WorldWideScience

Sample records for macroscopic magnetic properties

  1. Macroscopic behavior and microscopic magnetic properties of nanocarbon

    Energy Technology Data Exchange (ETDEWEB)

    Lähderanta, E., E-mail: Erkki.Lahderanta@lut.fi [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); Ryzhov, V.A. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); Petersburg Nuclear Physics Institute, NRC “Kurchatov Institute”, Orlova Coppice, Gatchina, Leningrad province 188300 (Russian Federation); Lashkul, A.V. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); Galimov, D.M. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); South Ural State University, 454080 Chelyabinsk (Russian Federation); Titkov, A.N. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); A. F. Ioffe Physico-Technical Institute, 194021 St. Petersburg (Russian Federation); Matveev, V.V. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); Saint-Petersburg State University, Saint-Petersburg 198504 (Russian Federation); Mokeev, M.V. [Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg (Russian Federation); Kurbakov, A.I. [Petersburg Nuclear Physics Institute, NRC “Kurchatov Institute”, Orlova Coppice, Gatchina, Leningrad province 188300 (Russian Federation); Lisunov, K.G. [Lappeenranta University of Technology, PO Box 20, FIN-53851 Lappeenranta (Finland); Institute of Applied Physics ASM, Academiei Str., 5, MD 2028 Kishinev (Moldova, Republic of)

    2015-06-01

    Here are presented investigations of powder and glass-like samples containing carbon nanoparticles, not intentionally doped and doped with Ag, Au and Co. The neutron diffraction study reveals an amorphous structure of the samples doped with Au and Co, as well as the magnetic scattering due to a long-range FM order in the Co-doped sample. The composition and molecular structure of the sample doped with Au is clarified with the NMR investigations. The temperature dependence of the magnetization, M (T), exhibits large irreversibility in low fields of B=1–7 mT. M (B) saturates already above 2 T at high temperatures, but deviates from the saturation behavior below ~50 (150 K). Magnetic hysteresis is observed already at 300 K and exhibits a power-law temperature decay of the coercive field, B{sub c} (T). The macroscopic behavior above is typical of an assembly of partially blocked magnetic nanoparticles. The values of the saturation magnetization, M{sub s}, and the blocking temperature, T{sub b}, are obtained as well. However, the hysteresis loop in the Co-doped sample differs from that in other samples, and the values of B{sub c} and M{sub s} are noticeably increased. - Highlights: • We have investigated powder and glassy samples with carbon nanoparticles. • They include an undoped sample and those doped with Ag, Au and Co. • Neutron diffraction study reveals amorphous structure of Au- and Co-doped samples. • Composition and molecular structure of Au-doped sample was investigated with NMR. • Magnetic behavior is typical of an assembly of partially blocked magnetic nanoparticles.

  2. Macroscopic Quantum Coherence in Antiferromagnetic Molecular Magnets

    Institute of Scientific and Technical Information of China (English)

    HU Hui; LO Rong; ZHU Jia-Lin; XIONG Jia-Jiong

    2001-01-01

    The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model. On the basis of instanton technique in the spin-coherent-state path-integral representation, both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained. We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys. Rev. Lett. 80 (1998) 169), but also have great influence on the intensity of the ground-state tunnel splitting. Those features clearly have no analogue in the ferromagnetic molecular magnets. We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets. The analytical results are complemented by exact diagonalization calculation.

  3. Macroscopic Quantum Coherence in Antiferromagnetic Molecular Magnets

    Institute of Scientific and Technical Information of China (English)

    HUHui; LURong; 等

    2001-01-01

    The macroscopic quantum coherence in a biaxial antiferromagnetic molecular magnet in the presence of magnetic field acting parallel to its hard anisotropy axis is studied within the two-sublattice model.On the basis of instanton technique in the spin-coherent-state path-integral representation,both the rigorous Wentzel-Kramers-Brillouin exponent and pre-exponential factor for the ground-state tunnel splitting are obtained.We find that the quantum fluctuations around the classical paths can not only induce a new quantum phase previously reported by Chiolero and Loss (Phys.Rev.Lett.80(1998)169),but also have great influence on the intensity of the ground-state tunnel splitting.Those features clearly have no analogue in the ferromagnetic molecular magnets.We suggest that they may be the universal behaviors in all antiferromagnetic molecular magnets.The analytical results are complemented by exact diagonalization calculation.

  4. Self-Feeding Turbulent Magnetic Reconnection on Macroscopic Scales

    CERN Document Server

    Lapenta, Giovanni

    2008-01-01

    Within a MHD approach we find magnetic reconnection to progress in two entirely different ways. The first is well-known: the laminar Sweet-Parker process. But a second, completely different and chaotic reconnection process is possible. This regime has properties of immediate practical relevance: i) it is much faster, developing on scales of the order of the Alfv\\'en time, and ii) the areas of reconnection become distributed chaotically over a macroscopic region. The onset of the faster process is the formation of closed circulation patterns where the jets going out of the reconnection regions turn around and forces their way back in, carrying along copious amounts of magnetic flux.

  5. Self-feeding turbulent magnetic reconnection on macroscopic scales.

    Science.gov (United States)

    Lapenta, Giovanni

    2008-06-13

    Within a MHD approach we find magnetic reconnection to progress in two entirely different ways. The first is well known: the laminar Sweet-Parker process. But a second, completely different and chaotic reconnection process is possible. This regime has properties of immediate practical relevance: (i) it is much faster, developing on scales of the order of the Alfvén time, and (ii) the areas of reconnection become distributed chaotically over a macroscopic region. The onset of the faster process is the formation of closed-circulation patterns where the jets going out of the reconnection regions turn around and force their way back in, carrying along copious amounts of magnetic flux.

  6. Determining the Macroscopic Properties of Relativistic Jets

    Science.gov (United States)

    Hardee, P. E.

    2004-08-01

    The resolved relativistic jets contain structures whose observed proper motions are typically assumed to indicate the jet flow speed. In addition to structures moving with the flow, various normal mode structures such as pinching or helical and elliptical twisting can be produced by ejection events or twisting perturbations to the jet flow. The normal mode structures associated with relativistic jets, as revealed by numerical simulation, theoretical calculation, and suggested by observation, move more slowly than the jet speed. The pattern speed is related to the jet speed by the sound speed in the jet and in the surrounding medium. In the event that normal mode structures are observed, and where proper motions of pattern and flow speed are available or can be estimated, it is possible to determine the sound speed in the jet and surrounding medium. Where spatial development of normal mode structures is observed, it is possible to make inferences as to the heating rate/macroscopic viscosity of the jet fluid. Ultimately it may prove possible to separate the microscopic energization of the synchrotron radiating particles from the macroscopic heating of the jet fluid. Here I present the relevant properties of useful normal mode structures and illustrate the use of this technique. Various aspects of the work presented here have involved collaboration with I. Agudo (Max-Planck, Bonn), M.A. Aloy (Max-Planck, Garching), J. Eilek (NM Tech), J.L. Gómez (U. Valencia), P. Hughes (U. Michigan), A. Lobanov (Max-Planck, Bonn), J.M. Martí (U. Valencia), & C. Walker (NRAO).

  7. Macroscopic Simulation of Isotropic Permanent Magnets

    CERN Document Server

    Bruckner, Florian; Vogler, Christoph; Heinrichs, Frank; Satz, Armin; Ausserlechner, Udo; Binder, Gernot; Koeck, Helmut; Suess, Dieter

    2015-01-01

    Accurate simulations of isotropic permanent magnets require to take the magnetization process into account and consider the anisotropic, nonlinear, and hysteretic material behaviour near the saturation configuration. An efficient method for the solution of the magnetostatic Maxwell equations including the description of isotropic permanent magnets is presented. The algorithm can easily be implemented on top of existing finite element methods and does not require a full characterization of the hysteresis of the magnetic material. Strayfield measurements of an isotropic permanent magnet and simulation results are in good agreement and highlight the importance of a proper description of the isotropic material.

  8. Macroscopic simulation of isotropic permanent magnets

    Science.gov (United States)

    Bruckner, Florian; Abert, Claas; Vogler, Christoph; Heinrichs, Frank; Satz, Armin; Ausserlechner, Udo; Binder, Gernot; Koeck, Helmut; Suess, Dieter

    2016-03-01

    Accurate simulations of isotropic permanent magnets require to take the magnetization process into account and consider the anisotropic, nonlinear, and hysteretic material behaviour near the saturation configuration. An efficient method for the solution of the magnetostatic Maxwell equations including the description of isotropic permanent magnets is presented. The algorithm can easily be implemented on top of existing finite element methods and does not require a full characterization of the hysteresis of the magnetic material. Strayfield measurements of an isotropic permanent magnet and simulation results are in good agreement and highlight the importance of a proper description of the isotropic material.

  9. Macroscopic Simulation of Isotropic Permanent Magnets

    OpenAIRE

    Bruckner, Florian; Abert, Claas; Vogler, Christoph; Heinrichs, Frank; Satz, Armin; Ausserlechner, Udo; Binder, Gernot; Koeck, Helmut; Suess, Dieter

    2015-01-01

    Accurate simulations of isotropic permanent magnets require to take the magnetization process into account and consider the anisotropic, nonlinear, and hysteretic material behaviour near the saturation configuration. An efficient method for the solution of the magnetostatic Maxwell equations including the description of isotropic permanent magnets is presented. The algorithm can easily be implemented on top of existing finite element methods and does not require a full characterization of the...

  10. Macroscopic Quantum Coherence in Magnetic Molecular Clusters

    Institute of Scientific and Technical Information of China (English)

    JIN Yan-Hong; NIE Yi-Hang; LIANG Jiu-Qing; PU Fu-Cho

    2001-01-01

    The oscillation of tunnel splitting in Fes molecular clusters is obtained as a function of magnetic field applied along the hard axis by means of the instanton method with both semiclassical treatment and the effective potential field description of the quantum spin system. The theoretical splittings of the instanton method are compared with the numerical result by diagonalization of spin Hamiltonian operators and experimental observations. By taking the appropriate parameters, our theoretical formula yields a result the same as the experimental observation.

  11. A macroscopic description of coherent geo-magnetic radiation from cosmic-ray air showers

    NARCIS (Netherlands)

    Scholten, O.; Werner, K.; Rusydi, F.

    2008-01-01

    We have developed a macroscopic description of coherent electromagnetic radiation from air showers initiated by ultra-high-energy cosmic rays due to the presence of the geo-magnetic field. This description offers it simple and direct insight in the relation between the properties of the air shower a

  12. Nuclear magnetic resonance studies of macroscopic morphology and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Barrall, Geoffrey Alden [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-09-01

    Nuclear magnetic resonance techniques are traditionally used to study molecular level structure and dynamics with a noted exception in medically applied NMR imaging (MRI). In this work, new experimental methods and theory are presented relevant to the study of macroscopic morphology and dynamics using NMR field gradient techniques and solid state two-dimensional exchange NMR. The goal in this work is not to take some particular system and study it in great detail, rather it is to show the utility of a number of new and novel techniques using ideal systems primarily as a proof of principle. By taking advantage of the analogy between NMR imaging and diffraction, one may simplify the experiments necessary for characterizing the statistical properties of the sample morphology. For a sample composed of many small features, e.g. a porous medium, the NMR diffraction techniques take advantage of both the narrow spatial range and spatial isotropy of the sample`s density autocorrelation function to obtain high resolution structural information in considerably less time than that required by conventional NMR imaging approaches. The time savings of the technique indicates that NMR diffraction is capable of finer spatial resolution than conventional NMR imaging techniques. Radio frequency NMR imaging with a coaxial resonator represents the first use of cylindrically symmetric field gradients in imaging. The apparatus as built has achieved resolution at the micron level for water samples, and has the potential to be very useful in the imaging of circularly symmetric systems. The study of displacement probability densities in flow through a random porous medium has revealed the presence of features related to the interconnectedness of the void volumes. The pulsed gradient techniques used have proven successful at measuring flow properties for time and length scales considerably shorter than those studied by more conventional techniques.

  13. Witnessing Macroscopic Entanglement in a Staggered Magnetic Field

    CERN Document Server

    Hide, J; Son, W; Vedral, V; Hide, Jenny; Lawrie, Ian; Son, Wonmin; Vedral, Vlatko

    2007-01-01

    We investigate macroscopic entanglement in an infinite XX spin-1/2 chain with staggered magnetic field, $B_l=B+e^{-i\\pi l}b$. Using single-site entropy and by constructing an entanglement witness, we search for the existence of entanglement when the system is at absolute zero, as well as in thermal equilibrium. Although the role of the alternating magnetic field $b$ is, in general, to suppress entanglement as do $B$ and $T$, we find that when T=0, introducing $b$ allows the existence of entanglement even when the uniform magnetic field $B$ is arbitrarily large. We find that the region and the amount of entanglement in the spin chain can be enhanced by a staggered magnetic field.

  14. Statistical thermodynamics understanding the properties of macroscopic systems

    CERN Document Server

    Fai, Lukong Cornelius

    2012-01-01

    Basic Principles of Statistical PhysicsMicroscopic and Macroscopic Description of StatesBasic PostulatesGibbs Ergodic AssumptionGibbsian EnsemblesExperimental Basis of Statistical MechanicsDefinition of Expectation ValuesErgodic Principle and Expectation ValuesProperties of Distribution FunctionRelative Fluctuation of an Additive Macroscopic ParameterLiouville TheoremGibbs Microcanonical EnsembleMicrocanonical Distribution in Quantum MechanicsDensity MatrixDensity Matrix in Energy RepresentationEntropyThermodynamic FunctionsTemperatureAdiabatic ProcessesPressureThermodynamic IdentityLaws of Th

  15. Strain-induced macroscopic magnetic anisotropy from smectic liquid-crystalline elastomer-maghemite nanoparticle hybrid nanocomposites.

    Science.gov (United States)

    Haberl, Johannes M; Sánchez-Ferrer, Antoni; Mihut, Adriana M; Dietsch, Hervé; Hirt, Ann M; Mezzenga, Raffaele

    2013-06-21

    We combine tensile strength analysis and X-ray scattering experiments to establish a detailed understanding of the microstructural coupling between liquid-crystalline elastomer (LCE) networks and embedded magnetic core-shell ellipsoidal nanoparticles (NPs). We study the structural and magnetic re-organization at different deformations and NP loadings, and the associated shape and magnetic memory features. In the quantitative analysis of a stretching process, the effect of the incorporated NPs on the smectic LCE is found to be prominent during the reorientation of the smectic domains and the softening of the nanocomposite. Under deformation, the soft response of the nanocomposite material allows the organization of the nanoparticles to yield a permanent macroscopically anisotropic magnetic material. Independent of the particle loading, the shape-memory properties and the smectic phase of the LCEs are preserved. Detailed studies on the magnetic properties demonstrate that the collective ensemble of individual particles is responsible for the macroscopic magnetic features of the nanocomposite.

  16. Flagella bending affects macroscopic properties of bacterial suspensions

    Energy Technology Data Exchange (ETDEWEB)

    Potomkin, M.; Tournus, M.; Berlyand, L. V.; Aranson, I. S.

    2017-05-01

    To survive in harsh conditions, motile bacteria swim in complex environments and respond to the surrounding flow. Here, we develop a mathematical model describing how flagella bending affects macroscopic properties of bacterial suspensions. First, we show how the flagella bending contributes to the decrease in the effective viscosity observed in dilute suspension. Our results do not impose tumbling (random reorientation) as was previously done to explain the viscosity reduction. Second, we demonstrate how a bacterium escapes from wall entrapment due to the self-induced buckling of flagella. Our results shed light on the role of flexible bacterial flagella in interactions of bacteria with shear flow and walls or obstacles.

  17. Symmetry properties of macroscopic transport coefficients in porous media

    Science.gov (United States)

    Lasseux, D.; Valdés-Parada, F. J.

    2017-04-01

    We report on symmetry properties of tensorial effective transport coefficients characteristic of many transport phenomena in porous systems at the macroscopic scale. The effective coefficients in the macroscopic models (derived by upscaling (volume averaging) the governing equations at the underlying scale) are obtained from the solution of closure problems that allow passing the information from the lower to the upper scale. The symmetry properties of the macroscopic coefficients are identified from a formal analysis of the closure problems and this is illustrated for several different physical mechanisms, namely, one-phase flow in homogeneous porous media involving inertial effects, slip flow in the creeping regime, momentum transport in a fracture relying on the Reynolds model including slip effects, single-phase flow in heterogeneous porous media embedding a porous matrix and a clear fluid region, two-phase momentum transport in homogeneous porous media, as well as dispersive heat and mass transport. The results from the analysis of these study cases are summarized as follows. For inertial single-phase flow, the apparent permeability tensor is irreducibly decomposed into its symmetric (viscous) and skew-symmetric (inertial) parts; for creeping slip-flow, the apparent permeability tensor is not symmetric; for one-phase slightly compressible gas flow in the slip regime within a fracture, the effective transmissivity tensor is symmetric, a result that remains valid in the absence of slip; for creeping one-phase flow in heterogeneous media, the permeability tensor is symmetric; for two-phase flow, we found the dominant permeability tensors to be symmetric, whereas the coupling tensors do not exhibit any special symmetry property; finally for dispersive heat transfer, the thermal conductivity tensors include a symmetric and a skew-symmetric part, the latter being a consequence of convective transport only. A similar result is achieved for mass dispersion. Beyond the

  18. Properties of nuclear matter from macroscopic-microscopic mass formulas

    Science.gov (United States)

    Wang, Ning; Liu, Min; Ou, Li; Zhang, Yingxun

    2015-12-01

    Based on the standard Skyrme energy density functionals together with the extended Thomas-Fermi approach, the properties of symmetric and asymmetric nuclear matter represented in two macroscopic-microscopic mass formulas: Lublin-Strasbourg nuclear drop energy (LSD) formula and Weizsäcker-Skyrme (WS*) formula, are extracted through matching the energy per particle of finite nuclei. For LSD and WS*, the obtained incompressibility coefficients of symmetric nuclear matter are K∞ = 230 ± 11 MeV and 235 ± 11 MeV, respectively. The slope parameter of symmetry energy at saturation density is L = 41.6 ± 7.6 MeV for LSD and 51.5 ± 9.6 MeV for WS*, respectively, which is compatible with the liquid-drop analysis of Lattimer and Lim [4]. The density dependence of the mean-field isoscalar and isovector effective mass, and the neutron-proton effective masses splitting for neutron matter are simultaneously investigated. The results are generally consistent with those from the Skyrme Hartree-Fock-Bogoliubov calculations and nucleon optical potentials, and the standard deviations are large and increase rapidly with density. A better constraint for the effective mass is helpful to reduce uncertainties of the depth of the mean-field potential.

  19. Properties of nuclear matter from macroscopic-microscopic mass formulas

    CERN Document Server

    Wang, Ning; Ou, Li; Zhang, Yingxun

    2015-01-01

    Based on the standard Skyrme energy density functionals together with the extended Thomas-Fermi approach, the properties of symmetric and asymmetric nuclear matter represented in two macroscopic-microscopic mass formulas: Lublin-Strasbourg nuclear drop energy (LSD) formula and Weizs\\"acker-Skyrme (WS*) formula, are extracted through matching the energy per particle of finite nuclei. For LSD and WS*, the obtained incompressibility coefficients of symmetric nuclear matter are $K_\\infty=230 \\pm 11$ MeV and $235\\pm 11$ MeV, respectively. The slope parameter of symmetry energy at saturation density is $L=41.6\\pm 7.6$ MeV for LSD and $51.5\\pm 9.6$ MeV for WS*, respectively, which is compatible with the liquid-drop analysis of Lattimer and Lim [ApJ. \\textbf{771}, 51 (2013)]. The density dependence of the mean-field isoscalar and isovector effective mass, and the neutron-proton effective masses splitting for neutron matter are simultaneously investigated. The results are generally consistent with those from the Skyrm...

  20. Macroscopic motion of sheath-connected blobs in magnetic fields with arbitrary topology

    Science.gov (United States)

    Stepanenko, A. A.; Lee, W.; Krasheninnikov, S. I.

    2017-01-01

    In this study, macroscopic motion of sheath-connected blobs in magnetic fields, having arbitrary topology of the field lines and unfrozen in plasma, is analyzed within the electrostatic limit. Two distinct cases of magnetic configurations, with small and large curvature of the field lines, are considered and the criterion to discern them is deduced. For magnetic configurations with small curvature of the field lines, it is demonstrated that asymmetry of plasma distribution at the blob ends can drive macroscopic motion of a filament due to formation of unequal sheath potentials and establishing the effective Boltzmann potential. For a specific case of magnetic fields with small curvature of the field lines and identical metrics at the sheaths, we show that macroscopic motion of a plasma filament is determined by an effective electrostatic potential, which remains constant in time. For magnetic configurations with large curvature of the field lines, it is shown that motion of sufficiently large blobs is governed by integral distribution of plasma and magnetic field parameters along the field lines leading to blob adjusting its shape and position to the lead of the magnetic field lines in the course of its motion, whereas propagation of small and medium sized blobs can be represented as mutually independent motion of filament transverse cross-sections across the magnetic field lines. The qualitative conclusions on regularities of filament motion are supplied with numerical simulations of blob dynamics in two cases of tokamak-like magnetic fields with sheared and non-sheared field lines.

  1. Microstructure and macroscopic properties of polydisperse systems of hard spheres

    NARCIS (Netherlands)

    Ogarko, Vitaliy Anatolyevich

    2014-01-01

    This dissertation describes an investigation of systems of polydisperse smooth hard spheres. This includes the development of a fast contact detection algorithm for computer modelling, the development of macroscopic constitutive laws that are based on microscopic features such as the moments of the

  2. Microstructure and macroscopic properties of polydisperse systems of hard spheres

    NARCIS (Netherlands)

    Ogarko, V.

    2014-01-01

    This dissertation describes an investigation of systems of polydisperse smooth hard spheres. This includes the development of a fast contact detection algorithm for computer modelling, the development of macroscopic constitutive laws that are based on microscopic features such as the moments of the

  3. Macroscopic Quantum Phenomena and Topological Phase Interference Effects in Single-Domain Magnets

    Institute of Scientific and Technical Information of China (English)

    L(U) Rong; ZHU Jialin

    2001-01-01

    The tunneling of macroscopic object is one of the most fascinating phenomena in condensed matter physics.During the last decade,the problem of quantum tunneling of magnetization in nanometer-scale magnets has attracted a great deal of theoretical and experimental interest.A review of recent theoretical research of the macroscopic quantum phenomena in nanometer-scale single-domain magnets is presented in this paper.It includes macroscopic quantum tunneling (MQT) and coherence (MQC) in single-domain magnetic particles,the topological phase interference or spin-parity effects,and tunneling of magnetization in an arbitrarily directed magnetic field.The general formulas are shown to evaluate the tunneling rate and the tunneling level splitting for single-domain AFM particles.A nontrivial generalization of Kramers degeneracy for double-well system is provided to coherently spin tunneling for spin systems with m-fold rotational symmetry.The effects induced by the external magnetic field have been studied,where the field is along the easy,medium,hard axis,or arbitrary direction.

  4. Correlations between Nanoindentation Hardness and Macroscopic Mechanical Properties in DP980 Steels

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Mark D.; Choi, Kyoo Sil; Sun, Xin; Matlock, David K.; Packard, Corrine; Xu, Le; Barlat, Frederic

    2014-03-01

    Multiphase advanced high strength steels (AHSS) are being increasingly used in the automotive industry due to their low cost, good availability and excellent combination of strength and ductility. There is a keen interest from the automotive and steel industry for more fundamental understandings on the key microstructure features influencing the macroscopic properties, i.e., tensile properties, hole-expansion ratio and localized formability of AHSS. In this study, the micro- and macro-level properties for eight commercial DP980 steels are first characterized and quantified with various experimental methods. Correlations between macroscopic-level properties and relationships between various micro- and macro- properties for these steels are then established based on the experimental measurements. It is found that, despite their differences in their chemistry, processing parameters and sheet thickness, the eight DP980 steels do have common microstructural level properties governing their specific macroscopic properties in terms of strength, elongation and hole expansion performance.

  5. Quantum dynamics of a macroscopic magnet operating as an environment of a mechanical oscillator

    Science.gov (United States)

    Foti, C.; Cuccoli, A.; Verrucchi, P.

    2016-12-01

    We study the dynamics of a bipartite quantum system in a way such that its formal description keeps holding even if one of its parts becomes macroscopic; the problem is related to the analysis of the quantum-to-classical crossover, but our approach implies that the whole system stays genuinely quantum. The aim of the work is to understand (1) if, (2) to what extent, and possibly (3) how the evolution of a macroscopic environment testifies to the coupling with its microscopic quantum companion. To this purpose we consider a magnetic environment made of a large number of spin-1/2 particles, coupled with a quantum mechanical oscillator, possibly in the presence of an external magnetic field. We take the value of the total environmental spin S constant and large, which allows us to consider the environment as one single macroscopic system, and further deal with the hurdles of the spin-algebra via approximations that are valid in the large-S limit. We find an insightful expression for the propagator of the whole system, where we identify an effective "back-action" term, i.e., an operator acting on the magnetic environment only, and yet missing in the absence of the quantum principal system. This operator emerges as a time-dependent magnetic anisotropy whose character, whether uniaxial or planar, also depends on the detuning between the frequency of the oscillator and the level splitting in the spectrum of the free magnetic system, induced by the possible presence of the external field. The time dependence of the anisotropy is analyzed, and its effects on the dynamics of the magnet, as well as its relation to the entangling evolution of the overall system, are discussed.

  6. Magnetic studies of colossal magnetoresistance perovskites on macroscopic, mesoscopic and microscopic length scales

    Indian Academy of Sciences (India)

    S M Yusuf

    2004-07-01

    We have investigated magnetic correlations in various CMR manganites on macroscopic, mesoscopic and microscopic length scales by carrying out DC magnetization, neutron depolarization, and neutron diffraction measurements. We present here the effect of substituting Mn with Fe and La with Dy in the ferromagnetic La0.7- CaMnO3 ( ∼ 0.3 - 0.33) compounds. Neutron diffraction has been used in order to characterize the long-range magnetic order and its gradual suppression by the substitution. Neutron depolarization study has been carried out in order to bridge the gap in our understanding regarding the nature of magnetic correlation obtained from the macroscopic and microscopic measurements. In particular, our study on La0.67Ca0.33Mn0.9Fe0.1O3 has established the fact that a true double exchange mediated spin-glass is insulating. In another study of La-site ionic size effect and its disorder in (La1-Dy)0.7Ca0.3MnO3, we have investigated the evolution of the length scale of magnetic ordering with a possible microscopic explanation and the results have been compared with that for the light rare earth substituted compounds.

  7. Dynamic Chiral Magnetic Effect and Faraday Rotation in Macroscopically Disordered Helical Metals

    Science.gov (United States)

    Ma, J.; Pesin, D. A.

    2017-03-01

    We develop an effective medium theory for electromagnetic wave propagation through gapless nonuniform systems with a dynamic chiral magnetic effect. The theory allows us to calculate macroscopic-disorder-induced corrections to the values of optical, as well as chiral magnetic conductivities. In particular, we show that spatial fluctuations of the optical conductivity induce corrections to the effective value of the chiral magnetic conductivity. The absolute value of the effect varies strongly depending on the system parameters, but yields the leading frequency dependence of the polarization rotation and circular dichroism signals. Experimentally, these corrections can be observed as features in the Faraday rotation angle near frequencies that correspond to the bulk plasmon resonances of a material. Such features are not expected to be present in single-crystal samples.

  8. Correlation of macroscopic material properties with microscopic nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Simons, R.L.

    1981-12-18

    Two primary irradiation-induced changes occur during neutron irradiation: the displacement of atoms forming crystal defects and the transmutation of atoms into either gaseous or solid products. The material scientist studying irradiation damage to material by fusion-produced neutrons is faced with several questions: Is the nature of high-energy (14-MeV) displacement damage the same as or different from that caused by fission neutrons (< 2 MeV). How do the high helium concentrations expected in a fusion environment affect the material properties. What effects do solid transmutation products have on the behavior of the irradiated materials. In the past few years, much work has been done to answer these questions. This paper reviews recent work in this area.

  9. Studies of Dynamic, Radiative Macroscopic Magnetized HED Plasmas with Closed B-Field Lines

    Energy Technology Data Exchange (ETDEWEB)

    Frese, Michael H. [NumerEx, LLC, Albuquerque, NM (United States); Frese, Sherry D. [NumerEx, LLC, Albuquerque, NM (United States)

    2013-11-01

    The purpose of this research has been to study the physics of macroscopic magnetized high-energy-density laboratory plasmas (HEDLPs) created through the compression of a high-beta compact toroid (CT) plasma having closed magnetic field lines. The high-beta CT chosen for this work is a field-reversed configuration (FRC). The basic approach is to investigate CT plasmas as they are compressed to a HED state by the electromagnetic implosion of a surrounding metallic shell or solid liner (Figure 1). The shell provides an axisymmetric, electrically-conducting boundary around the plasma and its supporting magnetic field and is imploded by means of the magnetic pressure force arising from axial current flow in the liner interacting with its associated azimuthal magnetic field. Compression of the CT will bring the plasma to fusion temperatures at higher densities and magnetic fields (multi-MegaGauss [MG]) than have previously been present in conventional magnetic fusion approaches. The resulting energy densities will be ~1 Mbar or greater and thus will place the plasma in a parameter space intermediate to MFE and IFE. This work has been a collaboration between the Air Force Research Laboratory, Los Alamos National Laboratory, and NumerEx, LLC.

  10. Scaling Properties and Asymptotic Spectra of Finite Models of Phase Transitions as They Approach Macroscopic Limits

    Science.gov (United States)

    Rowe, D. J.; Turner, P. S.; Rosensteel, G.

    2004-11-01

    The asymptotic spectra and scaling properties of a mixed-symmetry Hamiltonian, which exhibits a second-order phase transition in its macroscopic limit, are examined for a system of N interacting bosons. A second interacting boson-model Hamiltonian, which exhibits a first-order phase transition, is also considered. The latter shows many parallel characteristics and some notable differences, leaving it open to question as to the nature of its asymptotic critical-point properties.

  11. The association between histological, macroscopic and magnetic resonance imaging assessed synovitis in end-stage knee osteoarthritis

    DEFF Research Database (Denmark)

    Riis, Robert Gabriel Coumine; Gudbergsen, Henrik; Simonsen, Ole

    2017-01-01

    OBJECTIVES: To investigate the association between magnetic resonance imaging (MRI), macroscopic and histological assessments of synovitis in end-stage knee osteoarthritis (KOA). METHODS: Synovitis of end-stage osteoarthritic knees was assessed using non-contrast-enhanced (CE), contrast-enhanced ......OBJECTIVES: To investigate the association between magnetic resonance imaging (MRI), macroscopic and histological assessments of synovitis in end-stage knee osteoarthritis (KOA). METHODS: Synovitis of end-stage osteoarthritic knees was assessed using non-contrast-enhanced (CE), contrast......-enhanced magnetic resonance imaging (CE-MRI) and dynamic contrast-enhanced (DCE)-MRI prior to (TKR) and correlated with microscopic and macroscopic assessments of synovitis obtained intraoperatively. Multiple bivariate correlations were used with a pre-specified threshold of 0.70 for significance. Also, multiple...

  12. Enhancement of magnetic coercivity and macroscopic quantum tunneling in monodispersed Co/CoO cluster assemblies

    OpenAIRE

    Peng, D. L.; Sumiyama, Kenji; Hihara, Takehiko; Yamamuro, S.; ヒハラ, タケヒコ; スミヤマ, ケンジ; 日原, 岳彦; 隅山, 兼治; Hihara, T.; Sumiyama, K.

    1999-01-01

    Magnetic properties have been measured for monodisperse-sized Co/CoO cluster assemblies prepared by a plasma-gas-condensation-type cluster beam deposition technique. The clear correlation obtained between exchange bias field and coercivity suggests the enhancement of uniaxial anisotropy owing to the exchange coupling between the ferromagnetic Co core and antiferromagnetic CoO shell, and magnetic disorder at the core-shell interface. A nonthermal magnetic relaxation observed below 8 K, being r...

  13. Sialic Acid-Responsive Polymeric Interface Material: From Molecular Recognition to Macroscopic Property Switching

    Science.gov (United States)

    Xiong, Yuting; Jiang, Ge; Li, Minmin; Qing, Guangyan; Li, Xiuling; Liang, Xinmiao; Sun, Taolei

    2017-01-01

    Biological systems that utilize multiple weak non-covalent interactions and hierarchical assemblies to achieve various bio-functions bring much inspiration for the design of artificial biomaterials. However, it remains a big challenge to correlate underlying biomolecule interactions with macroscopic level of materials, for example, recognizing such weak interaction, further transforming it into regulating material’s macroscopic property and contributing to some new bio-applications. Here we designed a novel smart polymer based on polyacrylamide (PAM) grafted with lactose units (PAM-g-lactose0.11), and reported carbohydrate-carbohydrate interaction (CCI)-promoted macroscopic properties switching on this smart polymer surface. Detailed investigations indicated that the binding of sialic acid molecules with the grafted lactose units via the CCIs induced conformational transformation of the polymer chains, further resulted in remarkable and reversible switching in surface topography, wettability and stiffness. With these excellent recognition and response capacities towards sialic acid, the PAM-g-lactose0.11 further facilitated good selectivity, strong anti-interference and high adsorption capacity in the capture of sialylated glycopeptides (important biomarkers for cancers). This work provides some enlightenment for the development of biointerface materials with tunable property, as well as high-performance glycopeptide enrichment materials. PMID:28084463

  14. Sialic Acid-Responsive Polymeric Interface Material: From Molecular Recognition to Macroscopic Property Switching

    Science.gov (United States)

    Xiong, Yuting; Jiang, Ge; Li, Minmin; Qing, Guangyan; Li, Xiuling; Liang, Xinmiao; Sun, Taolei

    2017-01-01

    Biological systems that utilize multiple weak non-covalent interactions and hierarchical assemblies to achieve various bio-functions bring much inspiration for the design of artificial biomaterials. However, it remains a big challenge to correlate underlying biomolecule interactions with macroscopic level of materials, for example, recognizing such weak interaction, further transforming it into regulating material’s macroscopic property and contributing to some new bio-applications. Here we designed a novel smart polymer based on polyacrylamide (PAM) grafted with lactose units (PAM-g-lactose0.11), and reported carbohydrate-carbohydrate interaction (CCI)-promoted macroscopic properties switching on this smart polymer surface. Detailed investigations indicated that the binding of sialic acid molecules with the grafted lactose units via the CCIs induced conformational transformation of the polymer chains, further resulted in remarkable and reversible switching in surface topography, wettability and stiffness. With these excellent recognition and response capacities towards sialic acid, the PAM-g-lactose0.11 further facilitated good selectivity, strong anti-interference and high adsorption capacity in the capture of sialylated glycopeptides (important biomarkers for cancers). This work provides some enlightenment for the development of biointerface materials with tunable property, as well as high-performance glycopeptide enrichment materials.

  15. Stress dependent vector magnetic properties in electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Ktena, Aphrodite, E-mail: aktena@teihal.gr [Department of Electrical Engineering, TEI of Chalkida, Psachna, Evia 34400 (Greece); Davino, Daniele; Visone, Ciro [Engineering Department, University of Sannio (Italy); Hristoforou, Evangelos [Laboratory of Metallurgy, National Technical University of Athens (Greece)

    2014-02-15

    The dependence of macroscopic magnetic properties on applied and residual stresses is promising for development of new magnetic non-destructive evaluation techniques in ferrous materials. The reliability of AC magnetometry, in determining the effect of strain on magnetic macroscopic parameters, is evaluated against scalar and vector Vibrating Sample Magnetometer measurements on strained electrical steel samples after unloading. Hysteresis loops have been measured at 0°, 30°, 45°, 60° and 90° to the direction of the applied stress. Vector magnetic properties reveal a stress-related anisotropy component, which increases with strain and deteriorates after fracture. The effect of residual stress on the saturation and remanent magnetization, as well as the differential susceptibility, is discussed with respect to data from AC magnetometry at 0.1 Hz. The results of the latter are representative of the magnetic configuration of the material under test and make it a promising candidate for NDE applications in steels.

  16. CH-π Interaction Driven Macroscopic Property Transition on Smart Polymer Surface

    Science.gov (United States)

    Li, Minmin; Qing, Guangyan; Xiong, Yuting; Lai, Yuekun; Sun, Taolei

    2015-10-01

    Life systems have evolved to utilize weak noncovalent interactions, particularly CH-π interaction, to achieve various biofunctions, for example cellular communication, immune response, and protein folding. However, for artificial materials, it remains a great challenge to recognize such weak interaction, further transform it into tunable macroscopic properties and realize special functions. Here we integrate monosaccharide-based CH-π receptor capable of recognizing aromatic peptides into a smart polymer with three-component “Recognition-Mediating-Function” design, and report the CH-π interaction driven surface property switching on smart polymer film, including wettability, adhesion, viscoelasticity and stiffness. Detailed studies indicate that, the CH-π interaction induces the complexation between saccharide unit and aromatic peptide, which breaks the initial amphiphilic balance of the polymer network, resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties. This work not only presents a new approach to control the surface property of materials, but also points to a broader research prospect on CH-π interaction at a macroscopic level.

  17. CH-π Interaction Driven Macroscopic Property Transition on Smart Polymer Surface.

    Science.gov (United States)

    Li, Minmin; Qing, Guangyan; Xiong, Yuting; Lai, Yuekun; Sun, Taolei

    2015-10-29

    Life systems have evolved to utilize weak noncovalent interactions, particularly CH-π interaction, to achieve various biofunctions, for example cellular communication, immune response, and protein folding. However, for artificial materials, it remains a great challenge to recognize such weak interaction, further transform it into tunable macroscopic properties and realize special functions. Here we integrate monosaccharide-based CH-π receptor capable of recognizing aromatic peptides into a smart polymer with three-component "Recognition-Mediating-Function" design, and report the CH-π interaction driven surface property switching on smart polymer film, including wettability, adhesion, viscoelasticity and stiffness. Detailed studies indicate that, the CH-π interaction induces the complexation between saccharide unit and aromatic peptide, which breaks the initial amphiphilic balance of the polymer network, resulting in contraction-swelling conformational transition for polymer chains and subsequent dramatic switching in surface properties. This work not only presents a new approach to control the surface property of materials, but also points to a broader research prospect on CH-π interaction at a macroscopic level.

  18. Ground State Properties of Superheavy Nuclei in Macroscopic-Microscopic Model

    Institute of Scientific and Technical Information of China (English)

    ZHI Qi-Jun; REN Zhong-Zhou; ZHANG Xiao-Ping; ZHENG Qiang

    2008-01-01

    The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential The calculations well produced the ground state binding energies,a-decay energies,and half lives of superheavy nuclei.The calculated results are systematically compared with available experimental data.The calculated results are also compared with theoretical results from other MM models and from relativistic mean-field model.The calculations and comparisons show that the MM model is reliable in superheavy region and that the MM model results are not very sensitive to the choice of microscopic single-particle potential.

  19. Macroscopic Properties of Restacked, Redox-Liquid Exfoliated Graphite and Graphite Mimics Produced in Bulk Quantities

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Vikram K [ORNL; Quinlan, Ronald [ORNL; Agapov, Alexander L [ORNL; Dunlap, John R [ORNL; Nelson, Kimberly M [ORNL; Duranty, Edward R [ORNL; Sokolov, Alexei P [ORNL; Bhat, Gajanan [ORNL; Mays, Jimmy [ORNL

    2014-01-01

    The excellent properties exhibited by monolayer graphene have spurred the development of exfoliation techniques using bulk graphite to produce large quantities of pristine monolayer sheets. Development of simple chemistry to exfoliate and intercalate graphite and graphite mimics in large quantities is required for numerous applications. To determine the macroscopic behavior of restacked, exfoliated bulk materials, a systematic approach is presented using a simple, redox-liquid sonication process along to obtain large quantities of 2D and 3D hexagonally layered graphite, molybdenum disulfi de, and boron nitride, which are subsequently characterized to observe chemical and structural changes. For MoS 2 sonicated with the antioxidant sodium bisulfi te, results from Raman spectroscopy, X-ray diffraction, and electron microscopy indicate the presence of distorted phases from different polymorphs, and apparent nanotube structures in the bulk, restacked powder. Furthermore, using thermograviemtric analysis, the antioxidant enhances the resistance to oxidative degradation of MoS 2 , upon thermal treatment up to 900 C. The addition of the ionic antioxidant decreased dispersion stability in non-polar solvent, suggesting decreased compatibility with non-polar systems. Using simple chemical methods, the ability to generate tailored multidimensional layered materials with unique macroscopic properties is critical for numerous applications, including electrical devices, reinforced polymer composites, lithium ion capacitors, and chemical sensing.

  20. Macroscopic-microscopic calculations of ground state properties of superheavy nuclei

    Institute of Scientific and Technical Information of China (English)

    ZHI Qi-jun; Mao Ying-chen; REN Zhong-zhou

    2006-01-01

    We systematically calculate the ground state properties of superheavy even-even nuclei with proton number Z=94-118.The calculations are based on the liquid drop macroscopic model and the microscopic model with the modified single-particle oscillator potential. The calculated binding energies and α-decay energies agree well with the experimental data.The reliability of the macroscopic-microscopic(MM)model for superheavy nuclei is confirmed by the good agreement between calculated results and experimental ones. Detailed comparisons between our calculations and M(o)ller's are made.It is found that the calculated results also agree with M(o)ller's results and that the MM model is insensitive to the microscopic single-particle potential. Calculated results are also compared with results from relativistic mean-field (RMF)model and from Skyrme-Hatree-Fock(SHF) model.In addition,half-lives,deformations and shape coexistence are also investigated.The properties of some unknown nuclei are predicted and they will be useful for future experimental researches of superheavy nuclei.

  1. MAGNETIC WOVEN FABRICS - PHYSICAL AND MAGNETIC PROPERTIES

    Directory of Open Access Journals (Sweden)

    GROSU Marian C

    2015-05-01

    Full Text Available A coated material is a composite structure that consists of at least two components: base material and coating layer. The purpose of coating is to provide special properties to base material, with potential to be applied in EMI shielding and diverse smart technical fields. This paper reports the results of a study about some physical and magnetic properties of coated woven fabrics made from cotton yarns with fineness of 17 metric count. For this aim, a plain woven fabric was coated with a solution hard magnetic polymer based. As hard magnetic powder, barium hexaferrite (BaFe12O19 was selected. The plain woven fabric used as base has been coated with five solutions having different amounts of hard magnetic powder (15% - 45% in order to obtain five different magnetic woven fabrics. A comparison of physical properties regarding weight (g/m2, thickness (mm, degree of charging (% and magnetic properties of magnetic woven samples were presented. Saturation magnetizing (emu/g, residual magnetizing (emu/g and coercive force (kA/m of pure hard magnetic powder and woven fabrics have been studied as hysteresis characteristics. The magnetic properties of the woven fabrics depend on the mass percentage of magnetic powder from coating solution. Also, the residual magnetism and coercive field of woven fabrics represents only a part of bulk barium hexafferite residual magnetism and coercive field.

  2. Enhancing the magnetic properties of magnetic nanoparticles

    DEFF Research Database (Denmark)

    Ahlburg, Jakob; Saura-Múzquiz, Matilde; Stingaciu, Marian

    ways of enhancing magnetic properties of 3d magnetic compounds. This includes, size control, core-shell particles or mixing hard and soft magnetic materials together to achieve an exchange coupling between the compounds and enhancing the magnetic energy product. In order to control the particle size......Enhancing the magnetic properties of magnetic nanoparticles J. V. Ahlburg, M. S. Músquiz, C. Zeuthen, S. Kjeldgaard, M. Stingaciu, M. Christensen Center for Materials Crystallography, Departement of Chemistry & iNano, Aarhus University, Denmark Strong magnets with a high energy product are vital...... when optimizing the efficiency in the electric industry. But since the rare earth metals, normally used for making strong permanent magnets, are both expensive and difficult to mine, a great demand has come to cheaper types of magnets with a similar magnetic performance. There are several different...

  3. Long-term creep properties of cementitious materials: Comparing microindentation testing with macroscopic uniaxial compressive testing

    OpenAIRE

    Zhang, Qing; Le Roy, Robert; VANDAMME, Mathieu; ZUBER, Bruno

    2014-01-01

    This study is dedicated to comparing minutes-long microindentation creep experiments on cement paste with years-long macroscopic creep experiments on concrete and months-long macroscopic creep experiments on cement paste. For all experiments, after a transient period the creep function was well captured by a logarithmic function of time, the amplitude of which is governed by a so-called creep modulus. The non-logarithmic transient periods lasted for days at the macroscopic scale, but only for...

  4. Enhancing the magnetic properties of magnetic nanoparticles

    DEFF Research Database (Denmark)

    Ahlburg, Jakob; Saura-Múzquiz, Matilde; Stingaciu, Marian

    with a similar magnetic performance. There are several different ways of enhancing magnetic properties of 3d magnetic compounds. This includes, size control, core-shell particles or mixing hard and soft magnetic materials together to achieve an exchange coupling between the compounds and enhancing the magnetic......Strong magnets with a high energy product are vital when optimizing the efficiency in the electric industry. But since the rare earth metals, normally used for making strong permanent magnets, are both expensive and difficult to mine, a great demand has come to cheaper types of magnets...... energy product. In order to control the particle size, a hydrothermal synthesis is preferred. This followed by reduction or the oxides into either core shell particles, or a mixture of magnetic oxides and a metallic phase....

  5. Nanocomposites fabrication by self-assembly method to modify macroscopic properties

    Science.gov (United States)

    Lopez-Barbosa, N.; Osma, J. F.

    2017-01-01

    Polymeric nanocomposites have been in the scope of scientists for the last decade due to their multiple applications and simple synthesis. Self-assembly fabrication can be performed through different methods such as layer-by-layer or the controlled growth of nanostructures on a surface. These methods allow fast elaboration of nanocomposites that can be readily integrated in sensors or films. The current work exposes the self-assembly of nanocomposites for the modification of material’s macroscopic properties such as hydrophobicity and temperature’s resistance on textiles. Hydrophobicity properties of cotton textiles were modified by the application of functionalized silica nanoparticles on their surfaces. Thermal resistance of cotton textiles was achieved by incorporating TiO2 nanoparticles into the matrix, increasing the scope of their applications. Functionalization was attained by chloro-trimethyl-silane (CTS) and γ-amino(propyl) triethoxy silane (APTES) in organic and inorganic solvents. Wetting phenomena characteristics appeared to highly depend on the synthesis parameters.

  6. Aharonov-Casher-effect suppression of macroscopic tunneling of magnetic flux.

    Science.gov (United States)

    Friedman, Jonathan R; Averin, D V

    2002-02-04

    We suggest a system in which the amplitude of macroscopic flux tunneling can be modulated via the Aharonov-Casher effect. The system is an rf SQUID with the Josephson junction replaced by a Bloch transistor--two junctions separated by a small superconducting island on which the charge can be induced by an external gate voltage. When the Josephson coupling energies of the junctions are equal and the induced charge is q = e, destructive interference between tunneling paths brings the flux tunneling rate to zero. The device may also be useful as a qubit for quantum computation.

  7. Improving the specificity of R2' to the deoxyhaemoglobin content of brain tissue: Prospective correction of macroscopic magnetic field gradients.

    Science.gov (United States)

    Blockley, Nicholas P; Stone, Alan J

    2016-07-15

    The reversible transverse relaxation rate, R2', is sensitive to the deoxyhaemoglobin content of brain tissue, enabling information about the oxygen extraction fraction to be obtained. However, R2' is also sensitive to macroscopic magnetic field gradients, particularly at air-tissue interfaces where a large susceptibility difference is present. It is important that this latter effect is minimised in order to produce meaningful estimates of blood oxygenation. Therefore, the aim of this study was to implement a technique to prospectively correct for the effect of susceptibility induced magnetic field gradients on R2' weighted data. This was achieved by combining the Gradient-Echo Slice Excitation Profile Imaging (GESEPI) technique with an Asymmetric Spin Echo (ASE) pulse sequence. The main advantages of this approach are (i) shorter acquisition times, since a separately acquired magnetic field map is not required and (ii) simpler analysis, since retrospective correction for the effects of magnetic field gradients in postprocessing is not required. In these experiments we show that with this newly developed technique it is possible to correct the majority of grey matter voxels for the expected distribution of through-slice magnetic field gradients to produce maps of R2' in a short scan duration.

  8. Macroscopic Properties of Hollow Cone Spray Using an Outwardly Opening Piezoelectric Injector in GCI Engine

    KAUST Repository

    Cheng, Penghui

    2016-07-01

    Fuel mixture formation and spray characteristics are crucial for the advancement of Gasoline Compression Ignition (GCI) engine. For investigations of spray characteristics, a high-pressure high-temperature spray chamber with constant volume has been designed, tested and commissioned at CCRC, KAUST. Back light illumination technique has been applied to investigate the macroscopic spray properties of an outwardly opening piezoelec- tric injector. Three parameters including injection pressure, ambient pressure, and ambient temperature have been involved. A total of 18 combinations of experimental conditions were tested under non-reactive conditions. Through qualitative analysis of spray morphology under different operating conditions, an apparent distinction of spray morphology has been noticed. Spray morphology and propagation have shown strong dependencies on ambient pressure and ambient tempera- ture while injection pressure has a negligible effect on spray shape. Increasingly compact and bushier spray patterns were observed in the cases of high ambient pressure due to in- creasing aerodynamic drag force on spray boundary. It should also be noted that ambient temperature plays a fairly important role in fuel evaporation rate. At 200 °C, oscillating and considerably short spray shape was produced. Also, circumferential ring-like vortices and distinctive string-like structures have been identified for the fuel spray exiting this hollow cone injector. It has been observed that high ambient pressure conditions (Pamb = 4 bar and 10.5 bar) are favorable to the vortices generation, which has also been reported in previous literature. The quantitative description of macroscopic spray properties reveals that ambient pres- sure and ambient temperature are found to be the most influential parameters on liquid penetration length. The rise of ambient pressure results in considerably shorter liquid pen- etration length. Ambient temperature also appears to be a very effective

  9. Macroscopic fields in thin ferromagnetic sheets taking into account eddy currents and Landau-Lifshitz magnetization

    Science.gov (United States)

    Dupré, Luc; Olyslager, Frank; Melkebeek, Jan

    2004-05-01

    The paper deals with a numerical model for the evaluation of the electromagnetic behavior in thin magnetic sheets. Therefore, we consider Maxwell's equations together with a nonlinear magnetic constitutive law described by the Landau-Lifshitz equation. We present a suitable numerical approximation based upon a finite element-finite difference method. At each time step in the numerical scheme, the magnetization dynamics is calculated analytically by introducing for each finite element node a transformation towards a local coordinate system.

  10. Effect of microscopic disorder on magnetic properties of metamaterials.

    Science.gov (United States)

    Gorkunov, Maxim V; Gredeskul, Sergey A; Shadrivov, Ilya V; Kivshar, Yuri S

    2006-05-01

    We analyze the effect of microscopic disorder on the macroscopic properties of composite metamaterials and study how weak statistically independent fluctuations of the parameters of the structure elements can modify their collective magnetic response and left-handed properties. We demonstrate that even a weak microscopic disorder may lead to a substantial modification of the metamaterial magnetic properties, and a 10% deviation in the parameters of the microscopic resonant elements may lead to a substantial suppression of the wave propagation in a wide frequency range. A noticeable suppression occurs also if more than 10% of the resonant magnetic elements possess strongly different properties, and in the latter case the defects can create an additional weak resonant line. These results are of a key importance for characterizing and optimizing novel composite metamaterials with the left-handed properties at terahertz and optical frequencies.

  11. Macroscopic and microscopic spectral properties of brain networks during local and global synchronization

    NARCIS (Netherlands)

    Maksimenko, V.A.; Lüttjohann, A.; Makarov, V.V.; Goremyko, M.V.; Koronovskii, A.A.; Nedaivozov, V.; Runnova, A.E.; Luijtelaar, E.L.J.M. van; Hramov, A.E.; Boccaletti, S.

    2017-01-01

    We introduce a practical and computationally not demanding technique for inferring interactions at various microscopic levels between the units of a network from the measurements and the processing of macroscopic signals. Starting from a network model of Kuramoto phase oscillators which evolve

  12. MACROSCOPIC RIVERS

    NARCIS (Netherlands)

    VANDENBERG, IP

    1991-01-01

    We present a mathematical model for the ''river-phenomenon'': striking concentrations of trajectories of ordinary differential equations. This model of ''macroscopic rivers'' is formulated within nonstandard analysis, and stated in terms of macroscopes and singular perturbations. For a subclass, the

  13. Influence of macroscopic graphite particulates on the damping properties of Zn-Al eutectoid alloy

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The paper presents in detail the effects of macroscopic graphite (Gr) particulates on the damping behavior of Zn-Al eutectoid alloy (Zn-Al). Macroscopic defects are graphite particulates with sizes of the order of a millimeter (0.5 mm and 1.0 mm). Macroscopic graphite particulate-reinforced Zn-Al eutectoid alloys were prepared by the air pressure infiltration process. The damping characterization was conducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at different frequencies over the temperature range of 20 to 400℃. The damping capacity of the Zn-Al/Gr, with two different volume fractions of macroscopic graphite particulates, was compared with that of bulk Zn-Al eutectoid alloy. The damping capacity of the materials is shown to increase with increasing volume fraction of macroscopic graphite particulates. Two IF peaks were found in the IF-temperature curves. The first is a grain boundary peak, which is associated with the diffusive flux on a boundary between like phases, Al/Al. Its activation energy has been calculated to be 1.13±0.03 eV and the pre-exponential factor is 10?14 s in IF measurements. The second is a phase transition peak, which results from the transformation of Zn-Al eutectoid. In light of internal friction measurements and differential scanning calorimetry (DSC) experiments, its activation energy has been calculated to be 2.36±0.08 eV.

  14. Influence of macroscopic graphite particulates on the damping properties of Zn-Al eutectoid alloy

    Institute of Scientific and Technical Information of China (English)

    WEI JianNing; SONG ShiHua; HU KongGang; XIE WeiJun; MA MingLiang; LI GenMei

    2009-01-01

    The paper presents in detail the effects of macroscopic graphite (Gr) particulates on the damping be-havior of Zn-AI eutectoid alloy (Zn-AI). Macroscopic defects are graphite particulates with sizes of the order of a millimeter (0.5 mm and 1.0 mm). Macroscopic graphite particulate-reinforced Zn-AI eutectoid alloys were prepared by the air pressure infiltration process. The damping characterization was con-ducted on a multifunction internal friction apparatus (MFIFA). The internal friction (IF), as well as the relative dynamic modulus, was measured at different frequencies over the temperature range of 20 to 400"C. The damping capacity of the Zn-AI/Gr, with two different volume fractions of macroscopic graphite particulates, was compared with that of bulk Zn-Al eutectoid alloy. The damping capacity of the materials is shown to increase with increasing volume fraction of macroscopic graphite particulates. Two IF peaks were found in the IF-temperature curves. The first is a grain boundary peak, which is as-sociated with the diffusive flux on a boundary between like phases, Al/Al. Its activation energy has been calculated to be 1.13±0.03 eV and the pre-exponential factor is 10-14 s in IF measurements. The second is a phase transition peak, which results from the transformation of Zn-AI eutectoid. In light of internal friction measurements and differential scanning calorimetry (DSC) experiments, its activation energy has been calculated to be 2.36±0.08 eV.

  15. Quantification of synovistis by MRI: correlation between dynamic and static gadolinium-enhanced magnetic resonance imaging and microscopic and macroscopic signs of synovial inflammation

    DEFF Research Database (Denmark)

    Østergaard, Mikkel; Stoltenberg, M; Løvgreen-Nielsen, P;

    1998-01-01

    Dynamic and static gadolinium-diethylenetriaminepentaacetic acid(Gd-DTPA)-enhanced magnetic resonance imaging (MRI) were evaluated as measures of joint inflammation in arthritis, by a comparison with macroscopic and microscopic signs of synovitis. Furthermore, the importance of the size of the ev......Dynamic and static gadolinium-diethylenetriaminepentaacetic acid(Gd-DTPA)-enhanced magnetic resonance imaging (MRI) were evaluated as measures of joint inflammation in arthritis, by a comparison with macroscopic and microscopic signs of synovitis. Furthermore, the importance of the size...

  16. Effect of surface energy of solid surfaces on the micro- and macroscopic properties of adsorbed BSA and lysozyme.

    Science.gov (United States)

    Sharma, Indu; Pattanayek, Sudip K

    2017-07-01

    The surface energy, a macroscopic property, depends on the chemical functionality and micro- and macroscopic roughness of the surface. The adsorption of two widely used proteins bovine serum albumin (BSA) and lysozyme on surfaces of four different chemical functionalities were done to find out the interrelation between macroscopic and microscopic properties. We have observed the secondary structure of protein after its adsorption. In addition, we observed the variation of surface energy of proteins due to variation in adsorption time, change in protein concentration and effect of a mixture of proteins. Surfaces of three different chemical functionalities namely, amine, hydroxyl and octyl were obtained through self-assembled monolayer on silica surfaces and were tested for responses towards adsorption of lysozyme and BSA. The adsorbed lysozyme has higher surface energy than the adsorbed BSA on amine and octyl surfaces. On hydroxyl functional surface, the surface energy due to the adsorbed lysozyme or BSA increases slowly with time. The surface energy of the adsorbed protein increases gradually with increasing protein concentration on hydrophobic surfaces. On hydrophilic surfaces, with increasing BSA concentration in bulk solution, the surface energy of the adsorbed protein on GPTMS and amine surfaces is maximum at 1μM concentration. During the adsorption from a mixture of BSA and lysozyme on octyl surface, first lysozyme adsorbs and subsequent BSA adsorption leads to a high surface energy. Copyright © 2016. Published by Elsevier B.V.

  17. Chemical Ordering Modulated Electronic Phase Separation and Macroscopic Properties in Colossal Magnetoresistance Manganites

    Science.gov (United States)

    Zhu, Yinyan; Du, Kai; Yin, Lifeng; Shen, Jian; Low-dimensional material physics Team

    Using unit cell by unit cell superlattice growth technique, we determine the role of chemical ordering of the Pr dopant in a colossal magnetoresistance (La1-yPry)1-x CaxMnO3 (LPCMO) system, which has been well known for its large length scale electronic phase separation (EPS) phenomena. Our experimental results show that the chemical ordering of Pr leads to dramatic reduction of the length scale of EPS. Moreover, compared to the conventional Pr-disordered LPCMO system, the Pr-ordered LPCMO system has ~100 K higher metal-insulator transition temperature. We have further investigated the n-dependence of the physical properties of the (LCMO)2n/(PCMO)n superlattices. Magnetic and transport measurements indicate that the physical properties change nonmonotonically with increasing n, reaching a minimum for both the Curie temperature and the meta-insulator transition temperature. The crossover thickness thus reflects the characteristic correlation length scale along the vertical direction of the superlattice. For superlattices with n smaller than the correlation length, we combine MFM studies and model calculations to explain the weakened ferromagnetism and metallicity with increasing n.

  18. Micro-finite-element method to assess elastic properties of trabecular bone at micro- and macroscopic level.

    Science.gov (United States)

    Rieger, R; Auregan, J C; Hoc, T

    2017-09-08

    The objective of the present study is to assess the mechanical behavior of trabecular bone based on microCT imaging and micro-finite-element analysis. In this way two methods are detailed: (i) direct determination of macroscopic elastic property of trabecular bone; (ii) inverse approach to assess mechanical properties of trabecular bone tissue. Thirty-five females and seven males (forty-two subjects) mean aged (±SD) 80±11.7 years from hospitals of Assistance publique-Hôpitaux de Paris (AP-HP) diagnosed with osteoporosis following a femoral neck fracture due to a fall from standing were included in this study. Fractured heads were collected during hip replacement surgery. Standardized bone cores were removed from the femoral head's equator by a trephine in a water bath. MicroCT images acquisition and analysis were performed with CTan(®) software and bone volume fraction was then determined. Micro-finite-element simulations were per-formed using Abaqus 6.9-2(®) software in order to determine the macroscopic mechanical behaviour of the trabecular bone. After microCT acquisition, a longitudinal compression test was performed and the experimental macroscopic Young's Modulus was extracted. An inverse approach based on the whole trabecular bone's mechanical response and micro-finite-element analysis was performed to determine microscopic mechanical properties of trabecular bone. In the present study, elasticity of the tissue was shown to be similar to that of healthy tissue but with a lower yield stress. Classical histomorphometric analysis form microCT imaging associated with an inverse micro-finite-element method allowed to assess microscopic mechanical trabecular bone parameters. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  19. Macroscopic and microscopic spectral properties of brain networks during local and global synchronization

    Science.gov (United States)

    Maksimenko, Vladimir A.; Lüttjohann, Annika; Makarov, Vladimir V.; Goremyko, Mikhail V.; Koronovskii, Alexey A.; Nedaivozov, Vladimir; Runnova, Anastasia E.; van Luijtelaar, Gilles; Hramov, Alexander E.; Boccaletti, Stefano

    2017-07-01

    We introduce a practical and computationally not demanding technique for inferring interactions at various microscopic levels between the units of a network from the measurements and the processing of macroscopic signals. Starting from a network model of Kuramoto phase oscillators, which evolve adaptively according to homophilic and homeostatic adaptive principles, we give evidence that the increase of synchronization within groups of nodes (and the corresponding formation of synchronous clusters) causes also the defragmentation of the wavelet energy spectrum of the macroscopic signal. Our methodology is then applied to getting a glance into the microscopic interactions occurring in a neurophysiological system, namely, in the thalamocortical neural network of an epileptic brain of a rat, where the group electrical activity is registered by means of multichannel EEG. We demonstrate that it is possible to infer the degree of interaction between the interconnected regions of the brain during different types of brain activities and to estimate the regions' participation in the generation of the different levels of consciousness.

  20. Fission-fragment and neutron data traced back to the macroscopic and microscopic properties of the fissioning systems

    Directory of Open Access Journals (Sweden)

    Schmidt K.-H.

    2010-10-01

    Full Text Available A new model description of fission-fragment yields and prompt neutron emission is developed. The yields of the different fission channels and their properties are attributed to the number of relevant states above the potential-energy landscape on the fission path at the moment of dynamical freeze-out, which is specific to the collective coordinate considered. The model combines well established ideas with novel concepts. The separability principle of macroscopic properties of the compound nucleus and microscopic properties of the fragments strongly reduces the number of model parameters and assures a high predictive power. The recently discovered energy-sorting mechanism in superfluid nuclear dynamics determines the sharing of intrinsic excitation energy at scission and the enhancement of even-odd structure in asymmetric splits.

