi2Sr2CaCu2O8+δ
NASA Astrophysics Data System (ADS)
Tranquada, John; Xu, G. Y.; Gu, G. D.; Huecker, M.; Fauque, B.; Perring, T. G.; Stock, C.; Regnault, L.-P.
2009-03-01
We have used inelastic neutron scattering to measure the dynamic spin susceptibility in optimally-doped Bi2Sr2CaCu2O8+δ (Tc = 91 K). Four crystals with a total mass of 19 g were measured on the MAPS spectrometer at ISIS for temperatures of 10 K and 100 K. We have been able to identify the magnetic excitations in the energy range 20-90 meV. The magnetic nature of the scattering has been confirmed with spin-polarization analysis on IN22 at the ILL. While we see temperature-dependent changes for energies around 40 meV that are consistent with earlier studies, we find that the Q-integrated signal shows a much weaker variation with temperature. The absolute magnetic cross section is quite comparable to that of spin fluctuations in stripe ordered La1.875Ba0.125CuO4. As the magnetism in the latter system has been shown to have a dominant contribution from local moments [1], we argue that the same must be true for Bi2Sr2CaCu2O8+δ. [1] M. Huecker et al., Phys. Rev. B (accepted); cond-mat/0503417v3.
The magnetic moment enigma in Fe-based high temperature superconductors.
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
The magnetic moment enigma in Fe-based high temperature superconductors
NASA Astrophysics Data System (ADS)
Mannella, Norman
2014-11-01
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, BaFe2As2 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.
Origin of Perpendicular Magnetic Anisotropy and Large Orbital Moment in Fe Atoms on MgO.
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. PMID:26684139
Klempt, E.; Schulze, R.; Wolf, H.; Camani, M.; Gygax, F.N.; Rueegg, W.; Schenck, A.; Schilling, H.
1982-02-01
A new determination of the magnetic moment of the positive muon in units of the magnetic moment of the proton is presented. The Larmor precession of positive muons in liquid bromine was observed by a stroboscopic technique in a field of 0.75 T and combined with concomitant proton NMR measurements in the same chemical environment. The stroboscopic method allows use of the full muon stopping rate available at the Schweizerisches Institut fuer Nuklearforschung (SIN) muon channel. Moreover, it permits an intrinsically precise determination of muon Larmor frequency and proton NMR frequency measuring the magnetic field by comparison with the stable reference frequency of the SIN accelerator (..delta cap omega../..cap omega..roughly-equal10/sup -8/). Two different bromine targets were used which allowed an unambiguous determination of the chemical field shift experienced by the muons. One target contained pure and water-free liquid bromine (Br/sub 2/), where stopped muons form (..mu../sup +/e/sup -/)Br molecules. The other target was slightly contaminated with water; there a chemical reaction chain places the muons into (..mu../sup +/e/sup -/)HO molecules. The diamagnetic shielding of protons in the analogous molecules HBr and H/sub 2/O in liquid bromine was measured by high-resolution NMR. Values for the isotopic shift of the diamagnetic shielding, when protons are replaced by muons, are available from quantum chemical calculations. After application of the chemical-shift corrections, the results from the two different bromine targets are consistent. The final result is ..mu../sub ..mu..//..mu../sub p/ = 3.183 344 1(17) (or +- 0.53 ppm). This value agrees with other recent precision determinations of ..mu../sub ..mu..//..mu../sub p/. For the muon mass the present result implies m/sub ..mu..//m/sub e/ = 206.768 35(11) ( +- 0.53 ppm).
NASA Astrophysics Data System (ADS)
Nakamura, H.; Hayashi, N.; Nakai, N.; Okumura, M.; Machida, M.
2009-10-01
In order to resolve a discrepancy of the magnetic moment on Fe between the experimental and calculation results, we perform first-principle electronic structure calculations for iron-based superconductors LaFeAsO1-x and LiFeAs also show similar SDW. So far, the first-principle calculations on LaFeAsO actually predicted the SDW state as a ground state. However, the predicted magnetic moment (∼2 μB) per an Fe atom is much larger than the observed one (∼0.35 μB) in experiments [2,4]. The authors suggested that the discrepancy can be resolved by expanding U into a negative U range within LSDA + U framework. In this paper, we revisit the discrepancy and clarify why the negative correction is essential in these compounds. See Ref. [5] for the details of calculation data by LSDA + negative U. In the first-principle calculation on compounds including transition metals, the total energy is frequently corrected by “LSDA + U” approach. The parameter U is theoretically re-expressed as U(≡U-J), where U is the on-site Coulomb repulsion (Hubbard U) and J is the atomic-orbital intra-exchange energy (Hund’s coupling parameter) [6]. The parameter U employed in the electronic structure calculations is usually positive. The positivity promotes the localized character of d-electrons and enhances the magnetic moment in the cases of magnetically ordered compounds. Normally, this positive correction successfully works. In choosing the parameter, one can principally extend the parameter U range to a negative region. The negative case [7] is not popular, but it can occur in the following two cases [8]: (i) the Hubbard U becomes negative and (ii) the intra-exchange J is effectively larger than the Hubbard U. The case (i) has been suggested by many authors based on various theoretical considerations. Here, we note that U should be estimated once screening effects on the long-range Coulomb interaction are taken into account. In fact, small U has been reported [9]. Thus, when the
A study of nanosized magnesium ferrite particles with high magnetic moment
NASA Astrophysics Data System (ADS)
Sumangala, T. P.; Mahender, C.; Venkataramani, N.; Prasad, Shiva
2015-05-01
Nano-sized magnesium ferrite particles were prepared by sol gel combustion synthesis and were either furnace cooled or quenched after calcining at various temperatures ranging from 300 to 800 °C. A magnetisation value of 61 emu/g was obtained at 5 K for sample calcined at 800 °C and quenched in liquid nitrogen temperature. This is one of the highest reported values of magnetisation obtained from quenching at such a lower temperature. An estimate of the number of Fe3+ ions on A and B sites was made after applying Néel Model on the magnetisation values measured at 5 K. It was estimated that Fe3+ ions segregates out from both sites disproportionately so as to cause a net decrease in the overall moment. The resultant cation distribution is found to be consistent with the coercivity data.
Origin of lowered magnetic moments in epitaxially strained thin films of multiferroic Bi2FeCrO6
NASA Astrophysics Data System (ADS)
Rout, Paresh C.; Putatunda, Aditya; Srinivasan, Varadharajan
2016-03-01
We have investigated the effect of epitaxial strain on the magnetic properties and B -site cation ordering in multiferroic Bi2FeCrO6 (001) thin films using a density-functional theory approach. We find that in thin films with rock-salt ordering of Fe and Cr the ground state is characterized by C-type antiferromagnetic (AFM) order. This is in contrast to the bulk form of the material, which was predicted to be a ferrimagnet with G-type AFM order. Furthermore, the cation-ordered thin films undergo a transition with epitaxial strain from C- to A-type AFM order. Other magnetic orders appear as thermally accessible excited states. We also find that B -site cation-disordered structures are more stable in coherent epitaxial strains, thereby explaining the lowered magnetic moments observed in these samples at room temperature. Strain varies both the sign and strength of the Fe-Cr superexchange coupling, resulting in a very interesting phase diagram for Bi2FeCrO6 thin films.
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.
Magnetic field generation in the cores of terrestrial bodies
NASA Technical Reports Server (NTRS)
Runcorn, S. K.
1985-01-01
Efforts to find some scaling law for the dipole moments of planets seem illusory for, although dynamo theory is still in a rudimentary state, once the critical magnetic Reynolds Number is exceeded it appears that the field strength is determined by the energy source, it it is permissible to treat the core as a heat engine. For this reason the lunar magnetic field is of special significance as the paleomagnetic evidence strongly suggests that the surface field was about 1 G 3.9 by diminishing exponentially to about .02 G 3.2 by ago and completely disappearing some time later.
NASA Astrophysics Data System (ADS)
Iwakami, O.; Namisashi, Y.; Abe, S.; Matsumoto, K.; Ano, G.; Akatsu, M.; Mitsumoto, K.; Nemoto, Y.; Takeda, N.; Goto, T.; Kitazawa, H.
2014-09-01
Complex ac susceptibility, χ =χ'-iχ'', measurements of the clathrate compound Pr3Pd20Ge6 were performed in static fields up to 10 mT for H ∥[001] and at temperatures down to 500 μK. Praseodymium (Pr) nuclear magnetic moments at the 8c site, where quadrupole moments of 4f electrons order at TQ1=250 mK, were found to order antiferromagnetically at 9 mK, as shown by a peak in χ' and a substantial increase in thermal relaxation time. The large enhancement factor (1+K8c) obtained by calculation of the hyperfine-enhanced nuclear susceptibility of Pr at the 8c site accounts for the high transition temperature of Pr nuclear magnetic moments and the large χ' below 30 mK. From analysis of the crystalline electric field and the mean-field approximation, we conclude that a χ peak at 77 mK can be ascribed to an antiferromagnetic ordering of magnetic moments of 4f electrons at the 4a site. We found that nuclear and f-electron moments order separately on two sublattices in this compound. The temperature and magnetic field dependence of χ' and χ'' between 30 and 60 mK are discussed in terms of dissipation phenomena.
NASA Astrophysics Data System (ADS)
Khalilov, V. R.
The scattering of a nonrelativistic neutral massive fermion having the anomalous magnetic moment (AMM) in an electric field of a uniformly charged long conducting thread aligned perpendicularly to the fermion motion is considered to study the so-called Aharonov-Casher (AC) effect by taking into account the particle spin. For this solution, the nonrelativistic Dirac-Pauli equation for a neutral massive fermion with AMM in (3+1) dimensions is found, which takes into account explicitly the particle spin and interaction between AMM of moving fermion and the electric field. Expressions for the scattering amplitude and the cross-section are obtained for spin-polarized massive neutral fermion scattered off the above conducting thread. We conclude that the scattering amplitude and cross-section of spin-polarized massive neutral fermions are influenced by the interaction of AMM of moving neutral fermions with the electric field as well as by the polarization of fermion beam in the initial state.
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.
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.
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.
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.
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 CeT_{2}Cd_{20} (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.
Second generation measurement of the electric dipole moment of the electron using trapped ThF+ ions
NASA Astrophysics Data System (ADS)
Ng, Kia Boon; Zhou, Yan; Gresh, Daniel; Cairncross, William; Grau, Matthew; Ni, Yiqi; Ye, Jun; Cornell, Eric
2016-05-01
ThF+ has been chosen as the candidate for a second generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF+ eEDM experiment, ThF+ has several advantages: (i) the eEDM-sensitive state (3Δ1) is the ground state, which facilitates a long coherence time; (ii) its effective electric field (38 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state-selective photoionization via core-nonpenetrating Rydberg states. Here, we present progress of our experimental setup, preliminary spectroscopic data of multi-photon ionization, and discussions of new features in ion trapping, state preparation and population readout.
Improved Magnetic Field Generation Efficiency and Higher Temperature Spheromak Plasmas
Wood, R D; Hill, D N; McLean, H S; Hooper, E B; Hudson, B F; Moller, J M; Romero-Talamas, C A
2008-09-15
New understanding of the mechanisms governing the observed magnetic field generation limits on the sustained spheromak physics experiment has been obtained. Extending the duration of magnetic helicity injection during the formation of a spheromak and optimizing the ratio of injected current to bias flux produce higher magnetic field plasmas with record spheromak electron temperatures. To explore magnetic field buildup efficiency limits, the confinement region geometry was varied resulting in improved field buildup efficiencies.
