Magnetostatic wave tunable resonators
Castera, J.-P.; Hartemann, P.
1983-06-01
Theoretical principles and techniques for the implementation of magnetostatic surface wave and volume wave resonators in high frequency oscillators are discussed. Magnetostatic waves are magnetic waves that propagate in materials exposed to a polarized magnetic field. The propagation speed ranges from 3-300 km/sec for wavelengths between 1 micron and 10 mm, in the presence of lags from 10-1000 nsec/ cm. Tunable resonators in the 1-20 GHz frequency range have been manufactured with YIG using liquid phase epitaxy for deposition on gadolinium and gallium substrates. Distributed-mirror Fabry-Perot cavity resonators are described and performance tests results are reported, including losses of 8 dB, a quality coefficient under voltage of 450, and frequency rejection outside of resonance better than 10 dB. However, saturation occurs at low power levels at frequencies lower than 4.2 GHz, a feature overcome with forward volume magnetostatic wave generators, which have a quality factor of 500, an insertion loss of 22 dB, and rejection around 15 dB.
Methods for magnetostatic field calculation
International Nuclear Information System (INIS)
Vorozhtsov, S.B.
1984-01-01
Two methods for magnetostatic field calculation: differential and integrat are considered. Both approaches are shown to have certain merits and drawbacks, choice of the method depend on the type of the solved problem. An opportunity of combination of these tWo methods in one algorithm (hybrid method) is considered
Combined algorithms in nonlinear problems of magnetostatics
International Nuclear Information System (INIS)
Gregus, M.; Khoromskij, B.N.; Mazurkevich, G.E.; Zhidkov, E.P.
1988-01-01
To solve boundary problems of magnetostatics in unbounded two- and three-dimensional regions, we construct combined algorithms based on a combination of the method of boundary integral equations with the grid methods. We study the question of substantiation of the combined method of nonlinear magnetostatic problem without the preliminary discretization of equations and give some results on the convergence of iterative processes that arise in non-linear cases. We also discuss economical iterative processes and algorithms that solve boundary integral equations on certain surfaces. Finally, examples of numerical solutions of magnetostatic problems that arose when modelling the fields of electrophysical installations are given too. 14 refs.; 2 figs.; 1 tab
Magnetostatics of the uniformly polarized torus
DEFF Research Database (Denmark)
Beleggia, Marco; De Graef, Marc; Millev, Yonko
2009-01-01
We provide an exhaustive description of the magnetostatics of the uniformly polarized torus and its derivative self-intersecting (spindle) shapes. In the process, two complementary approaches have been implemented, position-space analysis of the Laplace equation with inhomogeneous boundary condit...
Magnetostatic excitations in thin ferrite films
International Nuclear Information System (INIS)
Zil'berman, P.E.; Lugovskoi, A.V.
1987-01-01
The authors discuss the influence of the exchange interaction and dissipative processes in thin ferrite films on the eigenfrequency spectrum of magnetostatic standing waves and on the dispersion relation and attenuation of magnetostatic traveling waves. For the first time they obtain explicitly the dispersion relation for magnetostatic waves (MSWs) in a tangential saturating magnetic field H 0 to second order (inclusive) in the exchange interaction parameter λ. The authors obtain computer solutions for this equation in the complex frequency (ω) plane (for standing waves) or wave-number (q) plane (for traveling waves). The authors show that the dispersion relation constructed from the standing-wave spectrum is different from that of the traveling waves if λ≠0, even if dissipation is neglected. The traveling waves have auxiliary branches of the dispersion relation with weak damping near the spin-wave-resonance (SWR) frequencies. Dissipation has only a relatively weak effect on the frequency spectrum of the standing waves, shifting it upward. For the traveling waves, however, dissipation leads to qualitative changes in the structure of the dispersion relation, giving rise to new branches, forbidden bands, reentrant and anomalous-dispersion regions
On the Basic Equations of the Magnetostatics
Directory of Open Access Journals (Sweden)
A. M. Makarov
2016-01-01
Full Text Available The paper studies the physical relationship between the main objects of the magnetic field in a continuous medium with magnetization effects. Consistently considers the following hypotheses: a hypothesis of the primacy and the physical reality of the magnetization vector field environment, a similar hypothesis about the real existence of Ampere currents (molecular currents, magnetization currents, a hypothesis of a magnetic dipole moment of the medium volume element in view of bulk density of electric currents in this volume. A more rigorous derivation of the basic differential equations of magnetostatics from the Biot-Savart-Laplace equation is proposed.The well-known works justifying basic equations of magnetostatics use a procedure wherein when proving the local differential ratio is used a transformation of some volume integral to the surface integral bounding this volume. Thus, there is a specific way to select a closed surface that is either a surface in a vacuum (beyond the medium volume under consideration, or a surface of the conductor (a normal component of currents to the surface, here, becomes zero. In the paper the control surface is arbitrarily carried out within the volume of the medium under consideration, thereby leading to the mathematically sound result.The paper analyzes the hypotheses listed above. The main feature of analysis is a succesively using concept of bilateralism surface bounding the medium volume of the arbitrary finite dimensions. The analysis allowed us to reveal the physical adequacy of the considered hypotheses, derive the appropriate differential equations for the basic vector fields of magnetostatics and obtain a new condition. The resulting condition for the closedness of magnetization currents is recorded in entire compliance with the well-known Gauss electrostatic law, which avoids the need for additional, but not always reasonable assumptions.
The chronicle of the electro-magnetostatic
International Nuclear Information System (INIS)
Bassalo, J.M.F.
1983-01-01
The Chronicle of the electro-magnetostatic is shown, since the first observation made by Tales de Mileto, in the VI centry B.C., about the magnetic and electric phenomenons, up to the mathematical learning of the electrical circuits, made by Kirchhoff, almost in the first half of the XIX century. In run away of this chronicle, the experimental laws involving the behavior of the electrical charge, in the insulators and in the conductors, are presented as well as the piezo and piro-electrical and chemical effects the electrical charge incite in some substances. (Author) [pt
Magnetostatic atmospheres with variations in three dimensions
International Nuclear Information System (INIS)
Low, B.C.
1982-01-01
The paper treats the static equilibrium of a fully ionized atmosphere with an embedded magnetic field in the presence of a uniform gravity. The magnetic field lines are assumed to lie in parallel vertical planes, taken to be perpendicular to the x-axis in Cartesian coordinates. Except for this assumption, the system is allowed to vary in all three dimensions. The theoretical investigation reported here is a departure from previous studies of magnetostatics which have been limited by mathematical tractability to symmetric or two-dimensional systems. The class of three-dimensional equilibria considered are characterized by the sum of plasma and magnetic pressures being invariant in the x-direction. A nonlinear second-order hyperbolic partial differential equation having y and z as independent variables, is shown to be a necessary condition on the magnetic surfaces for an equilibrium state to exist. This is a physical condition not encountered in symmetric equilibria described with an ignorable coordinate. The special case of the total pressure varying only with height is soluble analytically and selected explicit solutions are presented to illustrate various structural properties of prominence-like density enhancements, coronal magnetic arcades, and discrete bipolar plasma loops. There is considerable interest in the equilibrium and stability of plasma loops in the solar corona. This paper presents for the first time, explicit equilibrium solutions for plasma loops with three-dimensional extensions. Of particular interest is that the loop solutions presented include simple examples which can be shown to be stable under isothermal conditions
Birkeland currents in an anisotropic, magnetostatic plasma
International Nuclear Information System (INIS)
Birmingham, T.J.
1992-01-01
An expression for the parallel current density is derived for a plasma characterized by negligible bulk flow (magnetostatic) velocity and a two-component (anisotropic) pressure tensor by expanding the equilibrium Vlasov equation for each species in the adiabatic parameter until such point as a nonvanishing moment j parallel = ∫ d 3 vv parallel is identified. The result is a nonlocal one: it relates j parallel at one point s along a field line to j parallel at another (reference) point s 0 plus an integral function of the pressure and magnetic field between them. It is a generalization and elaboration of results obtained by Bostrom (1975), Heinemann (1990), and Heinemann and Pontius (1991). The expression could have been obtained by integrating the current continuity equation with -∇ x j perpendicular as a source term and j perpendicular given by perpendicular momentum balance. The authors explicitly show the equivalency. The widely used Vasyliunas (1970) equation follows when P perpendicular is set equal to P parallel and s and s 0 are taken to be at the ionosphere and the equator. An extended discussion of the relationship of results derived here to others in the literature is carried out in an effort to bring unity and perspective to this problem area
Magnetostatic modes in ferromagnetic samples with inhomogeneous internal fields
Arias, Rodrigo
2015-03-01
Magnetostatic modes in ferromagnetic samples are very well characterized and understood in samples with uniform internal magnetic fields. More recently interest has shifted to the study of magnetization modes in ferromagnetic samples with inhomogeneous internal fields. The present work shows that under the magnetostatic approximation and for samples of arbitrary shape and/or arbitrary inhomogeneous internal magnetic fields the modes can be classified as elliptic or hyperbolic, and their associated frequency spectrum can be delimited. This results from the analysis of the character of the second order partial differential equation for the magnetostatic potential under these general conditions. In general, a sample with an inhomogeneous internal field and at a given frequency, may have regions of elliptic and hyperbolic character separated by a boundary. In the elliptic regions the magnetostatic modes have a smooth monotonic character (generally decaying form the surfaces (a ``tunneling'' behavior)) and in hyperbolic regions an oscillatory wave-like character. A simple local criterion distinguishes hyperbolic from elliptic regions: the sign of a susceptibility parameter. This study shows that one may control to some extent magnetostatic modes via external fields or geometry. R.E.A. acknowledges Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia under Project No. FB 0807 (Chile), Grant No. ICM P10-061-F by Fondo de Innovacion para la Competitividad-MINECON, and Proyecto Fondecyt 1130192.
Practical design of magnetostatic structure using numerical simulation
Wang, Qiuliang
2013-01-01
Covers the practical numerical method for the analysis and design of magnets Extensively covers the magnet design and computation aspects from theories to practical applications, emphasizing design methods of practical structures such as superconducting, electromagnetic and permanent magnet for use in various scientific instruments, industrial processing, biomedicine and special electrical equipments. The computations cover a wide range of numerical techniques and analytical derivation to efficiently provide solutions to complicated problems that are often encountered in practice, where simple analytical calculations are no longer adequate. Chapters include: Introduction of Magnet Technology, Magnetostatic Equation for the Magnet Structure, Finite Element Analysis for Magnetostatic Field, Integral Method for Magnetostatic Field, Numerical Method of Solenoid Coils Design, Series Analysis of Axially Symmetric Magnetic Field, Magnets with High Magnetic Field and High Homogeneity, Permanent Magnet and its App...
Planar Hall effect sensor with magnetostatic compensation layer
DEFF Research Database (Denmark)
Dalslet, Bjarke Thomas; Donolato, Marco; Hansen, Mikkel Fougt
2012-01-01
Demagnetization effects in cross-shaped planar Hall effect sensors cause inhomogeneous film magnetization and a hysteretic sensor response. Furthermore, when using sensors for detection of magnetic beads, the magnetostatic field from the sensor edges attracts and holds magnetic beads near...... the sensor edges causing inhomogeneous and non-specific binding of the beads. We show theoretically that adding a compensation magnetic stack beneath the sensor stack and exchange-biasing it antiparallel to the sensor stack, the magnetostatic field is minimized. We show experimentally that the compensation...... stack removes nonlinear effects from the sensor response, it strongly reduces hysteresis, and it increases the homogeneity of the bead distribution. Finally, it reduces the non-specific binding due to magnetostatic fields allowing us to completely remove beads from the compensated sensor using a water...
On the magnetostatics of chains of magnetic nanoparticles
DEFF Research Database (Denmark)
Phatak, C.; Pokharel, R.; Beleggia, Marco
2011-01-01
A novel approach is presented for the computation of the magnetostatic energy of straight and bent chains of identical, uniformly magnetized particles of arbitrary shape. The formalism relies on the concept of the magnetometric tensor field, and allows for closed form expressions for the magnetos...
Magnetostatic interactions and forces between cylindrical permanent magnets
Czech Academy of Sciences Publication Activity Database
Vokoun, David; Beleggia, M.; Heller, Luděk; Šittner, Petr
2009-01-01
Roč. 321, č. 22 (2009), s. 3758-3763 ISSN 0304-8853 EU Projects: European Commission(XE) 46559 - CERINKA Institutional research plan: CEZ:AV0Z10100520 Keywords : cylinder * force measurement * magnetostatic * permanent magnet Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.204, year: 2009
A three-dimensional magnetostatics computer code for insertion devices
International Nuclear Information System (INIS)
Chubar, O.; Elleaume, P.; Chavanne, J.
1998-01-01
RADIA is a three-dimensional magnetostatics computer code optimized for the design of undulators and wigglers. It solves boundary magnetostatics problems with magnetized and current-carrying volumes using the boundary integral approach. The magnetized volumes can be arbitrary polyhedrons with non-linear (iron) or linear anisotropic (permanent magnet) characteristics. The current-carrying elements can be straight or curved blocks with rectangular cross sections. Boundary conditions are simulated by the technique of mirroring. Analytical formulae used for the computation of the field produced by a magnetized volume of a polyhedron shape are detailed. The RADIA code is written in object-oriented C++ and interfaced to Mathematica (Mathematica is a registered trademark of Wolfram Research, Inc.). The code outperforms currently available finite-element packages with respect to the CPU time of the solver and accuracy of the field integral estimations. An application of the code to the case of a wedge-pole undulator is presented
The inverse problem of the magnetostatic nondestructive testing
International Nuclear Information System (INIS)
Pechenkov, A.N.; Shcherbinin, V.E.
2006-01-01
The inverse problem of magnetostatic nondestructive testing consists in the calculation of the shape and magnetic characteristics of a flaw in a uniform magnetized body with measurement of static magnetic field beyond the body. If the flaw does not contain any magnetic material, the inverse problem is reduced to identification of the shape and magnetic susceptibility of the substance. This case has been considered in the study [ru
Transformation magneto-statics and illusions for magnets
Sun, Fei; He, Sailing
2014-10-01
Based on the form-invariant of Maxwell's equations under coordinate transformations, we extend the theory of transformation optics to transformation magneto-statics, which can design magnets through coordinate transformations. Some novel DC magnetic field illusions created by magnets (e.g. rescaling magnets, cancelling magnets and overlapping magnets) are designed and verified by numerical simulations. Our research will open a new door to designing magnets and controlling DC magnetic fields.
Contribution to the resolution of magnetohydrodynamic and magnetostatic equations
International Nuclear Information System (INIS)
Boulbe, C.
2007-10-01
Interaction between a plasma and a magnetic field appears and has an important role in various domains such as thermonuclear fusion by magnetic confinement or astrophysical plasmas for example. In evolution, these interactions are described by the equations of magnetohydrodynamics (MHD). At equilibrium, the MHD equations result in the magnetostatic equations involving the magnetic field and the kinetic pressure of the plasma. The magnetostatic equations form a system of 3-dimensional non linear partial differential equations involving a magnetic field and a kinetic plasma pressure. When the pressure is supposed negligible, the magnetic field is known as Beltrami field. In a first time, we propose to solve numerically the Beltrami field problem using a fixed point iterative algorithm associated with finite element methods. This iterative strategy is extended in a second time to the computation of magnetostatic configurations with pressure. In the sequel, we interest in the approximation of ideal MHD equations. This system forms a nonlinear hyperbolic conservation law. We propose to use a finite volume approach, in which fluxes are calculated by a Roe's method on a tetrahedral mesh. Fluxes of the magnetic field are modified in order to satisfy the constraint of divergence free imposed on it. The proposed methods have been implemented in two new 3-dimensional codes called TETRAFFF for equilibrium, and TETRAMHD for MHD. The obtained numerical results confirm the high performance of these methods. (author)
Using a micromachined magnetostatic relay in commutating a DC motor
Tai, Yu-Chong (Inventor); Wright, John A. (Inventor); Lilienthal, Gerald (Inventor)
2004-01-01
A DC motor is commutated by rotating a magnetic rotor to induce a magnetic field in at least one magnetostatic relay in the motor. Each relay is activated in response to the magnetic field to deliver power to at least one corresponding winding connected to the relay. In some cases, each relay delivers power first through a corresponding primary winding and then through a corresponding secondary winding to a common node. Specific examples include a four-pole, three-phase motor in which each relay is activated four times during one rotation of the magnetic rotor.
Superstrong coupling of thin film magnetostatic waves with microwave cavity
Energy Technology Data Exchange (ETDEWEB)
Zhang, Xufeng; Tang, Hong X., E-mail: hong.tang@yale.edu [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States); Zou, Changling [Department of Electrical Engineering, Yale University, New Haven, Connecticut 06511 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States); Jiang, Liang [Department of Applied Physics, Yale University, New Haven, Connecticut 06511 (United States)
2016-01-14
We experimentally demonstrated the strong coupling between a microwave cavity and standing magnetostatic magnon modes in a yttrium iron garnet film. Such strong coupling can be observed for various spin wave modes under different magnetic field bias configurations, with a coupling strength inversely proportional to the transverse mode number. A comb-like spectrum can be obtained from these high order modes. The collectively enhanced magnon-microwave photon coupling strength is comparable with the magnon free spectral range and therefore leads to the superstrong coupling regime. Our findings pave the road towards designing a new type of strongly hybridized magnon-photon system.
Iterative algorithm for the volume integral method for magnetostatics problems
International Nuclear Information System (INIS)
Pasciak, J.E.
1980-11-01
Volume integral methods for solving nonlinear magnetostatics problems are considered in this paper. The integral method is discretized by a Galerkin technique. Estimates are given which show that the linearized problems are well conditioned and hence easily solved using iterative techniques. Comparisons of iterative algorithms with the elimination method of GFUN3D shows that the iterative method gives an order of magnitude improvement in computational time as well as memory requirements for large problems. Computational experiments for a test problem as well as a double layer dipole magnet are given. Error estimates for the linearized problem are also derived
Effects of metal and 'magnetic wall' on the dispersion characteristic of magnetostatic waves
International Nuclear Information System (INIS)
Lock, Edwin H.; Vashkovsky, Anatoly V.
2006-01-01
The dispersion relation of magnetostatic waves tangentially magnetized to saturation ferrite film, with a 'magnetic wall' condition (tangential component of microwave magnetic field is equal to zero) on one of the film surface and with a metal condition on the opposite surface is analyzed. The dispersion characteristics show that unidirectional magnetostatic waves appear in this structure: they can transfer energy in one direction only and fundamentally cannot transfer energy in the opposite direction. The dispersion-free propagation of magnetostatic waves also is possible in the structure in a wide frequency interval
Precise magnetostatic field using the finite element method
International Nuclear Information System (INIS)
Nascimento, Francisco Rogerio Teixeira do
2013-01-01
The main objective of this work is to simulate electromagnetic fields using the Finite Element Method. Even in the easiest case of electrostatic and magnetostatic numerical simulation some problems appear when the nodal finite element is used. It is difficult to model vector fields with scalar functions mainly in non-homogeneous materials. With the aim to solve these problems two types of techniques are tried: the adaptive remeshing using nodal elements and the edge finite element that ensure the continuity of tangential components. Some numerical analysis of simple electromagnetic problems with homogeneous and non-homogeneous materials are performed using first, the adaptive remeshing based in various error indicators and second, the numerical solution of waveguides using edge finite element. (author)
Lowest order Virtual Element approximation of magnetostatic problems
Beirão da Veiga, L.; Brezzi, F.; Dassi, F.; Marini, L. D.; Russo, A.
2018-04-01
We give here a simplified presentation of the lowest order Serendipity Virtual Element method, and show its use for the numerical solution of linear magneto-static problems in three dimensions. The method can be applied to very general decompositions of the computational domain (as is natural for Virtual Element Methods) and uses as unknowns the (constant) tangential component of the magnetic field $\\mathbf{H}$ on each edge, and the vertex values of the Lagrange multiplier $p$ (used to enforce the solenoidality of the magnetic induction $\\mathbf{B}=\\mu\\mathbf{H}$). In this respect the method can be seen as the natural generalization of the lowest order Edge Finite Element Method (the so-called "first kind N\\'ed\\'elec" elements) to polyhedra of almost arbitrary shape, and as we show on some numerical examples it exhibits very good accuracy (for being a lowest order element) and excellent robustness with respect to distortions.
Magnetostatic Analysis of a Pinch Mode Magnetorheological Valve
Directory of Open Access Journals (Sweden)
Gołdasz Janusz
2017-09-01
Full Text Available The study deals with the pinch mode of magnetorheological (MR fluids’ operation and its application in MR valves. By applying the principle in MR valves a highly non-uniform magnetic field can be generated in flow channels in such a way to solidify the portion of the material that is the nearest to the flow channel’s walls. This is in contrary to well-known MR flow mode valves. The authors investigate a basic pinch mode valve in several fundamental configurations, and then examine their magnetic circuits through magnetostatic finite-element (FE analysis. Flux density contour maps are revealed and basic performance figures calculated and analysed. The FE analysis results yield confidence in that the performance of MR pinch mode devices can be effectively controlled through electromagnetic means.
Energy Technology Data Exchange (ETDEWEB)
Ferraro, Rafael, E-mail: ferraro@iafe.uba.a [Instituto de AstronomIa y Fisica del Espacio, Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina); Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina)
2010-05-14
In Born-Infeld theory and other nonlinear electrodynamics, the presence of a magnetostatic field modifies the dispersion relation and the energy velocity of waves propagating in a hollow waveguide. As a consequence, the transmitted power along a waveguide suffers slight changes when a magnetostatic field is switched on and off. This tiny effect could be better tested by operating the waveguide at a frequency close to the cutoff frequency.
International Nuclear Information System (INIS)
Ferraro, Rafael
2010-01-01
In Born-Infeld theory and other nonlinear electrodynamics, the presence of a magnetostatic field modifies the dispersion relation and the energy velocity of waves propagating in a hollow waveguide. As a consequence, the transmitted power along a waveguide suffers slight changes when a magnetostatic field is switched on and off. This tiny effect could be better tested by operating the waveguide at a frequency close to the cutoff frequency.
Reformulation of nonlinear integral magnetostatic equations for rapid iterative convergence
International Nuclear Information System (INIS)
Bloomberg, D.S.; Castelli, V.
1985-01-01
The integral equations of magnetostatics, conventionally given in terms of the field variables M and H, are reformulated with M and B. Stability criteria and convergence rates of the eigenvectors of the linear iteration matrices are evaluated. The relaxation factor β in the MH approach varies inversely with permeability μ, and nonlinear problems with high permeability converge slowly. In contrast, MB iteration is stable for β 3 , the number of iterations is reduced by two orders of magnitude over the conventional method, and at higher permeabilities the reduction is proportionally greater. The dependence of MB convergence rate on β, degree of saturation, element aspect ratio, and problem size is found numerically. An analytical result for the MB convergence rate for small nonlinear problems is found to be accurate for βless than or equal to1.2. The results are generally valid for two- and three-dimensional integral methods and are independent of the particular discretization procedures used to compute the field matrix
Multipolar ordering in electro- and magnetostatic coupled nanosystems.
Vedmedenko, Elena Y; Mikuszeit, Nikolai
2008-06-23
Electric and magnetic multipole moments and polarizabilities are important quantities in studies of intermolecular forces, non-linear optical phenomena, electrostatic, magnetostatic or gravitational potentials and electron scattering. The experimental determination of multipole moments is difficult and therefore the theoretical prediction of these quantities is important. Depending on purposes of the investigation several different definitions of multipole moments and multipole-multipole interactions are used in the literature. Because of this variety of methods it is often difficult to use published results and, therefore, even more new definitions appear. The first goal of this review is to give an overview of mathematical definitions of multipole expansion and relations between different formulations. The second aim is to present a general theoretical description of multipolar ordering on periodic two-dimensional lattices. After a historical introduction in the first part of this manuscript the static multipole expansion in cartesian and spherical coordinates as well as existing coordinate transformations are reviewed. On the basis of the presented mathematical description multipole moments of several symmetric charge distributions are summarized. Next, the established numerical approach for the calculation of multipolar ground states, namely Monte Carlo simulations, are reviewed. Special emphasis is put on the review of ground states in multipolar systems consisting of moments of odd or even order. The last section is devoted to the magnetization reversal in dense packed nanomagnetic arrays, where the magnetic multipole-multipole interactions play an important role. Comparison between the theory and recent experimental results is given.
Magnetostatic interactions in a natural magnetite-ulvospinel intergrowth system
Evans, M. E.; Krasa, D.; Williams, W.; Winklhofer, M.
2005-12-01
The difficult problem of magnetostatic interactions in naturally-occurring minerals has a long history but a renewed attack on it is currently being driven by recent advances in instrumentation and computing power. We report a new investigation of a finely exsolved magnetite/ulvöspinel intergrowth first studied magnetically by Evans & Wayman (1974) and more recently by Harrison et al. (2002). Transmission electron micrographs reveal a rectilinear pattern of tiny magnetite blocks separated by ulvöspinel sheets. The magnetite blocks have a gaussian size distribution with mean and standard deviation of 193 and 46 nm, respectively (n ~ 500), with the separation between nearest neighbours being typically 40 nm, but often much less. Thermomagnetic analysis yields a well-defined Curie point of 548°C indicating that the ``magnetite" actually has a compostion of Fe2.9Ti0.1O4. Routine hysteresis measurements immediately reflect the interaction between neighbouring ``magnetite" regions, with Mrs/Ms = 0.22, well below the expected value for non-interacting single-domain particles. The corresponding FORC diagram clearly reveals the interaction fields with Hi = 30 mT (full-width at half-maximum, FWHM) centred on a well-defined Hc peak at 20 mT. Furthermore, the maximum interaction field observed (~50 mT) agrees well with that expected from simple theory and micromagnetic calculations. Elimination of the intergrowth structure by heating in an evacuated quartz vial for 2 hours at 1000 °C leads to marked changes in the magnetic properties: Mrs/Ms drops to 0.11, Hcr/Hc increases from 1.98 to 2.73, the main peak on the FORC diagram shifts to 6 mT and the interaction field profile drastically narrows (FWHM Hi = 14 mT).
Velikanova, Yu. V.; Vinogradova, M. R.; Mitlina, L. A.
2018-06-01
The amplitude-frequency characteristics (AFCs) of magnetostatic waves in the films of magnesium-manganese ferrospinels with nanostructured inhomogeneities are discussed. A common effect, observed in the film AFCs under different process conditions, is the `oscillations of propagation' of magnetostatic waves as a function of the frequency. The oscillation pattern is thought to depend on the inhomogeneous exchange parameters and the surface anisotropy constants. The wave instability is characterized by the resonant interaction of the dipole magnetostatic waves with the surface spin waves. It is shown that the ferrospinel films with periodic nanostructured inhomogeneities of 30-40 nm could be treated as magnon crystals. An inclusion of the inhomogeneity into consideration allows one to provide reasoning for the formation of the rejection bands within the range 9-12 GHz, whose frequencies correspond to Bragg frequencies.
International Nuclear Information System (INIS)
Vashkovsky, Anatolii V; Lock, Edwin H
2011-01-01
The energy and dispersion characteristics of a dipole spin wave in a ferrite-dielectric-metal structure are calculated. An analysis of spin wave dispersion characteristics with extreme points demonstrates how fundamental relationships among the propagation constant, phase and group velocities, Poynting vector, and power flux manifest themselves when the wavenumber changes near these points. A comparison of magnetostatic approximation results with calculations using Maxwell's equations shows the inadequacy of the magnetostatic approximation formulas currently used for calculating the Poynting vector and power flux of dipole spin waves. A correct alternative is proposed. (methodological notes)
Setiawan, B.; Septianto, R. D.; Suhendra, D.; Iskandar, F.
2017-01-01
This paper describes the use of an inexpensive smartphone's magnetic sensor to measure magnetic field components (B[subscript x], B[subscript y] and B[subscript z]) induced by current wires in magnetostatic experiments. The variable parameters used to measure the magnetic sensor's capabilities were: the geometrical shapes of the wire, current…
International Nuclear Information System (INIS)
Lin, A.T.; Pritchett, P.L.; Dawson, J.M.
1976-01-01
A large number of important plasma problems involves self-consistent magnetic fields. For disturbances which propagate slowly compared to the velocity of light, the magnetostatic approximation (Darwin model) suffices. Based on the Darwin model a particle model has been developed to investigate such problems. (GG) [de
Laser plasma heating in the presence of electrostatic-magnetostatic crosses fields
International Nuclear Information System (INIS)
Goya, A.; Fonseca, A.L.A.; Nunes, O.A.C.
1994-01-01
The mechanism of plasma heating by one or two lasers in the presence of electrostatic-magnetostatic crossed fields is studied. The results show that the increasing of heating ratio is bigger due to the increment of stationary electric field. 7 refs
International Nuclear Information System (INIS)
Minteer, Timothy M
2013-01-01
The equivalence of the Ampère and Grassmann (Biot–Savart/Lorentz) current element force formulas is well established. However, when the magnetostatic potential energy corresponding to these force formulas is evaluated, the formulas are found to be nonequivalent. The historical current element force formulas are first presented. The magnetostatic potential energy corresponding to these historical current element force formulas are then analysed. The end result establishes the Grassmann and Neumann current element force formulas as the only commonly referenced formulas giving the correct magnetostatic potential energy for circuital currents. (paper)
Zhu, Hong-Ming; Chen, Jin-Wang; Pan, Xiao-Yin; Sahni, Viraht
2014-01-14
We derive via the interaction "representation" the many-body wave function for harmonically confined electrons in the presence of a magnetostatic field and perturbed by a spatially homogeneous time-dependent electric field-the Generalized Kohn Theorem (GKT) wave function. In the absence of the harmonic confinement - the uniform electron gas - the GKT wave function reduces to the Kohn Theorem wave function. Without the magnetostatic field, the GKT wave function is the Harmonic Potential Theorem wave function. We further prove the validity of the connection between the GKT wave function derived and the system in an accelerated frame of reference. Finally, we provide examples of the application of the GKT wave function.
Magnetostatic fields computed using an integral equation derived from Green's theorems
International Nuclear Information System (INIS)
Simkin, J.; Trowbridge, C.W.
1976-04-01
A method of computing magnetostatic fields is described that is based on a numerical solution of the integral equation obtained from Green's Theorems. The magnetic scalar potential and its normal derivative on the surfaces of volumes are found by solving a set of linear equations. These are obtained from Green's Second Theorem and the continuity conditions at interfaces between volumes. Results from a two-dimensional computer program are presented and these show the method to be accurate and efficient. (author)
New exact solutions of the Einstein—Maxwell equations for magnetostatic fields
International Nuclear Information System (INIS)
Goyal, Nisha; Gupta, R.K.
2012-01-01
The symmetry reduction method based on the Fréchet derivative of differential operators is applied to investigate symmetries of the Einstein—Maxwell field equations for magnetostatic fields, which is a coupled system of nonlinear partial differential equations of the second order. The technique yields invariant transformations that reduce the given system of partial differential equations to a system of nonlinear ordinary differential equations. Some of the reduced systems are further studied to obtain the exact solutions
Mathematical and numerical models for eddy currents and magnetostatics with selected applications
Rappaz, Jacques
2013-01-01
This monograph addresses fundamental aspects of mathematical modeling and numerical solution methods of electromagnetic problems involving low frequencies, i.e. magnetostatic and eddy current problems which are rarely presented in the applied mathematics literature. In the first part, the authors introduce the mathematical models in a realistic context in view of their use for industrial applications. Several geometric configurations of electric conductors leading to different mathematical models are carefully derived and analyzed, and numerical methods for the solution of the obtained problem
A Galleria Boundary Element Method for two-dimensional nonlinear magnetostatics
Brovont, Aaron D.
The Boundary Element Method (BEM) is a numerical technique for solving partial differential equations that is used broadly among the engineering disciplines. The main advantage of this method is that one needs only to mesh the boundary of a solution domain. A key drawback is the myriad of integrals that must be evaluated to populate the full system matrix. To this day these integrals have been evaluated using numerical quadrature. In this research, a Galerkin formulation of the BEM is derived and implemented to solve two-dimensional magnetostatic problems with a focus on accurate, rapid computation. To this end, exact, closed-form solutions have been derived for all the integrals comprising the system matrix as well as those required to compute fields in post-processing; the need for numerical integration has been eliminated. It is shown that calculation of the system matrix elements using analytical solutions is 15-20 times faster than with numerical integration of similar accuracy. Furthermore, through the example analysis of a c-core inductor, it is demonstrated that the present BEM formulation is a competitive alternative to the Finite Element Method (FEM) for linear magnetostatic analysis. Finally, the BEM formulation is extended to analyze nonlinear magnetostatic problems via the Dual Reciprocity Method (DRBEM). It is shown that a coarse, meshless analysis using the DRBEM is able to achieve RMS error of 3-6% compared to a commercial FEM package in lightly saturated conditions.