  1. Magnetic properties of hematite nanoparticles

    DEFF Research Database (Denmark)

    Bødker, Franz; Hansen, Mikkel Fougt; Bender Koch, Christian

    2000-01-01

    The magnetic properties of hematite (alpha-Fe2O3) particles with sizes of about 16 nm have been studied by use of Mossbauer spectroscopy, magnetization measurements, and neutron diffraction. The nanoparticles are weakly ferromagnetic at temperatures at least down to 5 K with a spontaneous...... magnetization that is only slightly higher than that of weakly ferromagnetic bulk hematite. At T greater than or similar to 100 K the Mossbauer spectra contain a doublet, which is asymmetric due to magnetic relaxation in the presence of an electric field gradient in accordance with the Blume-Tjon model......, Simultaneous fitting of series of Mossbauer spectra obtained at temperatures from 5 K to well above the superparamagnetic blocking temperature allowed the estimation of the pre-exponential factor in Neel's expression for the superparamagnetic relaxation time, tau(0) = (6 +/- 4) X 10(-11) s and the magnetic...

  2. Magnetic properties in the inhomogeneous chiral phase

    CERN Document Server

    Yoshiike, Ryo; Tatsumi, Toshitaka

    2016-01-01

    We investigate the magnetic properties of quark matter in the inhomogeneous chiral phase, where both scalar and pseudoscalar condensates spatially modulate. The energy spectrum of the lowest Landau level becomes asymmetric about zero in the external magnetic field, and gives rise to the remarkably magnetic properties: quark matter has a spontaneous magnetization, while the magnetic susceptibility does not diverge on the critical point.

  3. Magnetic Properties and Intergranular Action in Bonded Hybrid Magnets

    Institute of Scientific and Technical Information of China (English)

    Hua Zhenghe; Li Shandong; Han Zhida; Wang Dunhui; Zhong Wei; Gu Benxi; Lu Mu; Zhang Jianrong; Du Youwei

    2007-01-01

    Magnetic properties and intergranular action in bonded hybrid magnets, based on NdFeB and strontium ferrite powders were investigated. The long-range magnetostatic interaction and short-range exchange coupling interaction existed simultaneously in bonded hybrid magnets, and neither of them could be neglected. Some magnetic property parameters of hybrid magnets could be approximately obtained by adding the hysteresis loops of two magnets pro rata.

  4. Field diffusion-like representation and experimental identification of a dynamic magnetization property

    Energy Technology Data Exchange (ETDEWEB)

    Maloberti, Olivier [LEG-INPG/UJF-CNRS UMR 5529: BP 46, 38402 Saint Martin d' Heres cedex (France) and Schneider Electric Corporate Research and Developments, 37 quai Paul Louis Merlin, 38050 Grenoble cedex 9 (France)]. E-mail: olivier.maloberti@schneider-electric.com; Kedous-Lebouc, A. [LEG-INPG/UJF-CNRS UMR 5529: BP 46, 38402 Saint Martin d' Heres cedex (France); Geoffroy, O. [LLN-UJF/INPG-CNRS UPR 5051: 25 avenue des Martyrs, 38050 Grenoble cedex 9 (France); Meunier, G. [LEG-INPG/UJF-CNRS UMR 5529: BP 46, 38402 Saint Martin d' Heres cedex (France); Mazauric, V. [Schneider Electric Corporate Research and Developments, 37 quai Paul Louis Merlin, 38050 Grenoble cedex 9 (France)

    2006-09-15

    So as to fuse dynamic magnetization properties of soft materials with the electromagnetism theory, we investigate the inclusion of microscopic reversal processes related to domains and walls in macroscopic Maxwell equations. We first introduce a model for independent walls and the unidirectional motion mechanism; then we characterize one sample with measurements and analytical calculations in case of one-dimensional linear problems.

  5. Magnetic Properties of Erbium Gallium Gallate under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    Zhang Xijuan; Cheng Haiying; Yang Cuihong; Wang Wei

    2004-01-01

    A theoretical investigation on the magnetic properties of rare-earth Er3+ in Er3 Ga5 O12 was reported. The average magnetic moments(M) for applied magnetic field H parallel to the [001 ], [ 100], [ 110], [ 111 ] direction was studied based on the quantum theory. Temperature dependence of the magnetic properties is analyzed for H applied parallel to the [ 100] and [ 111 ] crystallographic directions. The magnetization decreases with increasing temperature,showing good agreement with thermal effect. A strong anisotropy of the magnetization is found under high magnetic field, but when the magnetic field is small, M and H are proportional.

  6. Electronic structure and magnetic properties of solids

    Science.gov (United States)

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

    2005-05-01

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

  7. Electronic structure and magnetic properties of solids

    OpenAIRE

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

    2005-01-01

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

  8. Magnetic Cluster States in Nanostructured Materials

    Energy Technology Data Exchange (ETDEWEB)

    Diandra Leslie-Pelecky

    2008-06-13

    The goal of this work is to fabricate model nanomaterials with different types of disorder and use atomic-scale characterization and macroscopic magnetization measurements to understand better how specific types of disorder affects macroscopic magnetic behavior. This information can be used to produce magnetic nanomaterials with specific properties for applications such as permanent magnets, soft magnetic material for motors and biomedical applications.

  9. Organosilane grafted silica: Quantitative correlation of microscopic surface characters and macroscopic surface properties

    Science.gov (United States)

    Ji, Tuo; Ma, Chi; Brisbin, Logan; Mu, Liwen; Robertson, Christopher G.; Dong, Yalin; Zhu, Jiahua

    2017-03-01

    In polymer composites, organosilanes are often used to modify the surface property of silica nanoparticles and improve the interfacial properties. Surface properties of the modified silica, such as grafting density and consequent surface energy, largely depend on the molecular structure of the silane. Achieving maximum interfacial bonding between the filler and polymer requires precise control of silica surface property. In this work, four silanes with similar molecular structure but different alkyl chain lengths, trimethoxy(propyl)silane, trimethoxy(octyl)silane, hexadecyltrimethoxysilane and trimethoxy(octadecyl)silane, are selected as model agents to study their roles in influencing silica surface property. The grafting density of silane on the silica is well controlled by regulating the reaction conditions. Three main surface characters, silane grafting density, surface energy and surface potential, are measured. More importantly, a linear relationship has been correlated when plotting grafting density vs. surface energy and grafting density vs. surface potential. Utilizing these relationships, a linear model has been developed to predict grafting density and surface energy by simply measuring surface potential. This model has been validated by both commercial silica and synthesized silica particles of different sizes.

  10. Connecting microscopic physics with the macroscopic properties of materials in introductory physics courses

    CERN Document Server

    Lucas, Andrew

    2014-01-01

    An elementary understanding of the relevant length, mass and energy scales at the molecular level can be used to explain the order of magnitude of material properties such as mass density, latent heat, surface tension, elastic moduli and beyond in an introductory physics course. These order of magnitude estimates are remarkably easy to derive, and in many instances are the same for many different liquids and solids. This helps students to understand the origin of the zoo of material properties, and to connect molecular physics to the physics of familiar materials like water, metals and plastics. We also note some simple mechanisms by which material properties can easily vary over many orders of magnitude.

  11. The magnetic properties of the hollow cylindrical ideal remanence magnet

    DEFF Research Database (Denmark)

    Bjørk, Rasmus

    2016-01-01

    We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived...... and the generated field is compared to that of a Halbach cylinder of equal dimensions. The ideal remanence magnet is shown in most cases to generate a significantly lower field than the equivalent Halbach cylinder, although the field is generated with higher efficiency. The most efficient Halbach cylinder is shown...... to generate a field exactly twice as large as the equivalent ideal remanence magnet....

  12. The magnetic properties of the hollow cylindrical ideal remanence magnet

    CERN Document Server

    Bjørk, R

    2016-01-01

    We consider the magnetic properties of the hollow cylindrical ideal remanence magnet. This magnet is the cylindrical permanent magnet that generates a uniform field in the cylinder bore, using the least amount of magnetic energy to do so. The remanence distribution of this magnet is derived and the generated field is compared to that of a Halbach cylinder of equal dimensions. The ideal remanence magnet is shown in most cases to generate a significantly lower field than the equivalent Halbach cylinder, although the field is generated with higher efficiency. The most efficient Halbach cylinder is shown to generate a field exactly twice as large as the equivalent ideal remanence magnet.

  13. An atomistic modelling of the porosity impact on UO{sub 2} matrix macroscopic properties

    Energy Technology Data Exchange (ETDEWEB)

    Jelea, A., E-mail: andrei.jelea@irsn.fr [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Institute of Physical Chemistry Ilie Murgulescu, Romanian Academy, 202 Spl Independentei St., 060021 Bucharest-12 (Romania); Colbert, M. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Ribeiro, F. [Institut de Radioprotection et de Surete Nucleaire (IRSN), DPAM, SEMCA, LEC, Cadarache (France); Treglia, G. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Pellenq, R.J.-M. [Centre Interdisciplinaire des Nanosciences de Marseille, CNRS, Campus de Luminy, Marseille 13288 (France); Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2011-08-15

    Highlights: > The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated. > Atomistic simulation techniques were used in this study. > The UO{sub 2} thermal expansion coefficient is modified due to the pore surface effects. > The elastic moduli at 0 K and at finite temperature decrease linearly with porosity. - Abstract: The porosity impact on the UO{sub 2} matrix thermomechanical properties was investigated using atomistic simulation techniques. The porosity modifies the thermal expansion coefficient and this is attributed to pore surface effects. The elastic moduli at 0 K and at finite temperature decrease with porosity, this variation being well approximated using affine functions. These results agree with other mesoscale model predictions and experimental data, showing the ability of the semiempirical potential atomistic simulations to give an overall good description of the porous UO{sub 2}. However, the surface effects are incompletely described.

  14. Doping Effect of Graphene Nanoplatelets on Electrical Insulation Properties of Polyethylene: From Macroscopic to Molecular Scale

    Directory of Open Access Journals (Sweden)

    Ziang Jing

    2016-08-01

    Full Text Available The doping effect of graphene nanoplatelets (GNPs on electrical insulation properties of polyethylene (PE was studied by combining experimental and theoretical methods. The electric conduction properties and trap characteristics were tested for pure PE and PE/GNPs composites by using a direct measurement method and a thermal stimulated current (TSC method. It was found that doping smaller GNPs is more beneficial to decrease the conductivity of PE/GNPs. The PE/GNPs composite with smaller size GNPs mainly introduces deep energy traps, while with increasing GNPs size, besides deep energy traps, shallow energy traps are also introduced. These results were also confirmed by density functional theory (DFT and the non-equilibrium Green’s function (NEGF method calculations. Therefore, doping small size GNPs is favorable for trapping charge carriers and enhancing insulation ability, which is suggested as an effective strategy in exploring powerful insulation materials.

  15. Predictive model of transport properties of fuel cell membrane : from microscopic to macroscopic level

    Energy Technology Data Exchange (ETDEWEB)

    Colinart, T.; Lottin, O.; Maranzana, G.; Didierjean, S.; Moyne, C. [Nancy-Univ., Vandoeuvre-les-Nancy (France). Laboratoire d' Energetique et de Mecanique Theorique et Appliquee

    2007-07-01

    Because of their attractiveness as efficient and clean energy producers, proton exchange membrane fuel cells (PEMFC) can be used in automotive and small stationary applications. The electrochemical reaction takes place on two electrodes separated by a ionomer membrane. An important component of fuel cell water management and a problem for fuel cell performances involves the transport of protons from the anode to the cathode as its' transport properties are highly water dependent. Nafion membranes are widely used as an electrolyte for PEMFC. This paper presented a model to predict transport properties of polymer membranes such as Nafion used as electrolytes in a low temperature fuel cell. The paper discussed the electrical double layer that was used to determine surface charge density. The paper then discussed the analytical solution to the physical problem in the diffuse part of a cylindrical pore which involved solving the Poisson-Boltzmann, the Navier-Stokes and the Nernst-Planck equations. The properties of the electrolytic solution were equal to those of water and they were considered to be constant within the pore. A literature comparison with other models was also presented. It was concluded that in order to supplement the model, it is necessary to investigate the mechanics of the membrane, particularly the swelling behaviour, and the adsorption phenomena of the ions in the stern layer. 15 refs., 1 tab., 3 figs.

  16. Macroscopic spin and charge transport theory

    Institute of Scientific and Technical Information of China (English)

    Li Da-Fang; Shi Jun-Ren

    2009-01-01

    According to the general principle of non-equilibrium thermodynamics, we propose a set of macroscopic transport equations for the spin transport and the charge transport. In particular, the spin torque is introduced as a generalized 'current density' to describe the phenomena associated with the spin non-conservation in a unified framework. The Einstein relations and the Onsager relations between different transport phenomena are established. Specifically, the spin transport properties of the isotropic non-magnetic and the isotropic magnetic two-dimensional electron gases are fully described by using this theory, in which only the macroscopic-spin-related transport phenomena allowed by the symmetry of the system are taken into account.

  17. Effects of magnetic field on fluidization properties of magnetic pearls

    Institute of Scientific and Technical Information of China (English)

    Maoming Fan; Zhenfu Luo; Yuemin Zhao; Qingru Chen; Daniel Tao; Xiuxiang Tao; Zhenqiang Chen

    2007-01-01

    An experimental study of the influence of external magnetic field on the fluidization behavior of magnetic pearls was carried out. Magnetic pearls are a magnetic form of iron oxide that mainly consists of Fe2O3 which are recovered from a high-volume power plant fly ash from pulverized coal combustion. Due to its abundance, low price and particular physical and chemical properties, magnetic pearls can be used as a heavy medium for minerals or solid waste dry separation based on density difference. This paper introduces the properties of magnetic pearls and compares the performance of magnetic pearls fluidised bed operation with or without an external magnetic field. Experimental results show that an external magnetic field significantly improves the fluidization performance of magnetic pearls such as uniformity and stability.

  18. Impact of thickness on microscopic and macroscopic properties of Fe-Te-Se superconductor thin films

    Directory of Open Access Journals (Sweden)

    N. Zhang

    2015-04-01

    Full Text Available A series of iron based Fe-Te-Se superconductor thin films depositing on 0.7wt% Nb-doped SrTiO3 at substrate temperatures in the 250°C -450°C range by pulsed laser ablation of a constituents well defined precursor FeTe0.55Se0.55 target sample. We study the possible growth mechanism and its influence on the superconductor properties. Experimental results indicate the superconductive and non-superconductive properties are modulated only by the thickness of the thin films through the temperature range. The films appear as superconductor whenever the thickness is above a critical value ∼30nm and comes to be non-superconductor below this value. Relative ratios of Fe to (Te+Se in the films retained Fe/(Te+Se1 for non-superconductor no matter what the film growth temperature was. The effect of film growth temperature takes only the role of modulating the ratio of Te/Se and improving crystallinity of the systems. According to the experimental results we propose a sandglass film growth mechanism in which the interfacial effect evokes to form a Fe rich area at the interface and Se or Te starts off a consecutive filling up process of chalcogenide elements defect sides, the process is significant before the film thickness reaches at ∼30nm.

  19. Scaling of Macroscopic Properties of Porous Sediments Experiencing Compaction: Implications for Geothermal Gradient and Methane Inventory

    CERN Document Server

    Goldobin, Denis S

    2011-01-01

    Porous sediments in geological systems experience stress by the above-laying mass and consequent compaction, which may be significantly nonuniform across the massif. We derive scaling laws for the compaction of sediments of similar geological origin. With these laws, we evaluate the dependence of the transport properties of a fluid-saturated porous medium (permeability, effective molecular diffusivity, hydrodynamic dispersion, and thermal conductivity) on its porosity. In particular, we demonstrate irrelevance of the assumption of a uniform geothermal gradient for systems with nonuniform compaction and importance of the derived scaling laws for mathematical modelling of methane hydrate deposits, which are believed to have potential for impact on global climate change and Glacial-Interglacial cycles.

  20. Magnetic materials fundamentals, products, properties, applications

    CERN Document Server

    Hilzinger, Rainer

    2013-01-01

    At a practical level, this compendium reviews the basics of soft and hard magnetic materials, discusses the advantages of the different processing routes for the exploitation of the magnetic properties and hence assists in proper, fail-safe and economic application of magnetic materials. Essential guidelines and formulas for the calculation of the magnetic and electrical properties, temperature and long-term stability of permanent magnets, of inductive components and magnetic shielding are compiled. Selected fields of application and case studies illustrate the large diversity of technical applications. Application engineers will appreciate the comprehensive compilation of the properties and detailed characteristic curves of modern soft and hard magnetic materials. Materials scientists will enjoy the presentation of the different processing routes and their impact on the magnetic properties and students will profit from the survey from the basics of magnetism down to the applications in inductive components, ...

  1. To the theory of elastic properties of isotropic magnetic gels. Effect of interparticle interaction

    Science.gov (United States)

    Lopez-Lopez, M. T.; Iskakova, L. Yu; Zubarev, A. Yu; Borin, D. Yu

    2017-09-01

    The paper deals with theoretical study of elastic shear properties of a magnetic gel, consisting of spherical magnetizable particles, randomly (gas-like) distributed in an elastic matrix. We suppose that the composite is placed in a magnetic field, perpendicular to the direction of the sample shear. In order to get mathematically rigorous results, we have restricted ourselves by the analysis of the system with a low concentration of the particles. Magnetic and elastic (through the matrix deformation) interactions between them are considered in the framework of the regular pair approximation. Analysis shows that external magnetic field decreases the macroscopic shear modulus of the composite with a low concentration of the particles. The decreasing dependence of the modulus on the macroscopic shear is estimated. We believe that the suggested rigorous approach can be a robust background for the study of the systems with a high concentration of the particles.

  2. Using microwave and macroscopic samples of dielectric solids to study the photonic properties of disordered photonic bandgap materials.

    Science.gov (United States)

    Hashemizad, Seyed Reza; Tsitrin, Sam; Yadak, Polin; He, Yingquan; Cuneo, Daniel; Williamson, Eric Paul; Liner, Devin; Man, Weining

    2014-09-26

    Recently, disordered photonic materials have been suggested as an alternative to periodic crystals for the formation of a complete photonic bandgap (PBG). In this article we will describe the methods for constructing and characterizing macroscopic disordered photonic structures using microwaves. The microwave regime offers the most convenient experimental sample size to build and test PBG media. Easily manipulated dielectric lattice components extend flexibility in building various 2D structures on top of pre-printed plastic templates. Once built, the structures could be quickly modified with point and line defects to make freeform waveguides and filters. Testing is done using a widely available Vector Network Analyzer and pairs of microwave horn antennas. Due to the scale invariance property of electromagnetic fields, the results we obtained in the microwave region can be directly applied to infrared and optical regions. Our approach is simple but delivers exciting new insight into the nature of light and disordered matter interaction. Our representative results include the first experimental demonstration of the existence of a complete and isotropic PBG in a two-dimensional (2D) hyperuniform disordered dielectric structure. Additionally we demonstrate experimentally the ability of this novel photonic structure to guide electromagnetic waves (EM) through freeform waveguides of arbitrary shape.

  3. Terahertz Science and Technology of Macroscopically Aligned Carbon Nanotube Films

    Science.gov (United States)

    Kono, Junichiro

    One of the outstanding challenges in nanotechnology is how to assemble individual nano-objects into macroscopic architectures while preserving their extraordinary properties. For example, the one-dimensional character of electrons in individual carbon nanotubes leads to extremely anisotropic transport, optical, and magnetic phenomena, but their macroscopic manifestations have been limited. Here, we describe methods for preparing macroscopic films, sheets, and fibers of highly aligned carbon nanotubes and their applications to basic and applied terahertz studies. Sufficiently thick films act as ideal terahertz polarizers, and appropriately doped films operate as polarization-sensitive, flexible, powerless, and ultra-broadband detectors. Together with recently developed chirality enrichment methods, these developments will ultimately allow us to study dynamic conductivities of interacting one-dimensional electrons in macroscopic single crystals of single-chirality single-wall carbon nanotubes.

  4. Magnetic Properties of Magnetic Nanoparticles for Efficient Hyperthermia

    Directory of Open Access Journals (Sweden)

    Ihab M. Obaidat

    2015-01-01

    Full Text Available Localized magnetic hyperthermia using magnetic nanoparticles (MNPs under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to enhance the power dissipation or heating efficiency of MNPs. Several factors influence the heating efficiency of MNPs, such as the amplitude and frequency of the applied magnetic field and the structural and magnetic properties of MNPs. We discuss some of the physics principles for effective heating of MNPs focusing on the role of surface anisotropy, interface exchange anisotropy and dipolar interactions. Basic magnetic properties of MNPs such as their superparamagnetic behavior, are briefly reviewed. The influence of temperature on anisotropy and magnetization of MNPs is discussed. Recent development in self-regulated hyperthermia is briefly discussed. Some physical and practical limitations of using MNPs in magnetic hyperthermia are also briefly discussed.

  5. Variation of some wood macroscopic properties along the stem of Acacia melanoxylon R. Br. adult trees in Portugal

    Energy Technology Data Exchange (ETDEWEB)

    Santos, A.; Simoes, R.; Tavares, M.

    2013-07-01

    Aim of the study: The aim of the study is to assess the variation of pith eccentricity, heartwood proportion, late wood percentage and basic wood density along the stem of 45-year-old A. melanoxylon trees collected in four sites of Portugal, and investigate the eventual relationship between these variables. Area of study: Sites covering littoral north, mid interior north and centre interior of Portugal. Materials and methods: Four sites and five trees per site were selected in the Acacia melanoxylon Portuguese forest. One wood sample at each of six height levels per tree was collected in order to evaluate its basic density, pith eccentricity, heartwood and late wood proportions. Main results: The high variability of the wood macroscopic properties among trees from the same site regarding to the variation of the corresponding average properties along the stem is a key characteristic of the experimental data. As a consequence, a multiple linear regression model tested was not able to properly explain the wood basic density variation of the 120 wood samples analysed. In spite of this, the following trends could be recognized: (i) excluding the base level, wood basic density moderately increased with tree level; (ii) late wood proportion followed similar behaviour; (iii) pith eccentricity was low; (iv) heartwood proportion decreased markedly with tree height, from 70% at the base to 7% at the top. Research highlights: The high basic density, the relatively low variability along the stem and the low pith eccentricity enable us to anticipate good performance as raw material for the wood industry. (Author)

  6. First-principles determination of magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Wu Ruqian; Yang Zongxian; Hong Jisang [Department of Physics, University of California, Irvine, CA (United States)

    2003-02-12

    First-principles density functional theory calculations have achieved great success in the exciting field of low-dimension magnetism, in explaining new phenomena observed in experiments as well as in predicting novel properties and materials. As known, spin-orbit coupling (SOC) plays an extremely important role in various magnetic properties such as magnetic anisotropy, magnetostriction, magneto-optical effects and spin-dynamics. Using the full potential linearized augmented plane wave approach, we have carried out extensive investigations for the effects of SOC in various materials. Results of selected examples, such as structure and magnetic properties of Ni/Cu(001), magnetism and magnetic anisotropy in magnetic Co/Cu(001) thin films, wires and clusters, magnetostriction in FeGa alloys and magneto-optical effects in Fe/Cr superlattices, are discussed.

  7. Electromechanical properties of radial active magnetic bearings

    OpenAIRE

    Antila, Matti

    1998-01-01

    Nonideal properties of the electromagnetic actuators in radial active magnetic bearings are studied. The two dimensional nonlinear stationary finite element method is used to determine the linearised parameters of a radial active magnetic bearing. The method is verified on two test machines. The accuracy is 10-15 % in the magnetic saturation region. The effect of magnetic saturation on the bearing dynamics is studied based on the root locus diagrams of the closed loop system. These diagrams s...

  8. Magnetic Properties of Tcnq Complexes

    Science.gov (United States)

    Qureshi, Saleem

    Available from UMI in association with The British Library. Requires signed TDF. This work can be divided up into three complementary steps. The first part of the work involved synthesis of a large number of TCNQ complexes, in particular complex salts, which are known to have promising electrical properties due to reduction in the on-site Coloumbic repulsion between the electrons. The cations used for the complexes are C12BPE (dodecyl bi pyridyl ethelenium), C10BPE, C8BPE, C6BPE, GTPP (geronyl triphenyl phosphonium), BI (butyl imidazolium), DMI (dimethyl imidazolium) and TB (toluidine blue). The second part of the project was to characterize these materials using different techniques to try to build up a knowledge of the materials. Particular interest was involved in the study of magnetic behaviour and in the later parts of the work some electrical measurements were made to try to determine the band gap, mobility and temperature dependence of conductivity. Considering the quasi-one-dimensional nature of the TCNQ salts, a theoretical model was devised based on the solution of one dimensional Heisenberg spin Hamiltonian. A computer program was developed that allowed for a numerical solution of a chain of spins in which number of spins could be varied. The Hamiltonian could be solved for up to 12 spins, the maximum allowable by the ICL 2900 computer at Crips computer centre of the University of Nottingham. The program allowed the user to input the coupling energy and alternation parameter between adjacent spins. The results from this program were used to explain magnetic behaviour of the TCNQ complexes prepared during this work.

  9. Probing the Microscopic with the Macroscopic: from Properties of Star Cluster Systems to Properties of Cluster-Forming Regions

    Science.gov (United States)

    Parmentier, G.

    To understand how systems of star clusters have reached their presently observed properties constitutes a powerful probe into the physics of cluster formation, without needing to resort to high spatial resolution observations of individual cluster-forming regions (CFRg) in distant galaxies. In this contribution I focus on the mass-radius relation of CFRgs, how it can be uncovered by studying the gas expulsion phase of forming star clusters, and what the implications are. I demonstrate that, through the tidal field impact upon exposed star clusters, the CFRg mass-radius relation rules cluster infant weight-loss in dependence of cluster mass. The observational constraint of a time-invariant slope for the power-law young cluster mass function is robustly satisfied by CFRgs with a constant mean volume density. In contrast, a constant mean surface density would be conducive to the preferential destruction of high-mass clusters. A purely dynamical line-of-reasoning leads therefore to a conclusion consistent with star formation a process driven by a volume density threshold. Developing this concept further, properties of molecular clumps and CFRgs naturally get dissociated. This allows to understand: (i) why the star cluster mass function is steeper than the molecular cloud/clump mass function; (ii) the presence of a massive star formation limit in the mass-size space of molecular structures.

  10. The Characterization of the Magnetic Properties of Soft Magnetic Materials

    DEFF Research Database (Denmark)

    Larsen, Raino Michael

    1996-01-01

    The hysteresis curve and magnetic properties such as permeability, saturation induction, residual induction, coercive force and hysteresis losses are presented. The design and construction of equipment making it possible to measure true DC-values as well as AC-properties of toroid rings and cylin......The hysteresis curve and magnetic properties such as permeability, saturation induction, residual induction, coercive force and hysteresis losses are presented. The design and construction of equipment making it possible to measure true DC-values as well as AC-properties of toroid rings...

  11. Diagnosis of bladder tumours in patients with macroscopic haematuria: a prospective comparison of split-bolus computed tomography urography, magnetic resonance urography and flexible cystoscopy.

    Science.gov (United States)

    Gandrup, Karen L; Løgager, Vibeke B; Bretlau, Thomas; Nordling, Jørgen; Thomsen, Henrik S

    2015-06-01

    The aim of this study was to compare split-bolus computed tomography urography (CTU), magnetic resonance urography (MRU) and flexible cystoscopy in patients with macroscopic haematuria regarding the diagnosis of bladder tumours. In this prospective study, 150 patients underwent CTU, MRU and flexible cystoscopy. Two uroradiologists individually reviewed the images without any clinical information, using a questionnaire. Patient records and pathology reports were also reviewed. At flexible cystoscopy, MRU and CTU, 32, 19 and 15 bladder lesions were identified, respectively. Histopathology showed that 13 of the 29 biopsied lesions were transitional cell carcinomas. Compared with the histopathology, the sensitivity and specificity for detection of tumours by CTU and MRU were 61.5% and 94.9%, and 79.9% and 93.4%, respectively. False-positive detection of bladder tumours, compared with histopathology, was reported in seven CTUs and nine MRUs, whereas the number of false-negative findings was five for CTUs and three for MRUs. Split-bolus CTU or MRU cannot replace cystoscopy in cases of macroscopic haematuria. MRU has a higher sensitivity than split-bolus CTU, and is a potential alternative to flexible cystoscopy. Patients with a low risk of bladder cancer may forgo flexible cystoscopy if a bladder tumour is identified by either CTU or MRU, and proceed straight to transuretheral resection of the bladder.

  12. Magnetic Properties of NdAl2

    DEFF Research Database (Denmark)

    Bak, P.

    1974-01-01

    The magnetic properties of NdAl2 are calculated using a Hamiltonian including crystal-field and isotropic exchange interaction terms. A two-dimensional mean-field theory is evaluated to calculate single-crystal magnetization curves. It is shown that the magnetic properties can be understood using...... the crystal-field parameters derived from the magnetic exciton spectrum measured by Houmann et al. by means of inelastic neutron scattering. The combined lambda -Schottky anomaly in the heat capacity is explained. No additional parameters are introduced....

  13. MAGNETIC NANOFLUID WITH ANTITUMORAL PROPERTIES

    Directory of Open Access Journals (Sweden)

    Alexandru Mihai Grumezescu

    2012-09-01

    Full Text Available The present study deals with the synthesis and characterization of magnetic nanofluid and it’s in vitro anti-cancer activity against HEp2 cells. The magnetic nanofluid with an average size of 10 nm was synthesized via a modified precipitation technique and characterized by FT-IR, XRD, DTA-TG and TEM. After 24 h incubation of HEp2 with the magnetic nanofluid, significant changes in the cell morphology were discernible in fluorescent microscopy. Cytotoxicity assay shows that the magnetic nanofluid exhibits significant cytotoxicity against HEp2, 50% of thee cells being killed after 24 hours incubation with magnetic nanofluid without any external alternating magnetic field.

  14. Properties of Simulated Magnetized Galaxy Clusters

    CERN Document Server

    Dolag, K

    2000-01-01

    We study the evolution of magnetized clusters in a cosmological environment using magneto-hydro dynamical simulations. Large scale flows and merging of subclumps generate shear flows leading to Kelvin-Helmholtz instabilities, which, in addition to the compression of the gas where the magnetic field is frozen in, further amplify the magnetic field during the evolution of the cluster. Therefore, well-motivated initial magnetic fields of $^{1/2}=10^{-9} {\\rm G}$ reach the observed $\\sim\\mu{\\rm G}$ field strengths in the cluster cores at $z=0$. These magnetized clusters can be used to study the final magnetic field structure, the dynamical importance of magnetic fields for the interpretation of observed X-Ray properties, and help to constrain further processes in galaxy clusters like the population of relativistic particles giving rise to the observed radio halos or the behavior of magnetized cooling flows.

  15. Magnetic and electronic properties of ruthenocuprates

    Science.gov (United States)

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

    2001-03-01

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

  16. Reconstruction of material properties profiles in one-dimensional macroscopically inhomogeneous rigid frame porous media in the frequency domain.

    Science.gov (United States)

    De Ryck, L; Lauriks, W; Leclaire, P; Groby, J P; Wirgin, A; Depollier, C

    2008-09-01

    The present paper deals with the inverse scattering problem involving macroscopically inhomogeneous rigid frame porous media. It consists of the recovery, from acoustic measurements, of the profiles of spatially varying material parameters by means of an optimization approach. The resolution is based on the modeling of acoustic wave propagation in macroscopically inhomogeneous rigid frame porous materials, which was recently derived from the generalized Biot's theory. In practice, the inverse problem is solved by minimizing an objective function defined in the least-square sense by the comparison of the calculated reflection (and transmission) coefficient(s) with the measured or synthetic one(s), affected or not by additive Gaussian noise. From an initial guess, the profiles of the x-dependent material parameters are reconstructed iteratively with the help of a standard conjugate gradient method. The convergence rate of the latter and the accuracy of the reconstructions are improved by the availability of an analytical gradient.

  17. Magnetic properties of ground-state mesons

    Energy Technology Data Exchange (ETDEWEB)

    Simonis, V. [Vilnius University Institute of Theoretical Physics and Astronomy, Vilnius (Lithuania)

    2016-04-15

    Starting with the bag model a method for the study of the magnetic properties (magnetic moments, magnetic dipole transition widths) of ground-state mesons is developed. We calculate the M1 transition moments and use them subsequently to estimate the corresponding decay widths. These are compared with experimental data, where available, and with the results obtained in other approaches. Finally, we give the predictions for the static magnetic moments of all ground-state vector mesons including those containing heavy quarks. We have a good agreement with experimental data for the M1 decay rates of light as well as heavy mesons. Therefore, we expect our predictions for the static magnetic properties (i.e., usual magnetic moments) to be of sufficiently high quality, too. (orig.)

  18. Magnetic properties of ground-state mesons

    CERN Document Server

    Simonis, Vytautas

    2016-01-01

    Starting with the bag model a method for the study of the magnetic properties (magnetic moments, magnetic dipole transition widths) of ground-state mesons is developed. We calculate the M1 transition moments and use them subsequently to estimate the corresponding decay widths. These are compared with experimental data, where available, and with the results obtained in other approaches. Finally, we give the predictions for the static magnetic moments of all ground-state vector mesons including those containing heavy quarks. We have a good agreement with experimental data for the M1 decay rates of light as well as heavy mesons. Therefore, we expect our predictions for the static magnetic properties (usual magnetic moments) to be of sufficiently high quality, too.

  19. Characterizing Magnetic Properties in Belize Corals

    Science.gov (United States)

    Urbalejo, A. A.; Bhattacharya, A.; Gee, J. S.; Mitra, R.; Carilli, J.; Hangsterfer, A.; Feinberg, J. M.

    2016-12-01

    Measurements of magnetic remanence and characterization of magnetic phases are widely applied to environmental and climate studies; however, magnetic tools have not been widely applied to coral studies. As such, there is a deficit in our understanding of magnetic materials and behavior in coral skeletons and consequently, of processes by which magnetic materials may get incorporated into coral skeletons. In this study, we present magnetic measurements conducted on freshly broken chips from coral cores; the cores were collected from Mesoamerican sites in Belize. Trace, minor, and major element concentration has been well studied in these two coral cores, using inductively coupled mass spectrometric techniques (ICP-MS). The goal of our current research is to determine are as follows: (a) Is there is a viable magnetic signal that can be obtained from measuring chips broken off of coral skeletons? (b) What are some of the dominant magnetic behaviors? (c) What are the carrier phases of magnetic material? (c) can we determine possible variations in the type and quantity of magnetic materials over time and ultimately, (e) can magnetic fingerprinting of corals can be used as tracers of environmental, climate or biological processes? Here, we present preliminary magnetic remanence measurements (IRM and double IRM) from the two coral cores collected from Belize and dating back to the mid 1800s. Early results using freshly broken chips from both coral cores indicate a magnetite-like soft magnetic component during IRM experiments. Double-IRM experiments on the same samples indicate uniaxial single domain behavior. Furthermore, SEM images suggest that the magnetic carrier phase could likely be magnetite. We will also present comparisons of our magnetic data with newly collected X-Ray Fluorescence (XRF) data on the same coral cores. The goal is to properly characterize the type of magnetic signals and determine possible environmental and/or biological impacts on magnetic carrier

  20. Magnetic and Electrical Properties of Leachate

    Directory of Open Access Journals (Sweden)

    Kartika Kirana

    2011-11-01

    Full Text Available Heavy metals content as well as magnetic and electrical properties of leachate from Sarimukti, West Java were studied in an attempt to seek correlation between heavy metals content and magnetic/electrical properties. Such correlation is expected to open the way for the use of magnetic/electrical properties as proxy indicators for the concentration of heavy metals in the leachate. The number of leachate samples studied is 21; 15 were taken spatially at depth of 1 m while the remaining 6 samples were taken vertically at a particular point. Measurement results showed that the heavy metals content in the leachate has a smaller concentration, except for Fe. The correlation between magnetic susceptibility and heavy metals content was found to be not so significant. The best correlation coefficient between magnetic susceptibility with heavy metals in leachate was found in Zn. Correlation between electrical conductivity and heavy metal is also not so significant, except for Zn and Cd. The use of magnetic properties as proxy indicator for heavy metals content in leachate is plausible provided that the magnetic susceptibility exceeds certain threshold value. Correlation between magnetic susceptibility, electrical conductivity and heavy metal content would be good if each quantity has a large value.

  1. Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

    Science.gov (United States)

    Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

    2016-06-01

    Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

  2. Thermodynamical properties and thermoelastic coupling of complex macroscopic structure; Elastomeri proprieta` termodinamiche ed effetto termoelastico di una struttura complessa : teoria e prove termovisive sperimentali per una analisi di fattibilita`

    Energy Technology Data Exchange (ETDEWEB)

    Fabbri, M.; Sacripanti, A. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dip. Innovazione

    1996-11-01

    Gross qualitative/quantitative analysis about thermodynamical properties and thermoelastic coupling (or elastocaloric effect) of complex macroscopic structure (running shoes) is performed by infrared camera. The experimental results showed the achievability of a n industrial research project.

  3. Dynamical properties of unconventional magnetic systems

    Energy Technology Data Exchange (ETDEWEB)

    Helgesen, G. [ed.

    1997-05-01

    The Advanced Study Institute addressed the current experimental and theoretical knowledge of the dynamical properties of unconventional magnetic systems including low-dimensional and mesoscopic magnetism, unconventional ground state, quantum magnets and soft matter. The main approach in this Advanced Study Institute was to obtain basic understanding of co-operative phenomena, fluctuations and excitations in the wide range unconventional magnetic systems now being fabricated or envisioned. The report contains abstracts for lectures, invited seminars and posters, together with a list of the 95 participants from 24 countries with e-mail addresses

  4. Ultrathin magnetic structures II measurement techniques and novel magnetic properties

    CERN Document Server

    Heinrich, Bretislav

    2006-01-01

    The ability to understand and control the unique properties of interfaces has created an entirely new field of magnetism, with profound impact in technology and serving as the basis for a revolution in electronics. Our understanding of the physics of magnetic nanostructures has also advanced significantly. This rapid development has generated a need for a comprehensive treatment that can serve as an introduction to the field for those entering it from diverse fields, but which will also serve as a timely overview for those already working in this area. The four-volume work Ultra-Thin Magnetic

  5. Granular superconductivity and magnetic-field-driven recovery of macroscopic coherence in a cuprate/manganite multilayer

    OpenAIRE

    Mallett, B. P. P.; Khmaladze, J.; Marsik, P.; Perret, E.; Cerreta, A.; Orlita, M.; Biškup, N.; Varela, M.; Bernhard, C.

    2015-01-01

    We show that in Pr$ _{0.5} $La$ _{0.2} $Ca$ _{0.3} $MnO$ _{3} $/YBa$ _{2} $Cu$ _{3} $O$ _{7} $ (PLCMO/YBCO) multilayers the low temperature state of YBCO is very resistive and resembles the one of a granular superconductor or a frustrated Josephson-junction network. Notably, a coherent superconducting response can be restored with a large magnetic field which also suppresses the charge-orbital order in PLCMO. This coincidence suggests that the granular superconducting state of YBCO is induced...

  6. Granular superconductivity and magnetic-field-driven recovery of macroscopic coherence in a cuprate/manganite multilayer

    Science.gov (United States)

    Mallett, B. P. P.; Khmaladze, J.; Marsik, P.; Perret, E.; Cerreta, A.; Orlita, M.; Biškup, N.; Varela, M.; Bernhard, C.

    2016-11-01

    We show that in Pr0.5La0.2Ca0.3MnO3 /YBa2Cu3O7 (PLCMO/YBCO) multilayers the low temperature state of YBCO is very resistive and resembles that of a granular superconductor or a frustrated Josephson-junction network. Notably, a coherent superconducting response can be restored with a large magnetic field which also suppresses the charge-orbital order in PLCMO. This coincidence suggests that the granular superconducting state of YBCO is induced by the charge-orbital order of PLCMO. The coupling mechanism and the nature of the induced inhomogeneous state in YBCO remain to be understood.

  7. Tailoring Magnetic Properties in Bulk Nanostructured Solids

    Science.gov (United States)

    Morales, Jason Rolando

    Important magnetic properties and behaviors such as coercivity, remanence, susceptibility, energy product, and exchange coupling can be tailored by controlling the grain size, composition, and density of bulk magnetic materials. At nanometric length scales the grain size plays an increasingly important role since magnetic domain behavior and grain boundary concentration determine bulk magnetic behavior. This has spurred a significant amount of work devoted to developing magnetic materials with nanometric features (thickness, grain/crystallite size, inclusions or shells) in 0D (powder), 1D (wires), and 2D (thin films) materials. Large 3D nanocrystalline materials are more suitable for many applications such as permanent magnets, magneto-optical Faraday isolators etc. Yet there are relatively few successful demonstrations of 3D magnetic materials with nanoscale influenced properties available in the literature. Making dense 3D bulk materials with magnetic nanocrystalline microstructures is a challenge because many traditional densification techniques (HIP, pressureless sintering, etc.) move the microstructure out of the "nano" regime during densification. This dissertation shows that the Current Activated Pressure Assisted Densification (CAPAD) method, also known as spark plasma sintering, can be used to create dense, bulk, magnetic, nanocrystalline solids with varied compositions suited to fit many applications. The results of my research will first show important implications for the use of CAPAD for the production of exchange-coupled nanocomposite magnets. Decreases in grain size were shown to have a significant role in increasing the magnitude of exchange bias. Second, preferentially ordered bulk magnetic materials were produced with highly anisotropic material properties. The ordered microstructure resulted in changing magnetic property magnitudes (ex. change in coercivity by almost 10x) depending on the relative orientation (0° vs. 90°) of an externally

  8. Influence of nitrogen flow on structure and magnetic properties of magnetron-sputtered FeCo/TiN multilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Klever, Christian; Seemann, Klaus [Forschungszentrum Karlsruhe, Institute of Materials Research I, Eggenstein-Leopoldshafen (Germany)

    2009-07-01

    Soft magnetic thin films with appropriate high frequency properties are interesting for applications, e.g., as core material for microinductors and for magnetoelastic sensors/actuators. For the use in such devices, tailoring of the magnetic film properties (e. g. saturation magnetization M{sub S}, coercitive field H{sub C}, anisotropy field H{sub K}) is necessary. In this study, multilayer films consisting of FeCo as the magnetic constituent and TiN as diffusion barrier are developed. The films are grown by sequential magnetron sputter deposition using a FeCo and a TiN target in an Ar atmosphere with an additional N{sub 2} flow between 0 and 5 % of the total gas flow. The films are annealed ex-situ in a static magnetic field. The static and dynamic macroscopic magnetic properties of the films are determined by means of a vibrating sample magnetometer and a strip-line permeameter connected to a vector network analyzer, respectively. The microstructure and constitution of the films are examined by XRD, XRR, TEM and AES depth profiling. It is shown that films with a coercitive field below 0.2 mT and a sufficient high frequency response can be produced by defining appropriate growth and film annealing conditions. Furthermore, the correlation between the nanoscale coating architecture, the films' microstructure and its macroscopic magnetic properties is presented.

  9. Properties of magnetic nano-particles

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1997-01-01

    The intrinsic thermodynamic magnetic properties of clusters are discussed using spin wave theory for a Heisenberg model, with a fixed magnitude of the spins S-i = S and site independent nearest neighbor exchange interaction. The consequences of the more realistic Hubbard model is considered...... in which we allow for a magnetization profile at T = 0 and a structural relaxation, which in turn will give rise to a site dependent exchange interaction. Et is concluded that correlation effects among the electrons play a very important role in small clusters, albeit not modifying the thermodynamic...... properties drastically. The finite cluster size gives foremost rise to a discrete excitation spectrum with a large energy gap to the ground state. The relaxation of the magnetization during the reversal of the external magnetic field is discussed. A first step towards a quantitative understanding...

  10. Magnetic properties of polymerized diphenyloctatetrayne

    Energy Technology Data Exchange (ETDEWEB)

    Beristain, Miriam F.; Jimenez-Solomon, Maria F.; Ortega, Alejandra; Escudero, Roberto [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, Ciudad Universitaria, Mexico DF 04510 (Mexico); Munoz, Eduardo [Instituto de Fisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-364, Ciudad Universitaria, Mexico DF 01000 (Mexico); Maekawa, Yasunari; Koshikawa, Hiroshi [High Performance Polymer Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Ogawa, Takeshi, E-mail: ogawa@unam.mx [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-360, Ciudad Universitaria, Mexico DF 04510 (Mexico)

    2012-10-15

    A new type of metal-free ferromagnetic carbon material was obtained by thermal polymerization and electron beam irradiation of diphenyloctatetrayne (DPOT). The isothermal magnetic measurements showed hysteresis loops indicating weak but intrinsic ferromagnetism with Curie temperatures of around 600 K. Electron spin resonance spectroscopy showed that the material contained stable free radicals in the range of 10{sup 17}-10{sup 20} radicals g{sup -1} depending on the polymerization process. The ferromagnetism should be due to high radical concentration although no correlation was observed between them. It was shown that an amorphous ferromagnetic carbon could be obtained from a simple crystalline solid by heating at moderate temperatures. Highlights: Black-Right-Pointing-Pointer Diphenyloctatetrayne as a precursor for carbon with high radical concentration. Black-Right-Pointing-Pointer The carbon material consists of sp{sup 2} configuration. Black-Right-Pointing-Pointer A weak intrinsic metal-free ferromagnetism was observed for the carbon products.

  11. Covariant Macroscopic Quantum Geometry

    CERN Document Server

    Hogan, Craig J

    2012-01-01

    A covariant noncommutative algebra of position operators is presented, and interpreted as the macroscopic limit of a geometry that describes a collective quantum behavior of the positions of massive bodies in a flat emergent space-time. The commutator defines a quantum-geometrical relationship between world lines that depends on their separation and relative velocity, but on no other property of the bodies, and leads to a transverse uncertainty of the geometrical wave function that increases with separation. The number of geometrical degrees of freedom in a space-time volume scales holographically, as the surface area in Planck units. Ongoing branching of the wave function causes fluctuations in transverse position, shared coherently among bodies with similar trajectories. The theory can be tested using appropriately configured Michelson interferometers.

  12. Magnetic Properties of 3D Printed Toroids

    Science.gov (United States)

    Bollig, Lindsey; Otto, Austin; Hilpisch, Peter; Mowry, Greg; Nelson-Cheeseman, Brittany; Renewable Energy; Alternatives Lab (REAL) Team

    Transformers are ubiquitous in electronics today. Although toroidal geometries perform most efficiently, transformers are traditionally made with rectangular cross-sections due to the lower manufacturing costs. Additive manufacturing techniques (3D printing) can easily achieve toroidal geometries by building up a part through a series of 2D layers. To get strong magnetic properties in a 3D printed transformer, a composite filament is used containing Fe dispersed in a polymer matrix. How the resulting 3D printed toroid responds to a magnetic field depends on two structural factors of the printed 2D layers: fill factor (planar density) and fill pattern. In this work, we investigate how the fill factor and fill pattern affect the magnetic properties of 3D printed toroids. The magnetic properties of the printed toroids are measured by a custom circuit that produces a hysteresis loop for each toroid. Toroids with various fill factors and fill patterns are compared to determine how these two factors can affect the magnetic field the toroid can produce. These 3D printed toroids can be used for numerous applications in order to increase the efficiency of transformers by making it possible for manufacturers to make a toroidal geometry.

  13. Calculation of the microscopic and macroscopic linear and nonlinear optical properties of liquid acetonitrile. II. Local fields and linear and nonlinear susceptibilities in quadrupolar approximation.

    Science.gov (United States)

    Avramopoulos, A; Papadopoulos, M G; Reis, H

    2007-03-15

    A discrete model based on the multipolar expansion including terms up to hexadecapoles was employed to describe the electrostatic interactions in liquid acetonitrile. Liquid structures obtained form molecular dynamics simulations with different classical, nonpolarizable potentials were used to analyze the electrostatic interactions. The computed average local field was employed for the determination of the environmental effects on the linear and nonlinear electrical molecular properties. Dipole-dipole interactions yield the dominant contribution to the local field, whereas higher multipolar contributions are small but not negligible. Using the effective in-phase properties, macroscopic linear and nonlinear susceptibilities of the liquid were computed. Depending on the partial charges describing the Coulomb interactions of the force field employed, either the linear properties (refractive index and dielectric constant) were reproduced in good agreement with experiment or the nonlinear properties [third-harmonic generation (THG) and electric field induced second-harmonic (EFISH) generation] and the bulk density but never both sets of properties together. It is concluded that the partial charges of the force fields investigated are not suitable for reliable dielectric properties. New methods are probably necessary for the determination of partial charges, which should take into account the collective and long-range nature of electrostatic interactions more precisely.

  14. Properties of magnetically attractive experimental resin composites.

    Science.gov (United States)

    Hirano, S; Yasukawa, H; Nomoto, R; Moriyama, K; Hirasawa, T

    1996-12-01

    SUS444 stainless steel filled chemically cured resin composites that can attract magnet were fabricated. The filler was treated with various concentrations of silane. The experimental composite was easy to handle and showed a good shelf life. The maximal properties obtained are as follows; The attraction force to a magnetic attachment was 1/3-1/4 lower than the commercially available magnet-keeper system for dental magnetic attachment. Flexural strength and Knoop hardness of the composite were 76MPa (7.7 kgf/mm2) and 64 KHN. These values were lower than the commercially available chemically cured composite used as a reference. Eluted metal from the composite in 1% lactic acid solution for 7 days showed 0.7 mg/cm2, but in 0.9% NaCl solution for 7 days, it could not be detected.

  15. Magnetic susceptibility properties of polluted soils

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An investigation of magnetic properties using magnetic susceptibility (X) and frequency-dependent susceptibility (Xfd) was conducted on representative modern pollutants, which include smelted slag dust, automobile exhaust dust and coal ash. Their magnetic susceptibility values are more than 500×10-8 m3/kg, and frequency-dependent susceptibility values less than 3%, indicating that ample ferrimagnetic and scanty superparamagnetic grains occurred in the studied pollutants. Similar to the artificially synthetic polluted soils, the industrially-polluted soils display a negative relationship between magnetic susceptibility and frequency-dependent susceptibility. However, the unpolluted soils, e.g. the Quaternary loess in the Chinese Loess Plateau, show a positive relationship between them. In this note, we propose a convenient and effective approach for identifying the polluted soils.

  16. Magnetic properties of friction stir processed composite

    Energy Technology Data Exchange (ETDEWEB)

    Das, Shamiparna; Martinez, Nelson Y.; Das, Santanu; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep; Polikarpov, Evgueni

    2016-03-29

    There are many existing inspection systems each with their own advantages and drawbacks. These usually comprise of semi-remote sensors which frequently causes difficulty in reaching complex areas of a component. This study proposes to overcome that difficulty by developing embedded functional composites. Through this route, embedding can be achieved in virtually any component part and can be periodically interrogated by a reading device. The “reinforcement rich” processed areas can then be utilized to record properties like strain, temperature, stress state etc. depending on the reinforcement material. In this work, friction stir processing (FSP) was utilized to fabricate a magnetostrictive composite by embedding galfenol particles into a nonmagnetic aluminum (Al) matrix. It targets to develop a composite that produces strain in a varying magnetic field. Reinforcements were observed to be distributed uniformly in the matrix. Magnetization curves were studied using a vibrating sample magnetometer (VSM). A simple and cheap setup was developed to measure the magnetostrictive strain of the composites. Important factors affecting the magnetic properties were identified and ways to improve the magnetic properties discussed.

  17. Structure and Magnetic Properties of Lanthanide Nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Dickerson, James Henry [Vanderbilt Univ., Nashville, TN (United States)

    2014-06-01

    We have had considerable success on this project, particularly in the understanding of the relationship between nanostructure and magnetic properties in lanthanide nanocrystals. We also have successfully facilitated the doctoral degrees of Dr. Suseela Somarajan, in the Department of Physics and Astronomy, and Dr. Melissa Harrison, in the Materials Science Program. The following passages summarize the various accomplishments that were featured in 9 publications that were generated based on support from this grant. We thank the Department of Energy for their generous support of our research efforts in this area of materials science, magnetism, and electron microscopy.

  18. Usefulness of combining gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging and contrast-enhanced ultrasound for diagnosing the macroscopic classification of small hepatocellular carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Tomoki; Aikata, Hiroshi; Hatooka, Masahiro; Morio, Kei; Morio, Reona; Kan, Hiromi; Fujino, Hatsue; Fukuhara, Takayuki; Masaki, Keiichi; Ohno, Atsushi; Naeshiro, Noriaki; Nakahara, Takashi; Honda, Yohji; Murakami, Eisuke; Kawaoka, Tomokazu; Tsuge, Masataka; Hiramatsu, Akira; Imamura, Michio; Kawakami, Yoshiiku; Hyogo, Hideyuki; Takahashi, Shoichi [Hiroshima University Hospital, Department of Gastroenterology and Metabolism, Hiroshima (Japan); Chayama, Kazuaki [Hiroshima University Hospital, Department of Gastroenterology and Metabolism, Hiroshima (Japan); Hiroshima University, Liver Research Project Center, Hiroshima (Japan)

    2015-11-15

    Non-simple nodules in hepatocellular carcinoma (HCC) correlate with poor prognosis. Therefore, we examined the diagnostic ability of gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid-enhanced magnetic resonance imaging (EOB-MRI) and contrast-enhanced ultrasound (CEUS) for diagnosing the macroscopic classification of small HCCs. A total of 85 surgically resected nodules (≤30 mm) were analyzed. HCCs were pathologically classified as simple nodular (SN) and non-SN. By evaluating hepatobiliary phase (HBP) of EOB-MRI and Kupffer phase of CEUS, the diagnostic abilities of both modalities to correctly distinguish between SN and non-SN were compared. Forty-six nodules were diagnosed as SN and the remaining 39 nodules as non-SN. The area under the ROC curve (AUROCs, 95 % confidence interval) for the diagnosis of non-SN were EOB-MRI, 0.786 (0.682-0.890): CEUS, 0.784 (0.679-0.889), in combination, 0.876 (0.792-0.959). The sensitivity, specificity, and accuracy were 64.1 %, 95.7 %, and 81.2 % in EOB-MRI, 56.4 %, 97.8 %, and 78.8 % in CEUS, and 84.6 %, 95.7 %, and 90.6 % in combination, respectively. High diagnostic ability was obtained when diagnosed in both modalities combined. The sensitivity was especially statistically significant compared to CEUS. Combined diagnosis by EOB-MRI and CEUS can provide high-quality imaging assessment for determining non-SN in small HCCs. (orig.)

  19. Microwave absorbing properties and magnetic properties of different carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.

  20. Microwave absorbing properties and magnetic properties of different carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    GUI XuChun; WANG KunLin; WEI JinQuan; L(U) RuiTao; SHU QinKe; JIA Yi; WANG Chen; ZHU HongWei; WU DeHai

    2009-01-01

    The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires.After annealing, the values increased to 291.00e and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.

  1. Magnetic properties of Ni substituted Y-type barium ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Won, Mi Hee; Kim, Chul Sung, E-mail: cskim@kookmin.ac.kr [Department of Physics, Kookmin University, Seoul 136-702 (Korea, Republic of)

    2014-05-07

    Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba{sub 2}Co{sub 2−x}Ni{sub x}Fe{sub 12}O{sub 22} (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (M{sub s}) decreases with Ni contents. Ni{sup 2+}, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co{sup 2+} having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba{sub 2}Co{sub 1.5}Ni{sub 0.5}Fe{sub 12}O{sub 22} shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature T{sub C} is increased with Ni contents, while T{sub S} is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3b{sub VI}, 6c{sub IV}*, 6c{sub VI}, 18h{sub VI}, 6c{sub IV}, and 3a{sub IV} sites at below T{sub C}. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe{sup 3+} and obtained the isomer shift (δ), magnetic hyperfine field (H{sub hf}), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna

  2. Magnetic properties of Ni substituted Y-type barium ferrite

    Science.gov (United States)

    Won, Mi Hee; Kim, Chul Sung

    2014-05-01

    Y-type barium hexaferrite is attractive material for various applications, such as high frequency antennas and RF devices, because of its interesting magnetic properties. Especially, Ni substituted Y- type hexaferrites have higher magnetic ordering temperature than other Y-type. We have investigated macroscopic and microscopic properties of Y-type barium hexaferrite. Ba2Co2-xNixFe12O22 (x = 0, 0.5, 1.0, 1.5, and 2.0) samples are prepared by solid-state reaction method and studied by X-ray diffraction (XRD), vibrating sample magnetometer, and Mössbauer spectroscopy, as well as a network analyzer for high frequency characteristics. The XRD pattern is analyzed by Rietveld refinement method and confirms the hexagonal structure with R-3m. The hysteresis curve shows ferrimagnetic behavior. Saturation magnetization (Ms) decreases with Ni contents. Ni2+, which preferentially occupies the octahedral site with up-spin sub-lattice, has smaller spin value S of 1 than Co2+ having S = 3/2. The zero-field-cooled (ZFC) measurement of Ba2Co1.5Ni0.5Fe12O22 shows that Curie and spin transition temperatures are found to be 718 K and 209 K, respectively. The Curie temperature TC is increased with Ni contents, while TS is decreased with Ni. The Mössbauer spectra were measured at various temperatures and fitted by using a least-squares method with six sextet of six Lorentzian lines for Fe sites, corresponding to the 3bVI, 6cIV*, 6cVI, 18hVI, 6cIV, and 3aIV sites at below TC. From Mössbauer measurements, we confirmed the spin state of Fe ion to be Fe3+ and obtained the isomer shift (δ), magnetic hyperfine field (Hhf), and the occupancy ratio of Fe ions at six sub-lattices. The complex permeability and permittivity are measured between 100 MHz and 4 GHz, suggesting that Y-type barium hexaferrite is promising for antenna applications in UHF band.

  3. Interference of macroscopic superpositions

    CERN Document Server

    Vecchi, I

    2000-01-01

    We propose a simple experimental procedure based on the Elitzur-Vaidman scheme to implement a quantum nondemolition measurement testing the persistence of macroscopic superpositions. We conjecture that its implementation will reveal the persistence of superpositions of macroscopic objects in the absence of a direct act of observation.

  4. Three-dimensional Fe3O4-graphene macroscopic composites for arsenic and arsenate removal.

    Science.gov (United States)

    Guo, Liangqia; Ye, Peirong; Wang, Jing; Fu, Fengfu; Wu, Zujian

    2015-11-15

    3D graphene macroscopic gel synthesized via self-assembly of GO nanosheets under basic conditions at low temperature is modified with polydopamine and Fe3O4 nanoparticles. The modification of polydopamine can not only strengthen the 3D graphene-based macroscopic architecture but also enhance the loadage and binding ability of Fe3O4 nanoparticles. The synthesized 3D Fe3O4-graphene macroscopic composites are characterized by SEM, XRD, XPS, BET, Raman and magnetic property and used as a versatile adsorbent for sub-ppm concentration of As(III) and As(V) removal from aqueous solutions. The experimental results suggest that the synthesized 3D Fe3O4-graphene macroscopic composites are promising for treating low concentration of arsenic contaminated water. Copyright © 2015 Elsevier B.V. All rights reserved.

  5. General properties of magnetic CP stars

    Science.gov (United States)

    Glagolevskij, Yu. V.

    2017-07-01

    We present the review of our previous studies related to observational evidence of the fossil field hypothesis of formation and evolution of magnetic and non-magnetic chemically peculiar stars. Analysis of the observed data shows that these stars acquire their main properties in the process of gravitational collapse. In the non-stationary Hayashi phase, a magnetic field becomes weakened and its configuration complicated, but the fossil field global orientation remains. After a non-stationary phase, relaxation of young star's tangled field takes place and by the time of joining ZAMS (Zero Age Main Sequence) it is generally restored to a dipole structure. Stability of dipole structures allows them to remain unchanged up to the end of their life on the Main Sequence which is 109 years at most.

  6. Synthesis and Properties of Magnetic Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Sixin LI; Jiancheng ZHANG; Yue SHEN; Bo NI; Jingang ZHANG

    2006-01-01

    The uniform mesoporous SBA-15 consisting of SiO2 with long-range channels offers an excellent host material to synthesize or assemble the magnetic nanocomposites, such as Fe, Ni.In this paper, highly dispersed and uniform iron nanoparticles were incorporated into the pore channels of SBA-15 through a newly developed strategy in which some kinds of coupling agents were used to entrap the nanoparticles into the silica framework.The X-ray diffraction(XRD), fourier transmission infrared spectroscopy(FTIR), high-resolution transmission electronic microscopy(HRTEM)and energy dispersive X-ray spectroscopy(EDX)were performed to further identify the successful incorporation and grafting of iron. Compared with other ordinary non-assembled magnetic nanoparticles, the assembled Fe nanoparticles with the diameter even in the size range of 5~6 nm still have better magnetic properties.

  7. Magnetic properties of artificially synthesized ferritins

    Science.gov (United States)

    Kim, B. J.; Lee, H. I.; Cho, S.-B.; Yoon, S.; Suh, B. J.; Jang, Z. H.; St. Pierre, T. G.; Kim, S.-W.; Kim, K.-S.

    2005-05-01

    Human ferritin homopolymers with H or L subunits (rHF and rLF) were genetically engineered in E coli. Apoferritins were then reconstituted with 2000 Fe atoms. A big difference was observed in the rates of iron uptake, whereas the mean core size was similar in rHF and rLF. Magnetization of the recombinant human ferritins were measured as functions of temperature and field. The blocking temperature TB(H) at low fields is considerably higher in rLF than in rHF. From the fit of M(H ) data to a modified Langevin function: M(H )=M0L(μpH/kBT)+χaH, the effective magnetic moment μp is found to be much larger in rLF than in rHF. Experimental data demonstrate that the magnetic properties, in particular, the uncompensated spins of ferritin core are related to the biomineralization process in ferritins.

  8. Magnetic Properties of Nanoparticles of Antiferromagnetic Materials

    DEFF Research Database (Denmark)

    Mørup, Steen; Frandsen, Cathrine; Bødker, Franz

    2003-01-01

    The magnetic properties of antiferromagnetic nanoparticles have been studied by Mossbauer spectroscopy and neutron scattering. Temperature series of Mossbauer spectra of non-interacting, superparamagnetic hematite nanoparticles were fitted by use of the Blume-Tjon relaxation model. It has been...... found that the magnetic anisotropy energy constant increases significantly with decreasing particle size. Neutron scattering experiments on similar samples give new information on both superparamagnetic relaxation and collective magnetic excitations. There is good agreement between the values...... of the parameters obtained from Mossbauer spectroscopy and neutron scattering. In samples of interacting hematite nanoparticles, the relaxation was significantly suppressed. The Mossbauer data for these samples are in accordance with a mean field model for an ordered state of strongly interacting particles. Mixing...

  9. Low-macroscopic field emission properties of wide bandgap copper aluminium oxide nanoparticles for low-power panel applications.

    Science.gov (United States)

    Banerjee, Arghya Narayan; Joo, Sang W

    2011-09-07

    Field emission properties of CuAlO(2) nanoparticles are reported for the first time, with a low turn-on field of approximately 2 V µm(-1) and field enhancement factor around 230. The field emission process follows the standard Fowler-Nordheim tunnelling of cold electron emission. The emission mechanism is found to be a combination of low electron affinity, internal nanostructure and large field enhancement at the low-dimensional emitter tips of the nanoparticles. The field emission properties are comparable to the conventional carbon-based field emitters, and thus can become alternative candidate for field emission devices for low-power panel applications.