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.
Muon anomalous magnetic moment and positron excess at AMS-02 in a gauged horizontal symmetric model
NASA Astrophysics Data System (ADS)
Tomar, Gaurav; Mohanty, Subhendra
2014-11-01
We studied an extension of the standard model with a fourth generation of fermions to explain the discrepancy in the muon ( g -2) and explain the positron excess seen in the AMS-02 experiment. We introduce a gauged SU(2)HV horizontal symmetry between the muon and the 4th generation lepton families. The 4th generation right-handed neutrino is identified as the dark matter with mass ~ 700GeV. The dark matter annihilates only to ( μ + μ -) and ( ν {/μ C } ν μ ) states via SU(2)HV gauge boson. The SU(2)HV gauge boson with mass ~ 1.4 TeV gives an adequate contribution to the ( g - 2) of muon and fulfill the experimental constraint from BNL measurement. The higgs production constraints from 4th generation fermions is evaded by extending the higgs sector.
A permanent-magnet generator for wind power applications
Soederlund, L.; Eriksson, J.T.; Salonen, J.; Vihriaelae, H.; Peraelae, R.
1996-07-01
In order to achieve a gearless construction of the wind energy conversion system (WECS) a low-speed, i.e., multipole, generator is required. This paper examines an axial-field permanent-magnet synchronous wind power generator (PMWG) mainly from the magnetic viewpoint. Both mechanical and electromagnetic designs are described as well as some primary test results concerning the model generators having nominal power of 5 and 10 kW.
An upper limit on the anomalous magnetic moment of the lepton
NASA Astrophysics Data System (ADS)
OPAL Collaboration; Ackerstaff, K.; Alexander, G.; Allison, J.; Altekamp, N.; Anderson, K. J.; Anderson, S.; Arcelli, S.; Asai, S.; Ashby, S. F.; Axen, D.; Azuelos, G.; Ball, A. H.; Barberio, E.; Barlow, R. J.; Bartoldus, R.; Batley, J. R.; Baumann, S.; Bechtluft, J.; Behnke, T.; Bell, K. W.; Bella, G.; Bentvelsen, S.; Bethke, S.; Betts, S.; Biebel, O.; Biguzzi, A.; Bird, S. D.; Blobel, V.; Bloodworth, I. J.; Bobinski, M.; Bock, P.; Bonacorsi, D.; Boutemeur, M.; Braibant, S.; Brigliadori, L.; Brown, R. M.; Burckhart, H. J.; Burgard, C.; Bürgin, R.; Capiluppi, P.; Carnegie, R. K.; Carter, A. A.; Carter, J. R.; Chang, C. Y.; Charlton, D. G.; Chrisman, D.; Clarke, P. E. L.; Cohen, I.; Conboy, J. E.; Cooke, O. C.; Couyoumtzelis, C.; Coxe, R. L.; Cuffiani, M.; Dado, S.; Dallapiccola, C.; Dallavalle, G. M.; Davis, R.; de Jong, S.; del Pozo, L. A.; de Roeck, A.; Desch, K.; Dienes, B.; Dixit, M. S.; Doucet, M.; Duchovni, E.; Duckeck, G.; Duerdoth, I. P.; Eatough, D.; Estabrooks, P. G.; Etzion, E.; Evans, H. G.; Evans, M.; Fabbri, F.; Fanfani, A.; Fanti, M.; Faust, A. A.; Feld, L.; Fiedler, F.; Fierro, M.; Fischer, H. M.; Fleck, I.; Folman, R.; Fong, D. G.; Foucher, M.; Fürtjes, A.; Futyan, D. I.; Gagnon, P.; Gary, J. W.; Gascon, J.; Gascon-Shotkin, S. M.; Geddes, N. I.; Geich-Gimbel, C.; Geralis, T.; Giacomelli, G.; Giacomelli, P.; Giacomelli, R.; Gibson, V.; Gibson, W. R.; Gingrich, D. M.; Glenzinski, D.; Goldberg, J.; Goodrick, M. J.; Gorn, W.; Grandi, C.; Gross, E.; Grunhaus, J.; Gruwé, M.; Hajdu, C.; Hanson, G. G.; Hansroul, M.; Hapke, M.; Hargrove, C. K.; Hart, P. A.; Hartmann, C.; Hauschild, M.; Hawkes, C. M.; Hawkings, R.; Hemingway, R. J.; Herndon, M.; Herten, G.; Heuer, R. D.; Hildreth, M. D.; Hill, J. C.; Hillier, S. J.; Hobson, P. R.; Hocker, A.; Homer, R. J.; Honma, A. K.; Horváth, D.; Hossain, K. R.; Howard, R.; Hüntemeyer, P.; Hutchcroft, D. E.; Igo-Kemenes, P.; Imrie, D. C.; Ishii, K.; Jawahery, A.; Jeffreys, P. W.; Jeremie, H.; Jimack, M.; Joly, A.; Jones, C. R.; Jones, M.; Jost, U.; Jovanovic, P.; Junk, T. R.; Kanzaki, J.; Karlen, D.; Kartvelishvili, V.; Kawagoe, K.; Kawamoto, T.; Kayal, P. I.; Keeler, R. K.; Kellogg, R. G.; Kennedy, B. W.; Kirk, J.; Klier, A.; Kluth, S.; Kobayashi, T.; Kobel, M.; Koetke, D. S.; Kokott, T. P.; Kolrep, M.; Komamiya, S.; Kowalewski, R. V.; Kress, T.; Krieger, P.; von Krogh, J.; Kyberd, P.; Lafferty, G. D.; Lahmann, R.; Lai, W. P.; Lanske, D.; Lauber, J.; Lautenschlager, S. R.; Lawson, I.; Layter, J. G.; Lazic, D.; Lee, A. M.; Lefebvre, E.; Lellouch, D.; Letts, J.; Levinson, L.; List, B.; Lloyd, S. L.; Loebinger, F. K.; Long, G. D.; Losty, M. J.; Ludwig, J.; Lui, D.; Macchiolo, A.; MacPherson, A.; Mannelli, M.; Marcellini, S.; Markopoulos, C.; Markus, C.; Martin, A. J.; Martin, J. P.; Martinez, G.; Mashimo, T.; Mättig, P.; McDonald, W. J.; McKenna, J.; McKigney, E. A.; McMahon, T. J.; McPherson, R. A.; Meijers, F.; Menke, S.; Merritt, F. S.; Mes, H.; Meyer, J.; Michelini, A.; Mihara, S.; Mikenberg, G.; Miller, D. J.; Mincer, A.; Mir, R.; Mohr, W.; Montanari, A.; Mori, T.; Mihara, S.; Nagai, K.; Nakamura, I.; Neal, H. A.; Nellen, B.; Nisius, R.; O'Neale, S. W.; Oakham, F. G.; Odorici, F.; Ogren, H. O.; Oh, A.; Oldershaw, N. J.; Oreglia, M. J.; Orito, S.; Pálinkás, J.; Pásztor, G.; Pater, J. R.; Patrick, G. N.; Patt, J.; Perez-Ochoa, R.; Petzold, S.; Pfeifenschneider, P.; Pilcher, J. E.; Pinfold, J.; Plane, D. E.; Poffenberger, P.; Poli, B.; Posthaus, A.; Rembser, C.; Robertson, S.; Robins, S. A.; Rodning, N.; Roney, J. M.; Rooke, A.; Rossi, A. M.; Routenburg, P.; Rozen, Y.; Runge, K.; Runolfsson, O.; Ruppel, U.; Rust, D. R.; Sachs, K.; Saeki, T.; Sahr, O.; Sang, W. M.; Sarkisyan, E. K. G.; Sbarra, C.; Schaile, A. D.; Schaile, O.; Scharf, F.; Scharff-Hansen, P.; Schieck, J.; Schleper, P.; Schmitt, B.; Schmitt, S.; Schöning, A.; Schröder, M.; Schumacher, M.; Schwick, C.; Scott, W. G.; Shears, T. G.; Shen, B. C.; Shepherd-Themistocleous, C. H.; Sherwood, P.; Sieberg, R. P. B.; Siroli, G. P.; Sittler, A.; Skillman, A.; Skuja, A.; Smith, A. M.; Snow, G. A.; Sobie, R.; Söldner-Rembold, S.; Springer, R. W.; Sproston, M.; Stephens, K.; Steuerer, J.; Stockhausen, B.; Stoll, K.; Strom, D.; Ströhmer, R.; Szymanski, P.; Tafirout, R.; Talbot, S. D.; Taras, P.; Tarem, S.; Teuscher, R.; Thiergen, M.; Thomson, M. A.; von Törne, E.; Torrence, E.; Towers, S.; Trigger, I.; Trócsányi, Z.; Tsur, E.; Turcot, A. S.; Turner-Watson, M. F.; Ueda, I.; Utzat, P.; van Kooten, R.; Vannerem, P.; Verzocchi, M.; Vikas, P.; Vokurka, E. H.; Voss, H.; Wäckerle, F.; Wagner, A.; Ward, C. P.; Ward, D. R.; Watkins, P. M.; Watson, A. T.; Watson, N. K.; Wells, P. S.; Wermes, N.; White, J. S.; Wilson, G. W.; Wilson, J. A.; Wyatt, T. R.; Yamashita, S.; Yekutieli, G.; Zacek, V.; Zer-Zion, D.
1998-07-01
Using radiative events collected with the OPAL detector at LEP at during 1990-95, a direct study of the electromagnetic current at the vertex has been performed in terms of the anomalous magnetic form factor of the lepton. The analysis is based on a data sample of 1429 events which are examined for a deviation from the expectation with . From the non-observation of anomalous production a limit ofis obtained. This can also be interpreted as a limit on the electric dipole form factor asThe above ranges are valid at the confidence level.
Microwave power generation by magnetic superlattices
NASA Astrophysics Data System (ADS)
Littlejohn, S.; Nogaret, A.; Davies, S. R.; Henini, M.; Beere, H. E.; Ritchie, D. A.
2011-12-01
We report on microwave power emission by ballistic electrons as they cross a region of spatially inhomogeneous magnetic field. Magnetic finger gates were fabricated at the surface of high mobility GaAs/AlGaAs Hall bars embedded in a coplanar waveguide. By modulating the current injected through the Hall bar and measuring the second harmonic of the signal rectified by a Schottky detector, we obtain the microwave power emitted by the superlattice. This power (˜6 W m-2) is compared to the fluorescence of electron spins that undergo spin resonance as they cross domains of opposite magnetic field.
Dynamical mass generation in QED with weak magnetic fields
Ayala, A.; Rojas, E.; Bashir, A.; Raya, A.
2006-09-25
We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2.