International Nuclear Information System (INIS)
Tang, Tsung-Lin; Fang, Weileun
2011-01-01
This study demonstrates the magnetostatic torsional actuator consisting in a Si–Ni compound frame to significantly improve the driving force. The present design has three merits: (1) it employs a Si mold to simultaneously electroplate/pattern thick Ni, and the Ni and Si structures respectively provide magnetostatic force and superior mechanical properties, (2) the embedded Ni structures not only increase the ferromagnetic material volume but also enhance magnetization strength to enlarge magnetostatic torque, (3) the Si–Ni compound structure, which is nearly symmetric about the torsional axis in the out-of-plane direction, can decrease the moment of inertia and also reduce the wobble motion. In applications, one-axis torsional actuator is implemented and characterized. The experiments show that the Si–Ni compound scanner has an optical scan angle θ optical = 90° with the input power 81 mW. The input power is decreased as compared with the existing scanner. Moreover, the out-of-plane wobble motion is only 44 nm at θ optical = 15°. Compared with the existing designs consisted of asymmetric structures in the out-of-plane direction, such as electroplated film and silicon rib, about the torsional axis, the equivalent eccentric force is reduced nearly two-fold. In short, the proposed design not only increases the driving force but also decreases the wobble motion
Energy Technology Data Exchange (ETDEWEB)
Chaudhuri, A. [B.K.C. College, Department of Physics, Kolkata (India); Chaudhuri, S. [University of Burdwan, Department of Physics, Burdwan (India)
2017-11-15
In the paper, magnetostatic solutions of the Einstein-Maxwell field equations are generated from the gravitational two-soliton solutions of a stationary mass. Using the soliton technique of Belinskii and Zakharov (Sov Phys JETP 48:985, 1978, Sov Phys JETP 50:1, 1979), we construct diagonal two-soliton solutions of Einstein's gravitational field equations for an axially symmetric stationary space-time and investigate some properties of the generated stationary gravitational metric. Magnetostatic solutions corresponding to the generated stationary gravitational solutions are then constructed using the transformation technique of Das and Chaudhuri (Pramana J Phys 40:277, 1993). The mass and the dipole moment of the source are evaluated. In our analysis we make use of a second transformation (Chaudhuri in Pramana J Phys 58:449, 2002), probably for the first time in the literature, to generate magnetostatic solutions from the stationary gravitational two-soliton solutions which give us simple and straightforward expressions for the mass and the magnetic dipole moment. (orig.)
A nonlinear theory of cosmic ray pitch angle diffusion in homogeneous magnetostatic turbulence
International Nuclear Information System (INIS)
Goldstein, M.L.
1975-04-01
A plasma strong turbulence, weak coupling theory is applied to the problem of cosmic ray pitch angle scattering in magnetostatic turbulence. The theory used is a rigorous generalization of Weinstock's resonance-broadening theory and contains no ad hoc approximations. A detailed calculation is presented for a model of slab turbulence with an exponential correlation function. The results agree well with numerical simulations. The rigidity dependence of the pitch angle scattering coefficient differs from that found by previous researchers. The differences result from an inadequate treatment of particle trajectories near 90 0 pitch angle in earlier work
Spin-wave logic devices based on isotropic forward volume magnetostatic waves
International Nuclear Information System (INIS)
Klingler, S.; Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V.
2015-01-01
We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves
Spin-wave logic devices based on isotropic forward volume magnetostatic waves
Energy Technology Data Exchange (ETDEWEB)
Klingler, S., E-mail: stefan.klingler@wmi.badw-muenchen.de; Pirro, P.; Brächer, T.; Leven, B.; Hillebrands, B.; Chumak, A. V. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany)
2015-05-25
We propose the utilization of isotropic forward volume magnetostatic spin waves in modern wave-based logic devices and suggest a concrete design for a spin-wave majority gate operating with these waves. We demonstrate by numerical simulations that the proposed out-of-plane magnetized majority gate overcomes the limitations of anisotropic in-plane magnetized majority gates due to the high spin-wave transmission through the gate, which enables a reduced energy consumption of these devices. Moreover, the functionality of the out-of-plane majority gate is increased due to the lack of parasitic generation of short-wavelength exchange spin waves.
Effect of magnetostatic interactions on twin boundary motion in Ni-Mn-Ga magnetic shape memory alloy
Czech Academy of Sciences Publication Activity Database
Heczko, Oleg; Vokoun, David; Kopecký, Vít; Beleggia, M.
2015-01-01
Roč. 6, Jul (2015), s. 1000204 ISSN 1949-307X R&D Projects: GA ČR GA15-00262S Institutional support: RVO:68378271 Keywords : magnetism in solids * demagnetization factors * magnetostatic interactions * shape memory alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.978, year: 2015
International Nuclear Information System (INIS)
Trowbridge, C.W.
1976-06-01
Various integral equation methods are described. For magnetostatic problems three formulations are considered in detail, (a) the direct solution method for the magnetisation distribution in permeable materials, (b) a method based on a scalar potential and (c) the use of an integral equation derived from Green's Theorem, i.e. the so-called Boundary Integral Method (BIM). In the case of (a) results are given for two-and three-dimensional non-linear problems with comparisons against measurement. For methods (b) and (c) which both lead to a more economic use of the computer than (a) some preliminary results are given for simple cases. For eddy current problems various methods are discussed and some results are given from a computer program based on a vector potential formulation. (author)
Energy Technology Data Exchange (ETDEWEB)
Rodionova, V. [Institute of Physics & Technology and STP “Fabrika” Immanuel Kant Baltic Federal University, A. Nevskogo 14, Kaliningrad 236041 (Russian Federation); National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Baraban, I.; Chichay, K.; Litvinova, A. [Institute of Physics & Technology and STP “Fabrika” Immanuel Kant Baltic Federal University, A. Nevskogo 14, Kaliningrad 236041 (Russian Federation); Perov, N. [Institute of Physics & Technology and STP “Fabrika” Immanuel Kant Baltic Federal University, A. Nevskogo 14, Kaliningrad 236041 (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory 1-2, Moscow 119991 (Russian Federation)
2017-01-15
For glass-coated amorphous ferromagnetic Fe-based microwires both joint and separate effect of metallic nucleus diameter, d, and the ratio of metallic nucleus diameter to the total diameter of microwire in glass shell, d/D, on magnetic properties is investigated. Thereby the contribution of both shell-induced stresses, associated with the ratio of diameters, and internal nucleus stresses (residual, quenching), associated with the diameter of the nucleus are estimated. A strong and non-monotonic effect of the metallic nucleus diameter and metallic nucleus diameter/total microwire diameter ratio on magnetostatic and magnetostrictive properties was established. For analysis, we considered magnetically bi-stable microwires of “classic” Fe{sub 77.5}Si{sub 7.5}B{sub 15} alloy with positive magnetostriction coefficient.
Polarimetry on dense samples of spin-polarized {sup 3}He by magnetostatic detection
Energy Technology Data Exchange (ETDEWEB)
Wilms, E.; Ebert, M.; Heil, W.; Surkau, R. [Mainz Univ. (Germany). Inst. fuer Physik
1997-12-21
A very sensitive low-field fluxgate magnetometer is used to detect the static magnetic field produced by dense samples of spin-polarized {sup 3}He gas contained in spherical glass cells at pressures around several bars. The {sup 3}He nuclear polarization can be extracted with high precision {Delta}P/P<1% by utilizing magnetostatic detection in combination with adiabatic fast-passage spin reversal. The polarization losses can be kept well below 0.1% thus making this type of polarimetry almost non-destructive. More simply even, P can be measured with reduced accuracy by the change of field when the cell is removed from the fluxgate. In this case the accuracy is limited to about 10% due to the uncertainties about the susceptibilities of the cell walls. (orig.). 29 refs.
Polarimetry on dense samples of spin-polarized 3He by magnetostatic detection
International Nuclear Information System (INIS)
Wilms, E.; Ebert, M.; Heil, W.; Surkau, R.
1997-01-01
A very sensitive low-field fluxgate magnetometer is used to detect the static magnetic field produced by dense samples of spin-polarized 3 He gas contained in spherical glass cells at pressures around several bars. The 3 He nuclear polarization can be extracted with high precision ΔP/P<1% by utilizing magnetostatic detection in combination with adiabatic fast-passage spin reversal. The polarization losses can be kept well below 0.1% thus making this type of polarimetry almost non-destructive. More simply even, P can be measured with reduced accuracy by the change of field when the cell is removed from the fluxgate. In this case the accuracy is limited to about 10% due to the uncertainties about the susceptibilities of the cell walls. (orig.)
International Nuclear Information System (INIS)
Rodionova, V.; Baraban, I.; Chichay, K.; Litvinova, A.; Perov, N.
2017-01-01
For glass-coated amorphous ferromagnetic Fe-based microwires both joint and separate effect of metallic nucleus diameter, d, and the ratio of metallic nucleus diameter to the total diameter of microwire in glass shell, d/D, on magnetic properties is investigated. Thereby the contribution of both shell-induced stresses, associated with the ratio of diameters, and internal nucleus stresses (residual, quenching), associated with the diameter of the nucleus are estimated. A strong and non-monotonic effect of the metallic nucleus diameter and metallic nucleus diameter/total microwire diameter ratio on magnetostatic and magnetostrictive properties was established. For analysis, we considered magnetically bi-stable microwires of “classic” Fe_7_7_._5Si_7_._5B_1_5 alloy with positive magnetostriction coefficient.
Co/Au multisegmented nanowires: a 3D array of magnetostatically coupled nanopillars
Bran, C.; Ivanov, Yurii P.; Kosel, Jü rgen; Chubykalo-Fesenko, O.; Vazquez, M.
2017-01-01
Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments. The proposed structure constitutes an innovative route towards a 3D array of synchronized magnetic nano-oscillators with large potential in nanoelectronics.
Energy Technology Data Exchange (ETDEWEB)
Trowbridge, C W
1976-06-01
Various integral equation methods are described. For magnetostatic problems three formulations are considered in detail, (a) the direct solution method for the magnetisation distribution in permeable materials, (b) a method based on a scalar potential, and (c) the use of an integral equation derived from Green's Theorem, i.e. the so-called Boundary Integral Method (BIM). In the case of (a) results are given for two-and three-dimensional non-linear problems with comparisons against measurement. For methods (b) and (c), which both lead to a more economical use of the computer than (a), some preliminary results are given for simple cases. For eddy current problems various methods are discussed and some results are given from a computer program based on a vector potential formulation.
Co/Au multisegmented nanowires: a 3D array of magnetostatically coupled nanopillars
Bran, C.
2017-01-31
Arrays of multisegmented Co/Au nanowires with designed segment lengths and diameters have been prepared by electrodeposition into aluminum oxide templates. The high quality of the Co/Au interface and the crystallographic structure of Co segments have determined by high-resolution transmission electron microscopy. Magnetic hysteresis loop measurements show larger coercivity and squareness of multisegmented nanowires as compared to single segment Co nanowires. The complementary micromagnetic simulations are in good agreement with the experimental results, confirming that the magnetic behavior is defined mainly by magnetostatic coupling between different segments. The proposed structure constitutes an innovative route towards a 3D array of synchronized magnetic nano-oscillators with large potential in nanoelectronics.
Computation of 3-D magnetostatic fields using a reduced scalar potential
International Nuclear Information System (INIS)
Biro, O.; Preis, K.; Vrisk, G.; Richter, K.R.
1993-01-01
The paper presents some improvements to the finite element computation of static magnetic fields in three dimensions using a reduced magnetic scalar potential. New methods are described for obtaining an edge element representation of the rotational part of the magnetic field from a given source current distribution. In the case when the current distribution is not known in advance, a boundary value problem is set up in terms of a current vector potential. An edge element representation of the solution can be directly used in the subsequent magnetostatic calculation. The magnetic field in a D.C. arc furnace is calculated by first determining the current distribution in terms of a current vector potential. A three dimensional problem involving a permanent magnet as well as a coil is solved and the magnetic field in some points is compared with measurement results
The influence of magnetostatic interactions in exchange-coupled composite particles
DEFF Research Database (Denmark)
Vokoun, D.; Beleggia, Marco; De Graef, M.
2010-01-01
Exchange-coupled composite (ECC) particles are the basic constituents of ECC magnetic recording media. We examine and compare two types of ECC particles: (i) core-shell structures, consisting of a hard-magnetic core and a coaxial soft-magnetic shell and (ii) conventional ECC particles, with a hard-magnetic...... core topped by a soft cylindrical element. The model we present describes the magnetic response of the two ECC particle types, taking into account all significant magnetic contributions to the energy landscape. Special emphasis is given to the magnetostatic (dipolar) interaction energy. We find...... that both the switching fields and the zero-field energy barrier depend strongly on the particle geometry. A comparison between the two types reveals that core-shell ECC particles are more effective in switching field reduction, while conventional ECC particles maintain a larger overall figure of merit....
Effect of Magnetostatic Interactions on Twin Boundary Motion in NiMnGa Magnetic Shape Memory Alloy
DEFF Research Database (Denmark)
Heczko, Oleg; Vokoun, David; Kopecky, Vit
2015-01-01
on the initial position of the twin boundary, the magnetic field providing the critical stress varied in the range 832 kA/m. By taking into account the variants sizes and their mutual interactions, we explained the observed dependence of the switching field on the location of the boundary. The resulting match......We investigated the effect of magnetostatic interactions on the field-induced reorientation of martensite variants in Ni50.0Mn27.5Ga22.5. The reorientation, achieved by sweeping a single Type-II twin boundary along the sample, was triggered by a twinning stress of about 0.1 MPa. However, depending...... between model predictions and measurements illustrates the fundamental role played by demagnetization effects and magnetostatic interactions in magnetic shape memory effect....
Magneto-static Modeling from Sunrise/IMaX: Application to an Active Region Observed with Sunrise II
Energy Technology Data Exchange (ETDEWEB)
Wiegelmann, T.; Solanki, S. K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmüller, T. L.; Noort, M. van [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Neukirch, T. [School of Mathematics and Statistics, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Nickeler, D. H. [Astronomical Institute, AV CR, Fricova 298, 25165 Ondrejov (Czech Republic); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Iniesta, J. C. Del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain); Schmidt, W. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Knölker, M., E-mail: wiegelmann@mps.mpg.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)
2017-03-01
Magneto-static models may overcome some of the issues facing force-free magnetic field extrapolations. So far they have seen limited use and have faced problems when applied to quiet-Sun data. Here we present a first application to an active region. We use solar vector magnetic field measurements gathered by the IMaX polarimeter during the flight of the Sunrise balloon-borne solar observatory in 2013 June as boundary conditions for a magneto-static model of the higher solar atmosphere above an active region. The IMaX data are embedded in active region vector magnetograms observed with SDO /HMI. This work continues our magneto-static extrapolation approach, which was applied earlier to a quiet-Sun region observed with Sunrise I. In an active region the signal-to-noise-ratio in the measured Stokes parameters is considerably higher than in the quiet-Sun and consequently the IMaX measurements of the horizontal photospheric magnetic field allow us to specify the free parameters of the model in a special class of linear magneto-static equilibria. The high spatial resolution of IMaX (110–130 km, pixel size 40 km) enables us to model the non-force-free layer between the photosphere and the mid-chromosphere vertically by about 50 grid points. In our approach we can incorporate some aspects of the mixed beta layer of photosphere and chromosphere, e.g., taking a finite Lorentz force into account, which was not possible with lower-resolution photospheric measurements in the past. The linear model does not, however, permit us to model intrinsic nonlinear structures like strongly localized electric currents.
International Nuclear Information System (INIS)
Hierro-Rodriguez, A; Teixeira, J M; Rodriguez-Rodriguez, G; Rubio, H; Vélez, M; Álvarez-Prado, L M; Martín, J I; Alameda, J M
2015-01-01
Hybrid 2D hard-soft composites have been fabricated by combining soft (Co 73 Si 27 ) and hard (NdCo 5 ) magnetic materials with in-plane and out-of-plane magnetic anisotropies, respectively. They have been microstructured in a square lattice of CoSi anti-dots with NdCo dots within the holes. The magnetic properties of the dots allow us to introduce a magnetostatic stray field that can be controlled in direction and sense by their last saturating magnetic field. The magnetostatic interactions between dot and anti-dot layers induce a completely tunable exchange bias-like shift in the system’s hysteresis loops. Two different regimes for this shift are present depending on the lattice parameter of the microstructures. For large parameters, dipolar magnetostatic decay is observed, while for the smaller one, the interaction between the adjacent anti-dot’s characteristic closure domain structures enhances the exchange bias-like effect as clarified by micromagnetic simulations. (paper)
Class of analytic solutions for the thermally balanced magnetostatic prominence sheet
International Nuclear Information System (INIS)
Low, B.C.; Wu, S.T.
1981-01-01
This is a theoretical study of the nonlinear interplay between magnetostatic equilibrium and energy balance in a Kippenhahn-Schlueter type prominence sheet. The basic effects are illustrated explicitly with an analytic model in which a radiative loss proportional to rho 2 T balances against wave heating proportional to rho, with thermal conduction confined along magnetic field lines, where rho and T denote the plasma density and temperature, respectively. The particular choices of heat sink and source enable us to integrate the governing equations exactly while they are of the basic mathematical forms to simulate radiative loss in an optically thin plasma which is heated by wave dissipation. The steady solutions exhibit three different basic behaviors, characterized by the total wave heating in the prominence sheet being more than, equal to, or less than the total radiative loss. It is the compaction of the plasma along the field lines under its own weight combined with the effects of energy transport that determines which of the three basic behaviors obtains in a particular situation. The implications of the steady solutions for the formation of prominences are discussed. The exact solutions presented do not support the conclusion of Milne, Priest, and Roberts that there is an upper bound on the plasma beta for an equilibrium of the Kippenhahn-Schlueter prominence
Magnetostatic analysis of a rotor system supported by radial active magnetic bearings
Directory of Open Access Journals (Sweden)
Ferfecki P.
2009-06-01
Full Text Available The development and the design of a radial active magnetic bearing (AMB reflects a complex process of the multidisciplinary rotor dynamics, electromagnetism and automatic control analysis. Modelling is performed by application of the physical laws from different areas, e.g. Newton's laws of motion and Maxwell's equations. The new approach in the numerical modelling of radial AMB and design methodology allowing automatic generation of primary dimensions of the radial AMB is proposed. Instead of the common way of computation of electromagnetic forces by linearizing at the centre position of the rotor with respect to rotor displacement and coil current, the finite element computation of electromagnetic forces is used. The heteropolar radial AMB consisting of eight pole shoes was designed by means of the built up algorithms for rotor system with two discs fixed on the cantilever shaft. A study of the influence of the nonlinear magnetization characteristics of a rotor and stator material on the equilibrium position of a rotor system is carried out. The performed numerical study shows that results obtained from the analytical nonlinear relation for electromagnetic forces can be considerably different from forces computed with magnetostatic finite element analysis.
Tensile stress dependence of the magnetostatic interaction between Fe-rich wires
International Nuclear Information System (INIS)
Gawronski, P.; Zhukov, A.; Blanco, J.M.; Gonzalez, J.; KuIakowski, K.
2005-01-01
We study the influence of the applied tensile stress on the magnetostatic interaction between two amorphous Fe-rich wires. The hysteresis loop is measured for: (i) conventional wires produced by in-rotation-water method, with diameter of 125μm (ii) cold-drawn wires with diameter of 50μm. The stress dependence of the interaction field is evaluated from the shape of the hysteresis loops, which show characteristic two-step behaviour. These steps mark the values of the switching field of the wires. For the conventional wires the tensile stress dependence of the interaction field can be explained as a result of the tensile stress dependence of the magnetization. For the cold-drawn wires, the interaction field shows a maximum with the applied stress. This behaviour is interpreted as a consequence of a local variation of the domain structure at the wire ends. It modifies the stray field, and-as a consequence-the switching field of the neighbouring wire
Hano, Mitsuo; Hotta, Masashi
A new multigrid method based on high-order vector finite elements is proposed in this paper. Low level discretizations in this method are obtained by using low-order vector finite elements for the same mesh. Gauss-Seidel method is used as a smoother, and a linear equation of lowest level is solved by ICCG method. But it is often found that multigrid solutions do not converge into ICCG solutions. An elimination algolithm of constant term using a null space of the coefficient matrix is also described. In three dimensional magnetostatic field analysis, convergence time and number of iteration of this multigrid method are discussed with the convectional ICCG method.
International Nuclear Information System (INIS)
Mintchev, Pavel; Dimitrov, Marin; Balinov, Stoimen
2002-01-01
The possibilities for applying the Finite Element Method (FEM) with gauged magnetic vector potential and the Edge Element Method (EEM) for three-dimensional numerical analysis of magnetostatic systems are analyzed. It is established that the EEM ensures sufficient accuracy for engineering calculations but in some cases its use results in bad convergence. The use of the FEM with gauged magnetic vector potential instead of the EEM is recommended for preliminary calculations of devices with complex geometry and large air gaps between the ferromagnetic parts. (Author)
International Nuclear Information System (INIS)
Lerche, I.; Low, B.C.
1977-01-01
A theoretical model of quiescent prominences in the form of an infinite vertical sheet is presented. Self-consistent solutions are obtained by integrating simultaneously the set of nonlinear equations of magnetostatic equilibrium and thermal balance. The basic features of the models are: (1) The prominence matter is confined to a sheet and supported against gravity by a bowed magnetic field. (2) The thermal flux is channelled along magnetic field lines. (3) The thermal flux is everywhere balanced by Low's (1975) hypothetical heat sink which is proportional to the local density. (4) A constant component of the magnetic field along the length of the prominence shields the cool plasma from the hot surrounding. It is assumed that the prominence plasma emits more radiation than it absorbes from the radiation fields of the photosphere, chromosphere and corona, and the above hypothetical heat sink is interpreted to represent the amount of radiative loss that must be balanced by a nonradiative energy input. Using a central density and temperature of 10 11 particles cm -3 and 5000 K respectively, a magnetic field strength between 2 to 10 gauss and a thermal conductivity that varies linearly with temperature, the physical properties implied by the model are discussed. The analytic treatment can also be carried out for a class of more complex thermal conductivities. These models provide a useful starting point for investigating the combined requirements of magnetostatic equilibrium and thermal balance in the quiescent prominence. (Auth.)
Septianto, R. D.; Suhendra, D.; Iskandar, F.
2017-01-01
This paper reports on the result of a research into the utilisation of a smartphone for the study of magnetostatics on the basis of experiments. The use of such a device gives great measurement result and thus it can replace magnetic sensor tools that are relatively expensive. For the best experimental result, firstly the position of the magnetic…
Energy Technology Data Exchange (ETDEWEB)
Anfinogenov, V B; Gulyaev, Yu V; Zil' berman, P E; Kotelyanskij, I M; Polzikova, N I; Sukhanov, A A [AN SSSR, Moscow (USSR). Inst. Radiotekhniki i Ehlektroniki
1989-07-26
Conditions for magneto-static wave (MSW) propagation in laminar structures ferrite-high-temperature superconductor (YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}) and effect of transition into superconducting state under the temperature drop on these conditions are investigated. MSW electron absorption effrect in such structures (strongly dependent on the temperature) is detected and its interpretation is given.
International Nuclear Information System (INIS)
Tucker, T.C.
1980-06-01
The implementation of a version of the Rutherford Laboratory's magnetostatic computer code GFUN3D on the CDC 7600 at the National Magnetic Fusion Energy Computer Center is reported. A new iteration technique that greatly increases the probability of convergence and reduces computation time by about 30% for calculations with nonlinear, ferromagnetic materials is included. The use of GFUN3D on the NMFE network is discussed, and suggestions for future work are presented. Appendix A consists of revisions to the GFUN3D User Guide (published by Rutherford Laboratory( that are necessary to use this version. Appendix B contains input and output for some sample calculations. Appendix C is a detailed discussion of the old and new iteration techniques
Energy Technology Data Exchange (ETDEWEB)
Nascimento, Francisco Rogerio Teixeira do
2013-07-01
The main objective of this work is to simulate electromagnetic fields using the Finite Element Method. Even in the easiest case of electrostatic and magnetostatic numerical simulation some problems appear when the nodal finite element is used. It is difficult to model vector fields with scalar functions mainly in non-homogeneous materials. With the aim to solve these problems two types of techniques are tried: the adaptive remeshing using nodal elements and the edge finite element that ensure the continuity of tangential components. Some numerical analysis of simple electromagnetic problems with homogeneous and non-homogeneous materials are performed using first, the adaptive remeshing based in various error indicators and second, the numerical solution of waveguides using edge finite element. (author)
Muniz, Sérgio R.; Bhattacharya, M.; Bagnato, Vanderlei S.
2010-01-01
In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method does not require integration or knowledge of the current distribution, and is presented through practical examples, including a non-uniform finite so...
Energy Technology Data Exchange (ETDEWEB)
Boulbe, C
2007-10-15
Interaction between a plasma and a magnetic field appears and has an important role in various domains such as thermonuclear fusion by magnetic confinement or astrophysical plasmas for example. In evolution, these interactions are described by the equations of magnetohydrodynamics (MHD). At equilibrium, the MHD equations result in the magnetostatic equations involving the magnetic field and the kinetic pressure of the plasma. The magnetostatic equations form a system of 3-dimensional non linear partial differential equations involving a magnetic field and a kinetic plasma pressure. When the pressure is supposed negligible, the magnetic field is known as Beltrami field. In a first time, we propose to solve numerically the Beltrami field problem using a fixed point iterative algorithm associated with finite element methods. This iterative strategy is extended in a second time to the computation of magnetostatic configurations with pressure. In the sequel, we interest in the approximation of ideal MHD equations. This system forms a nonlinear hyperbolic conservation law. We propose to use a finite volume approach, in which fluxes are calculated by a Roe's method on a tetrahedral mesh. Fluxes of the magnetic field are modified in order to satisfy the constraint of divergence free imposed on it. The proposed methods have been implemented in two new 3-dimensional codes called TETRAFFF for equilibrium, and TETRAMHD for MHD. The obtained numerical results confirm the high performance of these methods. (author)
International Nuclear Information System (INIS)
Marko, Daniel
2010-01-01
In the present work, the implications of ion irradiation on the magnetostatic and dynamic properties of soft magnetic Py/Ta (Py=Permalloy: Ni 80 Fe 20 ) single and multilayer films have been investigated with the main objective of finding a way to determine their saturation magnetization. Both polar magneto-optical Kerr effect (MOKE) and vector network analyzer ferromagnetic resonance (VNA-FMR) measurements have proven to be suitable methods to determine μ 0 M S , circumventing the problem of the unknown effective magnetic volume that causes conventional techniques such as SQUID or VSM to fail. Provided there is no perpendicular anisotropy contribution in the samples, the saturation magnetization can be determined even in the case of strong interfacial mixing due to an inherently high number of Py/Ta interfaces and/or ion irradiation with high fluences. Another integral part of this work has been to construct a VNA-FMR spectrometer capable of performing both azimuthal and polar angle-dependent measurements using a magnet strong enough to saturate samples containing iron. Starting from scratch, this comprised numerous steps such as developing a suitable coplanar waveguide design, and writing the control, evaluation, and fitting software. With both increasing ion fluence and number of Py/Ta interfaces, a decrease of saturation magnetization has been observed. In the case of the 10 x Py samples, an immediate decrease of μ 0 M S already sets in at small ion fluences. However, for the 1 x Py and 5 x Py samples, the saturation magnetization remains constant up to a certain ion fluence, but then starts to rapidly decrease. Ne ion irradiation causes a mixing and broadening of the interfaces. Thus, the Py/Ta stacks undergo a transition from being polycrystalline to amorphous at a critical fluence depending on the number of interfaces. The saturation magnetization is found to vanish at a Ta concentration of about 10-15 at.% in the Py layers. The samples possess a small
Energy Technology Data Exchange (ETDEWEB)
Marko, Daniel
2010-11-25
In the present work, the implications of ion irradiation on the magnetostatic and dynamic properties of soft magnetic Py/Ta (Py=Permalloy: Ni{sub 80}Fe{sub 20}) single and multilayer films have been investigated with the main objective of finding a way to determine their saturation magnetization. Both polar magneto-optical Kerr effect (MOKE) and vector network analyzer ferromagnetic resonance (VNA-FMR) measurements have proven to be suitable methods to determine {mu}{sub 0}M{sub S}, circumventing the problem of the unknown effective magnetic volume that causes conventional techniques such as SQUID or VSM to fail. Provided there is no perpendicular anisotropy contribution in the samples, the saturation magnetization can be determined even in the case of strong interfacial mixing due to an inherently high number of Py/Ta interfaces and/or ion irradiation with high fluences. Another integral part of this work has been to construct a VNA-FMR spectrometer capable of performing both azimuthal and polar angle-dependent measurements using a magnet strong enough to saturate samples containing iron. Starting from scratch, this comprised numerous steps such as developing a suitable coplanar waveguide design, and writing the control, evaluation, and fitting software. With both increasing ion fluence and number of Py/Ta interfaces, a decrease of saturation magnetization has been observed. In the case of the 10 x Py samples, an immediate decrease of {mu}{sub 0}M{sub S} already sets in at small ion fluences. However, for the 1 x Py and 5 x Py samples, the saturation magnetization remains constant up to a certain ion fluence, but then starts to rapidly decrease. Ne ion irradiation causes a mixing and broadening of the interfaces. Thus, the Py/Ta stacks undergo a transition from being polycrystalline to amorphous at a critical fluence depending on the number of interfaces. The saturation magnetization is found to vanish at a Ta concentration of about 10-15 at.% in the Py layers
Santos, Joao
2017-10-01
Powerful laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in the kTesla range. The B-fields are measured by proton-deflectometry and high-frequency bandwidth B-dot probes. According to our modeling, the quasi-static currents are provided from hot electron ejection from the laser-irradiated surface, accounting for the space charge neutralization and the plasma magnetization. The major control parameter is the laser irradiance Iλ2 . The B-fields ns-scale is long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport into solid dielectric targets, yielding an unprecedented enhancement of a factor 5 on the energy-density flux at 60 µm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes and to laboratory astrophysics. We acknowledge funding from French National Agency for Research (ANR), Grant TERRE ANR-2011-BS04-014, and from EUROfusion Consortium, European Union's Horizon 2020 research and innovation programme, Grant 633053.
Santos, J. J.; Bailly-Grandvaux, M.; Ehret, M.; Arefiev, A. V.; Batani, D.; Beg, F. N.; Calisti, A.; Ferri, S.; Florido, R.; Forestier-Colleoni, P.; Fujioka, S.; Gigosos, M. A.; Giuffrida, L.; Gremillet, L.; Honrubia, J. J.; Kojima, S.; Korneev, Ph.; Law, K. F. F.; Marquès, J.-R.; Morace, A.; Mossé, C.; Peyrusse, O.; Rose, S.; Roth, M.; Sakata, S.; Schaumann, G.; Suzuki-Vidal, F.; Tikhonchuk, V. T.; Toncian, T.; Woolsey, N.; Zhang, Z.
2018-05-01
Powerful nanosecond laser-plasma processes are explored to generate discharge currents of a few 100 kA in coil targets, yielding magnetostatic fields (B-fields) in excess of 0.5 kT. The quasi-static currents are provided from hot electron ejection from the laser-irradiated surface. According to our model, which describes the evolution of the discharge current, the major control parameter is the laser irradiance Ilasλlas2 . The space-time evolution of the B-fields is experimentally characterized by high-frequency bandwidth B-dot probes and proton-deflectometry measurements. The magnetic pulses, of ns-scale, are long enough to magnetize secondary targets through resistive diffusion. We applied it in experiments of laser-generated relativistic electron transport through solid dielectric targets, yielding an unprecedented 5-fold enhancement of the energy-density flux at 60 μm depth, compared to unmagnetized transport conditions. These studies pave the ground for magnetized high-energy density physics investigations, related to laser-generated secondary sources of radiation and/or high-energy particles and their transport, to high-gain fusion energy schemes, and to laboratory astrophysics.
Abedi-Varaki, M.