  10. Magnetic Properties of Friction Stir Processed Composite

    Science.gov (United States)

    Das, Shamiparna; Martinez, Nelson Y.; Das, Santanu; Mishra, Rajiv S.; Grant, Glenn J.; Jana, Saumyadeep; Polikarpov, Evgueni

    2016-07-01

    Of the many existing inspection or monitoring systems, each has its own advantages and drawbacks. These systems are usually comprised of semi-remote sensors that frequently cause difficulty in reaching complex areas of a component. This study proposes to overcome that difficulty by developing embedded functional composites, so that embedding can be achieved in virtually any component part and periodically can be interrogated by a reading device. The "reinforcement rich" processed areas can then be used to record properties such as strain, temperature, and stress state, to name a few, depending on the reinforcement material. Friction stir processing was used to fabricate a magnetostrictive composite by embedding galfenol particles into a nonmagnetic aluminum matrix. The aim was to develop a composite that produces strain in response to a varying magnetic field. Reinforcements were distributed uniformly in the matrix. Magnetization curves were studied using a vibrating sample magnetometer. A simple and cost-effective setup was developed to measure the magnetostrictive strain of the composites. Important factors affecting the magnetic properties were identified and the processing route was modified to improve the magnetic response.

  11. Magnetic properties of colloidal cobalt nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Torchio, R; Meneghini, C; Mobilio, S; Capellini, G [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Prieto, A Garcia; Alonso, J; Fdez-Gubieda, M L [Departamento de Electricidad y Electronica y Fisica Aplicada I, Universidad del PaIs Vasco (Spain); Liveri, V Turco; Ruggirello, A M [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Longo, A [ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo (Italy); Neisius, T, E-mail: torchio@fis.uniroma3.i [Universite Paul CEZANNE, Faculte des Sciences et Techniques, Marseille (France)

    2010-01-01

    Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co{sub 3}O{sub 4}with metallic Co and some Co{sup 2+} bound to the surfactant. The presence of antiferromagnetic Co{sub 3}O{sub 4} explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

  12. Characterization of the magnetic micro- and nanostructure in unalloyed steels by magnetic force microscopy

    Science.gov (United States)

    Batista, L.; Rabe, U.; Hirsekorn, S.

    2013-01-01

    The formation of a cementite phase influences significantly the macroscopic mechanical and magnetic properties of steels. Based on a correlation between mechanical and magnetic properties, mechanical properties as well as the morphology and content of the cementite phase can be inspected by electromagnetic non-destructive testing methods. The influence of the carbon content on bulk magnetic properties of unalloyed steels is studied on a macroscopic scale by hysteresis loop and Barkhausen noise measurements. The micro- and nanostructure is investigated by atomic force microscopy and magnetic force microscopy. Surface topography images and magnetic images of globular cementite precipitates embedded in a ferrite matrix are presented. The size, shape, and orientation of the precipitates influence the domain configuration. Applied external magnetic fields cause magnetization processes mainly in the ferrite matrix: Bloch walls move and are pinned by the cementite precipitates. The correlation between the microscopic observations and macroscopic magnetic properties of the material is discussed.

  13. Continuum cavity expansion and discrete micromechanical models for inferring macroscopic snow mechanical properties from cone penetration data

    Science.gov (United States)

    Ruiz, Siul; Capelli, Achille; van Herwijnen, Alec; Schneebeli, Martin; Or, Dani

    2017-08-01

    Digital cone penetration measurements can be used to infer snow mechanical properties, for instance, to study snow avalanche formation. The standard interpretation of these measurements is based on statistically inferred micromechanical interactions between snow microstructural elements and a well-calibrated penetrating cone. We propose an alternative continuum model to derive the modulus of elasticity and yield strength of snow based on the widely used cavity expansion model in soils. We compare results from these approaches based on laboratory cone penetration measurements in snow samples of different densities and structural sizes. Results suggest that the micromechanical model underestimates the snow elastic modulus for dense samples by 2 orders of magnitude. By comparison with the cavity expansion-based model, some of the discrepancy is attributed to low sensitivity of the micromechanical model to the snow elastic modulus. Reasons and implications of this discrepancy are discussed, and possibilities to enhance both methodologies are proposed.

  14. Large-scale structure of a network of co-occurring MeSH terms: statistical analysis of macroscopic properties.

    Science.gov (United States)

    Kastrin, Andrej; Rindflesch, Thomas C; Hristovski, Dimitar

    2014-01-01

    Concept associations can be represented by a network that consists of a set of nodes representing concepts and a set of edges representing their relationships. Complex networks exhibit some common topological features including small diameter, high degree of clustering, power-law degree distribution, and modularity. We investigated the topological properties of a network constructed from co-occurrences between MeSH descriptors in the MEDLINE database. We conducted the analysis on two networks, one constructed from all MeSH descriptors and another using only major descriptors. Network reduction was performed using the Pearson's chi-square test for independence. To characterize topological properties of the network we adopted some specific measures, including diameter, average path length, clustering coefficient, and degree distribution. For the full MeSH network the average path length was 1.95 with a diameter of three edges and clustering coefficient of 0.26. The Kolmogorov-Smirnov test rejects the power law as a plausible model for degree distribution. For the major MeSH network the average path length was 2.63 edges with a diameter of seven edges and clustering coefficient of 0.15. The Kolmogorov-Smirnov test failed to reject the power law as a plausible model. The power-law exponent was 5.07. In both networks it was evident that nodes with a lower degree exhibit higher clustering than those with a higher degree. After simulated attack, where we removed 10% of nodes with the highest degrees, the giant component of each of the two networks contains about 90% of all nodes. Because of small average path length and high degree of clustering the MeSH network is small-world. A power-law distribution is not a plausible model for the degree distribution. The network is highly modular, highly resistant to targeted and random attack and with minimal dissortativity.

  15. Hygroscopic properties of magnetic recording tape

    Science.gov (United States)

    Cuddihy, E. F.

    1976-01-01

    Relative humidity has been recognized as an important environmental factor in many head-tape interface phenomena such as headwear, friction, staining, and tape shed. Accordingly, the relative humidity is usually specified in many applications of tape use, especially when tape recorders are enclosed in hermetically sealed cases. Normally, the relative humidity is believed regulated by humidification of the fill gas to the specification relative humidity. This study demonstrates that the internal relative humidity in a sealed case is completely controlled by the time-dpendence of the hygroscopic properties of the pack of magnetic recording tape. Differences are found in the hygroscopic properties of the same brand of tape, which apparently result from aging, and which may have an effect on the long-term humidity-regulating behavior in a sealed case, and on the occurrence of head-tape interface phenomena from the long-term use of the tape. Results are presented on the basic hygroscopic properties of magnetic tape, its humidity-regulating behavior in a sealed case, and a theoretical commentary on the relative humidity dependence of head-wear by tape, is included.

  16. Effect of surfactant for magnetic properties of iron oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Haracz, S. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Hilgendorff, M. [Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany); Rybka, J.D. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Giersig, M. [Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89B, 61-614 Poznań (Poland); Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin (Germany)

    2015-12-01

    Highlights: • Dynamic behavior of magnetic nanoparticles. • Synthesis of iron oxide nanoparticles. • Effect of surfactant for magnetic properties. - Abstract: For different medical applications nanoparticles (NPs) with well-defined magnetic properties have to be used. Coating ligand can change the magnetic moment on the surface of nanostructures and therefore the magnetic behavior of the system. Here we investigated magnetic NPs in a size of 13 nm conjugated with four different kinds of surfactants. The surface anisotropy and the magnetic moment of the system were changed due to the presence of the surfactant on the surface of iron oxide NPs.

  17. Mechanochemical synthesis and magnetic properties of maghemite

    Directory of Open Access Journals (Sweden)

    Marin M. Tadić

    2011-07-01

    Full Text Available This work presents the results of an investigation on maghemite (γ -Fe2O3 nanoparticles magnetic properties, which show superparamagnetic behavior i.e. superparamagnetism. Nanoscale maghemite samples were obtained by the mechanochemical method. The crystal structure of the samples was analyzed by the electron diffraction and the X-ray powder diffraction. The formation of monophase maghemite was shown. The particle size was determined by the transmission electron microscopy (TEM. The shift of the blockage temperature TB towards lower values with increasing field strength is significant, which is the indication of the superparamagnetism in the system under consideration.

  18. Permanent magnets including undulators and wigglers

    OpenAIRE

    Bahrdt, J.

    2011-01-01

    After a few historic remarks on magnetic materials we introduce the basic definitions related to permanent magnets. The magnetic properties of the most common materials are reviewed and the production processes are described. Measurement techniques for the characterization of macroscopic and microscopic properties of permanent magnets are presented. Field simulation techniques for permanent magnet devices are discussed. Today, permanent magnets are used in many fields. This article concentrat...

  19. Modelling dielectric and magnetic properties of ferroconcrete

    Directory of Open Access Journals (Sweden)

    T. Frenzel

    2008-05-01

    Full Text Available This contribution discusses the modelling and parameterization of dielectric and magnetic properties of ferroconcrete by using numerical electromagnetic field analysis software. The software is based on the Method of Moments (MoM. The shielding effectiveness (SE of the ferroconcrete DUT was already measured in a study by order of the government. According to these results, the ferroconcrete DUT is modelled and calculated. Therefore the DUT is subdivided into two parts. The first part represents the reinforcement mesh; the second part represents the lossy concrete with complex permittivity. Afterwards, the reflection and transmission properties of numerical analysed building materials are validated and compared with the measurement results in a frequency range of 30–1000 MHz.

  20. Structural and Magnetic Properties of Trigonal Iron

    CERN Document Server

    Fox, S

    1995-01-01

    First principles calculations of the electronic structure of trigonal iron were performed using density function theory. The results are used to predict lattice spacings, magnetic moments and elastic properties; these are in good agreement with experiment for both the bcc and fcc structures. We find however, that in extracting these quantities great care must be taken in interpreting numerical fits to the calculated total energies. In addition, the results for bulk iron give insight into the properties of thin iron films. Thin films grown on substrates with mismatched lattice constants often have non-cubic symmetry. If they are thicker than a few monolayers their electronic structure is similar to a bulk material with an appropriately distorted geometry, as in our trigonal calculations. We recast our bulk results in terms of an iron film grown on the (111) surface of an fcc substrate, and find the predicted strain energies and moments accurately reflect the trends for iron growth on a variety of substrates.

  1. Magnetic colloid by PLA: Optical, magnetic and thermal transport properties

    Science.gov (United States)

    Pandey, B. K.; Shahi, A. K.; Gopal, Ram

    2015-08-01

    Ferrofluids of cobalt and cobalt oxide nanoparticles (NPs) have been successfully synthesized using liquid phase-pulse laser ablation (LP-PLA) in ethanol and double distilled water, respectively. The mechanism of laser ablation in liquid media and formation process for Co target in double distilled water (DDW) and ethanol are speculated based on the reactions between laser generated highly nascent cobalt species and vaporized solvent media in a confined high temperature and pressure at the plume-surrounding liquid interface region. Optical absorption, emission, vibrational and rotational properties have been investigated using UV-vis absorption, photoluminescence (PL) and Fourier transform-infra red (FT-IR) spectroscopy, respectively. In this study optical band gap of cobalt oxide ferrofluids has been engineered using different pulse energy of Nd:YAG laser in the range of (2.80-3.60 eV). Vibrating sample magnetometer (VSM) is employed to determine the magnetic properties of ferrofluids of cobalt and cobalt oxide NPs while their thermal conductivities are examined using rotating disc method. Ferrofluids have gained enormous curiosity due to many technological applications, i.e. drug delivery, coolant and heating purposes.

  2. Macroscopic quantum resonators (MAQRO)

    CERN Document Server

    Kaltenbaek, Rainer; Kiesel, Nikolai; Romero-Isart, Oriol; Johann, Ulrich; Aspelmeyer, Markus

    2012-01-01

    Quantum physics challenges our understanding of the nature of physical reality and of space-time and suggests the necessity of radical revisions of their underlying concepts. Experimental tests of quantum phenomena involving massive macroscopic objects would provide novel insights into these fundamental questions. Making use of the unique environment provided by space, MAQRO aims at investigating this largely unexplored realm of macroscopic quantum physics. MAQRO has originally been proposed as a medium-sized fundamental-science space mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments: DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative Acceleration Sensing Experiment). The main scientific objective of MAQRO, which is addressed by the experiment DECIDE, is to test the predictions of quantum theory for quantum superpositions of macroscopic objects containing more than 10e8 atoms. Under these conditions, deviations due to various suggested alternative models to quantum th...

  3. Magnetic Properties of Ni Nanoparticles and Ni(C) Nanocapsules

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Structure and magnetic properties of Ni nanoparticles and Ni(C) nanocapsules were studied. The carbon atoms hardly affect the lattice of Ni to form Ni-C solid solution or nickel carbides. The large thermal irreversibility in zerofield-cooled and zero-field magnetization curves indicates magnetic blocking with a wide energy barrier. Saturation magnetization, remanent magnetization and coercivity of Ni(C) nanocapsules decrease with increasing temperature.

  4. Magnetic nanoparticles and concentrated magnetic nanofluids: Synthesis, properties and some applications

    Institute of Scientific and Technical Information of China (English)

    Ladislau Vékás; Doina Bica; Mikhail V. Avdeev

    2007-01-01

    This paper reviews some recent results concerning chemical synthesis of magnetic nanoparticles and preparation of various types of magnetic nanofluids. Structural properties and behaviour in external magnetic field of magnetic nanofluids will be emphasized with relation to their use in leakage-free rotating seals and in biomedical applications.

  5. Obtaining Magnetic Properties of Meteorites Using Magnetic Scanner

    Science.gov (United States)

    Kletetschka, G.; Nabelek, L.; Mazanec, M.; Simon, K.; Hruba, J.

    2015-12-01

    Magnetic images of Murchison meteorite's and Chelyabinsk meteorite's thin section have been obtained from magnetic scanning system from Youngwood Science and Engineering (YSE) capable of resolving magnetic anomalies down to 10-3 mT range from about 0.3 mm distance between the probe and meteorite surface (resolution about 0.15 mm). Anomalies were produced repeatedly, each time after application of magnetic field pulse of varying amplitude and constant, normal or reversed, direction. This process resulted in both magnetizing and demagnetizing of the meteorite thin section, while keeping the magnetization vector in the plane of the thin section. Analysis of the magnetic data allows determination of coercivity of remanence (Bcr) for the magnetic sources in situ. Value of Bcr is critical for calculating magnetic forces applicable during missions to asteroids where gravity is compromised. Bcr was estimated by two methods. First method measured varying dipole magnetic field strength produced by each anomaly in the direction of magnetic pulses. Second method measured deflections of the dipole direction from the direction of magnetic pulses (Nabelek et al., 2015). Nabelek, L., Mazanec, M., Kdyr, S., and Kletetschka, G., 2015, Magnetic, in situ, mineral characterization of Chelyabinsk meteorite thin section: Meteoritics & Planetary Science.

  6. Kagome network compounds and their novel magnetic properties.

    Science.gov (United States)

    Pati, Swapan K; Rao, C N R

    2008-10-21

    Compounds possessing the Kagome network are truly interesting because of their unusual low-energy properties. They exhibit magnetic frustration because of the triangular lattice inherent to the hexagonal bronze structure they possess, as indeed demonstrated by some of the Fe(3+) jarosites, but this is not the general case. Kagome compounds formed by transition metal ions with varying spins exhibit novel magnetic properties, some even showing evidence for magnetic order and absence of frustration. We describe the structure and magnetic properties of this interesting class of materials and attempt to provide an explanation for the variety of properties on the basis of theoretical considerations.

  7. Magnetic properties of ultra-small goethite nanoparticles

    DEFF Research Database (Denmark)

    Brok, Erik; Frandsen, Cathrine; Madsen, Daniel Esmarch

    2014-01-01

    Goethite (α-FeOOH) is a common nanocrystalline antiferromagnetic mineral. However, it is typically difficult to study the properties of isolated single-crystalline goethite nanoparticles, because goethite has a strong tendency to form particles of aggregated nanograins often with low-angle grain...... boundaries. This nanocrystallinity leads to complex magnetic properties that are dominated by magnetic fluctuations in interacting grains. Here we present a study of the magnetic properties of 5.7 nm particles of goethite by use of magnetization measurements, inelastic neutron scattering and Mo......¨ssbauer spectroscopy. The `ultra-small' size of these particles (i.e. that the particles consist of one or only a few grains) allows for more direct elucidation of the particles' intrinsic magnetic properties. We find from ac and dc magnetization measurements a significant upturn of the magnetization at very low...

  8. Optimization of the magnetic properties of nanostructured Y-Co-Fe alloys for permanent magnets

    Directory of Open Access Journals (Sweden)

    P. Tozman

    2016-05-01

    Full Text Available The structural and magnetic properties of ball-milled Fe-doped Y Co5−xFex(0 ≤ x ≤ 0.5 were investigated. The magnetization increases with Fe-doping up to the solid solubility limit, x = 0.3 without destroying the crystal structure or degrading the coercivity. A special magnet array is designed using ring magnets for pressing the powders under magnetic field in order to achieve magnetic alignment. A dramatic increase in magnetization is observed for magnetically aligned Y Co4.8Fe0.2 pressed ingots.

  9. Determination of magnetic properties of multilayer metallic thin films

    CERN Document Server

    Birlikseven, C

    2000-01-01

    and magnetization measurements were taken. In recent year, Giant Magnetoresistance Effect has been attracting an increasingly high interest. High sensitivity magnetic field detectors and high sensitivity read heads of magnetic media can be named as important applications of these films. In this work, magnetic and electrical properties of single layer and thin films were investigated. Multilayer thin films were supplied by Prof. Dr. A. Riza Koeymen from Texas University. Multilayer magnetic thin films are used especially for magnetic reading and magnetic writing. storing of large amount of information into small areas become possible with this technology. Single layer films were prepared using the electron beam evaporation technique. For the exact determination of film thicknesses, a careful calibration of the thicknesses was made. Magnetic properties of the multilayer films were studied using the magnetization, magnetoresistance measurements and ferromagnetic resonance technique. Besides, by fitting the exper...

  10. Numerical calculations of magnetic properties of nanostructures

    CERN Document Server

    Kapitan, Vitalii; Nefedev, Konstantin

    2015-01-01

    Magnetic force microscopy and scanning tunneling microscopy data could be used to test computer numerical models of magnetism. The elaborated numerical model of a face-centered lattice Ising spins is based on pixel distribution in the image of magnetic nanostructures obtained by using scanning microscope. Monte Carlo simulation of the magnetic structure model allowed defining the temperature dependence of magnetization; calculating magnetic hysteresis curves and distribution of magnetization on the surface of submonolayer and monolayer nanofilms of cobalt, depending on the experimental conditions. Our developed package of supercomputer parallel software destined for a numerical simulation of the magnetic-force experiments and allows obtaining the distribution of magnetization in one-dimensional arrays of nanodots and on their basis. There has been determined interpretation of magneto-force microscopy images of magnetic nanodots states. The results of supercomputer simulations and numerical calculations are in...

  11. Magnetic Properties of AIIBIVCV2 Compounds Doped with Mn

    Directory of Open Access Journals (Sweden)

    A.V. Kochura

    2013-12-01

    Full Text Available Mn-doped AIIBIVCV2 semiconductors bulk crystals were grown by direct melting of base components with fast cooling. Structural and magnetic properties of samples were investigated. Analysis of the temperature dependence of the magnetization reveals three types of magnetic species: the substitutional Mn ions making Mn complexes (especially dimers, the MnAs micro- and nanosize precepitates.

  12. Magnetic twist: a source and property of space weather

    Directory of Open Access Journals (Sweden)

    Mitra Dhrubaditya

    2012-08-01

    Full Text Available Aim: We present evidence for finite magnetic helicity density in the heliosphere and numerical models thereof, and relate it to the magnetic field properties of the dynamo in the solar convection zone. Methods: We use simulations and solar wind data to compute magnetic helicity either directly from the simulations or indirectly using time series of the skew-symmetric components of the magnetic correlation tensor. Results: We find that the solar dynamo produces negative magnetic helicity at small scales and positive at large scales. However, in the heliosphere these properties are reversed and the magnetic helicity is now positive at small scales and negative at large scales. We explain this by the fact that a negative diffusive magnetic helicity flux corresponds to a positive gradient of magnetic helicity, which leads to a change of sign from negative to positive values at some radius in the northern hemisphere.

  13. Overview of Planar Magnetic Technology — Fundamental Properties

    DEFF Research Database (Denmark)

    Ouyang, Ziwei; Andersen, Michael A. E.

    2014-01-01

    The momentum towards high efficiency, high frequency, and high power density in power supplies limits wide use of conventional wire-wound magnetic components. This article gives an overview of planar magnetic technologies with respect to the development of modern power electronics. The major...... advantages and disadvantages in the use of planar magnetics for high frequency power converters are covered, and publications on planar magnetics are reviewed. A detailed survey of winding conduction loss, leakage inductance and winding capacitance for planar magnetics is presented so power electronics...... engineers and researchers can have a clear understanding of the intrinsic properties of planar magnetics....

  14. Magnetic Properties of Heisenberg Thin Films in an External Field

    Institute of Scientific and Technical Information of China (English)

    CHEN Hong; ZHANG Jing

    2004-01-01

    The magnetic properties of Heisenberg ferromagnetic films in an external magnetic field are investigated by means of the variational cumulant expansion (VCE). The magnetization can be in principle calculated analytically as the function of the temperature and the number of atomic layers in the film to an arbitrary order of accuracy in the VCE. We calculate the spontaneous magnetization and coercivity to the third order for spin-1/2 Heisenberg films with simple cubic lattices by using a graphic technique.

  15. Magnetic properties of CoO nanoparticles

    NARCIS (Netherlands)

    Flipse, CFJ; Rouwelaar, CB; de Groot, FMF

    1999-01-01

    The magnetic circular X-ray dichroism (MCXD) of CoO nanoparticles was measured at low temperatures and in high magnetic fields. The particles show a superparamagnetic behaviour at room temperature, and a large orbital contribution to the magnetic moment at low temperatures was observed. This enhance

  16. Electronic properties of magnetically doped nanotubes

    Indian Academy of Sciences (India)

    Keivan Esfarjani; Z Chen; Y Kawazoe

    2003-01-01

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

  17. Magnetic structures and properties of vanadium diiodide.

    NARCIS (Netherlands)

    Kuindersma, S. R.; Haas, C.; Sanchez, J. P.; Al, R.

    1979-01-01

    Single-crystal measurements of the magnetic susceptibilities of VI2 show an anomaly at a crit. temp. of ∼14 K. This anomaly can be ascribed to a magnetic phase transition from a 120° structure to a collinear arrangement of the spins with a magnetic unit cell amagn = a√3, bmagn = 2 a and cmagn = 2 c.

  18. Introducing artificial length scales to tailor magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Fassbender, J; Strache, T; Liedke, M O; Marko, D; Wintz, S; Lenz, K; Keller, A; Facsko, S [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, PO Box 51 01 19, D-01314 Dresden (Germany); Moench, I; McCord, J [Leibniz Institute for Solid State and Materials Research IFW Dresden, PO Box 27 01 16, D-01171 Dresden (Germany)], E-mail: J.Fassbender@fzd.de

    2009-12-15

    Magnetism is a collective phenomenon. Hence, a local variation on the nanoscale of material properties, which act on the magnetic properties, affects the overall magnetism in an intriguing way. Of particular importance are the length scales on which a material property changes. These might be related to the exchange length, the domain wall width, a typical roughness correlation length, or a length scale introduced by patterning of the material. Here we report on the influence of two artificially created length scales: (i) ion erosion templates that serve as a source of a predefined surface morphology (ripple structure) and hence allow for the investigation of roughness phenomena. It is demonstrated that the ripple wave length can be easily tuned over a wide range (25-175 nm) by varying the primary ion erosion energy. The effect of this ripple morphology on the induced uniaxial magnetic anisotropy in soft magnetic Permalloy films is studied. Only below a ripple wavelength threshold ({approx}60 nm) is a significant induced magnetic anisotropy found. Above this threshold the corrugated Permalloy film acts as a flat film. This cross-over is discussed in the frame of dipolar interactions giving rise to the induced anisotropies. (ii) Ion implantation through a lithographically defined mask, which is used for a magnetic property patterning on various length scales. The resulting magnetic properties are neither present in non-implanted nor in homogeneously implanted films. Here new insight is gained by the comparison of different stripe patterning widths ranging from 1 to 10 {mu}m. In addition, the appearance of more complicated magnetic domain structures, i.e. spin-flop domain configurations and head-on domain walls, during hard axis magnetization reversal is demonstrated. In both cases the magnetic properties, the magnetization reversal process as well as the magnetic domain configurations depend sensitively on the artificially introduced length scale.

  19. Random site dilution properties of frustrated magnets on a hierarchical lattice.

    Science.gov (United States)

    Fortin, Jean-Yves

    2013-07-24

    We present a method to analyze the magnetic properties of frustrated Ising spin models on specific hierarchical lattices with random dilution. Disorder is induced by dilution and geometrical frustration rather than randomness in the internal couplings of the original Hamiltonian. The two-dimensional model presented here possesses a macroscopic entropy at zero temperature in the large size limit, very close to the Pauling estimate for spin-ice on the pyrochlore lattice, and a crossover towards a paramagnetic phase. The disorder due to dilution is taken into account by considering a replicated version of the recursion equations between partition functions at different lattice sizes. An analysis to first order in replica number allows a systematic reorganization of the disorder configurations, leading to a recurrence scheme. This method is numerically implemented to evaluate thermodynamical quantities such as specific heat and susceptibility in an external field.

  20. Understanding the Pulsar High Energy Emission: Macroscopic and Kinetic Models

    Science.gov (United States)

    Kalapotharakos, Constantinos; Brambilla, Gabriele; Timokhin, Andrey; Kust Harding, Alice; Kazanas, Demos

    2017-08-01

    Pulsars are extraordinary objects powered by the rotation of magnetic fields of order 10^8, 10^12G anchored onto neutron stars and rotating with periods 10^(-3)-10s. These fields mediate the conversion of their rotational energy into MHD winds and at the same time accelerate particles to energies sufficiently high to produce GeV photons. Fermi, since its launch in 2008, has established several trends among the observed gamma-ray pulsar properties playing a catalytic role in the current modeling of the high energy emission in pulsar magnetospheres. We judiciously use the guidance provided by the Fermi data to yield meaningful constraints on the macroscopic parameters of our global dissipative pulsar magnetosphere models. Our FIDO (Force-Free Inside, Dissipative Outside) models indicate that the dissipative regions lie outside the light cylinder near the equatorial current sheet. Our models reproduce the light-curve phenomenology while a detailed comparison of the model spectral properties with those observed by Fermi reveals the dependence of the macroscopic conductivity parameter on the spin-down rate providing a unique insight into the understanding of the physical mechanisms behind the high-energy emission in pulsar magnetospheres. Finally, we further exploit these important results by building self-consistent 3D global kinetic particle-in-cell (PIC) models which, eventually, provide the dependence of the macroscopic parameter behavior (e.g. conductivity) on the microphysical properties (e.g. particle multiplicities, particle injection rates). Our PIC models provide field structures and particle distributions that are not only consistent with each other but also able to reproduce a broad range of the observed gamma-ray phenomenology (light curves and spectral properties) of both young and millisecond pulsars.

  1. Magnetism in nanoparticles: tuning properties with coatings.

    Science.gov (United States)

    Crespo, Patricia; de la Presa, Patricia; Marín, Pilar; Multigner, Marta; Alonso, José María; Rivero, Guillermo; Yndurain, Félix; González-Calbet, José María; Hernando, Antonio

    2013-12-04

    This paper reviews the effect of organic and inorganic coatings on magnetic nanoparticles. The ferromagnetic-like behaviour observed in nanoparticles constituted by materials which are non-magnetic in bulk is analysed for two cases: (a) Pd and Pt nanoparticles, formed by substances close to the onset of ferromagnetism, and (b) Au and ZnO nanoparticles, which were found to be surprisingly magnetic at the nanoscale when coated by organic surfactants. An overview of theories accounting for this unexpected magnetism, induced by the nanosize influence, is presented. In addition, the effect of coating magnetic nanoparticles with biocompatible metals, oxides or organic molecules is also reviewed, focusing on their applications.

  2. A macroscopic challenge for quantum spacetime

    CERN Document Server

    Amelino-Camelia, Giovanni

    2013-01-01

    Over the last decade a growing number of quantum-gravity researchers has been looking for opportunities for the first ever experimental evidence of a Planck-length quantum property of spacetime. These studies are usually based on the analysis of some candidate indirect implications of spacetime quantization, such as a possible curvature of momentum space. Some recent proposals have raised hope that we might also gain direct experimental access to quantum properties of spacetime, by finding evidence of limitations to the measurability of the center-of-mass coordinates of some macroscopic bodies. However I here observe that the arguments that originally lead to speculating about spacetime quantization do not apply to the localization of the center of mass of a macroscopic body. And I also analyze some popular formalizations of the notion of quantum spacetime, finding that when the quantization of spacetime is Planckian for the constituent particles then for the composite macroscopic body the quantization of spa...

  3. Nanoplasmon-enabled macroscopic thermal management

    CERN Document Server

    Jonsson, Gustav Edman; Dmitriev, Alexandre

    2013-01-01

    In numerous applications of energy harvesting via transformation of light into heat the focus recently shifted towards highly absorptive materials featuring nanoplasmons. It is currently established that noble metals-based absorptive plasmonic platforms deliver significant light-capturing capability and can be viewed as super-absorbers of optical radiation. However, direct experimental evidence of plasmon-enabled macroscopic temperature increase that would result from these efficient absorptive properties is scarce. Here we derive a general quantitative method of characterizing light-capturing properties of a given heat-generating absorptive layer by macroscopic thermal imaging. We further monitor macroscopic areas that are homogeneously heated by several degrees with plasmon nanostructures that occupy a mere 8% of the surface, leaving it essentially transparent and evidencing significant heat generation capability of nanoplasmon-enabled light capture. This has a direct bearing to thermophotovoltaics and othe...

  4. Magnetic and Electric Properties of , ( Layered Perovskites

    Directory of Open Access Journals (Sweden)

    A. I. Ali

    2013-01-01

    Full Text Available The electric and magnetic properties of layered perovskites have been investigated systematically over the doping range . It was found that both Sr1.5Y0.5CoO4 and Sr1.4Y0.6CoO4 undergo ferromagnetic (FM transition around 145 K and 120 K, respectively. On the other hand, Sr1.3Y0.7CoO4 and Sr1.2Y0.8CoO4 compounds showed paramagnetic behavior over a wide range of temperatures. In addition, spin-glass transition ( was observed at 10 K for Sr1.3Y0.7CoO4. All investigated samples are semiconducting-like within the temperature range of 10–300 K. The temperature dependence of the electrical resistivity, , was described by two-dimensional variable range hopping (2D-VRH model at 50 K < ≤ 300 K. Comparison with other layered perovskites was discussed in this work.

  5. Magnetic properties of hybrid elastomers with magnetically hard fillers: rotation of particles

    Science.gov (United States)

    Stepanov, G. V.; Borin, D. Yu; Bakhtiiarov, A. V.; Storozhenko, P. A.

    2017-03-01

    Hybrid magnetic elastomers belonging to the family of magnetorheological elastomers contain magnetically hard components and are of the utmost interest for the development of semiactive and active damping devices as well as actuators and sensors. The processes of magnetizing of such elastomers are accompanied by structural rearrangements inside the material. When magnetized, the elastomer gains its own magnetic moment resulting in changes of its magneto-mechanical properties, which remain permanent, even in the absence of external magnetic fields. Influenced by the magnetic field, magnetized particles move inside the matrix forming chain-like structures. In addition, the magnetically hard particles can rotate to align their magnetic moments with the new direction of the external field. Such an elastomer cannot be demagnetized by the application of a reverse field.

  6. Physical Properties of Ni2GeO4 Spinel Perturbed by Magnetic Dilution and Applied Pressure

    Science.gov (United States)

    Korobanik, Jory; Razavi, Fereidoon

    2014-03-01

    Geometrically frustrated magnetic systems have yielded an interesting and rich playground for physicists. Recently, a new disordered low temperature state was discovered in the frustrated pyrochlore type Ho2Ti2O7 which is termed spin ice. This phase is the magnetic analog to water ice with local spin disorder replacing proton disorder. Geometric frustration arises when nearest neighbor exchange interactions cannot be simultaneously satisfied resulting in large macroscopic degeneracy. This has the effect of suppressing Neel ordering temperature. This work seeks to understand the effects of applied pressure and magnetic dilution to the frustrated spinel Ni2GeO4. The parent material undergoes two closely spaced ordering events at T1 = 12.1K and T2 = 11.4K. Upon dilution a downward shift in the ordering temperatures is observed with a destruction of the lower T2 transition. Heat capacity, AC and DC magnetometry are used to probe the changes in physical properties.

  7. Photothermal investigation of local and depth dependent magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Pelzl, J; Meckenstock, R, E-mail: pelzl@fks.rub.d [Institute of Experimental Physics, Solid State Spectroscopy, Ruhr-University, D-44780 Bochum (Germany)

    2010-03-01

    To achieve a spatially resolved measurement of magnetic properties two different photothermal approaches are used which rely on heat dissipated by magnetic resonance absorption or thermal modulation of the magnetic properties, respectively. The heat produced by modulated microwave absorption is detected by the classical photothermal methods such as photoacoustic effect and mirage effect. Examples comprise depth resolution of the magnetization of layered tapes and visualisation of magnetic excitations in ferrites. The second photothermal technique relies on the local modulation of magnetic properties by a thermal wave generated with an intensity modulated laser beam incident on the sample. This technique has a higher spatial resolution and sensitivity and has been used to characterize lateral magnetic properties of multilayers and spintronic media. To extend the lateral resolution of the ferromagnetic resonance detection into the nm-range techniques have been developed which are based on the detection of the modulated thermal microwave response by the thermal probe of an atomic force microscope (AFM) or by detection the thermal expansion of the magnetic sample in the course of the resonant microwave absorption with an AFM or tunnelling microscope. These thermal near field based techniques in ferromagnetic resonance have been successfully applied to image magnetic inhomogeneities around nano-structures and to measure the ferromagnetic resonance from magnetic nano-dots.

  8. Soft-X-ray magnetic circular dichroism : a new technique for probing magnetic properties of magnetic surfaces and ultrathin films

    NARCIS (Netherlands)

    Tjeng, L.H.; Idzerda, Y.U.; Rudolf, P.; Sette, F.; Chen, C.T.

    1992-01-01

    We demonstrate the feasibility of applying the novel soft-X-ray magnetic circular dichroism (SXMCD) technique to investigate the magnetic properties of magnetic surfaces and uitrathin films. Measurements have been carried out on Ni films of various thickness on a Cu(100) substrate at the Ni L2,3 abs

  9. Macroscopic electromagnetic response of metamaterials with toroidal resonances

    CERN Document Server

    Savinov, V; Zheludev, N I

    2013-01-01

    Toroidal dipole, first described by Ia. B. Zeldovich [Sov. Phys. JETP 33, 1184 (1957)], is a distinct electromagnetic excitation that differs both from the electric and the magnetic dipoles. It has a number of intriguing properties: static toroidal nuclear dipole is responsible for parity violation in atomic spectra; interactions between static toroidal dipole and oscillating magnetic dipole are claimed to violate Newton's Third Law while non-stationary charge-current configurations involving toroidal multipoles have been predicted to produce vector potential in the absence of electromagnetic fields. Existence of the toroidal response in metamaterials was recently demonstrated and is now a growing field of research. However, no direct analytical link has yet been established between the transmission and reflection of macroscopic electromagnetic media and toroidal dipole excitations. To address this essential gap in electromagnetic theory we have developed an analytical approach linking microscopic and macrosc...

  10. Magnetic and Magneto-Optical Properties in Paramagnetic NdF3 Under High Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG Wei; LIU Gong-Qiang

    2005-01-01

    In this paper, we first theoretically report the magnetic and magneto-optical properties in paramagnetic media under high external magnetic field. Considering the action of the external magnetic field He and indirect exchange interaction Hv, the characteristic of the magnetic saturation and the property of the Faraday rotation to be nonlinear with external magnetic field are presented in paramagnetic NdF3. In terms of our theory, the indirect exchange interaction plays an important role in the magnetization M and the Faraday rotation θ in NdF3 under high external magnetic field. The theory is in good agreement with experimental results. On the other hand, a reasonable explanation for the temperature dependence of the ratio of the Verdet constant to the magnetic susceptibility V/x is obtained.

  11. Macroscopic Theory of Dark Sector

    Directory of Open Access Journals (Sweden)

    Boris E. Meierovich

    2014-01-01

    Full Text Available A simple Lagrangian with squared covariant divergence of a vector field as a kinetic term turned out to be an adequate tool for macroscopic description of the dark sector. The zero-mass field acts as the dark energy. Its energy-momentum tensor is a simple additive to the cosmological constant. Massive fields describe two different forms of dark matter. The space-like massive vector field is attractive. It is responsible for the observed plateau in galaxy rotation curves. The time-like massive field displays repulsive elasticity. In balance with dark energy and ordinary matter it provides a four-parametric diversity of regular solutions of the Einstein equations describing different possible cosmological and oscillating nonsingular scenarios of evolution of the Universe. In particular, the singular big bang turns into a regular inflation-like transition from contraction to expansion with the accelerated expansion at late times. The fine-tuned Friedman-Robertson-Walker singular solution is a particular limiting case at the lower boundary of existence of regular oscillating solutions in the absence of vector fields. The simplicity of the general covariant expression for the energy-momentum tensor allows displaying the main properties of the dark sector analytically. Although the physical nature of dark sector is still unknown, the macroscopic theory can help analyze the role of dark matter in astrophysical phenomena without resorting to artificial model assumptions.

  12. Magnetic properties of a doped graphene-like bilayer

    Energy Technology Data Exchange (ETDEWEB)

    Guo, An-Bang [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Jiang, Wei, E-mail: weijiang.sut.edu@gmail.com [School of Science, Shenyang University of Technology, Shenyang 110870 (China); Zhang, Na [Shenyang Normal University, Shenyang 110034 (China)

    2017-05-15

    A doped graphene-like bilayer is described using a four-sublattice Heisenberg model both ferromagnetic and antiferrimagnetic couplings. The magnetic properties of the bilayer system are studied using the Heisenberg model, retarded Green's function and the linear spin-wave approximation. The spin-wave spectra, energy gap, and the magnetization and quantum fluctuation of the system at the ground state are calculated with various intra- and interlayer couplings. The results indicate that the effect of antiferromagnetic exchange coupling on the magnetic properties of the system is significant. Magnetizations at low temperature show intersection points due to the quantum effects.

  13. Magnetic and magnetothermal properties and the magnetic phase diagram of high purity single crystalline terbium along the easy magnetization direction.

    Science.gov (United States)

    Zverev, V I; Tishin, A M; Chernyshov, A S; Mudryk, Ya; Gschneidner, K A; Pecharsky, V K

    2014-02-12

    The magnetic and magnetothermal properties of a high purity terbium single crystal have been re-investigated from 1.5 to 350 K in magnetic fields ranging from 0 to 75 kOe using magnetization, ac magnetic susceptibility and heat capacity measurements. The magnetic phase diagram has been refined by establishing a region of the fan-like phase broader than reported in the past, by locating a tricritical point at 226 K, and by a more accurate definition of the critical fields and temperatures associated with the magnetic phases observed in Tb.

  14. Magnetic Properties of Nd12Co6Pb Compound

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The magnetic and magnetocaloric properties for the Nd12Co6Pb compound were investigated. The Curie temperature TC of the magnetic transition of Nd12Co6Pb compound is 194 K. The experimentally determined magnetic effective paramagnetic moment is μeff=12.36 μB per formula unit (3.49 μB per Nd atom). The maximum magnetic entropy change in the low magnetic field changes of 0~2 T for the Nd12Co6Pb compound is about 215.0 J·mole-1·K-1.

  15. Enhancement in magnetic properties of magnesium substituted bismuth ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jianlong; Xie, Dan, E-mail: xiedan@mail.tsinghua.edu.cn, E-mail: RenTL@mail.tsinghua.edu.cn; Teng, Changjiu; Zhang, Xiaowen; Zhang, Cheng; Sun, Yilin; Ren, Tian-Ling, E-mail: xiedan@mail.tsinghua.edu.cn, E-mail: RenTL@mail.tsinghua.edu.cn [Institute of Microelectronics, Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); Zeng, Min; Gao, Xingsen [Institute for Advanced Materials and Laboratory of Quantum Engineering and Quantum Materials, South China Normal University, Guangzhou 510006 (China); Zhao, Yonggang [Department of Physics and State Key Laboratory of Low-Dimensional Quantum Physics, Tsinghua University, Beijing 100084 (China)

    2015-06-14

    We report a potential way to effectively improve the magnetic properties of BiFeO{sub 3} (BFO) nanoparticles through Mg{sup 2+} ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.

  16. Enhancement in magnetic properties of magnesium substituted bismuth ferrite nanoparticles

    Science.gov (United States)

    Xu, Jianlong; Xie, Dan; Teng, Changjiu; Zhang, Xiaowen; Zhang, Cheng; Sun, Yilin; Ren, Tian-Ling; Zeng, Min; Gao, Xingsen; Zhao, Yonggang

    2015-06-01

    We report a potential way to effectively improve the magnetic properties of BiFeO3 (BFO) nanoparticles through Mg2+ ion substitution at the Fe-sites of BFO lattice. The high purity and structural changes induced by Mg doping are confirmed by X-ray powder diffractometer and Raman spectra. Enhanced magnetic properties are observed in Mg substituted samples, which simultaneously exhibit ferromagnetic and superparamagnetic properties at room temperature. A physical model is proposed to support the observed ferromagnetism of Mg doped samples, and the superparamagnetic properties are revealed by the temperature dependent magnetization measurements. The improved magnetic properties and soft nature obtained by Mg doping in BFO nanoparticles demonstrate the possibility of BFO nanoparticles to practical applications.

  17. Searching for the nanoscopic–macroscopic boundary

    Energy Technology Data Exchange (ETDEWEB)

    Velásquez, E.A. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Investigación en Modelamiento y Simulación Computacional, Universidad de San Buenaventura Sec. Medellín, A.A. 5222, Medellín (Colombia); Altbir, D. [Departamento de Física, Universidad de Santiago de Chile (USACH), CEDENNA, Santiago (Chile); Mazo-Zuluaga, J. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Duque, L.F. [GICM and GES Groups, Instituto de Física-FCEN, Universidad de Antioquia UdeA, Calle 70 No. 52-21 Medellín (Colombia); Grupo de Física Teórica, Aplicada y Didáctica, Facultad de Ciencias Exactas y Aplicadas Instituto Tecnológico Metropolitano, Medellín (Colombia); Mejía-López, J., E-mail: jmejia@puc.cl [Facultad de Física, Pontificia Universidad Católica de Chile, CEDENNA, Santiago (Chile)

    2013-12-15

    Several studies have focused on the size-dependent properties of elements, looking for a unique definition of the nanoscopic–macroscopic boundary. By using a novel approach consisting of an energy variational method combined with a quantum Heisenberg model, here we address the size at which the ordering temperature of a magnetic nanoparticle reaches its bulk value. We consider samples with sizes in the range 1–500 nm, as well as several geometries and crystalline lattices and observe that, contrarily to what is commonly argued, the nanoscopic-microscopic boundary depends on both factors: shape and crystalline structure. This suggests that the surface-to-volume ratio is not the unique parameter that defines the behavior of a nanometric sample whenever its size increases reaching the bulk dimension. Comparisons reveal very good agreement with experimental evidence with differences less than 2%. Our results have broad implications for practical issues in measurements on systems at the nanometric scale. - Highlights: • A novel quantum-Heisenberg variational energy method is implemented. • The asymptotic behavior toward the thermodynamic limit is explored. • An important dependence of the nano-bulk boundary on the geometry is found. • And also an important dependence on the crystalline lattice. • We obtain a very good agreement with experimental evidence with differences <2%.

  18. Synthesis and magnetic properties of Co-Zn magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Vaidyanathan, G. [Department of Physics, Pondicherry Engineering College, Pondicherry 605014 (India)], E-mail: gvn_pec@yahoo.com; Sendhilnathan, S. [Department of Physics, Sri Manakula Vinayagar Engineering College, Pondicherry 605107 (India)], E-mail: sendhil29@yahoo.co.in

    2008-03-15

    Co{sub 1-x}Zn{sub x}Fe{sub 2}O{sub 4} (with x varying from 0 to 0.7) nanoparticles to be used for ferrofluid preparation were prepared by chemical co-precipitation method. The fine particles were suitably dispersed in transformer oil using oleic acid as the surfactant. The magnetization (M{sub s}) and the size of the particles were measured at room temperature. The magnetization (M{sub s}) was found to decrease with the increase in zinc substitution. The magnetic particle size (D{sub m}) of the fluid was found to vary from 11.19 to 4.25 nm decreasing with the increase in zinc substitution.

  19. Magnetoresistive properties of nanostructured magnetic metals, manganites, and magnetic semiconductors

    Science.gov (United States)

    Solin, N. I.; Romashev, L. N.; Naumov, S. V.; Saranin, A. A.; Zotov, A. V.; Olyanich, D. A.; Kotlyar, V. G.; Utas, O. A.

    2016-02-01

    We consider methods for controlling magnetoresistive parameters of magnetic metal superlattices, manganites, and magnetic semiconductors. By reducing the thickness of ferromagnetic layers in superlattices (e.g., Fe layers in Fe/Cr superlattices), it is possible to form superparamagnetic clustered-layered nanostructures with a magnetoresistance weakly depending on the direction of the external magnetic field, which is very important for applications of such type of materials. Producing Mn vacancies and additionally annealing lanthanum manganites in the oxygen atmosphere, it is possible to increase their magnetoresistance by more than four orders of magnitude. By changing the thickness of p- n junction in the structure of ferromagnetic semiconductors, their magnetoresistance can be increased by 2-3 orders of magnitude.

  20. Transport processes in macroscopically disordered media from mean field theory to percolation

    CERN Document Server

    Snarskii, Andrei A; Sevryukov, Vladimir A; Morozovskiy, Alexander; Malinsky, Joseph

    2016-01-01

    This book reflects on recent advances in the understanding of percolation systems to present a wide range of transport phenomena in inhomogeneous disordered systems. Further developments in the theory of macroscopically inhomogeneous media are also addressed. These developments include galvano-electric, thermoelectric, elastic properties, 1/f noise and higher current momenta, Anderson localization, and harmonic generation in composites in the vicinity of the percolation threshold. The book describes how one can find effective characteristics, such as conductivity, dielectric permittivity, magnetic permeability, with knowledge of the distribution of different components constituting an inhomogeneous medium. Considered are a wide range of recent studies dedicated to the elucidation of physical properties of macroscopically disordered systems. Aimed at researchers and advanced students, it contains a straightforward set of useful tools which will allow the reader to derive the basic physical properties of compli...

  1. The magnetic properties of powdered and compacted microcrystalline permalloy

    Science.gov (United States)

    Kollár, P.; Olekšáková, D.; Füzer, J.; Kováč, J.; Roth, S.; Polański, K.

    2007-03-01

    The aim of this work is to investigate the magnetic properties of powdered and compacted microcrystalline Ni-Fe (81 wt% of Ni) permalloy. It was found by investigating the influence of mechanical milling on the magnetic properties of powder samples prepared by milling of the ribbon that the alloy remains a solid solution with stable structure during the whole milling process. With decreasing particle size the rotation of magnetization vector gradually becomes dominant magnetization process and thus coercivity increases. After compaction of the powder by uniaxial hot pressing the magnetic contact between powder particles is recreated and for resulting bulk the displacement of the domain walls becomes dominant magnetization process with coercivity of 11 A/m (comparable with the coercivity of conventional permalloy).

  2. Magnetic properties of a nanoribbon: An effective-field theory

    Science.gov (United States)

    Wang, Jiu-Ming; Jiang, Wei; Zhou, Chen-Long; Shi, Zuo; Wu, Chuang

    2017-02-01

    An effective-field theory is proposed to study magnetic properties of a nanoribbon. The model consists of a core spin-3/2 and shell spin-2 with a ferrimagnetic exchange coupling, which is described by transverse Ising model with the anisotropy. Based on the differential operator technique, the magnetization and the susceptibility formulas of the nanoribbon are given. Numerical results of the magnetization, the susceptibility, the hysteresis loop of the system are discussed for specific values of the parameters. Magnetization plateaus exhibits on the magnetization curves at low temperature. The exchange coupling, the anisotropy and the transverse field have important roles in the magnetic properties for the nanoribbon. Results may provide some guidance to design in the nanoribbons.

  3. Magnetic properties measurement of soft magnetic composite material (SOMALOY 700) by using 3-D tester

    Science.gov (United States)

    Asari, Ashraf; Guo, Youguang; Zhu, Jianguo

    2017-08-01

    Core losses of rotating electrical machine can be predicted by identifying the magnetic properties of the magnetic material. The magnetic properties should be properly measured since there are some variations of vector flux density in the rotating machine. In this paper, the SOMALOY 700 material has been measured under x, y and z- axes flux density penetration by using the 3-D tester. The calibrated sensing coils are used in detecting the flux densities which have been generated by the Labview software. The measured sensing voltages are used in obtaining the magnetic properties of the sample such as magnetic flux density B, magnetic field strength H, hysteresis loop which can be used to calculate the total core loss of the sample. The results of the measurement are analyzed by using the Mathcad software before being compared to another material.

  4. Relationship between nanoparticle growth and magnetic properties of magnetic nanocomposites

    NARCIS (Netherlands)

    Ortega, D.; Garitaonandia, J. S.; Ramirez-del-Solar, M.; Barrera-Solano, C.; Dominguez, M.

    2008-01-01

    A description of the growth processes of maghemite (gamma-Fe(2)O(3)) nanoparticles in a silica matrix (SiO(2)) synthesized under a classic sol-gel method is proposed in order to explain the observed magnetic behavior at different stages of the sample heat treatment. Analytical electron microscopy st

  5. Magnetic properties of Pr-Fe-Co-B bonded HDDR magnets with alloying additions

    Directory of Open Access Journals (Sweden)

    Eguiberto Galego

    2007-09-01

    Full Text Available Microstructures and magnetic properties of Pr-Fe-Co-B bonded magnets were investigated. The magnets can be represented by the formulae, Pr14Fe63.9Co16B6M 0.1 (M = Ti, V, Cr, Ni, Zr, Nb or Mo, Pr14Fe63.8Co16B6Nb 0.1T0.1 (T/= Al, Si, P, Cu or Ga and Pr14Fe63.6Co16B6Nb 0.1R0.3 (R = Gd, Tb or Dy. The effects of additions on the magnetic properties of PrFeCoB-based magnets have been studied. Magnetically hard powders have been produced from homogenised alloys using the hydrogenation, disproportionation, desorption and recombination (HDDR process. The HDDR powders were isostatically pressed and bonded with cyanoacrylate adhesive to form permanent magnets.

  6. Magnetic Properties of Nanometer-sized Crystalline and Amorphous Particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Bødker, Franz; Hansen, Mikkel Fougt;

    1997-01-01

    Amorphous transition metal-metalloid alloy particles can be prepared by chemical preparation techniques. We discuss the preparation of transition metal-boron and iron-carbon particles and their magnetic properties. Nanometer-sized particles of both crystalline and amorphous magnetic materials...... are superparamagnetic at finite temperatures. The temperature dependence of the superparamagnetic relaxation time and the influence of inter-particle interactions is discussed. Finally, some examples of studies of surface magnetization of alpha-Fe particles are presented....

  7. Processing, properties and some novel applications of magnetic nanoparticles

    Indian Academy of Sciences (India)

    D Bahadur; J Giri; Bibhuti B Nayak; T Sriharsha; P Pradhan; N K Prasad; K C Barick; R D Ambashta

    2005-10-01

    Magnetic nanoparticles have been prepared by various soft chemical methods including self-assembly. The bare or surface-modified particles find applications in areas such as hyperthermia treatment of cancer and magnetic field-assisted radioactive chemical separation. We present here some of the salient features of processing of nanostructured magnetic materials of different sizes and shapes, their properties and some possible applications. The materials studied included metals, metal-ceramic composites, and ferrites.

  8. Magnetic Properties of Nanometer-sized Crystalline and Amorphous Particles

    DEFF Research Database (Denmark)

    Mørup, Steen; Bødker, Franz; Hansen, Mikkel Fougt

    1997-01-01

    Amorphous transition metal-metalloid alloy particles can be prepared by chemical preparation techniques. We discuss the preparation of transition metal-boron and iron-carbon particles and their magnetic properties. Nanometer-sized particles of both crystalline and amorphous magnetic materials...... are superparamagnetic at finite temperatures. The temperature dependence of the superparamagnetic relaxation time and the influence of inter-particle interactions is discussed. Finally, some examples of studies of surface magnetization of alpha-Fe particles are presented....

  9. Elastic properties of DNA linked flexible magnetic filaments

    Energy Technology Data Exchange (ETDEWEB)

    Erglis, K; Cebers, A [Department of Theoretical Physics, University of Latvia, Zellu 8, Riga, LV-1002 (Latvia); Zhulenkovs, D; Sharipo, A [Latvian Biomedical Research and Study Center, Ratsupites 1, Riga, LV-1067 (Latvia)], E-mail: aceb@tesla.sal.lv

    2008-05-21

    Elastic properties of magnetic filaments linked by DNA in solutions of univalent and bivalent salts with different pH values are investigated through their deformation in an external field. A strong dependence of the bending modulus in bivalent salt solution on the pH is shown. Experimental results are interpreted on the basis of the magnetic elastica.

  10. Magnetic properties of nanostructured CuFe2O4

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Goya, G.F.; Rechenberg, H.R.

    1999-01-01

    The structural evolution and magnetic properties of nanostructured copper ferrite, CuFe2O4, have been investigated by X-ray diffraction, Mossbauer spectroscopy, and magnetization measurements. Nanometre-sized CuFe2O4 particles with a partially inverted spinel structure were synthesized by high-en...

  11. Microstructure characterization and magnetic properties of nano structured materials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, X.C

    2000-07-01

    The present thesis deals with the unique microstructural properties and their novel magnetic properties of core-shell Ni-Ce nano composite particles, carbon encapsulated Fe, Co, and Ni nanoparticles and the nano crystallization behavior of typical ferromagnetic Fe{sub 78}Si{sub 9}B{sub 13} ribbons. These properties have intensively been investigated by high resolution transmission electron microscopy (HREM), X-ray diffraction (XRD), scanning electron microscopy (Sem), X-ray energy dispersive spectroscopy [eds.]; selected area electron diffraction pattern (SAED), Ft-IR, differential scanning calorimeter (DSC). In addition, magnetic moments measurements at different temperatures and applied fields have been performed by transmission Moessbauer spectroscopy, superconducting quantum interference device magnetometer (SQUID), and vibrating sample magnetometer (VSM). The present studies may provide the insights for the better understanding of the correlation between the unique microstructure and novel magnetic properties for several magnetic nano structured materials. (Author)

  12. Biomonitoring of particulate matter by magnetic properties of Ulmus ...

    African Journals Online (AJOL)

    ... and quality of vegetation in different parts of the city and create sustainable urban ... Four stations in different areas of green space, including, one park, one ... Keywords: Particulate matter, green area, magnetic properties, biomonitoring ...

  13. Nanodisperse Nickel Ferrite: Methods of Production, Structure and Magnetic Properties

    National Research Council Canada - National Science Library

    N Zaporina; J Grabis; M Maiorov; A Krumina; G Heidemane; D Bocharov

    2012-01-01

      Nanodisperse Nickel Ferrite: Methods of Production, Structure and Magnetic Properties The nickel ferrite nanoparticles were prepared using combustion synthesis and plasma chemical synthesis based on evaporation of coarse-grained...

  14. Structural and magnetic properties of granular CoPd multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Vivas, L.G.; Figueroa, A.I.; Bartolomé, F. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Rubín, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Ciencia y Tecnología de Materiales y Fluidos, E-50018 Zaragoza (Spain); García, L.M. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain); Deranlot, C.; Petroff, F. [Unité Mixte de Physique CNRS/Thales, F-91767 Palaiseau Cedex, France and Université Paris-Sud, F-191405 Orsay Cedex (France); Ruiz, L.; González-Calbet, J.M [Dept. de Química Inorgánica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Brookes, N.B.; Wilhelm, F.; Rogalev, A. [European Synchrotron Radiation Facility (ESRF), CS40220, F-38043 Grenoble Cedex 9 (France); Bartolomé, J. [Instituto de Ciencia de Materiales de Aragón (ICMA), CSIC-Universidad de Zaragoza, Dept. de Física de la Materia Condensada, E-50009 Zaragoza (Spain)

    2016-02-15

    Multilayers of bimetallic CoPd alloyed and assembled nanoparticles, prepared by room temperature sequential sputtering deposition on amorphous alumina, were studied by means of high-resolution transmission electron microscopy, x-ray diffraction, SQUID-based magnetometry and x-ray magnetic circular dichroism. Alloying between Co and Pd in these nanoparticles gives rise to a high perpendicular magnetic anisotropy. Their magnetic properties are temperature dependent: at low temperature, the multilayers are ferromagnetic with a high coercive field; at intermediate temperature the behavior is of a soft-ferromagnet, and at higher temperature, the perpendicular magnetic anisotropy in the nanoparticles disappears. The magnetic orbital moment to spin moment ratio is enhanced compared with Co bare nanoparticles and Co fcc bulk. - Highlights: • CoPd granular nanolayers show perpendicular magnetic anisotropy. • Three magnetic phases are detected: hard-ferro, soft-ferro and superparamagnetism. • The nanoparticles have Co-core and CoPd alloy shell morphology.

  15. Colossal anisotropy of the magnetic properties of doped lithium nitrodometalates

    Energy Technology Data Exchange (ETDEWEB)

    Antropov, Vladimir P [Ames Laboratory; Antonov, Victor N [Ames Laboratory

    2014-09-01

    We present a first-principles investigation of the electronic structure and physical properties of doped lithium nitridometalates Li2(Li1-xMx)N (LiMN) with M = Cr, Mn, Fe, Co, and Ni. The diverse properties include the equilibrium magnetic moments, magneto-crystalline anisotropy, magneto-optical Kerr spectra, and x-ray magnetic circular dichroism. We explain the colossal magnetic anisotropy in LiFeN by its unique electronic structure which ultimately leads to a series of unusual physical properties. The most unique property is a complete suppression of relativistic effects and freezing of orbital moments for in-plane orientation of the magnetization. This leads to the colossal spatial anisotropy of many magnetic properties including energy, Kerr, and dichroism effects. LiFeN is identified as an ultimate single-ion anisotropy system where a nearly insulating state can be produced by a spin orbital coupling alone. A very nontrivial strongly fluctuating and sign changing character of the magnetic anisotropy with electronic 3d-atomic doping is predicted theoretically. A large and highly anisotropic Kerr effect due to the interband transitions between atomic-like Fe 3d bands is found for LiFeN. A giant anisotropy of the x-ray magnetic circular dichroism for the Fe K spectrum and a very weak one for the Fe L2,3 spectra in LiFeN are also predicted.

  16. Large batch recycling of waste Nd–Fe–B magnets to manufacture sintered magnets with improved magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.T. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Yue, M., E-mail: yueming@bjut.edu.cn [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Liu, W.Q. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Li, X.L.; Yi, X.F.; Huang, X.L. [Anhui Province Key Laboratories of Rare Earth Permanent Magnet Materials, Anhui, 231500 (China); Anhui Earth-panda Advance Magnetic Material Co., Ltd., Anhui, 231500 (China); Zhang, D.T. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Chen, J.W. [Anhui Province Key Laboratories of Rare Earth Permanent Magnet Materials, Anhui, 231500 (China); Anhui Earth-panda Advance Magnetic Material Co., Ltd., Anhui, 231500 (China)

    2015-11-15

    The waste Nd–Fe–B sintered magnets up to 500 kg per batch were recycled to manufacture anisotropic sintered magnets by combination of hydrogen decrepitation (HD) and alloying technique. Magnetic properties and thermal stability of both the waste magnets and recycled magnets were investigated. The recycled magnet exhibits magnetic properties with remanence (B{sub r}) of 12.38 kGs, coercivity (H{sub ci}) of 24.89 kOe, and maximum energy product [(BH){sub max}] of 36.51 MGOe, respectively, which restores 99.20% of B{sub r}, 105.65% of H{sub ci}, and 98.65% of (BH){sub max} of the waste magnets, respectively. The volume fraction of Nd-rich phase in the recycled magnets is about 10.1 vol.%, which is bigger than that of the waste magnets due to the additive of Nd{sub 3}PrFe{sub 14}B alloy containing more rare earth. The remanence temperature coefficient (α) and coercivity temperature coefficient (β) of the recycled magnets are −0.1155%/K and −0.5099%/K in the range of 288–423 K, respectively, which are comparative to those of the waste magnets. - Highlights: • Large batch recycling of waste Nd–Fe–B sintered magnets were performed. • The recycled magnet restores 99.20% of B{sub r}, 105.65% of H{sub ci} and 98.65% of (BH){sub max} of the magnet. • The recycled magnets bears bigger volume fraction and better distribution of Nd-rich phase. • The recycled magnets exhibit similar temperature coefficients and maximum working temperature.

  17. Magnetic properties of the magnetic hybrid membranes based on various polymer matrices and inorganic fillers

    Energy Technology Data Exchange (ETDEWEB)

    Rybak, Aleksandra, E-mail: Aleksandra.Rybak@polsl.pl [Department of Physical Chemistry and Technology of Polymers, Faculty of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice (Poland); Kaszuwara, Waldemar [Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warszawa (Poland)

    2015-11-05

    Magnetic hybrid membranes based on ethylcellulose (EC), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and various magnetic praseodymium and neodymium powder microparticles as fillers were obtained. Permeability, diffusion and sorption coefficients of O{sub 2}, N{sub 2} and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on constant pressure permeation technique. The microstructure studies and the phase analysis of magnetic membranes were also performed using SEM and XRD. The influence of magnetic parameters, like coercivity, remanence and saturation magnetization of created membranes on the gas transport properties was studied. The results showed that their coercivity depended on composition and microstructure of the magnetic powder. On the other hand, remanence and saturation magnetization increased with the increase of the powder addition in the membrane. It was found that the magnetic membrane's gas transport properties were improved with the increase of membrane's remanence, saturation magnetization and magnetic particle filling. The decrease in powder particle size and associated increase of the membrane's coercivity also positively influenced the gas transport and separation properties of investigated membranes. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes had higher gas permeability, while their permselectivity and solubility coefficient values were rather maintained or slightly increased. The results also showed that the magnetic powder content enhanced significantly gas diffusivity in EC and PPO membranes. It was also analyzed the dependence of the drift coefficient w on the magnetic parameters of investigated membranes. The correlation between the membrane selectivity, permeability and magnetic properties with their XRD characteristics was stated. - Highlights: • Membrane's production consisting of EC or PPO

  18. Magnetic properties of rapidly quenched Fe-Ni alloys

    Science.gov (United States)

    Rossiter, P. L.; Jago, R. A.; Jenkins, B. M.