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
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
Magnetic field generated by shielding current in high Tc superconducting coils for NMR magnets
NASA Astrophysics Data System (ADS)
Amemiya, Naoyuki; Akachi, Ken
2008-09-01
Numerical electromagnetic field analyses of high Tc superconducting tape in coils were carried out to calculate the magnetic field generated by the shielding (magnetization) current in superconducting tape. The numerical model employs the power law electric field-current density characteristic and the thin strip approximation, in which the current component normal to the wide face of the tape is neglected. The shielding (magnetization) currents lead to non-uniform current distributions in the superconducting tape in the coils. The magnetic field generated by the shielding (magnetization) current can deteriorate the field quality and could be a concern in insert coils for NMR magnets using high Tc superconducting tape.
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
Force generation by orthodontic samarium-cobalt magnets.
von Fraunhofer, J A; Bonds, P W; Johnson, B E
1992-01-01
The use of samarium-cobalt (Sm-Co) magnets for light force application is a relatively new concept in orthodontic tooth movement. This study reports on the forces generated by these magnets. Magnets were attached to aluminum rods mounted in a universal testing machine. The magnets were initially separated by 10 mm were moved toward each other at 2.5mm/min in repulsion or attraction, depending upon the magnetic pole orientation. The magnets were also positioned initially in contact and then moved apart at a rate of 2.5mm/min, again producing repulsion or attraction, depending upon the pole orientation. The Sm-Co magnets exhibit very large forces when in close approximation but forces decrease markedly at separations greater than 2mm. The force, P, generated between magnets is determined by their separation, d, and follows the relationship P = dn. At magnet separations of 0 to 2mm, the exponent n is equal to -0.4; at separations of 2mm to 7mm, exponent n equals -2.1 for both attraction and repulsion. Thus the classic Coulomb law of magnetic force was followed only at magnet separations of greater than 2mm. Force-separation behavior and the high cost of these magnets may not justify their routine clinical use. PMID:1416238
NASA Technical Reports Server (NTRS)
Carpenter, Michele; Jackson, Kimberly; Cohanim, Babak; Duda, Kevin R.; Rize, Jared; Dopart, Celena; Hoffman, Jeffrey; Curiel, Pedro; Studak, Joseph; Ponica, Dina; RochlisZumbado, Jennifer
2013-01-01
Looking ahead to the human exploration of Mars, NASA is planning for exploration of near-Earth asteroids and the Martian moons. Performing tasks near the surface of such low-gravity objects will likely require the use of an updated version of the Manned Maneuvering Unit (MMU) since the surface gravity is not high enough to allow astronauts to walk, or have sufficient resistance to counter reaction forces and torques during movements. The extravehicular activity (EVA) Jetpack device currently under development is based on the Simplified Aid for EVA Rescue (SAFER) unit and has maneuvering capabilities to assist EVA astronauts with their tasks. This maneuvering unit has gas thrusters for attitude control and translation. When EVA astronauts are performing tasks that require ne motor control such as sample collection and equipment placement, the current control system will re thrusters to compensate for the resulting changes in center-of-mass location and moments of inertia, adversely affecting task performance. The proposed design of a next-generation maneuvering and stability system incorporates control concepts optimized to support astronaut tasks and adds control-moment gyroscopes (CMGs) to the current Jetpack system. This design aims to reduce fuel consumption, as well as improve task performance for astronauts by providing a sti er work platform. The high-level control architecture for an EVA maneuvering system using both thrusters and CMGs considers an initial assessment of tasks to be performed by an astronaut and an evaluation of the corresponding human-system dynamics. For a scenario in which the astronaut orbits an asteroid, simulation results from the current EVA maneuvering system are compared to those from a simulation of the same system augmented with CMGs, demonstrating that the forces and torques on an astronaut can be significantly reduced with the new control system actuation while conserving onboard fuel.
NASA Astrophysics Data System (ADS)
Ryu, Kwon-sang; Son, Derac; Park, Duck-gun; Kim, Yong-il
2010-05-01
Magnetic phases and defects are partly produced in steam generator tubes by stress and heat, because steam generator tubes in nuclear power plants are used under high temperature, high pressure, and radioactivity. The magnetic phases induce an error in the detection of the defects in steam generator tubes by the conventional eddy current method. So a new method is needed for detecting the magnetic phases in the steam generator tubes. We designed a new U-type yoke which has two kinds of coils and simulated the signal by the magnetic phases and defects in the Inconnel 600 tube.
Svirskii, M.S.
1985-09-10
Oscillations with a period equal to the normal or superconducting flux quantum occur in the current density and the orbital parts of the energy and the magnetic moment in cyclic systems. Transitions between these regimes can be induced by changing the number of electrons or by switching between states with different energies.
Computer Generated Snapshot of Our Sun's Magnetic Field
NASA Technical Reports Server (NTRS)
2003-01-01
These banana-shaped loops are part of a computer-generated snapshot of our sun's magnetic field. The solar magnetic-field lines loop through the sun's corona, break through the sun's surface, and cornect regions of magnetic activity, such as sunspots. This image --part of a magnetic-field study of the sun by NASA's Allen Gary -- shows the outer portion (skins) of interconnecting systems of hot (2 million degrees Kelvin) coronal loops within and between two active magnetic regions on opposite sides of the sun's equator. The diameter of these coronal loops at their foot points is approximately the same size as the Earth's radius (about 6,000 kilometers).
Highly Stable and Finely Tuned Magnetic Fields Generated by Permanent Magnet Assemblies
NASA Astrophysics Data System (ADS)
Danieli, E.; Perlo, J.; Blümich, B.; Casanova, F.
2013-05-01
Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays.
Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.
Danieli, E; Perlo, J; Blümich, B; Casanova, F
2013-05-01
Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays. PMID:23683185
Disc explosive magnetic generator of small class size
NASA Astrophysics Data System (ADS)
Grinevich, B. E.; Duday, P. V.; Ivanovsky, A. V.; Klimushkin, K. N.; Kraev, A. I.; Kudel'kin, V. B.; Mamyshev, V. I.; Mattsev, Yu. I.; Skobelev, A. N.; Shapovalov, E. V.
2015-01-01
This paper discusses one type of power generators—a disk explosive generator with flat disk elements and metal inserts. A technique of numerical simulation of the operation of this generator is proposed. The principle of operation and the design of the disk explosive magnetic generator are described. The results of calculations and experiments are presented.
Solvents level dipole moments.
Liang, Wenkel; Li, Xiaosong; Dalton, Larry R; Robinson, Bruce H; Eichinger, Bruce E
2011-11-01
The dipole moments of highly polar molecules measured in solution are usually smaller than the molecular dipole moments that are calculated with reaction field methods, whereas vacuum values are routinely calculated in good agreement with available vapor phase data. Whether from Onsager's theory (or variations thereof) or from quantum mechanical methods, the calculated molecular dipoles in solution are found to be larger than those measured. The reason, of course, is that experiments measure the net dipole moment of solute together with the polarized (perturbed) solvent "cloud" surrounding it. Here we show that the reaction field charges that are generated in the quantum mechanical self-consistent reaction field (SCRF) method give a good estimate of the net dipole moment of the solute molecule together with the moment arising from the reaction field charges. This net dipole is a better description of experimental data than the vacuum dipole moment and certainly better than the bare dipole moment of the polarized solute molecule. PMID:21923185
Generation and amplification of magnetic fields in the early Universe
NASA Astrophysics Data System (ADS)
Stone, James M.
A very brief review is given of processes that may be responsible for the generation of initial seed magnetic fields in the early Universe, and that can amplify those fields to the levels observed in galaxies in the current epoch.
Precise numerical estimation of the magnetic field generated around recombination
NASA Astrophysics Data System (ADS)
Fidler, Christian; Pettinari, Guido; Pitrou, Cyril
2016-05-01
We investigate the generation of magnetic fields from nonlinear effects around recombination. As tight-coupling is gradually lost when approaching z ≃1100 , the velocity difference between photons and baryons starts to increase, leading to an increasing Compton drag of the photons on the electrons. The protons are then forced to follow the electrons due to the electric field created by the charge displacement; the same field, following Maxwell's laws, eventually induces a magnetic field on cosmological scales. Since scalar perturbations do not generate any magnetic field as they are curl-free, one has to resort to second-order perturbation theory to compute the magnetic field generated by this effect. We reinvestigate this problem numerically using the powerful second-order Boltzmann code SONG. We show that: (i) all previous studies do not have a high enough angular resolution to reach a precise and consistent estimation of the magnetic field spectrum; (ii) the magnetic field is generated up to z ≃10 ; (iii) it is in practice impossible to compute the magnetic field with a Boltzmann code for scales smaller than 1 Mpc. Finally we confirm that for scales of a few Mpc, this magnetic field is of order 2 ×10-29 G , many orders of magnitude smaller than what is currently observed on intergalactic scales.
NASA Astrophysics Data System (ADS)
Vemuru, Krishnamurthy; Rosenberg, Richard; Mankey, Gary
Nanostructured FeCo thin films are interesting for magnetic recording applications due to their high saturation magnetization, high Curie temperature and low magnetocrystalline anisotropy. It is desirable to know how the magnetism is modified by the nanostructrure. We report Fe L 2 , 3 edge and Co L2 , 3 edge x-ray magnetic circular dichroism (XMCD) investigations of element specific spin and orbital magnetism of Fe and Co in two multilayer samples: (S1) Si/SiO2/[Co 0.8 nm/Fe 1.6 nm]x32/W (2nm) and (S2) Si/SiO2/[Co 1.6 nm/Fe 0.8 nm]x32/W (2nm) thin films at room temperature. Sum rule analysis of XMCD at Fe L2 , 3 edge in sample S1 shows that the orbital moment of Fe is strongly enhanced and the spin moment is strongly reduced as compared to the values found in bulk Fe. Details of sum rule analysis will be presented to compare and contrast spin magnetic moments and orbital magnetic moments of Fe and Co in the two multilayer samples. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Magnetic Second-Harmonic Generation from Interfaces and Nanostructures
NASA Astrophysics Data System (ADS)
McGilp, J. F.
2012-08-01
Magneto-optic techniques provide non-contact and non-destructive characterization of magnetic materials. This includes embedded magnetic nanostructures, which are accessible due to the large penetration depth of optical radiation. Nonlinear magnetic second-harmonic generation (MSHG) can measure the surface and interlace magnetism of centrosymmetric magnetic films and nanostructures with sub-monolayer sensitivity. MSHG is briefly reviewed and examples from high symmetry interlaces and nanostructures described. Low symmetry systems, such as aligned magnetic nanostructures grown by self-organization on vicinal substrates, are more difficult to characterize, however, because of the large number of tensor components that may contribute to the signal. Normal incidence geometry simplifies the problem and this new approach is shown to allow the determination of hysteresis loops and the temperature dependent magnetic response of Au-capped Fe nanostructures grown on vicinal W(110).
Performance Evaluation of a Permanent-Magnet Induction Generator
NASA Astrophysics Data System (ADS)
Fukami, Tadashi; Yokoi, Masahiro; Kanamaru, Yasunori; Miyamoto, Toshio
A permanent-magnet induction generator (PMIG) is a special induction machine self-excited from the inside of the squirrel-cage rotor by a permanent-magnet rotor (PM rotor). In order to evaluate the practical value of the PMIG, its steady-state performance is analyzed theoretically and experimentally. As a result, it was found that the PMIG exhibits good power factor and efficiency compared to a general-purpose induction generator (GPIG) of the same size.