2018-02-01
In this paper, the effects of planar magnetostatic wiggler and s-parameter on the terahertz (THz) radiation generation through rippled plasma have been investigated. Efficient THz radiation generation by photo-mixing of tophat lasers for rippled density plasma in the presence of the wiggler field has been presented. Fundamental equations for the analysis of the non-linear current density and THz radiation generation by wiggler magnetostatic field have been derived. It is shown that for the higher order of the tophat lasers, the values of THz amplitude are greater. In fact, the higher order of the tophat lasers has a sharp gradient in the intensity of lasers, which leads to a stronger nonlinear ponderomotive force and, consequently, a stronger current density. In addition, it is seen that by increasing s-parameter, the normalized transverse profile becomes more focused near the axis of y. Furthermore, it is observed that the normalized laser efficiency has a decreasing trend with increasing normalized THz frequency for different values of the wiggler field. Also, it is shown that by employing a greater order of the tophat lasers and a stronger wiggler field, the efficiency of order of 30% can be achieved. Moreover, it is found that we can control focus and intensity of THz radiation emitted in rippled plasma by choosing the appropriate order of the tophat lasers and tuning of the wiggler field.
Optimising Magnetostatic Assemblies
DEFF Research Database (Denmark)
Insinga, Andrea Roberto; Smith, Anders
theorem. This theorem formulates an energy equivalence principle with several implications concerning the optimisation of objective functionals that are linear with respect to the magnetic field. Linear functionals represent different optimisation goals, e.g. maximising a certain component of the field...... approached employing a heuristic algorithm, which led to new design concepts. Some of the procedures developed for linear objective functionals have been extended to non-linear objectives, by employing iterative techniques. Even though most the optimality results discussed in this work have been derived...
Lim, Jinho; Bang, Wonbae; Trossman, Jonathan; Amanov, Dovran; Ketterson, John B.
2018-05-01
We present experimental and theoretical results on the propagation of magnetostatic spin waves in a film of yttrium iron garnet (YIG) for out-of-plane magnetic fields for which propagation in opposite directions is nonreciprocal in the presence of a metal layer. The plane studied is defined by the film normal n and n × k where k is the wave vector of the mode. Spin waves in this setting are classified as forward volume waves or surface waves and display non-reciprocity in the presence of an adjacent metal layer except for when H//n. The measurements are carried out in a transmission geometry, and a microwave mixer is used to measure the change of phase, and with it the evolution of wavevector, of the arriving spin wave with external magnetic field.
International Nuclear Information System (INIS)
Buffa, A.
1967-06-01
The effect of a circularly polarized wave on a cylindrical plasma in a axial magnetostatic field and a radial space-charge field proportional to r is studied. Single particle motion is considered. The electrostatic field produces a shift in the cyclotron resonance frequency and,in case of high charge density, a radial movement of the off-resonance particles. In these conditions a radio-frequency-particle resonance is also possible called 'drift-resonance'. The drift resonance can be produced, with whistler mode, and may be employed in ion acceleration. Afterwards parametrical resonances produced by space-charge field oscillations and collisional limits of theory are studied. Cases in which ion acceleration is possible are considered on the basis of a quantitative analysis of results. (author) [fr
International Nuclear Information System (INIS)
Soh, Wee Tee; Ong, C. K.; Peng, Bin
2015-01-01
We demonstrate the localized excitation and dc electrical detection of magnetostatic surface spin waves (MSSWs) in yttrium iron garnet (YIG) by a shorted coaxial probe. Thin films of NiFe and Pt are patterned at different regions onto a common bulk YIG substrate. A shorted coaxial probe is used to excite spin precession locally near various patterned regions. The dc voltages across the corresponding regions are recorded. For excitation of the Pt regions, the dc voltage spectra are dominated by the spin pumping of MSSWs from YIG, where various modes can be clearly distinguished. For the NiFe region, it is also found that spin pumping from MSSWs generated in YIG dominated the spectra, indicating that the spin pumped currents are dissipated into charge currents via the inverse Spin Hall effect (ISHE) in NiFe. For all regions, dc signals from YIG MSSWs are observed to be much stronger than the ferromagnetic resonance (FMR) uniform mode, likely due to the nature of the microwave excitation. The results indicate the potential of this probe for microwave imaging via dc detection of spin dynamics in continuous and patterned films
International Nuclear Information System (INIS)
Li, Y.F.; Vazquez, M.; Chen, D.X.; Hernando, A.
2002-01-01
Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 amorphous wire was annealed at different temperatures (T a =400-700 deg. C, for 30 min) that result in partial devitrification and subsequently, the quasi-saturated hysteresis loop was measured. It is found that the loops are not symmetric, exhibiting two coercive fields, H c1 and H c2 , on descending and ascending branches, respectively. Moreover, the asymmetry degree is modified when the sample is previously magnetized under a field of 60 kA m -1 . The dependence on both maximum measured field, H m , and temperature, T, of the displaced loop has been determined. With increasing H m , the shift H sh =(H c2 +H c1 )/2 decreases and the coercivity H c =(H c2 -H c1 )/2 increases, but H sh -H c H c1 remains constant. Both H sh and the magnetic polarization, μ 0 M m , at maximum field decreases with elevating T. The loop of this sample also shows a remarkable time-effect. The H m - and T-dependent H sh is discussed considering the existence of an effective bias-field generated from the magnetostatic interaction between the nanocrystalline particles and residual soft matrix, and the time-effect could be ascribed to the dipolar interaction among the particles. (author)
Magnetostatics of anisotropic superconducting ellipsoid
International Nuclear Information System (INIS)
Saif, A.G.
1987-09-01
The magnetization and the magnetic field distribution inside (outside) an anisotropic type II superconducting ellipsoid, with filamentary structure, is formulated. We have shown that the magnetic field in this case is different from that of the general anisotropic one. The nucleations of the flux lines for specimens with large demagnetization factors are theoretically studied. We have shown that the nucleations of the flux lines, for specimens with large demagnetization factor, appears at a field larger than that of ellipsoidal shape. (author). 15 refs
Inertial electro-magnetostatic plasma neutron sources
International Nuclear Information System (INIS)
Barnes, D.C.; Nebel, R.A.; Schauer, M.M.; Pickrel, M.M.
1997-01-01
Two types of systems are being studied experimentally as D-T plasma neutron sources. In both concepts, spherical convergence of either electrons or ions or both is used to produce a dense central focus within which D-T fusion reactions produce 14 MeV neutrons. One concept uses nonneutral plasma confinement principles in a Penning type trap. In this approach, combined electrostatic and magnetic fields provide a vacuum potential well within which electrons are confined and focused. A small (6 mm radius) spherical machine has demonstrated a focus of 30 microm radius, with a central density of up to 35 times the Brillouin density limit of a static trap. The resulting electron plasma of up to several 10 13 cm -3 provides a multi-kV electrostatic well for confining thermonuclear ions as a neutron source. The second concept (Inertial Electrostatic Confinement, or IEC) uses a high-transparence grid to form a global well for acceleration and confinement of ions. Such a system has demonstrated steady neutron output of 2 x 10 10 s -1 . The present experiment will scale this to >10 11 s -1 . Advanced designs based on each concept have been developed recently. In these proposed approaches, a uniform-density electron sphere forms an electrostatic well for ions. Ions so trapped may be focused by spherical convergence to produce a dense core. An alternative approach produces large amplitude spherical oscillations of a confined ion cloud by a small, resonant modulation of the background electrons. In both the advanced Penning trap approach and the advanced IEC approach, the electrons are magnetically insulated from a large (up to 100 kV) applied electrostatic field. The physics of these devices is discussed, experimental design details are given, present observations are analyzed theoretically, and the performance of future advanced systems are predicted
Electro-magnetostatic homogenization of bianisotropic metamaterials
Fietz, Chris
2012-01-01
We apply the method of asymptotic homogenization to metamaterials with microscopically bianisotropic inclusions to calculate a full set of constitutive parameters in the long wavelength limit. Two different implementations of electromagnetic asymptotic homogenization are presented. We test the homogenization procedure on two different metamaterial examples. Finally, the analytical solution for long wavelength homogenization of a one dimensional metamaterial with microscopically bi-isotropic i...
Magnetostatic Interaction in Fe-Co Nanowires
Directory of Open Access Journals (Sweden)
Laura Elbaile
2012-01-01
Full Text Available Arrays of Fe-Co alloy nanowires with diameter around 35 nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves were characterized by SEM, TEM, X-ray diffraction (XRD, and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc structure and a preferred (110 orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.
Energy Technology Data Exchange (ETDEWEB)
Buffa, A [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1967-06-15
The effect of a circularly polarized wave on a cylindrical plasma in a axial magnetostatic field and a radial space-charge field proportional to r is studied. Single particle motion is considered. The electrostatic field produces a shift in the cyclotron resonance frequency and,in case of high charge density, a radial movement of the off-resonance particles. In these conditions a radio-frequency-particle resonance is also possible called 'drift-resonance'. The drift resonance can be produced, with whistler mode, and may be employed in ion acceleration. Afterwards parametrical resonances produced by space-charge field oscillations and collisional limits of theory are studied. Cases in which ion acceleration is possible are considered on the basis of a quantitative analysis of results. (author) [French] On etudie l'effet d'une onde polarisee circulairement sur un plasma cylindrique place dans un champ magnetique axial constant, en supposant etre en presence d'un, champ de charge d'espace radial proportionnel a r. L'etude est faite du point de vue de la particule individuelle. Le champ electrostatique deplace la frequence de resonance cyclotron et, dans le cas de forte densite, donne lieu a un mouvement radial des particules qui ne sont pas en resonance. Dans ces champs, il peut aussi se produire une resonance qu'on a appele 'de derive', entre un R.F. et la particule. Cette resonance peut se produire avec le mode siffleur et peut etre utilisee pour l'acceleration des ions. On considere ensuite les resonances parametriques, qui se manifestent lorsque le champ de charge d'espace oscille, et les limites a la theorie posees par les collisions. Une discussion quantitative des resultats fait ressortir les cas dans lesquels on peut accelerer les ions. (auteur)
Magnetostatic interactions and forces between cylindrical permanent magnets
International Nuclear Information System (INIS)
Vokoun, David; Beleggia, Marco; Heller, Ludek; Sittner, Petr
2009-01-01
Permanent magnets of various shapes are often utilized in magnetic actuators, sensors or releasable magnetic fasteners. Knowledge of the magnetic force is required to control devices reliably. Here, we introduce an analytical expression for calculating the attraction force between two cylindrical permanent magnets on the assumption of uniform magnetization. Although the assumption is not fulfilled exactly in cylindrical magnets, we obtain a very good agreement between the calculated and measured forces between two identical cylindrical magnets and within an array of NdFeB cylindrical magnets.
A New Approach for Magneto-Static Hysteresis Behavioral Modeling
DEFF Research Database (Denmark)
Astorino, Antonio; Swaminathan, Madhavan; Antonini, Giulio
2016-01-01
in this paper is based on simple functions, which do not require calculus to be involved, thus assuring a very good efficiency in the algorithm. In addition, the proposed method enables initial magnetization curves, symmetric loops, minor loops, normal curves, and reversal curves of any order to be reproduced......, as demonstrated through the pertinent results provided in this paper. A model example based on the proposed modeling technique is also introduced and used as inductor core, in order to simulate an LR series circuit. Finally, the model ability to emulate hysteretic inductors is proved by the satisfactory agreement...
Long-range magnetostatic interactions in arrays of nanowires
Raposo, V; González, J M; Vázquez, M
2000-01-01
Experimental measurements and micromagnetic simulations of the hysteresis loops of arrays of cobalt nanowires are compared here. Arrays of cobalt nanowires (200 nm in diameter) were electrodeposited into the pores of alumina membranes (thickness 60 mu m). Their hysteresis loops along the axial direction of nanowires were measured using vibrating sample magnetometry. Micromagnetic simulations were performed considering dipolar interaction between nanowires leading to similar hysteresis loops as those obtained experimentally.
Modeling of Stability of Electrostatic and Magnetostatic Systems
2017-06-01
15. SUBJECT TERMS electromagnetism, morphological instabilities, computational algorithm, gradient minimization, morphology patterns, motion by mean...variational approach is definitely underdeveloped. In particular, in terms of calculus of variations, all of the studies are based on the analysis of the...10) 4) at infinity 0ϕ → . (11) Thus, from the mathematical point of view, we arrive at the problem of multidimensional calculus of variations
Numerical Solution of Magnetostatic Field of Maglev System
Directory of Open Access Journals (Sweden)
Jaroslav Sobotka
2008-01-01
Full Text Available The paper deals with the design of the levitation and guidance system of the levitation train Transrapid 08 by means of QuickField 5.0 – a 2D program formagnetic electromagnetic fields solutions.
Magnetostatic bias in a composite hard/soft/hard microlayer
Czech Academy of Sciences Publication Activity Database
Kraus, Luděk; Pirota, K.R.; Torrejón, J.; Vázquez, M.
2007-01-01
Roč. 101, č. 6 (2007), 063910/1-063910/4 ISSN 0021-8979 Grant - others:Spanish Research Project(ES) MAT2004-00150 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic bias * amorphous alloys * geometrical dimensions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.171, year: 2007
Theory of magnetostatic equilibria and applications in astrophysics
International Nuclear Information System (INIS)
Amari, T.
1988-04-01
Magnetohydrostatic equations are used to study the properties of magnetic configurations of astrophysical interest, particularly in solar physics. Results on force-free solutions with singularities (with current sheets) and on solutions which take into account current sheets and gravitational fields are obtained. A general method to construct an infinite class of non-y-symmetric models of protuberances when the magnetic field of the support is assumed to be potential is outlined. The general integral properties of current sheets of arbitrary geometry plunged into a nonlinear force-free magnetic field are established. It is shown that for a given mass, the equilibrium height of the protuberance increases with the shear of the force-free field. The case where the current sheet is reduced to a filament is examined. It is also shown that there exists a critical pressure beyond which no equilibrium is possible [fr
Application of the MHD energy principle to magnetostatic atmospheres
International Nuclear Information System (INIS)
Zweibel, E.G.
1984-11-01
We apply the MHD energy principle to the stability of a magnetized atmosphere which is bounded below by much denser fluid, as is the solar corona. We treat the two fluids as ideal; the approximation which is consistent with the energy principle, and use the dynamical conditions that must hold at a fluid-fluid interface to show that if vertical displacements of the lower boundary are permitted, then the lower atmosphere must be perturbed as well. However, displacements which do not perturb the coronal boundary can be properly treated as isolated perturbations of the corona alone
Magnetostatic coupling of 900 domain walls in Fe19Ni81/Cu/Co trilayers
International Nuclear Information System (INIS)
Kurde, J; Miguel, J; Kuch, W; Bayer, D; Aeschlimann, M; Sanchez-Barriga, J; Kronast, F; Duerr, H A
2011-01-01
The magnetic interlayer coupling of Fe 19 Ni 81 /Cu/Co trilayered microstructures has been studied by means of x-ray magnetic circular dichroism in combination with photoelectron emission microscopy (XMCD-PEEM). We find that a parallel coupling between magnetic domains coexists with a non-parallel coupling between magnetic domain walls (DWs) of each ferromagnetic layer. We attribute the non-parallel coupling of the two magnetic layers to local magnetic stray fields arising at DWs in the magnetically harder Co layer. In the magnetically softer FeNi layer, non-ordinary DWs, such as 270 0 and 90 0 DWs with overshoot of the magnetization either inwards or outwards relative to the turning direction of the Co magnetization, are identified. Micromagnetic simulations reveal that in the absence of magnetic anisotropy, both types of overshooting DWs are energetically equivalent. However, if a uniaxial in-plane anisotropy is present, the relative orientation of the DWs with respect to the anisotropy axis determines which of these DWs is energetically favorable.
Axial to transverse energy mixing dynamics in octupole-based magnetostatic antihydrogen traps
Zhong, M.; Fajans, J.; Zukor, A. F.
2018-05-01
The nature of the trajectories of antihydrogen atoms confined in an octupole minimum-B trap is of great importance for upcoming spectroscopy, cooling, and gravity experiments. Of particular interest is the mixing time between the axial and transverse energies for the antiatoms. Here, using computer simulations, we establish that almost all trajectories are chaotic, and then quantify the characteristic mixing time between the axial and transverse energies. We find that there are two classes of trajectories: for trajectories whose axial energy is higher than about 20% of the total energy, the axial energy substantially mixes within about 10 s, whereas for trajectories whose axial energy is lower than about 10% of the total energy, the axial energy remains nearly constant for 1000 s or longer.
Majidi, Sharareh; Emden, Markus
2013-01-01
One of the main components of teachers' pedagogical content knowledge refers to their use of representation forms. In a similar vein, organizing concepts logically and meaningfully is an essential element of teachers' subject matter knowledge. Since subject matter and pedagogical content knowledge of teachers are tightly connected as categories…
Majidi, Sharareh
2013-01-01
Physics has been always one of the most challenging subjects to learn for university and school students. It is also considered a demanding topic for teachers who aim to teach it efficiently. Therefore, one of the most important notions in physics is to find suitable ways to maximize productive learning and teaching outcomes. One of the most important factors that influence physics learning and teaching is the organization of physics knowledge and the ability to arrange its concepts properly....
A magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake
International Nuclear Information System (INIS)
Yan Chen; Fan Ming-Wu
1984-01-01
A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake
Synchronization of vortex-based spin torque nano-oscillators by magnetostatic coupling
Energy Technology Data Exchange (ETDEWEB)
Zaspel, C.E., E-mail: craig.zaspel@umwestern.edu
2015-12-15
Synchronization of two nanopillar oscillators driven by spin torque and coupled through the magnetic dipolar interaction. The dominant mode in each oscillator is gyrotropic motion of the vortex core in an elliptical orbit about the free layer disk center. The dynamic properties of this mode is investigated by solution the coupled Thiele equations with both nanopillar oscillators having identical dimensions, but with a current mismatch. It is noticed that there is a range in the current difference where the oscillators will be synchronized where the vortex gyrotropic motion will be frequency-locked with the radii of gyrotropic motion equal for both disks. There is, however, a phase shift between the gyrotropic motion with the smaller current disk lagging the higher current disk by a few degrees. - Highlights: • Vortex-based nanopillar oscillators re synchronized by the dipolar interaction. • There is a range of frequencies where both oscillators will frequency-locked. • There are upper and lower critical currents defining a locking range.
Test particle propagation in magnetostatic turbulence. 3: the approach to equilibrium
International Nuclear Information System (INIS)
Klimas, A.J.; Sandri, G.; Scudder, J.D.; Howell, D.R.
1977-05-01
The asymptotic behavior, for large time, of the quasi-linear diabatic solutions and their local approximations is considered. A time averaging procedure is introduced which yields the averages of these solutions over time intervals which contain only large time values. A discussion of the quasi-linear diabatic solutions which is limited to those solutions that are bounded from below as functions of time is given. It is shown that as the upper limit of the time averaging interval is allowed to approach infinity the time averaged quasi-linear diabatic solutions must approach isotropy (mu-independence). The first derivative with respect to mu of these solutions is also considered. This discussion is limited to first derivatives which are bounded functions of time. It is shown that as the upper limit of the time averaging interval is allowed to approach infinity, the time averaged first derivative must approach zero everywhere in mu except at mu = 0 where it must approach a large value which is calculated. The impact of this large derivative on the quasi-linear expansion scheme is discussed. An H-theorem for the first local approximation to the quasi-linear diabatic solutions is constructed. Without time averaging, the H-theorem is used to determine sufficient conditions for the first local approximate solutions to asymptote, with increasing time, to exactly the same final state which the time averaged quasi-linear diabatic solutions must approach as discussed above
Magnetostatic calculation of fringing field for the Rogowski pole boundary with floating snake
Energy Technology Data Exchange (ETDEWEB)
Chen, Yan; Ming-Wu, Fan [Institute of Atomic Energy, Peking (China)
1984-01-01
A boundary integral method has been used to calculate the fringing field distribution of Rogowski pole boundary with floating snake for QMG2 type of QDDD magnetic spectrograph and the experimental EFB is nearly reproduced from BIM calculation. As a further criteria, a calculation for clamped Rogowski pole but without snake is also performed and the calculated EFB shows perfect identity with the experiment. For evaluating the effect of snake quantitatively, this work also predicts the EFB values for two different positions of snake.
Magnetostatic coupling of 90 domain walls in FeNi/Cu/Co trilayers
Energy Technology Data Exchange (ETDEWEB)
Kurde, Julia; Miguel, Jorge; Kuch, Wolfgang [Freie Universitaet, Berlin (Germany); Bayer, Daniela; Aeschlimann, Martin [Technische Universitaet, Kaiserslautern (Germany); Sanchez-Barriga, Jaime; Kronast, Florian; Duerr, Herrmann A. [Helmholtz-Zentrum Berlin fuer Materialien und Energie (Germany)
2011-07-01
The magnetic interlayer coupling of FeNi/Cu/Co trilayered microstructures has been studied by means of X-ray magnetic circular dichroism in combination with photoelectron emission microscopy (XMCD-PEEM). We find that a parallel coupling between magnetic domains coexists with a non-parallel coupling between magnetic domain walls of each ferromagnetic layer. We attribute the non-parallel coupling of the two magnetic layers to local magnetic stray fields arising at domain walls in the magnetically harder Co layer. In the magnetically softer FeNi layer non-ordinary domain walls such as 270 and 90 domain walls with overshoot of the magnetization either inwards or outwards relative to the turning direction of the Co magnetization are identified. Micromagnetic simulations reveal that in the absence of magnetocrystalline anisotropy, both types of overshooting domain walls are energetically equivalent. However, if a uniaxial in-plane anisotropy is present, the relative orientation of the domain walls with respect to the anisotropy axis determines which of these domain walls is energetically favorable.
Influence of magnetostatic interactions on the magnetization reversal of patterned magnetic elements
International Nuclear Information System (INIS)
Yin Xioalu; Liou, S. H.; Adeyeye, A. O.; Jain, S.; Han Baoshan
2011-01-01
The magnetization reversal in patterned thin-film arrays of elliptical submicron permalloy elements has been investigated by magnetic-force microscopy and micro-magneto-optic Kerr effect. Three different spatial arrangements of chains are considered, namely chains aligned parallel to the long axis of the ellipse, chains aligned parallel to the short axis of the ellipse, and arrays with roughly equal element-to-element spacings in both directions. Comparison of the hysteresis loops in an in-plane field perpendicular to the ellipses' long axes shows that the magnetization reversibility is highest for chains along the long axis. This is due to the nearly coherent magnetization rotation in the applied magnetic field and to the formation of a head-to-tail domain arrangement. Other arrangements, such as chains of ellipses aligned parallel to short axis, yield flux-closure domains as the applied magnetic field is changed.
The influence of magnetostatic interactions in exchange-coupled composite particles
Czech Academy of Sciences Publication Activity Database
Vokoun, David; Beleggia, M.; De Graef, M.; Hou, H.C.; Lai, C.H.
2010-01-01
Roč. 43, č. 27 (2010), s. 275001-275007 ISSN 0022-3727 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic recording materials * magnetic multilayers * magnetic thin film * magnetostac interaction * magnetic anisotropy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.105, year: 2010 http://iopscience.iop.org/0022-3727/43/27/275001/
International Nuclear Information System (INIS)
Saito, A; Kuroishi, M; Nakai, H
2016-01-01
This paper concerns the noise and structural vibration caused by rotating electric machines. Special attention is given to the magnetic-force induced vibration response of interior-permanent magnet machines. In general, to accurately predict and control the vibration response caused by the electric machines, it is inevitable to model not only the magnetic force induced by the fluctuation of magnetic fields, but also the structural dynamic characteristics of the electric machines and surrounding structural components. However, due to complicated boundary conditions and material properties of the components, such as laminated magnetic cores and varnished windings, it has been a challenge to compute accurate vibration response caused by the electric machines even after their physical models are available. In this paper, we propose a highly-accurate vibration prediction method that couples experimentally-obtained discrete structural transfer functions and numerically-obtained distributed magnetic-forces. The proposed vibration synthesis methodology has been applied to predict vibration responses of an interior permanent magnet machine. The results show that the predicted vibration response of the electric machine agrees very well with the measured vibration response for several load conditions, for wide frequency ranges. (paper)
Exact Travelling Wave Solutions for Isothermal Magnetostatic Atmospheres by Fan Subequation Method
Directory of Open Access Journals (Sweden)
Hossein Jafari
2012-01-01
ignorable coordinate corresponding to a uniform gravitational field in a plane geometry is carried out. These equations transform to a single nonlinear elliptic equation for the magnetic vector potential . This equation depends on an arbitrary function of that must be specified. With choices of the different arbitrary functions, we obtain analytical solutions of elliptic equation using the Fan subequation method.
End-compensated magnetostatic cavity for polarized 3He neutron spin filters.
McIver, J W; Erwin, R; Chen, W C; Gentile, T R
2009-06-01
We have expanded upon the "Magic Box" concept, a coil driven magnetic parallel plate capacitor constructed out of mu-metal, by introducing compensation sections at the ends of the box that are tuned to limit end-effects similar to those of short solenoids. This ability has reduced the length of the magic box design without sacrificing any loss in field homogeneity, making the device far more applicable to the often space limited neutron beam line. The appeal of the design beyond affording longer polarized 3He lifetimes is that it provides a vertical guide field, which facilitates neutron spin transport for typical polarized beam experiments. We have constructed two end-compensated magic boxes of dimensions 28.4 x 40 x 15 cm3 (length x width x height) with measured, normalized volume-averaged transverse field gradients ranging from 3.3 x 10(-4) to 6.3 x 10(-4) cm(-1) for cell sizes ranging from 8.1 x 6.0 to 12.0 x 7.9 cm2 (diameter x length), respectively.
International Nuclear Information System (INIS)
Vakulenko, M.O.
1992-01-01
Within the general renormalized statistical approach, the low-frequency short-wave stationary spectra of potential and magnetic perturbations in a finite-pressure plasma, are obtained. Anomalous heat conductivity considerably enhances due to non-linear interaction between magnetic excitations. 11 refs. (author)
Magneto-static Modeling of the Mixed Plasma Beta Solar Atmosphere Based on Sunrise/IMaX Data
Czech Academy of Sciences Publication Activity Database
Wiegelmann, T.; Neukirch, A.J.; Nickeler, Dieter Horst; Solanki, S.K.; Martinez Pillet, V.; Borrero, J.M.
2015-01-01
Roč. 815, č. 1 (2015), 10/1-10/6 ISSN 0004-637X R&D Projects: GA ČR GA13-24782S Institutional support: RVO:67985815 Keywords : numerical methods * Sun chromosphere * Sun corona Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 5.909, year: 2015
Bang, Wonbae; Lim, Jinho; Trossman, Jonathan; Tsai, C. C.; Ketterson, John B.
2018-06-01
We have observed the propagation of spin waves across a thin yttrium iron garnet film on (1 1 1) gadolinium gallium garnet for magnetic fields inclined with respect to the film plane. Two principle planes were studied: that for H in the plane defined by the wave vector k and the plane normal, n, with limiting forms corresponding to the Backward Volume and Forward Volume modes, and that for H in the plane perpendicular to k, with limiting forms corresponding to the Damon-Eshbach and Forward Volume modes. By exciting the wave at one edge of the film and observing the field dependence of the phase of the received signal at the opposing edge we determined the frequency vs. wavevector relation, ω = ω (k), of various propagating modes in the film. Avoided crossings are observed in the Damon-Eshbach and Forward Volume regimes when the propagating mode intersects the higher, exchange split, volume modes, leading to an extinction of the propagating mode; analysis of the resulting behavior allows a determination of the exchange parameter. The experimental results are compared with theoretical simulations.
Magneto-static Modeling from SUNRISE/IMaX: Application to an Active Region Observed with SUNRISE II
Czech Academy of Sciences Publication Activity Database
Wiegelmann, T.; Neukirch, A.J.; Nickeler, Dieter Horst; Solanki, S.K.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; Riethmueller, T.L.; van Noort, M.; Blanco Rodriguez, J.; del Toro Iniesta, J.C.; Orozco Suárez, D.; Schmidt, W.; Pillet, V.M.; Knolker, M.
2017-01-01
Roč. 229, č. 1 (2017), 18/1-18/12 ISSN 0067-0049 R&D Projects: GA ČR(CZ) GA16-05011S; GA ČR(CZ) GA16-13277S Institutional support: RVO:67985815 Keywords : Sun * chromosphere * corona Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 8.955, year: 2016
International Nuclear Information System (INIS)
Challeton, Didier
1970-07-01
Device applications of cylindrical magnetic domains - sometimes referred to as 'bubbles' - was first demonstrated by A.H. Bobeck in the rare earth ortho-ferrites. General magnetic and optical properties of the rare earth ortho-ferrites are considered. The theoretical study of the cylindrical magnetic domains and their stability conditions are presented in this paper. The single crystals were grown by the PbO flux method. The thin platelets (≅ 50 microns thick) preparation is specified and the magneto-optical measurements are presented. Absorption, birefringence and Faraday rotation were measured in HoFeO 3 and DyFeO 3 . The utilisation conditions of these materials are characterized by the measurements of the smallest stable domain diameter. (author) [fr
Magnetostatic coupling of 90{sup 0} domain walls in Fe{sub 19}Ni{sub 81}/Cu/Co trilayers
Energy Technology Data Exchange (ETDEWEB)
Kurde, J; Miguel, J; Kuch, W [Institut fuer Experimentalphysik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin-Dahlem (Germany); Bayer, D; Aeschlimann, M [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Sanchez-Barriga, J; Kronast, F; Duerr, H A, E-mail: julia.kurde@fu-berlin.de [Helmholtz-Zentrum Berlin fuer Materialien und Energie, Elektronenspeicherring BESSY II, Albert-Einstein-Strasse 15, 12489 Berlin (Germany)
2011-03-15
The magnetic interlayer coupling of Fe{sub 19}Ni{sub 81}/Cu/Co trilayered microstructures has been studied by means of x-ray magnetic circular dichroism in combination with photoelectron emission microscopy (XMCD-PEEM). We find that a parallel coupling between magnetic domains coexists with a non-parallel coupling between magnetic domain walls (DWs) of each ferromagnetic layer. We attribute the non-parallel coupling of the two magnetic layers to local magnetic stray fields arising at DWs in the magnetically harder Co layer. In the magnetically softer FeNi layer, non-ordinary DWs, such as 270{sup 0} and 90{sup 0} DWs with overshoot of the magnetization either inwards or outwards relative to the turning direction of the Co magnetization, are identified. Micromagnetic simulations reveal that in the absence of magnetic anisotropy, both types of overshooting DWs are energetically equivalent. However, if a uniaxial in-plane anisotropy is present, the relative orientation of the DWs with respect to the anisotropy axis determines which of these DWs is energetically favorable.
Czech Academy of Sciences Publication Activity Database
Stachiv, Ivo
2014-01-01
Roč. 115, č. 21 (2014), "214310-1"-"214310-7" ISSN 0021-8979 R&D Projects: GA ČR GAP107/12/0800 Institutional support: RVO:68378271 Keywords : suspended nanomechanical resonators * mass sensors Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.183, year: 2014
Generalization of the Biot--Savart law to Maxwell's equations using special relativity
International Nuclear Information System (INIS)
Neuenschwander, D.E.; Turner, B.N.
1992-01-01
Maxwell's equations are obtained by generalizing the laws of magnetostatics, which follow from the Biot--Savart law and superposition, to be consistent with special relativity. The Lorentz force on a charged particle and its rate of energy change also follow by making Newton's second law for a particle in a magnetostatic field consistent with special relativity
Vortex precession in thin elliptical ferromagnetic nanodisks
Energy Technology Data Exchange (ETDEWEB)
Zaspel, C.E., E-mail: craig.zaspel@umwestern.edu
2017-07-01
Highlights: • A general form for the magnetostatic energy is calculated for the vortex state in a ferromagnetic ellipse. • The ellipse magnetostatic energy is minimized by conformal mapping the circular disk onto the ellipse. • The gyrotropic precession frequency is obtained in general for a range of ellipticities. - Abstract: The magnetostatic energy is calculated for a magnetic vortex in a noncircular elliptical nanodisk. It is well-known that the energy of a vortex in the circular disk is minimized though an ansatz that eliminates the magnetostatic charge at the disk edge. Beginning with this ansatz for the circular disk, a conformal mapping of a circle interior onto the interior of an ellipse results in the magnetization of the elliptical disk. This magnetization in the interior of an ellipse also has no magnetostatic charge at the disk edge also minimizing the magnetostatic energy. As expected the energy has a quadratic dependence on the displacement of the vortex core from the ellipse center, but reflecting the lower symmetry of the ellipse. Through numerical integration of the magnetostatic integral a general expression for the energy is obtained for ellipticity values from 1.0 to about 0.3. Finally a general expression for the gyrotropic frequency as described by the Thiele equation is obtained.