    1983-01-01

    The magnetic properties of Fe-29 at.% Ni and Fe-50 at.% Ni alloys prepared by chill block melt spinning (CMBS) have been determined and compared with those of the bulk alloys. It has been found that atomic diffusion is enhanced by CMBS and that magnetic properties can change markedly even after annealing at relatively low temperatures. The increases in T c observed are attributed to heterogeneous short range atomic ordering.

  19. Magnetic properties of doped Heisenberg chains

    Energy Technology Data Exchange (ETDEWEB)

    Frahm, Holger; Slavnov, Nikita A

    2000-06-05

    The magnetic susceptibility of systems from a class of integrable models for doped spin-S Heisenberg chains is calculated in the limit of vanishing magnetic field. For small concentrations x{sub h} of the mobile spin-(S-1/2) charge carriers we find an explicit expression for the contribution of the gapless mode associated to the magnetic degrees of freedom of these holes to the susceptibility which exhibits a singularity for x{sub h}{yields}0 for sufficiently large S. We prove a sum rule for the contributions of the two gapless magnetic modes in the system to the susceptibility which holds for arbitrary hole concentration. This sum rule complements the one for the low temperature specific heat which has been obtained previously.

  20. MAGNETIC PROPERTY CHANGE IN AN AUSTENITIC STAINLESS STEEL SUBJECTED TO DAMAGE AT ELEVATED TEMPERATURE - MICROSTRUCTURE RESPONSIBLE FOR MAGNETIC PROPERTY

    Institute of Scientific and Technical Information of China (English)

    Y.Nagae; K.Aoto

    2004-01-01

    It has been found that magnetic property changes in austenitic stainless steel subjected to creep at high temperature. The change of magnetic property is mainly due to decrease the chromium concentration in the vicinity of grain boundary and transform into martensite in the area. However this result is for short-term creep. It is necessary to evaluate the long-term creep in order to develop non-destructive technique for plants. Moreover it is important to evaluate the fatigue. The change of magnetic property for those damages at high temperatures is investigated. The transformation into martensite is observed for both the long-term creep and fatigue. The magnetic regions are observed in sever deformed area and near crack. Then the formation of magnetic phases is related to the damage. The damage at high temperature can be universally evaluated.

  1. Properties of Magnetized Quark-Hybrid Stars

    CERN Document Server

    Orsaria, M; Vucetich, H; Weber, F

    2011-01-01

    The structure of a magnetized quark-hybrid stars (QHS) is modeled using a standard relativistic mean-field equation of state (EoS) for the description of hadronic matter. For quark matter we consider a bag model EoS which is modified perturbatively to account for the presence of a uniform magnetic field. The mass-radius (M-R) relationship, gravitational redshift and rotational Kepler periods of such stars are compared with those of standard neutron stars (NS).

  2. Electrical Properties of Nanostructured Magnetic Colloid and Influence of Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    PU Sheng-Li; CHEN Xian-Feng; DI Zi-Yun; GENG Tao; XIA Yu-Xing

    2007-01-01

    We investigate the electrical properties of the nanostructured magnetic colloid without and with magnetic Held. The competition between the directional motion of the charged magnetic nanoparticles and other minor nonmagnetic impurities (also small amount of ions) under applied voltage and their random orientation due to thermal activation is implemented to elaborate the electrically conduction mechanism under zero magnetic Geld. Two equivalent electric circuits are employed for explaining the charging and discharging processes. The tunnelling conduction mechanism upon application of externally magnetic field may exist in the nanostructured magnetic colloid. The alternation of the two conduction mechanisms accounts for the current spikes when the magnetic field is switched on or off. This work presents the peculiar electrical phenomena of the magnetically colloidal system.

  3. Magnetic properties and magnetic exchange interactions in Gd1-xREx(RE=Pr, Nd) alloys

    Institute of Scientific and Technical Information of China (English)

    肖素芬; 陈云贵

    2016-01-01

    The effect of Pr, Nd addition on the magnetic properties and magnetic exchange interaction of gadolinium alloys was sys-tematically studied. Curie temperatureTC and magnetic moment of Gd1–xREx (RE=Pr, Nd) systems withx<0.05 were investigated. Whenx<0.05, Pr and Nd formed respectively with Gd continuous solid solution which has the crystalline structure HCP. Study on the magnetic behavior indicated that at near room temperature, the simple ferromagnetism prevailed in these two systems of alloy. The Curie temperature and magnetic moment of Gd1–xREx alloy decreased with RE (RE= Pr, Nd) contentx increasing. The de Gennes factor of Gd1–xREx alloy which was associated with the exchange interaction between magnetic spin components also decreased with RE content increasing. The above results showed that the magnetic exchange interaction between magnetic atoms in gadolinium could be effectively changed by the Pr, Nd addition.

  4. The macroscopic pancake bounce

    Science.gov (United States)

    Andersen Bro, Jonas; Sternberg Brogaard Jensen, Kasper; Nygaard Larsen, Alex; Yeomans, Julia M.; Hecksher, Tina

    2017-01-01

    We demonstrate that the so-called pancake bounce of millimetric water droplets on surfaces patterned with hydrophobic posts (Liu et al 2014 Nat. Phys. 10 515) can be reproduced on larger scales. In our experiment, a bed of nails plays the role of the structured surface and a water balloon models the water droplet. The macroscopic version largely reproduces the features of the microscopic experiment, including the Weber number dependence and the reduced contact time for pancake bouncing. The scalability of the experiment confirms the mechanisms of pancake bouncing, and allows us to measure the force exerted on the surface during the bounce. The experiment is simple and inexpensive and is an example where front-line research is accessible to student projects.

  5. Magnetic properties and thermal stability of anisotropic bonded Nd-Fe-B magnets by warm compaction

    Institute of Scientific and Technical Information of China (English)

    TAO Siwu; LU Xin; TIAN Jianjun; QU Xuanhui; Y. Honkura; H. Mitaraib; K. Noguchi

    2009-01-01

    Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the viscosity of the binders, was 110℃. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows: remanence Br = 0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax = 166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120℃ for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.

  6. Magnetic properties of alluvial soils polluted with heavy metals

    Science.gov (United States)

    Dlouha, S.; Petrovsky, E.; Boruvka, L.; Kapicka, A.; Grison, H.

    2012-04-01

    Magnetic properties of soils, reflecting mineralogy, concentration and grain-size distribution of Fe-oxides, proved to be useful tool in assessing the soil properties in terms of various environmental conditions. Measurement of soil magnetic properties presents a convenient method to investigate the natural environmental changes in soils as well as the anthropogenic pollution of soils with several risk elements. The effect of fluvial pollution with Cd, Cu, Pb and Zn on magnetic soil properties was studied on highly contaminated alluvial soils from the mining/smelting district (Příbram; CZ) using a combination of magnetic and geochemical methods. The basic soil characteristics, the content of heavy metals, oxalate, and dithionite extractable iron were determined in selected soil samples. Soil profiles were sampled using HUMAX soil corer and the magnetic susceptibility was measured in situ, further detailed magnetic analyses of selected distinct layers were carried out. Two types of variations of magnetic properties in soil profiles were observed corresponding to indentified soil types (Fluvisols, and Gleyic Fluvisols). Significantly higher values of topsoil magnetic susceptibility compared to underlying soil are accompanied with high concentration of heavy metals. Sequential extraction analysis proved the binding of Pb, Zn and Cd in Fe and Mn oxides. Concentration and size-dependent parameters (anhysteretic and isothermal magnetization) were measured on bulk samples in terms of assessing the origin of magnetic components. The results enabled to distinguish clearly topsoil layers enhanced with heavy metals from subsoil samples. The dominance of particles with pseudo-single domain behavior in topsoil and paramagnetic/antiferromagnetic contribution in subsoil were observed. These measurements were verified with room temperature hysteresis measurement carried out on bulk samples and magnetic extracts. Thermomagnetic analysis of magnetic susceptibility measured on

  7. Electronic and magnetic properties of ultrathin rhodium nanowires

    CERN Document Server

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

    2003-01-01

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

  8. Integrated On-line Instrumentation System of Magnetic Properties Measurement

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A portable microcomputer-controlled inspection system has been developed for detection of mag netic properties of soft magnetic materials. It incorporates custom designed software for control of the magnetic field during operation such as demagnetization, field sweeping, and for data logging and analysis. Results are recorded using a 12-bit analog to digital converter and are then stored on disk. The magnetic hysteresis loop and Barkhausen noise data can be converted into important magnetic parameters:, coecivity, remanence, and hysteresis loss, Barkhausen ampli tude, and Barkhausen noise energy. This system incorporated with the magnetostriction, and magnetoacoustic emission, is then related with the nondestructive detection of material degra dation.

  9. Thermal to electricity conversion using thermal magnetic properties

    Science.gov (United States)

    West, Phillip B [Idaho Falls, ID; Svoboda, John [Idaho Falls, ID

    2010-04-27

    A system for the generation of Electricity from Thermal Energy using the thermal magnetic properties of a Ferromagnetic, Electrically Conductive Material (FECM) in one or more Magnetic Fields. A FECM is exposed to one or more Magnetic Fields. Thermal Energy is applied to a portion of the FECM heating the FECM above its Curie Point. The FECM, now partially paramagnetic, moves under the force of the one or more Magnetic Fields. The movement of the FECM induces an electrical current through the FECM, generating Electricity.

  10. Canonical quantization of macroscopic electromagnetism

    Energy Technology Data Exchange (ETDEWEB)

    Philbin, T G, E-mail: tgp3@st-andrews.ac.u [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom)

    2010-12-15

    Application of the standard canonical quantization rules of quantum field theory to macroscopic electromagnetism has encountered obstacles due to material dispersion and absorption. This has led to a phenomenological approach to macroscopic quantum electrodynamics where no canonical formulation is attempted. In this paper macroscopic electromagnetism is canonically quantized. The results apply to any linear, inhomogeneous, magnetodielectric medium with dielectric functions that obey the Kramers-Kronig relations. The prescriptions of the phenomenological approach are derived from the canonical theory.

  11. Canonical quantization of macroscopic electromagnetism

    CERN Document Server

    Philbin, T G

    2010-01-01

    Application of the standard canonical quantization rules of quantum field theory to macroscopic electromagnetism has encountered obstacles due to material dispersion and absorption. This has led to a phenomenological approach to macroscopic quantum electrodynamics where no canonical formulation is attempted. In this paper macroscopic electromagnetism is canonically quantized. The results apply to any linear, inhomogeneous, magnetoelectric medium with dielectric functions that obey the Kramers-Kronig relations. The prescriptions of the phenomenological approach are derived from the canonical theory.

  12. Characterizing the Properties of Coronal Magnetic Null Points

    Science.gov (United States)

    Barnes, Graham; DeRosa, Marc; Wagner, Eric

    2015-08-01

    The topology of the coronal magnetic field plays a role in a wide range of phenomena, from Coronal Mass Ejections (CMEs) through heating of the corona. One fundamental topological feature is the null point, where the magnetic field vanishes. These points are natural sites of magnetic reconnection, and hence the release of energy stored in the magnetic field. We present preliminary results of a study using data from the Helioseismic and Magnetic Imager aboard NASA's Solar Dynamics Observatory to characterize the properties and evolution of null points in a Potential Field Source Surface model of the coronal field. The main properties considered are the lifetime of the null points, their distribution with height, and how they form and subsequently vanish.This work is supported by NASA/LWS Grant NNX14AD45G, and by NSF/SHINE grant 1357018.

  13. Magnetic properties of ferromagnetic nanowire arrays: Theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Ghaddar, A; Gieraltowski, J [Laboratoire de Magnetisme de Bretagne, UBO, CNRS-FRE 3117, C. S. 93837 Brest Cedex 3 (France); Gloaguen, F, E-mail: abbas.ghaddar@univ-brest.f [Laboratoire de Chimie, Electrochimie Moleculaire et Chimie Analytique, UBO, CNRS-UMR 6521, C. S. 93837 Brest Cedex 3 (France)

    2010-01-01

    Magnetic nanowires are good candidates for microwave filters, sensors and data storage applications. An investigation of magnetic properties of single-component nanowires as a function of diameter and aspect ratio is performed in this work. Nickel nanowire (with 15 and 100 nm diameter and 6000 nm length) are grown with electrodeposition in polycarbonates templates. Two reversal modes (coherent and curling) are studied versus nanowire diameter. Magnetostatic interaction among wires and its effect on nanowire magnetic properties is also studied. Using vibrating magnetometer (VSM) and X-band ferromagnetic resonance (FMR) experiments at room temperature we infer that the interaction field H{sub c} value may vary significantly and may cause a change of magnetic easy axis orientation along geometrical wire axis (for large diameter) to an easy magnetic plane perpendicular to the nanowire axis (for small diameter).

  14. Magnetic properties and thermodynamics in a metallic nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Wei, E-mail: weijiang.sut.edu@gmail.com; Li, Xiao-Xi; Guo, An-Bang; Guan, Hong-Yu; Wang, Zan; Wang, Kai

    2014-04-15

    A metallic nanotube composed of the ferromagnetic spin-3/2 inner shell and spin-1 outer shell with a ferrimagnetic interlayer coupling has been studied by using the effective-field theory with correlations (EFT). With both existence of the magnetic anisotropy and transverse field, we have studied effects of them on the magnetic properties and the thermodynamics. Some interesting phenomena have been found in the phase diagrams. At low temperature, the magnetization curves present different behaviors. Two compensation points have been found for the certain values of the system parameters in the system. The research results of metallic nanotubes may have potential applications in the fields of biomedicine and molecular devices. - Highlights: • A hexagonal metallic nanotube is composed of spin-3/2 inner layer and spin-1 outer layer. • Various types of magnetization curves depend on physical parameters and temperature. • We study the effects of physical parameters on the magnetic properties and thermodynamics.

  15. Magnetic properties and heavy metal contents of automobile emission particulates

    Institute of Scientific and Technical Information of China (English)

    LU Sheng-gao; BAI Shi-qiang; CAI Jing-bo; XU Chuang

    2005-01-01

    Measurements of the magnetic properties and total contents of Cu, Cd, Pb and Fe in 30 automobile emission particulate samples indicated the presence of magnetic particles in them. The values of frequency dependent susceptibility (χfd)showed the absence of superparamagnetic (SP) grains in the samples. The IRM20 mT (isothermal remanent magnetization at 20 mT)being linearly proportional to SIRM (saturation isothermal remanent magnetization) (R2=0.901), suggested that ferrimagnetic minerals were responsible for the magnetic properties of automobile emission particulates. The average contents of Cu, Cd, Pb and Fe in automobile emission particulates were 95.83, 22.14, 30.58 and 34727.31 mg/kg, respectively. Significant positive correlations exist between the magnetic parameters and the contents of Pb, Cu and Fe. The magnetic parameters of automobile emission particulates reflecting concentration of magnetic particles increased linearly with increase of Pb and Cu content, showed that the magnetic measurement could be used as a preliminary index for detection of Pb and Cu pollution.

  16. Magnetic properties of nanocrystalline FeNiN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Prieto, P.; Sanz, J.M. [Departamento de Fisica Aplicada and Instituto de Ciencia de Materiales ' ' Nicolas Cabrera' ' , Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Camarero, J.; Sacristan, N. [Departamento de Fisica de la Materia Condensada and Instituto de Ciencia de Materiales ' ' Nicolas Cabrera' ' , Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Boerma, D.O. [Departamento de Fisica de la Materia Condensada and Centro de Micro Analisis de Materiales, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

    2006-05-15

    FeNiN thin films with a Ni content varying between 5 and 36 at% (as determined by X-ray photoelectron spectroscopy) have been deposited in a Dual Ion Beam Sputtering System at room temperature. The structure and crystalline size were studied by X-ray diffraction while the magnetic properties were investigated by vectorial kerr magnetometry. In general, the deposited films present a nanocrystaline cubic structure and well defined in-plane magnetic anisotropy. The variation of the magnetic properties was attributed to changes in composition and nanocrystalline structure. FeNiN thin films with a Ni content of about 15 at% show the better soft magnetic properties with a minimum in the coercivity of 9 Oe. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Magnetic properties of supported metal atoms and clusters

    Science.gov (United States)

    Martins, Michael; Wurth, Wilfried

    2016-12-01

    Clusters are small systems ranging from a few atoms up to several thousand atoms. They are of high interest in basic research, but also for applications due to their specific electronic, magnetic or chemical properties depending on size and composition. For small clusters, quantum size effects play an important role and specific material properties might be tailored by choosing a special size or composition of the cluster. Here, we review the magnetic properties of adatoms and supported small mass-selected transition-metal clusters in the few-atom limit investigated by x-ray magnetic circular dichroism spectroscopy in the soft x-ray regime. The influence of cluster size, composition, the cluster-surface and intra-cluster interaction on the spin and orbital magnetic moments will be discussed.

  18. Magnetic properties on strained manganite thin film

    Science.gov (United States)

    Prajapat, C. L.; Singh, M. R.; Gupta, S. K.; Bhattacharya, D.; Basu, S.; Ravikumar, G.

    2014-04-01

    Structural and magnetic studies on La2/3Sr1/3MnO3 (LSMO) epitaxial films grown on STO (100) and MgO (100) substrates by Pulsed Laser Deposition are presented. Due to larger interface strain, the grain size of LSMO on MgO is much smaller than that on STO substrate. However, anisotropy energy produced as a result of in plane tensile strain is much larger in case of the films deposited on MgO in such a way that the blocking (irreversibility) temperature and the coercive fields inferred from temperature and magnetic field dependent magnetization measurements are significantly higher. The importance of this result for the memory applications is highlighted.

  19. Electronic properties of SPFC electrodes materials. Macroscopic phenomena and effects induced by nanometric size of catalyst; Proprieta' elettroniche di materiali per elettrodi di SPFC: fenomeni macroscopici ed effetti legati alle dimensioni nanometriche del catalizzatore

    Energy Technology Data Exchange (ETDEWEB)

    Giorgi, R.; Turtu' , S. [ENEA, Centro Ricerche Casaccia, S. Maria di Galeria, RM (Italy). Dipt. Innovazione; Ascarelli, P. [Consiglio Nazionale delle Ricerche, Montelibretti, RM (Italy). Ist. di Metodologie Inorganiche Avanzate

    1999-07-01

    In this work the electronic properties and the composition of the three layers (diffusive, catalytic and outermost) are studied separately. In the first part, an anomalous behaviour of the photoemission peaks from the diffusive layer has been evidenced and correlated with the macroscopic electronic conductivity. In the second part, the electronic properties of the PT clusters are compared with the macroscopic electron conductivity. In the second part, the electronic properties of the PT clusters are compared with those of PT bulk, as a function of thermal treatment and after half-cell measurements. A correlation of the binding energy, asymmetry and width of the peaks with the different status of the metal has been attempted. [Italian] Il lavoro consiste di due parti: l'una dedicata allo studio delle caratteristiche dello strato di supporto e diffusivo, l'altra allo studio dello strato catalizzatore. Nella prima parte, la presenza anomala negli spettri XPS viene messa in relazione con la conducibilita' elettronica delle nanoparticelle metalliche in funzione delle condizioni di preparazione degli elettrodi e delle simulazioni di funzionamento. Sono messe in evidenza le problematiche connesse all'interpretazione degli spettri di fotoemissione da sistemi costituiti da particelle nanometriche, intermedi tra la condizione di atomo isolato e quella del solido, in cui gli effetti di dimensione svolgono un ruolo importante nel determinare risposte diverse ed inaspettate rispetto al comportamento del metallo massivo.

  20. Superconductivity and magnetism: Materials properties and developments

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, N.H.; Bay, N.; Grivel, J.C. (eds.) [and others

    2003-07-01

    The 24th Risoe International Symposium on Materials Science focuses on development of new materials, devices and applications, as well as experimental and theoretical studies of novel and unexplained phenomena in superconductivity and magnetism, e.g. within high.T{sub c} superconductivity, magnetic superconductors, MgB{sub 2}, CMR materials, nanomagnetism and spin-tronics. The aim is to stimulate exchange of ideas and establish new collaborations between leading Danish and international scientists. The topics are addressed by presentations from 24 invited speakers and by 41 contributed papers. (ln)

  1. Thermal properties of a large-bore cryocooled 10 T superconducting magnet for a hybrid magnet

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, M., E-mail: Mas_Ishizuka@shi.co.j [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Hamajima, T. [Graduate School of Engineering, Tohoku University, 6-6 Aramaki Aza Aoba, Aoba-ku, Sendai 980-8579 (Japan); Itou, T. [Ehime Works, Sumitomo Heavy Industries, Ltd., 5-2 Soubiraki-cho, Niihama, Ehime 792-8588 (Japan); Sakuraba, J. [Research and Development Center, Sumitomo Heavy Industries, Ltd., 19 Natsushima-chou, Yokosuka, Kanagawa 237-8555 (Japan); Nishijima, G.; Awaji, S.; Watanabe, K. [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2010-11-01

    A cryocooled 10 T superconducting magnet with a 360 mm room temperature bore has been developed for a hybrid magnet. The superconducting magnet cooled by four Gifford-McMahon cryocoolers has been designed to generate a magnetic field of 10 T. Since superconducting wires composed of coils were subjected to large hoop stress over 150 MPa and Nb{sub 3}Sn superconducting wires particularly showed a low mechanical strength due to those brittle property, Nb{sub 3}Sn wires strengthened by NbTi-filaments were developed for the cryocooled superconducting magnet. We have already reported that the hybrid magnet could generate the resultant magnetic field of 27.5 T by adding 8.5 T from the superconducting magnet and 19 T from a water-cooled Bitter resistive magnet, after the water-cooled resistive magnet was inserted into the 360 mm room temperature bore of the cryocooled superconducting magnet. When the hybrid magnet generated the field of 27.5 T, it achieved the high magnetic-force field (B x {partial_derivative}Bz/{partial_derivative}z) of 4500 T{sup 2}/m, which was useful for magneto-science in high fields such as materials levitation research. In this paper, we particularly focus on the cause that the cryocooled superconducting magnet was limited to generate the designed magnetic field of 10 T in the hybrid magnet operation. As a result, it was found that there existed mainly two causes as the limitation of the magnetic field generation. One was a decrease of thermal conductive passes due to exfoliation from the coil bobbin of the cooling flange. The other was large AC loss due to both a thick Nb{sub 3}Sn layer and its large diameter formed on Nb-barrier component in Nb{sub 3}Sn wires.

  2. Remanence Properties and Magnetization Reversal Mechanism of Fe Nanowire Arrays

    Institute of Scientific and Technical Information of China (English)

    WANG Jian-Bo; LIU Qing-Fang; XUE De-Sheng; LI Fa-Shen

    2004-01-01

    @@ Remanence properties and magnetization reversal mechanism of Fe nanowire arrays with diameters 16 nm and130nm are studied. Isothermal remanent magnetization curves show that the contribution of irreversible magnetization decreases when the diameter changes from 16nm to 130nm. The remanence coercivities of these nanowires obtained in dc-demagnetization curve are about 2400 Oe and 800 Oe, respectively. The magnetization reversal mechanism is different in these two samples. For the nanowire array with diameter 16nm, both the nucleation and the pinning have effects on magnetization reversal mechanism, and the pinning field (about 2500Oe) is larger than the nucleation field (about 2200 Oe). However, for the nanowire array with diameter 130nm,the magnetization reversal mechanism is dominated by the pinning effect of domain walls.

  3. Magnetic nanofluid properties as the heat transfer enhancement agent

    Directory of Open Access Journals (Sweden)

    Roszko Aleksandra

    2016-01-01

    Full Text Available The main purpose of this paper was to investigate an influence of various parameters on the heat transfer processes with strong magnetic field utilization. Two positions of experimental enclosure in magnetic environment, two methods of preparation and three different concentrations of nanoparticles (0.0112, 0.056 and 0.112 vol.% were taken into account together with the magnetic field strength. Analysed nanofluids consisted of distilled water (diamagnetic and Cu/CuO particles (paramagnetic of 40–60 nm size. The nanofluids components had different magnetic properties what caused complex interaction of forces’ system. The heat transfer data and fluid flow structure demonstrated the influence of magnetic field on the convective phenomena. The most visible consequence of magnetic field application was the heat transfer enhancement and flow reorganization under applied conditions.

  4. The structural and magnetic properties of holmium/scandium superlattices

    DEFF Research Database (Denmark)

    Bryn-Jacobsen, C.; Cowley, R.A.; McMorrow, D.F.;

    1997-01-01

    The properties of Ho/Sc superlattices grown by molecular beam epitaxy (MBE) have been investigated using X-ray and neutron diffraction techniques. Structural studies reveal the novel existence of more than one a lattice parameter. Examining the magnetic properties, it is found that the Ho 4f...

  5. Magnetic properties of thin Ni films measured by a dc SQUID-based magnetic microscope

    DEFF Research Database (Denmark)

    Snigirev, O.V.; Andreev, K.E.; Tishin, A.M.;

    1997-01-01

    We have applied a scanning HTS (high-temperature superconductor) de SQUID (superconducting quantum interference device) -based magnetic microscope to study the magnetic properties of Au/Ni/Si(100) films in the thickness range from 8 to 200 Angstrom at T = 77 K. A one-domain structure with in-plan...

  6. Magnetic property and microstructure of SmCo magnetic recording films

    Institute of Scientific and Technical Information of China (English)

    LI; Ning; LI; Shuai

    2009-01-01

    Cr/SmCo/Cr thin films with Sm concentration of 37.7 at.% were deposited on glass substrates by magnetron sputtering. Meas-urement of magnetic properties showed that the SmCo film possessed good magnetic anisotropy, a high coercivity of 3019 kA/m and low magnetic exchange coupling. Microstructure analysis showed that crystallized SmCo5 magnetic phase, non-magnetic SmCo2 phase and Sm2Co7 phase co-existed ill the film. The non-magnetic SmCo2 phase might function as isolator of SmCo grains, leading to a decrease of magnetic exchange coupling. Moreover, a Cr2)3 oxide layer which could protect the SmCo layer from oxidation formed at the surface of the Cr cap layer.

  7. Magnetic and Cohesive Properties from Cononical Bands

    DEFF Research Database (Denmark)

    Poulsen, U. K.; Kollar, J.; Andersen, O. K.

    1976-01-01

    The atomic volumes, the bulk moduli, the magnetizations, the gain susceptibilities and the derivatives of these quantities with respect to pressure have been obtained from first principles for Fe, Ni, Rh, Pd, Ir and Pt at 0K using canonical band theory and the local spin-density approximation...

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

    Science.gov (United States)

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

    2016-12-01

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

  9. Magnetic properties of a classical XY spin dimer in a "planar" magnetic field

    Science.gov (United States)

    Ciftja, Orion; Prenga, Dode

    2016-10-01

    Single-molecule magnetism originates from the strong intra-molecular magnetic coupling of a small number of interacting spins. Such spins generally interact very weakly with the neighboring spins in the other molecules of the compound, therefore, inter-molecular spin couplings are negligible. In certain cases the number of magnetically coupled spins is as small as a dimer, a system that can be considered the smallest nanomagnet capable of storing non-trivial magnetic information on the molecular level. Additional interesting patterns arise if the spin motion is confined to a two-dimensional space. In such a scenario, clusters consisting of spins with large-spin values are particularly attractive since their magnetic interactions can be described well in terms of classical Heisenberg XY spins. In this work we calculate exactly the magnetic properties of a nanomagnetic dimer of classical XY spins in a "planar" external magnetic field. The problem is solved by employing a mathematical approach whose idea is the introduction of auxiliary spin variables into the starting expression of the partition function. Results for the total internal energy, total magnetic moment, spin-spin correlation function and zero-field magnetic susceptibility can serve as a basis to understand the magnetic properties of large-spin dimer building blocks.

  10. Magnetic properties of Surabaya river sediments, East Java, Indonesia

    Science.gov (United States)

    Mariyanto, Bijaksana, Satria

    2017-07-01

    Surabaya river is one of urban rivers in East Java Province, Indonesia that is a part of Brantas river that flows in four urban and industrial cities of Mojokerto, Gresik, Sidoarjo, and Surabaya. The urban populations and industries along the river pose serious threat to the river mainly for their anthropogenic pollutants. This study aims to characterize the magnetic properties of sediments in various locations along Surabaya river and correlate these magnetic properties to the level of pollution along the river. Samples are taken and measured through a series of magnetic measurements. The mass-specific magnetic susceptibility of sediments ranges from 259.4 to 1134.8 × 10-8 m3kg-1. The magnetic minerals are predominantly PSD to MD magnetite with the grain size range from 6 to 14 μm. The mass-specific magnetic susceptibility tends to decreases downstream as accumulation of magnetic minerals in sediments is affected not only by the amount of household and industrial wastes but also by sediment dredging, construction of embankments, and extensive erosion arround the river. Sediments located in the industrial zone on the upstream area tend to have higher mass-specific magnetic susceptibility than in the non-industrial zones on the downstream area.

  11. Magnetic properties of dipolar chains in ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Avgin, I., E-mail: ihavgin@gmail.com [Department of Electrical Engineering, Ege University, Izmir (Turkey); Huber, D.L. [Physics Department, University of Wisconsin-Madison, Madison, WI (United States)

    2014-07-01

    We have investigated the dipole interaction energies per particle and the local dipole field distributions in a frozen magnetization model of a ferrofluid chain in a saturating magnetic field. A lognormal distribution of particle diameters was assumed. The interaction energies were calculated for one dimensional arrays of dipoles with moments parallel to the chain. We have computed the energies by various approximations related to the hard sphere particle diameter distribution. A similar approach was followed for the local field distributions. It was found that the energy per particle and mean local field were largely determined by the mean particle diameter, but the distribution of local fields was sensitive to both the mean diameter and the assumptions about spatial correlations between particles of different size. Detailed results are presented for water-soluble Fe{sub 3}O{sub 4}/PAA (polyacrylic acid). (author)

  12. Magnetic properties of rare earth superlattices

    CERN Document Server

    Wilkins, C J T

    2001-01-01

    Single-crystal Tm/Y and Tm/Lu superlattices have been grown using molecular beam epitaxy and their chemical structures have been determined using X-ray diffraction. Magnetisation measurements have revealed a more complicated phase diagram than that of pure Tm. Application of a field along the c-direction gave rise to an extra transition, and transitions were detected for the superlattices when the field was applied along the b-axis. In neutron diffraction studies, c-axis longitudinally modulated magnetic structures were found for both Tm/Y and Tm/Lu, which propagate coherently through the non-magnetic layers. In the case of Tm/Lu superlattices, there is evidence for ordering of the basal plane components.

  13. Magnetic properties of nano-composite particles

    Science.gov (United States)

    Xu, Xia

    Chemical synthesis routes for hollow spherical BaFe12O 19, hollow mesoporous spherical BaFe12O19, worm-shape BaFe12O19 and FeCo particles were developed. These structured particles have great potentials for the applications including magnetic recording medium, catalyst support, and energy storage. Magnetically exchange coupled hard/soft SrFe12O19/FeCo and MnBi/FeCo composites were synthesized through a newly proposed process of magnetic self-assembly. These exchange coupled composites can be potentially used as rare-earth free permanent magnets. Hollow spherical BaFe12O19 particles (shell thickness ˜5 nm) were synthesized from eth-ylene glycol assisted spray pyrolysis. Hollow mesoporous spherical BaFe12O19 particles (shell thickness ˜100 nm) were synthesized from ethanol assisted spray pyrolysis, followed by alkaline ethylene glycol etching at 185 °C. An alpha-Fe2O3 and BaCO3 nanoparticle mixture was synthesized with reverse microemulsion, followed by annealing at 900 °C for 2 hours to get worm-shape BaFe 12O19 particles, which consisted of 3-7 stacked hexagonal plates. FeCo nanoparticles were synthesized by reducing FeCl2 and CoCl2 in diphenyl ether with n-butyllithium at 200 °C in an inert gas environment. The surfactant of oleic acid was used in the synthesis to make particles well dispersed in nonpolar solvents (such as hexane). SrFe12O19/FeCo core/shell particles were prepared through a magnetic self-assembly process. The as-synthesized soft FeCo nanoparticles were magnetically attracted by hard SrFe12O19 parti-cles, forming a SrFe12O19/FeCo core/shell structure. The magnetic self-assembly mechanism was confirmed by applying alternating-current demagnetization to the core/shell particles, which re-sulted in a separation of SrFe 12O19 and FeCo particles. MnBi/FeCo composites were synthesized, and the exchange coupling between MnBi and FeCo phases was demonstrated by smooth magnetic hysteresis loop of MnBi/FeCo composites. The thermal stability of Mn

  14. The correlations between processing parameters and magnetic properties of an iron-resin soft magnetic composite

    Energy Technology Data Exchange (ETDEWEB)

    Hemmati, I. [Materials Science and Engineering Department, Sharif University of Technology, P.O. Box 11365-9466, Tehran (Iran, Islamic Republic of); Madaah Hosseini, H.R. [Materials Science and Engineering Department, Sharif University of Technology, P.O. Box 11365-9466, Tehran (Iran, Islamic Republic of)]. E-mail: madaah@sharif.edu; Kianvash, A. [Department of Ceramic Engineering, Faculty of Engineering, University of Tabriz, Tabriz 51664 (Iran, Islamic Republic of)

    2006-10-15

    In this study, internal microstrain of an iron-resin composite produced by powder metallurgy has been calculated using the Williamson-Hall method. The effects of microstrain evolution during different processing conditions on magnetic properties such as coercive force and hysteresis loss have been investigated. The results show that there are regular and similar changes of coercivity and hysteresis loss. Both of these properties are directly dependant on the pinning effect of the internal microstrain against the movement of magnetic domain walls during magnetization process.

  15. Magnetically textured ferrofluid in a non-magnetic matrix: Magnetic properties

    Indian Academy of Sciences (India)

    Mrudul Gadhvi; R V Upadhyay; Kinnari Parekh; R V Mehta

    2004-04-01

    Texturing of two different magnetic fluids were carried out in paraffin wax under the influence of an external magnetic field. The textured samples were characterized using magnetization measurement and a.c. susceptibility techniques. The results are discussed in the light of ratio of anisotropic energy to magnetic and thermal energies.

  16. Magnetic Properties and Thermal Entanglement on a Triangulated Kagome Lattice

    CERN Document Server

    Ananikian, N S; Chakhmakhchyan, L A; Kocharian, A N

    2011-01-01

    The magnetic and entanglement thermal (equilibrium) properties in spin-1/2 Ising-Heisenberg model on a triangulated Kagome lattice are analyzed by means of variational mean-field like treatment based on Gibbs-Bogoliubov inequality. Because of the separable character of Ising-type exchange interactions between the Heisenberg trimers the calculation of quantum entanglement in a self-consistent field can be performed for each of the trimers individually. The concurrence in terms of three qubit isotropic Heisenberg model in effective Ising field is non-zero even in the absence of a magnetic field. The magnetic and entanglement properties exhibit common (plateau and peak) features observable via (antferromagnetic) coupling constant and external magnetic field. The critical temperature for the phase transition and threshold temperature for concurrence coincide in the case of antiferromagnetic coupling between qubits. The existence of entangled and disentangled phases in saturated and frustrated phases is establishe...

  17. Synthesis and magnetic properties of a novel ferrite organogel

    Science.gov (United States)

    Li, Sichu; John, Vijay T.; Irvin, Glen C.; Rachakonda, Suguna H.; McPherson, Gary L.; O'Connor, Charles J.

    1999-04-01

    A novel magnetic organogel that can be considered a precursor example of a magnetoresponsive gel is reported. The gel is formed by the bridging of ferrite containing anionic bis(2-ethlhexyl) sodium sulfosuccinate reverse micelles with 2,6-dihydroxynaphthalene (2,6-DHN). The addition of 2,6-DHN leads to a room temperature quotes "freezing in" of the liquid solution to a clear organogel. Ferrite particles in the size range 10-15 nm are doped into the gel network and are thus suspended in the optically clear gel media. The magnetic properties of the gel were measured using a superconducting quantum interference device magnetometer. The results reveal that the gel exhibits superparamagnetic behavior with a blocking temperature of 6 K (at an applied field of 1000 G), and a coercivity of 850 G at 2 K. The ferrites introduced into the gel serve the function of magnetic "seeds" via which magnetic properties are acquired by the gel.

  18. Computer Simulation of Effect of Intergrain Exchange Interaction on Magnetic Properties of Nanocomposite Magnets

    Institute of Scientific and Technical Information of China (English)

    Fukunaga H; Mukaino H

    2004-01-01

    Effects of the intergrain exchange interaction on magnetic properties of nanocomposite magnets were investigated by using the computer simulation based on the micromagnetic theory. The simulation was carried out under the assumptions that the strength of the intergrain exchange interaction is weaker than that of the intragrain exchange interaction, that inhomogeneous nanostructures result in the distribution of the strength of the intergrain exchange interaction, and that there exists nonmagnetic intergranular phase(NMIP) between grain boundaries. The distribution of the strength of the intergrain exchange interaction was simulated by the lognormal distribution with the standard deviation of σ.The calculations for Nd2Fe14B/α-Fe nanocomposite magnets reveal that a suitably weak intergrain exchange interaction and small grain size enable us to improve magnetic properties. It is also found that a Nd2Fe14B/α-Fe nanocomposite magnet has a potential of a(BH)max value exceeding 300 kJ·m-3. On the other hand, the calculations for Nd2Fe14B/Fe3B nanocomposite magnets reveal that the distribution of the strength of the intergrain exchange interaction deteriorates magnetic properties significantly. Particularly, this tendency is remarkable, when the grain size L is larger than its optimum value, 11 nm. The existence of nonmagnetic boundary layers accelerats this tendency. At σ=0.2, the calculated demagnetization curve for the model magnet composed of Nd2Fe14B(36%)/Fe3B(54%)/NMIP(10%)(Valume fraction) grains(L=15 nm) agrees with that obtained experimentally for a Nd2Fe14B/Fe3B nanocomposite magnet. These results suggest importance of refinement of grain size, suppression of a nonmagnetic intergranular phase, and preparation of homogeneous nanostructure for superior magnetic properties.

  19. Magnetic properties of small Fe clusters: a nonorthogonal Hamiltonian study

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    We calculate the magnetic properties of small FeN clusters(N=2~7,9,13,15) by using a parameterized Hubbard tight-binding sp d-band model Hamiltonian, with the parameters obtained from nonorthogonal Ham il tonian parameters. the average magnetic moments, and the spin-polarized charge distribution within clusters are in agreement with those obtained by first-prin ciple and tight-binding calculations. The effect of the nonorthogonal basis is discussed.

  20. PHASE TRANSITION PROPERTIES OF A TWO COMPONENT FINITE MAGNETIC SUPERLATTICE

    Institute of Scientific and Technical Information of China (English)

    WANG XIAO-GUANG; LIU NING-NING; PAN SHAO-HUA; YANG GUO-ZHEN

    2000-01-01

    We study an (l, n) finite superlattice, which consists of two alternative magnetic materials(components) of l and n atomic layers, respectively. Based on the Ising model, we examine the phase transition properties of the magnetic superlattice. By transfer matrix method we derive the equation for Curie temperature of the superlattice. Numerical results are obtained for the dependence of Curie temperature on the thickness and exchange constants of the superlattice.

  1. GEMAS: Unmixing magnetic properties of European agricultural soil

    Science.gov (United States)

    Fabian, Karl; Reimann, Clemens; Kuzina, Dilyara; Kosareva, Lina; Fattakhova, Leysan; Nurgaliev, Danis

    2016-04-01

    High resolution magnetic measurements provide new methods for world-wide characterization and monitoring of agricultural soil which is essential for quantifying geologic and human impact on the critical zone environment and consequences of climatic change, for planning economic and ecological land use, and for forensic applications. Hysteresis measurements of all Ap samples from the GEMAS survey yield a comprehensive overview of mineral magnetic properties in European agricultural soil on a continental scale. Low (460 Hz), and high frequency (4600 Hz) magnetic susceptibility k were measured using a Bartington MS2B sensor. Hysteresis properties were determined by a J-coercivity spectrometer, built at the paleomagnetic laboratory of Kazan University, providing for each sample a modified hysteresis loop, backfield curve, acquisition curve of isothermal remanent magnetization, and a viscous IRM decay spectrum. Each measurement set is obtained in a single run from zero field up to 1.5 T and back to -1.5 T. The resulting data are used to create the first continental-scale maps of magnetic soil parameters. Because the GEMAS geochemical atlas contains a comprehensive set of geochemical data for the same soil samples, the new data can be used to map magnetic parameters in relation to chemical and geological parameters. The data set also provides a unique opportunity to analyze the magnetic mineral fraction of the soil samples by unmixing their IRM acquisition curves. The endmember coefficients are interpreted by linear inversion for other magnetic, physical and chemical properties which results in an unprecedented and detailed view of the mineral magnetic composition of European agricultural soils.

  2. Do micromagnetic simulations correctly predict hard magnetic hysteresis properties?

    Energy Technology Data Exchange (ETDEWEB)

    Toson, P., E-mail: peter.toson@tuwien.ac.at; Zickler, G.A.; Fidler, J.

    2016-04-01

    Micromagnetic calculations using the finite element technique describe semi-quantitatively the coercivity of novel rare earth permanent magnets in dependence on grain size, grain shape, grain alignment and composition of grain boundaries and grain boundary junctions and allow the quantitative prediction of magnetic hysteretic properties of rare earth free magnets based on densely packed elongated Fe and Co nanoparticles, which depend on crystal anisotropy, aspect ratio and packing density. The nucleation of reversed domains preferentially takes place at grain boundary junctions in granular sintered and melt-spun magnets independently on the grain size. The microstructure and the nanocompostion of the intergranular regions are inhomogeneous and too complex in order to make an exact model for micromagnetic simulations and to allow a quantitative prediction. The incoherent magnetization reversal processes near the end surfaces reduce and determine the coercive field values of Co- and Fe-based nanoparticles.

  3. Effects of temperature and Nickel content on magnetic properties of Ni-doped ZnO

    Institute of Scientific and Technical Information of China (English)

    REN Lingling; JEUNG Won Young

    2006-01-01

    Magnetic properties of diluted magnetic semiconductors (DMSs), Ni-doped ZnO materials, prepared by sol-gel method were investigated by measuring magnetization as functions of magnetic field.The Ni content affects the magnetic properties at low sintered temperature but it has few effects on the magnetic properties at high sintered temperature.The sintered temperature has great effects on the magnetic properties of Ni/ZnO at high original mole ratio of Ni/Zn while it has slight effects on the magnetic properties of Ni/ZnO at low original mole ratio of Ni/Zn whatever low or high sintered temperature.

  4. Quantum Magnetism

    CERN Document Server

    Barbara, Bernard; Sawatzky, G; Stamp, P. C. E

    2008-01-01

    This book is based on some of the lectures during the Pacific Institute of Theoretical Physics (PITP) summer school on "Quantum Magnetism", held during June 2006 in Les Houches, in the French Alps. The school was funded jointly by NATO, the CNRS, and PITP, and entirely organized by PITP. Magnetism is a somewhat peculiar research field. It clearly has a quantum-mechanical basis – the microsopic exchange interactions arise entirely from the exclusion principle, in conjunction with respulsive interactions between electrons. And yet until recently the vast majority of magnetism researchers and users of magnetic phenomena around the world paid no attention to these quantum-mechanical roots. Thus, eg., the huge ($400 billion per annum) industry which manufactures hard discs, and other components in the information technology sector, depends entirely on room-temperature properties of magnets - yet at the macroscopic or mesoscopic scales of interest to this industry, room-temperature magnets behave entirely classic...

  5. Particle size dependent rheological property in magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jie; Pei, Lei; Xuan, Shouhu, E-mail: xuansh@ustc.edu.cn; Yan, Qifan; Gong, Xinglong, E-mail: gongxl@ustc.edu.cn

    2016-06-15

    The influence of the particle size on the rheological property of magnetic fluid was studied both by the experimental and computer simulation methods. Firstly, the magnetic fluids were prepared by dispersing Fe{sub 3}O{sub 4} nanospheres with size varied from 40 nm to 100 nm and 200 nm in the solution. Then, the rheological properties were investigated and it was found that the relative magnetorheological effects increased with increasing the particle size. Finally, the molecular dynamic simulation was used to analyze the mechanical characteristics of the magnetic fluid and the chain-like model agreed well with the experimental result. The authentic chain-like structure observed by a microscope agreed with the simulation results. The three particles composed of the similar cluster nanostructure, thus they exhibited similar magnetic property. To this end, the unique assembling microstructures was the origination of the mechanical difference. And it was found that the higher MR (magnetorheological) effects of the large particle based magnetic fluid was originated from the stronger assembling microstructure under the applying magnetic field. - Highlights: • 40 nm, 100 nm and 200 nm Fe{sub 3}O{sub 4} nanospheres were dispersed in water. • The magnetorheological effect increased with increasing the particle sizes. • Molecular dynamic simulation was used in this article.

  6. Single crystal Processing and magnetic properties of gadolinium nickel

    Energy Technology Data Exchange (ETDEWEB)

    Shreve, Andrew John [Iowa State Univ., Ames, IA (United States)

    2012-01-01

    GdNi is a rare earth intermetallic material that exhibits very interesting magnetic properties. Spontaneous magnetostriction occurs in GdNi at T{sub C}, on the order of 8000ppm strain along the c-axis and only until very recently the mechanism causing this giant magnetostriction was not understood. In order to learn more about the electronic and magnetic structure of GdNi, single crystals are required for anisotropic magnetic property measurements. Single crystal processing is quite challenging for GdNi though since the rare-earth transition-metal composition yields a very reactive intermetallic compound. Many crystal growth methods are pursued in this study including crucible free methods, precipitation growths, and specially developed Bridgman crucibles. A plasma-sprayed Gd2O3 W-backed Bridgman crucible was found to be the best means of GdNi single crystal processing. With a source of high-quality single crystals, many magnetization measurements were collected to reveal the magnetic structure of GdNi. Heat capacity and the magnetocaloric effect are also measured on a single crystal sample. The result is a thorough report on high quality single crystal processing and the magnetic properties of GdNi.

  7. Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

    Directory of Open Access Journals (Sweden)

    Bashar Issa

    2013-10-01

    Full Text Available Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm, viruses, genes, down to proteins (3–50 nm. The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.

  8. Microstructure and magnetic properties of colloidal cobalt nano-clusters

    Energy Technology Data Exchange (ETDEWEB)

    Torchio, R. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); European Synchrotron Radiation Facility, 6 Rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France); Meneghini, C., E-mail: meneghini@fis.uniroma3.i [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); Mobilio, S. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); CNR-TASC c/o GILDA-ESRF Grenoble (France); Laboratori Nazionali di Frascati INFN, via E. Fermi 40, I-00044 Frascati, Roma (Italy); Capellini, G. [Dipartimento di Fisica ' E. Amaldi' , Universita di Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Garcia Prieto, A. [Departamento de Fisica Aplicada I, Universidad del Pais Vasco (Spain); Alonso, J.; Fdez-Gubieda, M.L. [Departamento de Electricidad y Electronica, Universidad del Pais Vasco (Spain); Turco Liveri, V. [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Longo, A. [ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via U. La Malfa 153, 90146 Palermo (Italy); Ruggirello, A.M. [Dipartimento di Chimica Fisica ' F. Accascina' , Universita di Palermo, Viale delle Scienze, Parco d' Orleans II, Edificio 17, 90128 Palermo (Italy); Neisius, T. [Federation des Sciences Chimiques de Marseille, Universite Paul Cezanne, Faculte des Sciences et Techniques Campus de Saint Jerome av. Escadrille Normandie Niemen 13397 Marseille Cedex (France)

    2010-11-15

    The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a core-shell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The core-shell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant.

  9. Magnetic properties of superparamagnetic nanoparticles loaded into silicon nanotubes

    Science.gov (United States)

    Granitzer, Petra; Rumpf, Klemens; Gonzalez, Roberto; Coffer, Jeffery; Reissner, Michael

    2014-08-01

    In this work, the magnetic properties of silicon nanotubes (SiNTs) filled with Fe3O4 nanoparticles (NPs) are investigated. SiNTs with different wall thicknesses of 10 and 70 nm and an inner diameter of approximately 50 nm are prepared and filled with superparamagnetic iron oxide nanoparticles of 4 and 10 nm in diameter. The infiltration process of the NPs into the tubes and dependence on the wall-thickness is described. Furthermore, data from magnetization measurements of the nanocomposite systems are analyzed in terms of iron oxide nanoparticle size dependence. Such biocompatible nanocomposites have potential merit in the field of magnetically guided drug delivery vehicles.

  10. Magnetoactive elastomeric composites: Cure, tensile, electrical and magnetic properties

    Indian Academy of Sciences (India)

    K Sasikumar; G Suresh; K A Thomas; Reji John; V Natarajan; T Mukundan; R M R Vishnubhatla

    2006-11-01

    Magnetically active elastomer materials were prepared by incorporating nickel powder in synthetic elastomeric matrices, polychloroprene and nitrile rubber. Cure characteristics, mechanical, electrical and magnetic properties were experimentally determined for different volume fractions of magnetoactive filler. The cure time decreases sharply for initial filler loading and the decrease is marginal for additional loading of filler. The tensile strength and modulus at 100% strain was found to increase with increase in the volume fraction of nickel due to reinforcement action. The magnetic impedance and a.c. conductivity are found to increase with increase in volume fraction of nickel as well as frequency.

  11. Magnetic and optoelectronic properties of gold nanocluster-thiophene assembly.

    Science.gov (United States)

    Qin, Wei; Lohrman, Jessica; Ren, Shenqiang

    2014-07-07

    Nanohybrids consisting of Au nanocluster and polythiophene nanowire assemblies exhibit unique thermal-responsive optical behaviors and charge-transfer controlled magnetic and optoelectronic properties. The ultrasmall Au nanocluster enhanced photoabsorption and conductivity effectively improves the photocurrent of nanohybrid based photovoltaics, leading to an increase of power conversion efficiency by 14 % under AM 1.5 illumination. In addition, nanohybrids exhibit electric field controlled spin resonance and magnetic field sensing behaviors, which open up the potential of charge-transfer complex system where the magnetism and optoelectronics interact.

  12. Magnetic properties of a single transverse Ising ferrimagnetic nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Bouhou, S.; El Hamri, M. [Laboratoire de Physique des Matériaux et Modélisation des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Essaoudi, I. [Laboratoire de Physique des Matériaux et Modélisation des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Ainane, A., E-mail: ainane@pks.mpg.de [Laboratoire de Physique des Matériaux et Modélisation des Systèmes, (LP2MS), Unité Associée au CNRST-URAC 08, University of Moulay Ismail, Physics Department, Faculty of Sciences, B.P. 11201 Meknes (Morocco); Max-Planck-Institut für Physik Complexer Systeme, Nöthnitzer Str. 38 D-01187 Dresden (Germany); Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden); Ahuja, R. [Condensed Matter Theory Group, Department of Physics and Astronomy, Uppsala University, 75120 Uppsala (Sweden)

    2015-01-01

    Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanoparticle consisting of a ferromagnetic core, a ferromagnetic surface shell and a ferrimagnetic interface coupling are examined. The effect of the transverse field in the surface shell, the exchange interactions between core/shell and in surface shell on the free energy, thermal magnetization, specific heat and susceptibility are studied. A number of interesting phenomena have been found such as the existence of the compensation phenomenon and the magnetization profiles exhibit P-type, N-type and Q-type behaviors.

  13. Electronic and Magnetic Properties of Small Iridium Clusters

    Institute of Scientific and Technical Information of China (English)

    KUANG Xiang-jun

    2004-01-01

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

  14. Magnetic properties of the binary Nickel/Bismuth alloy

    Science.gov (United States)

    Keskin, Mustafa; Şarlı, Numan

    2017-09-01

    Magnetic properties of the binary Nickel/Bismuth alloy (Ni/Bi) are investigated within the effective field theory. The Ni/Bi alloy has been modeled that the rhombohedral Bi lattice is surrounded by the hexagonal Ni lattice. According to lattice locations, Bi atoms have two different magnetic properties. Bi1 atoms are in the center of the hexagonal Ni atoms (Ni/Bi1 single layer) and Bi2 atoms are between two Ni/Bi1 bilayers. The Ni, Bi1, Bi2 and Ni/Bi undergo a second-order phase transition from the ferromagnetic phase to paramagnetic phase at Tc = 1.14. The magnetizations of the Ni/Bi alloy are observed as Bi1 > Bi2 > Ni/Bi > Ni at T < Tc; hence the magnetization of the Bi1 is dominant and Ni is at least dominant. However, the total magnetization of the Ni/Bi alloy is close to magnetization of the Ni at T < Tc. The corcivities of the Ni, Bi1, Bi2 and Ni/Bi alloy are the same with each others, but the remanence magnetizations are different. Our theoretical results of M(T) and M(H) of the Ni/Bi alloy are in quantitatively good agreement with the some experimental results of binary Nickel/Bismuth systems.

  15. Composite Materials with Magnetically Aligned Carbon Nanoparticles Having Enhanced Electrical Properties and Methods of Preparation

    Science.gov (United States)

    Hong, Haiping (Inventor); Peterson, G.P. (Bud) (Inventor); Salem, David R. (Inventor)

    2016-01-01

    Magnetically aligned carbon nanoparticle composites have enhanced electrical properties. The composites comprise carbon nanoparticles, a host material, magnetically sensitive nanoparticles and a surfactant. In addition to enhanced electrical properties, the composites can have enhanced mechanical and thermal properties.

  16. Review on magnetic and related properties of RTX compounds

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Sachin, E-mail: gsachin55@gmail.com; Suresh, K.G., E-mail: suresh@phy.iitb.ac.in

    2015-01-05

    RTX (R = rare earths, T = 3d/4d/5d, transition metals such as Sc, Ti, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, and X = p-block elements such as Al, Ga, In, Si, Ge, Sn, As, Sb, Bi) series is a huge family of intermetallics compounds. These compounds crystallize in different crystal structures depending on the constituents. Though these compounds have been known for a long time, they came to limelight recently in view of the large magnetocaloric effect (MCE) and magnetoresistance (MR) shown by many of them. Most of these compounds crystallize in hexagonal, orthorhombic and tetragonal crystal structures. Some of them show crystal structure modification with annealing temperature; while a few of them show iso-structural transition in the paramagnetic regime. Their magnetic ordering temperatures vary from very low temperatures to temperatures well above room temperature (∼510 K). Depending on the crystal structure, they show a variety of magnetic and electrical properties. These compounds have been characterized by means of a variety of techniques/measurements such as X-ray diffraction, neutron diffraction, magnetic properties, heat capacity, magnetocaloric properties, electrical resistivity, magnetoresistance, thermoelectric power, thermal expansion, Hall effect, optical properties, XPS, Mössbauer spectroscopy, ESR, μSR, NMR, and NQR. Some amount of work on theoretical calculations on electronic structure, crystal field interaction and exchange interactions has also been reported. The interesting aspect of this series is that they show a variety of physical properties such as Kondo effect, heavy fermion behavior, spin glass state, intermediate valence, superconductivity, multiple magnetic transitions, metamagnetism, large MCE, large positive as well as negative MR, spin orbital compensation, magnetic polaronic behavior, and pseudo gap effect. Except Mn, no other transition metal in these compounds possesses considerable magnetic moments. Because of this

  17. Improved Electrical Insulation of Rare Earth Permanent Magnetic Materials With High Magnetic Properties

    Institute of Scientific and Technical Information of China (English)

    CHANG Ying; WANG Da-peng; LI Wei; PAN Wei; YU Xiao-jun; QI Min

    2009-01-01

    Rare earth permanent magnetic materials are typical electrical conductor, and their magnetic properties will decrease because of the eddy current effect, so it is difficult to keep them stable for a long enough time under a high frequency AC field. In the present study, as far as rare earth permanent magnets are concerned, for the first time, rare earth permanent magnets with strong electrical insulation and high magnetic performance have been obtained through experiments, and their properties are as follows:(1) Sm2TM17: Br=0.62 T, jHc=803.7 kA/m, (BH)m= The magnetic properties of Sm2TM17 and NdFeB are obviously higher than those of ferrite permanent magnet, and the electric insulating characteristics of Sm2TM17 and NdFeB applied have in fact been approximately the same as those of ferrite. Therefore, Sm2TM17 and NdFeB will possess the ability to take the place of ferrite under a certain high frequency AC electric field.

  18. Magnetic Properties of Uranium Based Ferromagnetic Superconductors

    NARCIS (Netherlands)

    Sakarya, S.

    2007-01-01

    Ferromagnetism and superconductivity have long been thought to be mutually exclusive. Recently however it was found that the compounds UGe2, URhGe and UIr belong to a class of materials in which ferromagnetisme and superconductivity appear simultaneously. One characteristic property of these compoun

  19. Impact of Ion Irradiation upon Structure and Magnetic Properties of NANOPERM-Type Amorphous and Nanocrystalline Alloys

    Directory of Open Access Journals (Sweden)

    Marcel Miglierini

    2015-01-01

    Full Text Available Structural modifications and their impact upon magnetic properties are studied in amorphous and nanocrystalline NANOPERM-type 57Fe75Mo8Cu1B16 alloy. They are introduced by irradiation with 130 keV N+ ions to the total fluencies of up to 2.5 × 1017 ions/cm2 under different cooling conditions. Increased temperature during the irradiation triggers formation of nanocrystallites of bcc-Fe in those subsurface regions that are affected by bombarding ions. No crystallization occurs when good thermal contact between the irradiated sample and a sample holder is assured. Instead, structural rearrangement which favours development of magnetically active regions was determined by the local probe methods of Mössbauer spectrometry. Dipole magnetic interactions dominate in subsurface regions on that side of the ribbons which was exposed to ion irradiation. Nevertheless, structural modifications demonstrate themselves also via macroscopic magnetic parameters such as temperature dependence of magnetization, Curie temperature, and hysteresis loops. Impact of only the temperature itself to the observed effects is assessed by the help of samples that were subjected just to heat treatment, that is, without ion irradiation.

  20. Physical properties of elongated magnetic particles: magnetization and friction coefficient anisotropies.

    Science.gov (United States)

    Vereda, Fernando; de Vicente, Juan; Hidalgo-Alvarez, Roque

    2009-06-02

    Anisotropy counts: A brief review of the main physical properties of elongated magnetic particles (EMPs) is presented. The most important characteristic of an EMP is the additional contribution of shape anisotropy to the total anisotropy energy of the particle, when compared to spherical magnetic particles. The electron micrograph shows Ni-ferrite microrods fabricated by the authors.We present an overview of the main physical properties of elongated magnetic particles (EMPs), including some of their more relevant properties in suspension. When compared to a spherical magnetic particle, the most important characteristic of an EMP is an additional contribution of shape anisotropy to the total anisotropy energy of the particle. Increasing aspect ratios also lead to an increase in both the critical single-domain size of a magnetic particle and its resistance to thermally activated spontaneous reversal of the magnetization. For single-domain EMPs, magnetization reversal occurs primarily by one of two modes, coherent rotation or curling, the latter being facilitated by larger aspect ratios. When EMPs are used to prepare colloidal suspensions, other physical properties come into play, such as their anisotropic friction coefficient and the consequent enhanced torque they experience in a shear flow, their tendency to align in the direction of an external field, to form less dense sediments and to entangle into more intricate aggregates. From a more practical point of view, EMPs are discussed in connection with two interesting types of magnetic colloids: magnetorheological fluids and suspensions for magnetic hyperthermia. Advances reported in the literature regarding the use of EMPs in these two systems are included. In the final section, we present a summary of the most relevant methods documented in the literature for the fabrication of EMPs, together with a list of the most common ferromagnetic materials that have been synthesized in the form of EMPs.

  1. Structural, electronic and magnetic properties of MnB2

    Indian Academy of Sciences (India)

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

    2015-08-01

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

  2. Quantum equilibria for macroscopic systems

    Energy Technology Data Exchange (ETDEWEB)

    Grib, A [Department of Theoretical Physics and Astronomy, Russian State Pedagogical University, St. Petersburg (Russian Federation); Khrennikov, A [Centre for Mathematical Modelling in Physics and Cognitive Sciences Vaexjoe University (Sweden); Parfionov, G [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation); Starkov, K [Department of Mathematics, St. Petersburg State University of Economics and Finances (Russian Federation)

    2006-06-30

    Nash equilibria are found for some quantum games with particles with spin-1/2 for which two spin projections on different directions in space are measured. Examples of macroscopic games with the same equilibria are given. Mixed strategies for participants of these games are calculated using probability amplitudes according to the rules of quantum mechanics in spite of the macroscopic nature of the game and absence of Planck's constant. A possible role of quantum logical lattices for the existence of macroscopic quantum equilibria is discussed. Some examples for spin-1 cases are also considered.

  3. Magnetic properties and magnetic phase diagrams of intermetallic compound GdMn2Ge2

    Institute of Scientific and Technical Information of China (English)

    Guo Guang-Hua(郭光华); Zhang Hai-Bei(张海贝); R.Z.Levitin

    2003-01-01

    A modified Yafet-Kittle model is applied to investigate the magnetic properties and magnetic phase transition of the intermetallic compound GdMn2Ge2.Theoretical analysis and calculation show that there are five possible magnetic structures in GdMn2Ge2.Variations of external magnetic field and temperature give rise to the first-order or secondorder magnetic transitions from one phase to another.Based on this model,the magnetic curves of GdMn2Ge2 single crystals at different temperatures are calculated and a good agreement with experimental data has obtained.Based on the calculation,the H-T magnetic phase diagrams of GdMn2Ge2 are depicted.The Gd-Gd,Gd-Mn,intralayer Mn-Mn and interlayer Mn-Mn exchange coupling parameters are estimated.It is shown that,in order to describe the magnetic properties of GdMn2Ge2,the lattice constant and temperature dependence of interlayer Mn-Mn exchange interaction must be taken into account.

  4. Measurement of magnetic properties at cryogenic temperatures

    CERN Multimedia

    1977-01-01

    This picture shows part of the low-mu permeameter to measure permeability of stainless steels and other low-mu materials used in superconducting magnets. The sample, a 5 mm diam., 45 mm long rod, is suspended to long leads before being inserted in the test cryostat. For the measurement the sample is surrounded by a flux- measuring coil and placed in the field of a superconducting solenoid. At a given field the sample is removed.During the removal, the voltage induced in the flux-measuring coil is time integrated giving the flux variation. This equipment was developed to select stainless steels and other low-mu materials used in the ISR Prototype Superconducting Qaudrupole. The person is W.Ansorge.

  5. Bistability properties of magnetic micro-nanowires

    Science.gov (United States)

    Baranov, S. A.; Yaltychenko, O. V.; Kanarovskii, E. Yu.