38. VIEW OF COTTRELL MAGNETIC IMPULSE GENERATOR ADJACENT TO SIX ...
38. VIEW OF COTTRELL MAGNETIC IMPULSE GENERATOR ADJACENT TO SIX GAP ROTARY RECTIFIER. THIS UNIT GENERATED A MAGNETIC PULSE WHICH WAS TRANSMITTED TO THE COLLECTION PLATES IN THE ELECTROSTATIC PRECIPITATOR CHAMBER. THESE PERIODIC PULSES VIBRATE THE PLATES AND CAUSE PRECIPITATED ARTICLES OF SMOKE AND FLY ASH TO FALL TO THE BOTTOM OF THE PRECIPITATOR CHAMBER. - New York, New Haven & Hartford Railroad, Cos Cob Power Plant, Sound Shore Drive, Greenwich, Fairfield County, CT
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
Magnetic field generated resistivity maximum in graphite
NASA Technical Reports Server (NTRS)
Wollam, J. A.; Kreps, L. W.; Rojeski, M.; Vold, T.; Devaty, R.
1976-01-01
In zero magnetic field, B, the electrical resistivity, rho(O,T) of highly oriented pyrolytic (polycrystalline) graphite drops smoothly with decreasing T, becoming constant below 4 K. However, in a fixed applied magnetic field B, the resistivity rho(B,T) goes through a maximum as a function of T, with larger maximum for larger B. The temperature of the maximum increases with B, but saturates to a constant value near 25 K (exact T depends on sample) at high B. In single crystal graphite a maximum in rho(B,T) as a function of T is also present, but has the effects of Landau level quantization superimposed. Several possible explanations for the rho(B,T) maximum are proposed, but a complete explanation awaits detailed calculations involving the energy band structure of graphite, and the particular scattering mechanisms involved.
Magnetic Field Generation in Galactic Plasmas
NASA Astrophysics Data System (ADS)
Opher, Merav; Cowley, Steve; Maron, Jason; McWilliams, James
2000-10-01
The origin of the magnetic field in the universe is one of the great problems in astrophysics. The observed magnetic fields in spiral galaxies, for example, are of the order of microgauss and are coherent over galactic scales. It is usually assumed that turbulent fluid motions will enhance a seed field. In the present work we investigate the growth of the magnetic field in plasmas with high magnetic Prandtl number (the ratio of viscosity to resistivity). This growth occurs initially at scales below the viscous scale [1]. Kinney et al. [2] showed that in 2D the field saturates at an amplitude independent of the mean scale of the field. We discuss the initial growth in the three dimensional case where the dynamics of the field are on scales less than the viscosity scale [3]. At low initial field, the field grows and the scale decreases until the resistive scale is reached. The field then grows at a reduced rate until it reaches an equilibrium with the mean scale at a resistive scale. At higher initial amplitude, the field saturates before the mean scale has decreased to the resistive scale. The subsequent evolution is a slow decrease of the scale to the resistive scale, at which point it reaches equilibrium and stops evolving. To explain the large scale coherence of galactic fields, an inverse cascade is necessary. There is no evidence of an inverse cascade. We will present results for extended physics models including tensor viscosity and ambipular diffusion. [1] R. Kulsrud, and S. Anderson, Astrophys. J., 396, 606 (1992); A. Gruzinov, S. Cowley, and R. Sudan, Phys.Rev.Lett., 77, 4342 (1996). [2] R. M. Kinney, B. Chandran, S. Cowley, J. C. McWilliams, Astrophys. J., accepted to publication (2000). [3] M. Opher, S. Cowley, R. M. Kinney, B. Chandran, J. Maron and J.C. McWilliams, in preparation (2000).
Magnetic Field Generation in Galactic Plasmas
NASA Astrophysics Data System (ADS)
Opher, M.; Cowley, S.; Schekochihin, A.; Kinney, R. M.; Chandran, B.; Maron, J.; McWilliams, J. C.
2001-05-01
The origin of the magnetic field in the universe is one of the great problems in astrophysics. The observed magnetic fields in spiral galaxies, for example, are of the order of microgauss and are coherent over galactic scales. Its is usually assumed that turbulent fluid motions will enhance a seed field. In the present work we invetigate the growth of the magnetic field in plasmas with high magnetic Prandtl number (the ratio of viscosity to resistivity). This growth occur initially at scales below the viscous scale [1]. Kinney et al. [2] showed that in 2D the field saturates at an amplitude independent of the mean scale of the field. We discuss the initial growth in the three dimensional case where the dynamics of the field on scales less than the viscosity scale [3]. At low initial field, the field grows and the scale decreases until the resistive scale is reached. The field then grows at a reduced rate until it reaches an equilibrium with the mean scale at a resistive scale. At higher initial amplitude, the field saturates before the mean scale has decreased to the resistive scale. The subsequent evolution is a slow decrease of the scale to the resistive scale, at which point it reaches equilibrium and stops evolving. To explain the large scale coherence of galactic fields, an inverse cascade is necessary. There is no evidence of an inverse cascade. We will present results for extended physics models including tensor viscosity and ambipular diffusion. [1] R. Kulsrud, and S. Anderson, Astrophys. J., 396, 606 (1992); A. Gruzinov, S. Cowley, and R. Sudan, Phys.Rev.Lett., 77, 4342 (1996). [2] R. M. Kinney, B. Chandran, S. Cowley, J. C. McWilliams, Astrophys. J., accepted to publication (2000). [3] M. Opher, S. Cowley, A. Schekochihin, R. M. Kinney, B. Chandran, J. Maron and J.C. McWilliams, in preparation (2001).
NASA Astrophysics Data System (ADS)
Goyhenex, C.; Tréglia, G.; Legrand, B.
2016-04-01
Most of tight-binding studies of transition metal based systems deviating from perfect bulk (surfaces, nanoparticles, alloys) are based on local charge neutrality rules per site, per valence orbital and per element. Unfortunately, such rules do not hold per spin when interested in magnetic elements. We present here a simple way to characterize the variation of the magnetic moment with the environment and to generalize the tight-binding expression of the energy to account for magnetism. This is illustrated in the particular case of cobalt, going from perfect pure bulk to surface, nanoparticles and then CoPt alloy.
NASA Technical Reports Server (NTRS)
Kuhn, Richard E.
1997-01-01
When a jet STOVL aircraft is in STOL operation the jets impinge on the ground and generate wall jets flowing radially outward from the points at which the jets impinge. When the forward flowing part of a wall jet meets the free stream flow it is rolled back on itself forming a parabolic shaped ground vortex. Positive pressures are induced on the lower surface of the configuration ahead of the ground vortex and suction pressures are induced over the ground vortex itself. In addition, the suction pressures induced aft of the jet out of ground effect are reduced and lifting pressures are induced on the upper surface. This study analyzes available pressure and force data and develops a method for estimating the forces and moments induced in ground effect. The method includes the effects of configuration variables, height and operating conditions, as well as the effects of the location, deflection and shape of the jet. However, it is limited to single jets at subcritical nozzle pressure ratios. An analysis of the effects of moving over the ground vs. tests over a fixed ground plane is included.
NASA Astrophysics Data System (ADS)
Agashe, K.; Deshpande, N. G.; Wu, G.-H.
2001-06-01
We investigate whether models with flat extra dimensions in which SM fields propagate can give a significant contribution to the anomalous magnetic moment of the muon (MMM). In models with only SM gauge and Higgs fields in the bulk, the contribution to the MMM from Kaluza-Klein (KK) excitations of gauge bosons is very small. This is due to the constraint on the size of the extra dimensions from tree-level effects of KK excitations of gauge bosons on precision electroweak observables such as Fermi constant. If the quarks and leptons are also allowed to propagate in the (same) bulk (``universal'' extra dimensions), then there are no contributions to precision electroweak observables at tree-level. However, in this case, the constraint from one-loop contribution of KK excitations of (mainly) the top quark to /T parameter again implies that the contribution to the MMM is small. We show that in models with leptons, electroweak gauge and Higgs fields propagating in the (same) bulk, but with quarks and gluon propagating in a sub-space of this bulk, both the above constraints can be relaxed. However, with only one Higgs doublet, the constraint from the process /b-->sγ requires the contribution to the MMM to be smaller than the SM electroweak correction. This constraint can be relaxed in models with more than one Higgs doublet.
Transcranial magnetic stimulation-induced 'visual echoes' are generated in early visual cortex.
Jolij, Jacob; Lamme, Victor A F
2010-11-01
Transcranial magnetic stimulation (TMS) of the early visual areas can trigger perception of a flash of light, a so-called phosphene. Here we show that a very brief presentation of a stimulus can modulate features of a subsequent TMS-induced phosphene, to a level that participants mistake phosphenes for real stimuli, inducing 'visual echoes' of a previously seen stimulus. These 'echoes' are modulated by visual context at the moment of magnetic stimulation, showing that they are generated in early visual areas, and that the brain processes these 'echoes' as if they are factually presented stimuli. This shows that TMS can re-activate weak visual representations in early visual areas. Based on the pattern of contextual modulation of visual echoes, we theorize that perception of these echoes is not a passive reactivation of residual activity in early visual cortex, but an active interpretation of the combined activity of TMS-induced neural noise and cortical state. PMID:20732388
Fluorescent lamp unit with magnetic field generating means
Grossman, M.W.; George, W.A.
1989-08-08
A fluorescent lamp unit having a magnetic field generating means for improving the performance of the fluorescent lamp is disclosed. In a preferred embodiment the fluorescent lamp comprises four longitudinally extending leg portions disposed in substantially quadrangular columnar array and joined by three generally U-shaped portions disposed in different planes. In another embodiment of the invention the magnetic field generating means comprises a plurality of permanent magnets secured together to form a single columnar structure disposed within a centrally located region defined by the shape of lamp envelope. 4 figs.
Fluorescent lamp unit with magnetic field generating means
Grossman, Mark W.; George, William A.
1989-01-01
A fluorescent lamp unit having a magnetic field generating means for improving the performance of the fluorescent lamp is disclosed. In a preferred embodiment the fluorescent lamp comprises four longitudinally extending leg portions disposed in substantially quadrangular columnar array and joined by three generally U-shaped portions disposed in different planes. In another embodiment of the invention the magnetic field generating means comprises a plurality of permanent magnets secured together to form a single columnar structure disposed within a centrally located region defined by the shape of lamp envelope.
Passive magnetic bearing for a motor-generator
Post, Richard F.
2006-07-18
Conductive lap windings are interleaved with conventional loops in the stator of a motor-generator. The rotor provides magnetic induction lines that, when rotated, cut across the lap windings and the loops. When the rotor is laterally displaced from its equilibrium axis of rotation, its magnetic lines of induction induce a current in the interleaved lap windings. The induced current interacts with the magnetic lines of induction of the rotor in accordance with Lenz's law to generate a radial force that returns the rotor to its equilibrium axis of rotation.
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…
Linear moving magnet motor/generator for Stirling engines
NASA Astrophysics Data System (ADS)
Shtrikman, S.; Urieli, I.
Free piston Stirling cycle machines have many inherent advantages, however suffer from the difficulties of extracting power output and controllability of the free displacer, which is usually driven by gas pressure forces. Modern rare earth samarium cobalt magnets allow the use of moving magnet linear electrical devices. This paper discusses the development and testing of moving magnet devices designed specifically for use with Stirling engines, both for generating electricity and for driving the displacer piston. The generator was used as an output stage of a free piston Stirling engine, and is capable of delivering a power of 500 watts at an estimated efficiency of about 90%. The motor was used to drive the displacer of the same Stirling engine. It was found to be completely controllable in amplitude, phase, and mean position. The relative merits of moving magnet linear motor/generators are discussed.