Magnetic fields, special relativity and potential theory elementary electromagnetic theory
Chirgwin, B H; Kilmister, C W
1972-01-01
Magnetic Fields, Special Relativity and Potential Theory is an introduction to electromagnetism, special relativity, and potential theory, with emphasis on the magnetic field of steady currents (magnetostatics). Topics covered range from the origin of the magnetic field and the magnetostatic scalar potential to magnetization, electromagnetic induction and magnetic energy, and the displacement current and Maxwell's equations. This volume is comprised of five chapters and begins with an overview of magnetostatics, followed by a chapter on the methods of solving potential problems drawn from elec
Vaseem, Mohammad; Ghaffar, Farhan A.; Farooqui, Muhammad Fahad; Shamim, Atif
2018-01-01
. Functionalized iron oxide nanoparticles are successfully embedded in the SU8 matrix to make a magnetic substrate. The as-fabricated substrate is characterized for its magnetostatic and microwave properties. A frequency tunable printed patch antenna
Magnetic and microscopic characterization of magnetite nanoparticles adhered to clay surfaces
DEFF Research Database (Denmark)
Galindo-Gonzalez, C; Feinberg, JM; Kasama, Takeshi
2009-01-01
samples behave superparamagnetically at room temperature, and show increasing levels of single domain behavior as the samples are cooled to liquid nitrogen temperatures. At such low temperatures, magnetostatic interactions are observed to partially stabilize otherwise superparamagnetic grains in flux...
Variations of helicon wave induced radial plasma transport in different experimental conditions
International Nuclear Information System (INIS)
Petrzilka, V.
1993-08-01
Variations of the helicon wave induced radial plasma transport are presented in dependence on values of the plasma radius, magnetostatic field, plasma density, frequency of the helicon wave and on the ion charge. 22 refs., 14 figs
Electric and magnetic mirrors and grating for slowly moving neutral atoms and molecules
International Nuclear Information System (INIS)
Opat, G.I.; Washington Univ., Seattle, WA; Wark, S.J.; Hajnal, J.V.; Cimmino, A.
1990-01-01
Those atoms or molecules which happen to have positive Stark or Zeeman energies (by virtue of their internal quantum state) are repelled by regions of high electrostatic or magnetostatic energy density, respectively. Using electrostatic or magnetostatic fields, which are periodic in a plane, it is possible to construct mirrors and gratings for slowly moving atoms and molecules. The theory of such devices is presented, together with some ideas for their fabrication. 10 refs., 4 figs
A magnetic vector potential corresponding to a centrally conservative current element force
International Nuclear Information System (INIS)
Minteer, Timothy M
2015-01-01
The magnetic vector potential (Coulomb gauge) is commonly introduced in magnetostatic chapters of electromagnetism textbooks. However, what is not typically presented are the infinite subsets of the Coulomb gauge associated with differential current elements. This work provides a comparison of various differential magnetic vector potentials, differential magnetostatic potential energies, as well as differential current element forces as a collective work not available elsewhere. The differential magnetic vector potential highlighted in this work is the Coulomb–Ampère gauge corresponding to the centrally conservative Ampère current element force. The centrally conservative force is modeled as a mean valued continual exchange of energy carrier mediators accounting for both the differential magnetostatic potential energy and Ampère current element force of two differential current elements. (paper)
Quasi-linear theory and transport theory. [particle acceleration in interplanetary medium
Smith, Charles W.
1992-01-01
The theory of energetic particle scattering by magnetostatic fluctuations is reviewed in so far as it fails to produce the rigidity-independent mean-free-paths observed. Basic aspects of interplanetary magnetic field fluctuations are reviewed with emphasis placed on the existence of dissipation range spectra at high wavenumbers. These spectra are then incorporated into existing theories for resonant magnetostatic scattering and are shown to yield infinite mean-free-paths. Nonresonant scattering in the form of magnetic mirroring is examined and offered as a partial solution to the magnetostatic problem. In the process, mean-free-paths are obtained in good agreement with observations in the interplanetary medium at 1 AU and upstream of planetary bow shocks.
Energy Technology Data Exchange (ETDEWEB)
Komine, Takashi, E-mail: komine@mx.ibaraki.ac.jp; Aono, Tomosuke [Faculty of Engineering, Ibaraki University 4-12-1, Nakanarusawa, Hitachi, Ibaraki, 316-8511 (Japan)
2016-05-15
We demonstrate current-induced domain wall motion in bilayer nanowire with synthetic antiferromagnetic (SAF) coupling by modeling two body problems for motion equations of domain wall. The influence of interlayer exchange coupling and magnetostatic interactions on current-induced domain wall motion in SAF nanowires was also investigated. By assuming the rigid wall model for translational motion, the interlayer exchange coupling and the magnetostatic interaction between walls and domains in SAF nanowires enhances domain wall speed without any spin-orbit-torque. The enhancement of domain wall speed was discussed by energy distribution as a function of wall angle configuration in bilayer nanowires.
Magnetic guns with cylindrical permanent magnets
DEFF Research Database (Denmark)
Vokoun, David; Beleggia, Marco; Heller, Luděk
2012-01-01
The motion of a cylindrical permanent magnet (projectile) inside a tubular permanent magnet, with both magnets magnetized axially, illustrates nicely the physical principles behind the operation of magnetic guns. The force acting upon the projectile is expressed semi-analytically as derivative...... of the magnetostatic interaction energy. For comparison, the forces involved are also calculated numerically using finite elements methods. Based on the conservation of the magnetostatic and kinetic energies, the exit and asymptotic velocities are determined. The derived formulas can be used to optimize the generated...... forces and motion of the inner cylindrical magnet....
Some economic aspects of rare-earth permanent magnets
International Nuclear Information System (INIS)
Zijlstra, H.
1978-01-01
The commercial feasibility of RE permanent magnets is analyzed in terms of price per unit of magnetostatic energy. The availability of the raw materials is also taken into consideration. The conclusion is that RE magnets are and remain relatively expensive as compared with other permanent magnets, and will find only limited application. (author)
Accurate magnetic field calculations for contactless energy transfer coils
Sonntag, C.L.W.; Spree, M.; Lomonova, E.A.; Duarte, J.L.; Vandenput, A.J.A.
2007-01-01
In this paper, a method for estimating the magnetic field intensity from hexagon spiral windings commonly found in contactless energy transfer applications is presented. The hexagonal structures are modeled in a magneto-static environment using Biot-Savart current stick vectors. The accuracy of the
International Nuclear Information System (INIS)
Fuentes Cobas, L.E.; Font Hernandez, R.
1993-01-01
An analytical treatment of electrostatic and magnetostatic field symmetry, as a function of charge and current distribution symmetry, is proposed. The Newmann Principle, related to the cause-effect symmetry relation, is presented and applied to the characterization of simple configurations. (Author) 5 refs
Symmetry and electromagnetism. Simetria y electromagnetismo
Energy Technology Data Exchange (ETDEWEB)
Fuentes Cobas, L.E.; Font Hernandez, R.
1993-01-01
An analytical treatment of electrostatic and magnetostatic field symmetry, as a function of charge and current distribution symmetry, is proposed. The Newmann Principle, related to the cause-effect symmetry relation, is presented and applied to the characterization of simple configurations. (Author) 5 refs.
Ten years of born and infeld electrodynamics investigations
Energy Technology Data Exchange (ETDEWEB)
Vellozo, Sergio O. [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil); Helayel Neto, Jose Abdala [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Assis, Leonardo P. G. De [Stanford University (United States); Gaete, Patricio [U.S.M. (Chile)
2013-07-01
Full text: In this year, our group celebrates ten years of incursions in four-dimensional (3+1) Born and Infeld Electrodynamics (BIE). As is well known, BIE is a classical and nonlinear theory and it predicts a maximum finite value for the electric field, preventing the occurrence of classical singularities. It gives also finite energy for a point-like electric charge. In this period, our main effort was on BIE magnetic sector and the most significant results were: 1. the finite and well behaved magnetostatic field solution for a point-like electric charge at rest, 2. the intrinsic angular momentum (spin) as a self interaction among electric and magnetic field, 3. the cohesive resultant force, using the same natural and simple mechanism, giving stability to the electric charge. Another BIE incursion line stands for three-dimensional (2+1). We investigated the consequences of the space-time dimensionality on the existence of magnetostatic fields generated by electric charges at rest in an inertial frame, which were present in our four-dimensional version. A magnetostatic field associated with an electric charge at rest does not appear in this case. Interestingly, the addition of the topological term (Chern-Simons) to BIE yields the appearance of the magnetostatic field. Finally, we are looking for the hydrogen-like atom spectrum under the BI electrostatic potential, as well the muonic atom spectrum. (author)
Convergence analysis of spectral element method for electromechanical devices
Curti, M.; Jansen, J.W.; Lomonova, E.A.
2017-01-01
This paper concerns the comparison of the performance of the Spectral Element Method (SEM) and the Finite Element Method (FEM) for a magnetostatic problem. The convergence of the vector magnetic potential, the magnetic flux density, and the total stored energy in the system is compared with the
Modeling, design and experimental validation of a small-sized magnetic gear
Zanis, R.; Borisavljevic, A.; Jansen, J.W.; Lomonova, E.A.
2013-01-01
A magnetostatic analytical model is created to analyze and design a small-sized magnetic gear for a robotic application. Through a parameter variation study, it is found that the inner rotor magnet height is highly influential to the torque, and based on which, the design is performed. Several
Nature-inspired microfluidic propulsion using magnetic actuation
Khaderi, S. N.; Baltussen, M. G. H. M.; Anderson, P. D.; Ioan, D.; den Toonder, J.M.J.; Onck, P. R.
In this work we mimic the efficient propulsion mechanism of natural cilia by magnetically actuating thin films in a cyclic but non-reciprocating manner. By simultaneously solving the elastodynamic, magnetostatic, and fluid mechanics equations, we show that the amount of fluid propelled is
Nature-inspired microfluidic propulsion using magnetic actuation
Khaderi, S.N.; Baltussen, M.G.H.M.; Anderson, P.D.; Ioan, D.; Toonder, den J.M.J.; Onck, P.R.
2009-01-01
In this work we mimic the efficient propulsion mechanism of natural cilia by magnetically actuating thin films in a cyclic but non-reciprocating manner. By simultaneously solving the elastodynamic, magnetostatic, and fluid mechanics equations, we show that the amount of fluid propelled is
Electronic, magnetic, and optical materials
Fulay, Pradeep
2013-01-01
Technological aspects of ferroelectric, piezoelectric and pyroelectric materials are discussed in detail, in a way that should allow the reader to select an optimal material for a particular application. The basics of magnetostatics are described clearly, as are a wide range of magnetic properties of materials … .-Tony Harker, Department of Physics and Astronomy, University College London
Domain configuration and magnetization switching in arrays of permalloy nanostripes
International Nuclear Information System (INIS)
Iglesias-Freire, Ó.; Jaafar, M.; Pérez, L.; Abril, O. de; Vázquez, M.; Asenjo, A.
2014-01-01
The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm. - Highlights: • A shape anisotropy-induced single domain remanent state is present in the stripes. Closure domains are formed under external fields. • Separation distances between neighboring stripes (500 nm) are enough to overcome the magnetostatic coupling and avoid a multi-stripe character. • Micromagnetic simulations predict critical distances of around 500 nm for the onset of magnetostatic coupling between neighboring elements. • Simulations predict stripes with a small longitudinal separation to behave as single elements, with domain walls “jumping” between them
New design on air-core resistive NMR imaging magnet
Energy Technology Data Exchange (ETDEWEB)
Chen, Yan; Mingwu, Fan; Yixin, Miao
1984-08-01
A new type of NMR imaging air-core resistive magnet is designed. Based on the BIM Magnetostatic calculation the resultant four equiradial coils structure with optimized shapes of cross section possesses a larger spherical working volume obviously, comparing with the common four-coils imaging magnet. The manufacturing tolerance is also calculated.
Forces Between a Permanent Magnet and a Soft Magnetic Plate
DEFF Research Database (Denmark)
Beleggia, Marco; Vokoun, David; De Graef, Marc
2012-01-01
Forces between a hard/permanent magnet of arbitrary shape and an ideally soft magnetic plate in close proximity are derived analytically from the image method applied to magnetostatics. We found that the contact force, defined as the force required to detach the hard magnet from the plate, coinci...
Introduction to Electrodynamics
Griffiths, David J.
2017-06-01
1. Vector analysis; 2. Electrostatics; 3. Potentials; 4. Electric fields in matter; 5. Magnetostatics; 6. Magnetic fields in matter; 7. Electrodynamics; 8. Conservation laws; 9. Electromagnetic waves; 10. Potentials and fields; 11. Radiation; 12. Electrodynamics and relativity; Appendix A. Vector calculus in curvilinear coordinates; Appendix B. The Helmholtz theorem; Appendix C. Units; Index.
Magnetic saturation in semi-analytical harmonic modeling for electric machine analysis
Sprangers, R.L.J.; Paulides, J.J.H.; Gysen, B.L.J.; Lomonova, E.
2016-01-01
A semi-analytical method based on the harmonic modeling (HM) technique is presented for the analysis of the magneto-static field distribution in the slotted structure of rotating electric machines. In contrast to the existing literature, the proposed model does not require the assumption of infinite
Convergence analysis of spectral element method for magnetic devices
Curti, M.; Jansen, J.W.; Lomonova, E.A.
2018-01-01
This paper concerns the comparison of the performance of the Spectral Element Method (SEM) and the Finite Element Method (FEM) for modeling a magnetostatic problem. The convergence of the vector magnetic potential, the magnetic flux density, and the total stored energy in the system is compared with
Magnetic Interactions and the Method of Images: A Wealth of Educational Suggestions
Bonanno, A.; Camarca, M.; Sapia, P.
2011-01-01
Under some conditions, the method of images (well known in electrostatics) may be implemented in magnetostatic problems too, giving an excellent example of the usefulness of formal analogies in the description of physical systems. In this paper, we develop a quantitative model for the magnetic interactions underlying the so-called Geomag[TM]…
DEFF Research Database (Denmark)
Astorino, Antonio; Romano, D.; Antonini, G.
2018-01-01
In this paper, a fast H(M) magnetostatic hysteresis model is presented, tested, and used in Simulink and partial element equivalent circuit (PEEC) environments. The model is primarily designed to achieve full compatibility with the current 3-D PEEC formalism for nonlinear isotropic magnetic...
Effect of changing the pole profile in a gradient septum magnet
International Nuclear Information System (INIS)
Armstrong, A.G.A.M.
1977-05-01
A tapered-pole gradient septum magnet was fitted with wedge-shaped shims to make the gap parallel. The resulting field was measured and compared with the predicted field from the GFUN magnetostatic computer program. A method of estimating the beam loss due to kick non-uniformity is presented. (author)
Domain configuration and magnetization switching in arrays of permalloy nanostripes
Energy Technology Data Exchange (ETDEWEB)
Iglesias-Freire, Ó., E-mail: aasenjo@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, Madrid 28049 (Spain); Jaafar, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, Madrid 28049 (Spain); Dpto. Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco 28049 (Spain); Pérez, L. [Dpto. Física de Materiales, Universidad Complutense de Madrid, Madrid 28040 (Spain); Abril, O. de [Dpto. Física e Instalaciones Aplicadas a la Edificación, al Medio Ambiente y al Urbanismo, Universidad Politécnica de Madrid, Madrid 28040 (Spain); Vázquez, M.; Asenjo, A. [Instituto de Ciencia de Materiales de Madrid, CSIC, Sor Juana Inés de la Cruz 3, Madrid 28049 (Spain)
2014-04-15
The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm. - Highlights: • A shape anisotropy-induced single domain remanent state is present in the stripes. Closure domains are formed under external fields. • Separation distances between neighboring stripes (500 nm) are enough to overcome the magnetostatic coupling and avoid a multi-stripe character. • Micromagnetic simulations predict critical distances of around 500 nm for the onset of magnetostatic coupling between neighboring elements. • Simulations predict stripes with a small longitudinal separation to behave as single elements, with domain walls “jumping” between them.
A half mode inkjet printed tunable ferrite isolator
Ghaffar, Farhan A.; Vaseem, Mohammed; Bray, Joey. R.; Shamim, Atif
2017-01-01
. The isolation band can be controlled by changing the applied magnetostatic bias. As the bias is varied from 1500 Oe to 3500 Oe the center frequency of the isolation band varies from 4.45 GHz to 9 GHz. The measured response of the isolator shows that it can
On the resonant state of magnetization in array of interacting nanodots
Kim, P. D.; Orlov, V. A.; Rudenko, R. Yu.; Prokopenko, V. S.; Orlova, I. N.; Kobyakov, A. V.
2017-10-01
Development of the interpretation of the phenomenon of the lift of the magnetic resonance frequencies degeneracy caused by the magnetostatic interaction in assemblies of nanodisks has been done. The difference of the resonance behavior of magnetic vortexes in a round and rectangular nanodots has been studied experimentally and explained.
On radio frequency wave induced radial transport and wave helicity
International Nuclear Information System (INIS)
Petrzilka, V.
1992-09-01
Expressions for wave induced radial transport are derived allowing simple estimates. The transport is enhanced due to the presence of poloidal magnetostatic field and in the vicinity of the ion cyclotron resonance. The direction of the wave induced transport depends also on the wave polarization. (author) 19 refs
International Nuclear Information System (INIS)
Eloranta, E.
2003-11-01
The geophysical field theory includes the basic principles of electromagnetism, continuum mechanics, and potential theory upon which the computational modelling of geophysical phenomena is based on. Vector analysis is the main mathematical tool in the field analyses. Electrostatics, stationary electric current, magnetostatics, and electrodynamics form a central part of electromagnetism in geophysical field theory. Potential theory concerns especially gravity, but also electrostatics and magnetostatics. Solid state mechanics and fluid mechanics are central parts in continuum mechanics. Also the theories of elastic waves and rock mechanics belong to geophysical solid state mechanics. The theories of geohydrology and mass transport form one central field theory in geophysical fluid mechanics. Also heat transfer is included in continuum mechanics. (orig.)
Directory of Open Access Journals (Sweden)
Juan J. Soto-Bernal
2015-01-01
Full Text Available This paper presents the results of an experimental study carried out to comprehend the physical, mechanical, and microstructural behavior of cement pastes subjected to static magnetic fields while hydrating and setting. The experimental methodology consisted in exposing fresh cement pastes to static magnetic fields at three different magnetic induction strengths: 19.07, 22.22, and 25.37 Gauss. The microstructural characterization makes evident that there are differences in relation to amount and morphology of CSH gel; the amount of CSH is larger and its morphology becomes denser and less porous with higher magnetostatic induction strengths; it also shows the evidence of changes in the mineralogical composition of the hydrated cement pastes. The temperature increasing has no negative effects over the cement paste compressive strength since the magnetostatic field affects the process of hydration through a molecular restructuring process, which makes cement pastes improve microstructurally, with a reduced porosity and a higher mechanical strength.
Topology of plasma equilibria and the current closure condition
International Nuclear Information System (INIS)
Kocic, S.; Mahajan, S.M.; Hazeltine, R.D.
2005-01-01
A virtually complete description of the topology of stationary incompressible Euler flows and the magnetic field satisfying the magnetostatic equation is given by a theorem due to Arnol'd. We apply this theorem to describe the topology of stationary states of plasmas with significant fluid flow, obeying the Hall magnetohydrodynamics model equations. In the context of the integrability (nonchaotic topology) of the magnetic and velocity fields, we discuss the validity of conditions analogous to that of Greene and Johnson, which, in the case of magnetostatic equations, states that the line integral ∫dl/B is the same for each closed magnetic field line on a given magnetic surface. We also show how this property follows from the existence of a continuous volume-preserving symmetry of the magnetic field
Chaotic parametric soliton-like pulses in ferromagnetic-film active ring resonators
International Nuclear Information System (INIS)
Grishin, S. V.; Golova, T. M.; Morozova, M. A.; Romanenko, D. V.; Seleznev, E. P.; Sysoev, I. V.; Sharaevskii, Yu. P.
2015-01-01
The generation of quasi-periodic sequences of parametric soliton-like pulses in an active ring resonator with a ferromagnetic film via the three-wave parametric instability of a magnetostatic surface wave is studied theoretically and experimentally. These dissipative structures form in time due to the competition between the cubic nonlinearity caused by parametric coupling between spin waves and the time dispersion caused by the resonant cavity that is present in a self-oscillatory system. The development of dynamic chaos due to the parametric instability of a magnetostatic surface wave results in irregular behavior of a phase. However, this behavior does not break a quasi-periodic pulse sequence when the gain changes over a wide range. The generated soliton-like pulses have a chaotic nature, which is supported by the maximum Lyapunov exponent estimated from experimental time series
Wang, R.; Demerdash, N. A.
1991-01-01
A method of combined use of magnetic vector potential based finite-element (FE) formulations and magnetic scalar potential (MSP) based formulations for computation of three-dimensional magnetostatic fields is introduced. In this method, the curl-component of the magnetic field intensity is computed by a reduced magnetic vector potential. This field intensity forms the basic of a forcing function for a global magnetic scalar potential solution over the entire volume of the region. This method allows one to include iron portions sandwiched in between conductors within partitioned current-carrying subregions. The method is most suited for large-scale global-type 3-D magnetostatic field computations in electrical devices, and in particular rotating electric machinery.
ON THE ROLE OF REPETITIVE MAGNETIC RECONNECTIONS IN EVOLUTION OF MAGNETIC FLUX ROPES IN SOLAR CORONA
Energy Technology Data Exchange (ETDEWEB)
Kumar, Sanjay; Bhattacharyya, R.; Joshi, Bhuwan [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)
2016-10-20
Parker's magnetostatic theorem, extended to astrophysical magnetofluids with large magnetic Reynolds number, supports ceaseless regeneration of current sheets and, hence, spontaneous magnetic reconnections recurring in time. Consequently, a scenario is possible where the repeated reconnections provide an autonomous mechanism governing emergence of coherent structures in astrophysical magnetofluids. In this work, such a scenario is explored by performing numerical computations commensurate with the magnetostatic theorem. In particular, the computations explore the evolution of a flux rope governed by repeated reconnections in a magnetic geometry resembling bipolar loops of solar corona. The revealed morphology of the evolution process—including onset and ascent of the rope, reconnection locations, and the associated topology of the magnetic field lines—agrees with observations, and thus substantiates physical realizability of the advocated mechanism.
Three dimensional field computation software package DE3D and its applications
International Nuclear Information System (INIS)
Fan Mingwu; Zhang Tianjue; Yan Weili
1992-07-01
A software package, DE3D that can be run on PC for three dimensional electrostatic and magnetostatic field analysis has been developed in CIAE (China Institute of Atomic Energy). Two scalar potential method and special numerical techniques have made the code with high precision. It can be used for electrostatic and magnetostatic fields computations with complex boundary conditions. In the most cases, the result accuracy is better than 1% comparing with the measured. In some situations, the results are more acceptable than the other codes because some tricks are used for the current integral. Typical examples, design of a cyclotron magnet and magnetic elements on its beam transport line, given in the paper show how the program helps the designer to improve the design of the product. The software package could bring advantages to the producers and designers
Energy Technology Data Exchange (ETDEWEB)
Gammon, M.; Shalchi, A., E-mail: andreasm4@yahoo.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)
2017-10-01
In several astrophysical applications one needs analytical forms of cosmic-ray diffusion parameters. Some examples are studies of diffusive shock acceleration and solar modulation. In the current article we explore perpendicular diffusion based on the unified nonlinear transport theory. While we focused on magnetostatic turbulence in Paper I, we included the effect of dynamical turbulence in Paper II of the series. In the latter paper we assumed that the temporal correlation time does not depend on the wavenumber. More realistic models have been proposed in the past, such as the so-called damping model of dynamical turbulence. In the present paper we derive analytical forms for the perpendicular diffusion coefficient of energetic particles in two-component turbulence for this type of time-dependent turbulence. We present new formulas for the perpendicular diffusion coefficient and we derive a condition for which the magnetostatic result is recovered.
A self-biased 3D tunable helical antenna in ferrite LTCC substrate
Ghaffar, Farhan A.; Shamim, Atif
2015-01-01
A ferrite LTCC based helical antenna which also provides magneto-static bias for its frequency tuning is presented in this work. The 3D helical-cum-bias winding design avoids the use of large external electromagnets which are traditionally used with ferrite based tunable antennas. This reduces the overall size of the design while making it efficient by getting rid of demagnetization effect experienced at the air-to-ferrite interface. RF choke and DC blocking capacitor, required to isolate the RF and DC passing through a single structure, are integrated within the multi-layer Ferrite LTCC substrate. Magnetostatic and microwave simulations have been carried out for the design optimization. The prototype antenna demonstrates a tuning range of 10 % around 13 GHz. An optimized design with an air cavity is also presented which reduces the biasing power requirement by 40 %.
Some recent developments in the theoretical dynamics of magnetic fields
International Nuclear Information System (INIS)
Low, B.C.
1986-01-01
This article describes recent developments in the theoretical investigation of magnetostatic equilibrium in the presence of gravity, nonequilibrium in hydromagnetics, and classical problems in hydromagnetic stability. The construction of magnetostatic dequilibria has progressed beyond geometrically idealized systems, such as the axisymmetric system, to fully three-dimensional systems capable of modelling realistic solar structures. Nonequilibrium in a magnetic field with an arbitrary interweaving of lines of force due to random footpoint motion is a novel and subtle property with important implications for the solar atmosphere. To the extent quasi-static solar structures are approximated by stable equilibrium, ideal hydromagnetic stability theory provides a first insight into how stability is achieved in the solar environment. A qualitative physical picture based on recent stability analyses is given. The article places emphasis on understanding basic principles and issues rather than detailed results which can be found in the published literature
Angular beam width of a slit-diffracted wave with noncollinear group and phase velocities
International Nuclear Information System (INIS)
Lock, Edwin H
2012-01-01
Taking magnetostatic surface wave diffraction as an example, this paper theoretically investigates the 2D diffraction pattern arising in the far-field region of a ferrite slab in the case of a plane wave with noncollinear group and phase velocities incident on a wide, arbitrarily oriented slit in an opaque screen. A universal analytical formula for the angular width of a diffracted beam is derived, which is valid for magnetostatic and other types of waves in anisotropic media and structures (including metamaterials) in 2D geometries. It is shown that the angular width of a diffracted beam in an anisotropic medium can not only take values greater or less than λ 0 /D (where λ 0 is the incident wavelength, and D is the slit width), but can also be zero under certain conditions. (methodological notes)
Properties of backward electromagnetic waves and negative reflection in ferrite films
International Nuclear Information System (INIS)
Vashkovsky, Anatolii V; Lock, Edwin H
2006-01-01
For a backward electromagnetic wave (magnetostatic wave) in a ferrite film, reflection from a perfect mirror formed by the straight edge of the film is investigated experimentally and theoretically. It is found that when the incident wave is collinear (the group velocity vector and the wave vector have opposite directions), negative reflection occurs at any angle of incidence, i.e., the incident and reflected beams are on the same side of the normal to the boundary. It is discovered that a noncollinear backward wave is nonreciprocal in the sense that its energy can be localized both near the surface and in the middle of the film. This property, previously observed only for surface magnetostatic waves, provides both the efficiency of generating and receiving the wave and the possibility of observing the reflected beam. A situation is realized where wave reflection results in two reflected beams. The properties of backward electromagnetic waves propagating in ferrite films are briefly analyzed. (methodological notes)
A self-biased 3D tunable helical antenna in ferrite LTCC substrate
Ghaffar, Farhan A.
2015-07-19
A ferrite LTCC based helical antenna which also provides magneto-static bias for its frequency tuning is presented in this work. The 3D helical-cum-bias winding design avoids the use of large external electromagnets which are traditionally used with ferrite based tunable antennas. This reduces the overall size of the design while making it efficient by getting rid of demagnetization effect experienced at the air-to-ferrite interface. RF choke and DC blocking capacitor, required to isolate the RF and DC passing through a single structure, are integrated within the multi-layer Ferrite LTCC substrate. Magnetostatic and microwave simulations have been carried out for the design optimization. The prototype antenna demonstrates a tuning range of 10 % around 13 GHz. An optimized design with an air cavity is also presented which reduces the biasing power requirement by 40 %.
NUMERICAL SIMULATION OF MAGNETIC FIELD STRUCTURE IN CYLINDRICAL FILM SCREEN
Directory of Open Access Journals (Sweden)
G. F. Gromyko
2016-01-01
Full Text Available A numerical method for solving the boundary value problem for a nonlinear magnetostatic equation describing the external magnetostatic field penetration through the cylindrical film coating is developed. A mathematical model of the shielding problem based on the use of the boundary conditions of the third kind on the film surface is studied. The nonlinear dependence of the film magnetic permeability on magnetic field conforms with experimental data. The distribution of the magnetic field strength in the film layer and the magnetic permeability of the film material depending on the magnitude of the external magnetic field strength are investigated numerically.
Morphology, magnetic and resonance properties of Fe/MgO multilayers
International Nuclear Information System (INIS)
Garcia-Garcia, A; Algarabel, P A; Ibarra, M R; Vovk, A; Strichovanec, P; Pardo, J A; Magen, C; Golub, V; Salyuk, O
2011-01-01
Magnetic, resonance and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers prepared by pulsed laser deposition were investigated. Comparison of the data allows conclusions on Fe layers morphology. For t 1.25 nm a continuous coverage of MgO by Fe takes place. However, the morphology of Fe layers is rough. This causes the appearance of magnetostatic resonance modes analogous to those observed for continuous films deposited on embossed surfaces.
International Nuclear Information System (INIS)
Kalita, V.M.; Lozenko, A.F.; Ryabchenko, S.M.; Trotsenko, P.O.; Tovstolitkyin, O.Yi.; Pogoryilij, A.M.
2009-01-01
Magnetostatic properties of a La 0,7 Sr 0,3 MnO 3 single crystal have been studied in the vicinity of its critical temperature T c . A nonlinear temperature dependence of the inverse magnetic susceptibility which is characteristic of the Griffiths phase, has been found in the minimal measuring magnetic field at temperatures slightly above the temperature of ferromagnetic (FM) ordering. A conclusion was made that such a nonlinearity arises owing to the formation of magnetic polarons
A finite element code for electric motor design
Campbell, C. Warren
1994-01-01
FEMOT is a finite element program for solving the nonlinear magnetostatic problem. This version uses nonlinear, Newton first order elements. The code can be used for electric motor design and analysis. FEMOT can be embedded within an optimization code that will vary nodal coordinates to optimize the motor design. The output from FEMOT can be used to determine motor back EMF, torque, cogging, and magnet saturation. It will run on a PC and will be available to anyone who wants to use it.
Accurate magnetic field calculations for contactless energy transfer coils
Sonntag, C.L.W.; Spree, M.; Lomonova, E.A.; Duarte, J.L.; Vandenput, A.J.A.
2007-01-01
In this paper, a method for estimating the magnetic field intensity from hexagon spiral windings commonly found in contactless energy transfer applications is presented. The hexagonal structures are modeled in a magneto-static environment using Biot-Savart current stick vectors. The accuracy of the models are evaluated by mapping the current sticks and the hexagon spiral winding tracks to a local twodimensional plane, and comparing their two-dimensional magnetic field intensities. The accurac...
Three-dimensional modeling with finite element codes
Energy Technology Data Exchange (ETDEWEB)
Druce, R.L.
1986-01-17
This paper describes work done to model magnetostatic field problems in three dimensions. Finite element codes, available at LLNL, and pre- and post-processors were used in the solution of the mathematical model, the output from which agreed well with the experimentally obtained data. The geometry used in this work was a cylinder with ports in the periphery and no current sources in the space modeled. 6 refs., 8 figs.
International Nuclear Information System (INIS)
Kaplan, I.G.; Rodimova, O.B.; AN SSSR, Tomsk. Inst. Optiki Atmosfery)
1978-01-01
The present state of the intermolecular interaction theory is described. The general physical picture of the molecular interactions is given, the relative contributions of interactions of different types are analyzed (electrostatic, resonance, induction, dispersion, relativistic, magnetostatic and exchange), and the main ones in each range of separations are picked out. The methods of the potential curve calculations are considered, specific for definite separations between the interacting systems. The special attention is paid to the analysis of approximations used in different theoretical calculation methods
International Nuclear Information System (INIS)
Sjoeberg, Daniel
2009-01-01
We present four variational principles for the electric and magnetic polarizabilities for a structure consisting of anisotropic media with perfect electric conductor (PEC) inclusions. From these principles, we derive monotonicity results and upper and lower bounds on the electric and magnetic polarizabilities. When computing the polarizabilities numerically, the bounds can be used as error bounds. The variational principles demonstrate important differences between electrostatics and magnetostatics when PEC bodies are present.
Orbital dynamics in a storage ring with electrostatic bending
International Nuclear Information System (INIS)
Mane, S.R.