    2016-12-01

    A mathematical model that describes the process of the reversal magnetization of an amorphous microwire with the help of a large Barkhausen jump is proposed. The model has been estimated with regard to the optimization of the signal-tonoise ratio. Using nonlinear model, we studied the physical factors that cause the fluctuations of the start field. Based on the results of numerical experiments, the new data on the behavior of the start field under different conditions of a switching in a bistable ferromagnetic, including the conditions of high-frequency swapping, have been obtained and compared to the existing data. The results obtained do not contradict the existing physical concepts concerning a domain wall motion and are more general and realistic in a comparison with the previous model.

  6. Magnetic Properties of Different-Aged Chernozemic Soils

    Science.gov (United States)

    Fattakhova, Leysan; Shinkarev, Alexandr; Kosareva, Lina; Nourgaliev, Danis; Shinkarev, Aleksey; Kondrashina, Yuliya

    2016-04-01

    We investigated the magnetic properties and degree of mineral weathering in profiles of different-aged chernozemic soils derived from a uniform parent material. In this work, layer samples of virgin leached chernozem and chernozemic soils formed on the mound of archaeological earthy monument were used. The characterization of the magnetic properties was carried out on the data of the magnetometry and differential thermomagnetic analysis. The evaluation of the weathering degree was carried out on a loss on ignition, cation exchange capacity and X-ray phase analysis on the data of the original soil samples and samples of the heavy fraction of minerals. It was found that the magnetic susceptibility enhancement in humus profiles of newly formed chernozemic soils lagged significantly behind the organic matter content enhancement. This phenomenon is associated with differences in kinetic parameters of humus formation and structural and compositional transformation of the parent material. It is not enough time of 800-900 years to form a relatively "mature" magnetic profile. These findings are well consistent with the chemical kinetic model (Boyle et al., 2010) linking the formation of the soils magnetic susceptibility with the weathering of primary Fe silicate minerals. Different-aged chernozemic soils are at the first stage of formation of a magnetic profile when it is occur an active production of secondary ferrimagnetic minerals from Fe2+ released by primary minerals.

  7. Anisotropic mechanical properties of magnetically aligned fibrin gels measured by magnetic resonance elastography.

    Science.gov (United States)

    Namani, Ravi; Wood, Matthew D; Sakiyama-Elbert, Shelly E; Bayly, Philip V

    2009-09-18

    The anisotropic mechanical properties of magnetically aligned fibrin gels were measured by magnetic resonance elastography (MRE) and by a standard mechanical test: unconfined compression. Soft anisotropic biomaterials are notoriously difficult to characterize, especially in vivo. MRE is well-suited for efficient, non-invasive, and non-destructive assessment of shear modulus. Direction-dependent differences in shear modulus were found to be statistically significant for gels polymerized at magnetic fields of 11.7 and 4.7 T compared to control gels. Mechanical anisotropy was greater in the gels polymerized at the higher magnetic field. These observations were consistent with results from unconfined compression tests. Analysis of confocal microscopy images of gels showed measurable alignment of fibrils in gels polymerized at 11.7 T. This study provides direct, quantitative measurements of the anisotropy in mechanical properties that accompanies fibril alignment in fibrin gels.

  8. Magnetic Properties of Nd8Fe83Co3B6 Nanocomposite Magnets

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The influence of quenching technology, annealing temperature and time on the structures and magnetic properties of Nd8Fe83Co3B6 nanocomposite magnets was investigated. The results show that the α-Fe/Nd2Fe14B nanocomposite magnet containing a small amount of B is difficult to form amorphous state. The magnetic properties of 26 m/s quenched Nd8Fe83Co3B6 powders annealed at 640℃×480 s reach iHc=513 kA/m, Br=1.05 T and (BH)max=92.0 kJ/m3. The grain size is Dα-Fe=21.5 nm and DNd2Fe14B=30.2 nm.

  9. Detailed magnetic study on the formato-bridged MOFs with anion-tunable magnetic properties

    Institute of Scientific and Technical Information of China (English)

    WANG XinYi; WANG ZheMing; GAO Song

    2012-01-01

    Detailed studies of the structures,magnetic properties and photodimerization of a series of formato-bridged MOFs with the general formula M2(HCOO)3(4,4'-bpe)3(H20)3(X)(4,4'-bpe =4,4'-bipyridylethylene,M =Mn(l-X-),X- =CIO-4,NO-3,BF-4,I-,Br-; M =Co(2-X-),X- =CIO-4,NO-3; M =Zn(3-X-),X- =NO-3)were reported.Careful magnetic measurements on an oriented single crystal of 1-ClO-4 determined the spin-flop magnetic phase diagram and some intrinsic parameters,such as the intralayer coupling J,the anisotropy field HA and the exchange field HE.Different anions can remarkably tune the magnetic properties of l-X-,especially the critical fields of the spin-flop transition.Compound 2-ClO-4 remained paramagnetic down to 2 K.

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

    Science.gov (United States)

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

    2017-07-01

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

  11. Silica coated nanoparticles: Synthesis, magnetic properties and spin structure

    Energy Technology Data Exchange (ETDEWEB)

    Mazaleyrat, F., E-mail: mazaleyrat@satie.ens-cachan.f [SATIE, ENS de Cachan, CNRS, UniverSud, 61 av President Wilson, F-94230 Cachan (France); Ammar, M.; LoBue, M. [SATIE, ENS de Cachan, CNRS, UniverSud, 61 av President Wilson, F-94230 Cachan (France); Bonnet, J.-P.; Audebert, P. [PPSM, ENS de Cachan, CNRS, UniverSud, 61 av President Wilson, F-94230 Cachan (France); Wang, G.-Y.; Champion, Y. [ICMPE, CNRS, Universite Paris XII, 2-8 rue Henri Dunant, F-94320 Thiais (France); Hytch, M.; Snoeck, E. [CEMES, CNRS, 29 rue Jeanne Marvig, F-31055 Toulouse (France)

    2009-08-26

    In the recent years, magnetic nanoparticles have been extensively studied for their superparamagnetic properties providing useful labels in biology or for fundamental aspects including the size dependence of magnetic atomic moment and the effect of surface anisotropy. In most cases, the particles were smaller than 10 nm and interestingly, the sizes ranging between 10 and 100 nm have been poorly investigated until now. This is mainly due to the fact that usual chemical routes produce 5-10 nm oxide or metallic particles or eventually 20 nm at most. On the over side, atomization techniques yield particles in the micrometer range. Metallic particles are particularly interesting for better magnetic properties compared to oxides, but they have two big drawbacks: they are not biocompatible and they are conducting electricity. Consequently, it's necessary to produce core-shell particles, for which the shell is biocompatible and insulating and with a perfect control of thickness and uniformity of that shell. In this work, we are studying metallic particles synthesized by an original evaporation-condensation technique that produces particles of several tens of nanometers. We prepared hard magnetic cobalt particles and soft FeNi ones coated with a silica shell using a modified sol-gel method. Morphological and magnetic properties are presented, showing the efficiency of ultrasonic sol-gel process for that purpose.

  12. Anisotropic thermal property of magnetically oriented carbon nanotube polymer composites

    Science.gov (United States)

    Li, Bin; Dong, Shuai; Wang, Caiping; Wang, Xiaojie; Fang, Jun

    2016-04-01

    This paper proposes a method for preparing multi-walled carbon nanotubea/polydimethylsiloxane (MWCNTs/PDMS) composites with enhanced thermal properties by using a high magnetic field (up to 10T). The MWCNT are oriented magnetically inside a silicone by in-situ polymerization method. The anisotropic structure would be expected to produce directional thermal conductivity. This study will provide a new approach to the development of anisotropic thermal-conductive polymer composites. Systematic studies with the preparation of silicone/graphene composites corresponding to their thermal and mechanical properties are carried out under various conditions: intensity of magnetic field, time, temperature, fillings. The effect of MWCNT/graphene content and preparation procedures on thermal conductivity of composites is investigated. Dynamic mechanical analysis (DMA) is used to reveal the mechanical properties of the composites in terms of the filling contents and magnetic field strength. The scanning electron microscope (SEM) is used to observe the micro-structure of the MWCNT composites. The alignment of MWCNTs in PDMS matrix is also studied by Raman spectroscopy. The thermal conductivity measurements show that the magnetically aligned CNT-composites feature high anisotropy in thermal conductivity.

  13. Maxwell's macroscopic equations, the energy-momentum postulates, and the Lorentz law of force

    CERN Document Server

    Mansuripur, Masud

    2013-01-01

    We argue that the classical theory of electromagnetism is based on Maxwell's macroscopic equations, an energy postulate, a momentum postulate, and a generalized form of the Lorentz law of force. These seven postulates constitute the foundation of a complete and consistent theory, thus eliminating the need for actual (i.e., physical) models of polarization P and magnetization M, these being the distinguishing features of Maxwell's macroscopic equations. In the proposed formulation, P(r,t) and M(r,t) are arbitrary functions of space and time, their physical properties being embedded in the seven postulates of the theory. The postulates are self-consistent, comply with the requirements of the special theory of relativity, and satisfy the laws of conservation of energy, linear momentum, and angular momentum. One advantage of the proposed formulation is that it side-steps the long-standing Abraham-Minkowski controversy surrounding the electromagnetic momentum inside a material medium by simply "assigning" the Abra...

  14. Magnetic properties of a long, thin-walled ferromagnetic nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Chen, E-mail: chen.sun@physics.tamu.edu [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Pokrovsky, Valery L. [Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843-4242 (United States); Landau Institute for Theoretical Physics, Chernogolovka, Moscow District, 142432 (Russian Federation)

    2014-04-15

    We consider magnetic properties of a long, thin-walled ferromagnetic nanotube. We assume that the tube consists of isotropic homogeneous magnet whose spins interact via the exchange energy, the dipole–dipole interaction energy, and also interact with an external field via Zeeman energy. Possible stable states are the parallel state with the magnetization along the axis of the tube, and the vortex state with the magnetization along azimuthal direction. For a given material, which of them has lower energy depends on the value γ=R{sup 2}d/(Lλ{sub x}{sup 2}), where R is the radius of the tube, d is its thickness, L is its length and λ{sub x} is an intrinsic scale of length characterizing the ratio of exchange and dipolar interaction. At γ<1, the parallel state wins, otherwise the vortex state is stable. A domain wall in the middle of the tube is always energy unfavorable, but it can exist as a metastable structure. Near the ends of a tube magnetized parallel to the axis a half-domain structure transforming gradually the parallel magnetization to a vortex just at the edge of the tube is energy favorable. We also consider the equilibrium magnetization textures in an external magnetic field either parallel or perpendicular to the tube. Finally, magnetic field produced by a nanotube and an array of tubes is analyzed. - Highlights: • We obtain a simple criterion for stable state of a long, thin-walled magnetic tube. • A domain wall in the middle is always energy unfavorable, but can be metastable. • In external field different states show different hystereses. • Field produced by a tube and an array of tubes is calculated.

  15. Magnetic properties of tephras from Lake Van (Eastern Turkey)

    Science.gov (United States)

    Makaroglu, Ozlem; Caǧatay, Namık; Pesonen, Lauri J.; Orbay, Naci

    2013-04-01

    Here we present magnetic properties of tephra layers in the cores taken from Lake Van, Eastern Anatolia, Turkey. Lake Van is the fourth largest terminal Lake in the world by volume (607 km3). It is 460 m deep and has a salinity of 21.4 per mil and a pH of 9.81. It is located on the East Anatolian Plateau with present day water level of 1648 m.a.s.l., and surrounded by large stratovolcanoes Nemrut, Suphan, Tendurek, and Ararat to the west and north. It has accumulated varved-sediments with tephra units, which all provide important paleoenvironmental records. After a seismic survey, four different locations were selected for coring in Lake Van, with water depths varying between 60 m and 90 m. Four cores having between 3 and 4.8 m length were analyzed for for element geochemistry using XRF Core Scanner analysis. The sub-samples were taken into plastic boxes with a volume of 6.4 cm3 for mineral magnetic analysis. The mineral magnetic measurements included magnetic susceptibility (χ), anhysteretic remanent magnetisation (ARM), isothermal remanent magnetisation (IRM), hysteresis properties and thermomagnetic analyses. According to the mineral magnetic measurements and geochemical analysis, we identified the five tephra layers (T1-T5). These tephra units were correlated with the previously varve-dated units of Landmann et al. (2011). The varve ages of the tephra layers were used to obtain the age-depth model for the cores. According to the age models the cores extend back to 9500 ka BP (varve years). Down-core profiles of all the magnetic properties are highly correlatable between different cores, suggesting that the magnetic records are of regional character. ARM values are found to be more convenient than χ values for correlating the tephra layers. The hysteresis parameters of samples taken from these layers indicate that they are within Pseudo Single Domain range. IRM curves show that low coersivity magnetic minerals are dominated in all tephra layers. Measurements

  16. Magnetic properties and magnetization reversal of α-Fe nanowires deposited in alumina film

    Science.gov (United States)

    Peng, Yong; Zhang, Hao-Li; Pan, Shan-Lin; Li, Hu-Lin

    2000-05-01

    Uniform arrays of Fe nanowires were prepared by electrochemical deposition of iron into nanoporous anodic aluminum oxide films. The microstructure and crystal structures of the nanowires were studied by transmission electron microscopy and electron diffraction. It was found that each nanowire looked like a chain of dots and each dot in the chain was supposed to be a single crystal of α-Fe. Each dot was shown to be a single magnetic domain. The magnetic properties of a uniform array of Fe nanowires and the magnetization reversal in a Fe nanowire were investigated by Mössbauer spectroscopy and vibrating sample magnetometry, which demonstrated that the film of Fe nanowires in alumina had superior perpendicular magnetic characteristics. The magnetic studies also revealed that the moments of each single domain dot were oriented along the chain. Experimental results could be interpreted by the reversal model of "chains of spheres" with the symmetric fanning mechanism.

  17. Neutron investigations of magnetic properties of crystal substances with use of a pulsed magnetic field

    CERN Document Server

    Nitts, V V

    2001-01-01

    Bases for neutron researches of magnetic properties of crystal substances with use of a pulsed magnetic field and analysis of possible application of various neutron sources in this area are submitted. The review of the most interesting physical results is presented. Main investigations on pulsed reactors of JINR are researches on kinetics of the first order reorientational phase transitions induced in single crystals, and also measurements of antiferromagnetic ordering induced by an external magnetic field. Magnetic phase transitions, induced by a field up to 160 kOe in several magnetic ordering substances, were studied in KEK (Japan). Experiment on observation of spin-flop transition in MnF sub 2 was carried out on TRIGA-reactor in a mode of single flashes of power

  18. Intrinsic Magnetism and Collective Magnetic Properties of Size-Selected Nanoparticles

    Science.gov (United States)

    Antoniak, C.; Friedenberger, N.; Trunova, A.; Meckenstock, R.; Kronast, F.; Fauth, K.; Farle, M.; Wende, H.

    Using size-selected spherical FePt nanoparticles and cubic Fe/Fe-oxide nanoparticles as examples, we discuss the recent progress in the determination of static and dynamic properties of nanomagnets. Synchroton radiation-based characterisation techniques in combination with detailed structural, chemical and morphological investigations by transmission and scanning electron microscopy allow the quantitative correlation between element-specific magnetic response and spin structure on the one hand and shape, crystal and electronic structure of the particles on the other hand. Examples of measurements of element-specific hysteresis loops of single 18 nm sized nanocubes are discussed. Magnetic anisotropy of superparamagnetic ensembles and their dynamic magnetic response are investigated by ferromagnetic resonance as a function of temperature at different microwave frequencies. Such investigations allow the determination of the magnetic relaxation and the extraction of the average magnetic anisotropy energy density of the individual particles.

  19. Transport and magnetic properties of CMR manganites with antidot arrays

    Science.gov (United States)

    Zhang, Kai; Du, Kai; Niu, Jiebin; Wei, Wengang; Chen, Jinjie; Yin, Lifeng; Shen, Jian

    2014-03-01

    We fabricated and characterized a series of manganites thin film samples with different densities of antidots. With increasing antidot density, the samples show higher MIT temperature and lower resistivity under zero and low magnetic fields. These differences become smaller and finally vanished when the magnetic field is large enough to melt the charge ordered phase in the system, which is expected in our theoretical explanations. We believe that emerging edge states at the ring of antidotes play a significant role for observed metal-insulator transition and electrical transport properties, which are of great importance of real storage and sensor device design. Magnetic property measurements and theoretical simulation also support the conclusion. These results open up new ways to control and tune the strongly correlated oxides without introduce any new material or field.

  20. Surface modification of Fe304 nanoparticles and their magnetic properties

    Institute of Scientific and Technical Information of China (English)

    Hao Yan; Jian-cheng Zhang; Chen-xia You; Zhen-wei Song; Ben-wei Yu; Yue Shen

    2009-01-01

    Fe3O4 magnetic nanoparticles were synthesized by the hydrothermal method, and the influences of the surfactant sodium bis(2-ethylhexyl) sulfosuecinate (AOT) on the particles were investigated. The structure, morphology, and magnetic properties of the products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). It is confirmed that the as-prepared nanopartieles have been modified by using the surfactant during the synthesis process. The amount of the surfactant has an effect on the size, the dispersal, and the magnetic properties of the particles. Besides, the mechanisms of the influences were also discussed.

  1. Influence of Barium Hexaferrite on Magnetic Properties of Hydroxyapatite Ceramics.

    Science.gov (United States)

    Jarupoom, P; Jaita, P

    2015-11-01

    Hydroxyapatite (HA) powders was derived from natural bovine bone by sequence of thermal processes. The barium hexaferrite (BF) find magnetic powders were added into HA powders in ratio of 1-3 vol.%. The HA-BF ceramics were prepared by a solid state reaction method and sintered at 1250 degrees C for 2 h. Effects of BF additive on structural, physical and magnetic properties of HA ceramics were investigated. X-ray diffraction revealed that all HA-BF samples showed a main phase of high purity hydroxyapatite [Ca10(PO4)6(OH)2] with calcium and phosphate molar ratio of 1.67. The addition of BF into HA inhibited grain growth and caused an improvement of mechanical properties. The M-H hysteresis loops also showed an improvement in magnetic behavior for higher content of BF. Moreover, in vitro bioactivity test indicated that the 2-3 vol.% sample may be suitable for biological applications.

  2. Transport properties of graphene under periodic and quasiperiodic magnetic superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Wei-Tao, E-mail: luweitao@lyu.edu.cn [School of Science, Linyi University, 276005 Linyi (China); Institute of Condensed Matter Physics, Linyi University, 276005 Linyi (China); Wang, Shun-Jin [Department of Physics, Sichuan University, 610064 Chengdu (China); Wang, Yong-Long; Jiang, Hua [School of Science, Linyi University, 276005 Linyi (China); Institute of Condensed Matter Physics, Linyi University, 276005 Linyi (China); Li, Wen [School of Science, Linyi University, 276005 Linyi (China)

    2013-08-15

    We study the transmission of Dirac electrons through the one-dimensional periodic, Fibonacci, and Thue–Morse magnetic superlattices (MS), which can be realized by two different magnetic blocks arranged in certain sequences in graphene. The numerical results show that the transmission as a function of incident energy presents regular resonance splitting effect in periodic MS due to the split energy spectrum. For the quasiperiodic MS with more layers, they exhibit rich transmission patterns. In particular, the transmission in Fibonacci MS presents scaling property and fragmented behavior with self-similarity, while the transmission in Thue–Morse MS presents more perfect resonant peaks which are related to the completely transparent states. Furthermore, these interesting properties are robust against the profile of MS, but dependent on the magnetic structure parameters and the transverse wave vector.

  3. Preparation and electrical properties of oil-based magnetic fluids

    Science.gov (United States)

    Sartoratto, P. P. C.; Neto, A. V. S.; Lima, E. C. D.; Rodrigues de Sá, A. L. C.; Morais, P. C.

    2005-05-01

    This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%-0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7-2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

  4. Gd doped Au nanoclusters: Molecular magnets with novel properties

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-01-01

    The structural, magnetic, and optical properties of subnanometer Au N and AuN-1Gd1 gas phase clusters (N = 2 to 8) are systematically investigated in the framework of (time-dependent) density functional theory, using the B3LYP hybrid exchange correlation functional. The size dependent evolution of the gap between the highest occupied and lowest unoccupied molecular orbitals, the magnetism, and the absorption spectra are studied. The simultaneous appearance of large magnetic moments, significant band gaps, and plasmon resonances in the visible spectral region leads to novel multi-functional nanomaterials for applications in drug delivery, magnetic resonance imaging, and photo-responsive agents. © 2013 Elsevier B.V. All rights reserved.

  5. Magnetic and transport properties of discontinuous metal-oxides multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Dinia, A.; Schmerber, G.; Ulhaq, C.; El Bahraoui, T

    2003-02-15

    We report on structural, magnetic and transport properties of Al{sub 2}O{sub 3}/CoFe discontinuous multilayers deposited by RF sputtering at room temperature on silicon substrate. Transmission electron microscopy observations show that these multilayers consist of discontinuous layers of CoFe particles embedded in an insulating Al{sub 2}O{sub 3} matrix. This is further supported by magnetization measurements showing the presence at room temperature of both superparamagnetic and ferromagnetic components. The current-in-plane resistivity of the discontinuous multilayers has shown a negative magnetoresistance due to a spin-dependent tunneling between the CoFe magnetic particles through the insulating Al{sub 2}O{sub 3} barrier. The magnetoresistance response gives rise to two spin-dependent tunneling contributions. A contribution at small applied fields due to ferromagnetic particles and a contribution at larger magnetic applied fields due to a superparamagnetic particles.

  6. Magnetic properties of Fe/NiO/Fe(001) trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Biagioni, P. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)]. E-mail: paolo.biagioni@polimi.it; Brambilla, A. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Portalupi, M. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Rougemaille, N. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Schmid, A.K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Lanzara, A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Department of Physics, University of California at Berkeley, Berkeley, CA 94720 (United States); Vavassori, P. [INFM - Dipartimento di Fisica, Universita di Ferrara, Via Paradiso 12, 44100 Ferrara (Italy); Zani, M. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Finazzi, M. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Duo, L. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Ciccacci, F. [INFM - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)

    2005-04-15

    We have investigated the magnetic properties of epitaxially grown Fe/NiO/Fe(001) trilayers, for different thicknesses of the NiO spacer. Magneto Optical Kerr Effect has been exploited to study the in-plane magnetization reversal processes in the iron layers. We found that the NiO thickness t{sub AFM} has a critical value t{sub C} for the magnetic coupling between the Fe layers: for t{sub AFM}magnetization directions align perpendicularly, with zero applied field, while the alignment is collinear for thicker spacers. A phenomenological model has been developed to reproduce and discuss the results. Complementary information has been obtained by means of spin polarized low energy electron microscopy.

  7. Magnetic properties of checkerboard lattice: a Monte Carlo study

    Science.gov (United States)

    Jabar, A.; Masrour, R.; Hamedoun, M.; Benyoussef, A.

    2017-06-01

    The magnetic properties of ferrimagnetic mixed-spin Ising model in the checkerboard lattice are studied using Monte Carlo simulations. The variation of total magnetization and magnetic susceptibility with the crystal field has been established. We have obtained a transition from an order to a disordered phase in some critical value of the physical variables. The reduced transition temperature is obtained for different exchange interactions. The magnetic hysteresis cycles have been established. The multiples hysteresis cycle in checkerboard lattice are obtained. The multiples hysteresis cycle have been established. The ferrimagnetic mixed-spin Ising model in checkerboard lattice is very interesting from the experimental point of view. The mixed spins system have many technological applications such as in domain opto-electronics, memory, nanomedicine and nano-biological systems. The obtained results show that that crystal field induce long-range spin-spin correlations even bellow the reduced transition temperature.

  8. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Araujo, J. F. D. F.; Bruno, A. C.; Louro, S. R. W. [Department of Physics, Pontifícia Universidade Católica do Rio de Janeiro, Rio de Janeiro 22451-900 (Brazil)

    2015-10-15

    We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer’s sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10{sup −8} Am{sup 2} was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

  9. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles.

    Science.gov (United States)

    Araujo, J F D F; Bruno, A C; Louro, S R W

    2015-10-01

    We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme. A magnetic moment sensitivity of 8.5 × 10(-8) Am(2) was obtained with this configuration. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F-127, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.

  10. Thermodynamic properties of the magnetized Coulomb crystal lattices

    Science.gov (United States)

    Kozhberov, A. A.

    2016-08-01

    It is thought that Coulomb crystals of ions with hexagonal close-packed lattice may form in the crust of strongly-magnetized neutron stars (magnetars). In this work we are trying to verify this prediction assuming that the direction of the magnetic field corresponds to the minimum of the zero-point energy. We also continue a detailed study of vibration modes and thermodynamic properties of magnetized Coulomb crystals in a wide range of temperatures and magnetic fields. It is demonstrated that the total Helmholtz free energy of the body-centered cubic Coulomb crystal is always lower than that of the Coulomb crystal with hexagonal close-packed or face-centered cubic lattice, which casts doubt on the hypothesis above.

  11. Magnetic Properties of Nd-Group V Compounds

    DEFF Research Database (Denmark)

    Bak, Poul Erik; Lindgård, Per-Anker

    1973-01-01

    The Nd monopnictides NdP, NdAs and NdSb are simple cubic type I antiferromagnets in which the crystal-field splitting is larger than the exchange energy. The magnetic properties are calculated by means of a mean-field theory including crystal-field and magnetoelastic effects. The calculations are...

  12. Structural analysis and magnetic properties of Fe/Bi system

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y.; Nakanishi, Y.; Yoshimoto, N.; Daibo, M.; Nakamura, M.; Yoshizawa, M

    2003-05-01

    We have investigated the structure and magnetic properties of Fe/Bi multilayers and trilayers by RHEED, XRD, XRR, XPS and SQUID. The samples were grown by molecular beam epitaxy method. It was found that the synthesis of the multilayer is very difficult. However, we successfully grown Fe/Bi trilayers by adopting the appropriate growth conditions.

  13. Structural and magnetic properties of epitaxial Fe/Cu multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Y. E-mail: t5101008@iwate-u.ac.jp; Nakanishi, Y.; Yoshimoto, N.; Yamaguchi, A.; Nakamura, M.; Yoshizawa, M

    2004-05-01

    We have grown FCC-Fe/Cu multilayers by molecular beam epitaxy method. The structural and magnetic properties were studied by RHEED, XRD and magnetoresistance measurement (MR). The RHEED images confirmed that Fe/Cu multilayers were epitaxially grown on Cu(1 0 0). Furthermore, a clear negative MR was observed. The buffer layer condition for MR effect will be discussed.

  14. Confinining properties of QCD in strong magnetic backgrounds

    Directory of Open Access Journals (Sweden)

    Bonati Claudio

    2017-01-01

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

  15. Defects, phase transformations and magnetic properties of lithium ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, R.K.

    1977-03-01

    Achieving suitable magnetic properties in ceramic ferrites through thermomechanical treatments rather than through varying the processing and fabrication parameters alone has been investigated. Ferrimagnetic lithium ferrite and some other spinel structure materials were chosen for this investigation. Extensive characterization of phase transformations and lattice defects was done.

  16. Magnetic and ferroelectric properties of multiferroic RMn2O5

    Science.gov (United States)

    Noda, Y.; Kimura, H.; Fukunaga, M.; Kobayashi, S.; Kagomiya, I.; Kohn, K.

    2008-10-01

    The magnetic and ferroelectric properties of multiferroic RMn2O5 (R = Y, Tb, Ho, Er, Tm) are reviewed based on recent neutron diffraction and dielectric measurements. Successive phase transitions of magnetic and dielectric ordering were found to occur simultaneously in this system. The characteristic magnetic ordering of the system exhibits an incommensurate-commensurate phase transition, and again transitions to an incommensurate phase. Special attention is given to the magnetic structure in order to discuss the mechanism for the introduction of ferroelectric polarization. For all the compounds examined, the spin configuration for Mn4+ and Mn3+ ions in the commensurate magnetic phase, where spontaneous electric polarization occurs, was determined to be a transverse spiral spin structure propagating along the c-axis. By contrast, the alignment of the induced 4f moment of R3+ ions showed variation, depending on the character of each of the elements. Corresponding responses to external fields such as a magnetic field, hydrostatic pressure etc at low temperature are strongly dependent on the rare earth element present in the RMn2O5 system. The so-called colossal magnetoelectric effect in this system can be easily interpreted by the phase transition from the magnetic incommensurate and weak ferroelectric phase to the commensurate and ferroelectric phase.

  17. Investigation of magnetic properties for oblique deposited granular films by magnetic field annealing

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Bangmin [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Ge Shihui, E-mail: gesh@lzu.edu.cn [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China); Zuo Huaping; Xiao Yuhua; Wang Guowei; Zhang Li [Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, Lanzhou University, Lanzhou 730000 (China)

    2010-08-15

    A series of (Fe{sub 57}Co{sub 24}Ni{sub 4}Nb{sub 2}B{sub 13}){sub x}-(SiO{sub 2}){sub 1-x} nano-granular thin films were fabricated by magnetron sputtering with different oblique incidence angle {theta} and excellent soft magnetic properties are achieved. Based on the results of magnetic field anneal at different temperature T{sub a}, it is evidenced that orientation of atomic pairs contributes to the annealing treatment, and could manipulate magnetic anisotropy. The damping coefficient {alpha} decreases with increasing angle {theta} and this is ascribed to the anisotropy dissipation.

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

    CERN Document Server

    Getzlaff, Mathias

    2010-01-01

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

  19. Effects of electric field on magnetic properties of MnxGe_{1-x} diluted magnetic semiconductors

    Science.gov (United States)

    Assefa, Gezahegn; Singh, P.

    2016-03-01

    We report the effect of external electric field (EEF) on the magnetic properties of MnxGe_{1-x}, diluted magnetic semiconductor. We present a Kondo Lattice Model type Hamiltonian with exchange coupling between localized spins, itinerant holes and the EEF. The magnetization, the dispersion and critical temperature (Tc) are calculated for different values of EEF parameters (α) using double time temperature-dependent Green function formalism. The enhancement of the (Tc) with the EEF is shown to be very distinct and is in agreement with recent experimental observation and much required for spintronics applications and devices.

  20. Magnetic properties of self-assembled iron nanoparticle arrays

    Science.gov (United States)

    Farrell, Dorothy

    Nanoparticles of Fe were synthesized via thermal decomposition of iron pentacarbonyl, Fe(CO)5, in the presence of surfactants. Heterogeneously nucleating particles from Pt seeds led to high moment, minimally oxidized Fe particles 4.5--9 nm in diameter. Homogeneous nucleation of particles in the presence of an excess of oleic acid led to formation of partially oxidized particles, consisting of an Fe core and an oxide shell, 9--19 nm in diameter. Once synthesized, the particles were dispersed in hexane, and the hexane evaporated from the dispersion. During the evaporation, the particles self-assembled to form particle superlattices. The size and quality of the particle arrays depended on particle and surfactant concentration and drying conditions. Transmission electron microscopy (TEM) was used to characterize the size and structure of both particles and particle superlattices. Structural evidence for magnetic interactions between particles in the arrays was observed. Samples of hcp superlattices of 6.6 nm, high moment Fe particles displayed a preference for odd numbers of layers. This was not observed in arrays of low moment particles, and has not been reported for non-magnetic particles. The magnetic properties of dilute particle suspensions and dried particle arrays were measured using a Quantum Design MPMS magnetometer. The hysteretic and remanent behavior of both the dispersions and dried assemblies were indicative of the existence of dipole interactions between particles. Differences in the magnetic behavior of dispersions and arrays indicated that dipole interaction effects depend on the size and structure of particle assemblies. Magnetizing interactions play a larger role in the large, close-packed arrays than in the smaller, loosely-associated clusters contained in the dispersions. The magnetizing effects in the arrays can be enhanced by decreasing the interparticle spacing. The arrays were also magnetically anisotropic, with magnetic properties depending on

  1. Macroscopic Invisibility Cloaking of Visible Light

    CERN Document Server

    Chen, Xianzhong; Zhang, Jingjing; Jiang, Kyle; Pendry, John B; Zhang, Shuang

    2010-01-01

    Invisibility cloaks of light, which used to be confined to the imagination, have now been turned into a scientific reality, thanks to the enabling theoretical tools of transformation optics and conformal mapping. Inspired by those theoretical works, the experimental realisation of electromagnetic invisibility cloaks has been reported at various electromagnetic frequencies. All the invisibility cloaks demonstrated thus far, however, have relied on nano- or micro-fabricated artificial composite materials with spatially varying electromagnetic properties, which limit the size of the cloaked region to a few wavelengths. Here we report realisation of a macroscopic volumetric invisibility cloak constructed from natural birefringent crystals. The cloak operates at visible frequencies and is capable of hiding three-dimensional objects of the scale of centimetres and millimetres. Our work opens avenues for future applications with macroscopic cloaking devices.

  2. Effect of HD Process on Microstructure and Hard Magnetic Properties of NdFeAlB Magnet

    Institute of Scientific and Technical Information of China (English)

    姜忠良; 陈秀云; 陈晓东; 石大立; 杨昌平; 朱静

    2002-01-01

    The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than that of traditional ball milling (BM) magnet, while the remanence and the maximum energy product of HD magnet are lower. Microstructure analysis shows that some fine un-sintered powders are distributed at the grain boundaries of HD magnet. X-ray diffraction (XRD) analysis reveals that the degree of easy axis alignment of HD magnet is lower. Some ideas to improve the current HD process were proposed.

  3. Magnetic properties of sintered high energy sm-co and nd-fe-b magnets

    Directory of Open Access Journals (Sweden)

    Talijan Nadežda M.

    2006-01-01

    Full Text Available Magnetic properties of permanent magnetic materials based on intermetallic compounds of Sm-Co and Nd-Fe-B are in direct dependence on the microstructure. In the first part of this paper, having in mind the importance of the regime of sintering and heat treatment to obtain the optimal magnetic structure, yet another approach in defining the most adequate technological parameters of the sintering process for applied heat treatment conditions was made. The goal of these investigations was to use the correlation that exists between sintering conditions (temperature and time and intensity of the diffraction peak of the (111 plane of the SmCo5 phase to optimize. In the second part a brief overview of high energy magnetic materials based on Nd-Fe-B is presented with special emphasis to the current research and development of high remanent nanocomposite magnetic materials based on Nd-Fe-B alloys with a reduced Nd content. Part of experimental results gained during research of the sintering process of SmCo5 magnetic materials were realized and published earlier. The scientific meeting devoted to the 60th anniversary of Frankel’s theory of sintering was an opportunity to show once more the importance and role of sintering in optimization of the magnetic microstructure of sintered Sm Co5 magnetic materials.

  4. Synthesis, characterization and magnetic properties of carbon nanotubes decorated with magnetic MIIFe2O4 nanoparticles

    Science.gov (United States)

    Ali, Syed Danish; Hussain, Syed Tajammul; Gilani, Syeda Rubina

    2013-04-01

    In this study, a simple, efficient and reproducible microemulsion method was applied for the successful decoration of carbon nanotubes (CNTs) with magnetic MIIFe2O4 (M = Co, Ni, Cu, Zn) nanoparticles. The structure, composition and morphology of the prepared nanocomposite materials were characterized using X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). The magnetic properties were investigated by the vibrating sample magnetometer (VSM). The SEM results illustrated that large quantity of MIIFe2O4 nanoparticles were uniformly decorated around the circumference of CNTs and the sizes of the nanoparticles ranged from 15 to 20 nm. Magnetic hysteresis loop measurements revealed that all the MIIFe2O4/CNTs nanocomposites displayed ferromagnetic behavior at 300 K and can be manipulated using an external magnetic field. The CoFe2O4/CNTs nanocomposite showed maximum value of saturation magnetization which was 37.47 emu g-1. The as prepared MIIFe2O4/CNTs nanocomposites have many potential application in magnetically guided targeted drug delivery, clinical diagnosis, electrochemical biosensing, magnetic data storage and magnetic resonance imaging.

  5. Effects of oxygen and carbon on the magnetic properties and microstructure of Sm2Co17 permanent magnets

    Institute of Scientific and Technical Information of China (English)

    TIAN Jianjun; ZHANG Shengen; QU Xuanhui

    2007-01-01

    The research on the sintered Sm2Co17 permanent magnets prepared by metal injection molding is still at the exploratory stage. Carbon and oxygen are two key factors that influence the magnetic properties. In this article, the effects of oxygen and carbon on the properties and microstructure of the magnets have been studied. The results indicate that oxygen consumes the effective Sm content of the magnets and forms Sm2O3-the non-magnetism phase, which result in the deterioration of the magnetic properties. Besides, the magnetic properties decrease in evidence with increasing carbon content. The main factor that affects the magnetic properties is the deterioration of the microstructure of the magnets. The Sm(Co, Cu)5 phase decreases, whereas the cell size increases with the increase of the carbon content. When the carbon content is above 0.43 wt.%, the Sm(Co, Cu)5 phase is not enough to form a uniform cellular microstructure. Thus the magnetic properties disappear. ZrC is detected in the magnets by XRD when the carbon content is above 0.21 wt.%. ZrC also reduces the properties of the magnets.

  6. Magnetic properties of lanthanoid(III) phthalocyaninato triple-decker complexes in an external magnetic field and electronic transport properties for molecular spintronics

    Energy Technology Data Exchange (ETDEWEB)

    Katoh, K; Yamamoto, K; Breedlove, B K; Yamashita, M [Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki-Aza-Aoba, Aoba-Ku, Sendai 980-8578 (Japan); Kajiwara, T [Department of Chemistry, Faculty of Science, Nara Women' s University, Nishi-Machi, Kita-Uoya, Nara 630-8506 (Japan); Takeya, J, E-mail: yamashita@agnus.chem.tohoku.ac.jp [Institute of Scientific and Industrial Research, Osaka University, Mihogaoka, Ibaragi 567-0047 (Japan)

    2011-07-06

    Lanthanoid phthalocyaninato complexes of Dy{sub 2}(obPc){sub 3} (1) and Tb{sub 2}(obPc){sub 3} (2) are shown to be a single-molecule magnet. The relationships among the magnetic relaxation properties of 1 in a direct current (dc) magnetic field in comparison to 2 and the electronic properties of a cast film are discussed.

  7. Magnetic properties of amorphous Fe 78P 22 alloy obtained by mechanical grinding

    Science.gov (United States)

    Yelsukov, E. P.; Konygin, G. N.; Zagainov, A. V.; Barinov, V. A.

    1999-06-01

    The amorphous Fe 78P 22 alloy obtained by mechanical grinding was studied by X-ray analysis, Mössbauer spectroscopy and magnetic measurements. The measured values of the average hyperfine magnetic field H, mean magnetic moment per Fe atom mFe and Curie temperature Tc agree with those obtained earlier for electrodeposited and then ground samples and are in good qualitative agreement with the model describing macroscopic characteristics through the parameters of local environment but essentially disagree with the literature data for the samples obtained by rapidly quenching and only by electrochemical deposition.

  8. Magnetic antenna excitation of whistler modes. I. Basic properties

    Energy Technology Data Exchange (ETDEWEB)

    Urrutia, J. M.; Stenzel, R. L. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547 (United States)

    2014-12-15

    Properties of magnetic loop antennas for exciting electron whistler modes have been investigated in a large laboratory plasma. The parameter regime is that of large plasma frequency compared to the cyclotron frequency and signal frequency below half the cyclotron frequency. The antenna diameter is smaller than the wavelength. Different directions of the loop antenna relative to the background magnetic field have been measured for small amplitude waves. The differences in the topology of the wave magnetic field are shown from measurements of the three field components in three spatial directions. The helicity of the wave magnetic field and of the hodogram of the magnetic vector in space and time are clarified. The superposition of wave fields is used to investigate the properties of two antennas for small amplitude waves. Standing whistler waves are produced by propagating two wave packets in opposite directions. Directional radiation is obtained with two phased loops separated by a quarter wavelength. Rotating antenna fields, produced with phased orthogonal loops at the same location, do not produce directionality. The concept of superposition is extended in a Paper II to generate antenna arrays for whistlers. These produce nearly plane waves, whose propagation angle can be varied by the phase shifting the currents in the array elements. Focusing of whistlers is possible. These results are important for designing antennas on spacecraft or diagnosing and heating of laboratory plasmas.

  9. Magnetic properties of nanocrystalline KNbO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Golovina, I. S., E-mail: golovina@isp.kiev.ua; Shanina, B. D.; Kolesnik, S. P. [Institute of Semiconductor Physics of NAS of Ukraine, Pr. Nauky 41, 03028 Kyiv (Ukraine); Geifman, I. N. [Quality Engineering Education, Inc., Buffalo Grove, Illinois 60089 (United States); Andriiko, A. A. [National Technical University of Ukraine “KPI”, pr. Peremogy 37, 03056 Kyiv (Ukraine)

    2013-11-07

    Newly synthesized undoped and iron-doped nanoscale powders of KNbO{sub 3} are investigated using magnetic resonance and static magnetization methods in order to determine how the crystal size and doping affect the structure of magnetic defects and material properties. Although the bulk crystals of KNbO{sub 3} are nonmagnetic, the undoped KNbO{sub 3} powder with average particle size of 80 nm exhibits magnetic properties. The ferromagnetic resonance signal and the magnetization curve registered on the powder are thoroughly analyzed. It is concluded that the appearance of the defect driven ferromagnetism in the undoped powder is due to the nano-size of the particles. This effect disappears in the iron-doped KNbO{sub 3} powder with particle sizes above 300 nm. In case of low doping (<1 mol. % Fe), a new electron paramagnetic resonance signal with g{sub eff} = 4.21 is found out in the KNbO{sub 3}:Fe powder. Such a signal has not been observed in the bulk crystals of KNbO{sub 3}:Fe. We suppose that this signal corresponds to individual paramagnetic Fe{sup 3+} ions having rhombic symmetry.

  10. Magnetic properties of Fe1-xMnx/Fe nanocomposites

    DEFF Research Database (Denmark)

    Anhøj, Thomas Aarøe; Jacobsen, Claus Schelde; Mørup, Steen

    2004-01-01

    We have prepared nanocomposites of mixtures of ferromagnetic alpha-Fe and antiferromagnetic gamma-Fe50Mn50 nanoparticles, and studied their magnetic and structural properties by magnetization measurements, Mössbauer spectroscopy, and x-ray diffraction. A sample consisting of a 1:1 mixture...... of the two materials showed enhanced coercivity, but almost negligible exchange bias at room temperature after field cooling from 520 K. However, samples with higher content of gamma-Fe50Mn50 showed significant exchange bias. The mechanisms for exchange bias and enhanced coercivity in the system...

  11. Optical Writing of Magnetic Properties by Remanent Photostriction.

    Science.gov (United States)

    Iurchuk, V; Schick, D; Bran, J; Colson, D; Forget, A; Halley, D; Koc, A; Reinhardt, M; Kwamen, C; Morley, N A; Bargheer, M; Viret, M; Gumeniuk, R; Schmerber, G; Doudin, B; Kundys, B

    2016-09-02

    We present an optically induced remanent photostriction in BiFeO_{3}, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO_{3}/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO_{3}. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

  12. Optical Writing of Magnetic Properties by Remanent Photostriction

    Science.gov (United States)

    Iurchuk, V.; Schick, D.; Bran, J.; Colson, D.; Forget, A.; Halley, D.; Koc, A.; Reinhardt, M.; Kwamen, C.; Morley, N. A.; Bargheer, M.; Viret, M.; Gumeniuk, R.; Schmerber, G.; Doudin, B.; Kundys, B.

    2016-09-01

    We present an optically induced remanent photostriction in BiFeO3 , resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3 . Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.

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

    Science.gov (United States)

    Trepte, Kai; Schwalbe, Sebastian; Seifert, Gotthard

    2015-07-14

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

  14. Characteristics of Magnetic Properties of Substituted Hexagonal Ferrites

    Directory of Open Access Journals (Sweden)

    Vladimir Jancarik

    2006-01-01

    Full Text Available The samples of barium hexaferrite BaFe12-2x(Me1Me2xO19 with x from 0.0 to 0.6 were prepared by variousmethods. The cationic preference of mainly divalent Me1 = Zn, Co, Ni, Sn ions and tetravalent Me2 = Ti, Zr, Ir, Sn, Ru ionsand their combinations in substituted Ba ferrites was investigated. The substitutions were performed to reduce the grain sizeand high magnetic uniaxial anisotropy field of the M-type Ba ferrite without affecting the magnetic polarisation. The goal isto reach the properties of ferrite proper for high-density magnetic recording and microwave absorption devices. Magneticproperties were determined as a function of the substitution level x. The specific saturation magnetic polarisation Js–m andremanence Js–rincreased with small x due to the substitution of non-magnetic and less magnetic ions in 4f1 and 4f2 sites. Thesteep decrease of coercivity Hc with increasing x may be caused by the Co2+ preference of 4f2 site and Ti4+or Zr4+ions preference of 2b and slightly in 4f1 sites. The temperature coefficient of the coercivity TKHc was very low (0.01kA.m-1.°C-1for the Co-Zr substitutions and positive for the rest of samples.

  15. Electronic and magnetic properties of small rhodium clusters

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-24

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

  16. Magnetic and microstructural properties of nanocrystalline exchange coupled PrFeB permanent magnets

    Science.gov (United States)

    Goll, D.; Seeger, M.; Kronmüller, H.

    1998-05-01

    Nanocrystalline exchange coupled Pr 2Fe 14B single-phase and Pr 2Fe 14B+α-Fe two-phase magnets with grain sizes of about 20 nm were produced using the melt-spinning procedure. In the stoichiometric Pr 2Fe 14B composition a significantly enhanced remanence of JR=0.95 T was achieved in comparison with conventional Pr-rich and therefore decoupled isotropic PrFeB magnets ( JR⩽0.5 JS=0.78 T). In the composite magnets with overstoichiometric Fe a further enhancement of the remanence is possible. Values up to JR=1.42 T and ( BH) max=180.7 kJ/m 3 were obtained. As there exists no spin reorientation in PrFeB magnets, our attention was not only directed to the magnetic behaviour at room temperature but also to the magnetic properties in the whole ferromagnetic temperature range. The microstructural parameters Neff, αK and αex describing the influence of the non-ideal microstructure and the effect of the exchange coupling on the coercive field were determined within the framework of the nucleation model from the temperature dependence of the coercive field. Furthermore, reversibility measurements of the demagnetization curves in the second quadrant give important information about the magnetization processes in exchange coupled magnets. Moreover, we have investigated the law of approach to ferromagnetic saturation of the single-phase magnet in comparison with the decoupled one. The magnetic results are correlated with TEM investigations of the real microstructure.

  17. Macroscopic theory for capillary-pressure hysteresis.

    Science.gov (United States)

    Athukorallage, Bhagya; Aulisa, Eugenio; Iyer, Ram; Zhang, Larry

    2015-03-03

    In this article, we present a theory of macroscopic contact angle hysteresis by considering the minimization of the Helmholtz free energy of a solid-liquid-gas system over a convex set, subject to a constant volume constraint. The liquid and solid surfaces in contact are assumed to adhere weakly to each other, causing the interfacial energy to be set-valued. A simple calculus of variations argument for the minimization of the Helmholtz energy leads to the Young-Laplace equation for the drop surface in contact with the gas and a variational inequality that yields contact angle hysteresis for advancing/receding flow. We also show that the Young-Laplace equation with a Dirichlet boundary condition together with the variational inequality yields a basic hysteresis operator that describes the relationship between capillary pressure and volume. We validate the theory using results from the experiment for a sessile macroscopic drop. Although the capillary effect is a complex phenomenon even for a droplet as various points along the contact line might be pinned, the capillary pressure and volume of the drop are scalar variables that encapsulate the global quasistatic energy information for the entire droplet. Studying the capillary pressure versus volume relationship greatly simplifies the understanding and modeling of the phenomenon just as scalar magnetic hysteresis graphs greatly aided the modeling of devices with magnetic materials.

  18. Magnetic and electrical properties of In doped cobalt ferrite nanoparticles

    Science.gov (United States)

    Nongjai, Razia; Khan, Shakeel; Asokan, K.; Ahmed, Hilal; Khan, Imran

    2012-10-01

    Nanoparticles of CoFe2O4 and CoIn0.15Fe1.85O4 ferrites were prepared by citrate gel route and characterized to understand their structural, electrical, and magnetic properties. X-ray diffraction and Raman spectroscopy were used to confirm the formation of single phase cubic spinel structure. The average grain sizes from the Scherrer formula were below 50 nm. Microstructural features were obtained by scanning electron microscope and compositional analysis by energy dispersive spectroscopy. The hysteresis curve shows enhancement in coercivity while reduction in saturation magnetization with the substitution of In3+ ions. Enhancement of coercivity is attributed to the transition from multidomain to single domain nature. Electrical properties, such as dc resistivity as a function of temperature and ac conductivity as a function of frequency and temperature were studied for both the samples. The activation energy derived from the Arrhenius equation was found to increase in the doped sample. The dielectric constant (ɛ') and dielectric loss (tan δ) are also studied as a function of frequency and temperature. The variation of dielectric properties ɛ', tan δ, and ac conductivity (σac) with frequency reveals that the dispersion is due to Maxwell-Wagner type of interfacial polarization in general and the hopping of charge between Fe2+ and Fe3+ as well as between Co2+ and Co3+ ions at B-sites. Magnetization and electrical property study showed its dominant dependence on the grain size.

  19. Scaling macroscopic aquatic locomotion

    Science.gov (United States)

    Gazzola, Mattia; Argentina, Mederic; Mahadevan, Lakshminarayanan

    2014-11-01

    Inertial aquatic swimmers that use undulatory gaits range in length L from a few millimeters to 30 meters, across a wide array of biological taxa. Using elementary hydrodynamic arguments, we uncover a unifying mechanistic principle characterizing their locomotion by deriving a scaling relation that links swimming speed U to body kinematics (tail beat amplitude A and frequency ω) and fluid properties (kinematic viscosity ν). This principle can be simply couched as the power law Re ~ Swα , where Re = UL / ν >> 1 and Sw = ωAL / ν , with α = 4 / 3 for laminar flows, and α = 1 for turbulent flows. Existing data from over 1000 measurements on fish, amphibians, larvae, reptiles, mammals and birds, as well as direct numerical simulations are consistent with our scaling. We interpret our results as the consequence of the convergence of aquatic gaits to the performance limits imposed by hydrodynamics.

  20. Magnetic structure and magnetic transport properties of graphene nanoribbons with sawtooth zigzag edges.

    Science.gov (United States)

    Wang, D; Zhang, Z; Zhu, Z; Liang, B

    2014-12-23

    The magnetic structure and magnetic transport properties of hydrogen-passivated sawtooth zigzag-edge graphene nanoribbons (STGNRs) are investigated theoretically. It is found that all-sized ground-state STGNRs are ferromagnetic and always feature magnetic semiconductor properties, whose spin splitting energy gap E(g) changes periodically with the width of STGNRs. More importantly, for the STGNR based device, the dual spin-filtering effect with the perfect (100%) spin polarization and high-performance dual spin diode effect with a rectification ratio about 10(10) can be predicted. Particularly, a highly effective spin-valve device is likely to be realized, which displays a giant magnetoresistace (MR) approaching 10(10)%, which is three orders magnitude higher than the value predicted based on the zigzag graphene nanoribbons and six orders magnitude higher than previously reported experimental values for the MgO tunnel junction. Our findings suggest that STGNRs might hold a significant promise for developing spintronic devices.

  1. Magnetic properties of ultrathin tetragonal Heusler D022-Mn3Ge perpendicular-magnetized films

    Science.gov (United States)

    Sugihara, A.; Suzuki, K. Z.; Miyazaki, T.; Mizukami, S.

    2015-05-01

    We investigated the crystal structure and magnetic properties of Manganese-germanium (Mn3Ge) films having the tetragonal D022 structure, with varied thicknesses (5-130 nm) prepared on chromium (Cr)-buffered single crystal MgO(001) substrates. A crystal lattice elongation in the in-plane direction, induced by the lattice mismatch between the D022-Mn3Ge and the Cr buffer layer, increased with decreasing thickness of the D022-Mn3Ge layer. The films exhibited clear magnetic hysteresis loops with a squareness ratio close to unity, and a step-like magnetization reversal even at a 5-nm thickness under an external field perpendicular to the film's plane. The uniaxial magnetic anisotropy constant of the films showed a reduction to less than 10 Merg/cm3 in the small thickness range (≤20 nm), likely due to the crystal lattice elongation in the in-plane direction.

  2. Structure and magnetic properties of bulk nanocrystalline Nd-Fe-B permanent magnets prepared by hot pressing and hot deformation

    Institute of Scientific and Technical Information of China (English)

    SONG Jie; YUE Ming; ZUO Jianhua; ZHANG Zirui; LIU Weiqiang; ZHANG Dongtao; ZHANG Jiuxing

    2013-01-01

    Structure and magnetic properties were studied for bulk nanocrystalline Nd-Fe-B permanent magnets that were prepared at 650 ℃ for 3 min under 300 MPa using the SPS-3.20-MK-V sintering machine and the hot pressed magnets were then submitted to hot deformation with height reduction of 50%,60%,70%,80%,and 85%.Effects of height reduction (HR) and deformation temperature on the structure and magnetic properties of the magnets were investigated.The crystal structure was evaluated by means of X-ray diffraction (XRD) and the microstructure was observed by transmission electron microscopy (TEM).The magnetic properties of the magnets were investigated by vibrating sample magnetometer (VSM).As the height reduction increased,the remanence (Br) of the magnets increased first,peaks at 1.3 T with HR=60%,then decreased again,and the coercivity (Hci) of the magnets decreased monotonically.On the other hand,as the deformation temperature increased,the Br of the magnets increased first,peaks at 1.36 T with HR=60%,then decreased again,and the Hci of the magnets decreased monotonically.Under optimal conditions,the hot deformed magnet possessed excellent magnetic properties as Br=l.36 T,Hci=1143 kA/m,and (BH)max=370 kJ/m3,suggesting the good potential of the magnets in practical applications.

  3. The effect of magnetic annealing on crystallographic texture and magnetic properties of Fe-2.6% Si

    Energy Technology Data Exchange (ETDEWEB)

    Salih, M.Z., E-mail: mohammedzs2007@hotmail.com [Institut für Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6, D-38678 Clausthal-Zellerfeld (Germany); Uhlarz, M. [Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, D-01328 Dresden (Germany); Pyczak, F. [Instiute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, D-21502 Geesthacht (Germany); Brokmeier, H.-G. [Institut für Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6, D-38678 Clausthal-Zellerfeld (Germany); Instiute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, D-21502 Geesthacht (Germany); Weidenfeller, B. [Institut für Elektrochemie, Abteilung für Materialwissenschaft, Arnold-Sommerfeld-Straße 6, D-38678 Clausthal-Zellerfeld (Germany); Al-hamdany, N. [Institut für Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6, D-38678 Clausthal-Zellerfeld (Germany); Gan, W.M. [Instiute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, D-21502 Geesthacht (Germany); Zhong, Z.Y. [Institut für Werkstoffkunde und Werkstofftechnik, TU Clausthal, Agricolastraße 6, D-38678 Clausthal-Zellerfeld (Germany); Schell, N. [Instiute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, D-21502 Geesthacht (Germany)

    2015-05-01

    The effect of magnetic annealing on crystallographic texture, microstructure, defects density and magnetic properties of a Fe-2.6% Si steel has been analyzed. After two stage cold rolling (75% and 60% cold rolled) with intermediate annealing process at (600 °C/1 h) the sample annealed at 600 °C for one hour during which different magnetic field of 0, 7 and 14 T were applied has been investigated. The effect of defects density after cold rolling process on the recrystallization texture and magnetic properties was characterized. Heat treatments under a high external field of 14 T show a drastic improvement of the magnetic properties such as significantly increased permeability. Neutron diffraction measurements were preferred for measurement of the bulk sample texture so that sufficient grain statistics were obtained. Because of its small wavelength (0.05–0.2 Å) Synchrotron diffraction with high photon energy was used to evaluate the defects density by a modified Williamson–Hall plot. - Highlights: • We show the effect of the magnetic annealing after intermediate cold rolling on the crystallographic texture and magnetic properties. • Due the coarse grained we used Neutron diffraction for texture measurement. • We used hysteresis recorder to measure the magnetic properties. • The magnetic annealing leads to drastic improvements of the magnetic properties such as significantly increased permeability. • We show the effect of defect density on the crystallographic texture and magnetic properties.

  4. Magnetic properties of electrodeposited Ni‒P alloys with varying phosphorus content

    Science.gov (United States)

    Knyazev, A. V.; Fishgoit, L. A.; Chernavskii, P. A.; Safonov, V. A.; Filippova, S. E.

    2017-02-01

    The effect thermal treatment has on the magnetic properties (magnetization, saturation magnetization, and coercivity) of Ni‒P alloys prepared via electrodeposition is studied. The process of amorphous Ni‒P alloys devitrification is investigated by differential scanning calorimetry. The effects of chemical composition and thermal treatment on magnetic properties of the alloys are revealed.

  5. Ab initio study of ZnCoO diluted magnetic semiconductor and its magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Lardjane, S., E-mail: soumia.lardjane@utbm.fr [Laboratoire d' Etudes et de Recherches, les Procedes et les Surfaces, IRTES-LERMPS, UTBM, Site de Montbeliard, 90010 Belfort Cedex (France); Laboratoire d' Etude et Prediction des Materiaux, Unite de Recherche Materiaux et Energies Renouvelables, LEPM-URMER, Universite de Tlemcen (Algeria); Merad, G. [Laboratoire d' Etude et Prediction des Materiaux, Unite de Recherche Materiaux et Energies Renouvelables, LEPM-URMER, Universite de Tlemcen (Algeria); Fenineche, N.; Billard, A. [Laboratoire d' Etudes et de Recherches, les Procedes et les Surfaces, IRTES-LERMPS, UTBM, Site de Montbeliard, 90010 Belfort Cedex (France); Faraoun, H.I. [Laboratoire d' Etude et Prediction des Materiaux, Unite de Recherche Materiaux et Energies Renouvelables, LEPM-URMER, Universite de Tlemcen (Algeria)

    2013-02-25

    Highlights: Black-Right-Pointing-Pointer We have studied the electronic and magnetic properties of ZnCoO using the GGA and GGA + U. Black-Right-Pointing-Pointer The GGA + U calculations show that the ZnCoO system shows semiconductor band structures. Black-Right-Pointing-Pointer The obtained magnetic moment on Co is larger in the GGA + U case. Black-Right-Pointing-Pointer Antiferromagnetic order between nearest-neighbour magnetic ions was predicted. Black-Right-Pointing-Pointer Our results suggest that the range of magnetic interaction is short in ZnCoO. - Abstract: Transition metal-doped wide band gap semiconductors, such as ZnO, attract much attention due to the theoretical prediction that ZnO is a room temperature ferromagnetic semiconductor [1,2]. Very controversial experimental and theoretical papers have been published to discuss the origin of ferromagnetic ordering and the relevance of the Curie temperature (T{sub C}) of Co-doped ZnO [3-5]. In order to get better insight, electronic structure of Co{sub x}Zn{sub 1-x}O magnetic semiconductor was investigated via first principle calculations. The generalised gradient approximations (GGA) and the GGA with Hubbard U correction (GGA + U) in the framework of density functional theory (DFT) have been used. Calculations are done for different doping concentrations to discuss the contribution of different atoms in magnetic moments and magnetic coupling.

  6. Magnetic Properties of Diluted Magnetic Semiconductor Hg0.89Mn0.11Te

    Institute of Scientific and Technical Information of China (English)

    WANG Zewen; JIE Wanqi

    2015-01-01

    The magnetization of Hg0.89Mn0.11Te single crystal grown by vertical Bridgman method was studied by using superconducting quantum interference device magnetometer (SQUID Magnetometer). First, magnetization measurements were done under various magnetic ifeld strengths from-20 kOe to 20 kOe at 5 K, 15 K, and 77 K, respectively. Then, the magnetizations were measured with continuous changes of temperature in the range from 5 K to 300 K under the magnetic ifeld of 0.1 kOe and 10 kOe, respectively. The modiifed Brillouin function was well fitted with the data of magnetization vs. magnetic field strength. The analysis indicated that there was an antiferromagnetic exchange coupling among Mn2+ions. The results of reciprocal susceptibility vs. temperature ift Curie-Weiss law very well at the temperatures above 40 K, but deviate from the law from 5 K to 40 K, which shows that the antiferromagnetic exchange coupling among Mn2+ions increases in the lower temperature range below 40 K. The experimental result was explained by extending higher-order terms in the calculation of susceptibility and fitted by a power law function. The measurements reveal that Hg0.89Mn0.11Te possesses paramagnetic properties at temperatures from 5 K to 300 K.

  7. Magnetic properties of zero-magnetostrictive nanocrystalline Fe-Zr-Nb-B soft magnetic alloys with high magnetic induction

    Energy Technology Data Exchange (ETDEWEB)

    Makino, A.; Bitoh, T. E-mail: teruo_bitoh@akita-pu.ac.jp; Kojima, A.; Inoue, A.; Masumoto, T

    2000-06-02

    The soft magnetic properties of the nanocrystalline Fe-Zr-Nb-B alloys have been investigated. The best soft magnetic properties have been obtained for the Fe{sub 85.5}Zr{sub 2}Nb{sub 4}B{sub 8.5} alloy. The alloy shows a high permeability of 60,000 at 1 kHz, a high magnetic induction of 1.64 T and zero magnetostriction, simultaneously. The alloy also exhibits a very low core loss of 0.09 W/kg at 1.4 T and 50 Hz, which is extremely lower than that of Fe-Si-B amorphous. The nanocrystalline Fe-Zr-Nb-B alloy is therefore suitable for a core material for pole transformers.

  8. Macroscopic-microscopic mass models

    CERN Document Server

    Nix, J R; Nix, J Rayford; Moller, Peter

    1995-01-01

    We discuss recent developments in macroscopic-microscopic mass models, including the 1992 finite-range droplet model, the 1992 extended-Thomas-Fermi Strutinsky-integral model, and the 1994 Thomas-Fermi model, with particular emphasis on how well they extrapolate to new regions of nuclei. We also address what recent developments in macroscopic-microscopic mass models are teaching us about such physically relevant issues as the nuclear curvature energy, a new congruence energy arising from a greater-than-average overlap of neutron and proton wave functions, the nuclear incompressibility coefficient, and the Coulomb redistribution energy arising from a central density depression. We conclude with a brief discussion of the recently discovered rock of metastable superheavy nuclei near 272:110 that had been correctly predicted by macroscopic-microscopic models, along with a possible new tack for reaching an island near 290:110 beyond our present horizon.

  9. Structure and magnetic properties of nanostructured Ni-ferrite

    Science.gov (United States)

    Albuquerque, A. S.; Ardisson, J. D.; Macedo, W. A. A.; López, J. L.; Paniago, R.; Persiano, A. I. C.