Effects of non-linearities on magnetic field generation
Nalson, Ellie; Malik, Karim A.; Christopherson, Adam J. E-mail: achristopherson@gmail.com
2014-09-01
Magnetic fields are present on all scales in the Universe. While we understand the processes which amplify the fields fairly well, we do not have a ''natural'' mechanism to generate the small initial seed fields. By using fully relativistic cosmological perturbation theory and going beyond the usual confines of linear theory we show analytically how magnetic fields are generated. This is the first analytical calculation of the magnetic field at second order, using gauge-invariant cosmological perturbation theory, and including all the source terms. To this end, we have rederived the full set of governing equations independently. Our results suggest that magnetic fields of the order of 10{sup -30}- 10{sup -27} G can be generated (although this depends on the small scale cut-off of the integral), which is largely in agreement with previous results that relied upon numerical calculations. These fields are likely too small to act as the primordial seed fields for dynamo mechanisms.
Microwave generation for magnetic fusion energy applications
Antonsen, T.M. Jr.; Destler, W.W.; Granatstein, V.L.; Levush, B.
1992-01-01
This progress report encompasses work on two separate projects, both related to developing sources for electron cyclotron resonance heating of magnetic fusion plasmas. The report is therefore divided into two parts as follows: Free electron laser with small period wigglers; and theory and modeling of high frequency, high power gryotron operation. Task A is experimental and eventually aims at developing continuously tunable, cw sources for ECRH with power per unit as high as 5 megawatts. Task B provides gryotron theory and modeling in support of the gryotron development programs at MIT and Varian.
NASA Astrophysics Data System (ADS)
Hummler, K.; Fähnle, M.
1992-02-01
The local magnetic moments and the valence contribution to the crystal-field parameter A02 at the rare-earth sites are calculated for scrR2Fe14B with scrR=Gd, Tb, Dy, Ho, and Er within the framework of the linear-muffin-tin-orbital theory and the local-spin-density approximation. Thereby, the 4f moments of scrR are calculated by the Russel-Saunders scheme, but the radial 4f spin density was part of the self-consistent density-functional calculation. The local moments as well as A02 averaged over the two crystallographically inequivalent scrR sites remain remarkably constant across the series.
Boseggia, S; Walker, H C; Vale, J; Springell, R; Feng, Z; Perry, R S; Moretti Sala, M; Rønnow, H M; Collins, S P; McMorrow, D F
2013-10-23
Sr2IrO4 is a prototype of the class of Mott insulators in the strong spin-orbit interaction (SOI) limit described by a Jeff = 1/2 ground state. In Sr2IrO4, the strong SOI is predicted to manifest itself in the locking of the canting of the magnetic moments to the correlated rotation by 11.8(1)° of the oxygen octahedra that characterizes its distorted layered perovskite structure. Using x-ray resonant scattering at the Ir L3 edge we have measured accurately the intensities of Bragg peaks arising from different components of the magnetic structure. From a careful comparison of integrated intensities of peaks due to basal-plane antiferromagnetism, with those due to b-axis ferromagnetism, we deduce a canting of the magnetic moments of 12.2(8)°. We thus confirm that in Sr2IrO4 the magnetic moments rigidly follow the rotation of the oxygen octahedra, indicating that, even in the presence of significant non-cubic structural distortions, it is a close realization of the Jeff = 1/2 state. PMID:24067396
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
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.
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.
Arbitrary function generator for APS injector synchrotron correction magnets
Despe, O.D.
1990-11-07
The APS injector synchrotron ring measures about 368 m in circumference. In order to obtain the precision of the magnetic field required for the positron acceleration from 450 Mev to 7.7 Gev with low beam loss, eighty correction magnets are distributed around its circumference. These magnets provide the vernier field changes required for beam orbit correction during the acceleration phase of the injector synchrotron cycle. Because of mechanical imperfections in the construction, as well as installation of real dipole and multi-pole magnets, the exact field correction required at each correction magnet location is not known until a beam is actually accelerated. It is therefore essential that a means is provided to generate a correction field that is a function of the beam energy from injection until extraction for each correction magnet. The fairly large number of correction magnets in the system requires that the arbitrary function generator design be as simple as possible yet provide the required performance. An important, required performance feature is that the function can be changed or modified ``on the fly``, to provide the operator with a real-time feel during the tune up process. The arbitrary function generator described in this report satisfies these requirements.
Generation of Primordial Magnetic Fields on Linear Overdensity Scales
NASA Astrophysics Data System (ADS)
Naoz, Smadar; Narayan, Ramesh
2013-08-01
Magnetic fields appear to be present in all galaxies and galaxy clusters. Recent measurements indicate that a weak magnetic field may be present even in the smooth low density intergalactic medium. One explanation for these observations is that a seed magnetic field was generated by some unknown mechanism early in the life of the Universe, and was later amplified by various dynamos in nonlinear objects like galaxies and clusters. We show that a primordial magnetic field is expected to be generated in the early Universe on purely linear scales through vorticity induced by scale-dependent temperature fluctuations, or equivalently, a spatially varying speed of sound of the gas. Residual free electrons left over after recombination tap into this vorticity to generate magnetic field via the Biermann battery process. Although the battery operates even in the absence of any relative velocity between dark matter and gas at the time of recombination, the presence of such a relative velocity modifies the predicted spatial power spectrum of the magnetic field. At redshifts of order a few tens, we estimate a root mean square field strength of order 10-25-10-24G on comoving scales ˜10kpc. This field, which is generated purely from linear perturbations, is expected to be amplified significantly after reionization, and to be further boosted by dynamo processes during nonlinear structure formation.
Generation of primordial magnetic fields on linear overdensity scales.
Naoz, Smadar; Narayan, Ramesh
2013-08-01
Magnetic fields appear to be present in all galaxies and galaxy clusters. Recent measurements indicate that a weak magnetic field may be present even in the smooth low density intergalactic medium. One explanation for these observations is that a seed magnetic field was generated by some unknown mechanism early in the life of the Universe, and was later amplified by various dynamos in nonlinear objects like galaxies and clusters. We show that a primordial magnetic field is expected to be generated in the early Universe on purely linear scales through vorticity induced by scale-dependent temperature fluctuations, or equivalently, a spatially varying speed of sound of the gas. Residual free electrons left over after recombination tap into this vorticity to generate magnetic field via the Biermann battery process. Although the battery operates even in the absence of any relative velocity between dark matter and gas at the time of recombination, the presence of such a relative velocity modifies the predicted spatial power spectrum of the magnetic field. At redshifts of order a few tens, we estimate a root mean square field strength of order 10(-25)-10(-24) G on comoving scales ~10 kpc. This field, which is generated purely from linear perturbations, is expected to be amplified significantly after reionization, and to be further boosted by dynamo processes during nonlinear structure formation. PMID:23952384
Exchange-Spring Magnets: Nanocomposite Exchange-Spring Magnets for Motor and Generator Applications
2012-01-01
REACT Project: ANL will develop a cost-effective exchange-spring magnet to use in the electric motors of wind generators and EVs that uses no rare earth materials. This ANL exchange-spring magnet combines a hard magnetic outer shell with a soft magnetic inner core—coupling these together increases the performance (energy density and operating temperature). The hard and soft magnet composite particles would be created at the molecular level, followed by consolidation in a magnetic field. This process allows the particles to be oriented to maximize the magnetic properties of low-cost and abundant metals, eliminating the need for expensive imported rare earths. The ultimate goal of this project is to demonstrate this new type of magnet in a prototype electric motor.
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.
NASA Astrophysics Data System (ADS)
Ferrer, R.; Bree, N.; Cocolios, T. E.; Darby, I. G.; De Witte, H.; Dexters, W.; Diriken, J.; Elseviers, J.; Franchoo, S.; Huyse, M.; Kesteloot, N.; Kudryavtsev, Yu.; Pauwels, D.; Radulov, D.; Roger, T.; Savajols, H.; Van Duppen, P.; Venhart, M.
2014-01-01
In-gas-cell laser ionization spectroscopy studies on the neutron deficient 97-101Ag isotopes have been performed with the LISOL setup. Magnetic dipole moments and mean-square charge radii have been determined for the first time with the exception of 101Ag, which was found in good agreement with previous experimental values. The reported results allow tentatively assigning the spin of 97,99Ag to 9/2 and confirming the presence of an isomeric state in these two isotopes, whose collapsed hyperfine structure suggests a spin of 1/2 >. The effect of the N=50 shell closure is not only manifested in the magnetic moments but also in the evolution of the mean-square charge radii of the isotopes investigated, in accordance with the spherical droplet model predictions.
Self-generated Turbulence in Magnetic Reconnection
NASA Astrophysics Data System (ADS)
Oishi, Jeffrey S.; Mac Low, Mordecai-Mark; Collins, David C.; Tamura, Moeko
2015-06-01
Classical Sweet-Parker models of reconnection predict that reconnection rates depend inversely on the resistivity, usually parameterized using the dimensionless Lundquist number (S). We describe magnetohydrodynamic (MHD) simulations using a static, nested grid that show the development of a three-dimensional (3D) instability in the plane of a current sheet between reversing field lines without a guide field. The instability leads to rapid reconnection of magnetic field lines at a rate independent of S over at least the range 3.2× {{10}3}≲ S≲ 3.2× {{10}5} resolved by the simulations. We find that this instability occurs even for cases with S≲ {{10}4} that in our models appear stable to the recently described, two-dimensional, plasmoid instability. Our results suggest that 3D, MHD processes alone produce fast (resistivity independent) reconnection without recourse to kinetic effects or external turbulence. The unstable reconnection layers provide a self-consistent environment in which the extensively studied turbulent reconnection process can occur.
Modeling HEDLA magnetic field generation experiments on laser facilities
NASA Astrophysics Data System (ADS)
Fatenejad, M.; Bell, A. R.; Benuzzi-Mounaix, A.; Crowston, R.; Drake, R. P.; Flocke, N.; Gregori, G.; Koenig, M.; Krauland, C.; Lamb, D.; Lee, D.; Marques, J. R.; Meinecke, J.; Miniati, F.; Murphy, C. D.; Park, H.-S.; Pelka, A.; Ravasio, A.; Remington, B.; Reville, B.; Scopatz, A.; Tzeferacos, P.; Weide, K.; Woolsey, N.; Young, R.; Yurchak, R.
2013-03-01
The Flash Center is engaged in a collaboration to simulate laser driven experiments aimed at understanding the generation and amplification of cosmological magnetic fields using the FLASH code. In these experiments a laser illuminates a solid plastic or graphite target launching an asymmetric blast wave into a chamber which contains either Helium or Argon at millibar pressures. Induction coils placed several centimeters away from the target detect large scale magnetic fields on the order of tens to hundreds of Gauss. The time dependence of the magnetic field is consistent with generation via the Biermann battery mechanism near the blast wave. Attempts to perform simulations of these experiments using the FLASH code have uncovered previously unreported numerical difficulties in modeling the Biermann battery mechanism near shock waves which can lead to the production of large non-physical magnetic fields. We report on these difficulties and offer a potential solution.