2008-01-01
A storage ring where electrostatic fields contribute to the bending and focusing of the orbital motion has some novel features because, unlike a magnetostatic field, an electrostatic field can change the kinetic energy of the particles. I present analytical formulas to calculate the linear focusing gradient, dispersion, momentum compaction and natural chromaticity for a storage ring with a radial electrostatic field. I solve the formulas explicitly for a weak focusing model.
On the equilibrium configuration of the Kittel type domain structure with Bloch walls, l80deg
International Nuclear Information System (INIS)
Gavrila, H.
1975-01-01
Using a phenomenologic method for appreciating different components of the free energy, the equilibrium configuration of the Kittel-type domain structure with Bloch walls is obtained. By improving the known methods, more accurate magnetostatic energy calculations are reported. In order to determine the equilibrium structure, the total free energy is minimized with respect to two system parameters: the Bloch wall width and the structure half-period. (author)
Generation of attosecond electron packets via conical surface plasmon electron acceleration
Greig, S. R.; Elezzabi, A. Y.
2016-01-01
We present a method for the generation of high kinetic energy attosecond electron packets via magnetostatic and aperture filtering of conical surface plasmon (SP) accelerated electrons. The conical SP waves are excited by coupling an ultrafast radially polarized laser beam to a conical silica lens coated with an Ag film. Electromagnetic and particle tracking models are employed to characterize the ultrafast electron packets. PMID:26764129
Three dimensional field computation
International Nuclear Information System (INIS)
Trowbridge, C.W.
1981-06-01
Recent research work carried out at Rutherford and Appleton Laboratories into the Computation of Electromagnetic Fields is summarised. The topics covered include algorithms for integral and differential methods for the solution of 3D magnetostatic fields, comparison of results with experiment and an investigation into the strengths and weaknesses of both methods for an analytic problem. The paper concludes with a brief summary of the work in progress on the solution of 3D eddy currents using differential finite elements. (author)
Stationary axisymmetric Einstein--Maxwell field equations
International Nuclear Information System (INIS)
Catenacci, R.; Diaz Alonso, J.
1976-01-01
We show the existence of a formal identity between Einstein's and Ernst's stationary axisymmetric gravitational field equations and the Einstein--Maxwell and the Ernst equations for the electrostatic and magnetostatic axisymmetric cases. Our equations are invariant under very simple internal symmetry groups, and one of them appears to be new. We also obtain a method for associating two stationary axisymmetric vacuum solutions with every electrostatic known
Magnetic guns with cylindrical permanent magnets
Czech Academy of Sciences Publication Activity Database
Vokoun, David; Beleggia, M.; Heller, Luděk
2012-01-01
Roč. 324, č. 9 (2012), s. 1715-1719 ISSN 0304-8853 R&D Projects: GA ČR(CZ) GAP107/11/0391; GA AV ČR IAA100100920 Institutional research plan: CEZ:AV0Z10100520 Keywords : permanent magnet * cylindrical magnet * Earnshaw's theorem * magnetic gun * magnetostatic interaction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.826, year: 2012 http://www.sciencedirect.com/science/article/pii/S0304885311008997
Spin wave isolator based on frequency displacement nonreciprocity in ferromagnetic bilayer
Energy Technology Data Exchange (ETDEWEB)
Shichi, Shinsuke, E-mail: shinsuke-shichi@murata.com; Matsuda, Kenji; Okajima, Shingo; Hasegawa, Takashi; Okada, Takekazu [Murata Manufacturing Co., Ltd., Kyoto 617-8555 (Japan); Kanazawa, Naoki; Goto, Taichi, E-mail: goto@ee.tut.ac.jp; Takagi, Hiroyuki; Inoue, Mitsuteru [Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibari-Ga-Oka, Tempaku, Toyohashi, Aichi 441-8580 (Japan)
2015-05-07
We demonstrated the spin wave isolator using bilayer ferromagnetic media comprising single crystalline and poly-crystalline yttrium iron garnet films, which can control the propagation frequency of magnetostatic waves by the direction of applied magnetic field. This isolator's property does not depend on their thickness then this can be downsized and integrated for nano-scale magnonic circuits. Calculated dispersion relationship shows good agreement with measured one.
The metre-kilogram-second system of electrical units
Sas, R K
1947-01-01
Introduction ; electrostatic units, electromagnetic units, and practical units ; magnetic intensity and flux density ; rationalization ; tribulations of the student ; metres and kilograms in general and in mechanics ; pulse and aperture ; magnetostatics ; steady currents ; electrostatics ; resistance ; electromagnetic induction ; determination of Eo. capacity formulae ; field ; electrons and moving charges ; quantum theory ; memory assisted by the M.K.S. system ; short account of M.K.S. units ; list of formulae
Energy Technology Data Exchange (ETDEWEB)
Kryshtal, R.G.; Medved, A.V., E-mail: avm@ms.ire.rssi.ru
2017-03-15
Experimental results on the investigation of the influence of magnetic crystallographic anisotropy onto parameters of dynamic magnonic crystals arising at surface acoustic wave (SAW) propagation in yttrium iron garnet (YIG) films are presented. The main features of such an influence, as we have shown, are: 1) appearance of extra magnonic band gaps together with the normal magnonic band gap existing without anisotropy, 2) the absence of reflections of the incident surface magnetostatic wave at the frequency of these extra gaps, 3) the same depth for the extra gaps was achieved with a relatively small SAW power, almost by the order of magnitude less than in the case of normal magnonic gaps caused by SAW. A possible explanation of the features is given on the base of inelastic scattering of surface magnetostatic waves by SAW with the transformation of the reflected surface wave to the anisotropic direct volume magnetostatic wave existence of which is due to cubic crystallographic anisotropy in YIG. These results may be useful in designing new devices of information processing. - Highlights: • A new mechanism of creation of dynamic magnonic crystals by SAW propagating in real YIG films with magnetic anisotropy is investigated. • This mechanism is based on inelastic scattering of SMSW by SAW with SMSW transformation to the anisotropic volume magnetostatic wave. • This mechanism brings to creating by SAW additional (extra) magnonic stop bands for SMSW. • The given depth of these band gaps is achieved at SAW powers of the order of magnitude less than in the case of normal magnonic gaps created by SAW in the magnonic crystal without taking into account the anisotropy. • No reflected waves, usually taking place at SMSW propagation at the frequency of normal magnonic gaps, were detected. Such extra gaps look like a magnonic 'black hole' for SMSW. • These new properties of SAW-magnonic crystals, given by the magnetic anisotropy, may be used at creating
Kalvas, T.
2013-12-16
This chapter gives an introduction to low-energy beam transport systems, and discusses the typically used magnetostatic elements (solenoid, dipoles and quadrupoles) and electrostatic elements (einzel lens, dipoles and quadrupoles). The ion beam emittance, beam space-charge effects and the physics of ion source extraction are introduced. Typical computer codes for analysing and designing ion optical systems are mentioned, and the trajectory tracking method most often used for extraction simulations is described in more detail.
Didactical formulation of the Ampère law
International Nuclear Information System (INIS)
Barchiesi, Dominique
2014-01-01
The Ampère law is useful to calculate the magnetostatic field in the cases of distributions of current with high degree of symmetry. Nevertheless the magnetic field produced by a thin straight wire carrying a current I requires the Biot–Savart law and the use of the Ampère law leads to a mistake. A didactical formulation of the Ampère law is proposed to prevent misinterpretations. (letters and comments)
Edge rotational magnons in magnonic crystals
International Nuclear Information System (INIS)
Lisenkov, Ivan; Kalyabin, Dmitry; Nikitov, Sergey
2013-01-01
It is predicted that in 2D magnonic crystals the edge rotational magnons of forward volume magnetostatic spin waves can exist. Under certain conditions, locally bounded magnons may appear within the crystal consisting of the ferromagnetic matrix and periodically inserted magnetic/non-magnetic inclusions. It is also shown that interplay of different resonances in 2D magnonic crystal may provide conditions for spin wave modes existence with negative group velocity
International Nuclear Information System (INIS)
Kryshtal, R.G.; Medved, A.V.
2017-01-01
Experimental results on the investigation of the influence of magnetic crystallographic anisotropy onto parameters of dynamic magnonic crystals arising at surface acoustic wave (SAW) propagation in yttrium iron garnet (YIG) films are presented. The main features of such an influence, as we have shown, are: 1) appearance of extra magnonic band gaps together with the normal magnonic band gap existing without anisotropy, 2) the absence of reflections of the incident surface magnetostatic wave at the frequency of these extra gaps, 3) the same depth for the extra gaps was achieved with a relatively small SAW power, almost by the order of magnitude less than in the case of normal magnonic gaps caused by SAW. A possible explanation of the features is given on the base of inelastic scattering of surface magnetostatic waves by SAW with the transformation of the reflected surface wave to the anisotropic direct volume magnetostatic wave existence of which is due to cubic crystallographic anisotropy in YIG. These results may be useful in designing new devices of information processing. - Highlights: • A new mechanism of creation of dynamic magnonic crystals by SAW propagating in real YIG films with magnetic anisotropy is investigated. • This mechanism is based on inelastic scattering of SMSW by SAW with SMSW transformation to the anisotropic volume magnetostatic wave. • This mechanism brings to creating by SAW additional (extra) magnonic stop bands for SMSW. • The given depth of these band gaps is achieved at SAW powers of the order of magnitude less than in the case of normal magnonic gaps created by SAW in the magnonic crystal without taking into account the anisotropy. • No reflected waves, usually taking place at SMSW propagation at the frequency of normal magnonic gaps, were detected. Such extra gaps look like a magnonic 'black hole' for SMSW. • These new properties of SAW-magnonic crystals, given by the magnetic anisotropy, may be used at creating
Design Methodology of a Brushless IPM Machine for a Zero Speed Injection Based Sensorless Control
Godbehere, Jonathan; Wrobel, Rafal; Drury, David; Mellor, Phil
2015-01-01
In this paper a design approach for a sensorless controlled, brushless, interior permanent magnet machine is attained. An initial study based on established electrical machine formulas provides the machine’s basic geometrical sizing. The next design stage combines a particle swarm optimisation (PSO) search routine with a magneto-static finite element (FE) solver to provide a more in depth optimisation. The optimisation system has been formulated to derive alternative machine design variants, ...
Magnetotail equilibrium theory - The general three-dimensional solution
Birn, J.
1987-01-01
The general magnetostatic equilibrium problem for the geomagnetic tail is reduced to the solution of ordinary differential equations and ordinary integrals. The theory allows the integration of the self-consistent magnetotail equilibrium field from the knowledge of four functions of two space variables: the neutral sheet location, the total pressure, the magnetic field strength, and the z component of the magnetic field at the neutral sheet.
MFM observation of spin structures in nano-magnetic-dot arrays fabricated by damascene technique
International Nuclear Information System (INIS)
Sato, K.; Yamamoto, T.; Tezuka, T.; Ishibashi, T.; Morishita, Y.; Koukitu, A.; Machida, K.; Yamaoka, T.
2006-01-01
Regularly aligned arrays of magnetic nano dots buried in silicon wafers have been fabricated using damascene technique with the help of electron beam lithography. Arrays of square, rectangular, cross-shaped and Y-shaped structures of submicron size have been obtained. Spin distributions have been observed by means of magnetic force microscopy and analyzed by a micromagnetic simulation with Landau-Lifshitz-Gilbert equations. Importance of magnetostatic interactions working between adjacent dots has been elucidated
Theory of a relativistic peniotron
International Nuclear Information System (INIS)
Zhurakhovskii, V.A.
1986-01-01
A normalized mathematical model for describing the motion of electrons in a relativistic peniotron with smoothly varying magnetostatic field, which provides a state of exact gyroresonance along the entire length of the device, is constructed. The results of computer calculations of the energetics of this device are presented and an example of an effective choice of its parameterse corresponding to high electronic efficiency of a one-velocity flow are presented
A remotely interrogatable sensor for chemical monitoring
Stoyanov, P. G.; Doherty, S. A.; Grimes, C. A.; Seitz, W. R.
1998-01-01
A new type of continuously operating, in-situ, remotely monitored sensor is presented. The sensor is comprised of a thin film array of magnetostatically coupled, magnetically soft ferromagnetic thin film structures, adhered to or encased within a thin polymer layer. The polymer is made so that it swells or shrinks in response to the chemical analyte of interest, which in this case is pH. As the polymer swells or shrinks, the magnetostatic coupling between the magnetic elements changes, resulting in changes in the magnetic switching characteristics of the sensor. Placed within a sinusoidal magnetic field the magnetization vector of the coupled sensor elements periodically reverses directions, generating magnetic flux that can be remotely detected as a series of voltage spikes in appropriately placed pickup coils. one preliminary sensor design consists of four triangles, initially spaced approximately 50 micrometers apart, arranged to form a 12 mm x 12 mm square with the triangle tips centered at a common origin. Our preliminary work has focused on monitoring of pH using a lightly crosslinked pH sensitive polymer layer of hydroxyethylmethacrylate and 2-(dimethylamino) ethylmethacrylate. As the polymer swells or shrinks the magnetostatic coupling between the triangles changes, resulting in measurable changes in the amplitude of the detected voltage spirits.
A ferrite LTCC based dual purpose helical antenna providing bias for tunability
Ghaffar, Farhan A.
2015-03-30
Typically, magnetically tunable antennas utilize large external magnets or coils to provide the magneto-static bias. In this work, we present a novel concept of combining the antenna and the bias coil in one structure. A helical antenna has been optimized to act as the bias coil in a ten layer ferrite LTCC package, thus performing two functions. This not only reduces the overall size of the system by getting rid of the external bias source but also eliminates demagnetization effect (fields lost at air-to-substrate interface), which reduces the required magneto-static field strength and makes the design efficient. RF choking inductor and DC blocking capacitor have been monolithically integrated as package elements to allow the magnetostatic and microwave excitation at the same time. The design has been optimized for its low frequency and high frequency performance in two different simulators. A measured tuning range of 10% is achieved at a center frequency of 13 GHz. The design is highly suitable for low cost, compact, light-weight and tunable microwave systems. © 2002-2011 IEEE.
A ferrite LTCC based dual purpose helical antenna providing bias for tunability
Ghaffar, Farhan A.; Shamim, Atif
2015-01-01
Typically, magnetically tunable antennas utilize large external magnets or coils to provide the magneto-static bias. In this work, we present a novel concept of combining the antenna and the bias coil in one structure. A helical antenna has been optimized to act as the bias coil in a ten layer ferrite LTCC package, thus performing two functions. This not only reduces the overall size of the system by getting rid of the external bias source but also eliminates demagnetization effect (fields lost at air-to-substrate interface), which reduces the required magneto-static field strength and makes the design efficient. RF choking inductor and DC blocking capacitor have been monolithically integrated as package elements to allow the magnetostatic and microwave excitation at the same time. The design has been optimized for its low frequency and high frequency performance in two different simulators. A measured tuning range of 10% is achieved at a center frequency of 13 GHz. The design is highly suitable for low cost, compact, light-weight and tunable microwave systems. © 2002-2011 IEEE.
Field calculations. Part I: Choice of variables and methods
International Nuclear Information System (INIS)
Turner, L.R.
1981-01-01
Magnetostatic calculations can involve (in order of increasing complexity) conductors only, material with constant or infinite permeability, or material with variable permeability. We consider here only the most general case, calculations involving ferritic material with variable permeability. Variables suitable for magnetostatic calculations are the magnetic field, the magnetic vector potential, and the magnetic scalar potential. For two-dimensional calculations the potentials, which each have only one component, have advantages over the field, which has two components. Because it is a single-valued variable, the vector potential is perhaps the best variable for two-dimensional calculations. In three dimensions, both the field and the vector potential have three components; the scalar potential, with only one component,provides a much smaller system of equations to be solved. However the scalar potential is not single-valued. To circumvent this problem, a calculation with two scalar potentials can be performed. The scalar potential whose source is the conductors can be calculated directly by the Biot-Savart law, and the scalar potential whose source is the magnetized material is single valued. However in some situations, the fields from the two potentials nearly cancel; and the numerical accuracy is lost. The 3-D magnetostatic program TOSCA employs a single total scalar potential; the program GFUN uses the magnetic field as its variable
Topology optimized permanent magnet systems
Bjørk, R.; Bahl, C. R. H.; Insinga, A. R.
2017-09-01
Topology optimization of permanent magnet systems consisting of permanent magnets, high permeability iron and air is presented. An implementation of topology optimization for magnetostatics is discussed and three examples are considered. The Halbach cylinder is topology optimized with iron and an increase of 15% in magnetic efficiency is shown. A topology optimized structure to concentrate a homogeneous field is shown to increase the magnitude of the field by 111%. Finally, a permanent magnet with alternating high and low field regions is topology optimized and a Λcool figure of merit of 0.472 is reached, which is an increase of 100% compared to a previous optimized design.
Combined Simulation of a Micro Permanent Magnetic Linear Contactless Displacement Sensor
Directory of Open Access Journals (Sweden)
Jing Gao
2010-09-01
Full Text Available The permanent magnetic linear contactless displacement (PLCD sensor is a new type of displacement sensor operating on the magnetic inductive principle. It has many excellent properties and has already been used for many applications. In this article a Micro-PLCD sensor which can be used for microelectromechanical system (MEMS measurements is designed and simulated with the CST EM STUDIO® software, including building a virtual model, magnetostatic calculations, low frequency calculations, steady current calculations and thermal calculations. The influence of some important parameters such as air gap dimension, working frequency, coil current and eddy currents etc. is studied in depth.
International Nuclear Information System (INIS)
Tandon, S.; Beleggia, M.; Zhu, Y.; De Graef, M.
2004-01-01
A Fourier space formalism based on the shape amplitude of a particle is used to compute the demagnetization tensor field for uniformly magnetized particles of arbitrary shape. We provide a list of explicit shape amplitudes for important particle shapes, among others: the sphere, the cylindrical tube, an arbitrary polyhedral shape, a truncated paraboloid, and a cone truncated by a spherical cap. In Part I of this two-part paper, an analytical representation of the demagnetization tensor field for particles with cylindrical symmetry is provided, as well as expressions for the magnetostatic energy and the volumetric demagnetization factors
Topology optimized permanent magnet systems
DEFF Research Database (Denmark)
Bjørk, Rasmus; Bahl, Christian; Insinga, Andrea Roberto
2017-01-01
Topology optimization of permanent magnet systems consisting of permanent magnets, high permeability iron and air is presented. An implementation of topology optimization for magnetostatics is discussed and three examples are considered. The Halbach cylinder is topology optimized with iron...... and an increase of 15% in magnetic efficiency is shown. A topology optimized structure to concentrate a homogeneous field is shown to increase the magnitude of the field by 111%. Finally, a permanent magnet with alternating high and low field regions is topology optimized and a ΛcoolΛcool figure of merit of 0...
Mitsubishi Denki Giho, Vol. 67, No. 5, 1993
Energy Technology Data Exchange (ETDEWEB)
1993-01-01
Partial Contents: Magnetic Films for Magnetostatic Wave Devices; New Printed Circuit Board Products and Recent Technical Trends; Copper Alloys for Electronic Parts; A Ferrite Device for High Resolution Display and EMC Applications; Improvement in the Superconducting Properties of Metal Oxide Superconducting Wires; Pi-Conjugated Polymers for Optical and Electronic Devices; High-Dielectric-Constant Materials for Next-Generation DRAM Capacitors; Photoresist Materials for Excimer-Laser Lithography; Open Network Support for Small Business Computers; A Tutoring System Incorporating the Use of a Facsimile Machine; A Thyristor Starting Device for Thermal Power Stations.
Modeling Vertical Plasma Flows in Solar Filament Barbs
Litvinenko, Y.
2003-12-01
Speeds of observed flows in quiescent solar filaments are typically much less than the local Alfvén speed. This is why the flows in filament barbs can be modeled by perturbing a local magnetostatic solution describing the balance between the Lorentz force, gravity, and gas pressure in a barb. Similarly, large-scale filament flows can be treated as adiabatically slow deformations of a force-free magnetic equilibrium that describes the global structure of a filament. This approach reconciles current theoretical models with the puzzling observational result that some of the flows appear to be neither aligned with the magnetic field nor controlled by gravity.
The free energies of partially open coronal magnetic fields
Low, B. C.; Smith, D. F.
1993-01-01
A simple model of the low corona is examined in terms of a static polytropic atmosphere in equilibrium with a global magnetic field. The question posed is whether magnetostatic states with partially open magnetic fields may contain magnetic energies in excess of those in fully open magnetic fields. Based on the analysis presented here, it is concluded that the cross-field electric currents in the pre-eruption corona are a viable source of the bulk of the energies in a mass ejection and its associated flare.
Das, Ashok
2013-01-01
These lecture notes on electromagnetism have evolved from graduate and undergraduate EM theory courses given by the author at the University of Rochester, with the basics presented with clarity and his characteristic attention to detail. The thirteen chapters cover, in logical sequence, topics ranging from electrostatics, magnetostatics and Maxwell's equations to plasmas and radiation. Boundary value problems are treated extensively, as are wave guides, electromagnetic interactions and fields. This second edition comprises many of the topics expanded with more details on the derivation of vari
Globally Optimal Segmentation of Permanent-Magnet Systems
DEFF Research Database (Denmark)
Insinga, Andrea Roberto; Bjørk, Rasmus; Smith, Anders
2016-01-01
Permanent-magnet systems are widely used for generation of magnetic fields with specific properties. The reciprocity theorem, an energy-equivalence principle in magnetostatics, can be employed to calculate the optimal remanent flux density of the permanent-magnet system, given any objective...... remains unsolved. We show that the problem of optimal segmentation of a two-dimensional permanent-magnet assembly with respect to a linear objective functional can be reduced to the problem of piecewise linear approximation of a plane curve by perimeter maximization. Once the problem has been cast...
Spin wave absorber generated by artificial surface anisotropy for spin wave device network
Directory of Open Access Journals (Sweden)
Naoki Kanazawa
2016-09-01
Full Text Available Spin waves (SWs have the potential to reduce the electric energy loss in signal processing networks. The SWs called magnetostatic forward volume waves (MSFVWs are advantageous for networking due to their isotropic dispersion in the plane of a device. To control the MSFVW flow in a processing network based on yttrium iron garnet, we developed a SW absorber using artificial structures. The mechanical surface polishing method presented in this work can well control extrinsic damping without changing the SW dispersion of the host material. Furthermore, enhancement of the ferromagnetic resonance linewidth over 3 Oe was demonstrated.
Hewagama, Tilak; Deming, Drake; Jennings, Donald E.; Osherovich, Vladimir; Wiedemann, Gunter; Zipoy, David; Mickey, Donald L.; Garcia, Howard
1993-01-01
Polarimetric observations at 12 microns of two sunpots are reported. The horizontal distribution of parameters such as magnetic field strength, inclination, azimuth, and magnetic field filling factors are presented along with information about the height dependence of the magnetic field strength. Comparisons with contemporary magnetostatic sunspot models are made. The magnetic data are used to estimate the height of 12 micron line formation. From the data, it is concluded that within a stable sunspot there are no regions that are magnetically filamentary, in the sense of containing both strong-field and field-free regions.
Electromagnetic field properties in the vicinity of a massive wormhole
Energy Technology Data Exchange (ETDEWEB)
Novikov, I. D.; Shatskiy, A. A., E-mail: shatskiy@asc.rssi.ru [Russian Academy of Sciences, Astro Space Centre, Lebedev Physical Institute (Russian Federation)
2011-12-15
It is proved that not only massless but also traversable massive wormholes can have electromagnetic 'hair.' An analysis is also presented of the passage from a traversable wormhole to the limit of a Reissner-Nordstroem black hole, with the corresponding disappearance of 'hair.' A general method is developed for solving stationary axisymmetric Maxwell's equations in the field of a massive, spherically symmetric wormhole. As a particular example of application of the method, a solution is found to the axisymmetric magnetostatic problem for a current loop in the field of the Bronnikov-Ellis-Morris-Thorne wormhole.
Magnetic interactions and the method of images: a wealth of educational suggestions
International Nuclear Information System (INIS)
Bonanno, A; Camarca, M; Sapia, P
2011-01-01
Under some conditions, the method of images (well known in electrostatics) may be implemented in magnetostatic problems too, giving an excellent example of the usefulness of formal analogies in the description of physical systems. In this paper, we develop a quantitative model for the magnetic interactions underlying the so-called Geomag(TM) paradox and describe a quantitative experimental investigation to validate the model. The validity ranges of some approximations involved in this problem are quantitatively discussed and the advantages of a dimensionless formulation of the interaction are pointed out. This work offers many educational suggestions suitable for university students.
Design concepts for a continuously rotating active magnetic regenerator
DEFF Research Database (Denmark)
Bahl, Christian Robert Haffenden; Engelbrecht, Kurt; Bjørk, Rasmus
2011-01-01
Design considerations for a prototype magnetic refrigeration device with a continuously rotating AMR are presented. Building the active magnetic regenerator (AMR) from stacks of elongated plates of the perovskite oxide material La0.67Ca0.33−xSrxMn1.05O3, gives both a low pressure drop and allows....... Focus is on maximising the magnetic field in the high field regions but also, importantly, minimising the flux in the low field regions. The design is iteratively optimised through 3D finite element magnetostatic modelling....
Kocharovsky, V. V.; Kocharovsky, Vl V.; Martyanov, V. Yu; Nechaev, A. A.
2017-12-01
We derive and describe analytically a new wide class of self-consistent magnetostatic structures with sheared field lines and arbitrary energy distributions of particles. To do so we analyze superpositions of two planar current sheets with orthogonal magnetic fields and cylindrically symmetric momentum distribution functions, such that the magnetic field of one of them is directed along the symmetry axis of the distribution function of the other. These superpositions satisfy the pressure balance equation and allow one to construct configurations with an almost arbitrarily sheared magnetic field. We show that most of previously known current sheet families with sheared magnetic field lines are included in this novel class.
Study of a Quantum Dot in an Excited State
Slamet, Marlina; Sahni, Viraht
We have studied the first excited singlet state of a quantum dot via quantal density functional theory (QDFT). The quantum dot is represented by a 2D Hooke's atom in an external magnetostatic field. The QDFT mapping is from an excited singlet state of this interacting system to one of noninteracting fermions in a singlet ground state. The results of the study will be compared to (a) the corresponding mapping from a ground state of the quantum dot and (b) to the similar mapping from an excited singlet state of the 3D Hooke's atom.
Complex analysis with applications to flows and fields
Braga da Costa Campos, Luis Manuel
2012-01-01
Complex Analysis with Applications to Flows and Fields presents the theory of functions of a complex variable, from the complex plane to the calculus of residues to power series to conformal mapping. The book explores numerous physical and engineering applications concerning potential flows, the gravity field, electro- and magnetostatics, steady heat conduction, and other problems. It provides the mathematical results to sufficiently justify the solution of these problems, eliminating the need to consult external references.The book is conveniently divided into four parts. In each part, the ma
Method to stimulate dose gradient in liquid media
International Nuclear Information System (INIS)
Scarlat, F.
1993-01-01
The depth absorbed dose from electrons with energy higher than 10 MeV shows a distribution with a big-percentage absorbed dose at the entrance surface and a small dose gradient. This is due to the big distance between the virtual focus and irradiated liquid medium. In order to stimulate dose gradient and decrease the surface dose, this paper presents a method for obtaining the second focus by means of a magnetostatic planar wiggler. Preliminary calculations indicated that the absorbed dose rate increases two-three times at the reference plane in the irradiated liquid medium. (Author)
Wave scattering theory a series approach based on the Fourier transformation
Eom, Hyo J
2001-01-01
The book provides a unified technique of Fourier transform to solve the wave scattering, diffraction, penetration, and radiation problems where the technique of separation of variables is applicable. The book discusses wave scattering from waveguide discontinuities, various apertures, and coupling structures, often encountered in electromagnetic, electrostatic, magnetostatic, and acoustic problems. A system of simultaneous equations for the modal coefficients is formulated and the rapidly-convergent series solutions amenable to numerical computation are presented. The series solutions find practical applications in the design of microwave/acoustic transmission lines, waveguide filters, antennas, and electromagnetic interference/compatibilty-related problems.
Micromagnetic simulations of submicron cobalt dots
International Nuclear Information System (INIS)
Parker, G. J.; Cerjan, C.
2000-01-01
Numerical simulations of submicron Co extruded elliptical dots were performed to illustrate the relative importance of different physical parameters on the switching behavior in the easy direction. Shape, size, magnetic moment magnitude, and the magnitude and distribution of the crystalline anisotropicity were varied. The simulation represents magnetostatic, exchange, and crystalline anisotropicity fields on a structured mesh using finite difference techniques. The smooth boundary of the dots is accurately represented by use of the embedded curve boundary method. Agreement with experimental hysteresis measurements of submicron dot arrays is obtained when an appropriate angular distribution of the grain anisotropicity axes is invoked. (c) 2000 American Institute of Physics
Modeling of Magnetoelectric Interaction in Magnetostrictive-Piezoelectric Composites
Directory of Open Access Journals (Sweden)
M. I. Bichurin
2012-01-01
Full Text Available The paper dwells on the theoretical modeling of magnetoelectric (ME effect in layered and bulk composites based on magnetostrictive and piezoelectric materials. Our analysis rests on the simultaneous solution of elastodynamic or elastostatic and electro/magnetostatic equations. The expressions for ME coefficients as the functions of material parameters and volume fractions of components are obtained. Longitudinal, transverse, and in-plane cases are considered. The use of the offered model has allowed to present the ME effect in ferrite cobalt-barium titanate, ferrite cobalt-PZT, ferrite nickel-PZT, and lanthanum strontium manganite-PZT composites adequately.
Simulating a singularity-free universe outside the problem boundary in poisson
International Nuclear Information System (INIS)
Halbach, K.; Schlueter, R.
1992-01-01
An exact analytical solution developed from the Dirichlet problem exterior to a circle is employed in the magnetostatics code POISSON to provide a boundary condition option which simulates a singularity-free universe external to the problem domain. Problems with domains of large unequal extents in perpendicular directions are treated by first conformally mapping the exterior of an ellipse onto the exterior of the unit circle. Problems exhibiting symmetry in one or two planes are modeled using a semi or quarter, respectively, in conjunction with the singularity-free rest-of-universe boundary condition
Forces between arrays of permanent magnets of basic geometric shapes
Czech Academy of Sciences Publication Activity Database
Vokoun, David; Beleggia, M.
2014-01-01
Roč. 350, JAN (2014), s. 174-178 ISSN 0304-8853 R&D Projects: GA ČR(CZ) GAP107/11/0391; GA MŠk(CZ) LM2011026 Institutional support: RVO:68378271 Keywords : permanent magnet * cylindrical magnet * attraction force * magnetostatic interaction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.970, year: 2014 http://ac.els-cdn.com/S0304885313006732/1-s2.0-S0304885313006732-main.pdf?_tid=f6840b24-5115-11e3-9237-00000aab0f6b&acdnat=1384864232_323ac87712560a07
Energy Technology Data Exchange (ETDEWEB)
Wenisch, Jan
2008-07-01
This work studies the fundamental connection between lattice strain and magnetic anisotropy in the ferromagnetic semiconductor (Ga,Mn)As. The first chapters provide a general introduction into the material system and a detailed description of the growth process by molecular beam epitaxy. A finite element simulation formalism is developed to model the strain distribution in (Ga,Mn)As nanostructures is introduced and its predictions verified by high-resolution X-ray diffraction methods. The influence of lattice strain on the magnetic anisotropy is explained by an magnetostatic model. A possible device application is described in the closing chapter. (orig.)
Darwin model in plasma physics revisited
International Nuclear Information System (INIS)
Xie, Huasheng; Zhu, Jia; Ma, Zhiwei
2014-01-01
Dispersion relations from the Darwin (a.k.a., magnetoinductive or magnetostatic) model are given and compared with those of the full electromagnetic model. Analytical and numerical solutions show that the errors from the Darwin approximation can be large even if phase velocity for a low-frequency wave is close to or larger than the speed of light. Besides missing two wave branches associated mainly with the electron dynamics, the coupling branch of the electrons and ions in the Darwin model is modified to become a new artificial branch that incorrectly represents the coupling dynamics of the electrons and ions. (paper)
Chang, L H; Luo, G H; Lin, M C
2002-01-01
This paper presents a novel empirical formula for evaluating the axial magnetic attenuation of a circularly cylindrical shield with partial openings at both ends, which is derived under the assumption of scaling law with help of the 3-D magnetostatic code TOSCA for computing the magnetic attenuation of some canonical models. Our formula allows a quick evaluation of the magnetic shielding for design application to a superconducting radio-frequency cavity with less than 10% discrepancy in comparison with that obtained from pure numerical simulations.
Theoretical prediction of a rotating magnon wave packet in ferromagnets.