    2001-05-01

    The structural and magnetic properties of NiFe 2O 4 ultrafine powders synthesized by coprecipitation, a nonconventional method of preparation, were investigated. The samples were obtained by annealing at relatively low temperatures (300-600°C) and characterized by X-ray diffraction, Mössbauer spectroscopy, and vibrating sample magnetometry. The average particle diameter ranges from 4 to 15 nm, as determined by X-ray diffraction. All nanometric powder samples presented strong superparamagnetic relaxation at room temperature and reduced magnetic hyperfine fields at -193°C. Magnetometry measurements indicated different magnetic behavior related with crystallinity of samples, coercivity as high as 168 Oe at 27°C, value that is nearly two times higher than coercivity of bulk Ni-ferrite.

  10. Structure and magnetic properties of nanostructured Ni-ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Albuquerque, A.S. E-mail: asa@urano.cdtn.br; Ardisson, J.D.; Macedo, W.A.A.; Lopez, J.L.; Paniago, R.; Persiano, A.I.C

    2001-05-01

    The structural and magnetic properties of NiFe{sub 2}O{sub 4} ultrafine powders synthesized by coprecipitation, a nonconventional method of preparation, were investigated. The samples were obtained by annealing at relatively low temperatures (300-600 deg. C) and characterized by X-ray diffraction, Moessbauer spectroscopy, and vibrating sample magnetometry. The average particle diameter ranges from 4 to 15 nm, as determined by X-ray diffraction. All nanometric powder samples presented strong superparamagnetic relaxation at room temperature and reduced magnetic hyperfine fields at -193 deg. C. Magnetometry measurements indicated different magnetic behavior related with crystallinity of samples, coercivity as high as 168 Oe at 27 deg. C, value that is nearly two times higher than coercivity of bulk Ni-ferrite.

  11. Structural and magnetic properties of Ni/Pt multilayers

    Science.gov (United States)

    Quiroga, Matías A.; Cabeza, Gabriela F.; Castellani, Norberto J.

    2007-10-01

    In this work, the variation of the magnetic moments of the Ni/Pt multilayers are studied using the linearized augmented plane waves (LAPW) method in the framework of the density functional theory (DFT) implemented in the version of WIEN2K program. The systems have been modeled by seven layers slab separated in z direction by a vacuum region of four substrate layers. We present the results of the dependence of the magnetic properties with respect to the thickness variation of the different multilayers. The modeling of these systems finds an important empirical support. Experiment and theory show the same trends for the magnetic moments: hybridization effects between Ni and Pt are mostly localized at the interface.

  12. Evaluating the effect of magnetocaloric properties on magnetic refrigeration performance

    DEFF Research Database (Denmark)

    Engelbrecht, Kurt; Bahl, Christian Robert Haffenden

    2010-01-01

    Active magnetic regenerator (AMR) refrigerators represent an alternative to vapor compression technology that relies on the magnetocaloric effect in a solid refrigerant. Magnetocaloric materials are in development and properties are reported regularly. Recently, there has been an emphasis...... on developing materials with a high entropy change with magnetization while placing lower emphasis on the adiabatic temperature change. This work uses model magnetocaloric materials and a numerical AMR model to predict how the temperature change and entropy change with magnetization interact and how they affect...... that exhibits a sharp peak in isothermal entropy change was shown to produce a significantly lower cooling power than a material with a wide peak in a practical AMR system. © 2010 American Institute of Physics...

  13. Magnetic Properties of Nanocrystalline Nickel-Cobalt Ferrites

    Science.gov (United States)

    Tiwari, D. K.; Villaseñor-Cendejas, L. M.; Thakur, A. K.

    2013-09-01

    In this study, the nanocrystalline nickel-cobalt ferrites were prepared via the citrate route method at . The samples were calcined at for 3 h. The crystalline structure and the single-phase formations were confirmed by X-ray diffraction (XRD) measurements. Prepared materials showed the cubic spinel structure with m3m symmetry and Fd3m space group. The analyses of XRD patterns were carried out using POWD software. It gave an estimation of lattice constant “” of 8.3584 Å, which was in good agreement with the results reported in JCPDS file no. 742081. The crystal size of the prepared materials calculated by Scherer’s formula was 27.6 nm and the electrical conductivity was around . The permeability component variations with frequency were realized. The magnetic properties of the prepared materials were analyzed by a vibrating sample magnetometer (VSM). It showed a saturation magnetization of and the behavior of a hard magnet.

  14. SYNTHESIS AND MAGNETIC PROPERTIES OF Zn SPINEL CERAMICS

    Directory of Open Access Journals (Sweden)

    Huber Š.

    2013-06-01

    Full Text Available We present the synthesis and characterization of ZnTM2O4 spinels (where TM = Cr3+, Mn3+, Fe3+ and Co3+, which are possible impurity phases in TM-doped ZnO that represent a large family of diluted magnetic semiconductors (DMS. The aim of our study was to find a uniform technique simplifying the whole synthesis of zinc spinels and their magnetic characterization. The synthesis was carried out by a conventional ceramic route with one calcination and two sintering steps. The structure of the prepared samples was proofed by X-ray diffraction analysis and magnetic properties were studied using SQUID magnetometer. Excluding the cobalt spinel, all spinels were singe phase and showed antiferromagnetic behavior.

  15. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively. Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→ pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  16. Magnetic properties related to thermal treatment of pyrite

    Institute of Scientific and Technical Information of China (English)

    WANG Lei; PAN YongXin; LI JinHua; QIN HuaFeng

    2008-01-01

    Detailed rock magnetic experiments were conducted on high-purity natural crystalline pyrite and its products of thermal treatments in both argon and air atmospheres. In argon atmosphere (reducing environment), the pyrite is altered by heating to magnetite and pyrrhotite; the latter is stable in argon atmosphere, and has coercive force and coercivity of remanence of ~20 and ~30 mT, respectively.Whereas in air, the pyrite is ultimately oxidized to hematite. First order reversal curve (FORC) diagram of the end product shows that the remanence coercivity of hematite is up to ~1400 mT. The corresponding thermal transformation process of pyrite in air can be simply summarized as pyrite→pyrrhotite→magnetite→hematite. These results are helpful for understanding of sedimentary magnetism, secondary chemical remanence and meteorolite magnetic properties.

  17. Micromorphology, microstructure and magnetic properties of sputtered garnet multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Marcelli, R. [CNR, Roma (Italy). Ist. di Elettronica dello Stato Solido; Padeletti, G.; Gambacorti, N.; Simeone, M.G.; Fiorani, D. [CNR, Monterotondo Stazione (Italy). Ist. di Chimica dei Materiali

    1998-12-31

    The growth technique, the micromorphological and microstructural characterization by means of atomic force microscopy (AFM) and secondary ions mass spectrometry (SIMS) as well as the magnetic properties of a novel class of magnetic multilayers, based on radio frequency (RF) sputtered thin amorphous garnet films, are presented. One, three and five thin film multilayers composed by amorphous pure yttrium iron garnet (a:YIG) and amorphous gadolinium gallium garnet (a:GGG) have been grown on GGG single crystal substrates. The multilayer interfaces have been found to be comparable in both, the three and five-layers structure. Low field susceptibility measurements, showed a paramagnetic behavior for the single layer YIG film. For the three and five layers samples, irreversibility effects were observed, giving evidence of magnetic clusters at the interface YIG/GGG.

  18. Resonant magnetic properties of gadolinium-gallium garnet single crystals

    Science.gov (United States)

    Bedyukh, A. R.; Danilov, V. V.; Nechiporuk, A. Yu.; Romanyuk, V. F.

    1999-03-01

    The results of experimental investigations of resonant magnetic properties of gadolinium-gallium garnet (GGG) single crystals at temperatures 4.2-300 K in the frequency range 1.6-9.3 GHz are considered. It is found that magnetic losses in GGG are determined by the initial splitting of energy levels for gadolinium ions in the garnet crystal lattice and by the dipole broadening. The width and shape of the electron paramagnetic resonance (EPR) line in the GGG crystal, whose asymmetry is manifested most strongly at low frequencies, can be explained by the influence of these factors. Magnetic losses in GGG increase with frequency and upon cooling. It is found that the EPR linewidth increases considerably with decreasing temperature due to the presence of rapidly relaxing impurities.

  19. Frequency-Dependent Properties of Magnetic Nanoparticle Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Majetich, Sara [Carnegie Mellon Univ., Pittsburgh, PA (United States)

    2016-05-17

    In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magnetic order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500

  20. Size-dependent magnetic properties of branchlike nickel oxide nanocrystals

    Science.gov (United States)

    Liu, Dan; Li, Dongsheng; Yang, Deren

    2017-01-01

    Branchlike nickel oxide nanocrystals with narrow size distribution are obtained by a solution growth method. The size-dependent of magnetic properties of the nickel oxides were investigated. The results of magnetic characterization indicate that the NiO nanocrystals with size below 12.8 nm show very weak ferromagnetic state at room temperature due to the uncompensated spins. Both of the average blocking temperature (Tb) and the irreversible temperature (Tirr) increase with the increase of nanoparticle sizes, while both the remnant magnetization and the coercivity at 300 K increase with the decrease of the particle sizes. Moreover, the disappearance of two-magnon (2M) band and redshift of one-phonon longitudinal (1LO) and two-phonon LO in vibrational properties due to size reduction are observed. Compared to the one with the spherical morphological, it is also found that nano-structured nickel oxides with the branchlike morphology have larger remnant magnetization and the coercivity at 5 K due to their larger surface-to-volume ratio and greater degree of broken symmetry at the surface or the higher proportion of broken bonds.

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

    Directory of Open Access Journals (Sweden)

    Jia-Jia Zheng

    2016-01-01

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

  2. The magnetic properties of the star Kepler-78

    Science.gov (United States)

    Moutou, C.; Donati, J.-F.; Lin, D.; Laine, R. O.; Hatzes, A.

    2016-06-01

    Kepler-78 is host to a transiting 8.5-h orbit super-Earth. In this paper, the rotation and magnetic properties of the planet host star are studied. We first revisit the Kepler photometric data for a detailed description of the rotation properties of Kepler-78, showing that the star seems to undergo a cycle in the spot pattern of ˜1300 d duration. We then use spectropolarimetric observations with Canada-France-Hawaii Telescope (CFHT)/ESPaDOnS to measure the circular polarization in the line profile of the star during its rotation cycle, as well as spectroscopic proxies of the chromospheric activity. The average field has a strength of 16 G. The magnetic topology is characterized by a poloidal and a toroidal component, encompassing 60 per cent and 40 per cent of the magnetic energy, respectively. Differential rotation is detected with an estimated rate of 0.105±0.039 rad d-1. Activity tracers vary with the rotation cycle of the star; there is no hint that a residual activity level is related to the planetary orbit at the precision of our data. The description of the star magnetic field's characteristics then may serve as input for models of interactions between the star and its close-by planet, e.g. Ohmic dissipation and unipolar induction.

  3. Static Magnetic Properties of AL800 Garnet Material

    Energy Technology Data Exchange (ETDEWEB)

    Kuharik, J. [Fermilab; Madrak, R. [Fermilab; Makarov, A. [Fermilab; Pellico, W. [Fermilab; Sun, S. [Fermilab; Tan, C. Y. [Fermilab; Terechkine, I. [Fermilab

    2017-05-17

    A second harmonic tunable RF cavity is being devel-oped for the Fermilab Booster. This device, which prom-ises reduction of the particle beam loss at the injection, transition, and extraction stages, employs perpendicularly biased garnet material for frequency tuning. The required range of the tuning is significantly wider than in previously built and tested tunable RF devices. As a result, the mag-netic field in the garnet comes fairly close to the gyromag-netic resonance line at the lower end of the frequency range. The chosen design concept of a tuner for the cavity cannot ensure uniform magnetic field in the garnet mate-rial; thus, it is important to know the static magnetic prop-erties of the material to avoid significant increase in the lo-cal RF loss power density. This report summarizes studies performed at Fermilab to understand variations in the mag-netic properties of the AL800 garnet material used to build the tuner of the cavity.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-15

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

  5. Electrical and Magnetic Properties of FeSi2 Nanowires

    Institute of Scientific and Technical Information of China (English)

    PENG Zu-Lin; S. Liang

    2008-01-01

    We report the characterization of serf-assembled epitaxially grown FeSi2 nanowires (NWs) in terms of electrical and magnetic properties. NWs grown by reactive deposition epitaxy (RDE) on silicon (110) show dimensions of 1Onm×5nm, and several micrometres in length. By using conductive-AFM (c-AFM), electron transport properties of one single NW is measured, resistivity of a single crystalline FeSi2 NW is estimated to be 225 μΩ·cm.Using superconducting quantum interference device (SQUID), we measure a magnetic moment of 0.3±0.1 Bohr magneton per iron atom for these FeSi2 NWs.

  6. The uncertainties of magnetic properties measurements of electrical sheet steel

    CERN Document Server

    Ahlers, H

    2000-01-01

    In this work, uncertainties in measurements of magnetic properties of Epstein- and single-sheet samples have been determined according to the 'Guide To The Expression Of Uncertainty In Measurement', [International Organization for Standardization (1993)]. They were calculated for the results at predicted values of parameters taking into account the non-linear dependences. The measurement results and the uncertainties are calculated simultaneously by a computer program.

  7. Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

    Science.gov (United States)

    Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

    2011-01-01

    The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

  8. Drug delivery property, bactericidal property and cytocompatibility of magnetic mesoporous bioactive glass

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi-Zhuo [The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University, Shanghai 200234 (China); Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China); Li, Yang [Shanghai Key Laboratory of Orthopedic Implant, Department of Orthopedic Surgery, Shanghai Ninth People' s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011 (China); Yu, Xi-Bin [The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University, Shanghai 200234 (China); Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China); Liu, Li-Na [Shanghai Key Laboratory of Orthopedic Implant, Department of Orthopedic Surgery, Shanghai Ninth People' s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011 (China); Zhu, Zhen-An, E-mail: zhuzhenan2006@126.com [Shanghai Key Laboratory of Orthopedic Implant, Department of Orthopedic Surgery, Shanghai Ninth People' s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011 (China); Guo, Ya-Ping, E-mail: ypguo@shnu.edu.cn [The Education Ministry Key Lab of Resource Chemistry, Shanghai Normal University, Shanghai 200234 (China); Shanghai Key Laboratory of Rare Earth Functional Materials, Shanghai Normal University, Shanghai 200234 (China)

    2014-08-01

    A multifunctional magnetic mesoporous bioactive glass (MMBG) has been widely used for a drug delivery system, but its biological properties have been rarely reported. Herein, the effects of mesopores and Fe{sub 3}O{sub 4} nanoparticles on drug loading–release property, bactericidal property and biocompatibility have been investigated by using mesoporous bioactive glass (MBG) and non-mesoporous bioactive glass (NBG) as control samples. Both MMBG and MBG have better drug loading efficiency than NBG because they possess ordered mesoporous channels, big specific surface areas and high pore volumes. As compared with MBG, the Fe{sub 3}O{sub 4} nanoparticles in MMBG not only provide magnetic property, but also improve sustained drug release property. For gentamicin-loaded MMBG (Gent-MMBG), the sustained release of gentamicin and the Fe{sub 3}O{sub 4} nanoparticles minimize bacterial adhesion significantly and prevent biofilm formation against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Moreover, the magnetic Fe{sub 3}O{sub 4} nanoparticles in MMBG can promote crucial cell functions such as cell adhesion, spreading and proliferation. The excellent biocompatibility and drug delivery property of MMBG suggest that Gent-MMBG has great potentials for treatment of implant-associated infections. - Highlights: • Multifunctional magnetic mesoporous bioactive glass is fabricated. • The bioactive glass has great biocompatibility. • The bioactive glass exhibits high drug loading–release properties. • The drug delivery system has bactericidal property. • Magnetic particles improve cell adhesion, spreading and proliferation.

  9. Optical and magnetic properties of PAA@Fe nanocomposite films

    Directory of Open Access Journals (Sweden)

    Jing-jing Zhang

    2013-07-01

    Full Text Available A simple method to fabricate porous anodic alumina films embedded with Fe is reported. The films exhibit vivid structural colors and magnetic properties after being synthesized by an ac electrodeposition method. The optical properties of the samples can be effectively tuned by varying the oxidation time of aluminum. The coercivity mechanism of the Fe nanowires in our case is consistent with fanning reversal mode. PAA@Fe films can be used in many areas including decoration, display and multifunctional anti-counterfeiting applications.

  10. Magnetic properties of point defects in proton irradiated diamond

    Energy Technology Data Exchange (ETDEWEB)

    Makgato, T.N., E-mail: Thuto.Makgato@students.wits.ac.za [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Sideras-Haddad, E. [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Center of Excellence in Strong Materials, Physics Building, University of the Witwatersrand, Johannesburg 2050 (South Africa); Ramos, M.A. [CMAM, Centro de Micro-Analisis de Materiales, Universidad Autónoma de Madrid, C/Faraday 3, Campus de Cantoblanco, E-28049 Madrid (Spain); Departamento de Fisica de la Materia Condensada, Condensed Matter Physics Center (IFIMAC) and Instituto Nicolás Cabrera, Universidad Autónoma de Madrid, 28049 Madrid (Spain); García-Hernández, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Climent-Font, A.; Zucchiatti, A.; Muñoz-Martin, A. [CMAM, Centro de Micro-Analisis de Materiales, Universidad Autónoma de Madrid, C/Faraday 3, Campus de Cantoblanco, E-28049 Madrid (Spain); Shrivastava, S. [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Erasmus, R. [School of Physics, University of the Witwatersrand, Johannesburg 2050 (South Africa); Center of Excellence in Strong Materials, Physics Building, University of the Witwatersrand, Johannesburg 2050 (South Africa)

    2016-09-01

    We investigate the magnetic properties of ultra-pure type-IIa diamond following irradiation with proton beams of ≈1–2 MeV energy. SQUID magnetometry indicate the formation of Curie type paramagnetism according to the Curie law. Raman and Photoluminescence spectroscopy measurements show that the primary structural features created by proton irradiation are the centers: GR1, ND1, TR12 and 3H. The Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulations together with SQUID observations show a strong correlation between vacancy production, proton fluence and the paramagnetic factor. At an average surface vacancy spacing of ≈1–1.6 nm and bulk (peak) vacancy spacing of ≈0.3-0.5 nm Curie paramagnetism is induced by formation of ND1 centres with an effective magnetic moment μ{sub eff}~(0.1–0.2)μ{sub B}. No evidence of long range magnetic ordering is observed in the temperature range 4.2-300 K. - Highlights: • Proton macro-irradiation of pure diamond creates fluence dependent paramagnetism. • The effective magnetic moment is found to be in the range μ{sub eff}~(0.1–0.2)μ{sub B}. • No evidence of long range magnetic ordering is observed.

  11. Synthesis and magnetic properties of single phase titanomagnetites

    Energy Technology Data Exchange (ETDEWEB)

    Schoenthal, W., E-mail: wms@andrew.cmu.edu; Liu, X.; Cox, T.; Laughlin, D. E.; McHenry, M. E. [Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Mesa, J. L.; Diaz-Michelena, M. [Instituto Nacional de Tecnica Aeroespacial, Madrid (Spain); Maicas, M. [Universidad Politecnica de Madrid, ISOM-ETSIT, Madrid (Spain)

    2014-05-07

    The focus of this paper is the study of cation distributions and resulting magnetizations in titanomagnetites (TMs), (1−x)Fe{sub 3}O{sub 4−x}Fe{sub 2}TiO{sub 4} solid solutions. TM remnant states are hypothesized to contribute to planetary magnetic field anomalies. This work correlates experimental data with proposed models for the TM pseudobinary. Improved synthesis procedures are reported for single phase Ulvöspinel (Fe{sub 2}TiO{sub 4}), and TM solid solutions were made using solid state synthesis techniques. X-ray diffraction and scanning electron microscopy show samples to be single phase solid solutions. M-H curves of TM75, 80, 85, 90, and 95 (TMX where X = at. % of ulvöspinel) were measured using a Physical Property Measurement System at 10 K, in fields of 0 to 8 T. The saturation magnetization was found to be close to that predicted by the Neel model for cation distribution in TMs. M-T curves of the remnant magnetization were measured from 10 K to 350 K. The remnant magnetization was acquired at 10 K by applying an 8 T field and then releasing the field. Experimental Neel temperatures are reported for samples in the Neel model ground state.

  12. Microscopic and magnetic properties of template assisted electrodeposited iron nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Irshad, M. I., E-mail: imrancssp@gmail.com; Mohamed, N. M., E-mail: noranimuti-mohamed@petronas.com.my; Yar, A., E-mail: asfandyarhargan@gmail.com [Department of Fundamental & Applied Sciences, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia); Ahmad, F., E-mail: faizahmad@petronas.com.my; Abdullah, M. Z., E-mail: zaki-abdullah@petronas.com.my [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, 31750 PERAK (Malaysia)

    2015-07-22

    Nanowires of magnetic materials such as Iron, nickel, cobalt, and alloys of them are one of the most widely investigated structures because of their possible applications in high density magnetic recording media, sensor elements, and building blocks in biological transport systems. In this work, Iron nanowires have been prepared by electrodeposition technique using Anodized Aluminium Oxide (AAO) templates. The electrolyte used consisted of FeSO{sub 4.}6H{sub 2}O buffered with H{sub 3}BO{sub 3} and acidized by dilute H{sub 2}SO{sub 4}. FESEM analysis shows that the asdeposited nanowires are parallel to one another and have high aspect ratio with a reasonably high pore-filing factor. To fabricate the working electrode, a thin film of copper (∼ 220 nm thick) was coated on back side of AAO template by e-beam evaporation system to create electrical contact with the external circuit. The TEM results show that electrodeposited nanowires have diameter around 100 nm and are polycrystalline in structure. Magnetic properties show the existence of anisotropy for in and out of plane configuration. These nanowires have potential applications in magnetic data storage, catalysis and magnetic sensor applications.

  13. Magnetic properties of Ni(II)-Mn(III) LDHs

    Energy Technology Data Exchange (ETDEWEB)

    Giovannelli, F., E-mail: fabien.giovannelli@univ-tours.fr [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France); Zaghrioui, M.; Autret-Lambert, C. [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France); Delorme, F.; Seron, A. [BRGM, 3 Avenue Claude Guillemin, BP 36009, 45060 Orleans Cedex 2 (France); Chartier, T.; Pignon, B. [LEMA, UMR 6157 CNRS-CEA, Universite Francois Rabelais, 3 place Jean Jaures, 41029 Blois (France)

    2012-11-15

    The synthesis of Ni{sub 1-x}Mn{sub x}(OH){sub 2}(CO{sub 3}){sub x/2}{center_dot}nH{sub 2}O Layered Double Hydroxides (LDHs) for x = 0.2, 0.25 and 0.33, their characterisation by electron microscopy, X-ray diffraction and their magnetic properties are reported in this study. When x increases, the crystallinity of the nanoparticles is improved. The low temperature magnetic behaviour of these compounds is characteristic of the competition between in plane ferromagnetic and interlayer antiferromagnetic interactions. The ferromagnetism is due to in plane Ni cations interaction and decreases when manganese content increases (Tc decreases from 26 to 15 K when x increases from 0.2 to 0.33). It was found that the substitution of Ni by Mn ions favours the in plane antiferromagnetic order. This study demonstrates that magnetic interactions occur in LDH with non magnetic interlayer anions. -- Highlights: Black-Right-Pointing-Pointer The synthesis of Ni{sub 1-x}Mn{sub x}(OH){sub 2}(CO{sub 3}){sub x/2}{center_dot}nH{sub 2}O Layered Double Hydroxides have been performed. Black-Right-Pointing-Pointer The low temperature magnetic behaviour of these compounds has been studied. Black-Right-Pointing-Pointer The substitution of Ni by Mn ions favours the in plane antiferromagnetic order.

  14. Magnetic and Magnetoelectric Properties of Rare Earth Molybdates

    Directory of Open Access Journals (Sweden)

    B. K. Ponomarev

    2012-01-01

    Full Text Available We present results on ferroelectric, magnetic, magneto-optical properties and magnetoelectric effect of rare earth molybdates (gadolinium molybdate, GMO, and terbium molybdate, TMO, and samarium molybdate, SMO, belonging to a new type of ferroelectrics predicted by Levanyuk and Sannikov. While cooling the tetragonal β-phase becomes unstable with respect to two degenerate modes of lattice vibrations. The β-β′ transition is induced by this instability. The spontaneous polarization appears as a by-product of the lattice transformation. The electric order in TMO is of antiferroelectric type. Ferroelectric and ferroelastic GMO and TMO at room temperature are paramagnets. At low temperatures GMO and TMO are antiferromagnetic with the Neel temperatures TN=0.3 K (GMO and TN=0.45 K (TMO. TMO shows the spontaneous destruction at 40 kOe magnetic field. Temperature and field dependences of the magnetization in TMO are well described by the magnetism theory of singlets at 4.2 K ≤ T ≤ 30 K. The magnetoelectric effect in SMO, GMO and TMO, the anisotropy of magnetoelectric effect in TMO at T = (1.8–4.2 K, the Zeeman effect in TMO, the inversion of the electric polarization induced by the laser beam are discussed. The correlation between the magnetic moment of rare earth ion and the magnetoelectric effect value is predicted. The giant fluctuations of the acoustic resonance peak intensity near the Curie point are observed.

  15. Properties of mesons in a strong magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Rui [Peking University, Department of Physics, State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Fu, Wei-jie [Universitaet Heidelberg, Institut fuer Theoretische Physik, Heidelberg (Germany); Liu, Yu-xin [Peking University, Department of Physics, State Key Laboratory of Nuclear Physics and Technology, Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China); Peking University, Center for High Energy Physics, Beijing (China)

    2016-06-15

    By extending the Φ-derivable approach in the Nambu-Jona-Lasinio model to a finite magnetic field we calculate the properties of pion, σ, and ρ mesons in a magnetic field at finite temperature not only in the quark-antiquark bound state scheme but also in the pion-pion scattering resonant state scenario. Our calculation as a result makes manifest that the masses of π{sup 0} and σ meson can be nearly degenerate at the pseudo-critical temperature which increases with increasing magnetic field strength, and the π{sup ±} mass ascends suddenly at almost the same critical temperature. Meanwhile the ρ mesons' masses decrease with the temperature but increase with the magnetic field strength. We also check the Gell-Mann-Oakes-Renner relation and find that the relation can be violated clearly with increasing temperature, and the effect of the magnetic field becomes pronounced around the critical temperature. With different criteria, we analyze the effect of the magnetic field on the chiral phase transition and find that the pseudo-critical temperature of the chiral phase cross, T{sub c}{sup χ}, is always enhanced by the magnetic field. Moreover, our calculations indicate that the ρ mesons will get melted as the chiral symmetry has not yet been restored, but the σ meson does not disassociate even at very high temperature. Particularly, it is the first to show that there does not exist a vector meson condensate in the QCD vacuum in the pion-pion scattering scheme. (orig.)

  16. Anisotropic magnetic properties of dysprosium iron garnet (DyIG)

    Energy Technology Data Exchange (ETDEWEB)

    Lahoubi, M; Younsi, W; Soltani, M-L [Department of Physics, Badji-Mokhtar University, BP 12 - 23000 Annaba (Algeria); Ouladdiaf, B, E-mail: mlahoubi@gmail.co [Institut Laue Langevin, BP 156 - 38042 Grenoble Cedex 9 (France)

    2010-01-01

    The magnetic properties of dysprosium iron garnet (DyIG) have been studied by performing high resolution powder neutron diffraction experiments and high dc fields magnetizations on single crystals. Among all the reflections (hkl) indexed in the nuclear cubic space group (CSG) Ia 3-bar d with h+k+l=2n and k=[000], the superstructure lines (hkl)* forbidden by the symmetry (222)* and (622)* are not observed in the patterns at all temperatures. The pattern at 130 K is well interpreted within the magnetic modes F belonging to the irreducible representation (IR) T{sub 1g} of the CSG and identified to the room temperature ferrimagnetic Neel model. The high magnetic field behavior of the spontaneous collinear magnetic structure (MS) along the easy axis (EA) <111> is isotropic. Below 130 K, the patterns exhibit additional magnetic superstructure lines. They are associated to the appearance of the spontaneous non collinear MS which is described in the subgroup of the CSG, R 3-bar c within the IR A{sub 2g}. A strong magnetization anisotropy (MA) is observed at 1.5 K in the low symmetry phases were the spin reorientation transition (SR) occur at T{sub RS}=14.5 K. The onset of MA is detected below two characteristic temperatures, Ta{sub 1}=125 K and Ta{sub 2}=75 K respectively to the hard axis (HA) <100> and <110>. Symmetry arguments are used in the framework of the theory of representation analysis (RA) applied to the subgroup of R 3-bar c, C2/c within the IR A{sub g}. It seems that this MA results essentially from the difference between the spontaneous non collinear MS and the field induced (FI) configurations. All results are discussed with previous neutrons studies.

  17. Nonaqueous magnetic nanoparticle suspensions with controlled particle size and nuclear magnetic resonance properties.

    Science.gov (United States)

    Meledandri, Carla J; Stolarczyk, Jacek K; Ghosh, Swapankumar; Brougham, Dermot F

    2008-12-16

    We report the preparation of monodisperse maghemite (gamma-Fe2O3) nanoparticle suspensions in heptane, by thermal decomposition of iron(III) acetylacetonate in the presence of oleic acid and oleylamine surfactants. By varying the surfactant/Fe precursor mole ratio during synthesis, control was exerted both over the nanocrystal core size, in the range from 3 to 6 nm, and over the magnetic properties of the resulting nanoparticle dispersions. We report field-cycling 1H NMR relaxation analysis of the superparamagnetic relaxation rate enhancement of nonaqueous suspensions for the first time. This approach permits measurement of the relaxivity and provides information on the saturation magnetization and magnetic anisotropy energy of the suspended particles. The saturation magnetization was found to be in the expected range for maghemite particles of this size. The anisotropy energy was found to increase significantly with decreasing particle size, which we attribute to increased shape anisotropy. This study can be used as a guide for the synthesis of maghemite nanoparticles with selected magnetic properties for a given application.

  18. Hematite nanoplates: Controllable synthesis, gas sensing, photocatalytic and magnetic properties.

    Science.gov (United States)

    Hao, Hongying; Sun, Dandan; Xu, Yanyan; Liu, Ping; Zhang, Guoying; Sun, Yaqiu; Gao, Dongzhao

    2016-01-15

    Uniform hematite (α-Fe2O3) nanoplates exposing {001} plane as basal planes have been prepared by a facile solvothermal method under the assistance of sodium acetate. The morphological evolution of the nanoplates was studied by adjusting the reaction parameters including the solvent and the amount of sodium acetate. The results indicated that both the adequate nucleation/growth rate and selective adsorption of alcohol molecules and acetate anions contribute to the formation of the plate-like morphology. In addition, the size of the nanoplates can be adjusted from ca. 180nm to 740nm by changing the reaction parameters. Three nanoplate samples with different size were selected to investigate the gas sensing performance, photocatalytic and magnetic properties. As gas sensing materials, all the α-Fe2O3 nanoplates exhibited high gas sensitivity and stability toward n-butanol. When applied as photocatalyst, the α-Fe2O3 nanoplates show high photodegradation efficiency towards RhB. Both the gas sensing performance and the photocatalytic property of the products exhibit obvious size-dependent effect. Magnetic measurements reveal that the plate-like α-Fe2O3 particles possess good room temperature magnetic properties.

  19. A Macroscopic Analogue of the Nuclear Pairing Potential

    Science.gov (United States)

    Dunlap, Richard A.

    2013-01-01

    A macroscopic system involving permanent magnets is used as an analogue to nucleons in a nucleus to illustrate the significance of the pairing interaction. This illustrates that the view of the total nuclear energy based only on the nucleon occupancy of the energy levels can yield erroneous results and it is only when the pairing interaction is…

  20. Diagnosis of bladder tumours in patients with macroscopic haematuria

    DEFF Research Database (Denmark)

    Gandrup, Karen L; Løgager, Vibeke B; Bretlau, Thomas

    2015-01-01

    OBJECTIVE: The aim of this study was to compare split-bolus computed tomography urography (CTU), magnetic resonance urography (MRU) and flexible cystoscopy in patients with macroscopic haematuria regarding the diagnosis of bladder tumours. MATERIALS AND METHODS: In this prospective study, 150...

  1. The Influence Of The Temperature Of Liquid Nitrogen On The Physical Properties Of Powder Magnetic Composites

    Directory of Open Access Journals (Sweden)

    Kapelski D.

    2015-06-01

    Full Text Available The paper presents the physical properties of soft magnetic iron composites and Nd-Fe-B bonded permanent magnets measured at room temperature and at liquid nitrogen. The objective of research was a determination of influence of liquid nitrogen temperature on the magnetic properties, resistivity and mechanical properties of different powder magnetic materials. Research was carried out for three powder materials: soft magnetic, i.e. Somaloy 700, AncorLam and hard magnetic powder MQP-B used for production of bonded magnets. Composite specimens were prepared by compression moulding technology.

  2. Synthesis, photoluminescence and magnetic properties of barium vanadate nanoflowers

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jing [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Chongqing University of Science and Technology, Chongqing 401331 (China); Hu, Chenguo, E-mail: hucg@cqu.edu.cn [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Xi, Yi [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China); Peng, Chen [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Wan, Buyong; He, Xiaoshan [Department of Applied Physics, Chongqing University, 174 Shapingba Street, Chongqing 400044 (China)

    2011-06-15

    Graphical abstract: The flower-shaped barium vanadate was obtained for the first time. The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. Research highlights: {yields} In the paper, the flower-shaped barium vanadate were obtained for the first time. The CHM method used here is new and simple for preparation of barium vanadate. {yields} The photoluminescence and magnetic properties of the barium vanadate nanoflowers were investigated at room temperature. The strong bluish-green emission was observed. {yields} The ferromagnetic behavior of the barium vanadate nanoflowers was found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g. {yields} The mechanisms of PL and magnetic property of barium vanadate nanoflowers have been discussed. -- Abstract: The flower-shaped barium vanadate has been obtained by the composite hydroxide mediated (CHM) method from V{sub 2}O{sub 5} and BaCl{sub 2} at 200 {sup o}C for 13 h. XRD and XPS spectrum of the as-synthesized sample indicate it is hexagonal Ba{sub 3}V{sub 2}O{sub 8} with small amount of Ba{sub 3}VO{sub 4.8} coexistence. Scan electron microscope and transmission electron microscope display that the flower-shaped crystals are composed of nanosheets with thickness of {approx}20 nm. The UV-visible spectrum shows that the barium vanadate sample has two optical gaps (3.85 eV and 3.12 eV). Photoluminescence spectrum of the barium vanadate flowers exhibits a visible light emission centered at 492 and 525 nm which might be attributed to VO{sub 4} tetrahedron with T{sub d} symmetry in Ba{sub 3}V{sub 2}O{sub 8}. The ferromagnetic behavior of the barium vanadate nanoflowers has been found with saturation magnetization of about 83.50 x 10{sup -3} emu/g, coercivity of 18.89 Oe and remnant magnetization of 4.63 x 10{sup -3} emu/g, which is mainly due to the presence of a non

  3. Magnetic properties changes due to hydrocarbon contaminated groundwater table fluctuations

    Science.gov (United States)

    Ameen, Nawrass

    2013-04-01

    This study aims to understand the mechanisms and conditions which control the formation and transformation of ferro(i)magnetic minerals caused by hydrocarbon contaminated groundwater, in particular in the zone of fluctuating water levels. The work extends previous studies conducted at the same site. The study area is a former military air base at Hradčany, Czech Republic (50°37'22.71"N, 14°45'2.24"E). The site was heavily contaminated with petroleum hydrocarbons, due to leaks in petroleum storage tanks and jet fuelling stations over years of active use by the Soviet Union, which closed the base in 1991. The site is one of the most important sources of high quality groundwater in the Czech Republic. In a previous study, Rijal et al. (2010) concluded that the contaminants could be flushed into the sediments as the water level rose due to remediation processes leading to new formation of magnetite. In this previous study three different locations were investigated; however, from each location only one core was obtained. In order to recognize significant magnetic signatures versus depth three cores from each of these three locations were drilled in early 2012, penetrating the unsaturated zone, the groundwater fluctuation (GWF) zone and extending to about one meter below the groundwater level (~2.3 m depth at the time of sampling). Magnetic susceptibility (MS) profiles combined with other magnetic properties were analyzed to obtain a significant depth distribution of the ferro(i)magnetic concentration. Sediment properties, hydrocarbon content and bacterial activity were additionally studied. The results show that the highest ferrimagnetic mineral concentrations exist between 1.4-1.9 m depth from the baseline which is interpreted as the top of the GWF zone. Spikes of MS detected in the previous studies turned out to represent small-scale isolated features, but the trend of increasing MS values from the lowermost position of the groundwater table upward was verified

  4. Direct hydrothermal synthesis and magnetic property of titanate nanotubes doped magnetic metal ions

    Institute of Scientific and Technical Information of China (English)

    Meili Wang; Gongbao Song; Jian Li; Landong Miao; Baoshu Zhang

    2008-01-01

    Pure titanate nanotubes and titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions were synthesized by the hydrothermal method. In this process, titanate nanotubes were first prepared synchronously with doping Fe3+/Ni2+/Mn2+ ions. The morphology,structure, thermal stability and magnetic property of titanate nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), and magnetic measurement. The titanate nanotubes transformed into the anatase titania nanocrystals,and further the mixture of anatase and rutile titania along with increasing temperature. The results indicate that the titanate nanotubes doped with Fe3+/Ni2+/Mn2+ ions are paramagnetic behaviors.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1990-01-01

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

  6. Structure organization and magnetic properties of microscale ferrogels: The effect of particle magnetic anisotropy

    Science.gov (United States)

    Ryzhkov, Aleksandr V.; Melenev, Petr V.; Balasoiu, Maria; Raikher, Yuriy L.

    2016-08-01

    The equilibrium structure and magnetic properties of a ferrogel object of small size (microferrogel(MFG)) are investigated by coarse-grained molecular dynamics. As a generic model of a microferrogel (MFG), a sample with a lattice-like mesh is taken. The solid phase of the MFG consists of magnetic (e.g., ferrite) nanoparticles which are mechanically linked to the mesh making some part of its nodes. Unlike previous models, the finite uniaxial magnetic anisotropy of the particles, as it is the case for real ferrogels, is taken into account. For comparison, two types of MFGs are considered: MFG-1, which dwells in virtually non-aggregated state independently of the presence of an external magnetic field, and MFG-2, which displays aggregation yet under zero field. The structure states of the samples are analyzed with the aid of angle-resolved radial distribution functions and cluster counts. The results reveal the crucial role of the matrix elasticity on the structure organization as well as on magnetization of both MFGs. The particle anisotropy, which plays insignificant role in MFG-1 (moderate interparticle magnetodipole interaction), becomes an important factor in MFG-2 (strong interaction). There, the restrictions imposed on the particle angular freedom by the elastic matrix result in notable diminution of the particle chain lengths as well as the magnetization of the sample. The approach proposed enables one to investigate a large variety of MFGs, including those of capsule type and to purposefully choose the combination of their magnetoelastic parameters.

  7. Rainbow correlation imaging with macroscopic twin beam

    Science.gov (United States)

    Allevi, Alessia; Bondani, Maria

    2017-06-01

    We present the implementation of a correlation-imaging protocol that exploits both the spatial and spectral correlations of macroscopic twin-beam states generated by parametric downconversion. In particular, the spectral resolution of an imaging spectrometer coupled to an EMCCD camera is used in a proof-of-principle experiment to encrypt and decrypt a simple code to be transmitted between two parties. In order to optimize the trade-off between visibility and resolution, we provide the characterization of the correlation images as a function of the spatio-spectral properties of twin beams generated at different pump power values.

  8. Fingerprint Feature Extraction Based on Macroscopic Curvature

    Institute of Scientific and Technical Information of China (English)

    Zhang Xiong; He Gui-ming; Zhang Yun

    2003-01-01

    In the Automatic Fingerprint Identification System (AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characteristic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.

  9. Fingerprint Feature Extraction Based on Macroscopic Curvature

    Institute of Scientific and Technical Information of China (English)

    Zhang; Xiong; He; Gui-Ming; 等

    2003-01-01

    In the Automatic Fingerprint Identification System(AFIS), extracting the feature of fingerprint is very important. The local curvature of ridges of fingerprint is irregular, so people have the barrier to effectively extract the fingerprint curve features to describe fingerprint. This article proposes a novel algorithm; it embraces information of few nearby fingerprint ridges to extract a new characterstic which can describe the curvature feature of fingerprint. Experimental results show the algorithm is feasible, and the characteristics extracted by it can clearly show the inner macroscopic curve properties of fingerprint. The result also shows that this kind of characteristic is robust to noise and pollution.

  10. Magnetic properties of manganese based one-dimensional spin chains.

    Science.gov (United States)

    Asha, K S; Ranjith, K M; Yogi, Arvind; Nath, R; Mandal, Sukhendu

    2015-12-14

    We have correlated the structure-property relationship of three manganese-based inorganic-organic hybrid structures. Compound 1, [Mn2(OH-BDC)2(DMF)3] (where BDC = 1,4-benzene dicarboxylic acid and DMF = N,N'-dimethylformamide), contains Mn2O11 dimers as secondary building units (SBUs), which are connected by carboxylate anions forming Mn-O-C-O-Mn chains. Compound 2, [Mn2(BDC)2(DMF)2], contains Mn4O20 clusters as SBUs, which also form Mn-O-C-O-Mn chains. In compound 3, [Mn3(BDC)3(DEF)2] (where DEF = N,N'-diethylformamide), the distorted MnO6 octahedra are linked to form a one-dimensional chain with Mn-O-Mn connectivity. The magnetic properties were investigated by means of magnetization and heat capacity measurements. The temperature dependent magnetic susceptibility of all the three compounds could be nicely fitted using a one-dimensional S = 5/2 Heisenberg antiferromagnetic chain model and the value of intra-chain exchange coupling (J/k(B)) between Mn(2+) ions was estimated to be ∼1.1 K, ∼0.7 K, and ∼0.46 K for compounds 1, 2, and 3, respectively. Compound 1 does not undergo any magnetic long-range-order down to 2 K while compounds 2 and 3 undergo long-range magnetic order at T(N) ≈ 4.2 K and ≈4.3 K, respectively, which are of spin-glass type. From the values of J/k(B) and T(N) the inter-chain coupling (J(⊥)/k(B)) was calculated to be about 0.1J/k(B) for both compounds 2 and 3, respectively.

  11. E and S hysteresis model for two-dimensional magnetic properties

    CERN Document Server

    Soda, N

    2000-01-01

    We define an effective hysteresis model of two-dimensional magnetic properties for the magnetic field analysis. Our hysteresis model is applicable to both alternating and rotating flux conditions. Moreover, we compare the calculated results with the measured ones, and verify the accuracy of this model. We can calculate iron losses in the magnetic materials exactly. As a result, it is shown that the hysteresis model is generally applicable to two-dimensional magnetic properties of some kinds of magnetic materials.

  12. Calixarene-stabilised cobalt nanoparticle rings: Self-assembly and collective magnetic properties

    DEFF Research Database (Denmark)

    Wei, A; Tripp, SL; Liu, J

    2009-01-01

    ) and entropic loss, analogous to the thermodynamic balance of forces governing supramolecular self-assembly. Examination of the Co nanoparticle rings by electron holography (an electron microscopy technique for imaging in-plane magnetic induction) reveals the existence of chiral flux closure (FC) domains...... at room temperature, comprising a 'racemic' mixture of clockwise and anticlockwise states. Furthermore, these FC polarisations can be reversed by applying out-of-plane magnetic pulses (Hz) in alternating directions. This switching behaviour has no known analogy at the macroscopic level, and may represent...

  13. Fundamentals and applications of magnetic materials

    CERN Document Server

    Krishnan, Kannan M

    2016-01-01

    Students and researchers looking for a comprehensive textbook on magnetism, magnetic materials and related applications will find in this book an excellent explanation of the field. Chapters progress logically from the physics of magnetism, to magnetic phenomena in materials, to size and dimensionality effects, to applications. Beginning with a description of magnetic phenomena and measurements on a macroscopic scale, the book then presents discussions of intrinsic and phenomenological concepts of magnetism such as electronic magnetic moments and classical, quantum, and band theories of magnetic behavior. It then covers ordered magnetic materials (emphasizing their structure-sensitive properties) and magnetic phenomena, including magnetic anisotropy, magnetostriction, and magnetic domain structures and dynamics. What follows is a comprehensive description of imaging methods to resolve magnetic microstructures (domains) along with an introduction to micromagnetic modeling. The book then explores in detail size...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-01

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

  15. CoCrTa thin films for magnetic recording media: structure, magnetic properties and time-dependence effect

    NARCIS (Netherlands)

    Phan le kim, P.L.K.

    This thesis has been devoted to deposition process, structures, magnetic properties and time-dependence effect of CoCrTa magnetic thin films for recording media. The experimental study began from Chapter 5 by investigating properties of single layer CoCrTa thin films, produced under different

  16. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    Science.gov (United States)

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo; Arami, Hamed; Ferguson, R. Mathew; Krishnan, Kannan M.

    2014-06-01

    Sensitivity and spatial resolution in magnetic particle imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer's magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance.

  17. Self-consistent magnetic properties of magnetite tracers optimized for magnetic particle imaging measured by ac susceptometry, magnetorelaxometry and magnetic particle spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Frank; Remmer, Hilke; Kuhlmann, Christian; Wawrzik, Thilo [Institute of Electrical Measurement and Fundamental Electrical Engineering, TU Braunschweig, Hans-Sommer-Str. 66, D-38106 Braunschweig (Germany); Arami, Hamed; Ferguson, R. Mathew [Department of Materials Science and Engineering Box 352120, University of Washington, Seattle, WA 98195 (United States); Krishnan, Kannan M., E-mail: kannanmk@uw.edu [Department of Materials Science and Engineering Box 352120, University of Washington, Seattle, WA 98195 (United States)

    2014-06-01

    Sensitivity and spatial resolution in magnetic particle imaging are affected by magnetic properties of the nanoparticle tracers used during imaging. Here, we have carried out a comprehensive magnetic characterization of single-core iron oxide nanoparticles that were designed for MPI. We used ac susceptometry, fluxgate magnetorelaxometry, and magnetic particle spectroscopy to evaluate the tracer's magnetic core size, hydrodynamic size, and magnetic anisotropy. Our results present a self-consistent set of magnetic and structural parameters for the tracers that is consistent with direct measurements of size using transmission electron microscopy and dynamic light scattering and that can be used to better understand their MPI performance.

  18. The magnetic properties of the planet host star Kepler-78

    CERN Document Server

    Moutou, Claire; Lin, Doug; Laine, Randy; Hatzes, Artie

    2016-01-01

    Kepler-78 is host to a transiting 8.5-hour orbit super-Earth. In this paper, the rotation and magnetic properties of the planet host star are studied. We first revisit the Kepler photometric data for a detailed description of the rotation properties of Kepler-78, showing that the star seems to undergo a cycle in the spot pattern of ~1,300 day duration. We then use spectropolarimetric observations with CFHT/ESPaDOnS to measure the circular polarization in the line profile of the star during its rotation cycle, as well as spectroscopic proxies of the chromospheric activity. The average field has an amplitude of 16 G. The magnetic topology is characterized by a poloidal and a toroidal component, encompassing 60% and 40% of the magnetic energy, respectively. Differential rotation is detected with an estimated rate of 0.105+-0.039 rad/d. Activity tracers vary with the rotation cycle of the star; there is no hint that a residual activity level is related to the planetary orbit at the precision of our data. The desc...

  19. Size-dependent magnetic properties of iron oxide nanoparticles

    Science.gov (United States)

    Patsula, Vitalii; Moskvin, Maksym; Dutz, Silvio; Horák, Daniel

    2016-01-01

    Uniform iron oxide nanoparticles in the size range from 10 to 24 nm and polydisperse 14 nm iron oxide particles were prepared by thermal decomposition of Fe(III) carboxylates in the presence of oleic acid and co-precipitation of Fe(II) and Fe(III) chlorides by ammonium hydroxide followed by oxidation, respectively. While the first method produced hydrophobic oleic acid coated particles, the second one formed hydrophilic, but uncoated, nanoparticles. To make the iron oxide particles water dispersible and colloidally stable, their surface was modified with poly(ethylene glycol) and sucrose, respectively. Size and size distribution of the nanoparticles was determined by transmission electron microscopy, dynamic light scattering and X-ray diffraction. Surface of the PEG-functionalized and sucrose-modified iron oxide particles was characterized by Fourier transform infrared (FT-IR) and Raman spectroscopy and thermogravimetric analysis (TGA). Magnetic properties were measured by means of vibration sample magnetometry and specific absorption rate in alternating magnetic fields was determined calorimetrically. It was found, that larger ferrimagnetic particles showed higher heating performance than smaller superparamagnetic ones. In the transition range between superparamagnetism and ferrimagnetism, samples with a broader size distribution provided higher heating power than narrow size distributed particles of comparable mean size. Here presented particles showed promising properties for a possible application in magnetic hyperthermia.

  20. Properties of magnetic nickel/porous-silicon composite powders

    Directory of Open Access Journals (Sweden)

    Toshihiro Nakamura

    2012-09-01

    Full Text Available The magnetic and photoluminescence (PL properties of nickel/porous-silicon (Ni/PSi composite powders are investigated. Ni/PSi composite powders are prepared by stain etching of Si powder in a HF/HNO3 solution followed by electroless plating of Ni nanoparticles on the stain-etched PSi powder in a NiCl2 solution. The Ni/PSi powders exhibit hydrophillicity, superparamagnetism caused by the deposited Ni nanoparticles, and orange-red PL owing to the nanostructured PSi surface. The degree of magnetization decreases with increasing Ni plating time, indicating its dependence on the size of the Ni nanoparticles. The Ni/PSi composite powders also show a stronger magnetization as compared to that of the Ni-particle-plated Si powder. The stronger magnetization results from the larger surface area of PSi. The PL intensity, peak wavelength, and lifetime of Ni/PSi are strongly dependent on the NiCl2 concentration. This dependence is due to the different thickness of the oxide overlayer on the PSi surface formed during the Ni plating process. The existence of the oxide overlayer also results in a small change in the PL intensity against excitation time.

  1. The structural and magnetic properties of dual phase cobalt ferrite.

    Science.gov (United States)

    Gore, Shyam K; Jadhav, Santosh S; Jadhav, Vijaykumar V; Patange, S M; Naushad, Mu; Mane, Rajaram S; Kim, Kwang Ho

    2017-05-31

    The bismuth (Bi(3+))-doped cobalt ferrite nanostructures with dual phase, i.e. cubic spinel with space group Fd3m and perovskite with space group R3c, have been successfully engineered via self-ignited sol-gel combustion route. To obtain information about the phase analysis and structural parameters, like lattice constant, Rietveld refinement process is applied. The replacement of divalent Co(2+) by trivalent Bi(3+) cations have been confirmed from energy dispersive analysis of the ferrite samples. The micro-structural evolution of cobalt ferrite powders at room temperature under various Bi(3+) doping levels have been identified from the digital photoimages recorded using scanning electron microscopy. The hyperfine interactions, like isomer shift, quadrupole splitting and magnetic hyperfine fields, and cation distribution are confirmed from the Mossbauer spectra. Saturation magnetization is increased with Bi(3+)-addition up to x = 0.15 and then is decreased when x = 0.2. The coercivity is increased from 1457 to 2277 G with increasing Bi(3+)-doping level. The saturation magnetization, coercivity and remanent ratio for x = 0.15 sample is found to be the highest, indicating the potential of Bi(3+)-doping in enhancing the magnetic properties of cobalt ferrite.

  2. Relationship Between Solar Wind Speed and Coronal Magnetic Field Properties

    CERN Document Server

    Fujiki, Ken'ichi; Iju, Tomoya; Hakamada, Kazuyuki; Kojima, Masayoshi

    2015-01-01

    We have studied the relationship between the solar-wind speed $[V]$ and the coronal magnetic-field properties (a flux expansion factor [$f$] and photospheric magnetic-field strength [$B_{\\mathrm{S}}$]) at all latitudes using data of interplanetary scintillation and solar magnetic field obtained for 24 years from 1986 to 2009. Using a cross-correlation analyses, we verified that $V$ is inversely proportional to $f$ and found that $V$ tends to increase with $B_{\\mathrm{S}}$ if $f$ is the same. As a consequence, we find that $V$ has extremely good linear correlation with $B_{\\mathrm{S}}/f$. However, this linear relation of $V$ and $B_{\\mathrm{S}}/f$ cannot be used for predicting the solar-wind velocity without information on the solar-wind mass flux. We discuss why the inverse relation between $V$ and $f$ has been successfully used for solar-wind velocity prediction, even though it does not explicitly include the mass flux and magnetic-field strength, which are important physical parameters for solar-wind accele...

  3. Magnetic properties of electrodeposited Co-W thin films

    Energy Technology Data Exchange (ETDEWEB)

    Admon, U.; Dariel, M.P.; Grunbaum, E.; Lodder, J.C.

    1987-09-01

    Thin films of Co-W, 300--500 A thick, were electrodeposited at various compositions under a wide range of plating conditions. The saturation magnetization, coercivity, and squareness ratio of the films were derived from the parallel (in-plane) and perpendicular hysteresis loops, measured by using a vibrating sample magnetometer. The magnetic properties of the films are strongly related to their microstructure. The nonmagnetic alloying element (W) affects the saturation magnetization via the dilution mechanism. The in-plane coercivity, which increases with increasing content of the hexagonal phase and with decreasing degree of (0001)h texture, is in the range of 100--600 Oe for the crystalline deposits and decreases to a few oersteds for amorphous deposits. The in-plane squareness ratio increases with the fcc or amorphous phase content and with decreasing degree of (0001)h texture. The magnetic measurements suggest that films that appeared amorphous according to their electron diffraction patterns are actually microcrystalline or at least partially crystallized.

  4. Magnetic properties of nickel halide hydrates including deuteration effects

    Science.gov (United States)

    DeFotis, G. C.; Van Dongen, M. J.; Hampton, A. S.; Komatsu, C. H.; Trowell, K. T.; Havas, K. C.; Davis, C. M.; DeSanto, C. L.; Hays, K.; Wagner, M. J.

    2017-01-01

    Magnetic measurements on variously hydrated nickel chlorides and bromides, including deuterated forms, are reported. Results include locations and sizes of susceptibility maxima, Tmax and χmax, ordering temperatures Tc, Curie constants and Weiss theta in the paramagnetic regime, and primary and secondary exchange interactions from analysis of low temperature data. For the latter a 2D Heisenberg model augmented by interlayer exchange in a mean-field approximation is applied. Magnetization data to 16 kG as a function of temperature show curvature and hysteresis characteristics quite system dependent. For four materials high field magnetization data to 70 kG at 2.00 K are also obtained. Comparison is made with theoretical relations for spin-1 models. Trends are apparent, primarily that Tmax of each bromide hydrate is less than for the corresponding chloride, and that for a given halide nD2O (n=1 or 2) deuterates exhibit lesser Tmax than do nH2O hydrates. A monoclinic unit cell determined from powder X-ray diffraction data on NiBr2·2D2O is different from and slightly larger than that of NiBr2·2H2O. This provides some rationale for the difference in magnetic properties between these.

  5. Study of magnetic properties of graphene nanostructures and graphene nanoribbons

    Directory of Open Access Journals (Sweden)

    F Fazileh

    2012-03-01

    Full Text Available The discovery of graphene and its remarkable electronic and magnetic properties has initiated great research interest in this material. Furthermore, there are many derivatives in these graphene related materials among which graphene nanoribbons and graphene nanofragments are candidates for future carbon-based nanoelectronics and spintronics. Theoretical studies have shown that magnetism can arise in various situations such as point defects, disorder and reduced dimensionality. Using a mean field Hubbard model, we studied the appearance of magnetic textures in zero-dimensional graphene nanofragments and one-dimensional graphene zigzag nanoribbons. Among nanofragments, triangular shape, bowtie and coronene were studied. We explain how the shape of these materials, the imbalance in the number of atoms belonging to the graphene sublattices, the existence of zero-energy states and the total and local magnetic moments were related. At the end, we focused on the effects of a model disorder potential (Anderson-type, and illustrate how density of states of zigzag nanoribbons was affected.

  6. Tailoring the magnetic properties of cobalt-ferrite nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Vega, A. Estrada de la; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

    2016-01-15

    In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

  7. Drug delivery property, bactericidal property and cytocompatibility of magnetic mesoporous bioactive glass.

    Science.gov (United States)

    Liu, Yi-Zhuo; Li, Yang; Yu, Xi-Bin; Liu, Li-Na; Zhu, Zhen-An; Guo, Ya-Ping

    2014-08-01

    A multifunctional magnetic mesoporous bioactive glass (MMBG) has been widely used for a drug delivery system, but its biological properties have been rarely reported. Herein, the effects of mesopores and Fe3O4 nanoparticles on drug loading-release property, bactericidal property and biocompatibility have been investigated by using mesoporous bioactive glass (MBG) and non-mesoporous bioactive glass (NBG) as control samples. Both MMBG and MBG have better drug loading efficiency than NBG because they possess ordered mesoporous channels, big specific surface areas and high pore volumes. As compared with MBG, the Fe3O4 nanoparticles in MMBG not only provide magnetic property, but also improve sustained drug release property. For gentamicin-loaded MMBG (Gent-MMBG), the sustained release of gentamicin and the Fe3O4 nanoparticles minimize bacterial adhesion significantly and prevent biofilm formation against Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). Moreover, the magnetic Fe3O4 nanoparticles in MMBG can promote crucial cell functions such as cell adhesion, spreading and proliferation. The excellent biocompatibility and drug delivery property of MMBG suggest that Gent-MMBG has great potentials for treatment of implant-associated infections.

  8. Evolution of the macroscopic properties of two epoxy resins during ageing under irradiation; Evolution des proprietes macroscopiques de deux resines epoxydes lors du vieillissement sous irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Vignoud, L

    2001-11-15

    In this study, the thermomechanical properties of two epoxy resins (DGEBA/TETA and DGEBA/DDM systems) are analysed as a function of the irradiation dose. The maximum conversion and reticulation is obtained by post-curing treatment. Irradiation by electrons results in a decrease of the glass transition temperature and of the elastic modulus in the rubbery region. These results can be interpreted invoking a destruction of the crosslinks and chains breaks within the resin. The Arrhenius diagrams obtained for the various doses shows that the cooperative mobility associated with the {alpha} relaxation becomes faster after the irradiation. On the contrary, more local mobility corresponding to the {gamma} relaxation is also modified, but in a lesser extent. The stress-strain curves are also discussed. In uniaxial compression test, the plastic flow stress {sigma}{sub p} decreases when the irradiation dose increases and this effect can largely be accounted for by a variation of T{sub g}. Post-irradiative effects are studied in inert atmosphere. Reticulation increases when the material is heated to a higher temperature than its T{sub g}. This effect suggest the presence of radical formed during irradiation. For DGEBA/TETA system, glass transition temperature T{sub g} shifts towards lowest temperatures. This shift increases the molecular mobility and enhances the physical ageing process at the ambient temperature. The results are well described by the quasi point defects theory. Direct effect of irradiation and physical ageing evolve with the scale parameter t{sub 0}. This parameter characterizes the gap (in time and/or temperature) between the principal relaxation and simplest ones. By connecting t{sub 0} to the amount of irradiation, it is possible to predict the modifications of the behaviour and to predict these evolutions for various amounts. (author)

  9. Structures and magnetic properties of Co-Zr-B magnets studied by first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin; Ke, Liqin; Nguyen, Manh Cuong; Wang, Cai-Zhuang, E-mail: wangcz@ameslab.gov; Ho, Kai-Ming, E-mail: kmh@ameslab.gov [Ames Laboratory, U.S. DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    2015-06-28

    The structures and magnetic properties of Co-Zr-B alloys near the composition of Co{sub 5}Zr with B at. % ≤6% were studied using adaptive genetic algorithm and first-principles calculations. The energy and magnetic moment contour maps as a function of chemical composition were constructed for the Co-Zr-B magnet alloys through extensive structure searches and calculations. We found that Co-Zr-B system exhibits the same structure motif as the “Co{sub 11}Zr{sub 2}” polymorphs, and such motif plays a key role in achieving strong magnetic anisotropy. Boron atoms were found to be able to substitute cobalt atoms or occupy the “interruption” sites. First-principles calculations showed that the magnetocrystalline anisotropy energies of the boron-doped alloys are close to that of the high-temperature rhombohedral Co{sub 5}Zr phase and larger than that of the low-temperature Co{sub 5.25}Zr phase. Our calculations provide useful guidelines for further experimental optimization of the magnetic performances of these alloys.

  10. FeGa/MgO/Fe/GaAs(001) magnetic tunnel junction: Growth and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Gobaut, B., E-mail: benoit.gobaut@elettra.eu [Sincrotrone Trieste S.C.p.A., S.S. 14-km 163.5, Area Science Park, 34012 Trieste (Italy); Ciprian, R.; Salles, B.R.; Krizmancic, D. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Rossi, G. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Dipartimento di Fisica, Università di Milano, via Celoria 16, 20133 Milano (Italy); Panaccione, G. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy); Eddrief, M.; Marangolo, M. [Sorbonne Universites, UPMC Univ Paris 06, UMR 7588, INSP, 4 place Jussieu, 75005 Paris (France); CNRS, UMR 7588, Institut des NanoSciences de Paris, 4 place Jussieu, 75005 Paris (France); Torelli, P. [Laboratorio TASC, IOM-CNR, S.S. 14-km 163.5, Basovizza, 34149 Trieste (Italy)

    2015-06-01

    Research on spintronics and on multiferroics leads now to the possibility of combining the properties of these materials in order to develop new functional devices. Here we report the integration of a layer of magnetostrictive material into a magnetic tunnel junction. A FeGa/MgO/Fe heterostructure has been grown on a GaAs(001) substrate by molecular beam epitaxy (MBE) and studied by X-ray magnetic circular dichroism (XMCD). The comparison between magneto optical Kerr effect (MOKE) measurements and hysteresis performed in total electron yield allowed distinguishing the ferromagnetic hysteresis loop of the FeGa top layer from that of the Fe buried layer, evidencing a different switching field of the two layers. This observation indicates an absence of magnetic coupling between the two ferromagnetic layers despite the thickness of the MgO barrier of only 2.5 nm. The in-plane magnetic anisotropy has also been investigated. Overall results show the good quality of the heterostructure and the general feasibility of such a device using magnetostrictive materials in magnetic tunnel junction.

  11. Magnetic bubbles and magnetic towers - I. General properties and simple analytical models

    Science.gov (United States)

    Aly, J.-J.; Amari, T.