NASA Astrophysics Data System (ADS)
De Sanctis, M.; Ferretti, J.; Santopinto, E.; Vassallo, A.
2016-05-01
The relativistic interacting quark-diquark model of baryons, recently developed, is here extended introducing in the mass operator a spin-isospin transition interaction. This refined version of the model is used to calculate the non-strange baryon spectrum. The results are compared to the present experimental data. A preliminary calculation of the magnetic moments of the proton and neutron is also presented.
NASA Astrophysics Data System (ADS)
Zhevlakov, A. S.; Radzhabov, A. E.; Dorokhov, A. E.
2010-11-01
The muon contribution to the anomalous magnetic moment from light-by-light scattering diagrams with pion participation is calculated for a nonlocal chiral quark model. For various nonlocal model parameterizations, the contribution makes a μ Had,LbL = 5.1(0.2) 10-10. Later on, we plan to calculate contributions from diagrams with an intermediate scalar meson and quark boxing.
Fano resonance generated by magnetic scatterer in micro metal slit
NASA Astrophysics Data System (ADS)
Zhou, Yun-Song; Wang, Pei-Jie; Wang, Hai; Feng, Sheng-Fei
2014-09-01
A micro metal slit/magnetic scatterer structure is proposed to generate electromagnetic Fano resonance. The magnetic scatterer is formed by infinite long split cylinder resonator array. The analytical transmissivity formulas are deduced from Maxwell electromagnetic theory and the Fano resonance transmission is achieved by the theoretical calculations. The enhancement of environment refractive index leads to an ultrasensitive and linear red shift of resonance peak in the THz range.
A permanent magnet tubular linear generator for wave energy conversion
NASA Astrophysics Data System (ADS)
Yu, Haitao; Liu, Chunyuan; Yuan, Bang; Hu, Minqiang; Huang, Lei; Zhou, Shigui
2012-04-01
A novel three-phase permanent magnet tubular linear generator (PMTLG) with Halbach array is proposed for the sea wave energy conversion. Non-linear axi-symmetrical finite element method (FEM) is implemented to calculate the magnetic fields along air-gap for different Halbach arrays of PMTLGs. The PMTLG characteristics are analyzed and the simulation results are validated by the experiment. An assistant tooth is implemented to greatly minimize the end and cogging effects which cause the oscillatory detent force.
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.
Magnetic Field Generation and Electron Acceleration in Relativistic Laser Channel
I.Yu. Kostyukov; G. Shvets; N.J. Fisch; J.M. Rax
2001-12-12
The interaction between energetic electrons and a circularly polarized laser pulse inside an ion channel is studied. Laser radiation can be resonantly absorbed by electrons executing betatron oscillations in the ion channel and absorbing angular momentum from the laser. The absorbed angular momentum manifests itself as a strong axial magnetic field (inverse Faraday effect). The magnitude of this magnetic field is calculated and related to the amount of the absorbed energy. Absorbed energy and generated magnetic field are estimated for the small and large energy gain regimes. Qualitative comparisons with recent experiments are also made.
Intense transient magnetic-field generation by laser plasma
Benjamin, R.F.
1981-08-18
In a laser system, the return current of a laser generated plasma is conducted near a target to subject that target to the magnetic field thereof. In alternate embodiments the target may be either a small non-fusion object for testing under the magnetic field or a laser-fusion pellet. In the laser-fusion embodiment, the laser-fusion pellet is irradiated during the return current flow and the intense transient magnetic field is used to control the hot electrons thereof to hinder them from striking and heating the core of the irradiated laser-fusion pellet.
NASA Astrophysics Data System (ADS)
Sluchanko, N. E.; Azarevich, A. N.; Anisimov, M. A.; Bogach, A. V.; Gavrilkin, S. Yu.; Gilmanov, M. I.; Glushkov, V. V.; Demishev, S. V.; Khoroshilov, A. L.; Dukhnenko, A. V.; Mitsen, K. V.; Shitsevalova, N. Yu.; Filippov, V. B.; Voronov, V. V.; Flachbart, K.
2016-02-01
Based on low-temperature resistivity, heat capacity, and magnetization investigations, we show that the unusually strong suppression of superconductivity in LuxZr1 -xB12 (x <8 % ) BCS-type superconductors is caused by the emergence of static spin polarization in the vicinity of nonmagnetic lutetium impurities. The analysis of the obtained results points to a formation of static magnetic moments with μeff≈6 μB per Lu3 + ion (1S0 ground state, 4 f14 configuration) incorporated in the superconducting ZrB12 matrix. The size of these spin-polarized nanodomains was estimated to be about 5 Å.
Laser propagation and soliton generation in strongly magnetized plasmas
NASA Astrophysics Data System (ADS)
Feng, W.; Li, J. Q.; Kishimoto, Y.
2016-03-01
The propagation characteristics of various laser modes with different polarization, as well as the soliton generation in strongly magnetized plasmas are studied numerically through one-dimensional (1D) particle-in-cell (PIC) simulations and analytically by solving the laser wave equation. PIC simulations show that the laser heating efficiency substantially depends on the magnetic field strength, the propagation modes of the laser pulse and their intensities. Generally, large amplitude laser can efficiently heat the plasma with strong magnetic field. Theoretical analyses on the linear propagation of the laser pulse in both under-dense and over-dense magnetized plasmas are well confirmed by the numerical observations. Most interestingly, it is found that a standing or moving soliton with frequency lower than the laser frequency is generated in certain magnetic field strength and laser intensity range, which can greatly enhance the laser heating efficiency. The range of magnetic field strength for the right-hand circularly polarized (RCP) soliton formation with high and low frequencies is identified by solving the soliton equations including the contribution of ion's motion and the finite temperature effects under the quasi-neutral approximation. In the limit of immobile ions, the RCP soliton tends to be peaked and stronger as the magnetic field increases, while the enhanced soliton becomes broader as the temperature increases. These findings in 1D model are well validated by 2D simulations.
Fully magnetic printing by generation of magnetic droplets on demand with a coilgun
NASA Astrophysics Data System (ADS)
Vekselman, Vladislav; Sande, Luke; Kornev, Konstantin G.
2015-12-01
In this paper, we exhibit a coilgun-based approach to drop-on-demand printing of liquids laden with magnetic particles. In contrast to other drop-on-demand technologies designed to print droplets only in gaseous environments, this methodology allows one to print magnetic droplets inside any gaseous or liquid media using the same coilgun. Furthermore, we demonstrate the basic principles of magnetic drop-on-demand generation and show the physico-chemical parameters controlling the process.
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).
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).
Magnetic Fields generated in the Solar Wind Interaction with Mars
NASA Astrophysics Data System (ADS)
Vennerstrom, S.; Primdahl, F.
The solar wind interaction with Mars has revealed a complexity that provide a major challenge for planetary exploration, and which places it as a central issue of current research in space physics. The combined effect of direct interaction between the solar wind and the atmosphere and the formation of mini-magnetospheres around the strong crustal anomalies is unique in the solar system and so far largely unexplored. The most extensive set of magnetic field observations near Mars comes from more than six years of operation of the Mars Global Surveyor MAG/ER measurements. These reveal both piled-up magnetic disturbances generated in the interaction with the atmosphere as well as significant perturbations associated with a direct interaction between the solar wind and the crustal fields. While the magnetic field in the pile-up region are generally closely associated with the upstream solar wind parameters, the perturbations close to the magnetic anomalies and in the ionosphere are much more complex. Combined magnetic field and plasma observations in the martian ionosphere as proposed in the Mars Escape and Magnetic Orbiter (MEMO) are clearly needed. In addition surface magnetic observations characterizing magnetic activity at Mars are highly called for.
Intense magnetic field generation by solidification and crustal delamination
NASA Astrophysics Data System (ADS)
Neufeld, J. A.; Bryson, J. F. J.; Nimmo, F.
2015-12-01
Recent paleomagnetic measurements of meteorites suggest that asteroidal magnetic fields are a common feature of the early solar system [1,2]. The iron cores of different asteroids may solidify in different ways [3]. For the IVA iron meteorite parent body the rapid cooling rates and correlation with Ni concentrations further suggest that their parent body was entirely metal, and that solidification of their parent asteroid proceeded from the top down. Here we present model constraints on the thermo-chemical evolution of such rapidly cooled iron asteroids. We show that the temperature of the liquid is rapidly well mixed, and equal to the composition-dependent freezing point, and that thermal convection contributes only at early times to generation of intense magnetic fields and is therefore not sufficient to explain the generation of a dynamo. Instead, we propose that viscous delamination [4] at the base of the solidifying, dense crust provides a sufficient buoyancy flux to generate a magnetic field with properties consistent with those inferred from paleomagnetic measurements of the two IVA meteorites [5]. A model that captures the aggregate effect of episodic delamination events predicts the evolution of the crust and the formation and growth of the asteroid core, the intensity and directional evolution of the magnetic field through time, and the times at which magnetic field generation ceases and total asteroid solidification occur. These predictions can be compared directly with recent measurements of IVA iron meteorites [5] with implications for top-down solidification, the solid structure of the IVA parent core, and magnetic field generation both on the IVA parent body, and wider implications for top-down core solidification generally. [1] Weiss et al. Space Sci. Rev. 152, 341-390 (2010). [2] Tarduno et al. Science. 338, 939-942 (2012). [3] Williams Earth Planet. Sci. Lett. 284, 564-569 (2009) [4] Molnar et al. Geophys. J. Int. 133, 568-584 (1998) [5] Bryson et
NASA Astrophysics Data System (ADS)
Yang, X. I. A.; Meneveau, C.; Marusic, I.; Biferale, L.
2016-08-01
In wall-bounded turbulence, the moment generating functions (MGFs) of the streamwise velocity fluctuations
Relativistic Scott correction in self-generated magnetic fields
NASA Astrophysics Data System (ADS)
Erdős, László; Fournais, Søren; Solovej, Jan Philip
2012-09-01
We consider a large neutral molecule with total nuclear charge Z in a model with self-generated classical magnetic field and where the kinetic energy of the electrons is treated relativistically. To ensure stability, we assume that Zα < 2/π, where α denotes the fine structure constant. We are interested in the ground state energy in the simultaneous limit Z → ∞, α → 0 such that κ = Zα is fixed. The leading term in the energy asymptotics is independent of κ, it is given by the Thomas-Fermi energy of order Z7/3 and it is unchanged by including the self-generated magnetic field. We prove the first correction term to this energy, the so-called Scott correction of the form S(αZ)Z2. The current paper extends the result of Solovej et al. [Commun. Pure Appl. Math. LXIII, 39-118 (2010)] on the Scott correction for relativistic molecules to include a self-generated magnetic field. Furthermore, we show that the corresponding Scott correction function S, first identified by Solovej et al. [Commun. Pure Appl. Math. LXIII, 39-118 (2010)], is unchanged by including a magnetic field. We also prove new Lieb-Thirring inequalities for the relativistic kinetic energy with magnetic fields.