Matsumoto, Ryo; Murakami, Shuichi
2011-05-13
We theoretically show that the magnon wave packet has a rotational motion in two ways: a self-rotation and a motion along the boundary of the sample (edge current). They are similar to the cyclotron motion of electrons, but unlike electrons the magnons have no charge and the rotation is not due to the Lorentz force. These rotational motions are caused by the Berry phase in momentum space from the magnon band structure. Furthermore, the rotational motion of the magnon gives an additional correction term to the magnon Hall effect. We also discuss the Berry curvature effect in the classical limit of long-wavelength magnetostatic spin waves having macroscopic coherence length.
Nonreciprocity of edge modes in 1D magnonic crystal
International Nuclear Information System (INIS)
Lisenkov, I.; Kalyabin, D.; Osokin, S.; Klos, J.W.; Krawczyk, M.; Nikitov, S.
2015-01-01
Spin waves propagation in 1D magnonic crystals is investigated theoretically. Mathematical model based on plane wave expansion method is applied to different types of magnonic crystals, namely bi-component magnonic crystal with symmetric/asymmetric boundaries and ferromagnetic film with periodically corrugated top surface. It is shown that edge modes in magnonic crystals may exhibit nonreciprocal behaviour at much lower frequencies than in homogeneous films. - Highlights: • Magnetostatic surface spin waves in 1D magnonic crystals were studied theoretically. • Mathematical model is based on plane wave method. • Mathematical model was applied to different types of magnonic crystals. • Stop band formation and nonreciprocity were obtained
Diffraction imaging study of the phase coexistence around the triple point in MnP
International Nuclear Information System (INIS)
Medrano, C.; Pernot, E.; Espeso, J.I.; Boller, E.; Lorut, F.; Baruchel, J.
2001-01-01
The coexistence of the helimagnetic, ferromagnetic and fan phases in the neighborhood of the triple point is investigated by real-time Bragg diffraction imaging in a (0 0 1) MnP crystal. When increasing the field while retaining the heli-ferromagnetic coexistence, the nucleation of the fan phase occurs inside the present interface. The shapes and orientations of the heli-ferromagnetic and fan-helimagnetic interfaces can be understood by considering the corresponding elastic and/or magnetostatic energy. The ferromagnetic-fan thick interface, on the contrary, suggests the existence of intermediate states
Tu, Kun-Hua
2018-04-10
Dense arrays of pillars, with diameters of 64 and 25 nm, were made from a perpendicular CoFeB magnetic tunnel junction thin film stack using block copolymer lithography. While the soft layer and hard layer in the 64 nm pillars reverse at different fields, the reversal of the two layers in the 25 nm pillars could not be distinguished, attributed to the strong interlayer magnetostatic coupling. First order reversal curves were used to identify the steps that occur during switching, and the thermal stability and effective switching volume were determined from scan rate dependent hysteresis measurements.
Modified small angle magnetization rotation method in multilayer magnetic microwires
International Nuclear Information System (INIS)
Torrejon, J.; Badini, G.; Pirota, K.; Vazquez, M.
2007-01-01
The small angle magnetization rotation (SAMR) technique is a widely used method to quantify magnetostriction in elongated ultrasoft magnetic materials. In the present work, we introduce significant optimization of the method, particularly simplification of the required equipment, profiting of the very peculiar characteristics of a recently introduced family of multilayer magnetic microwires consisting of a soft magnetic core, insulating intermediate layer and a hard magnetic outer layer. The introduced modified SAMR method is used not only to determine the saturation magnetostriction constant of the soft magnetic nucleus but also the magnetoelastic and magnetostatic coupling. This new method has a great potential in multifunctional sensor applications
Light propagation in a magneto-optical hyperbolic biaxial crystal
Kuznetsov, Evgeniy V.; Merzlikin, Alexander M.
2017-12-01
The light propagation through a magneto-optical hyperbolic biaxial crystal is investigated. Magnetization of the structure results in splitting and reconnection of an isofrequency near the self-intersection point and thus it leads to the disappearance of conical refraction in a crystal. In its turn the isofrequency splitting leads to band gap opening and makes it possible to steer the beam. These effects allow to control the light propagation by means of an external magnetostatic field. The Poynting's vector distribution in the crystal is calculated by means of a Fourier transform in order to demonstrate the aforementioned effects.
Spin wave scattering and interference in ferromagnetic cross
Energy Technology Data Exchange (ETDEWEB)
Nanayakkara, Kasuni; Kozhanov, Alexander [Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia 30303 (United States); Center for Nano Optics, Georgia State University, Atlanta, Georgia 30303 (United States); Jacob, Ajey P. [Exploratory Research Device and Integration, GLOBALFOUNDRIES, Albany, New York 12203 (United States)
2015-10-28
Magnetostatic spin wave scattering and interference across a CoTaZr ferromagnetic spin wave waveguide cross junction were investigated experimentally and by micromagnetic simulations. It is observed that the phase of the scattered waves is dependent on the wavelength, geometry of the junction, and scattering direction. It is found that destructive and constructive interference of the spin waves generates switching characteristics modulated by the input phase of the spin waves. Micromagnetic simulations are used to analyze experimental data and simulate the spin wave scattering and interference.
The phase accumulation and antenna near field of microscopic propagating spin wave devices
Energy Technology Data Exchange (ETDEWEB)
Chang, Crosby S.; Kostylev, Mikhail, E-mail: mikhail.kostylev@uwa.edu.au; Ivanov, Eugene [School of Physics M013, The University of Western Australia, Crawley, WA 6009 (Australia); Ding, Junjia; Adeyeye, Adekunle O. [Department of Electrical and Computer Engineering, National University of Singapore, 117576 Singapore (Singapore)
2014-01-20
We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy.
The phase accumulation and antenna near field of microscopic propagating spin wave devices
International Nuclear Information System (INIS)
Chang, Crosby S.; Kostylev, Mikhail; Ivanov, Eugene; Ding, Junjia; Adeyeye, Adekunle O.
2014-01-01
We studied phase accumulation by the highly non-reciprocal magnetostatic surface spin waves in thin Permalloy microstripes excited and received by microscopic coplanar antennae. We find that the experimentally measured characteristic length of the near field of the antenna is smaller than the total width of the coplanar. This is confirmed by our numerical simulations. Consequently, the distance over which the spin wave accumulates its phase while travelling between the input and output antennae coincides with the distance between the antennae symmetry axes with good accuracy
Spin-wave wavelength down-conversion at thickness steps
Stigloher, Johannes; Taniguchi, Takuya; Madami, Marco; Decker, Martin; Körner, Helmut S.; Moriyama, Takahiro; Gubbiotti, Gianluca; Ono, Teruo; Back, Christian H.
2018-05-01
We report a systematic experimental study on the refraction and reflection of magnetostatic spin-waves at a thickness step between two Permalloy films of different thickness. The transmitted spin-waves for the transition from a thick film to a thin film have a higher wave vector compared to the incoming waves. Consequently, such systems may find use as passive wavelength transformers in magnonic networks. We investigate the spin-wave transmission behavior by studying the influence of the external magnetic field, incident angle, and thickness ratio of the films using time-resolved scanning Kerr microscopy and micro-focused Brillouin light scattering.
International Nuclear Information System (INIS)
Beleggia, M.; Graef, M. de
2003-01-01
A method is presented to compute the demagnetization tensor field for uniformly magnetized particles of arbitrary shape. By means of a Fourier space approach it is possible to compute analytically the Fourier representation of the demagnetization tensor field for a given shape. Then, specifying the direction of the uniform magnetization, the demagnetizing field and the magnetostatic energy associated with the particle can be evaluated. In some particular cases, the real space representation is computable analytically. In general, a numerical inverse fast Fourier transform is required to perform the inversion. As an example, the demagnetization tensor field for the tetrahedron will be given
Directory of Open Access Journals (Sweden)
F. Valdés-Bango
2017-05-01
Full Text Available Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.
Valdés-Bango, F.; Vélez, M.; Alvarez-Prado, L. M.; Alameda, J. M.; Martín, J. I.
2017-05-01
Hexagonal antidot arrays have been patterned on weak perpendicular magnetic anisotropy NdCo films by e-beam lithography and lift off. Domain structure has been characterized by Magnetic Force Microscopy at remanence. On a local length scale, of the order of stripe pattern period, domain configuration is controlled by edge effects within the stripe pattern: stripe domains meet the hole boundary at either perpendicular or parallel orientation. On a longer length scale, in-plane magnetostatic effects dominate the system: clear superdomains are observed in the patterned film with average in-plane magnetization along the easy directions of the antidot array, correlated over several antidot array cells.
Response of multiferroic composites inferred from a fast-Fourier-transform-based numerical scheme
International Nuclear Information System (INIS)
Brenner, Renald; Bravo-Castillero, Julián
2010-01-01
The effective response and the local fields within periodic magneto-electric multiferroic composites are investigated by means of a numerical scheme based on fast Fourier transforms. This computational framework relies on the iterative resolution of coupled series expansions for the magnetic, electric and strain fields. By using an augmented Lagrangian formulation, a simple and robust procedure which makes use of the uncoupled Green operators for the elastic, electrostatics and magnetostatics problems is proposed. Its accuracy is assessed in the cases of laminated and fibrous two-phase composites for which analytical solutions exist
Essentials of Electromagnetics for Engineering
de Wolf, David A.
2000-11-01
Essentials of Electromagnetics for Engineering introduces the key physical and engineering principles of electromagnetics. Throughout the book, David de Wolf describes the intermediate steps in mathematical derivations that many other textbooks leave out. He covers in depth the concepts of fields and potentials and then progresses to magnetostatics, Maxwell's equations, electrodynamics and wave propagation, waveguides, transmission lines, and antennas. At each stage, de Wolf stresses the physical principles underlying the mathematical results. He also includes homework exercises, a separate chapter on numerical methods in electromagnetics, and a broad range of worked examples to illustrate important concepts. Solutions manual available.
Ferrofluid aggregation in chains under the influence of a magnetic field
International Nuclear Information System (INIS)
Ivanov, Alexey O.; Kantorovich, Sofia S.; Mendelev, Valentin S.; Pyanzina, Elena S.
2006-01-01
The paper is devoted to the basic problem of chain aggregate formation in magnetic fluids under the influence of an external magnetic field. Chain distribution in dynamic equilibrium is obtained on the basis of free energy minimization method under the condition when the interparticle dipole-dipole interaction between the nearest neighboring ferroparticles in each chain is taken into account. The modified mean field approach is used for considering the dipole-dipole interaction between all particles in a ferrofluid. The model describes well the molecular dynamics simulations of magnetostatic properties for monodisperse ferrofluids containing chain aggregates
Radiation, waves, fields. Causes and effects on environment and health
International Nuclear Information System (INIS)
Leitgeb, N.
1990-01-01
The book discusses static electricity, alternating electric fields, magnetostatic fields, alternating magnetic fields, electromagnetic radiation, optical and ionizing radiation and their hazards and health effects. Each chapter presents basic physical and biological concepts and describes the common radiation sources and their biological effects. Each chapter also contains hints for everyday behaviour as well as in-depth information an specific scientific approaches for assessing biological effects; the latter are addressed to all expert readers working in these fields. There is a special chapter on the problem of so-called 'terrestrial radiation'. (orig.) With 88 figs., 31 tabs [de
International Nuclear Information System (INIS)
Buksa, J.J.; McColl, D.B.
1989-01-01
The reference flight system design of the SP-100 power system uses thermoelectric-electromagnetic (TEM) pumps to circulate its coolants. To predict the performance and estimate the mass of these pumps, an integrated computer model has been developed. This computer code, dubbed STEPAC, models the coupled thermal, magnetic, hydraulic and electrical aspects of the pump. The code incorporates a magnetic fringe model and a current dependent magnetic field strength model, both in conjunction with the Poisson magnetostatic code. STEPAC was used to predict the performance of the RFS SP-100 TEM pump and the results of several scoping parametric studies are presented
Analysis of the magnetic properties in hard-magnetic nanofibers composite
Murillo-Ortíz, R.; Mirabal-García, M.; Martínez-Huerta, J. M.; Cabal Velarde, J. G.; Castaneda-Robles, I. E.; Lobo-Guerrero, A.
2018-03-01
The magnetic properties of the strontium hexaferrite nanoparticles were studied as they were embedded at different concentrations in poly(vinyl alcohol) (PVA) nanofibers. These nanoparticles were prepared using the Pechini method and a low frequency sonication process obtaining a 3.4 nm average diameter. The composite consisting of hard magnetic nanoparticles homogeneously dispersed in a polymeric matrix was fabricated using a homemade electrospinning with 25 kV DC power supply. The obtained nanofibers had an average diameter of 110 nm, and nanoparticles were arranged and distributed within the nanofibers under the influence of a strong electric field. The configuration of the magnetic nanoparticles in the PVA nanofibers was such that the interparticle exchange interaction became negligible, while the magnetostatic interaction turned out predominant. The results reveal a considerable improvement in the energy product (BHmax) and in the squareness ratio (Mr/Ms) for nanoparticle concentrations between 15 and 30% per gram of PVA. The nanoparticles arrangement occurred at densities below the percolation concentration enhanced the hard-magnetic properties of the nanofibers, which indicates that the organization of the particles along the fibers induces anisotropy from the magnetostatic interaction among the magnetic nanoparticles. Finally, we close the discussion analyzing the observed effect below the percolation threshold, where the induced anisotropy caused the reduction of the full-width at half-maximum of the switching field distribution curves.
Quantal density functional theory. 2. ed.
International Nuclear Information System (INIS)
Sahni, Viraht
2016-01-01
This book is on quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The time-independent QDFT constitutes a special case. The 2 nd edition describes the further development of the theory, and extends it to include the presence of an external magnetostatic field. The theory is based on the 'quantal Newtonian' second and first laws for the individual electron. These laws are in terms of 'classical' fields that pervade all space, and their quantal sources. The fields are separately representative of the electron correlations that must be accounted for in local potential theory. Recent developments show that irrespective of the type of external field the electrons are subject to, the only correlations beyond those due to the Pauli exclusion principle and Coulomb repulsion that need be considered are solely of the correlation-kinetic effects. Foundational to QDFT, the book describes Schroedinger theory from the new perspective of the single electron in terms of the 'quantal Newtonian' laws. Hohenberg-Kohn density functional theory (DFT), new understandings of the theory and its extension to the presence of an external uniform magnetostatic field are described. The physical interpretation via QDFT, in terms of electron correlations, of Kohn-Sham DFT, approximations to it and Slater theory are provided.
Finite-element 3D simulation tools for high-current relativistic electron beams
Humphries, Stanley; Ekdahl, Carl
2002-08-01
The DARHT second-axis injector is a challenge for computer simulations. Electrons are subject to strong beam-generated forces. The fields are fully three-dimensional and accurate calculations at surfaces are critical. We describe methods applied in OmniTrak, a 3D finite-element code suite that can address DARHT and the full range of charged-particle devices. The system handles mesh generation, electrostatics, magnetostatics and self-consistent particle orbits. The MetaMesh program generates meshes of conformal hexahedrons to fit any user geometry. The code has the unique ability to create structured conformal meshes with cubic logic. Organized meshes offer advantages in speed and memory utilization in the orbit and field solutions. OmniTrak is a versatile charged-particle code that handles 3D electric and magnetic field solutions on independent meshes. The program can update both 3D field solutions from the calculated beam space-charge and current-density. We shall describe numerical methods for orbit tracking on a hexahedron mesh. Topics include: 1) identification of elements along the particle trajectory, 2) fast searches and adaptive field calculations, 3) interpolation methods to terminate orbits on material surfaces, 4) automatic particle generation on multiple emission surfaces to model space-charge-limited emission and field emission, 5) flexible Child law algorithms, 6) implementation of the dual potential model for 3D magnetostatics, and 7) assignment of charge and current from model particle orbits for self-consistent fields.
Theoretical analysis of transcranial magneto-acoustical stimulation with Hodgkin–Huxley neuron model
Directory of Open Access Journals (Sweden)
Yi eYuan
2016-04-01
Full Text Available Transcranial magneto-acoustical stimulation (TMAS is a novel stimulation technology in which an ultrasonic wave within a magnetostatic field generates an electric current in an area of interest in the brain to modulate neuronal activities. As a key part of the neural network, neurons transmit information in the nervous system. However, the effect of TMAS on the neuronal firing rhythm remains unknown. To address this problem, we investigated the stimulatory mechanism of TMAS on neurons with a Hodgkin-Huxley neuron model. The simulation results indicate that the magnetostatic field intensity and ultrasonic power can affect the amplitude and interspike interval of neuronal action potential under continuous wave ultrasound. The simulation results also show that the ultrasonic power, duty cycle and repetition frequency can alter the firing rhythm of neural action potential under pulsed ultrasound. This study can help to reveal and explain the biological mechanism of TMAS and to provide a theoretical basis for TMAS in the treatment or rehabilitation of neuropsychiatric disorders.
Magnetic study of extraction elements of compact cyclotron beam with AGOR superconducting coils
International Nuclear Information System (INIS)
Gustafsson, S.
1991-12-01
The extraction system of the superconducting cyclotrons is normally making a large use of electric extractors followed by magnetostatic elements. The electric field limit initially hoped for (14 MV/m) has been shown to be too optimistic. A more realistic value is around 10 MV/m in the concerned geometries. The first element of the AGOR extraction system is an electrostatic channel where the maximum electric field is limited to 10.5 MV/m. The smaller separation between the internal beam and the extracted beam at the entrance of the first magnetic element is compensated by the replacement of the usual magnetostatic channels with high power electromagnetic channels placed in the reduced space close to the internal beam and where the horizontal position can be adjusted according to the kind of ion accelerated and its energy. The fringing field very close to the channels is controlled with the help of correction coils reducing the perturbations of the internal beam trajectories to an acceptable level
International Nuclear Information System (INIS)
Lembege, B.; Savoini, P.
1992-01-01
Two-dimensional electromagnetic particle simulations evidence a self-reformation of the shock front for a collisionless supercritical magnetosonic shock propagating at angle θ 0 around 90 degree, where θ 0 is the angle between the normal to the shock front and the upstream magnetostatic field. This self-reformation is due to reflected ions which accumulate in front of the shock and is observed (i) in both electric and magnetic components, (ii) for both resistive and nonresistive two-dimensional shocks, and (iii) over a cyclic time period equal to the mean ion gyroperiod measured downstream in the overshoot; resistive effects may be self-consistently included or excluded for θ 0 congruent 90 degree according to a judicious choice of the upstream magnetostatic field orientation. The self-reformation leads to a nonstationary behavior of the shock; however, present results show evidence that the shock becomes stationary for θ less than a critical value θ r , below which the self-reformation disappears. Present results are compared to previous works where one/two-dimensional hybrid and particle codes have been used, and to experimental measurements
Hysteresis loop design by geometry of garnet film element with single domain wall
International Nuclear Information System (INIS)
Skidanov, V A; Vetoshko, P M; Stempkovskiy, A L
2011-01-01
Numerical modeling and experimental investigation of magnetostatic stable states of two-domain structure in Bi-substituted uniaxial garnet film elements was made. Single domain walls (DW) between two opposite normally magnetized parts in isolated rectangular strip and strip-like bridge are found to exhibit different behavior. DW inside strip (bridge) suffers increasing repulsion (attraction) from nearest edge when shifted from element center. DW position center position is stable in isolated strip but bridge is magnetized spontaneously to one of two saturated states in zero external field. Isolated strip magnetization process occurs reversibly while bridge magnetization reversal occurs by coercive manner. Strip susceptibility and bridge coercive field are entirely defined by magnetostatic barrier created by element boundary stray field in case of constant DW length during magnetization reversal. Variation of strip and bridge boundary shape along DW trajectory gives the opportunity to create additional controllable potential profile due to DW surface energy modulation by DW length. Garnet elements with high Faraday rotation and low light switching field were developed for fine magnetic sensing and optical data processing applications.
Analytical model for shape anisotropy in thin-film nanostructured arrays: Interaction effects
International Nuclear Information System (INIS)
Alvarez-Sanchez, R.; Costa-Kraemer, J.L.; Briones, F.
2006-01-01
When reducing the size of array elements and interelement separations to the nanoscale, long-range magnetostatic interactions become important. A methodology that extends the study of conventional single-element magnetostatics is presented, adding the effect of stacking nanoelements into close proximity in arrays and the consequent interaction effects. This would be very time consuming to model by micromagnetic simulations that are also very vulnerable to artifacts due to cell or boundary condition selection. The proposed method considers an analytical expression valid for short interelement separations and not very costly to evaluate by computational means. This approach allows the quantitative study of shape anisotropy in non-square-shaped arrays. It is also shown how it can be used to find anisotropy compensation conditions, where an anisotropy due to a magnetic element shape can be compensated by the shape anisotropy due to the array. The obtained results can be used to establish a criterion for the minimum number of elements to be considered for a micromagnetic simulation of an array to be realistic depending on the element size and separation
Quantum oscillation and the Aharonov-Bohm effect in a multiply connected normal-conductor loop
Takai, Daisuke; Ohta, Kuniichi
1994-12-01
The magnetostatic and electrostatic Aharonov-Bohm (AB) effects in multiply connected normal-conductor rings are studied. A previously developed model of a single mesoscopic ring is generalized to include an arbitrary number of rings, and the oscillatory behavior of the total transmission coefficients for the serially connected N (N is equal to integer) rings are derived as a function of the magnetic flux threading each ring and as a function of the electrostatic potential applied to the rings. It is shown that quantum oscillation of multiple rings exhibits greater variety of behavior than in periodic superlattices. We investigate the influence of the scattering at a junction and the number of atoms in the ring in both magnetostatic and electrostatic oscillation of multiring systems. For the electrostatic AB effects, when scattering occurs at the junctions between the connecting wire and the ring, the conductance in the AB oscillation is modified to an N-1 peaked shape. It is shown that this oscillatory behavior is greatly influenced by the number of atoms in the ring and is controlled by the electrostatic potential or magnetic flux that is applied to the ring. We discuss the behavior of the quantum oscillations upon varying the number of connected rings and the number of minibands.
Energy Technology Data Exchange (ETDEWEB)
Yuan, H.Y. [Physics Department, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); HKUST Shenzhen Research Institute, Shenzhen 518057 (China); Wang, X.R., E-mail: phxwan@ust.hk [Physics Department, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon (Hong Kong); HKUST Shenzhen Research Institute, Shenzhen 518057 (China)
2014-11-15
Antivortex birth, growth and death accompanying the propagation of a transverse domain wall (DW) in magnetic nanostrips are observed and analyzed. Antivortex formation is an intrinsic process of a strawberry-like transverse DW originated from magnetostatic interaction. Under an external magnetic field, the wider width region of a DW tends to move faster than the narrower one. This speed mismatch tilts and elongates DW center line. As a result, an antivortex with a well-defined polarity is periodically born near the tail of the DW center line. The antivortex either moves along the center line and dies on the other side of the nanostrip, or grows to its maximum size, detaches itself from the DW, and vanishes eventually. The former route reverses the polarity of DW while the later keeps the DW polarity unchanged. The evolution of the DW structures is analyzed using winding numbers assigned to each topological defects. The phase diagram in the field-width plane is obtained and the damping constant's influence on the phase diagram is discussed. - Highlights: • The magnetostatic interaction leads to a strawberry-like domain wall. • Two types of antivortices evolutions are identified. • Antivortex generation can cause decrease of Walker breakdown field. • The phase diagrams on the field-width plane are obtained.
Magnetic anisotropy in rapidly quenched amorphous glass-coated nanowires
Energy Technology Data Exchange (ETDEWEB)
Óvári, T.-A.; Rotărescu, C.; Atițoaie, A.; Corodeanu, S.; Lupu, N., E-mail: nicole@phys-iasi.ro; Chiriac, H.
2016-07-15
Results on the roles played by the magnetoelastic and magnetostatic anisotropy terms in the magnetic behavior of glass-coated magnetostrictive amorphous nanowires prepared by means of rapid solidification are reported. Their contributions have been analyzed both experimentally, through hysteresis loop measurements, and theoretically, using micromagnetic simulations. All the investigated samples exhibit a magnetically bistable behavior, characterized by a single-step magnetization reversal when the applied field reaches a critical threshold value, called switching field. The combined interpretation of the experimental and theoretical data allows one to understand the effect of the magnetoelastic term on the value of the switching field, on one hand, and the effect of the magnetostatic term on the nucleation mechanism on the other, both with an essential impact on the characteristics of the nanowires’ magnetic bistability. The results are crucial for understanding the basic magnetic properties of these novel rapidly solidified ultrathin magnetic wires, as well as for tailoring their properties according to the specific requirements of various sensing applications. - Highlights: • Glass-coated nanowires have been very recently prepared by rapid solidification. • Amorphous wires change their properties as their diameter reaches the nano range. • Here we report on their main anisotropy terms: magnetoelastic and shape. • The results are essential for tailoring their properties for future applications.
Bhoi, Biswanath; Kim, Bosung; Kim, Junhoe; Cho, Young-Jun; Kim, Sang-Koog
2017-09-20
We experimentally demonstrate strongly enhanced coupling between excited magnons in an Yttrium Iron Garnet (YIG) film and microwave photons in an inverted pattern of split-ring resonator (noted as ISRR). The anti-crossing effects of the ISRR's photon mode and the YIG's magnon modes were found from |S 21 |-versus-frequency measurements for different strengths and directions of externally applied magnetic fields. The spin-number-normalized coupling strength (i.e. single spin-photon coupling) [Formula: see text] was determined to 0.194 Hz ([Formula: see text] = 90 MHz) at 3.7 GHz frequency. Furthermore, we found that additional fine features in the anti-crossing region originate from the excitation of different spin-wave modes (such as the magnetostatic surface and the backward-volume magnetostatic spin-waves) rather than the Kittel-type mode. These spin-wave modes, as coupled with the ISRR mode, modify the anti-crossing effect as well as their coupling strength. An equivalent circuit model very accurately reproduced the observed anti-crossing effect and its coupling strength variation with the magnetic field direction in the planar-geometry ISRR/YIG hybrid system. This work paves the way for the design of new types of high-gain magnon-photon coupling systems in planar geometry.
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, Ben [Department of Electrical Energy, Systems and Automation, Ghent University, Technologiepark 913, B-9052 Ghent-Zwijnaarde (Belgium); Fin, Samuele [Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, 44122 Ferrara (Italy); Pancaldi, Matteo [CIC nanoGUNE, E-20018 Donostia-San Sebastian (Spain); Vavassori, Paolo [CIC nanoGUNE, E-20018 Donostia-San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, E-48013 Bilbao (Spain); Sarella, Anandakumar [Physics Department, Mount Holyoke College, 211 Kendade, 50 College St., South Hadley, Massachusetts 01075 (United States); Bisero, Diego [Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, 44122 Ferrara (Italy); CNISM, Unità di Ferrara, 44122 Ferrara (Italy)
2016-05-28
Various proposals for future magnetic memories, data processing devices, and sensors rely on a precise control of the magnetization ground state and magnetization reversal process in periodically patterned media. In finite dot arrays, such control is hampered by the magnetostatic interactions between the nanomagnets, leading to the non-uniform magnetization state distributions throughout the sample while reversing. In this paper, we evidence how during reversal typical geometric arrangements of dots in an identical magnetization state appear that originate in the dominance of either Global Configurational Anisotropy or Nearest-Neighbor Magnetostatic interactions, which depends on the fields at which the magnetization reversal sets in. Based on our findings, we propose design rules to obtain the uniform magnetization state distributions throughout the array, and also suggest future research directions to achieve non-uniform state distributions of interest, e.g., when aiming at guiding spin wave edge-modes through dot arrays. Our insights are based on the Magneto-Optical Kerr Effect and Magnetic Force Microscopy measurements as well as the extensive micromagnetic simulations.
Tuning magnetic properties of magnetoelectric BiFeO 3-NiFe 2O 4 nanostructures
Crane, S. P.; Bihler, C.; Brandt, M. S.; Goennenwein, S. T. B.; Gajek, M.; Ramesh, R.
2009-02-01
Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.
Tuning magnetic properties of magnetoelectric BiFeO{sub 3}-NiFe{sub 2}O{sub 4} nanostructures
Energy Technology Data Exchange (ETDEWEB)
Crane, S.P. [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States)], E-mail: scrane@berkeley.edu; Bihler, C.; Brandt, M.S. [Walter Schottky Institut, Technische Universitaet Muenchen, D-85748 Garching (Germany); Goennenwein, S.T.B. [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching (Germany); Gajek, M. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Ramesh, R. [Department of Materials Science and Engineering, University of California, Berkeley, CA 94720 (United States); Department of Physics, University of California, Berkeley, CA 94720 (United States)
2009-02-15
Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe{sub 2}O{sub 4} pillars in a multiferroic BiFeO{sub 3} matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars.
Tuning magnetic properties of magnetoelectric BiFeO3-NiFe2O4 nanostructures
International Nuclear Information System (INIS)
Crane, S.P.; Bihler, C.; Brandt, M.S.; Goennenwein, S.T.B.; Gajek, M.; Ramesh, R.
2009-01-01
Multifunctional thin film nanostructures containing soft magnetic materials such as nickel ferrite are interesting for potential applications in microwave signal processing because of the possibility to shrink the size of device architecture and limit device power consumption. An essential prerequisite to future applications of such a system is a firm understanding of its magnetic properties. We show that nanostructures composed of ferrimagnetic NiFe 2 O 4 pillars in a multiferroic BiFeO 3 matrix can be tuned magnetically by altering the aspect ratio of the pillars by depositing films of varying thickness. Magnetic anisotropy is studied using ferromagnetic resonance, which shows that the uniaxial magnetic anisotropy in the growth direction changes sign upon increasing the film thickness. The magnitude of this anisotropy contribution can be explained via a combination of shape and magnetostatic effects, using the object-oriented micromagnetic framework (OOMMF). The key factors determining the magnetic properties of the films are shown to be the aspect ratio of individual pillars and magnetostatic interactions between neighboring pillars
Study of synthetic ferrimagnet-synthetic antiferromagnet structures for magnetic sensor application
Guedes, A.; Mendes, M. J.; Freitas, P. P.; Martins, J. L.
2006-04-01
There has been a growing interest in using both synthetic ferrimagnet (SF) free and synthetic antiferromagnet (SAF) pinned layers for head and memory applications. In particular, for linear sensor applications, these structures lower the magnetostatic fields present at the free layer through the reduction of its effective thickness (teffSF). This allows higher sensitivity but at the expense of an increased offset field H0(Néel coupling field Hf+interlayer demagnetizing field HdSAF). In this work, results on a series of patterned 3×1 and 6×2 μm2 top-pinned SF-SAF spin valves are analyzed and compared with a three-dimensional micromagnetic simulation in order to clarify the role of the different ferromagnetic layers in the overall offset field and sensitivity. H0 varies as 1/teffSF[teffSF=(Mata-Mbtb)/MeffSF]. The magnetostatic field acting on the SF coming from the SAF (HdSAF) can act as a biasing field, partially counterbalancing the Néel coupling field (Hf) leading to a reduction of H0. In this work the offset field was reduced from an initial value of 25 Oe in a quasicompensated SAF to a value of -6 Oe, by unbalancing the SAF and consequently increasing its effective moment (teffSF=15 A˚).
Self-Assembly of Flux-Closure Polygons from Magnetite Nanocubes.
Szyndler, Megan W; Corn, Robert M
2012-09-06
Well-defined nanoscale flux-closure polygons (nanogons) have been fabricated on hydrophilic surfaces from the face-to-face self-assembly of magnetite nanocubes. Uniform ferrimagnetic magnetite nanocubes (∼86 nm) were synthesized and characterized with a combination of electron microscopy, diffraction, and magnetization measurements. The nanocubes were subsequently cast onto hydrophilic substrates, wherein the cubes lined up face-to-face and formed a variety of polygons due to magnetostatic and hydrophobic interactions. The generated surfaces consist primarily of three- and four-sided nanogons; polygons ranging from two to six sides were also observed. Further examination of the nanogons showed that the constraints of the face-to-face assembly of nanocubes often led to bowed sides, strained cube geometries, and mismatches at the acute angle vertices. Additionally, extra nanocubes were often present at the vertices, suggesting the presence of external magnetostatic fields at the polygon corners. These nanogons are inimitable nanoscale magnetic structures with potential applications in the areas of magnetic memory storage and high-frequency magnetics.
Quantal density functional theory. 2. ed.