    2012-02-01

    We consider magnetostatic equilibria in which a bounded region D containing a magnetized plasma is either fully confined by a field-free external medium - magnetic bubble equilibria (MBEqs) - or is confined by both such a medium and line-tying in a dense plasma region - magnetic tower equilibria (MTEqs). We first establish some of their general properties. In particular, we derive a series of useful integral equalities relating the magnetic field and the thermal pressures inside and outside D, respectively. We use them to prove the non-existence of an axisymmetric MBEq with a purely poloidal field, and to discuss some recent results of Braithwaite on MBEq formation by relaxation from an initial non-equilibrium state. We next present two families of exact analytical axisymmetric MBEqs with, respectively, spherical and toroidal shapes. The first family is extracted from Prendergast's model of a self-gravitating magnetized body, while the second one is constructed by using Palumbo's theory of isodynamic equilibria, for which both magnetic and thermal pressures take constant values on any flux surface. MTEqs with a large variety of structures are thus obtained in a simple way: we start from an arbitrary MBEq and just consider the part of it above a given plane cutting the bubble D. For MBEqs and MTEqs in either family, we compute in closed form most of the interesting physical quantities (such as energy, magnetic helicity and twist). Our results are expected to be useful for building up simple models of several astrophysical objects (such as X-ray cavities in the intracluster medium, jets emitted by disc accreting compact objects, eruptive events in stellar coronae and their ejecta).

  12. Electronic and Magnetic Properties of the p-NPNN

    Institute of Scientific and Technical Information of China (English)

    LUOShi-Jun; YAOKai-Lun

    2003-01-01

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

  13. Magnetic and sensitive magnetoelastic properties of Finemet nanostructured ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Pham Duc Thang [Faculty of Engineering Physics and Nanotechnology and Laboratory of Micro and Nanotechnology, College of Technology, Vietnam National University, 144 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Hoang Hai Duong; Nguyen Hoang Nghi [Laboratory of Amorphous and Nanocrystalline Materials, Hanoi University of Technology, 1 Dai Co Viet, Hanoi (Viet Nam)], E-mail: pdthang@vnu.edu.vn

    2009-09-01

    Soft-magnetic Fe{sub 73.5}Cu{sub 1}Nb{sub 3}Si{sub 13.5}B{sub 9} (Finemet) ribbon has been fabricated by using melt-spinning techniques. After annealing at suitable temperature the ribbon changes from an amorphous to crystalline state which related to the formation of Fe nanocrystallites. Study on the magnetic and magnetoelastic properties of the ribbon is presented. Furthermore, based on the fabricated ribbon stress sensors are simply constructed. The sensors showed high sensitivity of 3.8 mV/MPa as well as a wide working range up to 17 MPa. These sensors are potential for practical applications such as detecting small stress and movement in civil structures.

  14. Electronic and Magnetic Properties of the p-NPNN

    Institute of Scientific and Technical Information of China (English)

    LUO Shi-Jun; YAO Kai-Lun

    2003-01-01

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

  15. Geometry effect on the magnetic properties of manganese zinc ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Landgraf, F.J.G.; Lazaro-Colan, V. [Polytechnic School - EPUSP, Av.Prof. Luciano Gualberto 380, Sao Paulo 05508-900 (Brazil); Leicht, J. [Institute for Technological Research of Sao Paulo, Almeida Prado 532, Sao Paulo 05508-901 (Brazil)], E-mail: leichtj@ipt.br; Janasi, S.R. [Institute for Technological Research of Sao Paulo, Almeida Prado 532, Sao Paulo 05508-901 (Brazil); Lopes, M.F. [IMAG Industria e Comercio de Componentes Eletronicos Ltda, Embaixador 74, Ribeirao Pires 09410-650 (Brazil)

    2008-10-15

    The geometry effect on the bulk magnetic properties of MnZn ferrite toroidal cores produced by the ceramic method was investigated. The MnZn ferrite powder was pressed at two different toroidal sizes and sintered, under controlled atmosphere at different temperatures. The MnZn ferrites cores were characterized according to their magnetic losses, electrical resistivity, initial permeability and Curie temperature. The total loss (200 mT, 100 kHz) in the small cores S (aspect ratio (AR)=2.84) is lower compared with the total loss in the large cores L (AR=0.79). These results show an agreement with the geometry effect observed on electrical steels.

  16. Optimization of the magnetic properties of materials for fluxgate sensors

    Directory of Open Access Journals (Sweden)

    Luiz Carlos de Carvalho Benyosef

    2008-06-01

    Full Text Available A study was made of the variation of the magnetic properties of cobalt-based alloys using different compositions of CoFeSiB and CoFeSiBCr systems, which were produced by the melt-spinning technique and some of them subjected to a stress annealing treatment. A comparative study of core geometry and supporting material was also performed in order to obtain low noise fluxgate sensor core using amorphous magnetic ribbons of these alloys. The best alloy was a stress annealed Co67.5Fe3.5Si17.4B11.6 sample, which yielded fluxgate sensors with lower noise levels than those of commercial crystalline materials.

  17. Homogeneous Precipitation Synthesis and Magnetic Properties of Cobalt Ferrite Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zhigang Liu

    2008-01-01

    Full Text Available Magnetic nanoparticles (NPs of cobalt ferrite have been synthesized via a homogeneous precipitation route using hexamethylenetetramine (HMT as the precipitant. The particle size, crystal structure, and magnetic properties of the synthesized particles were investigated by X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer. The NPs are of cubic inverse spinel structure and nearly spherical shape. With the increase of oxidation time from 30 to 180 minutes in the reaction solution at 90∘C, the average particle size increases from ~30 nm to ~45 nm. The as-synthesized NPs ~30 nm in size show higher Ms (61.5 emu/g and moderate Hc (945 Oe and Mr/Ms (0.45 value compared with the materials synthesized by coprecipitation method using NaOH as precipitate at high pH value.

  18. Self-Assembled Magnetic Metallic Nanopillars in Ceramic Matrix with Anisotropic Magnetic and Electrical Transport Properties.

    Science.gov (United States)

    Su, Qing; Zhang, Wenrui; Lu, Ping; Fang, Shumin; Khatkhatay, Fauzia; Jian, Jie; Li, Leigang; Chen, Fanglin; Zhang, Xinghang; MacManus-Driscoll, Judith L; Chen, Aiping; Jia, Quanxi; Wang, Haiyan

    2016-08-10

    Ordered arrays of metallic nanopillars embedded in a ceramic matrix have recently attracted considerable interest for their multifunctionality in advanced devices. A number of hurdles need to be overcome for achieving practical devices, including selections of metal-ceramic combination, creation of tunable and ordered structure, and control of strain state. In this article, we demonstrate major advances to create such a fine nanoscale structure, i.e., epitaxial self-assembled vertically aligned metal-ceramic composite, in one-step growth using pulsed laser deposition. Tunable diameter and spacing of the nanopillars can be achieved by controlling the growth parameters such as deposition temperature. The magnetic metal-ceramic composite thin films demonstrate uniaxial anisotropic magnetic properties and enhanced coercivity compared to that of bulk metal. The system also presents unique anisotropic electrical transport properties under in-plane and out-of-plane directions. This work paves a new avenue to fabricate epitaxial metal-ceramic nanocomposites, which can simulate broader future explorations in nanocomposites with novel magnetic, optical, electrical, and catalytical properties.

  19. Magnetic properties and the effect of non-magnetic impurities in the quasi-2D quantum magnet

    Science.gov (United States)

    Khuntia, P.; Dey, T.; Mahajan, A. V.

    2016-09-01

    We present synthesis, x-ray diffraction, magnetisation and specific heat studies on the quasi-two-dimensional (2D) S = 1/2 antiferromagnet (CuCl)LaNb2O7 and its doping analogues (Cu1-x Zn x Cl)LaNb2O7 (0 ≤ x ≤ 0.05), (Cu0.95Mg0.05Cl)LaNb2O7, and (CuCl)La1-y Ba y Nb2O7 (0 ≤ y ≤ 0.10). The magnetic susceptibility and specific heat of the parent compound and its isovalent or hetereovalent counterparts do not display any signature of magnetic ordering down to 1.8 K. The parent compound and its doping variants exhibit spin-singlet behaviour with a finite gap in the spin excitation spectrum due to dimerisation of the dominant intradimer interactions as evidenced from our magnetic susceptibility and specific heat data. The systematic increase of magnetic susceptibility at low temperature with non-magnetic Zn2+ and Mg2+ (S = 0) substitution at the Cu2+ site reflect that impurities induce local moments around the non-magnetic sites. While heterovalent Ba2+ substitution at the La3+ site do not result in mobile holes but rather give rise to a Curie term in the susceptibility due to localisation. The low value of spin S = 1/2, and absence of long range ordering or spin freezing, and the presence of competing exchange interactions hold special significance in hosting novel magnetic properties in this class of quasi-2D quantum material.

  20. Copper nanoparticles functionalized PE: Preparation, characterization and magnetic properties

    Science.gov (United States)

    Reznickova, A.; Orendac, M.; Kolska, Z.; Cizmar, E.; Dendisova, M.; Svorcik, V.

    2016-12-01

    We report grafting of copper nanoparticles (CuNP) on plasma activated high density polyethylene (HDPE) via dithiol interlayer pointing out to the structural and magnetic properties of those composites. The as-synthesized Cu nanoparticles have been characterized by high-resolution transmission electron microscopy (HRTEM/TEM) and UV-vis spectroscopy. Properties of pristine PE and their plasma treated counterparts were studied by different experimental techniques: X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, energy dispersive X-ray spectroscopy (EDS), zeta potential, electron spin resonance (ESR) and SQUID magnetometry. From TEM and HRTEM analyses, it is found that the size of high purity Cu nanoparticles is (12.2 ± 5.2) nm. It was determined that in the CuNPs, the copper atoms are arranged mostly in the (111) and (200) planes. Absorption in UV-vis region by these nanoparticles is ranging from 570 to 670 nm. EDS revealed that after 1 h of grafting are Cu nanoparticles homogeneously distributed over the whole surface and after 24 h of grafting Cu nanoparticles tend to aggregate slightly. The combined investigation of magnetic properties using ESR spectrometry and SQUID magnetometry confirmed the presence of copper nanoparticles anchored on PE substrate and indicated ferromagnetic interactions.

  1. Anisotropic Thermal Properties of Nanostructured Magnetic, Carbon and Hybrid Magnetic - Carbon Materials

    Science.gov (United States)

    Ramirez, Sylvester

    In this dissertation research we investigated thermal properties of three groups of nanostructured materials: (i) magnetic; (ii) reduced graphene oxide films; and (iii) hybrid magnetic -- graphite -- graphene composites. The thermal measurements were conducted using the transient "hot disk" and "laser flash" techniques. The rare-earth free nanostructured SrFe12O19 permanent magnets were produced by the current activated pressure assisted densification technique. The thermal conductivity of the nanostructured bulk magnets was found to range from 3.8 to 5.6 W/mK for the in-plane and 2.36 W/mk to 2.65 W/mK for the cross-plane directions, respectively. The heat conduction was dominated by phonons near the room temperature. The anisotropy of heat conduction was explained by the brick-like alignment of crystalline grains with the longer grain size in-plane direction. The thermal conductivity scales up with the average grain size and mass density of the material revealing weak temperature dependence. Using the nanostructured ferromagnetic Fe3O4 composites as an example system, we incorporated graphene and graphite fillers into magnetic material without changing their morphology. It was demonstrated that addition of 5 wt. % of equal mixture of graphene and graphite flakes to the composite results in a factor of x2.6 enhancement of the thermal conductivity without significant degradation of the saturation magnetization. We investigated thermal conductivity of free-standing reduced graphene oxide films subjected to a high-temperature treatment of up to 1000°C. It was found that the high-temperature annealing dramatically increased the in-plane thermal conductivity, K, of the films from ˜3 W/mK to ˜61 W/mK at room temperature. The cross-plane thermal conductivity, K⊥, revealed an interesting opposite trend of decreasing to a very small value of ˜0.09 W/mK in the reduced graphene oxide films annealed at 1000°C. The obtained films demonstrated an exceptionally strong

  2. Particle Size-Specific Magnetic Measurements as a Tool for Enhancing Our Understanding of the Bulk Magnetic Properties of Sediments

    Directory of Open Access Journals (Sweden)

    Robert G. Hatfield

    2014-10-01

    Full Text Available Bulk magnetic properties of soils and sediments are often sensitive proxies for environmental change but commonly require interpretation in terms of the different sources of magnetic minerals (or components that combine to generate them. Discrimination of different components in the bulk magnetic record is often attempted through endmember unmixing and/or high resolution measurements that can require intensive measurement plans, assume linear additivity, and sometimes have difficulty in discriminating a large number of sources. As an alternative, magnetic measurements can be made on isolated sediment fractions that constitute the bulk sample. When these types of measurements are taken, heterogeneity is frequently observed between the magnetic properties of different fractions, suggesting different magnetic components often associate with different physical grain sizes. Using a particle size-specific methodology, individual components can be isolated and studied and bulk magnetic properties can be linked to, and isolated from, sedimentological variations. Deconvolving sedimentary and magnetic variability in this way has strong potential for increased understanding of how magnetic fragments are carried in natural systems, how they vary with different source(s, and allows for a better assessment of the effect environmental variability has in driving bulk magnetic properties. However, despite these benefits, very few studies exploit the information they can provide. Here, I present an overview of the different sources of magnetic minerals, why they might associate with different sediment fractions, how bulk magnetic measurements have been used to understand the contribution of different components to the bulk magnetic record, and outline how particle size-specific magnetic measurements can assist in their better understanding. Advantages and disadvantages of this methodology, their role alongside bulk magnetic measurements, and potential future

  3. Structural and magnetic properties of nanocrystalline stannic substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Abbas, Y.M., E-mail: ymabbas@live.com [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Mansour, S.A. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University, Rabegh (Saudi Arabia); Ibrahim, M.H. [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt); Physics Department, Faculty of Science, King AbdulAziz University (Saudi Arabia); Ali, Shehab. E., E-mail: shehab_ali@science.suez.edu.eg [Physics Department, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-09-15

    The structural and magnetic properties of the spinel ferrite system Co{sub 1+x}Fe{sub 2-2x}Sn{sub x}O{sub 4} (x=0.0-1.0) have been studied. Samples in the series were prepared by the ceramic technique. The structural and microstructural evolutions of the nanophase have been studied using X-ray powder diffraction and the Rietveld method. The refinement result showed that the type of the cationic distribution over the tetrahedral and octahedral sites in the nanocrystalline lattice is partially an inverse spinel. Far infrared absorption spectra show two significant absorption bands, around 600 cm{sup -1} and 425 cm{sup -1}, which are respectively attributed to tetrahedral (A) and octahedral [B] vibrations of the spinel. Scanning Electron Microscopy (SEM) was used to study surface morphology. SEM images reveal particles in the nanosize range. The transmission electronic microscope (TEM) reveals that the grains are spherical in shape. TEM analysis confirmed the X-ray results. The magnetic properties of the prepared samples were characterized by using a vibrating sample magnetometer. - Highlights: Black-Right-Pointing-Pointer The spinel ferrite system has been formed at 1000 Degree-Sign C by using ceramic techniques. Black-Right-Pointing-Pointer Structural and microstructural evolutions have been studied using XRD and the Rietveld method. Black-Right-Pointing-Pointer The refinement result showed cationic distribution in the lattice is partially an inverse spinel. Black-Right-Pointing-Pointer The transmission electronic microscope analysis confirmed the X-ray results. Black-Right-Pointing-Pointer Magnetic properties of the samples were characterized by using a vibrating sample magnetometer.

  4. Theoretical investigation of magnetic and optical properties of semiconductor nanocrystals

    Science.gov (United States)

    Proshchenko, Vitaly

    This thesis presents the theoretical investigation of physical properties of pure and transition metal doped semiconductor nanostructures. First we study optical and energy (the density of states) spectra for Cd mSem clusters of various sizes and shapes, such as spheres, cubes, nanorods, and nanotubes. This work requires a careful computational analysis where a proper exchange-correlation functional has to be chosen to fit the experimental data. The next part of the thesis deals with the magnetic properties of manganese doped CdSe, ZnSe, ZnS, and CdS quantum dots (QDs). We theoretically explain the effect of dual luminescence and show that in the case with CdSe quantum dots the luminescence becomes tunable by a QD size. We also study the concentration dependence of magnetic order and optical transitions in Mn doped CdSe nanocrystals. Room temperature d0 ferromagnetism is studied in ZnS quantum dots and nanowires in Chapter 4. To find the magnetization of the medium and large size nanocrystals we introduce the surface-bulk (SB) model. We show that the condensation of Zn vacancies into a single droplet takes place which leads to the week d0 ferromagnetism in ZnS nanocrystals. In the last Chapter we study electronic, optical, and charge transport properties of two new holey 2D materials, ELH-g-C2N-H and ELH-g-C2N-Br with hydrogen and bromine side-groups, respectively. Since the two 2D crystals under study have not been synthesized yet, we provide the stability analysis and prove that the calculated crystal structures correspond to the global energy minimum criterion.

  5. Macroscopic quantum oscillator based on a flux qubit

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mandip, E-mail: mandip@iisermohali.ac.in

    2015-09-25

    In this paper a macroscopic quantum oscillator is proposed, which consists of a flux-qubit in the form of a cantilever. The net magnetic flux threading through the flux-qubit and the mechanical degrees of freedom of the cantilever are naturally coupled. The coupling between the cantilever and the magnetic flux is controlled through an external magnetic field. The ground state of the flux-qubit-cantilever turns out to be an entangled quantum state, where the cantilever deflection and the magnetic flux are the entangled degrees of freedom. A variant, which is a special case of the flux-qubit-cantilever without a Josephson junction, is also discussed. - Highlights: • In this paper a flux-qubit-cantilever is proposed. • Coupling can be varied by an external magnetic field. • Ground state is a macroscopic entangled quantum state. • Ground state of the superconducting-loop-oscillator is a macroscopic quantum superposition. • Proposed scheme is based on a generalized quantum approach.

  6. Tailoring magnetic and dielectric properties of rubber ferrite composites containing mixed ferrites

    Indian Academy of Sciences (India)

    M R Anantharaman; K A Malini; S Sindhu; E M Mohammed; S K Date; S D Kulkarni; P A Joy; Philip Kurian

    2001-12-01

    Rubber ferrite composites containing various mixed ferrites were prepared for different compositions and various loadings. The magnetic and dielectric properties of the fillers as well as the ferrite filled matrixes were evaluated separately. The results are correlated. Simple equations are proposed to predetermine the magnetic and dielectric properties. The validity of these equations is verified and they are found to be in good agreement. These equations are useful in tailoring the magnetic and dielectric properties of these composites with predetermined properties.

  7. The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with single-ion anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Gangsan; Zhu, Rengui, E-mail: rgzhu@mail.ahnu.edu.cn

    2015-02-15

    The magnetic properties of the spin-1 Heisenberg antiferromagnetic chain with exchange anisotropy and single-ion anisotropy are studied by the double-time Green's function method. The determinative equations for the critical temperature, the magnetization, and the zero-field susceptibility are derived analytically. The effects of the anisotropies on the magnetic properties are presented.

  8. Measurement system of alternating magnetic properties under DC-biased field

    CERN Document Server

    Enokizono, M

    2000-01-01

    This paper presents magnetic properties under DC-biased magnetization of a grain-oriented silicon steel sheet 30Z. We have practised the measurement of DC-biased flux density by using flux meter directly. The DC-biased magnetic properties have been made clear in this experimental approach.

  9. Magnetic properties of UN studied by [mu]SR

    Energy Technology Data Exchange (ETDEWEB)

    Muench, K.H. (Technische Univ. Muenchen, Garching (Germany)); Kratzer, A. (Technische Univ. Muenchen, Garching (Germany)); Kalvius, G.M. (Technische Univ. Muenchen, Garching (Germany)); Asch, L. (Technische Univ. Muenchen, Garching (Germany)); Litterst, F.J. (Technische Univ. Braunschweig (Germany)); Richter, K. (European Transuranium Inst., Karlsruhe (Germany))

    1993-11-01

    In the paramagnetic range (T>T[sub N] = 53 K) fluctuations of the moments on uranium are too fast to produce a sizeable damping of the [mu]SR signal even close to T[sub N]. This rules out the formation of a magnetic precursor state as seen in UAs. In the antiferromagnetic regime all contributions to the field at the muon site cancel due to symmetry. Comparison with analogous data on other uranium mono-pnictides show that the magnitude of the field distribution width in the type I-single k antiferromagnetic state is not an intrinsic property of these materials. (orig.)

  10. Low-Temperature Magnetic Properties of Co Antidot Array

    Institute of Scientific and Technical Information of China (English)

    LIU Qing-Fang; JIANG Chang-Jun; FAN Xiao-Long; WANG Jian-Bo; XUE De-Sheng

    2006-01-01

    Cobalt antidot arrays with different thicknesses are fabricated by rf magnetron sputtering onto porous alumina substrates. Scanning electron microscopy and grazing incidence x-ray diffraction are employed to characterize the morphology and crystal structure of the antidot array, respectively. The temperature dependence of magnetic properties shows that in the temperature range 5K-300K, coercivity and squareness increase firstly, reach their maximum values, then decrease. The anomalous temperature dependences of coercivity and squareness are discussed by considering the pinning effect of the antidot and the magnetocrystalline anisotropy.

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

    Institute of Scientific and Technical Information of China (English)

    M.Nakamura; Y.Ohgo; A.Ikezaki

    2007-01-01

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

  12. Investigation of magnetic sensor properties of magnetic tunnel junctions with superparamagnetic free layer at low frequencies for biomedical imaging applications

    Science.gov (United States)

    Ishikawa, Kyohei; Oogane, Mikihiko; Fujiwara, Kousuke; Jono, Junichi; Tsuchida, Masaaki; Ando, Yasuo

    2016-12-01

    The magnetic sensor properties of magnetic tunnel junctions (MTJs) with a superparamagnetic (SP) free layer were systematically investigated at low frequencies (<10 Hz). We prepared four varieties of MTJs with various SP properties by changing the annealing temperature. The temperature dependence of magnetoresistance curves and the signal/noise property at 285 K were evaluated. We found that the SP free layer has the advantage of detecting very small and low-frequency AC magnetic fields compared with a ferromagnetic free layer. The SP free layer strongly suppressed magnetic 1/f noise at low frequencies and expressed a very linear response to a small magnetic field. The obtained properties in MTJs with the SP free layer are suitable for detecting biomagnetic fields. The detectivity was 111 nT at low frequencies (from 0.1 to 10 Hz), which is one of the highest values in single-MTJ sensors.

  13. Growth and magnetic properties dependence of the Co–Cu/Cu films electrodeposited under high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Franczak, Agnieszka, E-mail: agnieszka.franczak@mtm.kuleuven.be [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Department of Materials Science (MTM), KU Leuven, Kasteelpark Arenberg 44, 3001 Haverlee (Leuven) (Belgium); Levesque, Alexandra [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); Zabinski, Piotr [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Li, Donggang [Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, 314 Box, 110004 Shenyang (China); Czapkiewicz, Maciej [Department of Electronics, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Kowalik, Remigiusz [Laboratory of Physical Chemistry and Electrochemistry, Faculty of Non-Ferrous Metals, AGH University of Science and Technology, al. A. Mickiewicza 30, 30059 Krakow (Poland); Bohr, Frédéric [Laboratoire d’Ingénierie et Sciences des Matériaux (LISM EA 4695), Université de Reims Champagne-Ardenne, UFR Sciences et Naturelles, Bat. 6, Moulin de la Housse, BP 1039, 51687 Reims Cedex 2 (France); and others

    2015-07-15

    The present work is focused on the investigations of magnetic properties dependence on microstructure of Co–Cu/Cu films electrodeposited under superimposed high magnetic field. The experimental results indicate a strong effect of an external magnetic field on the morphology of deposited films, more precisely on the Co:Cu ratio that determines the film growth. It is shown that the Co–Cu/Cu films electrodeposited without superimposed magnetic field consisted of two clearly visible features: compact film with incorporated granular particles. Under a superimposed external high magnetic field the privilege growth of the particles was induced. As a consequence, development of the well-defined branched structure of Co–Cu/Cu film was observed. In contrary, the phase compositional investigations do not reveal any changes in the phase formation during electrodeposition under magnetic field conditions. Thus, it is assumed that a strong growth of Co–Cu/Cu films in (111) direction under magnetic or non-magnetic electrodeposition conditions is related with the growth of Cu (111) plane and embedded into it some of the Co fcc atoms of same (111) orientation, as well as the Co hcp atoms that grows in the (002) direction. This non-equilibrium growth of Co–Cu/Cu films under magnetic deposition conditions affects strongly the magnetic properties of deposited films, revealing that films obtained under magnetic fields higher than 3 T were no more magnetic materials. - Highlights: • Co–Cu/Cu electrodeposits were obtained at elevated temperature under HMFs. • The effects of HMFs on microstructure and magnetic properties were investigated. • Interesting morphological changes due to HMFs has been observed. • Changes in Co:Cu ratio due to HMFs modified the magnetic properties of deposits.

  14. Magnetic properties of nanocrystalline Fe-Cu-Si-B alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizawa, Y; Ohta, M, E-mail: yoshihito_yoshizawa@hitachi-metals.co.j [Advanced Electronics Research Laboratory, Hitachi Metals, Ltd., 5200 Mikajiri, Kumagaya, Saitama 360-0843 (Japan)

    2009-01-01

    Recently, nanocrystalline Fe-Cu-B and Fe-Cu-Si-B soft magnetic alloys with high saturation magnetic flux density more than 1.8 T and low coercivity of about 6 A m{sup -1} were developed by annealing melt-quenched alloys containing 1.3 -1.5 at % Cu and 0 - 7 at % Si. In this work, the magnetic properties of annealed Fe{sub 77.5-x}Cu{sub x}Si{sub 15.5}B{sub 7} alloys with high Si content prepared by melt spinning are reported. The appropriate Cu content in this alloy system shifted to Cu content higher than that of the reported Fe-Cu-Si-B alloys with high B{sub s}. The annealed alloy with x = 2.0 showed the H{sub c} of about 10 A m{sup -1}, the B{sub 8000} of 1.47 T, and low magnetostriction of +4.8 x 10{sup -6}.

  15. Properties of the Ising magnet confined in a corner geometry

    Science.gov (United States)

    Albano, Ezequiel V.; de Virgiliis, Andres; Müller, Marcus; Binder, Kurt

    2007-10-01

    The properties of Ising square lattices with nearest neighbor ferromagnetic exchange confined in a corner geometry, are studied by means of Monte Carlo simulations. Free boundary conditions at which boundary magnetic fields ±h are applied, i.e., at the two boundary rows ending at the lower left corner a field +h acts, while at the two boundary rows ending at the upper right corner a field -h acts. For temperatures T less than the critical temperature T of the bulk, this boundary condition leads to the formation of two domains with opposite orientation of the magnetization direction, separated by an interface which for T larger than the filling transition temperature T(h) runs from the upper left corner to the lower right corner, while for Tinterface is localized either close to the lower left corner or close to the upper right corner. It is shown that for T=T(h) the magnetization profile m(z) in the z-direction normal to the interface simply is linear and the interfacial width scales as w∝L, while for T>T(h) it scales as w∝√{L}. The distribution P(ℓ) of the interface position ℓ (measured along the z-direction from the corners) decays exponentially for TT(h). Unlike the findings for critical wetting in the thin film geometry of the Ising model, the Monte Carlo results for corner wetting are in very good agreement with the theoretical predictions.

  16. Distribution of Helical Properties of Solar Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    Kirill M. Kuzanyan; Victor G. Lamburt; Hong-Qi Zhang; Shu-Dong Bao

    2003-01-01

    We summarize studies of helical properties of solar magnetic fieldssuch as current helicity and twist of magnetic fields in solar active regions (ARs),that are observational tracers of the alpha-effect in the solar convective zone (SCZ).Information on their spatial distribution is obtained by analysis of systematic mag-netographic observations of active regions taken at Huairou Solar Observing Stationof National Astronomical Observatories of Chinese Academy of Sciences. The mainproperty is that the tracers of the alpha-effect are antisymmetric about the solarequator. Identifying longitudinal migration of active regions with their individualrotation rates and taking into account the internal differential rotation law withinthe SCZ known from helioseismology, we deduce the distribution of the effect overdepth. We have found evidence that the alpha-effect changes its value and signnear the bottom of the SCZ, and this is in accord with the theoretical studies andnumerical simulations. We discuss other regularities which can be revealed by fur-ther analysis such as possible dependence on longitude, time, and magnetic fieldstrength, etc.

  17. Crystallographic phases and magnetic properties of iron nitride films

    Energy Technology Data Exchange (ETDEWEB)

    Li, Guo-Ke [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Liu, Yan; Zhao, Rui-Bin [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Shen, Jun-Jie [Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043 (China); Wang, Shang; Shan, Pu-Jia; Zhen, Cong-Mian [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China); Hou, Deng-Lu, E-mail: houdenglu@mail.hebtu.edu.cn [Department of Physics, Hebei Advanced Thin Films Laboratory, Hebei Normal University, Shijiazhuang 050024 (China)

    2015-08-31

    Iron nitride films, including single phase films of α-FeN (expanded bcc Fe), γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N (0 ≤ x ≤ 1), and γ″-FeN, were sputtered onto AlN buffered glass substrates. It was found possible to control the phases in the films merely by changing the nitrogen partial pressure during deposition. The magnetization decreased with increased nitrogen concentration and dropped to zero when the N:Fe ratio was above 0.5. The experimental results, along with spin polarized band calculations, have been used to discuss and analyze the magnetic properties of iron nitrides. It has been demonstrated that in addition to influencing the lattice constant of the various iron nitrides, the nearest N atoms have a significant influence on the exchange splitting of the Fe atoms. Due to the hybridization of Fe-3d and N-2p states, the magnetic moment of Fe atoms decreases with an increase in the number of nearest neighbor nitrogen atoms. - Highlights: • Single phase γ′-Fe{sub 4}N, ε-Fe{sub 3−x}N, and γ″-FeN films were obtained using dc sputtering. • The phases in iron nitride films can be controlled by the nitrogen partial pressure. • The nearest N neighbors have a significant influence on the exchange splitting of Fe.

  18. Avian magnetic compass: Its functional properties and physical basis

    Directory of Open Access Journals (Sweden)

    Roswitha WILTSCHKO, Wolfgang WILTSCHKO

    2010-06-01

    Full Text Available The avian magnetic compass was analyzed in bird species of three different orders – Passeriforms, Columbiforms and Galliforms – and in three different behavioral contexts, namely migratory orientation, homing and directional conditioning. The respective findings indicate similar functional properties: it is an inclination compass that works only within a functional window around the ambient magnetic field intensity; it tends to be lateralized in favor of the right eye, and it is wavelength-dependent, requiring light from the short-wavelength range of the spectrum. The underlying physical mechanisms have been identified as radical pair processes, spin-chemical reactions in specialized photopigments. The iron-based receptors in the upper beak do not seem to be involved. The existence of the same type of magnetic compass in only very distantly related bird species suggests that it may have been present already in the common ancestors of all modern birds, where it evolved as an all-purpose compass mechanism for orientation within the home range [Current Zoology 56 (3: 265–276, 2010].

  19. Magnetic nanoparticles with dual functional properties: drug delivery and magnetic resonance imaging.

    Science.gov (United States)

    Jain, Tapan K; Richey, John; Strand, Michelle; Leslie-Pelecky, Diandra L; Flask, Chris A; Labhasetwar, Vinod

    2008-10-01

    There is significant interest in recent years in developing magnetic nanoparticles (MNPs) having multifunctional characteristics with complimentary roles. In this study, we investigated the drug delivery and magnetic resonance imaging (MRI) properties of our novel oleic acid-coated iron-oxide and pluronic-stabilized MNPs. The drug incorporation efficiency of doxorubicin and paclitaxel (alone or in combination) in MNPs was 74-95%; the drug release was sustained and the incorporated drugs had marginal effects on physical (size and zeta potential) and magnetization properties of the MNPs. The drugs in combination incorporated in MNPs demonstrated highly synergistic antiproliferative activity in MCF-7 breast cancer cells. The T2 relaxivity (r(2)) was higher for our MNPs than Feridex IV, whereas the T1 relaxivity (r(1)) was better for Feridex IV than for our MNPs, suggesting greater sensitivity of our MNPs than Feridex IV in T2 weighted imaging. The circulation half-life (t(1/2)), determined from the changes in the MRI signal intensity in carotid arteries in mice, was longer for our MNPs than Feridex IV (t(1/2)=31.2 vs. 6.4 min). MNPs with combined characteristics of MRI and drug delivery could be of high clinical significance in the treatment of various disease conditions.

  20. Enhanced dielectric and magnetic properties of polystyrene added CoFe2O4 magnetic nanoparticles

    Science.gov (United States)

    Vadivel, M.; Babu, R. Ramesh; Ramamurthi, K.; Arivanandhan, M.

    2017-03-01

    In this work, a facile chemical synthesis of polystyrene (PS) added cobalt ferrite (CoFe2O4) magnetic nanoparticles by co-precipitation method is reported and the role of PS concentrations (1, 2, 3, 4 and 5 wt%) on the structural, morphological, dielectric and magnetic properties of CoFe2O4 nanoparticles is investigated. Formation of single phase cubic inverse spinel structure is confirmed by X-ray diffraction and Raman spectral analyses. Transmission electron microscopy studies show that the size of CoFe2O4 nanoparticles can be controlled by varying of PS concentration. Dielectric constant is enhanced due to increase in the PS concentrations in CoFe2O4 nanoparticles. Vibrating sample magnetometer measurements elucidate the enhanced saturation magnetization, coercivity and remanent magnetization in 1, 2 and 3 wt% of PS added CoFe2O4 nanoparticles. Hence the results obtained in this work evidently show that the addition of PS as a surfactant in the synthesis of CoFe2O4 nanoparticles remarkably modify the size of the particles.

  1. Magnetic properties and magnetic domain structure of grain-oriented Fe-3%Si steel under compression

    Science.gov (United States)

    Perevertov, O.; Schäfer, R.

    2016-09-01

    The influence of an applied compressive stress on the magnetic properties and domain structure in Goss-textured (110) [001] Fe-3%Si steel is studied. The magnetic domains and magnetization processes were observed by longitudinal Kerr microscopy at different levels of compressive stress. With stress increase the domain structure without applied field evolves from 180° slab-like domains along the surface-parallel easy axis first into stress pattern I, then into the checkerboard pattern and finally into stress pattern II, in which all internal domains are oriented along the transverse axes. The magnetization process under compression is realized by surface closure [001] domains that grow into the bulk at the expense of transverse domains. The domain evolution by these three stress patterns is not practically noticeable in hysteresis curves above 10 MPa—they change continuously with the same effective field being valid for curves from 10 to 67 MPa. The comparison with previous measurements under different stress/cutting angle combinations shows that for the prediction of a constricted hysteresis loop it is sufficient to consider the energy difference between surface-parallel and transverse easy axes neglecting details of the spatial organization of transverse domains.

  2. Optimizing Magnetocaloric Properties of Heusler-Type Magnetic Shape Memory Alloys by Tuning Magnetostructural Transformation Parameters

    Science.gov (United States)

    Huang, Lian; Qu, Yuhai; Cong, Daoyong; Sun, Xiaoming; Wang, Yandong

    2017-08-01

    Heusler-type magnetic shape memory alloys show a magnetostructural transformation from the low-magnetization phase to the high-magnetization phase upon the application of external magnetic fields. As a result, these alloys exhibit fascinating multifunctional properties, such as magnetic shape memory effect, magnetocaloric effect, magnetoresistance, and magnetic superelasticity. All these functional properties are intimately related to the coupling of the structural and magnetic transitions. Therefore, deliberate tuning of the magnetostructural transformation parameters is essential for obtaining optimal multifunctional properties. Here, we show that by tuning the magnetostructural transformation parameters, we are able to achieve a variety of novel magnetocaloric properties with different application potentials: (1) large magnetic entropy change of 31.9 J kg-1 K-1 under a magnetic field of 5 T; (2) giant effective magnetic refrigeration capacity (251 J kg-1) with a broad operating temperature window (33 K) under a magnetic field of 5 T; (3) large reversible field-induced entropy change (about 15 J kg-1 K-1) and large reversible effective magnetic refrigeration capacity (77 J kg-1) under a magnetic field of 5 T. The balanced tuning of magnetostructural transformation parameters of magnetic shape memory alloys may provide an instructive reference to the shape memory and magnetic refrigeration communities.

  3. Switching Properties of sub-100 nm Perpendicular Magnetic Tunnel Junctions

    Science.gov (United States)

    Tryputen, Larysa; Piotrowski, Stephan; Bapna, Mukund; Chien, Chia-Ling; Wang, Weigang; Majetich, Sara; Ross, Caroline

    2015-03-01

    Perpendicular magnetic tunnel junctions (p-MTJs) have great potential for realizing high-density non-volatile memory and logic devices. It is critical to solve scalability problem to implement such devices, to achieve low resistance area and to reduce switching current density while maintaining thermal stability. We present our recent results on fabrication of high resolution Ta/CoFeB/MgO/CoFeB/Ta p-MTJ devices and characterization of their switching properties as well as topography and current mapping by using nanoscale Conductive Atomic Force Microscopy. Our patterning method is based on using hydrogen silsesquioxane resist mask combined with ion beam etching. It allows to fabricate p-MTJ devices down to 40 nm in diameter while maintaining the magnetic quality of the multilayers. Repeatable, consistent switching behaviour has been observed in the obtained p-MTJ devices of 500 nm down to 40 nm with 10 - 800 mV voltage applied. Switching field increased as device diameter decreased, from 580 Oe at 500 nm (MR = 10%) to 410 Oe at 80 nm (MR = 9%). We discuss the effect of device sizes on the switching properties. This work was supported in part by C-SPIN, one of the six centers of STARnet, a Semiconductor Research Corporation Program sponsored by MARCO and DARPA and in part through the National Science Foundation through NCN-Needs Program, Contract 12207020-EEC.

  4. Thermal and magnetic properties of chitosan-iron oxide nanoparticles.

    Science.gov (United States)

    Soares, Paula I P; Machado, Diana; Laia, César; Pereira, Laura C J; Coutinho, Joana T; Ferreira, Isabel M M; Novo, Carlos M M; Borges, João Paulo

    2016-09-20

    Chitosan is a biopolymer widely used for biomedical applications such as drug delivery systems, wound healing, and tissue engineering. Chitosan can be used as coating for other types of materials such as iron oxide nanoparticles, improving its biocompatibility while extending its range of applications. In this work iron oxide nanoparticles (Fe3O4 NPs) produced by chemical precipitation and thermal decomposition and coated with chitosan with different molecular weights were studied. Basic characterization on bare and chitosan-Fe3O4 NPs was performed demonstrating that chitosan does not affect the crystallinity, chemical composition, and superparamagnetic properties of the Fe3O4 NPs, and also the incorporation of Fe3O4 NPs into chitosan nanoparticles increases the later hydrodynamic diameter without compromising its physical and chemical properties. The nano-composite was tested for magnetic hyperthermia by applying an alternating current magnetic field to the samples demonstrating that the heating ability of the Fe3O4 NPs was not significantly affected by chitosan.

  5. Correlation of Crystalline Structure with Magnetic and Transport Properties of Glass-Coated Microwires

    Directory of Open Access Journals (Sweden)

    Arcady Zhukov

    2017-02-01

    Full Text Available We overviewed the correlation between the structure, magnetic and transport properties of magnetic microwires prepared by the Taylor-Ulitovsky method involving rapid quenching from the melt and drawing of the composite (metallic core, glass coated wire. We showed that this method can be useful for the preparation of different families of magnetic microwires: soft magnetic microwires displaying Giant magnetoimpedance (GMI effect, semi-hard magnetic microwires, microwires with granular structure exhibiting Giant Magnetoresistance (GMR effect and Heusler-type microwires. Magnetic and transport properties of magnetic microwires depend on the chemical composition of metallic nucleus and on the structural features (grain size, precipitating phases of prepared microwires. In all families of crystalline microwires, their structure, magnetic and transport properties are affected by internal stresses induced by the glass coating, depending on the quenching rate. Therefore, properties of glass-coated microwires are considerably different from conventional bulk crystalline alloys.

  6. Magnetic and structural properties of ferrihydrite/hematite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Pariona, N.; Camacho-Aguilar, K.I.; Ramos-González, R. [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav-Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Coahuila 25900 (Mexico); Martinez, Arturo I., E-mail: mtz.art@gmail.com [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav-Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Coahuila 25900 (Mexico); Herrera-Trejo, M. [Center for Research and Advanced Studies of the National Polytechnic Institute, Cinvestav-Saltillo, Av. Industria Metalúrgica 1062, Parque Industrial Ramos Arizpe, Coahuila 25900 (Mexico); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Río de Janeiro 22290-180 (Brazil)

    2016-05-15

    A rich variety of ferrihydrite/hematite nanocomposites (NCs) with specific size, composition and properties were obtained in transformation reactions of 2-line ferrihydrite. Transmission electron microscopy (TEM) observations showed that the NCs consist of clusters of strongly aggregated nanoparticles (NPs) similarly to a “plum pudding”, where hematite NPs “raisins” are surrounded by ferrihydrite “pudding”. Magnetic measurements of the NCs correlate very well with TEM results; i.e., higher coercive fields correspond to greater hematite crystallite size. First order reversal curve (FORC) measurements were used for the characterization of the magnetic components of the NCs. FORC diagrams revealed that the NCs prepared at short times are composed by single domains with low coercivity, and NCs prepared at times larger than 60 min exhibited elongated distribution along the Hc axis. It suggested that these samples consist of mixtures of different kinds of hematite particles, ones with low coercivity and others with coercivity greater than 600 Oe. For NCs prepared at times larger than 60 min, Mossbauer spectroscopy revealed the presence of two sextets, which one was assigned to fine hematite particles and other to hematite particles with hyperfine parameters near to bulk hematite. The correlation of the structural and magnetic properties of the ferrihydrite/hematite NCs revealed important characteristics of these materials which have not been reported elsewhere. - Highlights: • Ferrihydrite/hematite nanocomposites were prepared. • The “plum pudding” morphology of the ferrihydrite/hematite nanocomposites was found. • The FORC diagrams of ferrihydrite/hematite nanocomposites have been measured.

  7. Magnetic properties of Pr ions in perovskite-type oxides

    Science.gov (United States)

    Sekizawa, K.; Kitagawa, M.; Takano, Y.

    1998-01-01

    Magnetic properties of Pr ions with the controlled valence on the A and B sites of perovskite-type oxides (ABO 3) were investigated for two systems, PrSc 1 - xMg xO 3 and BaPr 1 - xBi xO 3. From the magnetic susceptibility χ versus temperature T curves of PrSc 1 - xMg xO 3, the χ-T curve for molar Pr 3+ ions on the A site and that of Pr 4+ ions were obtained. The 1/χ-T curves for both ions exhibit the crystalline electric field (CEF) effect and the effective magnetic moment μ eff above 100 K is 3.41 μ B for Pr 3+ and 2.58 μ B for Pr 4+, respectively. The χ-T curve of PrSc 0.8Mg 0.2O 3 is similar to that of PrBa 2Cu 3O y. In the BaPr 1 - xBi xO 3 system, only one intermediate phase BaPr 0.5Bi 0.5O 3 exists, in which Pr and Bi take an ordered arrangement on the B site. The magnetic susceptibility χ for Pr 4+ and that of Pr 3- in the ordered arrangement with Bi 5+ on the B site are much smaller than those for the A site, reflecting the strong CEF effect on the B site. Experimental χ-T curves can be well reproduced by the numerical calculation for Pr 3+ or Pr 4+ ions in the molecular field and the CEF with proper respective parameters.

  8. Magnetic Properties and Residual Stress of electroplated Ni

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Joo; Park, Keun Yung; Uhm, Young Rang; Son, Kwang Jae [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    The charged Ni-63 ions are formed by dissolving metal Ni-63. To establish the coating conditions for Ni-63, non-radioactive metal Ni particles are dissolved in an acid solution and electroplated onto a Ni sheet. A continuous increase in the particle size versus the current density has also been recognized in the DC electrodeposition of nickel coating. The Ni metal is magnetic materials. The saturation of magnetizations for the perpendicular and the parallel direction are influenced by crystalline easy direction. In this research, a plating film with a face centered cubic (fcc) structure was obtained. At the same time, their thickness dependent crystalline easy direction and magnetic properties were investigated by main peak intensity of the X-ray diffraction (XRD) and saturation magnetization. The proposed model can also be applied for radioactive Ni-63 electroplating. Nanocrystalline nickel (Ni) coating were synthesized by direct current electrodeposition at current density from 10 to 25 mA/cm{sup 2} and pH=4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2 M Ni ions. The results showed that the surface roughness decreased as the saccharin addition of 2g/l. The experimental results showed that the increase in the current density had a considerable effect on the large residual stress of the Ni deposits. Crystal orientations of the films were estimated by the degree of high (200){sub N}i orientation in the XRD patterns and M-H curves.

  9. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Directory of Open Access Journals (Sweden)

    Sumeet Kumar

    2015-02-01

    Full Text Available In the present study, monodispersed CeO2 nanoparticles (NPs of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD, field emission scanning electron microscope (FE-SEM, high resolution transmission electron microscopy (HR-TEM, ultra-violet visible (UV-VIS spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce4+ into Ce3+ at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm-1 for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms, coercivity (Hc and retentivity (Mr are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce3+ ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce ions located around oxygen vacancies, which causes ferromagnetism in pure CeO2 samples.

  10. Controlled synthesis and magnetic properties of monodispersed ceria nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sumeet; Ojha, Animesh K. [Department of Physics, Motilal Nehru National Institute of Technology, Allahabad-211004 (India); Srivastava, Manish, E-mail: 84.srivastava@gmail.com, E-mail: manish-mani84@rediffmail.com [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Singh, Jay [Department of Applied Chemistry and Polymer Technology, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi 110042 (India); Layek, Samar [Department of Physics, Indian Institute of Technology, Kanpur 208016 (India); Yashpal, Madhu [Electron Microscope Facility, Department of Anatomy Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005 (India); Materny, Arnulf [Center for Functional Materials and Nanomolecular Science, Jacobs University Bremen, Campus Ring, 28759 Bremen (Germany)

    2015-02-15

    In the present study, monodispersed CeO{sub 2} nanoparticles (NPs) of size 8.5 ± 1.0, 11.4 ± 1.0 and 15.4 ± 1.0 nm were synthesized using the sol-gel method. Size-dependent structural, optical and magnetic properties of as-prepared samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscopy (HR-TEM), ultra-violet visible (UV-VIS) spectroscopy, Raman spectroscopy and vibrating sample magnetometer (VSM) measurements. The value of optical band gap is calculated for each particle size. The decrease in the value of optical band gap with increase of particle size may be attributed to the quantum confinement, which causes to produce localized states created by the oxygen vacancies due to the conversion of Ce{sup 4+} into Ce{sup 3+} at higher calcination temperature. The Raman spectra showed a peak at ∼461 cm{sup -1} for the particle size 8.5 nm, which is attributed to the 1LO phonon mode. The shift in the Raman peak could be due to lattice strain developed due to variation in particle size. Weak ferromagnetism at room temperature is observed for each particle size. The values of saturation magnetization (Ms), coercivity (Hc) and retentivity (Mr) are increased with increase of particle size. The increase of Ms and Mr for larger particle size may be explained by increase of density of oxygen vacancies at higher calcination temperature. The latter causes high concentrations of Ce{sup 3+} ions activate more coupling between the individual magnetic moments of the Ce ions, leading to an increase of Ms value with the particle size. Moreover, the oxygen vacancies may also produce magnetic moment by polarizing spins of f electrons of cerium (Ce) ions located around oxygen vacancies, which causes ferromagnetism in pure CeO{sub 2} samples.

  11. Magnetic properties in III-V diluted magnetic semiconductor quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Dakhlaoui, H. [Departement de Physique, Faculte des Sciences de Bizerte, 7000 (Tunisia); Jaziri, S. [Departement de Physique, Faculte des Sciences de Bizerte, 7000 (Tunisia)]. E-mail: sihem.jaziri@fsb.rnu.tn

    2005-01-31

    Spin injection in low-dimensional semiconductors have a great potential to be used in magnetoelectronics and spintronics. In our work we analyze the electronic properties of the hole gas formed in Ga{sub 1-x}Mn{sub x}As/GaAs/Ga{sub 1-x}Mn{sub x}As heterostructures. We find that there is an RKKY-type exchange coupling between the magnetic layers that oscillates between ferromagnetic and antiferromagnetic as a function of the different parameters of the problem. As an example we calculate the spin-dependent hole density, the polarization and the coupling energy, using an efficient self-consistent procedure to solve simultaneously the Schroedinger and Poisson equations, taking into account the interaction with Mn magnetic moments. Our results indicate that the coupling energy also oscillates in terms of the band offset V{sub w} which describes the difference in electronegativity between the Mn and GaAs atoms.

  12. Investigation of structure and magnetic properties of nanocrystalline iron oxide powders for use in magnetic fluids

    Energy Technology Data Exchange (ETDEWEB)

    Lukashova, N.V.; Savchenko, A.G. [National University of Science and Technology ’’MISIS’’, 4, Leninsky pr., Moscow (Russian Federation); Yagodkin, Yu.D., E-mail: yag52@mail.ru [National University of Science and Technology ’’MISIS’’, 4, Leninsky pr., Moscow (Russian Federation); Muradova, A.G.; Yurtov, E.V. [Mendeleev University of Chemical Technology, Miusskaya sq., 9, Moscow (Russian Federation)

    2014-02-15

    Highlights: • The iron oxide nanopowders were obtained by chemical methods. • The particles of the nanopowders had different size. • The structure and magnetic behavior of the powders depend on nanoparticle size. -- Abstract: Iron oxide nanopowders with particles of different size, obtained by co-precipitation and sonochemical methods, were studied by X-ray diffraction, transmission electron microscopy and Mössbauer spectroscopy. The average size of nanoparticles obtained by a co-precipitation method, was about 10 nm. The main phase component of such nanoparticles was maghemite phase γ-Fe{sub 2}O{sub 3}. It was shown, that these nanoparticles were superparamagnetic. In contrast, the nanoparticles obtained by sonochemical method, consisted of larger particles with an average size of around 25 nm. Their main phase component was magnetite Fe{sub 3}O{sub 4}. This powder clearly showed hard magnetic properties.

  13. Homometallic and Heterometallic Antiferromagnetic Rings: Magnetic Properties Studied by Nuclear Magnetic Resonance

    Energy Technology Data Exchange (ETDEWEB)

    Casadei, Cecilia [Univ. of Pavia (Italy)

    2011-01-01

    The aim of the present thesis is to investigate the local magnetic properties of homometallic Cr8 antiferromagnetic (AFM) ring and the changes occurring by replacing one Cr3+ ion with diamagnetic Cd2+ (Cr7Cd) and with Ni2+ (Cr7Ni). In the heterometallic ring a redistribution of the local magnetic moment is expected in the low temperature ground state. We have investigated those changes by both 53Cr-NMR and 19F-NMR. We have determined the order of magnitude of the transferred hyperfine coupling constant 19F - M+ where M+ = Cr3+, Ni2+ in the different rings. This latter result gives useful information about the overlapping of the electronic wavefunctions involved in the coordinative bond.

  14. Influence of Inhomogeneous Composition of Rock on Macroscopic Mechanical Properties%岩石非均质构成对宏观力学特性的影响研究

    Institute of Scientific and Technical Information of China (English)

    罗荣; 曾亚武

    2012-01-01

    The inhomogeneous composition of rock is described by using the random parameter assignment method of rock mineral cell unit which is based on the contents (sort and ratio) of the rock forming minerals. The hybrid models with two mineral cell units and three mineral cell units that simulate inhomogeneous rock are used to carry out numerical test to research the influence of inhomogeneiry on macroscopic stress-strain curve. Besides, based on the rock mineral composition (sort and ratio), the parameter of inhomogeneity degree is defined. The influence of inhomogeneiry degree on the macroscopic mechanical parameters (elastic modulus and ultimate strength) are analyzed according to results of the numerical test. The research result indicates that mechanical property of homogeneity rock is determined by the mechanical properties of the units, while inhomogeneous rock is determined by both the mechanical properties of the units and the rock mineral composition. When the parameter of inhomogeneity degree is small, the weakening effect of elastic modulus caused by inhompgeneity is small, and vice versa. The influence on ultimate strength is the same as that on elastic modulus.%利用岩石矿物细胞元随机性参数赋值方法描述岩石的非均质构成,分别针对2类矿物细胞元和3类矿物细胞元构成的非均质岩石模型,研究了岩石非均质构成对其宏观应力-应变关系曲线的影响.基于岩石矿物构成定义了岩石的非均质度,根据数值模拟计算结果分析了岩石非均质度对岩石宏观力学参数(宏观弹性模量、极限强度)的影响.研究结果表明:均质岩石宏观力学特性由细胞元力学特性决定,非均质岩石宏观力学特性由细胞元力学特性和岩石非均质构成共同决定;在非均质度较小时,宏观弹性模量受岩石非均质性的弱化影响较小,反之,当非均质度较大时,宏观弹性模量受非均质性的弱化影响较大;宏观极限强度受岩石

  15. Properties of a new magnetic material: Sr2FeMoO6

    Indian Academy of Sciences (India)

    D D Sarma; Sugata Ray

    2001-10-01

    Recently, there have been a large number of investigations of the physical properties of Sr2FeMoO6 and related compounds, in view of their significant negative magnetoresistive property at room temperature and in low applied magnetic fields. We review these investigations, detailing the microscopic mechanism controlling the electronic and magnetic properties of this system.

  16. Microscopic Magnetic Properties of the Itinerant Metamagnet UCoAl by X-ray Magnetic Circular Dichroism

    Science.gov (United States)

    Combier, Tristan; Palacio-Morales, Alexandra; Sanchez, Jean-Pierre; Wilhelm, Fabrice; Pourret, Alexandre; Brison, Jean-Pascal; Aoki, Dai; Rogalev, Andrei

    2017-02-01

    The itinerant metamagnet UCoAl has been investigated by high field X-ray magnetic circular dichroism (XMCD) at the U M4,5 and Co K edges. The orbital and spin moments of U at 2.1 K for H || c applied below and above the first order metamagnetic transition field (HM) have been determined. The magnetism of UCoAl is dominated by the U moment. There is no evidence for any change of the orbital to spin moment ratio (˜-2.05) across HM and within the ferromagnetic phase up to 17 T. The possibility of a Fermi surface reconstruction at HM remains an open option. XMCD at the Co K-edge reveals the presence of a small Co 4p-orbital moment parallel to the macroscopic magnetization. In addition, the Co 3d-moment is estimated to be at most 0.1 μB at 17 T. The similar field dependence of the U and Co magnetizations indicates that the Co moment is induced by the U moment.

  17. Test of Annealing to Improve the Magnetic Properties for CYCIAE-100

    Institute of Scientific and Technical Information of China (English)

    ZHONG; Jun-qing; CUI; Tao; LI; Ming

    2012-01-01

    <正>The magnetic properties of the magnet can be influenced by the chemical composition and structureof the material.The higher the carbon content is,the higher the carbide content will be;meanwhile,themagnetic reluctance is greater and the magnet will be more difficult to be magnetized;the grain size islarger and the maximum permeability is higher.Because the final goal of the magnetic heat treatment is to

  18. Chromium removal by combining the magnetic properties of iron oxide with adsorption properties of carbon nanotubes.

    Science.gov (United States)

    Gupta, V K; Agarwal, Shilpi; Saleh, Tawfik A

    2011-03-01

    The adsorption features of multiwall carbon nanotubes (MWCNTs) with the magnetic properties of iron oxides have been combined in a composite to produce a magnetic adsorbent. Composites of MWCNT/nano-iron oxide were prepared, and were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR). XRD suggests that the magnetic phase formed is maghemite and/or magnetite. FESEM image shows nano-iron oxides attached to a network of MWCNTs. The adsorption capability of the composites was tested in batch and fixed bed modes. The composites have demonstrated a superior adsorption capability to that of activated carbon. The results also show that the adsorptions of Cr(III) on the composites is strongly dependent on contact time, agitation speed and pH, in the batch mode; and on flow rate and the bed thickness in the fixed bed mode. Along with the high surface area of the MWCNTs, the advantage of the magnetic composite is that it can be used as adsorbent for contaminants in water and can be subsequently controlled and removed from the medium by a simple magnetic process. Copyright © 2011 Elsevier Ltd. All rights reserved.

  19. Enhanced magnetic properties in Nd-Fe-B magnets prepared by spark plasma sintering via die-upsetting process

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHU Linhua; LI Jun; LIU Ying

    2011-01-01

    The magnetic properties and microstructure of Nd-Fe-B magnets prepared by spark plasma sintering with different die-upsetting processes were investigated.The results showed that the optimum magnetic properties of die-upset Nd-Fe-B magnets were obtained at 680 ℃ when the die-upset level was 60%,and the degree of magnetic alignment was 0.84.The microstructures showed that the coarse grains occurred predominantly within certain areas,and abnormal grain growth was not observed within the major areas of well-aligned grains.There existed many small spherical grains,which stacked together and were not aligned during die upsetting when the deformation temperature was 650 ℃.These small spherical grains grew up,and were aligned when the deformation temperature increased from 650 to 680 ℃,which could improve the crystallographic alignment of die-upset Nd-Fe-B magnets.

  20. Enhancement of electric and magnetic properties by tuning Co cluster in ZnO films via high magnetic field

    Science.gov (United States)

    Gao, Yang; Li, Guojian; Wang, Zhao; Liu, Shan; Wang, Qiang

    2017-09-01

    To reveal the origin of magnetic coupling in dilute magnetic semiconductors (DMSs), this article utilized high magnetic field (HMF) in the process of oxidizing Co/Zn bilayers to study the influence of Co clusters and oxygen vacancy (Vo) content control on magnetic and electrical properties of Co doped ZnO (Co-ZnO) films. Results indicated that HMF can suppress the diffusion of Co and remain the content of Co clusters compared with oxidation growth in the absence of HMF. Moreover, HMF promoted the oxidation of Zn, improved the crystallinity in the films, and lowered the content of Vo. Consequently, the resistivity of the films oxidized in HMF was decreased by 50%, while both the saturation magnetization and coercivity were increased by 100%. This indicates that contribution of more Co clusters to the magnetic properties of the films is greater than that of Vo.

  1. Effects of boron-doping on the morphology and magnetic property of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    JIANG Qi; QIAN Lan; YI Jing; ZHU Xiaotong; ZHAO Yong

    2007-01-01

    Boron carbide nanotubes (nano-fibers) was prepared by B powder and carbon nanotubes (CNTs) at high temperature in a vacuumed quartz tube.The morphology,microstructure,component and magnetic property of samples were characterized by transmission electron microscopy (TEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and magnetic property measurement system (MPMS) controller.The results showed that B-doping CNTs have great difference in the morphology and magnetic property from those of pristine CNTs.

  2. Effect of O-vacancies on magnetic properties of bismuth ferrite nanoparticles by solution evaporation method

    Energy Technology Data Exchange (ETDEWEB)

    Afzal, A.M., E-mail: Amirafzal461@gmail.com [Department of Physics, GC University, Faisalabad 38000 (Pakistan); Umair, M., E-mail: umairranwerr@gmail.com [Department of Physics, GC University, Faisalabad 38000 (Pakistan); Dastgeer, G., E-mail: dtedastgeer@gmail.com [Department of Physics, University of Agriculture, Faisalabad 38000 (Pakistan); Rizwan, M., E-mail: h.rizwan70@gmail.com [Department of Physics, GC University, Faisalabad 38000 (Pakistan); Yaqoob, M.Z., E-mail: zeeshaan32@gmail.com [Department of Physics, GC University, Faisalabad 38000 (Pakistan); Rashid, R., E-mail: rashid.kanwar22@gmail.com [Department of Physics, University of Agriculture, Faisalabad 38000 (Pakistan); Munir, H.S., E-mail: sadiamunir.cute@gmail.com [Department of Physics, GC University, Faisalabad 38000 (Pakistan)

    2016-02-01

    Bismuth ferrite is a multiferroic material which shows high magnetization and polarization at room temperature. In present work, the effect of Oxygen (O) vacancies on magnetic properties of bismuth ferrite nanoparticles is studied. Bismuth ferrite nanoparticles (BiFeO{sub 3}) were synthesized by solution evaporation method (SEM) at room temperature. The sample was annealed under two different atmospheres such as in air and oxygen, to check the effect of O-vacancies on magnetic properties. The average crystallite size of Bismuth ferrite nanoparticles (NPs) as calculated by X-ray diffraction (XRD) falls in the range of 23–32 nm and 26–39 nm for the case of air and oxygen respectively. The crystallite size of bismuth ferrite nanoparticles increases as the temperature was varied from 450 °C to 650 °C. Further the influence of annealing temperature on the magnetic properties of the bismuth ferrite nanoparticles was also observed. It was concluded that the magnetic properties of Bismuth ferrite nanoparticles are directly interconnected to annealing atmosphere and annealing temperature. The magnetic properties were increased in the case of oxygen annealing, which actually leads in our case to an improvement of the crystallinity. - Highlights: • Bismuth ferrite was synthesized by solution evaporation method. • The effect of different annealing atmosphere on magnetic properties was studied. • The magnetic properties dramatically increased in case of Oxygen annealing. • The influence of crystalline size on magnetic properties was studied. • The magnetization was decreased as the temperature and crystallite size increased.