Design and Analysis of Tubular Permanent Magnet Linear Wave Generator
Si, Jikai; Feng, Haichao; Su, Peng; Zhang, Lufeng
2014-01-01
Due to the lack of mature design program for the tubular permanent magnet linear wave generator (TPMLWG) and poor sinusoidal characteristics of the air gap flux density for the traditional surface-mounted TPMLWG, a design method and a new secondary structure of TPMLWG are proposed. An equivalent mathematical model of TPMLWG is established to adopt the transformation relationship between the linear velocity of permanent magnet rotary generator and the operating speed of TPMLWG, to determine the structure parameters of the TPMLWG. The new secondary structure of the TPMLWG contains surface-mounted permanent magnets and the interior permanent magnets, which form a series-parallel hybrid magnetic circuit, and their reasonable structure parameters are designed to get the optimum pole-arc coefficient. The electromagnetic field and temperature field of TPMLWG are analyzed using finite element method. It can be included that the sinusoidal characteristics of air gap flux density of the new secondary structure TPMLWG are improved, the cogging force as well as mechanical vibration is reduced in the process of operation, and the stable temperature rise of generator meets the design requirements when adopting the new secondary structure of the TPMLWG. PMID:25050388
A 7 T Pulsed Magnetic Field Generator for Magnetized Laser Plasma Experiments
NASA Astrophysics Data System (ADS)
Hu, Guangyue; Liang, Yihan; Song, Falun; Yuan, Peng; Wang, Yulin; Zhao, Bin; Zheng, Jian
2015-02-01
A pulsed magnetic field generator was developed to study the effect of a magnetic field on the evolution of a laser-generated plasma. A 40 kV pulsed power system delivered a fast (~230 ns), 55 kA current pulse into a single-turn coil surrounding the laser target, using a capacitor bank of 200 nF, a laser-triggered switch and a low-impedance strip transmission line. A one-dimensional uniform 7 T pulsed magnetic field was created using a Helmholtz coil pair with a 6 mm diameter. The pulsed magnetic field was controlled to take effect synchronously with a nanosecond heating laser beam, a femtosecond probing laser beam and an optical Intensified Charge Coupled Device (ICCD) detector. The preliminary experiments demonstrate bifurcation and focusing of plasma expansion in a transverse magnetic field.
Laser-generated magnetic fields in quasi-hohlraum geometries
NASA Astrophysics Data System (ADS)
Pollock, Bradley; Turnbull, David; Ross, Steven; Hazi, Andrew; Ralph, Joseph; Lepape, Sebastian; Froula, Dustin; Haberberger, Dan; Moody, John
2014-10-01
Laser-generated magnetic fields of 10--40 T have been produced with 100--4000 J laser drives at Omega EP and Titan. The fields are generated using the technique described by Daido et al. [Phys. Rev. Lett. 56, 846 (1986)], which works by directing a laser through a hole in one plate to strike a second plate. Hot electrons generated in the laser-produced plasma on the second plate collect on the first plate. A strap connects the two plates allowing a current of 10 s of kA to flow and generate a solenoidal magnetic field. The magnetic field is characterized using Faraday rotation, b-dot probes, and proton radiography. Further experiments to study the effect of the magnetic field on hohlraum performance are currently scheduled for Omega. This work was performed under the auspices of the United States Department of Energy by the Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA-27344.
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.
DC Magnetic Field Generation by Nonlinear Whis-tlers
NASA Astrophysics Data System (ADS)
Stenzel, R. L.; Urrutia, J. M.; Griskey, M. C.
1998-11-01
A magnetic loop antenna is immersed into a large laboratory plasma (1 m diam, 2.5 m length, 10^12 cm-3, 3 eV, 5 G). It excites whistlers whose wave magnetic field exceeds the ambient dc field.(R. L. Stenzel and J. M. Urrutia, Phys. Rev. Lett. (1998).) The periodic reversal of both the electric and magnetic field produces a time-average electron Hall currents which results in the generation of a dc magnetic field. Copious harmonics of the fundamental frequency are produced. The propagation of nonlinear whistlers depends on amplitude and field direction. These phenomena are important for the excitation of large amplitude whistler with antennas in space.
The next generation Antarctic digital magnetic anomaly map
von Frese, R.R.B; Golynsky, A.V.; Kim, H.R.; Gaya-Piqué, L.; Thébault, E.; Chiappinii, M.; Ghidella, M.; Grunow, A.; ADMAP Working Group
2007-01-01
S (Golynsky et al., 2001). This map synthesized over 7.1 million line-kms of survey data available up through 1999 from marine, airborne and Magsat satellite observations. Since the production of the initial map, a large number of new marine and airborne surveys and improved magnetic observations from the Ørsted and CHAMP satellite missions have become available. In addition, an improved core field model for the Antarctic has been developed to better isolate crustal anomalies in these data. The next generation compilation also will likely represent the magnetic survey observations of the region in terms of a high-resolution spherical cap harmonic model. In this paper, we review the progress and problems of developing an improved magnetic anomaly map to facilitate studies of the Antarctic crustal magnetic field
Quantification of Low Frequency Magnetic Fields Generated by Household Appliances
NASA Astrophysics Data System (ADS)
Tanaka, Kenji; Mizuno, Yukio; Naito, Katsuhiko
Resultant low frequency magnetic field generated was measured as a function of distance from them over broadband range (40-800Hz) and harmonic range (100-800Hz) on eleven kinds and more than two hundred recent household appliances in total. The relationship between magnetic filed measured and the power consumption of household appliances was also examined. As a result, it is verified that magnetic field from appliances is drastically reduced as the distance goes. And, any clear dependence of what on the power consumption of appliances is not recognized. Furthermore, from harmonic component analysis by using FFT for current flowing in appliances, it is assumed that relatively large amount of harmonic components with odd numbers is contained in the magnetic field.
NASA Astrophysics Data System (ADS)
Shang, Zhi-Feng; Qi, Wei-Hua; Ji, Deng-Hui; Xu, Jing; Tang, Gui-De; Zhang, Xiao-Yun; Li, Zhuang-Zhi; Lang, Li-Li
2014-10-01
(A)[B]2O4 ferrite samples with the composition Co1-xCrxFe2O4 (0.0 <= x <= 1.0) are prepared using a hydrothermal method, and subjected to calcining in atube furnace with an argon-flow at 1673 K for 2 h. X-ray diffraction patterns indicate that each of all the samples has a single phase cubic spinel structure with a space group of Fd3¯m. Magnetic measurements show that the saturation magnetization decreases with as the Cr content x increases. The cation distribution of the samples is estimated by fitting the dependence of the magnetic moments on x at 10 K, using the quantum mechanical model previously proposed by our group. The calculated sum of the content values of the Cr3+ and Cr2+ cations occupying the (A) sites increases as the value of x increases. In the fitting process, the magnetic moment directions of the Cr3+ and Cr2+ cations are assumed to be antiparallel to those of the Fe and Co cations, respectively, which is in accordance with Hund's rules.
Generation of Whistler Wave by a Rotating Magnetic Field Source
NASA Astrophysics Data System (ADS)
Karavaev, A.; Papadopoulos, K.; Shao, X.; Sharma, A. S.; Gigliotti, A.; Gekelman, W.; Pribyl, P.; Vincena, S.
2008-12-01
The interaction of Rotating Magnetic Fields (RMF) with plasmas is a fundamental plasma physics problem with implications to fusion related Field-Reversed Configurations (FRC), space propulsion, astronaut protection from cosmic rays in long interstellar travel, control of the energetic population in the radiation belts and near zone processes in pulsar magnetospheres. In this paper we report recent experiments on the generation of whistler waves with a new type RMF-based antenna. The experiments were conducted on UCLA's Large Plasma Device (LAPD). The Rotating Magnetic Field (RMF) is created using poly-phased loop antennas. A number of parameter combinations, e.g. plasma density, background magnetic field, and driving current, were used. It was found that RMF created by a two phase-delayed loop antenna drives significant currents along the ambient magnetic field. The measured amplitude of induced wave field was proportional to the square-root of the plasma density. The spatial decay rate for the wave perturbation across the background magnetic field was found to scale with the plasma skin depth. A small amplitude second harmonic was also measured. The paper will also present analytic and simulation results that account for the experimental results; in particular, the scaling of the induced magnetic field as a function of the RMF and plasma parameters and the spatial decay rate of magnetic field. Applications of RMF as an efficient radiation source of plasma waves in space plasmas will be discussed. This work was sponsored by ONR MURI Grant 5-28828
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.
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
Methods of high current magnetic field generator for transcranial magnetic stimulation application
NASA Astrophysics Data System (ADS)
Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.
2015-05-01
This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.
Methods of high current magnetic field generator for transcranial magnetic stimulation application
Bouda, N. R. Pritchard, J.; Weber, R. J.; Mina, M.
2015-05-07
This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/−20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.
NASA Astrophysics Data System (ADS)
Stefańska, Patrycja
2016-02-01
We consider a Dirac one-electron atom placed in a weak, static, uniform magnetic field. We show that, to the first order in the strength B of the external field, the only electric multipole moments, which are induced by the perturbation in the atom, are those of an even order. Using the Sturmian expansion of the generalized Dirac-Coulomb Green function [R. Szmytkowski, J. Phys. B 30, 825 (1997), 10.1088/0953-4075/30/4/007; J. Phys. B 30, 2747 (1997), 10.1088/0953-4075/30/11/023], We derive a closed-form expression for the electric quadrupole moment induced in the atom in an arbitrary discrete energy eigenstate. The result, which has the form of a double finite sum involving the generalized hypergeometric functions 3F2 of the unit argument, agrees with the earlier relativistic formula for that quantity, obtained by us for the ground state of the atom.
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.
Spin transfer torque generated magnetic droplet solitons (invited)
Chung, S.; Mohseni, S. M.; Sani, S. R.; Iacocca, E.; Dumas, R. K.; Pogoryelov, Ye.; Anh Nguyen, T. N.; Muduli, P. K.; Eklund, A.; Hoefer, M.; Åkerman, J.
2014-05-07
We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy.
Resistive Generation of Intergalactic Magnetic Field at Cosmic Dawn
NASA Astrophysics Data System (ADS)
Miniati, F.; Bell, A. R.
2012-07-01
Miniati & Bell (2011) proposed a mechanism for the generation of magnetic seeds that is based the finite resistivity of the low temperature IGM in the high redshift universe. In this model, cosmic-ray protons generated by the first generation of galaxies, escape into the intergalactic medium carrying an electric current that induces return currents, jt, and associated electric fields, E = ηjt there. Because the resistivity, η, depends on the IGM temperature, which is highly inhomogeneous due to adiabatic contraction and shocks produced by structure formation, a non-vanishing curl of the electric field exists which sustains the growth of magnetic field. In this contribution we have developed an approximate numerical model for this process by implementing the source terms of the resistive mechanism in the cosmological code CHARM. Our numerical estimates substantiate the earlier analysis in Miniati & Bell (2011) which found magnetic seeds between 10-18 and 10-16 Gauss throughout cosmic space at redshift z ˜ 6, consistent with conservative estimates of magnetic fields in voids at z ˜ 0 from recent gamma-ray experiments.