Energy Technology Data Exchange (ETDEWEB)
Sahni, Viraht
2016-07-01
This book is on quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The time-independent QDFT constitutes a special case. The 2{sup nd} edition describes the further development of the theory, and extends it to include the presence of an external magnetostatic field. The theory is based on the 'quantal Newtonian' second and first laws for the individual electron. These laws are in terms of 'classical' fields that pervade all space, and their quantal sources. The fields are separately representative of the electron correlations that must be accounted for in local potential theory. Recent developments show that irrespective of the type of external field the electrons are subject to, the only correlations beyond those due to the Pauli exclusion principle and Coulomb repulsion that need be considered are solely of the correlation-kinetic effects. Foundational to QDFT, the book describes Schroedinger theory from the new perspective of the single electron in terms of the 'quantal Newtonian' laws. Hohenberg-Kohn density functional theory (DFT), new understandings of the theory and its extension to the presence of an external uniform magnetostatic field are described. The physical interpretation via QDFT, in terms of electron correlations, of Kohn-Sham DFT, approximations to it and Slater theory are provided.
On absorption of low frequency electromagnetic fields
International Nuclear Information System (INIS)
Brunner, S.; Vaclavik, J.
1993-03-01
The drift kinetic equation (DKE) is used to establish a formula for power absorption of small amplitude, low frequency electromagnetic (EM) fields in a hot toroidal axisymmetric plasma. The stationary plasma is first considered. Electrons and ions are described by local Maxwellian distributions, alpha particles by a local slowing-down distribution. The fluctuating part of the distribution function for each species is then evaluated from the linearized DKE in terms of the EM fields using a perturbation method. The parameter b p =B p /B o , where B p is the poloidal component of the magnetostatic field B o , and the parameter v d /λω, where v d is the magnetic curvature drift, λ the wavelength perpendicular to B o and ω the frequency of the EM fields, are considered to be small. By integrating the resulting distribution function over velocity space, an explicit formula for the power absorbed by each species is obtained. To obtain an expression suitable for direct implementation in an ideal-MHD code, the electric field component parallel to the magnetostatic field is evaluated using the quasi-neutrality equation. (author) 4 refs
Preferential orientation of magnetization and interfacial disorder in Co/Au multilayers
Energy Technology Data Exchange (ETDEWEB)
Quispe-Marcatoma, J., E-mail: justinianoqm@gmail.com [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, P.O. Box 14–0149, Lima 14, Perú (Peru); Pandey, B. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Alayo, W. [Departamento de Física, Universidade Federal de Pelotas, Campus Universitário, 96010-900 Pelotas, RS (Brazil); Sousa, M.A. de; Pelegrini, F. [Instituto de Física, Universidade Federal de Goiás, Goiânia 74001-970 (Brazil); Saitovitch, E. Baggio [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil)
2013-10-15
Two families of Co/Au multilayer films with different interlayer magnetostatic coupling were grown by the DC magnetron sputtering technique. The structure of these films was analyzed by X-ray diffraction (XRD), and the magnetic properties by vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) spectroscopy. All these techniques give complementary information about the structure of the multilayers and the magnetization direction as a function of thickness of the Co layers. The structural analysis shows a decrease of the interfacial disorder for increasing Co layer thickness in both groups of samples. This behavior has been correlated with a transition of the magnetization direction from perpendicular to parallel to the films plane. Thin Co layer samples gave high remnant magnetization with very low saturation field while thick Co layer samples showed low remnant magnetization with high value of saturation field. In the FMR study, the spectra showed two resonance modes, which were associated to the internal and interfacial Co atoms. Volume (K{sub v}) and surface (K{sub s}) anisotropy constants were deduced from the FMR experiments and are in good agreement with the reported values for Co/Au multilayers. - Highlights: • We find a competition between the magnetostatic coupling and magnetic anisotropy. • We find two resonant modes associated to different environments of Co atoms. • The main mode shows perpendicular magnetic anisotropy for samples with t{sub Co}<10 Å. • The secondary mode shows in-plane anisotropy for samples with t{sub Co}<10 Å.
Non-invasive diagnostics of ion beams in strong toroidal magnetic fields with standard CMOS cameras
Ates, Adem; Ates, Yakup; Niebuhr, Heiko; Ratzinger, Ulrich
2018-01-01
A superconducting Figure-8 stellarator type magnetostatic Storage Ring (F8SR) is under investigation at the Institute for Applied Physics (IAP) at Goethe University Frankfurt. Besides numerical simulations on an optimized design for beam transport and injection a scaled down (0.6T) experiment with two 30°toroidal magnets is set up for further investigations. A great challenge is the development of a non-destructive, magnetically insensitive and flexible detector for local investigations of an ion beam propagating through the toroidal magnetostatic field. This paper introduces a new way of beam path measurement by residual gas monitoring. It uses a single board camera connected to a standard single board computer by a camera serial interface all placed inside the vacuum chamber. First experiments with one camera were done and in a next step two under 90 degree arranged cameras were installed. With the help of the two cameras which are moveable along the beam pipe the theoretical predictions are experimentally verified successfully. Previous experimental results have been confirmed. The transport of H+ and H2+ ion beams with energies of 7 keV and at beam currents of about 1 mA is investigated successfully.
Enhanced method of magnetic powder alignment for production of PLP Nd-Fe-B magnets
Energy Technology Data Exchange (ETDEWEB)
Popov, A.G. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation); Golovnia, O.A., E-mail: golovnya@imp.uran.ru [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation); Protasov, A.V. [M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Str. S. Kovalevskoy, 18, 620137 Ekaterinburg (Russian Federation); Institute of Natural Sciences and Mathematics, Ural Federal University, Av. Mira, 19, 620002 Ekaterinburg (Russian Federation)
2017-04-15
It is demonstrated how the high degree of powder alignment in PLP magnets can be achieved by loading the powder into a container placed in a magnetic field of moderate strength. The strip-cast alloy with a composition of 30.00 Nd, 1.95 Dy, 66.42 Fe, 0.99 B, 0.54 Co, 0.1 Ga (wt%) was subjected to hydrogen decrepitation and then milled in a vibratory mill in toluene to an average particle size of 2.9 µm determined by the FSSS method. The powder was compacted in the magnetic field of 0.2 – 1.2 T to the filling density 2.6 – 3.2×10{sup 3} kg/m{sup 3}. It is shown that loading the powder into a container placed in a magnetic field enhances the degree of powder alignment in sintered Nd-Fe-B magnets produced from non-pressed powder. At the filling density less than 3.2×10{sup 3} kg/m{sup 3}, the density of magnets is high but insufficient, because of the formation of magnetostatic chains of particles, which impedes the powder compaction. The simulation by the discrete-element method qualitatively proves that the magnetostatic interaction of the chains of particles that are formed in the course of loading in the magnetic field stimulates a decrease in the density of the sintered magnets and its non-uniform distribution over the sample. As a result of the optimization of the parameters of the alignment and compaction of the powder loaded in a magnetic field, PLP magnets with B{sub r} ≥1.34 T, H{sub c} ≥950 kA/m, (BH){sub max} ≥340 kJ/m{sup 3}, and the degree of alignment exceeding 96% were produced. - Highlights: • The pressless process (PLP) in magnet production is studied. • A new method of the loading of powder in an applied DC magnetic field is suggested. • The method allows achieving higher degree of alignment in moderate magnetic field. • Density of sintered magnets is studied experimentally and via DEM simulation. • Low density is caused by the formation of magnetostatic chains of powder particles.
Enhanced method of magnetic powder alignment for production of PLP Nd-Fe-B magnets
International Nuclear Information System (INIS)
Popov, A.G.; Golovnia, O.A.; Protasov, A.V.
2017-01-01
It is demonstrated how the high degree of powder alignment in PLP magnets can be achieved by loading the powder into a container placed in a magnetic field of moderate strength. The strip-cast alloy with a composition of 30.00 Nd, 1.95 Dy, 66.42 Fe, 0.99 B, 0.54 Co, 0.1 Ga (wt%) was subjected to hydrogen decrepitation and then milled in a vibratory mill in toluene to an average particle size of 2.9 µm determined by the FSSS method. The powder was compacted in the magnetic field of 0.2 – 1.2 T to the filling density 2.6 – 3.2×10 3 kg/m 3 . It is shown that loading the powder into a container placed in a magnetic field enhances the degree of powder alignment in sintered Nd-Fe-B magnets produced from non-pressed powder. At the filling density less than 3.2×10 3 kg/m 3 , the density of magnets is high but insufficient, because of the formation of magnetostatic chains of particles, which impedes the powder compaction. The simulation by the discrete-element method qualitatively proves that the magnetostatic interaction of the chains of particles that are formed in the course of loading in the magnetic field stimulates a decrease in the density of the sintered magnets and its non-uniform distribution over the sample. As a result of the optimization of the parameters of the alignment and compaction of the powder loaded in a magnetic field, PLP magnets with B r ≥1.34 T, H c ≥950 kA/m, (BH) max ≥340 kJ/m 3 , and the degree of alignment exceeding 96% were produced. - Highlights: • The pressless process (PLP) in magnet production is studied. • A new method of the loading of powder in an applied DC magnetic field is suggested. • The method allows achieving higher degree of alignment in moderate magnetic field. • Density of sintered magnets is studied experimentally and via DEM simulation. • Low density is caused by the formation of magnetostatic chains of powder particles.
Macroscopic simulation of isotropic permanent magnets
International Nuclear Information System (INIS)
Bruckner, Florian; Abert, Claas; Vogler, Christoph; Heinrichs, Frank; Satz, Armin; Ausserlechner, Udo; Binder, Gernot; Koeck, Helmut; Suess, Dieter
2016-01-01
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. - Highlights: • Simulations of isotropic permanent magnets. • Accurate calculation of remanence magnetization and strayfield. • Comparison with strayfield measurements and anisotropic magnet simulations. • Efficient 3D FEM–BEM coupling for solution of Maxwell equations.
Hugon, Cedric; D'Amico, Francesca; Aubert, Guy; Sakellariou, Dimitris
2010-07-01
Starting from general results of magnetostatics, we give fundamental considerations on the design and characterization of permanent magnets for NMR based on harmonic analysis and symmetry. We then propose a simple geometry that takes advantage of some of these considerations and discuss the practical aspects of the assembly of a real magnet based on this geometry, involving the characterization of its elements, the optimization of the layout and the correction of residual inhomogeneities due to material and geometry imperfections. We report with this low-cost, light-weight magnet (100 euros and 1.8 kg including the aluminum frame) a field of 120 mT (5.1 MHz proton) with a 10 ppm natural homogeneity over a sphere of 1.5 mm in diameter. Copyright (c) 2010 Elsevier Inc. All rights reserved.
Sakellariou, Dimitris; Hugon, Cédric; Guiga, Angelo; Aubert, Guy; Cazaux, Sandrine; Hardy, Philippe
2010-12-01
We introduce a cylindrical permanent magnet design that generates a homogeneous and strong magnetic field having an arbitrary inclination with respect to the axis of the cylinder. The analytical theory of 3 D magnetostatics has been applied to this problem, and a hybrid magnet structure has been designed. This structure contains two magnets producing a longitudinal and transverse component for the magnetic field, whose amplitudes and homogeneities can be fully controlled by design. A simple prototype has been constructed using inexpensive small cube magnets, and its magnetic field has been mapped using Hall and NMR probe sensors. This magnet can, in principle, be used for magic angle field spinning NMR and MRI experiments allowing for metabolic chemical shift profiling in small living animals. Copyright © 2010 John Wiley & Sons, Ltd.
Mathematical models and numerical simulation in electromagnetism
Bermúdez, Alfredo; Salgado, Pilar
2014-01-01
The book represents a basic support for a master course in electromagnetism oriented to numerical simulation. The main goal of the book is that the reader knows the boundary-value problems of partial differential equations that should be solved in order to perform computer simulation of electromagnetic processes. Moreover it includes a part devoted to electric circuit theory based on ordinary differential equations. The book is mainly oriented to electric engineering applications, going from the general to the specific, namely, from the full Maxwell’s equations to the particular cases of electrostatics, direct current, magnetostatics and eddy currents models. Apart from standard exercises related to analytical calculus, the book includes some others oriented to real-life applications solved with MaxFEM free simulation software.
Theoretical physics 3 electrodynamics
Nolting, Wolfgang
2016-01-01
This textbook offers a clear and comprehensive introduction to electrodynamics, one of the core components of undergraduate physics courses. It follows on naturally from the previous volumes in this series. The first part of the book describes the interaction of electric charges and magnetic moments by introducing electro- and magnetostatics. The second part of the book establishes deeper understanding of electrodynamics with the Maxwell equations, quasistationary fields and electromagnetic fields. All sections are accompanied by a detailed introduction to the math needed. Ideally suited to undergraduate students with some grounding in classical and analytical mechanics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful Germa...
Directory of Open Access Journals (Sweden)
Vahid Behjat
2014-12-01
Full Text Available This research work develops dynamic model of a gearless small scale wind power generation system based on a direct driven single sided outer rotor AFPMSG with coreless armature winding. Dynamic modeling of the AFPMSG based wind turbine requires machine parameters. To this end, a 3D FEM model of the generator is developed and from magnetostatic and transient analysis of the FEM model, machine parameters are calculated and utilized in dynamic modeling of the system. A maximum power point tracking (MPPT-based FOC control approach is used to obtain maximum power from the variable wind speed. The simulation results show the proper performance of the developed dynamic model of the AFPMSG, control approach and power generation system.
Thermal stability of bubble domains in ferromagnetic discs
Energy Technology Data Exchange (ETDEWEB)
Hrkac, G [University of Sheffield, Engineering Materials, Mappin Street, Sheffield S1 3JD (United Kingdom) ; Bance, S [University of Sheffield, Engineering Materials, Mappin Street, Sheffield S1 3JD (United Kingdom) ; Goncharov, A [University of Sheffield, Engineering Materials, Mappin Street, Sheffield S1 3JD (United Kingdom) ; Schrefl, T [University of Sheffield, Engineering Materials, Mappin Street, Sheffield S1 3JD (United Kingdom) ; Suess, D [Vienna University of Technology, Wiedner Hauptstr. 8-10e, A-1040 Vienna (Austria)
2007-05-07
The transition and thermal stability of disc-shaped ferromagnetic particles at the temperature of T = 300 K with a uniaxial anisotropy along the symmetry axis from a bi-domain to a single domain state has been studied. The nudge elastic band method was used to map the energy landscape and to calculate the energy barrier between the transition states. For single FePt disc-shaped particles with perpendicular anisotropy three transition configurations have been found: single domain, stripe- and stable bubble domains at zero applied field. The single domain configuration along the positive anisotropy axis is reached by an annihilation process of the domain wall and the all-down state by a complex domain expansion process. Magnetization configurations in two interacting discs show an increase in thermal stability compared with single disc systems, which is attributed to the interacting magnetostatic energy between the two particles.
3D field calculation of the GEM prototype magnet and comparison with measurements
Energy Technology Data Exchange (ETDEWEB)
Lari, R.J.
1983-10-28
The proposed 4 GeV Electron Microtron (GEM) is designed to fill the existing buildings left vacant by the demise of the Zero Gradient Synchrotron (ZGS) accelerator. One of the six large dipole magnets is shown as well as the first 10 electron orbits. A 3-orbit prototype magnet has been built. The stepped edge of the magnet is to keep the beam exiting perpendicular to the pole. The end guards that wrap around the main coils are joined together by the 3 shield plates. The auxiliary coils are needed to keep the end guards and shield plates from saturating. A 0.3 cm Purcell filter air gap exists between the pole and the yoke. Can anyone question this being a truly three-dimensional magnetostatic problem. The computer program TOSCA, developed at the Rutherford Appleton Laboratory by the Computing Applications Group, was used to calculate this magnet and the results have been compared with measurements.
3D field calculation of the GEM prototype magnet and comparison with measurements
International Nuclear Information System (INIS)
Lari, R.J.
1983-01-01
The proposed 4 GeV Electron Microtron (GEM) is designed to fill the existing buildings left vacant by the demise of the Zero Gradient Synchrotron (ZGS) accelerator. One of the six large dipole magnets is shown as well as the first 10 electron orbits. A 3-orbit prototype magnet has been built. The stepped edge of the magnet is to keep the beam exiting perpendicular to the pole. The end guards that wrap around the main coils are joined together by the 3 shield plates. The auxiliary coils are needed to keep the end guards and shield plates from saturating. A 0.3 cm Purcell filter air gap exists between the pole and the yoke. Can anyone question this being a truly three-dimensional magnetostatic problem. The computer program TOSCA, developed at the Rutherford Appleton Laboratory by the Computing Applications Group, was used to calculate this magnet and the results have been compared with measurements
Mechanical vibration to electrical energy converter
Kellogg, Rick Allen [Tijeras, NM; Brotz, Jay Kristoffer [Albuquerque, NM
2009-03-03
Electromechanical devices that generate an electrical signal in response to an external source of mechanical vibrations can operate as a sensor of vibrations and as an energy harvester for converting mechanical vibration to electrical energy. The devices incorporate a magnet that is movable through a gap in a ferromagnetic circuit, wherein a coil is wound around a portion of the ferromagnetic circuit. A flexible coupling is used to attach the magnet to a frame for providing alignment of the magnet as it moves or oscillates through the gap in the ferromagnetic circuit. The motion of the magnet can be constrained to occur within a substantially linear range of magnetostatic force that develops due to the motion of the magnet. The devices can have ferromagnetic circuits with multiple arms, an array of magnets having alternating polarity and, encompass micro-electromechanical (MEM) devices.
International Nuclear Information System (INIS)
Leboeuf, J.N.; Tajima, T.; Dawson, J.M.
1981-03-01
Two-and-one-half dimensional magnetostatic and electromagnetic particle simulations of time-varying magnetic x-points and the associated plasma response are reported. The stability and topology depend on the crossing angle of the field lines at the x-point, irrespective of the plasma β. The electrostatic field and finite Larmor radius effects play an important role in current penetration and shaping of the plasma flow. The snapping of the field lines, and dragging of the plasma into, and confinement of the plasma at, an o-point (magnetic island) is observed. Magnetic island coalescence with explosive growth of the coalescence mode occurs and is accompanied by a large increase of kinetic energy and temperature as well as the formation of hot tails on the distribution functions
Approximated solutions to Born-Infeld dynamics
Energy Technology Data Exchange (ETDEWEB)
Ferraro, Rafael [Instituto de Astronomía y Física del Espacio (IAFE, CONICET-UBA),Casilla de Correo 67, Sucursal 28, 1428 Buenos Aires (Argentina); Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,Ciudad Universitaria, Pabellón I, 1428 Buenos Aires (Argentina); Nigro, Mauro [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires,Ciudad Universitaria, Pabellón I, 1428 Buenos Aires (Argentina)
2016-02-01
The Born-Infeld equation in the plane is usefully captured in complex language. The general exact solution can be written as a combination of holomorphic and anti-holomorphic functions. However, this solution only expresses the potential in an implicit way. We rework the formulation to obtain the complex potential in an explicit way, by means of a perturbative procedure. We take care of the secular behavior common to this kind of approach, by resorting to a symmetry the equation has at the considered order of approximation. We apply the method to build approximated solutions to Born-Infeld electrodynamics. We solve for BI electromagnetic waves traveling in opposite directions. We study the propagation at interfaces, with the aim of searching for effects susceptible to experimental detection. In particular, we show that a reflected wave is produced when a wave is incident on a semi-space containing a magnetostatic field.
Morphology, magnetic and resonance properties of Fe/MgO multilayers
Energy Technology Data Exchange (ETDEWEB)
Garcia-Garcia, A; Algarabel, P A; Ibarra, M R [Instituto de Ciencia de Materiales de Aragon, Universidad de Zaragoza-CSIC 50009 Zaragoza (Spain); Vovk, A [Centro de Fisica da Materia Condensada Unversidade de Lisboa, Campo Grande Ed. C8, 1749-016, Lisboa (Portugal); Strichovanec, P; Pardo, J A; Magen, C [Instituto de Nanociencia de Aragon, Universidad de Zaragoza 50018 Zaragoza (Spain); Golub, V; Salyuk, O, E-mail: ayvovk@fc.ul.pt [Institute of Magnetism NAS of Ukraine, 36-b Vernnadsky blvd., 03142, Kyiv (Ukraine)
2011-07-06
Magnetic, resonance and transport properties of Fe(t nm)/MgO(3.0 nm) multilayers prepared by pulsed laser deposition were investigated. Comparison of the data allows conclusions on Fe layers morphology. For t<0.61 nm typical features of granular cermet films in dielectric regime are observed, i.e. high electrical resistance, isotropic magnetoresistance and strong temperature dependence of magnetization. For higher t coalescence of Fe granules occurs and metallic percolation cluster is formed at t{approx}0.81 nm. This is manifested by rapid decrease of films resistance and formation of multipeak ferromagnetic resonance spectra. For t>1.25 nm a continuous coverage of MgO by Fe takes place. However, the morphology of Fe layers is rough. This causes the appearance of magnetostatic resonance modes analogous to those observed for continuous films deposited on embossed surfaces.
Magnetic ground and remanent states of synthetic metamagnets with perpendicular anisotropy
International Nuclear Information System (INIS)
Kiselev, N S; Roessler, U K; Bogdanov, A N; Hellwig, O
2011-01-01
In this work, we summarize our theoretical results within a phenomenological micromagnetic approach for magnetic ground state and nonequilibrium states as topological magnetic defects in multilayers with strong perpendicular anisotropy and antiferromagnetic (AF) interlayer exchange coupling (IEC), e.g. [Co/Pt(Pd)]/Ru(Ir, NiO). We give detailed analysis of our model together with the most representative results which elucidate common features of such systems. We discuss phase diagrams of the magnetic ground state, and compare solutions of our model with experimental data. A model to assess the stability of so-called tiger tail patterns is presented. It is found that these modulated topological defect cannot be stabilized by an interplay between magnetostatic and IEC energies only. It is argued that tiger tail patterns arise as nuclei of ferro-stripe structure in AF domain walls and that they are stabilized by domain wall pinning.
New ideas for axion like particle dark matter search
Betz, Michael; Zioutas, Konstantin
2012-01-01
In the context of finding suitable large magnets for RF and microwave axion search, the Tore supra ring had been proposed. This Tokamak which could probably be made available for DM search has a huge volume and a strong magnetic field (30000 liter and 4.5 Tesla). It appears on a first glance, as an interesting candidate for this kind of experiment. One can find a suitable microwave mode which meets the condition that the RF electric field is parallel to the magnetostatic field. The eigenfrequency field pattern and Q factor for this mode and a few adjacent ones are calculated the some field patterns shown graphically. The use of the torus type cavity is not restricted to the Tore Supra. It can in principle be applied to any torus type structure also scaled up toward smaller dimensions and higher frequencies. In the second part of the slide presentation some alternatives and other cavity magnet concepts are shown and discussed.
International Nuclear Information System (INIS)
Balandin, V.; Decking, W.; Golubeva, N.
2014-09-01
We show that if in the particle beam there are linear correlations between energy of particles and their transverse positions and momenta (linear beam dispersions), then the transverse projected emittances always can be reduced by letting the beam to pass through magnetostatic system with specially chosen nonzero lattice dispersions. The maximum possible reduction of the transverse projected emittances occurs when all beam dispersions are zeroed, and the values of the lattice dispersions required for that are completely defined by the values of the beam dispersions and the beam rms energy spread and are independent from any other second-order central beam moments. Besides that, we prove that, alternatively, one can also use the lattice dispersions to remove linear correlations between longitudinal positions of particles and their transverse coordinates (linear beam tilts), but in this situation solution for the lattice dispersions is nonunique and the reduction of the transverse projected emittances is not guaranteed.
A double-layer based model of ion confinement in electron cyclotron resonance ion source
Energy Technology Data Exchange (ETDEWEB)
Mascali, D., E-mail: davidmascali@lns.infn.it; Neri, L.; Celona, L.; Castro, G.; Gammino, S.; Ciavola, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Torrisi, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell’Informazione, delle Infrastrutture e dell’Energia Sostenibile, Via Graziella, I-89100 Reggio Calabria (Italy); Sorbello, G. [Istituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica, Viale Andrea Doria 6, 95125 Catania (Italy)
2014-02-15
The paper proposes a new model of ion confinement in ECRIS, which can be easily generalized to any magnetic configuration characterized by closed magnetic surfaces. Traditionally, ion confinement in B-min configurations is ascribed to a negative potential dip due to superhot electrons, adiabatically confined by the magneto-static field. However, kinetic simulations including RF heating affected by cavity modes structures indicate that high energy electrons populate just a thin slab overlapping the ECR layer, while their density drops down of more than one order of magnitude outside. Ions, instead, diffuse across the electron layer due to their high collisionality. This is the proper physical condition to establish a double-layer (DL) configuration which self-consistently originates a potential barrier; this “barrier” confines the ions inside the plasma core surrounded by the ECR surface. The paper will describe a simplified ion confinement model based on plasma density non-homogeneity and DL formation.
Magnetic response to applied electrostatic field in external magnetic field
Energy Technology Data Exchange (ETDEWEB)
Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)
2014-04-15
We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to the simple example of a spherically symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space; the pattern of the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics. (orig.)
Self-generation of dissipative solitons in magnonic quasicrystal active ring resonator
International Nuclear Information System (INIS)
Grishin, S. V.; Beginin, E. N.; Morozova, M. A.; Sharaevskii, Yu. P.; Nikitov, S. A.
2014-01-01
Self-generation of dissipative solitons in the magnonic quasicrystal (MQC) active ring resonator is studied theoretically and experimentally. The developed magnonic crystal has quasiperiodic Fibonacci type structure. Frequency selectivity of the MQC together with the parametric three-wave decay of magnetostatic surface spin wave (MSSW) leads to the dissipative soliton self-generation. The transfer matrix method is used to describe MQC transmission responses. Besides, the model of MQC active ring resonator is suggested. The model includes three coupled differential equations describing the parametric decay of MSSW and two differential equations of linear oscillators describing the frequency selectivity of MQC. Numerical simulation results of dissipative soliton self-generation are in a fair agreement with experimental data
Directory of Open Access Journals (Sweden)
G. Shimon
2015-09-01
Full Text Available A direct and systematic investigation of the magnetization dynamics in individual circular Ni80Fe20 disk of diameter (D in the range from 300 nm to 1 μm measured using micro-focused Brillouin Light Scattering (μ-BLS spectroscopy is presented. At high field, when the disks are in a single domain state, the resonance frequency of the uniform center mode is observed to reduce with reducing disk’s diameter. For D = 300 nm, additional edge and end-domains resonant modes are observed due to size effects. At low field, when the disks are in a vortex state, a systematic increase of resonant frequency of magnetostatic modes in a vortex state with the square root of the disks’ aspect ratio (thickness divided by radius is observed. Such dependence diminishes for disks with larger aspect ratio due to an increasing exchange energy contribution. Micromagnetic simulations are in excellent agreement with the experiments.
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
1979-11-01
The SLAC Electron Trajectory Program is described and instructions and examples for users are given. The program is specifically written to compute trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes. Either rectangular or cylindrically symmetric geometry may be used. Magntic fields may be specified using arbitrary configurations of coils, or the output of a magnet program such as Poisson or by an externally calculated array of the axial fields. The program is available in IBM FORTRAN but can be easily converted for use on other brands of hardware. The program is intended to be used with a plotter whose interface the user must provide
Large-Strain Transparent Magnetoactive Polymer Nanocomposites
Meador, Michael A.
2012-01-01
A document discusses polymer nano - composite superparamagnetic actuators that were prepared by the addition of organically modified superparamagnetic nanoparticles to the polymer matrix. The nanocomposite films exhibited large deformations under a magnetostatic field with a low loading level of 0.1 wt% in a thermoplastic polyurethane elastomer (TPU) matrix. The maximum actuation deformation of the nanocomposite films increased exponentially with increasing nanoparticle concentration. The cyclic deformation actuation of a high-loading magnetic nanocomposite film was examined in a low magnetic field, and it exhibited excellent reproducibility and controllability. Low-loading TPU nanocomposite films (0.1-2 wt%) were transparent to semitransparent in the visible wavelength range, owing to good dispersion of the magnetic nanoparticles. Magnetoactuation phenomena were also demonstrated in a high-modulus, high-temperature polyimide resin with less mechanical deformation.
Design strategy for a tunable antenna on a partially magnetized ferrite LTCC substrate
Ghaffar, Farhan A.
2014-07-01
Typical microwave simulators cannot accurately predict the behavior of an antenna on a partially magnetized substrate as they assume the substrate to be in fully saturate state. In this work, a new simulation strategy aided by theoretical analysis, is presented to model a tunable patch antenna on a partially magnetized ferrite substrate through a combination of magnetostatic and microwave simulators. An antenna prototype is fabricated in Ferrite LTCC medium to verify the partially magnetized state simulations. The measured results are in close agreement with the simulations, contrary to the case where the substrate is assumed to be in saturation. The prototype designed for 13 GHz exhibits a tuning range of 10 % making it highly suitable for tunable and reconfigurable wireless applications.
Theory and design of a half-mode SIW Ferrite LTCC phase shifter
Ghaffar, Farhan A.
2015-05-01
A half mode SIW based Ferrite LTCC phase shifter is presented in this work. A theoretical model to predict the phase shift in the partially magnetized state has been derived. Contrary to the bulky external magnets employed by conventional ferrite phase shifters for biasing, this design uses bias windings embedded within the ferrite substrate. This not only enables miniaturization but also reduces the required bias fields considerably by avoiding the demagnetization effect (fields lost at air-dielectric interface for external biasing schemes). The design is optimized with the aid of magnetostatic and microwave simulations which are later verified through measurements of a prototype. The fabricated phase shifter provides a differential phase shift of 110°/cm and an FoM of 55°/dB for an applied DC current of 240 mA.
Two Models of Magnetic Support for Photoevaporated Molecular Clouds
International Nuclear Information System (INIS)
Ryutov, D; Kane, J; Mizuta, A; Pound, M; Remington, B
2004-01-01
The thermal pressure inside molecular clouds is insufficient for maintaining the pressure balance at an ablation front at the cloud surface illuminated by nearby UV stars. Most probably, the required stiffness is provided by the magnetic pressure. After surveying existing models of this type, we concentrate on two of them: the model of a quasi-homogeneous magnetic field and the recently proposed model of a ''magnetostatic turbulence''. We discuss observational consequences of the two models, in particular, the structure and the strength of the magnetic field inside the cloud and in the ionized outflow. We comment on the possible role of reconnection events and their observational signatures. We mention laboratory experiments where the most significant features of the models can be tested
Surface modification of YIG by magnet array
International Nuclear Information System (INIS)
Atalay, S.; Kolat, V.S.; Bakır, H.G.; Izgi, T.; Kaya, A.O.; Kaya, O.A.; Gencer, H.
2015-01-01
Highlights: • The surface of YIG films were magnetically modulated by magnet array. • The surface modulated YIG films formed sharp band gaps. • A very small magnetic field change leads a large change in the peak value of band gap frequency. - Abstract: In this work, magnetostatic surface spin waves (MSSW) were propagated along the single crystal YIG (Y_3Fe_5O_1_2) film grown on GGG substrate. In order to obtain magnonic crystals, unlike the conventional methods, the surface of YIG films were magnetically modulated by magnet array in one and two-dimensions. The surface modulated YIG films formed sharp band gaps at approximately 6.55 GHz and 6.58 GHz at 1600 Oe magnetic field for one and two-dimensional magnonic crystals, respectively. It was found that a very small magnetic field change leads a large change in the peak value of band gap frequency.
Quantal density functional theory
Sahni, Viraht
2016-01-01
This book deals with quantal density functional theory (QDFT) which is a time-dependent local effective potential theory of the electronic structure of matter. The treated time-independent QDFT constitutes a special case. In the 2nd edition, the theory is extended to include the presence of external magnetostatic fields. The theory is a description of matter based on the ‘quantal Newtonian’ first and second laws which is in terms of “classical” fields that pervade all space, and their quantal sources. The fields, which are explicitly defined, are separately representative of electron correlations due to the Pauli exclusion principle, Coulomb repulsion, correlation-kinetic, correlation-current-density, and correlation-magnetic effects. The book further describes Schrödinger theory from the new physical perspective of fields and quantal sources. It also describes traditional Hohenberg-Kohn-Sham DFT, and explains via QDFT the physics underlying the various energy functionals and functional derivatives o...
Micromagnetic simulation of two-body magnetic nanoparticles
Li, Fei; Lu, Jincheng; Yang, Yu; Lu, Xiaofeng; Tang, Rujun; Sun, Z. Z.
2017-05-01
Field-induced magnetization dynamics was investigated in a system of two magnetic nanoparticles with uniaxial anisotropies and magnetostatic interaction. By using the micromagnetic simulation, ultralow switching field strength was found when the separation distance between the two particles reaches a critical small value on nanometer scale in the perpendicular configuration where the anisotropic axes of the two particles are perpendicular to the separation line. The switching field increases sharply when the separation is away from the critical distance. The same results were observed when varying the radius of particles. The micromagnetic results are consistent with the previous theoretical prediction where dipolar interaction between two single-domain magnetic particles was considered. Our present simulations offered further proofs and possibilities for the low-power applications of information storage as the two-body magnetic nanoparticles could be implemented as a composite information bit.