  3. Quantum correlations of lights in macroscopic environments

    Science.gov (United States)

    Sua, Yong Meng

    This dissertation presents a detailed study in exploring quantum correlations of lights in macroscopic environments. We have explored quantum correlations of single photons, weak coherent states, and polarization-correlated/polarization-entangled photons in macroscopic environments. These included macroscopic mirrors, macroscopic photon number, spatially separated observers, noisy photons source and propagation medium with loss or disturbances. We proposed a measurement scheme for observing quantum correlations and entanglement in the spatial properties of two macroscopic mirrors using single photons spatial compass state. We explored the phase space distribution features of spatial compass states, such as chessboard pattern by using the Wigner function. The displacement and tilt correlations of the two mirrors were manifested through the propensities of the compass states. This technique can be used to extract Einstein-Podolsky-Rosen correlations (EPR) of the two mirrors. We then formulated the discrete-like property of the propensity P b(m,n), which can be used to explore environmental perturbed quantum jumps of the EPR correlations in phase space. With single photons spatial compass state, the variances in position and momentum are much smaller than standard quantum limit when using a Gaussian TEM 00 beam. We observed intrinsic quantum correlations of weak coherent states between two parties through balanced homodyne detection. Our scheme can be used as a supplement to decoy-state BB84 protocol and differential phase-shift QKD protocol. We prepared four types of bipartite correlations +/- cos2(theta1 +/- theta 2) that shared between two parties. We also demonstrated bits correlations between two parties separated by 10 km optical fiber. The bits information will be protected by the large quantum phase fluctuation of weak coherent states, adding another physical layer of security to these protocols for quantum key distribution. Using 10 m of highly nonlinear

  4. Fe-based magnetic nanomaterials: Wet chemical synthesis, magnetic properties and exploration on applications

    Science.gov (United States)

    Xiaoliang, Hong

    Even though the start of research based on Fe-based magnetic nanomaterials could be dated back to hundreds years ago, the considerably large amount of emerging fields for their applications, including spintronic structures in information storage, biomedical and environmental applications, magnetic sensors, magnetic energy harvesters, has spurred renewed interest on the application-related properties of Fe-based nanomaterial in both the nanoparticle and film forms. Besides, an exploration of a simple, wide, effective technique that can be used for growth of high-quality Fe-based magnetic nanoparticles and films is of great importance for better materialization of these potential Fe-based devices. This thesis mainly focuses on fabricating different magnetic Fe-based materials (ferrites and ferrous alloys, nanoparticle and film) with wet chemical method, investigating their growth mechanism and magnetic and electrical properties. In addition, the possible applications of as-fabricated Fe-based nanoparticles and films are studied. The contribution of the work is summarized as below: (1) Investigation indicated that the external magnetic field plays an important role in determining the microstructure, magnetic properties of the Fe3O4 nanoparticles. The magnetic field can promote the change of Fe3O4 nanocuboctahedrons to nanocubes. Compared the hyperthermia property of as-fabricated nanocuboctahedrons and nanocubes Fe3O4, the intrinsic loss power (ILP) of the Fe3O4 nanocubes was much higher than that of nanocuboctahedrons due to the surface magnetic effect. (2) A general and facile method for broadly deposition of thick Fe 3O4 film and other ferrites has been demonstrated. It had been found that the epitaxial high-quality Fe3O4 film could be deposited either on MgO substrates directly or Si substrates with Fe3O4 seed layer deposited by PLD. As-deposited Fe 3O4 film could be easily patterned and shows potential applications for microwave and MEMS supercapacitor. Besides

  5. High magnetic field properties of Fe-pnictide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kurth, Fritz

    2015-11-20

    The recent discovery of high-temperature superconductivity in Fe-based materials triggered worldwide efforts to investigate their fundamental properties. Despite a lot of similarities to cuprates and MgB{sub 2}, important differences like near isotropic behaviour in contrast to cuprates and the peculiar pairing symmetry of the order parameter (OP) have been reported. The OP symmetry of Fe-based superconductors (FBS) was theoretically predicted to be of so-called s± state prior to various experimental works. Still, most of the experimental results favour the s± scenario; however, definitive evidence has not yet been reported. Although no clear understanding of the superconducting mechanisms yet exists, potential applications such as high-field magnets and Josephson devices have been explored. Indeed, a lot of reports about FBS tapes, wires, and even SQUIDs have been published to this date. In this thesis, the feasibility of high-field magnet applications of FBS is addressed by studying their transport properties, involving doped BaFe{sub 2}As{sub 2} (Ba-122) and LnFeAs(O,F) [Ln=Sm and Nd]. Particularly, it is important to study physical properties in a sample form (i.e. thin films) that is close to the conditions found in applications. However, the realisation of epitaxial FBS thin films is not an easy undertaking. Recent success in growing epitaxial FBS thin films opens a new avenue to delve into transport critical current measurements. The information obtained through this research will be useful for exploring high-field magnet applications. This thesis consists of 7 chapters: Chapter 1 describes the motivation of this study, the basic background of superconductivity, and a brief summary of the thin film growth of FBS. Chapter 2 describes experimental methods employed in this study. Chapter 3 reports on the fabrication of Co-doped Ba-122 thin films on various substrates. Particular emphasis lies on the discovery of fluoride substrates to be beneficial for

  6. Approximating macroscopic observables in quantum spin systems with commuting matrices

    CERN Document Server

    Ogata, Yoshiko

    2011-01-01

    Macroscopic observables in a quantum spin system are given by sequences of spatial means of local elements $\\frac{1}{2n+1}\\sum_{j=-n}^n\\gamma_j(A_{i}), \\; n\\in{\\mathbb N},\\; i=1,...,m$ in a UHF algebra. One of their properties is that they commute asymptotically, as $n$ goes to infinity. It is not true that any given set of asymptotically commuting matrices can be approximated by commuting ones in the norm topology. In this paper, we show that for macroscopic observables, this is true.

  7. Magnetic and mechanical properties of deformable hard magnetic alloys on the Fe-Cr-Co system with 7% - 8% cobalt

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ With the purpose of the further increase of an economic efficiency hard magnetic alloys on the basis of system Fe-Cr-Co the study of magnetic and mechanical properties of alloys of this system in wt. % (26-30)Cr, (7-10)Co doped Ti, Si, V and Mo is carried out.

  8. Magnetic and mechanical properties of deformable hard magnetic alloys on the Fe-Cr-Co system with 7% - 8% cobalt

    Institute of Scientific and Technical Information of China (English)

    Milyaev; A.; I.; Kovneristii; Ju.; K.; Yusupov; V.; S.; Korznikova; G.; F.

    2005-01-01

    With the purpose of the further increase of an economic efficiency hard magnetic alloys on the basis of system Fe-Cr-Co the study of magnetic and mechanical properties of alloys of this system in wt. % (26-30)Cr, (7-10)Co doped Ti, Si, V and Mo is carried out.……

  9. The Effect of Pressure on Magnetic Properties of KMnCr(CN6.

    Directory of Open Access Journals (Sweden)

    Csach K.

    2013-01-01

    Full Text Available In the contribution we present the effect of pressure on magnetic properties of molecule based magnet KMnCr(CN6. Applied pressure affects magnetization curves only marginally. The saturation is reached at higher magnetic fields under pressure, but the effect of the pressure on the values of saturated magnetization µs, remnant magnetization µr and coercive field HC are almost negligible. Observed pronounced increase of the Curie temperature TC with increasing pressure can be attributed to strengthening of antiferromagnetic superexchange interaction. Additionally we observed double magnetic transition induced by hydrostatic pressure. All pressure changes were fully reversible.

  10. Dependence of the magnetization on the interface morphology in ultra-thin magnetic/non-magnetic films: Monte Carlo approach

    Energy Technology Data Exchange (ETDEWEB)

    Razouk, A. [Laboratoire de Physique et Mecanique des Materiaux, Faculte des Sciences et Techniques, Universite Sultan Moulay Slimane, BP 523, 23000 Beni-Mellal (Morocco); Sahlaoui, M., E-mail: msahlaoui@yahoo.fr [Laboratoire de Physique et Mecanique des Materiaux, Faculte des Sciences et Techniques, Universite Sultan Moulay Slimane, BP 523, 23000 Beni-Mellal (Morocco); Sajieddine, M. [Laboratoire de Physique et Mecanique des Materiaux, Faculte des Sciences et Techniques, Universite Sultan Moulay Slimane, BP 523, 23000 Beni-Mellal (Morocco)

    2009-07-30

    Using Monte Carlo simulations, we have studied the dependence of magnetic properties on interface morphology in magnetic/non-magnetic (M/NM) multilayers. Our aim is to relate macroscopic magnetic properties of the multilayers to their concentration profile at the interface. Our model consists of an alternate staking of magnetic and non-magnetic layers with disordered interfaces. We have considered different concentration and the existence of local magnetic domains at the interface. The results indicate the crucial dependence of magnetization amplitude with interface multilayers atomic composition and the spatial arrangement of magnetic atoms. In particular, we show that isolated islands at the interface leads to the apparition of super-paramagnetic behavior.

  11. Shock consolidation of Sm-Fe-N magnetic powders and magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Chiba, A.; Ooyabu, K.; Kozuka, T. [Faculty of Engineering, Kumamoto Univ., Kumamoto (Japan); Morizono, Y. [Shock Wave and Condensed Matter Research Center, Kumamoto Univ., Kumamoto (Japan); Maeda, T.; Sugimoto, S.; Kawahara, K.; Watanabe, T. [Faculty of Engineering, Tohoku Univ., Sendai (Japan); Kakimoto, E. [Explosive R and D Center, Explosive Div., Asahi Kasei Co., Fukuoka (Japan)

    2004-07-01

    Sm{sub 2}Fe{sub 17}N{sub x} compound is a prospective candidate as a material for high performance permanent magnets because of its good intrinsic magnetic properties with a curie temperature of 747 K, a room-temperature anisotropy field of 14 T and a room-temperature saturation magnetization of 1.5T. However, Sm{sub 2}Fe{sub 17}N{sub x} compound decomposes to {alpha}-Fe and Sm nitride above 873 K and conventional powder metallurgy processing techniques fail to meet the processing requirements. Shock consolidation is a viable alternative to process this compound. Fully dense Sm{sub 2}Fe{sub 17}N{sub x} bulk materials were fabricated by cylindrical explosive consolidation technique using water as a pressure transmitting medium. Explosive consolidation is performed under cold state and fully dense materials can be obtained without any degradation of the characteristics of the powder states. Sound compacts were obtained without any cracks or teas, and the value of (BH){sub max} of Sm{sub 2}Fe{sub 17}N{sub x} compact is 23.8 MGOe. (orig.)

  12. Structural, optical, magnetic and photocatalytic properties of Co doped CuS diluted magnetic semiconductor nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Sreelekha, N.; Subramanyam, K. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); Department of Physics, Raghu Engineering College, Visakhapatnam, Andrapradesh 531162 (India); Amaranatha Reddy, D. [Department of Chemistry and Chemical Institute for Functional Materials, Pusan National University, Busan 609735 (Korea, Republic of); Murali, G. [Department of BIN Fusion Technology & Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk (Korea, Republic of); Ramu, S. [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India); Rahul Varma, K. [Department of Mechanical Engineering, University of California, Berkeley (United States); Vijayalakshmi, R.P., E-mail: vijayaraguru@gmail.com [Department of Physics, Sri Venkateswara University, Tirupati 517502 (India)

    2016-08-15

    Highlights: • Cu{sub 1−x}Co{sub x}S nanoparticles were synthesized via chemical co-precipitation method. • Structural, band gap, magnetization and photocatalysis studies were carried out. • All the doped samples exhibited intrinsic room temperature ferromagnetism. • Effect of magnetic properties on photocatalytic activity was analyzed. • CuS:Co nanoparticles may find applications in photocatalytic and spintronic devices. - Abstract: Pristine and Co doped covellite CuS nanoparticles were synthesized in aqueous solution by facile chemical co-precipitation method with Ethylene Diamine Tetra Acetic Acid (EDTA) as a stabilizing agent. EDAX measurements confirmed the presence of Co in the CuS host lattice. Hexagonal crystal structure of pure and Co doped CuS nanoparticles were authenticated by XRD patterns. TEM images indicated that sphere-shape of nanoparticles through a size ranging from 5 to 8 nm. The optical absorption edge moved to higher energies with increase in Co concentration as indicated by UV–vis spectroscopy. Magnetic measurements revealed that bare CuS sample show sign of diamagnetic character where as in Co doped nanoparticles augmentation of room temperature ferromagnetism was observed with increasing doping precursor concentrations. Photocatalytic performance of the pure and Co doped CuS nanoparticles were assessed by evaluating the degradation rate of rhodamine B solution under sun light irradiation. The 5% Co doped CuS nanoparticles provide evidence for high-quality photocatalytic activity.

  13. Influence of antiferromagnetic FeMn on magnetic properties of perpendicular magnetic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Feng Chun; Li Baohe; Teng Jiao; Jiang Yong [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); Yu Guanghua [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)], E-mail: ghyu@mater.ustb.edu.cn

    2009-02-27

    We studied the influence of an anitferromagnetic FeMn layer on perpendicular magnetic anisotropy (PMA) and perpendicular coercivity (H{sub C}-perpendicular ) of the CoCr/Pt multilayers and found that both PMA and H{sub C}-perpendicular can be enhanced by the FeMn layer. We observed an obvious exchange coupling between FeMn and CoCr/Pt multilayers which enhances PMA and may increase the density of pinning sites that can pin the domain wall of ferromagnetic layers and lifts up energy barrier during the propagation of domain walls. This leads to the enhancement of H{sub C}-perpendicular . Moreover, X-ray diffraction results shows that the (111) texture of the FeMn layer enhances that of the CoCr/Pt multilayers, leading to the increase of PMA and H{sub C}-perpendicular as well. This result is of great significance on improving magnetic properties of perpendicular magnetic recording media by using an antiferromagnetic manganese alloy.

  14. Magnetic Properties and Kinetics Parameters of Electroless Magnetic Loss CoFeB Films

    Institute of Scientific and Technical Information of China (English)

    LIU Chang-hui; HE Hua-hui; SHEN Xiang; LI Hai-hua

    2008-01-01

    Electroless CoFeB films with good soft magnetic properties were fabricated on polyester plastic substrate from sodium tartarate as a complexing agent. The plating rate of electroless CoFeB films is a function of concentration of sodium tetrahydroborate, pH of the plating bath, plating temperature and the metallic ratio. The estimated regression coefficient b0-b3 confidence interval, residual error r and confidence interval rint were confirmed by a computer program. The optimal composition of the plating bath was obtained and the dynamic electromagnetic parameters of films were measured in the 2-10 GHz range. At 2 GHz, the μ′, μ″ of the electroless CoFeB films were 304 and 76.6, respectively, as the concentration of reducer is 1 g/L. Magnetic hysteresis loop of the deposited CoFeB films show a remanence close to the saturation magnetization and coercivity of about 55.7-127.4 A/m. The loops along the hard axis display low anisotropic field Hk of 2 388-3 582 A/m.

  15. Magnetic Properties of Nd-Fe-B Sintered Magnet Powders Recovered by Yb Metal Vapor Sorption

    Institute of Scientific and Technical Information of China (English)

    Horikawa T; Itoh M; Suzuki Shunji; Machida K

    2004-01-01

    Fine ground powders of Nd-Fe-B sintered magnet bulks(particle size=46~125 μm in diameter) were coated and alloyed with Yb metal by sorbing them. A significant recovery of the decreased magnetic properties of the ground powders(remanence Br=~0.95 T, coercivity Hcj =~227 kA·m-1 and maximum energy product(BH)max=~48.8 kJ·m-3) was observed in accordance with increasing temperature up to 800 ℃. The sorbing temperature and time for Yb metal vapor were optimized and after heating at 800 ℃ for 90 min and annealing subsequently at 610 ℃ for 60 min, the Br, Hcj and(BH)max values were increased to be 0.98 T, 712 kA·m-1 and 173 kJ·m-3, respectively. From the microstructural characterizations of resulting samples by using X-ray diffraction(XRD), scanning electron microscopy(SEM), and electron probe X-ray microanalyzer(EPMA), it is found that the sorbed Yb metal uniformly covers the surface and diffuses to the Nd-rich grain boundary of fine ground powders of Nd-Fe-B sintered magnet bulks forming a(Nd,Yb)Fe2 phase.

  16. Magnetic Properties of Hydrothermalized A-type Red Granites

    Science.gov (United States)

    Trindade, R. I. F.; Nédélec, A.; Peschler, A.; Archanjo, C. J.; Poitrasson, F.; Bouchez, J. L.

    Hydrothermalized A-type granites are commonly identified by their pink to red-brick colour attributed to tiny flakes of hematite in the alkali feldspars. These inclusions can be of interest in magnetic studies, but their timing and process of formation are still unclear. Formation of chlorite after biotite is the commonest effect of hydrother- malization and may occur quite early after crystallization due to late-magmatic or externally-derived fluids. The reddish colour appears at a later stage. Five cases of A-type granites were investigated for their magnetic mineralogy and properties. The selected cases range from nearly unmodified granites (Panafrican stratoid granites of Madagascar) to strongly hydrothermalized ones (Meruoca, Brazil; Tana, Corsica); in- termediate cases are : Mount Scott (Oklahoma), Bushveld (granitic core kindly pro- vided by R.G. Cawthorn) and. Hydrothermal alteration is often associated to a de- crease of the magnetic susceptibility magnitude (K) and of the anisotropy degree (P). It also strongly affects the rockt's bulk coercivity parameters, since alteration changes the relative amounts of coarse-grained primary magnetite, fine-grained PSD to SD sec- ondary magnetite, and hematite. Correspondingly, most samples plot away from the magnetite trend in the Dayt's diagram, but the different groups identified after coer- civity parameters do not directly correlate with whole-rock colour. In addition, IRM- acquisition curves and thermal demagnetization of tri-axial IRM show that hematite occurs in almost all analysed samples despite their colour. Various hematite coercivity ranges are also evidenced. In fact, hematite can be formed either in feldspar crys- tals or after magnetite. Tiny hematite within feldspars can appear either by exsolu- tion process or, more likely, by precipitation from a fluid phase. For these reasons, hematite inclusions may carry a remanence acquired shortly after granite crystalliza- tion or, conversely, a recent

  17. Microscopic versus macroscopic calculation of dielectric nanospheres

    Science.gov (United States)

    Kühn, M.; Kliem, H.

    2008-12-01

    The issue of nanodielectrics has recently become an important field of interest. The term describes nanometric dielectrics, i. e. dielectric materials with structural dimensions typically smaller than 100 run. In contrast to the behaviour of a bulk material the nanodielectrics can behave completely different. With shrinking dimensions the surface or rather boundary effects outweigh the volume effects. This leads to a different observable physics at the nanoscale. A crucial point is the question whether a continuum model for the calculation of dielectric properties is still applicable for these nanomaterials. In order to answer this question we simulated dielectric nanospheres with a microscopic local field method and compared the results to the macroscopic mean field theory.

  18. Magnetic and mineralogical properties of salt rocks from the Zechstein of the Northern German Basin

    Science.gov (United States)

    Heinrich, Frances C.; Schmidt, Volkmar; Schramm, Michael; Mertineit, Michael

    2017-01-01

    Magnetic properties of rocks are often studied to characterize composition and fabric of rocks. For salt rocks, the basic relationships between their magnetic properties and composition, which are necessary to interpret rock magnetic data, are not yet established. Therefore, we studied different types of natural salt rock and pure salt minerals. We measured their magnetic properties (magnetic susceptibility, IRM acquisition curves, FORC diagrams, temperature-dependent magnetic susceptibility) and used analytical methods such as microscopy, XRD and ICP-OES to understand the relationship between magnetic properties and mineralogy. Salt rocks mainly consist of the diamagnetic minerals halite, carnallite, sylvine and anhydrite with negative magnetic susceptibilities. The magnetic susceptibilities of pure synthetic NaCl and KCl single crystals, show values of -14.5 × 10-6 SI and -13.5 × 10-6 SI, respectively. In contrast, in natural salt rocks higher magnetic susceptibility values were measured. The magnetic susceptibility of the samples investigated in this study shows a general increase from light rock salt (max. -10 × 10-6 SI) over carnallitite (max. 134 × 10-6 SI) to red sylvinite (max. 270 × 10-6 SI). Whole rock analyses suggests that increased magnetic susceptibility can be attributed to paramagnetic and ferromagnetic minerals that are contained within the insoluble residue. The magnetic susceptibility is mainly controlled by magnetite and phyllosilicates. Its measurement can therefore be used to detect subtle changes in the content of these minerals.

  19. Hydration of swelling clays: multi-scale sequence of hydration and determination of macroscopic energies from microscopic properties; Hydratation des argiles gonflantes: sequence d'hydratation multi-echelle determination des energies macroscopiques a partir des proprietes microscopiques

    Energy Technology Data Exchange (ETDEWEB)

    Salles, F

    2006-10-15

    Smectites have interesting properties which make them potential candidates for engineered barriers in deep geological nuclear waste repository: low permeability, swelling and cations retention. The subject of this thesis consists in the determination of the relationship between hydration properties, swelling properties and cations mobility in relation with confinement properties of clayey materials. The aim is to understand and to predict the behaviour of water in smectites, following two research orientations: the mechanistic aspects and the energetic aspects of the hydration of smectites. We worked on the Na-Ca montmorillonite contained in the MX80 bentonite, with the exchanged homo ionic structure (saturated with alkaline cations and calcium cations). The approach crosses the various scales (microscopic, mesoscopic and macroscopic) and implied the study of the various components of the system (layer-cation-water), by using original experimental methods (thermo-poro-metry and electric conductivity for various relative humidities (RH) and electrostatic calculations. Initially, the dry state is defined by SCTA (scanning calorimetry thermal analysis). Then a classical characterization of the smectite porosity for the dry state is carried out using mercury intrusion and nitrogen adsorption. We evidenced the existence of a meso-porosity which radius varies from 2 to 10 nm depending on the compensating cation. The thermo-poro-metry and conductivity experiments performed at various hydration states made it possible to follow the increase in the pore sizes and the cations mobility as a function of the hydration state. We highlight in particular the existence of an osmotic mesoscopic swelling for low RH (approximately 50-60%RH for Li and Na). By combining the results of thermo-poro-metry, X-ray diffraction and electric conductivity, we are able to propose a complete hydration sequence for each cation, showing the crucial role of the compensating cation in the hydration of

  20. Synthesis and magnetic properties of CoPt nanoparticles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhongyan; WANG Hao; WANG Hanbin; MO Qi; CHEN Yan; ZHANG Cong

    2006-01-01

    CoPt nanoparticles were prepared by simultaneous thermally reducing Co(CH3COO)2 and Pt(acac)2 in oleylamine with a small quantity of oleic acid. The composition of the particles was controlled by changing the amount of the reactants. Transmission electronic microscopy reveals that Co 48 Pt 52 particles with an average diameter of 8.4 nm are steadily dispersed in octane in the presence of oleylamine and oleic acid. Selected area electron diffraction indicates that the as-prepared particles have a face center cubic structure. Magnetic properties of these particles measured by a vibrate sample magnetometer yield a coercivity of 1.194×104 A·m-1 and a saturation magnetization of 5.3 emu·g-1 . After annealing at 650 ℃ for 2 h under the flowing Ar, the coercivity increases to 9.552×104 A·m-1 according to partly phase transformation from face center cubic structure to face center tetragonal structure for the nanoparticles.

  1. Optical Properties of Graphene in Magnetic and Electric fields

    CERN Document Server

    Lin, Chiun-Yan; Huang, Yao-Kung; Lin, Ming-Fa

    2016-01-01

    Optical properties of graphene are explored by using the generalized tight-binding model. The main features of spectral structures, the form, frequency, number and intensity, are greatly enriched by the complex relationship among the interlayer atomic interactions, the magnetic quantization and the Coulomb potential energy. Absorption spectra have the shoulders, asymmetric peaks and logarithmic peaks, coming from the band-edge states of parabolic dispersions, the constant-energy loops and the saddle points, respectively. The initial forbidden excitation region is only revealed in even-layer AA stacking systems. Optical gaps and special structures can be generated by an electric field. The delta-function-like structures in magneto-optical spectra, which present the single, twin and double peaks, are associated with the symmetric, asymmetric and splitting Landau-level energy spectra, respectively. The single peaks due to the non-tilted Dirac cones exhibit the nearly uniform intensity. The AAB stacking possesses...

  2. Magnetic properties and structure of very thin permalloy films

    Institute of Scientific and Technical Information of China (English)

    Guanghua Yu; Haifeng Li; Tao Yang; Fengwu Zhu

    2004-01-01

    In order to study the magnetic properties and structure of very thin permalloy films, Ni81Fe19 films of 12 nm in thickness were prepared by different instruments at an ultrahigh base vacuum and a lower base vacuum. The anisotropic magnetoresistance coefficients (△R/R) of Ni81Fe19 (12 nm) films reached 1.6 % and 0.6 %, and the coercivities were 127 and 334 A/m, respectively. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were used to study the structure and surface chemical state. The experimental results show that the films prepared at the ultrahigh base vacuum have a smoother surface, a bigger grain size and a denser structure with fewer defects than those prepared at the lower base vacuum.

  3. Microscopic and macroscopic infarct complicating pediatric epilepsy surgery.

    Science.gov (United States)

    Rubinger, Luc; Hazrati, Lili-Naz; Ahmed, Raheel; Rutka, James; Snead, Carter; Widjaja, Elysa

    2017-03-01

    There is some suggestion that microscopic infarct could be associated with invasive monitoring, but it is unclear if the microscopic infarct is also visible on imaging and associated with neurologic deficits. The aims of this study were to assess the rates of microscopic and macroscopic infarct and other major complications of pediatric epilepsy surgery, and to determine if these complications were higher following invasive monitoring. We reviewed the epilepsy surgery data from a tertiary pediatric center, and collected data on microscopic infarct on histology and macroscopic infarct on postoperative computed tomography (CT) or magnetic resonance imaging (MRI) done one day after surgery and major complications. Three hundred fifty-two patients underwent surgical resection and there was one death. Forty-two percent had invasive monitoring. Thirty patients (9%) had microscopic infarct. Univariable analyses showed that microscopic infarct was higher among patients with invasive monitoring relative to no invasive monitoring (20% vs. 0.5%, respectively, p microscopic infarct had transient right hemiparesis, and two with both macroscopic and microscopic infarct had unexpected persistent neurologic deficits. Thirty-two major complications (9.1%) were reported, with no difference in major complications between invasive monitoring and no invasive monitoring (10% vs. 7%, p = 0.446). In the multivariable analysis, invasive monitoring increased the odds of microscopic infarct (odds ratio [OR] 15.87, p = 0.009), but not macroscopic infarct (OR 2.6, p = 0.173) or major complications (OR 1.4, p = 0.500), after adjusting for age at surgery, sex, age at seizure onset, operative type, and operative location. Microscopic infarct was associated with invasive monitoring, and none of the patients had permanent neurologic deficits. Macroscopic infarct was not associated with invasive monitoring, and two patients with macroscopic infarct had persistent neurologic deficits. Wiley

  4. Geometric aspects of Schnakenberg's network theory of macroscopic nonequilibrium observables

    Science.gov (United States)

    Polettini, M.

    2011-03-01

    Schnakenberg's network theory deals with macroscopic thermodynamical observables (forces, currents and entropy production) associated to the steady states of diffusions on generic graphs. Using results from graph theory and from the theory of discrete differential forms we recast Schnakenberg's treatment in the form of a simple discrete gauge theory, which allows to interpret macroscopic forces as the Wilson loops of a real connection. We discuss the geometric properties of transient states, showing that heat fluxes allow for a notion of duality of macroscopic observables which interchanges the role of the environment and that of the system. We discuss possible generalizations to less trivial gauge groups and the relevance for nonequilibrium fluctuation theorems. Based on work in collaboration with professor A. Maritan, University of Padua, to be published.

  5. Broadband Macroscopic Cortical Oscillations Emerge from Intrinsic Neuronal Response Failures

    Directory of Open Access Journals (Sweden)

    Amir eGoldental

    2015-10-01

    Full Text Available Broadband spontaneous macroscopic neural oscillations are rhythmic cortical firing which was extensively examined during the last century, however, their possible origination is still controversial. In this work we show how macroscopic oscillations emerge in solely excitatory random networks and without topological constraints. We experimentally and theoretically show that these oscillations stem from the counterintuitive underlying mechanism - the intrinsic stochastic neuronal response failures. These neuronal response failures, which are characterized by short-term memory, lead to cooperation among neurons, resulting in sub- or several- Hertz macroscopic oscillations which coexist with high frequency gamma oscillations. A quantitative interplay between the statistical network properties and the emerging oscillations is supported by simulations of large networks based on single-neuron in-vitro experiments and a Langevin equation describing the network dynamics. Results call for the examination of these oscillations in the presence of inhibition and external drives.

  6. Anisotropically structured magnetic aerogel monoliths

    Science.gov (United States)

    Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

    2014-10-01

    Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and

  7. Hybrid magnetic – Semiconductor nanocomposites: optical, magnetic and nanosecond dynamical properties

    Energy Technology Data Exchange (ETDEWEB)

    Emam, A.N.; Girgis, E.; Mostafa, A.A. [National Research Center, Dokki, Giza (Egypt); Guirguis, O.W. [Biophysics Department, Faculty of Science, Cairo University, Giza (Egypt); Mohamed, M.B., E-mail: monabmohamed@gmail.com [National Institute of Laser Enhanced Science, Cairo University, Giza (Egypt); NanoTech Egypt for Photoelectronics, Dreamland, Giza (Egypt)

    2015-07-15

    A series of colloidal CdSe quantum dots doped with different concentration of cobalt ions has been prepared via organometallic pyrolysis of a mixture of cadmium stearate and cobalt dithiocarbazate. The conditions required for successful doping depend on the source of cobalt ions and the dopant concentration. The structure and morphology of the prepared nanocrystals have been characterized using X-Ray Diffraction (XRD), and Transmission Electron Microscope (TEM). Slight shift in the interplaner space was observed in the XRD pattern of the doped nanocrystals. Formation of separate cobalt nanoclusters has been observed in the TEM images upon increasing the cobalt concentration more than 2% of the original cadmium concentration. This was confirmed by magnetic measurements of the prepared samples. Room-temperature ferromagnetism has been observed, in which the switching field increases as the cobalt ratio increases. Increasing the cobalt ratio more than 5% increases the coercivity due to formation of Co{sup 0} nanoclusters. Moreover, the presence of localized magnetic ions in semiconductor QDs leads to strong exchange interactions between sp band electrons and the magnetic ions d electrons. This would influence the optical properties such as absorption, emission, as well as nanosecond relaxation dynamics. - Graphical abstract: Display Omitted - Highlights: • Hybrid semiconductor-magnetic nanostructure was prepared via chemical method. • Room-temperature ferromagnetism for hybrid CdSe–Co quantum dots has been observed. • Co{sup +2} ions induces slight shift in the interplaner space distance of the doped QDs. • Hybrid CdSe–Co QDs have better quantum yield than pure CdSe QDs. • Hybrid CdSe–Co nanocrystals have faster electron-hole dynamics than pure CdSe QDs.

  8. Optical properties of semiconductor nanostructures in magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Grochol, M.

    2007-04-03

    In this work, the near bandgap linear optical properties of semiconductor quantum structures under applied magnetic field are investigated. First, the exciton theory is developed starting with the one-electron Hamiltonian in a crystal, continuing with the Luttinger and Bir-Pikus Hamiltonian, and ending with the exciton Hamiltonian in the envelope function approximation. Further, concentrating on the quantum well and thus assuming strong confinement in the growth direction, the motion parallel and perpendicular to the xy-plane is factorized leading to the well-known single sublevel approximation. A magnetic field perpendicular to the xy-plane is applied, and a general theorem describing the behavior of the energy eigenvalues is derived. The strain calculation within the isotropic elasticity approach is described in detail. The Schroedinger equation is solved numerically for both the full model and the factorization with artificially generated disorder potentials. Furthermore the statistical properties of the disorder in a real quantum well have been analyzed. In particular, temperature dependent photoluminescence spectra and diamagnetic shift statistics, have been compared with the experimental ones and very good agreement has been found. The second part of this thesis deals predominantly with highly symmetrical structures embedded in the quantum well: namely quantum rings and dots. First, adopting an ansatz for the wave function, the Hamiltonian matrix is derived discussing which matrix elements are non-zero according to the symmetry of the potential. Additionally, the expectation values of the current and magnetization operators are evaluated. Then, concentrating on the case of the highest (circular) symmetry, the model of zero width ring is introduced. Within this model the close relation between the oscillatory component of the exciton energy (exciton Aharonov-Bohm effect) and the persistent current is revealed. Examples for different material systems follow

  9. Structural, magnetic and magnetoelectric properties of Nb substituted Cobalt Ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Ramchandra Kiran, R. [Advanced Magnetic Materials Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Mondal, R.A. [Microwave Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Dwevedi, Sandhya [Department of Condensed Matter Physics and Material Sciences, Tata Institute of Fundamental Research, Mumbai 400005 (India); Markandeyulu, G., E-mail: mark@iitm.ac.in [Advanced Magnetic Materials Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2014-10-15

    Highlights: • Ferroelectricity upon Nb{sup 5+} substitution (d{sup 0} configuration) at B site in CoFe{sub 2}O{sub 4}. • Trigonal distortion at an external magnetic field of 2.2 kOe. • Increase of coercive electric field of Nb substituted CoFe{sub 2}O{sub 4} with frequency. - Abstract: The structural and magnetic properties of bulk polycrystalline CoFe{sub 2}O{sub 4} and niobium substituted Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} prepared by solid state reaction method, are presented in this paper. The lattice parameter of Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} is seen to be more than that of CoFe{sub 2}O{sub 4}. Saturation magnetization, first order magnetocrystalline anisotropy constant calculated using law of approach to saturation and magnetostriction of Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} are seen to be less than those of CoFe{sub 2}O{sub 4}. Longitudinal magnetostriction of Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} measured at room temperature is −123 × 10{sup −6} at a field of 2.2 kOe, with enhanced strain derivative. Field induced trigonal distortion was observed at 2.2 kOe in Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} from the analysis of powder XRD patterns. Co{sub 1.1}Fe{sub 1.85}Nb{sub 0.05}O{sub 4} exhibits ferroelectric and magnetoelectric properties.

  10. Correlation Between Domain Behavior and Magnetic Properties of Materials

    Energy Technology Data Exchange (ETDEWEB)

    Leib, Jeffrey Scott [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, Hc in cases 1, 3, and 5, and the uniaxial character of the Gd5(Si2Ge2), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, Ms, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected

  11. Correlation Between Domain Behavior and Magnetic Properties of Materials

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey Scott Leib

    2003-05-31

    Correlation between length scales in the field of magnetism has long been a topic of intensive study. The long-term desire is simple: to determine one theory that completely describes the magnetic behavior of matter from an individual atomic particle all the way up to large masses of material. One key piece to this puzzle is connecting the behavior of a material's domains on the nanometer scale with the magnetic properties of an entire large sample or device on the centimeter scale. In the first case study involving the FeSiAl thin films, contrast and spacing of domain patterns are clearly related to microstructure and stress. Case study 2 most clearly demonstrates localized, incoherent domain wall motion switching with field applied along an easy axis for a square hysteresis loop. In case study 3, axis-specific images of the complex Gd-Si-Ge material clearly show the influence of uniaxial anisotropy. Case study 4, the only study with the sole intent of creating domain structures for imaging, also demonstrated in fairly simple terms the effects of increasing stress on domain patterns. In case study 5, it was proven that the width of magnetoresistance loops could be quantitatively predicted using only MFM. When all of the case studies are considered together, a dominating factor seems to be that of anisotropy, both magneticrostaylline and stress induced. Any quantitative bulk measurements heavily reliant on K coefficients, such as the saturation fields for the FeSiAl films, H{sub c} in cases 1, 3, and 5, and the uniaxial character of the Gd{sub 5}(Si{sub 2}Ge{sub 2}), transferred to and from the domain scale quite well. In-situ measurements of domain rotation and switching, could also be strongly correlated with bulk magnetic properties, including coercivity, M{sub s}, and hysteresis loop shape. In most cases, the qualitative nature of the domain structures, when properly considered, matched quite well to what might have been expected from theory and

  12. The role of the nature of pillars in the structural and magnetic properties of magnetic pillared vlays

    DEFF Research Database (Denmark)

    Bachir, Cherifa; Lan, Yanhua; Mereacre, Valeriu;

    2011-01-01

    -PILCs, respectively) were produced at different calcination temperatures and then magnetic pillared clays (Ti-M-PILCs, Al-M-PILCs, and Zr-M-PILCs) were prepared at ambient temperature. The synthesis involves a reduction in aqueous solution of the original Fe-exchanged pillared clay using NaBH4. The structural...... properties of pillared clays and their magnetic forms were investigated using X-ray diffraction, N-2 adsorption, cation exchange capacity determination, and X-ray fluorescence (XRF) measurements. The properties of the magnetic pillared clays were investigated by superconducting quantum interference devices...

  13. Effect of particle friction and polydispersity on the macroscopic stress–strain relations of granular materials

    NARCIS (Netherlands)

    Göncü, F.; Luding, S.

    2013-01-01

    The macroscopic mechanical behavior of granular materials inherently depends on the properties of particles that compose them. Using the discrete element method, the effect of particle contact friction and polydispersity on the macroscopic stress response of 3D sphere packings is studied. The analyt

  14. Magnetic properties of (Nd,Pr,Dy)2Fe14B/α-Fe nanocomposite magnets crystallized in a magnetic field

    Science.gov (United States)

    Cui, B. Z.; Huang, M. Q.; Yu, R. H.; Kramp, A.; Dent, J.; Miles, D. D.; Liu, S.

    2003-05-01

    The effect of applying a magnetic field during the crystallization process of a melt-spun Nd2.4Pr5.6Dy1Fe85B6 alloy on the nanostructure, crystallographic texture, exchange coupling, and magnetic properties has been studied. Compared with samples annealed without magnetic field, there was a noticeable improvement in the intrinsic coercivity iHc, the remanence Br, and the maximum magnetic energy product (BH)max for Nd2.4Pr5.6Dy1Fe85B6 alloys annealed in a 12 kOe field. The magnetic performance improved with an increase in the magnetic fields applied up to 9 kOe. Crystallographic alignment and magnetically anisotropic behavior were found in the samples crystallized in the magnetic field. The improvement in magnetic properties after magnetic crystallization is considered to be the result of both magnetic-field-induced crystallite alignment and enhanced exchange coupling due to a reduction of grain size.

  15. Macroscopically-Discrete Quantum Cosmology

    CERN Document Server

    Chew, Geoffrey F

    2008-01-01

    To Milne's Lorentz-group-based spacetime and Gelfand-Naimark unitary representations of this group we associate a Fock space of 'cosmological preons'-quantum-theoretic universe constituents. Milne's 'cosmological principle' relies on Lorentz invariance of 'age'--global time. We divide Milne's spacetime into 'slices' of fixed macroscopic width in age, with 'cosmological rays' defined on (hyperbolic) slice boundaries-Fock space attaching only to these exceptional universe ages. Each (fixed-age) preon locates within a 6-dimensional manifold, one of whose 3 'extra' dimensions associates in Dirac sense to a self-adjoint operator that represents preon (continuous) local time, the operator canonically-conjugate thereto representing preon (total) energy. Self-adjoint-operator expectations at any spacetime-slice boundary prescribe throughout the following slice a non-fluctuating 'mundane reality'- electromagnetic and gravitational potentials 'tethered' to current densities of locally-conserved electric charge and ener...

  16. Seismic scanning tunneling macroscope - Theory

    KAUST Repository

    Schuster, Gerard T.

    2012-09-01

    We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

  17. Effect of optimal aging treatment on magnetic performance and mechanical properties of sintered Nd-Fe-B permanent magnets

    Institute of Scientific and Technical Information of China (English)

    DING Xia; DING Kai-hong; CUI Sheng-li; SUN Yong-cong; LI Mu-sen

    2016-01-01

    The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged NdFeB magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy (FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged NdFeB magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd2Fe14B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.

  18. Preliminary analysis of the MER magnetic properties experiment using a computational fluid dynamics model

    DEFF Research Database (Denmark)

    Kinch, K.M.; Merrison, J.P.; Gunnlaugsson, H.P.;

    2006-01-01

    Motivated by questions raised by the magnetic properties experiments on the NASA Mars Pathfinder and Mars Exploration Rover (MER) missions, we have studied in detail the capture of airborne magnetic dust by permanent magnets using a computational fluid dynamics (CFD) model supported by laboratory...

  19. M(o)ssbauer study and magnetic properties of electrochemical material LiFePO4

    Institute of Scientific and Technical Information of China (English)

    Luo Zhi; Di Nai-Li; Kou Zhi-Qi; Cheng Zhao-Hua; Liu Li-Jun; Chen Li-Quan; Huang Xue-Jie

    2004-01-01

    Magnetic properties and crystal symmetry of electrochemical material LiFePO4 have been investigated by Mossbauer spectroscopy and magnetization measurement. Magnetization reveals the antiferromagnetic nature of LiFePO4. Temperature dependence of inverse susceptibility and that of hyperfine field confirm that there is an antiferromagnetic-paramagnetic transition at about 50K.

  20. Magnetic, structural, and dielectric properties of CuB(2)O(4)

    NARCIS (Netherlands)

    Nenert, G.; Bezmaternykh, L. N.; Vasiliev, A. N.; Palstra, T. T. M.

    2007-01-01

    We have studied the magnetic, structural, and dielectric properties of a single crystal of CuB(2)O(4). We show that both reported magnetic transitions are observable in the magnetization, irrespective of the measured direction of the crystal. This is in agreement with recent neutron data. More

  1. Magnetic and electrical properties of epitaxial GeMn

    Energy Technology Data Exchange (ETDEWEB)

    Ahlers, Stefan

    2009-01-15

    In this work, GeMn magnetic semiconductors will be investigated. The fabrication of GeMn thin films with Mn contents up to 11.7% was realised with molecular beam epitaxy. At a fabrication temperature of 60 C, the suppression of Mn{sub x}Ge{sub y} phases could reproducibly be obtained. Dislocation free epitaxy of diamond-lattice type GeMn thin films was observed. In all fabrication conditions where Mn{sub x}Ge{sub y} suppression was feasible, an inhomogeneous dispersion of Mn was observed in form of a self-assembly of nanometre sized, Mn rich regions in a Ge rich matrix. Each Mn rich region exhibits ferromagnetic coupling with high Curie temperatures exceeding, in part, room temperature. The local ferromagnetic ordering leads to the formation of large, spatially separated magnetic moments, which induce a superparamagnetic behaviour of the GeMn thin films. At low temperatures {<=} 20 K, remanent behaviour was found to emerge. X-ray absorption experiments revealed a similarity of the Mn incorporation in diamond-lattice type GeMn thin films and in the hexagonal lattice of the intermetallic Mn{sub 5}Ge{sub 3} phase, respectively. These tetrahedra represent building blocks of the Mn{sub 5}Ge{sub 3} unit cell. The incorporation of Mn{sub 5}Ge{sub 3} building blocks was found to be accompanied by local structural disorder. The electrical properties of GeMn thin films were addressed by transport measurements. It was shown that by using a n-type Ge substrate, a pn energy barrier between epilayers and substrate to suppress parallel substrate conduction paths can be introduced. With the pn barrier concept, first results on the magnetotransport behaviour of GeMn thin films were obtained. GeMn was found to be p-type, but of high resistivity. a series of GeMn thin films was fabricated, where intermetallic Mn{sub x}Ge{sub y} phase separation was supported in a controlled manner. Phase separation was found to result in the formation of partially coherent, nanometre sized Mn{sub 5

  2. Magnetic properties of (Co, Ni, Mn3O4 spinels

    Directory of Open Access Journals (Sweden)

    Durán, P.

    2004-06-01

    Full Text Available Magnetic properties of new materials, based on the general formula CoxNiyMnzO4 (x+y+z= 3, have been investigated as a function of magnetic field and temperature. The behavior observed in the paramagnetic regime (220 K ≤ T ≤ 400 K shows a direct correlation with the nominal cation concentration. The paramagnetic-ferrimagnetic transition which takes place at T = Tc depends on the overall composition, going from Tc = 120 K (for Co0.2NiMn1.8O4 up to Tc = 210 K (for Co1.2Ni0.3Mn1.5O4. A second transition is observed at lower temperatures, corresponding to a second ordered magnetic sublattice. This second transition takes place at about 60 K (for Co0.6NiMn1.4O4, increasing with the cobalt content up to about 160 K. Under an external magnetic field, both transitions merge into a single one, with a characteristic temperature Tmax, which rapidly decreases with increasing field. Magnetization loops M(H obtained at 5 K show a typical behavior of soft magnetic materials, with low coercive fields. Low conductivity values were observed at room‑temperature, increasing by a factor of 200-1000 at high temperatures (400 C, which make these compounds to be very interesting materials for potential applications as NTCR thermistors.Se han investigado las propiedades magnéticas de materiales de fórmula CoxNiyMnzO4 (x+y+z+ = 3, en función del campo magnético aplicado y de la temperatura. El comportamiento observado en el régimen paramagnético (220 K ≤ T ≤ 400 K está en relación directa con la concentración catiónica nominal. Se observa una transición paramagnética-ferrimagnética a T = Tc, cuyo valor depende de la composición global del compuesto, variando entre Tc = 120 K (Co0.2NiMn1.8O4 y Tc = 210 K (Co1.2Ni0.3Mn1.5O4. Se ha observado una segunda transición a una temperatura inferior, relacionada con una segunda subred magnéticamente ordenada. Esta segunda transición ocurre a T = 60 K (Co0.6NiMn1.4O4, aumentando progresivamente con la

  3. Effect of Gallium Addition on Magnetic Properties of Nd2Fe14B-Based/α-Fe Nanocomposite Magnets

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The influence of Ga addition on the crystallization behavior and the magnetic properties of nanocomposite Nd2Fe14B-based/α-Fe magnets was investigated. It was found that the addition of 0.2% did not change the crystallization temperature of amorphous alloy, but the magnetic properties were improved significantly because of the strong exchange coupling interaction between the hard and soft magnetic phases. The optimum magnetic properties with iHc=600.3 kA·m-1, Br=0.75 T, and (BH)max=88.03 kJ·m-3 were obtained in bonded Nd9.5(FeCoZr)83.8Ga0.2B6.5 magnet with 15 m·s-1 wheel speed and 670 ℃ annealing treatment. The apparent improvement of magnetic properties originates from the grain refinement calculated using the Scherrer formula from corresponding XRD patterns and the excellent rectangularity of the demagnetization curve.

  4. Preparation and Magnetic Properties of Melt-Spinning Nd2Fe14B/α-Fe Nanocomposite Magnets

    Institute of Scientific and Technical Information of China (English)

    王伟; 倪建森; 徐晖; 周邦新; 李强; 王占勇

    2004-01-01

    Nd11Fe71Co8V1.5Cr1B7.5 magnet was prepared by melt-spinning and subsequently annealed. The effects of the wheel speed on the magnetic properties and microstructure were studied. The results reveal that fine nanocomposite microstructure consisting of Nd2Fe14B and α-Fe phases can be developed at an optimum wheel speed of about 21 m·s-1. After optimal annealing (640 ℃×4 min), magnetic properties of Br=0.64 T, jHc=903.5 kA·m-1 and (BH)max=71 kJ·m-3 were obtained for the bonded magnets. The addition of Cr element significantly reduces grain size, increasing the intrinsic coercivity and maximum magnetic energy product.

  5. Crystal Structure and Magnetic Studies of a New Nitronyl Nitroxide Compound

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Compound 1 was first synthesized and characterized. Its crystal structure and magnetic property were determined and investigated. Discussion about the molecule packing in crystal and the macroscopic magnetism was also presented, in combination with computing study of the spatial distribution over the molecule.

  6. Magnetic and magnetocaloric properties of amorphous Y3Fe5O12 compound

    Science.gov (United States)

    Nóbrega, E. P.; Costa, S. S.; Alvarenga, T. S. T.; Alho, B. P.; Caldas, A.; Ribeiro, P. O.; de Sousa, V. S. R.; de Oliveira, N. A.; von Ranke, P. J.

    2017-01-01

    We report a theoretical model formed by two coupled magnetic sublattices of localized spins in the presence of an applied magnetic field to investigate the magnetic characteristics and magnetocaloric properties of amorphous yttrium iron garnet. The magnetic state equation is based on Handrich-Kobe´s theory, where the amorphization is taken into account by introducing fluctuations in the exchange parameters. Experimental results report that Y3Fe5O12 presents a structural phase transition from crystalline to amorphous caused by a variation of external pressure. This phase transition on Y3Fe5O12 leads to interesting results in the magnetic properties and magnetocaloric quantities.

  7. Study of Microstructure and Magnetic Properties of Pr-Fe-B-Cu Permanent Magnets by Hot Deformation

    Institute of Scientific and Technical Information of China (English)

    陈秀云; 姜忠良; 高天明; 吴严; 杨昌平; 朱静

    2002-01-01

    The relationship between the microstructures and magnetic properties of rare earth cast permanent Pr-Fe-B-Cu alloys by hot deformation was studied. Fine and well-aligned column grains can be obtained by using a proper solidification mould with a high cooling rate. The soft magnetic phase α-Fe can be removed during proper annealing treatment. Hot pressing can produce the anisotropy and refine the grain size, so that the magnetic properties are greatly improved. The technique has the advantages of simple processing, low cost and high benefit, compared with the common sintering processing. Under the condition of the deformation temperature of 1073 K, 90% strain and strain rate of 40×10-3 s-1, the magnetic properties obtained are: Br=1.05 T, i Hc=955 kAm-1, (BH)max=207 kJ*m-3.

  8. Magnetic Property Measurements on Single Wall Carbon Nanotube-Polyimide Composites

    Science.gov (United States)

    Sun, Keun J.; Wincheski, Russell A.; Park, Cheol

    2008-01-01

    Temperature and magnetic field dependent magnetization measurements were performed on polyimide nanocomposite samples, synthesized with various weight percentages of single wall carbon nanotubes. It was found that the magnetization of the composite, normalized to the mass of nanotube material in the sample, decreased with increasing weight percentage of nanotubes. It is possible that the interfacial coupling between the carbon nanotube (CNT) fillers and the polyimide matrix promotes the diamagnetic response from CNTs and reduces the total magnetization of the composite. The coercivity of the samples, believed to originate from the residual magnetic catalyst particles, was enhanced and had a stronger temperature dependence as a result of the composite synthesis. These changes in magnetic properties can form the basis of a new approach to investigate the interfacial properties in the CNT nanocomposites through magnetic property measurements.

  9. The impact of the chemical synthesis on the magnetic properties of intermetallic PdFe nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Castellanos-Rubio, I.; Insausti, M.; Muro, I. Gil de [Universidad del País Vasco, UPV/EHU, Dpto. de Química Inorgánica (Spain); Arias-Duque, D. Carolina; Hernández-Garrido, Juan Carlos [Universidad de Cadiz, Departamento de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Facultad de Ciencias (Spain); Rojo, T.; Lezama, L., E-mail: luis.lezama@ehu.es [Universidad del País Vasco, UPV/EHU, Dpto. de Química Inorgánica (Spain)

    2015-05-15

    Palladium-rich Iron nanoparticles in the 4–8 nm range have been produced by a combination of two methods: the thermal decomposition of organometallic precursors and the reduction of metallic salts by a polyol. Herein, it is shown how the details of the synthesis have a striking impact on the magnetic and morphological properties of the final products. In the synthesis of these bimetallic nanoparticles, the use of high reaction temperatures plays an essential role in attaining good chemical homogeneity, which has proved to have a key influence on the magnetic properties. Magnetic characterization has been performed by electron magnetic resonance and magnetization measurements, which have confirmed the superparamagnetic-like behavior at room temperature. No clear traces of magnetic polarization in palladium atoms have been detected. The combination of long-term stability and homogeneous chemical and magnetic properties makes these particles very suitable for a wide range of applications in nanotechnology.

  10. Synthesis, structure, and magnetic properties of a [Mn22] wheel-like single-molecule magnet.

    Science.gov (United States)

    Murugesu, Muralee; Raftery, James; Wernsdorfer, Wolfgang; Christou, George; Brechin, Euan K

    2004-07-12

    The synthesis and magnetic properties of the compound [Mn(22)O(6)(OMe)(14)(O(2)CMe)(16)(tmp)(8)(HIm)(2)] 1 are reported. Complex 1 was prepared by treatment of [Mn(3)O(MeCO(2))(6)(HIm)(3)](MeCO(2)) (HIm = imidazole) with 1,1,1-tris(hydroxymethyl)propane (H(3)tmp) in MeOH. Complex 1.2MeOH crystallizes in the orthorhombic space group Pbca. The molecule consists of a metallic core of 2 Mn(IV), 18 Mn(III), and 2 Mn(II) ions linked by a combination of 6 micro(3)-bridging O(2)(-) ions, 14 micro(3)- and micro(2)-bridging MeO(-) ions, 16 micro-MeCO(2)(-) ligands, and 8 tmp(3)(-) ligands, which use their alkoxide arms to bridge in a variety of ways. The metal-oxygen core is best described as a wheel made from [Mn(3)O(4)] partial cubes and [Mn(3)O] triangles. Variable-temperature direct current (dc) magnetic susceptibility data were collected for complex 1 in the 1.8-300 K temperature range in a 1 T applied field. The chi(M)T value steadily decreases from 56 cm(3) K mol(-)(1) at 300 K to 48.3 cm(3) K mol(-)(1) at 30 K and then increases slightly to reach a maximum value of 48.6 cm(3) K mol(-)(1) at 15 K before dropping rapidly to 40.3 cm(3) K mol(-)(1) at 5 K. The ground-state spin of complex 1 was established by magnetization measurements in the 0.1-2.0 T and 1.80-4.00 K ranges. Fitting of the data by a matrix-diagonalization method to a model that assumes only the ground state is populated and incorporating only axial zero-field splitting (DS(z)()(2)), gave a best fit of S = 10, g = 1.96 and D = -0.10 cm(-)(1). The ac magnetization measurements performed on complex 1 in the 1.8-8 K range in a 3.5 G ac field oscillating at 50-1000 Hz showed frequency-dependent ac susceptibility signals below 3 K. Single-crystal hysteresis loop and relaxation measurements indicate loops whose coercivities are strongly temperature and time dependent, increasing with decreasing temperature and increasing field sweep rate, as expected for the superparamagnetic-like behavior of a single

  11. Physical, Thermal, Magnetic and Mechanical Properties of ARAA

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Y. B.; Lee, D. W. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Rhee, C. K. [National Fusion Research Institute, Daejeon, (Korea, Republic of)

    2015-10-15

    The mechanical properties of total ninety-eight model alloys designed for application to HCCR TBM in the ITER were evaluated. The addition of small amounts of Zr was found to have positive effects on creep and impact resistance, based on which Zr-containing reduced activation ferritic-martensitic steel, ARAA, has been developed. A 5-ton scale ARAA was produced via VIM and ESR methods and its basic properties required for fusion reactor applications were evaluated. It is found that the physical, thermal, magnetic and mechanical properties of ARAA are comparable to those of Eurofer 97. Reduced activation ferritic-martensitic (RAFM) steel is considered a primary candidate for the structural material in a fusion reactor, owing to its good swelling resistance and compatibility with various coolants. Several types of RAFM steels showing good performance have been developed, which include the European Eurofer 97 and the Japanese F82H. For these alloys, an extensive materials database is available. The structural materials for the blanket system is expected to be subjected to high heat-load and operate under high-energy (14 MeV) and high-fluence fusion neutron irradiation. The operational range of temperature for a blanket is limited by the high-temperature creep and low-temperature irradiation embrittlement of the structural material. RAFM steels developed thus far are known to be operable at 350-550 .deg. C. To expand the temperature window and thereby allow for various design options, it is important to develop alloys that are able to withstand high temperature and high-energy neutron irradiation.

  12. Effects of gadolinium and silicon substitution on magnetic properties and microstructure of Nd–Fe–B–Nb bulk nanocomposite magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Zubair [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Yan, Mi, E-mail: mse_yanmi@zju.edu.cn [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Tao, Shan [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China); Husain, S. Wilayat [Department of Materials Science and Engineering, Institute of Space Technology, Islamabad (Pakistan); Liu, Zhongwu [School of Materials Science and Engineering, South China, University of Technology, Guangzhou 510640 (China)

    2015-03-15

    The magnetic properties, phase evolution and microstructure of Fe{sub 70−x}M{sub x}B{sub 19}Nd{sub 7}Nb{sub 4} (M=Si, Gd, Si+Gd; x=0–2.5 at%) bulk nanocomposite permanent magnets in the form of rods produced by annealing the amorphous precursor have been investigated systematically. Microstructural examination, three-dimensional atom probe microanalysis, δM-plots, X-ray diffraction analysis and magnetometer studies deduced that good magnetic properties in the magnets originate from the homogenous microstructure consisting of exchange coupled, soft magnetic (α-Fe, Fe{sub 3}B) and hard magnetic (Nd,Gd){sub 2}Fe{sub 14}B nanophases. Optimally annealed Fe{sub 70}B{sub 19}Nd{sub 7}Nb{sub 4} rod magnets exhibit magnetic properties of B{sub r}=0.61 T, {sub i}H{sub c}=876 kA/m and (BH){sub max}=50.2 kJ/m{sup 3}. Gadolinium and silicon addition to quaternary Fe{sub 70}B{sub 19}Nd{sub 7}Nb{sub 4} alloy increased the mass fraction of hard magnetic phase, strengthened the exchange coupling interactions and enhanced the magnetic properties. Gadolinium and silicon segregated into hard magnetic phase which led to enhance coercivity up to 1115 kA/m. Enhancement in the coercivity is mainly resulted by hard phase increment as well as domain wall pinning, while strengthening of exchange coupling is caused by grain size refinement and increase in Curie temperature of the magnetic phases. The Fe{sub 67}B{sub 19}Nd{sub 7}Gd{sub 2}Nb{sub 4}Si{sub 1} magnetic rods of 1.2 mm in diameter demonstrated the best magnetic properties such as intrinsic coercivity, {sub i}H{sub c} of 1115 kA/m, remanence, B{sub r} of 0.57 T and maximum energy product, (BH){sub max} of 65.7 kJ/m{sup 3}. - Highlights: • Magnetic and microstructural properties of Fe{sub 70−x}M{sub x}B{sub 19}Nd{sub 7}Nb{sub 4} (M=Si, Gd, Si+Gd; x=0–2.5 at%) magnets are studied. • Amorphous rods of 1.2 mm in diameter are synthesized by injection casting. • Magnetic properties are improved by substitution of Gd and Si

  13. Endowing carbon nanotubes with superparamagnetic properties: applications for cell labeling, MRI cell tracking and magnetic manipulations.

    Science.gov (United States)

    Lamanna, Giuseppe; Garofalo, Antonio; Popa, Gabriela; Wilhelm, Claire; Bégin-Colin, Sylvie; Felder-Flesch, Delphine; Bianco, Alberto; Gazeau, Florence; Ménard-Moyon, Cécilia

    2013-05-21

    Coating of carbon nanotubes (CNTs) with magnetic nanoparticles (NPs) imparts novel magnetic, optical, and thermal properties with potential applications in the biomedical domain. Multi-walled CNTs have been decorated with iron oxide superparamagnetic NPs. Two different approaches have been investigated based on ligand exchange or "click chemistry". The presence of the NPs on the nanotube surface allows conferring magnetic properties to CNTs. We have evaluated the potential of the NP/CNT hybrids as a contrast agent for magnetic resonance imaging (MRI) and their interactions with cells. The capacity of the hybrids to magnetically monitor and manipulate cells has also been investigated. The NP/CNTs can be manipulated by a remote magnetic field with enhanced contrast in MRI. They are internalized into tumor cells without showing cytotoxicity. The labeled cells can be magnetically manipulated as they display magnetic mobility and are detected at a single cell level through high resolution MRI.

  14. Effects of wear on structure-sensitive magnetic properties of ceramic ferrite in contact with magnetic tape

    Science.gov (United States)

    Miyoshi, K.; Buckley, D. H.; Tanaka, K.

    1985-01-01

    Wear experiments and electron microscopy and diffraction studies were conducted to examine the wear and deformed layers in single-crystal Mn-Zn (ceramic) ferrite magnetic head material in contact with magnetic tape and the effects of that contact on magnetic properties. The crystalline state of the single-crystal magnetic head was changed drastically during the sliding process. A nearly amorphous structure was produced on its wear surface. Deformation in the surficial layer of the magnetic head was a critical factor in readback signal loss above 2.5 dB. The signal output level was reduced as applied normal load was increased. Considerable plastic flow occurred on the magnetic tape surface with sliding, and the signal loss due to the tape wear was approximately 1 dB.

  15. Monte Carlo simulation of magnetic properties of a nano-graphene bilayer in a longitudinal magnetic field

    Science.gov (United States)

    Wang, Wei; Liu, Ruijia; Lv, Dan; Luo, Xiaohong

    2016-10-01

    Monte Carlo simulation has been used to study the magnetic properties of a nano-graphene bilayer which consists of the upper layer A with spin-3/2 and the bottom layer B with spin-5/2. The effects of the single-ion anisotropy, the intralayer exchange coupling and the longitudinal magnetic field on the magnetization, the susceptibility, the blocking temperature and hysteresis loops of the mixed-spin nano-graphene bilayer system have been examined detailedly. In particular, the variations of the blocking temperature with different intralayer exchange couplings, single-ion anisotropies, and the longitudinal magnetic field are obtained for the present system. Many multiple hysteresis loop behaviors have also been found, depending on the combinations of both the upper and bottom layer magnetizations in the longitudinal magnetic field. Through a comparison, our results obtained are according well with other theoretical researches and experimental results.

  16. The influence of the textural development on magnetic properties in Co-Cr thin films

    NARCIS (Netherlands)

    Li, Cheng-Zhang; Lodder, J.C.; Szpunar, J.A.

    1994-01-01

    Two series Co81Cr19 films (5-980 nm) were chosen to investigate the influence of textural development on magnetic properties. It was demonstrated that both the texture and the magnetic properties strongly depend on the film thickness. In the thickness range from 12 to 980 nm, the coercivity Hc and t

  17. Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow

    NARCIS (Netherlands)

    de Groot, L.V.|info:eu-repo/dai/nl/314839178; Dekkers, M.J.|info:eu-repo/dai/nl/073463744; Visscher, M.; ter Maat, G.W.

    2014-01-01

    The outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties, we sampled a vertical transect in a ∼6 m thick inflated lava flow at Hawaii, emplaced in ∼588 AD. Its

  18. Magnetic properties and paleointensities as function of depth in a Hawaiian lava flow

    NARCIS (Netherlands)

    de Groot, L.V.; Dekkers, M.J.; Visscher, M.; ter Maat, G.W.

    2014-01-01

    The outcome of paleointensity experiments largely depends on the rock-magnetic properties of the samples. To assess the relation between volcanic emplacement processes and rock-magnetic properties, we sampled a vertical transect in a ∼6 m thick inflated lava flow at Hawaii, emplaced in ∼588 AD. Its

  19. The numerical investigation of magnetic properties of single domain MnP:GaP nanoparticles

    Science.gov (United States)

    Gerami, Adeleh Mokhles; Vaez-Zadeh, Mehdi

    2016-03-01

    The magnetic properties of MnP:GaP nanoparticles are calculated using a statistical mechanical approach and effect of various factors on magnetization of nanoparticles is studied. The calculation is based on solution of localized partition function and evolution of magnetic moment affected by thermal fluctuation and external field is included by solving master equation. Instead of constant magnetic saturation approximation, a temperature dependent magnetic moment saturation is included to improve calculation efficiency for larger nanoparticles. In the present work, the field-cooled and zero-field-cooled (FC/ZFC) magnetization of randomly oriented anisotropy and log-normal volume distributed nanoparticles are calculated.

  20. Magnetic properties of Ni/Au core/shell studied by Monte Carlo simulations

    Energy Technology Data Exchange (ETDEWEB)

    Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi Bouzid, Safi, 63 4600 (Morocco); LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Bahmad, L. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculté des Sciences, Université Mohammed V-Agdal, Av. Ibn Batouta, B.P. 1014, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble cedex 9 (France)

    2014-01-10

    The magnetic properties of ferromagnetic Ni/Au core/shell have been studied using Monte Carlo simulations within the Ising model framework. The considered Hamiltonian includes the exchange interactions between Ni–Ni, Au–Au and Ni–Au and the external magnetic field. The thermal total magnetizations and total magnetic susceptibilities of core/shell Ni/Au are computed. The critical temperature is deduced. The exchange interaction between Ni and Au atoms is obtained. In addition, the total magnetizations versus the external magnetic field and crystal filed for different temperature are also established.