Energy confinement and magnetic field generation in the SSPX spheromak
Hudson, B; McLean, H S; Wood, R D; Hooper, E B; Hill, D N; Jayakumar, J; Moller, J; Romero-Talamas, C; Casper, T A; LoDestro, L L; Pearlstein, L D; Johnson, III, J A; Mezonlin, E
2008-02-11
The Sustained Spheromak Physics Experiment (SSPX) [E.B. Hooper, et. al., Nuclear Fusion, Vol. 39, No. 7] explores the physics of efficient magnetic field buildup and energy confinement, both essential parts of advancing the spheromak concept. Extending the spheromak formation phase increases the efficiency of magnetic field generation with the maximum edge magnetic field for a given injector current (B/I) from 0.65 T/MA previously to 0.9 T/MA. We have achieved the highest electron temperatures (T{sub e}) recorded for a spheromak with T{sub e} > 500 eV, toroidal magnetic field {approx}1 T and toroidal current ({approx}1 MA) [R.D. Wood, D.N. Hill, H.S. McLean, E.B. Hooper, B.F. Hudson, J.M. Moller, 'Improved magnetic field generation efficiency and higher temperature spheromak plasmas', submitted to Physical Review Letters]. Extending the sustainment phase to > 8 ms extends the period of low magnetic fluctuations (< 1 %) by 50%. The NIMROD 3-D resistive MHD code [C.R. Sovinec, T.A. Gianakon, E.D. Held, S.E. Kruger and D.D. Schnack, The NIMROD Team, Phys. Plasmas 10, 1727 (2003)] reproduces the observed flux amplification {Psi}{sub pol}/{Psi}{sub gun}. Successive gun pulses are demonstrated to maintain the magnetic field in a quasi-steady state against resistive decay. Initial measurements of neutral particle flux in multi-pulse operation show charge-exchange power loss < 1% of gun input power and dominantly collisional majority ion heating. The evolution of electron temperature shows a distinct and robust feature of spheromak formation: a hollow-to-peaked T{sub e}(r) associated with q {approx} 1/2.
NASA Astrophysics Data System (ADS)
Xue, L. C.; Lang, L. L.; Xu, J.; Li, Z. Z.; Qi, W. H.; Tang, G. D.; Wu, L. Q.
2015-09-01
Powder samples of the spinel ferrites MxNi0.7-xFe2.3O4 (M = Cr, Co and 0.0 ≤ x ≤ 0.3) and CrxNi0.7Fe2.3-xO4 (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 (μexp) per formula both at 10 K and 300 K increased with Co substitution, while the values of μexp decreased with Cr substitution. Applying the assumption that the magnetic moments of Cr2+ and Cr3+ 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 μexp, 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.
NASA Astrophysics Data System (ADS)
Damewood, L.; Busemeyer, B.; Shaughnessy, M.; Fong, C. Y.; Yang, L. H.; Felser, C.
2015-02-01
Due to their similarities to metastable zinc-blende half-metals, we systematically examined the half-Heusler compounds β -LiMnZ (Z =N,P and Si) for their electronic, magnetic, and stability properties at optimized lattice constants and strained lattice constants that exhibit half-metallic properties. We also report the other phases of the half-Heusler structure (α and γ phases), but they are unlikely to be grown. The magnetic moments of these stable Li-based compounds are expected to reach as high as 4 μB per unit cell when Z =Si and 5 μB per unit cell when Z =N and P; however, the antiferromagnetic spin configuration is energetically favored when Z is a pnictogen. β -LiMnSi at a lattice constant 14% larger than its equilibrium lattice constant is a promising half-metal due to its large magnetic moment, large gap, and vibrational stability. The modified Slater-Pauling rule for these compounds is determined. Finally, we investigated a plausible method for developing half-metallic Li xMn Z at equilibrium by tuning x , but this type of alloying introduces local structural changes that preclude half-metallicity.
Intense ionospheric electric and magnetic field pulses generated by lightning
NASA Technical Reports Server (NTRS)
Kelley, M. C.; Ding, J. G.; Holzworth, R. H.
1990-01-01
Electric and magnetic field measurements have been made in the ionosphere over an active thunderstorm and an optical detector onboard the same rocket yielded an excellent time base for the study of waves radiated into space from the discharge. In addition to detection of intense, but generally well understood whistler mode waves, very unusual electric and magnetic field pulses preceded the 1-10 kHz component of the radiated signal. These pulses lasted several ms and had a significant electric field component parallel to the magnetic field. No known propagating wave mode has this polarization nor a signal propagation velocity as high as those measured here. This study investigated and rejected an explanation based on an anomalous skin depth effect. Although only a hypothesis at this time, a more promising explanation involving the generation of the pulse via a nonlinear decay of whistler mode waves in the frequency range 10-80 kHz is being investigated.
Self-generated magnetic dipoles in weakly magnetized beam-plasma system.
Jia, Qing; Mima, Kunioki; Cai, Hong-bo; Taguchi, Toshihiro; Nagatomo, Hideo; He, X T
2015-02-01
A self-generation mechanism of magnetic dipoles and the anomalous energy dissipation of fast electrons in a magnetized beam-plasma system are presented. Based on two-dimensional particle-in-cell simulations, it is found that the magnetic dipoles are self-organized and play important roles in the beam electron energy dissipation. These dipoles drift slowly in the direction of the return flow with a quasisteady velocity, which depends upon the magnetic amplitude of the dipole and the imposed external magnetic field. This dipole formation provides a mechanism for the anomalous energy dissipation of a relativistic electron beam, which would play an important role in collisionless shock and ion shock acceleration. PMID:25768618
Power generation from human body motion through magnet and coil arrays with magnetic spring
NASA Astrophysics Data System (ADS)
Zhang, Qian; Wang, Yufeng; Kim, Eun Sok
2014-02-01
This article presents a hand-held electromagnetic energy harvester which can be used to harvest tens of mW power level from human body motion. A magnet array, aligned to a coil array for maximum magnetic flux change, is suspended by a magnetic spring for a resonant frequency of several Hz and is stabilized horizontally by graphite sheets for reducing the friction. An analytical model of vibration-driven energy harvester with magnetic spring through magnet and coil arrays is developed to explore the power generation from vibrations at low frequency and large amplitude. When the energy harvester (occupying 120 cc and weighing 180 g) is placed in a backpack of a human walking at various speeds, the power output increases as the walking speed increases from 0.45 m/s (slow walking) to 3.58 m/s (slow running), and reaches 32 mW at 3.58 m/s.
Keller, Dustin M.; Hicks, Kenneth H.
2013-05-01
The transition magnetic moments for decuplet-to-octet baryon electromagnetic decays are calculated from the CLAS experimental results and are compared with calculations to first order in the 1/N{sub c} expansion of quantum chromodynamics (QCD) and new U-spin predictions. Using the U-spin predictions for the {Sigma} *{sup 0} --> {Sigma}{sup 0} {gamma} and {Sigma} *{sup +} → {Sigma}{sup +} {gamma} decays, the SU(3)-forbidden transition {Sigma} *{sup -} → {Sigma}{sup -} {gamma} is obtained. In addition, the doubly strange baryon radiative decay {Xi} *{sup 0} → {Xi} {gamma} is predicted using U-spin.
Generation of scale invariant magnetic fields in bouncing universes
NASA Astrophysics Data System (ADS)
Sriramkumar, L.; Atmjeet, Kumar; Jain, Rajeev Kumar
2015-09-01
We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic field can arise before the bounce for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape after the bounce. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the e-Script N-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and evaluate the spectra of the electric and magnetic fields at a suitable time after the bounce. As one could have intuitively expected, though the complete spectra depend on the details of the bounce, we find that, under the original conditions, scale invariant spectra of the magnetic fields do arise for wavenumbers much smaller than the scale associated with the bounce. We also show that magnetic fields which correspond to observed strengths today can be generated for specific values of the parameters. But, we find that, at the bounce, the backreaction due to the electromagnetic modes that have been generated can be significantly large calling into question the viability of the model. We briefly discuss the implications of our results.
NASA Astrophysics Data System (ADS)
Prester, M.; Drobac, D.; Marohnić, Ž.
2014-07-01
Magnetic dynamics studies by AC susceptibility technique have been performed on the two newest-generation iron deficiency drugs, commercialized under the trade names Feraheme and Monofer. In all aspects, these magnetic nanoparticle systems obey a common pattern of superparamagnetism characterized by similar blocking temperatures, average particle sizes, and magnetocrystalline anisotropy energy. However, effective magnetic moments associated with average particle of each drug are remarkably different, being approximately 10630 μB (Feraheme) and 134 μB (Monofer). The difference relies on qualitatively different magnetic interaction permeating the iron cores of the constituent nanoparticles. The nanoparticle of each system can be classified as monodomain ferrimagnet (Feraheme) and almost compensated antiferromagnet (Monofer). In accordance with different associated moments the dipole-dipole interaction between nanoparticles for the two drugs differs for orders of magnitudes but remains safely small at room temperatures. For reference, the corresponding measurements on previously better investigated iron-sucrose haematinic Venofer has been also performed and included in this article.
Efficiency estimation for permanent magnets of synchronous wind generators
NASA Astrophysics Data System (ADS)
Serebryakov, A.; Levin, N.; Sokolov, A.; Kamolins, E.
2014-02-01
Application of wind generators opens wide possibilities for raising the efficiency of low- and medium-power wind generators (WGs). The mass of generators in the proposed version is smaller, their reliability higher, while maintenance costs are lower. At the same time, the use of high-energy permanent magnets in generators of enhanced power comes up against some obstacles, which can be overcome through proper orientation of magnetization at creation of a magnetic field in the airgap of electrical machine. In this regard, it might be preferable to use magnets with indirect action on the airgap instead of those with direct action. A convincing example of the former variant is a generator with tangentially oriented magnetization of permanent magnets. In the work, an attempt is done to prove the advantages of such installation in modern low- and medium-power WGs Pastāvīgo magnētu pielietošana vējģeneratoros paver plašas iespējas mazas un vidējas jaudas vēja enerģētisko iekārtu (VEI) efektivitātes paaugstināšanai. Turklāt samazinās ģeneratoru masa, palielinās drošums, samazinās ekspluatācijas izmaksas. Tomēr, izmantojot augsti enerģētiskos pastāvīgos magnētus ģeneratoros ar paaugstinātu jaudu, rodas virkne problēmu, kuras sekmīgi iespējams pārvarēt, ja pareizi izvieto magnētus pēc to orientācijas, radot magnētisko lauku elektriskās mašīnas gaisa spraugā. Darbā ir mēģināts pierādīt, ka eksistē būtiskas priekšrocības mazas un vidējas jaudas vējģeneratoros, ja pastāvīgie magnēti tiek magnetizēti tangenciāli attiecībā pret gaisa spraugu.
Magnetic Field Generation During the Collision of Narrow Plasma Clouds
NASA Astrophysics Data System (ADS)
Sakai, Jun-ichi; Kazimura, Yoshihiro; Haruki, Takayuki
1999-06-01
We investigate the dynamics of the collision of narrow plasma clouds,whose transverse dimension is on the order of the electron skin depth.A 2D3V (two dimensions in space and three dimensions in velocity space)particle-in-cell (PIC) collisionless relativistic code is used toshow the generation of a quasi-staticmagnetic field during the collision of narrow plasma clouds both inelectron-ion and electron-positron (pair) plasmas. The localizedstrong magnetic fluxes result in the generation of the charge separationwith complicated structures, which may be sources of electromagneticas well as Langmuir waves. We also present one applicationof this process, which occurs during coalescence of magnetic islandsin a current sheet of pair plasmas.