Magnetic domains in Ni-Mn-Ga martensitic thin films
International Nuclear Information System (INIS)
Chernenko, V A; Anton, R Lopez; Kohl, M; Ohtsuka, M; Orue, I; Barandiaran, J M
2005-01-01
A series of martensitic Ni 52 Mn 24 Ga 24 thin films deposited on alumina ceramic substrates has been prepared by using RF(radio-frequency) magnetron sputtering. The film thickness, d, varies from 0.1 to 5.0m. Magnetic domain patterns have been imaged by the MFM (magnetic force microscopy) technique. A maze domain structure is found for all studied films. MFM shows a large out-of-plane magnetization component and a rather uniform domain width for each film thickness. The domain width, δ, depends on the film thickness as δ∝√d in the whole studied range of film thickness. This dependence is the expected one for magnetic anisotropy and magnetostatic contributions in a perpendicular magnetic domain configuration. The proportionality coefficient is also consistent with the values of saturation magnetization and magnetic anisotropy determined in the samples
International Nuclear Information System (INIS)
Chatelier, Michel.
1976-01-01
A simple mechanical model is used to investigate the various physical mechanisms originating the echoes. The model is applied to nuclear spins and echoes from particles trapped in a magnetostatic well. The theory of echoes from trapped ions in a magnetic machine is developed. The effects that may be observed when two magnetic perturbations are applied to the plasma are described. Diffusion effects in the velocity space are then taken into account when the diffusion is due either to Coulomb collisions or to a microturbulence at the ion cyclotron frequency. The experimental results obtained with the DECA II B machine are described. Emphasis is put upon the effects observed when magnetic perturbations are applied to the plasma and echoes observation independently of the diffusion study, as it is the first time that trapped particle echoes are observed in a hot plasma [fr
Spin wave propagation in perpendicularly magnetized nm-thick yttrium iron garnet films
Chen, Jilei; Heimbach, Florian; Liu, Tao; Yu, Haiming; Liu, Chuanpu; Chang, Houchen; Stückler, Tobias; Hu, Junfeng; Zeng, Lang; Zhang, Youguang; Liao, Zhimin; Yu, Dapeng; Zhao, Weisheng; Wu, Mingzhong
2018-03-01
Magnonics offers a new way for information transport that uses spin waves (SWs) and is free of charge currents. Unlike Damon-Eshbach SWs, the magneto-static forward volume SWs offer the reciprocity configuration suitable for SW logic devices with low power consumption. Here, we study forward volume SW propagation in yttrium iron garnet (YIG) thin films with an ultra-low damping constant α = 8 ×10-5 . We design different integrated microwave antenna with different k-vector excitation distributions on YIG thin films. Using a vector network analyzer, we measured SW transmission with the films magnetized in perpendicular orientation. Based on the experimental results, we extract the group velocity as well as the dispersion relation of SWs and directly compare the power efficiency of SW propagation in YIG using coplanar waveguide and micro stripline for SW excitation and detection.
Surface modification of YIG by magnet array
Energy Technology Data Exchange (ETDEWEB)
Atalay, S., E-mail: satalay@inonu.edu.tr [Inonu University, Science and Art Faculty, Physics Department, 44280 Malatya (Turkey); Kolat, V.S. [Inonu University, Science and Art Faculty, Physics Department, 44280 Malatya (Turkey); Bakır, H.G. [Inonu University, Science and Art Faculty, Astronomy Department, 44280 Malatya (Turkey); Izgi, T.; Kaya, A.O. [Inonu University, Science and Art Faculty, Physics Department, 44280 Malatya (Turkey); Kaya, O.A. [Inonu University, Education Faculty, Computer Education and Educational Technology Department, 44280 Malatya (Turkey); Gencer, H. [Inonu University, Science and Art Faculty, Physics Department, 44280 Malatya (Turkey)
2015-11-01
Highlights: • The surface of YIG films were magnetically modulated by magnet array. • The surface modulated YIG films formed sharp band gaps. • A very small magnetic field change leads a large change in the peak value of band gap frequency. - Abstract: In this work, magnetostatic surface spin waves (MSSW) were propagated along the single crystal YIG (Y{sub 3}Fe{sub 5}O{sub 12}) film grown on GGG substrate. In order to obtain magnonic crystals, unlike the conventional methods, the surface of YIG films were magnetically modulated by magnet array in one and two-dimensions. The surface modulated YIG films formed sharp band gaps at approximately 6.55 GHz and 6.58 GHz at 1600 Oe magnetic field for one and two-dimensional magnonic crystals, respectively. It was found that a very small magnetic field change leads a large change in the peak value of band gap frequency.
The optical analogy for vector fields
Parker, E. N. (Editor)
1991-01-01
This paper develops the optical analogy for a general vector field. The optical analogy allows the examination of certain aspects of a vector field that are not otherwise readily accessible. In particular, in the cases of a stationary Eulerian flow v of an ideal fluid and a magnetostatic field B, the vectors v and B have surface loci in common with their curls. The intrinsic discontinuities around local maxima in absolute values of v and B take the form of vortex sheets and current sheets, respectively, the former playing a fundamental role in the development of hydrodyamic turbulence and the latter playing a major role in heating the X-ray coronas of stars and galaxies.
Triaxial fiber optic magnetic field sensor for MRI applications
Filograno, Massimo L.; Pisco, Marco; Catalano, Angelo; Forte, Ernesto; Aiello, Marco; Soricelli, Andrea; Davino, Daniele; Visone, Ciro; Cutolo, Antonello; Cusano, Andrea
2016-05-01
In this paper, we report a fiber-optic triaxial magnetic field sensor, based on Fiber Bragg Gratings (FBGs) integrated with giant magnetostrictive material, the Terfenol-D. The realized sensor has been designed and engineered for Magnetic Resonance Imaging (MRI) applications. A full magneto-optical characterization of the triaxial sensing probe has been carried out, providing the complex relationship among the FBGs wavelength shift and the applied magnetostatic field vector. Finally, the developed fiber optic sensors have been arranged in a sensor network composed of 20 triaxial sensors for mapping the magnetic field distribution in a MRI-room at a diagnostic center in Naples (SDN), equipped with Positron emission tomography/magnetic resonance (PET/MR) instrumentation. Experimental results reveal that the proposed sensor network can be efficiently used in MRI centers for performing quality assurance tests, paving the way for novel integrated tools to measure the magnetic dose accumulated day by day by MRI operators.
International Nuclear Information System (INIS)
Alija, A; Sobrado, I; Rodriguez-RodrIguez, G; Velez, M; Alameda, J M; MartIn, J I; Parrondo, J M R
2010-01-01
Micromagnetic simulations have been performed in uniaxial magnetic films with 2D array of asymmetric arrow shape holes. In order to understand the asymmetric pinning potential created by the holes, different boundary geometries conditions are used on the simulations. The depinning fields for forward and backward domain wall propagation have been calculated by the analysis of the energy landscapes as a function of the domain wall position. Domain wall depinning occurs preferentially at the free ends of the domain wall at the film boundaries. We have found that the domain wall propagation is different at the top/bottom boundaries of the simulated film which can be understood in terms of the magnetostatic energy and the chirality of the domain wall.
The mimetic finite difference method for elliptic problems
Veiga, Lourenço Beirão; Manzini, Gianmarco
2014-01-01
This book describes the theoretical and computational aspects of the mimetic finite difference method for a wide class of multidimensional elliptic problems, which includes diffusion, advection-diffusion, Stokes, elasticity, magnetostatics and plate bending problems. The modern mimetic discretization technology developed in part by the Authors allows one to solve these equations on unstructured polygonal, polyhedral and generalized polyhedral meshes. The book provides a practical guide for those scientists and engineers that are interested in the computational properties of the mimetic finite difference method such as the accuracy, stability, robustness, and efficiency. Many examples are provided to help the reader to understand and implement this method. This monograph also provides the essential background material and describes basic mathematical tools required to develop further the mimetic discretization technology and to extend it to various applications.
Unidirectional Spin-Wave-Propagation-Induced Seebeck Voltage in a PEDOT:PSS/YIG Bilayer
Wang, P.; Zhou, L. F.; Jiang, S. W.; Luan, Z. Z.; Shu, D. J.; Ding, H. F.; Wu, D.
2018-01-01
We clarify the physical origin of the dc voltage generation in a bilayer of a conducting polymer film and a micrometer-thick magnetic insulator Y3Fe5O12 (YIG) film under ferromagnetic resonance and/or spin wave excitation conditions. The previous attributed mechanism, the inverse spin Hall effect in the polymer [Nat. Mater. 12, 622 (2013), 10.1038/nmat3634], is excluded by two control experiments. We find an in-plane temperature gradient in YIG which has the same angular dependence with the generated voltage. Both vanish when the YIG thickness is reduced to a few nanometers. Thus, we argue that the dc voltage is governed by the Seebeck effect in the polymer, where the temperature gradient is created by the nonreciprocal magnetostatic surface spin wave propagation in YIG.
Oros Pop, Susana Teodora; Berinde, Ioan; Vadan, Ioan
2015-12-01
This paper presents the design and analysis of a permanent magnet moving coil type generator driven by a free piston Stirling engine. This assemble free piston Stirling engine - permanent magnet moving coil type generator will be used in a combined heat and power (CHP) system for producing heat and power in residential area. The design procedure for moving coil type linear generator starts from the rated power imposed and finally uses the Faraday law of induction. The magneto-static magnetic field generated by permanent magnets is analyzed by means of Reluctance method and Finite Element Method in order to evaluate the magnetic flux density in the air gap, which is a design data imposed in the design stage, and the results are compared.
A graphics-card implementation of Monte-Carlo simulations for cosmic-ray transport
Tautz, R. C.
2016-05-01
A graphics card implementation of a test-particle simulation code is presented that is based on the CUDA extension of the C/C++ programming language. The original CPU version has been developed for the calculation of cosmic-ray diffusion coefficients in artificial Kolmogorov-type turbulence. In the new implementation, the magnetic turbulence generation, which is the most time-consuming part, is separated from the particle transport and is performed on a graphics card. In this article, the modification of the basic approach of integrating test particle trajectories to employ the SIMD (single instruction, multiple data) model is presented and verified. The efficiency of the new code is tested and several language-specific accelerating factors are discussed. For the example of isotropic magnetostatic turbulence, sample results are shown and a comparison to the results of the CPU implementation is performed.
Dependence of Magnetic Field Quality on Collar Supplier and Dimensions in the Main LHC Dipole
Bellesia, B; Santoni, C; Todesco, E
2006-01-01
In order to keep the electro-magnetic forces and to minimize conductor movements, the superconducting coils of the main Large Hadron Collider dipoles are held in place by means of austenitic steel collars. Two suppliers provide the collars necessary for the whole LHC production, which has now reached more than 800 collared coils. In this paper we first assess if the different collar suppliers origin a noticeable difference in the magnetic field quality measured at room temperature. We then analyze the measurements of the collar dimensions carried out at the manufacturers, comparing them to the geometrical tolerances. Finally we use a magneto-static model to evaluate the expected spread in the field components induced by the actual collar dimensions. These spreads are compared to the magnetic measurements at room temperature over the magnet production in order to identify if the collars, rather than other components or assembly process, can account for the measured magnetic field effects. It has been found tha...
Computer simulations of magnetic fluids in laminar pipe flows
International Nuclear Information System (INIS)
Ramos, D.M.; Cunha, F.R.; Sobral, Y.D.; Fontoura Rodrigues, J.L.A.
2005-01-01
Finite volume method is adapted to simulate momentum and magnetic coupled equations of a laminar magnetic fluid flow. An evolution equation is used to calculate the fluid magnetization. Pressure-driven flow under steady and oscillatory magnetic field is investigated. The magnetostatic limit of the Maxwell's equations is treated in terms of a Poisson equation numerically integrated. The SIMPLE algorithm is used to calculate the pressure-velocity coupling when the pressure field is not prescribed. Suitable boundary conditions for velocity, magnetization and field intensity on the pipe wall are described. Results are obtained for velocity and pressure response under several conditions of the identified physical parameters of the flow. The simulations are verified by comparing numerical results and asymptotic theory, and they show a very good agreement
Approximated solutions to Born-Infeld dynamics
International Nuclear Information System (INIS)
Ferraro, Rafael; Nigro, Mauro
2016-01-01
The Born-Infeld equation in the plane is usefully captured in complex language. The general exact solution can be written as a combination of holomorphic and anti-holomorphic functions. However, this solution only expresses the potential in an implicit way. We rework the formulation to obtain the complex potential in an explicit way, by means of a perturbative procedure. We take care of the secular behavior common to this kind of approach, by resorting to a symmetry the equation has at the considered order of approximation. We apply the method to build approximated solutions to Born-Infeld electrodynamics. We solve for BI electromagnetic waves traveling in opposite directions. We study the propagation at interfaces, with the aim of searching for effects susceptible to experimental detection. In particular, we show that a reflected wave is produced when a wave is incident on a semi-space containing a magnetostatic field.
Design strategy for a tunable antenna on a partially magnetized ferrite LTCC substrate
Ghaffar, Farhan A.; Shamim, Atif; Bray, Joey R.
2014-01-01
Typical microwave simulators cannot accurately predict the behavior of an antenna on a partially magnetized substrate as they assume the substrate to be in fully saturate state. In this work, a new simulation strategy aided by theoretical analysis, is presented to model a tunable patch antenna on a partially magnetized ferrite substrate through a combination of magnetostatic and microwave simulators. An antenna prototype is fabricated in Ferrite LTCC medium to verify the partially magnetized state simulations. The measured results are in close agreement with the simulations, contrary to the case where the substrate is assumed to be in saturation. The prototype designed for 13 GHz exhibits a tuning range of 10 % making it highly suitable for tunable and reconfigurable wireless applications.
Resolution of unsteady Maxwell equations with charges in non convex domains
International Nuclear Information System (INIS)
Garcia, Emmanuelle
2002-01-01
This research thesis deals with the modelling and numerical resolution of problems related to plasma physics. The interaction of charged particles (electrons and ions) with electromagnetic fields is modelled with the system of unsteady Vlasov-Maxwell coupled equations (the Vlasov system describes the transport of charged particles and the Maxwell equations describe the wave propagation). The author presents definitions related to singular domains, establishes a Helmholtz decomposition in a space of electro-magnetostatic solutions. He reports a mathematical analysis of decompositions into a regular and a singular part of general functional spaces intervening in the investigation of the Maxwell system in complex geometries. The method is then implemented for bi-dimensional domains. A last part addressed the study and the numerical resolution of three-dimensional problems
Nonphonon mechanism of superconductivity in compounds of transition metals
International Nuclear Information System (INIS)
Ivanov, V.A.; Zaitsev, R.O.
1989-01-01
The kinematical mechanism of superconductivity is applied to the Emery-Hirsch model for the CuO 2 and BiO 3 layers. A superconducting region due to strong kinematic interaction of p- and s, d-electrons are determined as a function of n p and n s,d -degrees of non-filling of 2p 6 ,6s 2 ,3d 10 shells of O 2 - ,Bi 3 + ,Cu + . The T c is calculated taking into account the spin flip relaxation time. Magnetostatic properties of a superconducting state in a weak magnetic field are investigated. Coefficients of the Ginzburg-Landau equation are calculated. The ground state energy of the Emery-Hirsch model is also calculated
International Nuclear Information System (INIS)
Kordbacheh, A.; Ghahremaninezhad, Roghayeh; Maraghechi, B.
2012-01-01
A three-dimensional analysis of a novel free-electron laser (FEL) based upon a rectangular hybrid wiggler (RHW) is presented. This RHW is designed in a configuration composed of rectangular rings with alternating ferrite and dielectric spacers immersed in a solenoidal magnetic field. An analytic model of RHW is introduced by solution of Laplace's equation for the magnetostatic fields under the appropriate boundary conditions. The single-electron orbits in combined RHW and axial guide magnetic fields are studied when only the first and the third spatial harmonic components of the RHW field are taken into account and the higher order terms are ignored. The results indicate that the third spatial harmonic leads to group III orbits with a strong negative mass regime particularly in large solenoidal magnetic fields. RHW is found to be a promising candidate with favorable characteristics to be used in microwave FEL.
The influence of non-magnetocaloric properties on the AMR performance
DEFF Research Database (Denmark)
Nielsen, Kaspar Kirstein; Bahl, Christian; Smith, Anders
2012-01-01
The performance of Active Magnetic Regenerators (AMR) does not depend solely on the magnetocaloric effect of their constituents. Rather, it depends on several additional parameters, including, magnetic field, geometry (hydraulic diameter, cross-sectional area, regenerator length etc.), thermal pr...... a strong dependence on the orientation of the applied field and the regenerator geometry. Finally, the flow maldistribution of non-uniform regenerator geometries is found to degrade the AMR performance even at minor deviations from perfectly homogeneous regenerator matrices.......The performance of Active Magnetic Regenerators (AMR) does not depend solely on the magnetocaloric effect of their constituents. Rather, it depends on several additional parameters, including, magnetic field, geometry (hydraulic diameter, cross-sectional area, regenerator length etc.), thermal...... properties (conductivity, specific heat and mass density) and operating parameters (utilization, frequency, number of transfer units etc.). In this paper we focus on the influence of three parameters on regenerator performance: 1) Solid thermal conductivity, 2) magnetostatic demagnetization and 3) flow...
The influence of non-magnetocaloric properties on the performance in parallel-plate AMRs
DEFF Research Database (Denmark)
Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders
2014-01-01
a strong dependence on the orientation of the applied field and the regenerator geometry. Finally, the flow maldistribution of non-uniform regenerator geometries is found to degrade the AMR performance even at minor deviations from perfectly homogeneous regenerator matrices. This paper reflects a summary......The performance of Active Magnetic Regenerators (AMR) does not depend solely on the magnetocaloric effect of their constituents. Rather, it depends on several additional parameters, including, magnetic field, geometry (hydraulic diameter, cross-sectional area, regenerator length etc.), thermal...... properties (conductivity, specific heat and mass density) and operating parameters (utilization, frequency, number of transfer units etc.). In this paper we focus on the influence of three parameters on regenerator performance: 1) Solid thermal conductivity, 2) magnetostatic demagnetization and 3) flow...
Modeling the behaviour of shape memory materials under large deformations
Rogovoy, A. A.; Stolbova, O. S.
2017-06-01
In this study, the models describing the behavior of shape memory alloys, ferromagnetic materials and polymers have been constructed, using a formalized approach to develop the constitutive equations for complex media under large deformations. The kinematic and constitutive equations, satisfying the principles of thermodynamics and objectivity, have been derived. The application of the Galerkin procedure to the systems of equations of solid mechanics allowed us to obtain the Lagrange variational equation and variational formulation of the magnetostatics problems. These relations have been tested in the context of the problems of finite deformation in shape memory alloys and ferromagnetic materials during forward and reverse martensitic transformations and in shape memory polymers during forward and reverse relaxation transitions from a highly elastic to a glassy state.
Large-scale micromagnetics simulations with dipolar interaction using all-to-all communications
Directory of Open Access Journals (Sweden)
Hiroshi Tsukahara
2016-05-01
Full Text Available We implement on our micromagnetics simulator low-complexity parallel fast-Fourier-transform algorithms, which reduces the frequency of all-to-all communications from six to two times. Almost all the computation time of micromagnetics simulation is taken up by the calculation of the magnetostatic field which can be calculated using the fast Fourier transform method. The results show that the simulation time is decreased with good scalability, even if the micromagentics simulation is performed using 8192 physical cores. This high parallelization effect enables large-scale micromagentics simulation using over one billion to be performed. Because massively parallel computing is needed to simulate the magnetization dynamics of real permanent magnets composed of many micron-sized grains, it is expected that our simulator reveals how magnetization dynamics influences the coercivity of the permanent magnet.
Directory of Open Access Journals (Sweden)
Zhou Shao-Min
2011-01-01
Full Text Available Abstract In this study, for the first time, high-yield chain-like one-dimensional (1D Co nanostructures without any impurity have been produced by means of a solution dispersion approach under permanent-magnet. Size, morphology, component, and structure of the as-made samples have been confirmed by several techniques, and nanochains (NCs with diameter of approximately 60 nm consisting of single-crystalline Co and amorphous Co-capped layer (about 3 nm have been materialized. The as-synthesized Co samples do not include any other adulterants. The high-quality NC growth mechanism is proposed to be driven by magnetostatic interaction because NC can be reorganized under a weak magnetic field. Room-temperature-enhanced coercivity of NCs was observed, which is considered to have potential applications in spin filtering, high density magnetic recording, and nanosensors. PACS: 61.46.Df; 75.50; 81.07.Vb; 81.07.
Directory of Open Access Journals (Sweden)
Eduardo Ortega
2018-05-01
Full Text Available Magnetic nanostructures of different size, shape, and composition possess a great potential to improve current technologies like data storage and electromagnetic sensing. In thin ferromagnetic nanowires, their magnetization behavior is dominated by the competition between magnetocrystalline anisotropy (related to the crystalline structure and shape anisotropy. In this way electron diffraction methods like precession electron diffraction (PED can be used to link the magnetic behavior observed by Electron Holography (EH with its crystallinity. Using off-axis electron holography under Lorentz conditions, we can experimentally determine the magnetization distribution over neighboring nanostructures and their diamagnetic matrix. In the case of a single row of nickel nanowires within the alumina template, the thin TEM samples showed a dominant antiferromagnetic arrangement demonstrating long-range magnetostatic interactions playing a major role.
Ferrite LTCC based phased array antennas
Ghaffar, Farhan A.
2016-11-02
Two phased array antennas realized in multilayer ferrite LTCC technology are presented in this paper. The use of embedded bias windings in these designs allows the negation of external magnets which are conventionally employed with bulk ferrite medium. This reduces the required magnetostatic field strength by 90% as compared to the traditional designs. The phase shifters are implemented using the SIW technology. One of the designs is operated in the half mode waveguide topology while the other design is based on standard full mode waveguide operation. The two phase shifter designs are integrated with two element patch antenna array and slotted SIW array respectively. The array designs demonstrate a beam steering of 30° and ±19° respectively for a current excitation of 200 mA. The designs, due to their small factor can be easily integrated in modern communication systems which is not possible in the case of bulk ferrite based designs.
Xing, X J; Zhang, D; Li, S W
2012-12-14
We have investigated the tunneling of dipole-exchange spin waves across an air gap in submicrometer-sized permalloy magnetic strips by means of micromagnetic simulations. The magnetizations beside the gap could form three distinct end-domain states with various strengths of dipolar coupling. Spin-wave tunneling through the gap at individual end-domain states is studied. It is found that the tunneling behavior is strongly dependent on these domain states. Nonmonotonic decay of transmission of spin waves with the increase of the gap width is observed. The underlying mechanism for these behaviors is proposed. The tunneling characteristics of the dipole-exchange spin waves differ essentially from those of the magnetostatic ones reported previously.
Atomic spin resonance in a rubidium beam obliquely incident to a transmission magnetic grating
International Nuclear Information System (INIS)
Hatakeyama, A; Goto, K
2016-01-01
We studied atomic spin resonance induced by atomic motion in a spatially periodic magnetostatic field. A rubidium atomic beam, with a velocity of about 400 m s −1 , was obliquely incident to a transmission magnetic grating that produced a spatially periodic magnetic field. The magnetic grating was formed by a magnetic thin film on a polyimide substrate that had multiple slits at 150 μm intervals. The atoms experienced field oscillation, depending on their velocity and the field period when passing through the grating, and underwent magnetic resonance. Resonance spectra obtained with a perpendicular magnetization film were in clear contrast to ones obtained with an in-plane magnetization film. The former exhibited resonance peaks at odd multiples of the frequency, determined by the velocity over the period, while the latter had dips at the same frequencies. (paper)
International Nuclear Information System (INIS)
Razavi, Soheil; Shooshtari, Alireza
2014-01-01
Free vibration of a simply-supported magneto-electro-elastic doubly-curved thin shell resting on a Pasternak foundation is investigated based on Donnell theory. The rotary inertia effect is considered in the formulation. Maxwell equations for electrostatics and magnetostatics are used to model the electric and magnetic behavior. The partial differential equations of motion are reduced to a single ordinary differential equation and an analytical relation is obtained for the natural frequency. After validation of the present study, several numerical studies is done to investigate the effects of the electric and magnetic potentials, spring and shear coefficients of the Pasternak foundation, and the geometry of the shell on the vibration frequency. (paper)
Vacuum polarization of the electromagnetic field near a rotating black hole
International Nuclear Information System (INIS)
Frolov, V.P.; Zel'nikov, A.I.
1985-01-01
The electromagnetic field contribution to the vacuum polarization near a rotating black hole is considered. It is shown that the problem of calculating the renormalized average value of the stress-energy tensor /sup ren/ for the Hartle-Hawking vacuum state at the pole of the event horizon can be reduced to the problem of electro- and magnetostatics in the Kerr spacetime. An explicit expression for /sup ren/ at the pole of the event horizon is obtained and its properties are discussed. It is shown that in the case of a nonrotating black hole the Page-Brown approximation for the electromagnetic stress-energy tensor gives a result which coincides at the event horizon with the exact value of /sup ren/. .AE
A thick-walled sphere rotating in a uniform magnetic field: The next step to de-spin a space object
Nurge, Mark A.; Youngquist, Robert C.; Caracciolo, Ryan A.; Peck, Mason; Leve, Frederick A.
2017-08-01
Modeling the interaction between a moving conductor and a static magnetic field is critical to understanding the operation of induction motors, eddy current braking, and the dynamics of satellites moving through Earth's magnetic field. Here, we develop the case of a thick-walled sphere rotating in a uniform magnetic field, which is the simplest, non-trivial, magneto-statics problem that leads to complete closed-form expressions for the resulting potentials, fields, and currents. This solution requires knowledge of all of Maxwell's time independent equations, scalar and vector potential equations, and the Lorentz force law. The paper presents four cases and their associated experimental results, making this topic appropriate for an advanced student lab project.
Transparency of magnetized plasma at the cyclotron frequency
International Nuclear Information System (INIS)
Shvets, G.; Wurtele, J.S.
2002-01-01
Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator, or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of nonlocal plasma oscillation. A Lagrangian description was used to elucidate the physics of the plasma transparency and control of group and phase velocity. This control leads to applications for electromagnetic pulse compression and electron/ion acceleration
Directory of Open Access Journals (Sweden)
Alireza Shooshtari
Full Text Available Abstract Free vibration of a magnetoelectroelastic rectangular plate is investigated based on the Reddy's third-order shear deformation theory. The plate rests on an elastic foundation and it is considered to have different boundary conditions. Gauss's laws for electrostatics and magnetostatics are used to model the electric and magnetic behavior. The partial differential equations of motion are reduced to a single partial differential equation and then by using the Galerkin method, the ordinary differential equation of motion as well as an analytical relation for the natural frequency of the plate is obtained. Some numerical examples are presented to validate the proposed model and to investigate the effects of several parameters on the vibration frequency of the considered smart plate.
Slender Ca ii H Fibrils Mapping Magnetic Fields in the Low Solar Chromosphere
Energy Technology Data Exchange (ETDEWEB)
Jafarzadeh, S.; Rutten, R. J.; Szydlarski, M. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Solanki, S. K.; Wiegelmann, T.; Riethmüller, T. L.; Noort, M. van; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Iniesta, J. C. del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain); Knölker, M. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Schmidt, W., E-mail: shahin.jafarzadeh@astro.uio.no [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany)
2017-04-01
A dense forest of slender bright fibrils near a small solar active region is seen in high-quality narrowband Ca ii H images from the SuFI instrument onboard the Sunrise balloon-borne solar observatory. The orientation of these slender Ca ii H fibrils (SCF) overlaps with the magnetic field configuration in the low solar chromosphere derived by magnetostatic extrapolation of the photospheric field observed with Sunrise/IMaX and SDO/HMI. In addition, many observed SCFs are qualitatively aligned with small-scale loops computed from a novel inversion approach based on best-fit numerical MHD simulation. Such loops are organized in canopy-like arches over quiet areas that differ in height depending on the field strength near their roots.
Continuous development of current sheets near and away from magnetic nulls
International Nuclear Information System (INIS)
Kumar, Sanjay; Bhattacharyya, R.
2016-01-01
The presented computations compare the strength of current sheets which develop near and away from the magnetic nulls. To ensure the spontaneous generation of current sheets, the computations are performed congruently with Parker's magnetostatic theorem. The simulations evince current sheets near two dimensional and three dimensional magnetic nulls as well as away from them. An important finding of this work is in the demonstration of comparative scaling of peak current density with numerical resolution, for these different types of current sheets. The results document current sheets near two dimensional magnetic nulls to have larger strength while exhibiting a stronger scaling than the current sheets close to three dimensional magnetic nulls or away from any magnetic null. The comparative scaling points to a scenario where the magnetic topology near a developing current sheet is important for energetics of the subsequent reconnection.
Spin-orbit torque induced magnetic vortex polarity reversal utilizing spin-Hall effect
Li, Cheng; Cai, Li; Liu, Baojun; Yang, Xiaokuo; Cui, Huanqing; Wang, Sen; Wei, Bo
2018-05-01
We propose an effective magnetic vortex polarity reversal scheme that makes use of spin-orbit torque introduced by spin-Hall effect in heavy-metal/ferromagnet multilayers structure, which can result in subnanosecond polarity reversal without endangering the structural stability. Micromagnetic simulations are performed to investigate the spin-Hall effect driven dynamics evolution of magnetic vortex. The mechanism of magnetic vortex polarity reversal is uncovered by a quantitative analysis of exchange energy density, magnetostatic energy density, and their total energy density. The simulation results indicate that the magnetic vortex polarity is reversed through the nucleation-annihilation process of topological vortex-antivortex pair. This scheme is an attractive option for ultra-fast magnetic vortex polarity reversal, which can be used as the guidelines for the choice of polarity reversal scheme in vortex-based random access memory.
International Nuclear Information System (INIS)
Bertrand, P.
1993-01-01
The new LIONS code (Lancement d'IONS or Ion Launching), a dynamical code implemented in the SPIRaL project for the CIME cyclotron studies, is presented. The various software involves a 3D magnetostatic code, 2D or 3D electrostatic codes for generation of realistic field maps, and several dynamical codes for studying the behaviour of the reference particle from the cyclotron center up to the ejection and for launching particles packets complying with given correlations. Its interactions with the other codes are described. The LIONS code, written in Fortran 90 is already used in studying the CIME cyclotron, from the center to the ejection. It is designed to be used, with minor modifications, in other contexts such as for the simulation of mass spectrometer facilities
RAY: a ray tracing program in cold magnetized plasma
International Nuclear Information System (INIS)
Montes, A.; Souza, L.H.
1985-01-01
This report deals with the development of a ray tracing program, that is, the plot of an electromagnetic wave path in a cold magnetized plasma medium. The program was developed based on the validity of the geometrical optics laws to calculate the electromagnetic wave trajectory. This approximation is valid when the wave length is much smaller than the characteristic length of the medium. No hypothesis was made about a particular geometric configuration for the magnetic field, what enables the use of the program in any magnetic confinment scheme. The numerically obtained results were compared with an analytic solution for a particular case (cylindrically symmetric medium, uniform magnetostatic, field along the symmetry axis and ordinary wave) and have shown a satisfactory precision. (Author) [pt
The stability of a constricted gas discharge
Energy Technology Data Exchange (ETDEWEB)
Tayler, R J [U.K. Atomic Energy Authority, AERE, Harwell (United Kingdom)
1958-07-01
This paper is to be regarded as a progress report on an unfinished problem and an indication is given of aspects of the problem which, it is hoped, will be studied soon. Two theoretical models are considered here. The first approach is extremely naive: plasma dynamics is completely neglected and only the forces exerted by the electromagnetic field are considered. The second approach is to use Maxwell's equations combined with a simple one-fluid hydrodynamics - classical hydromagnetics. The paper is arranged as follows: the magnetostatic or extensible wire model of the discharge is studied; based on the hydromagnetic equations: 1) the gradual loss of stability of the stabilised pinch, due to field diffusion, is discussed and 2) another type of stable discharge configuration is introduced. In the final section there is a discussion of further problems which must be studied.
Closed and open magnetic fields in stellar winds
Mullan, D. J.; Steinolfson, R. S.
1983-01-01
A numerical study of the interaction between a thermal wind and a global dipole field in the sun and in a giant star is reported. In order for closed field lines to persist near the equator (where a helmet-streamer-like configuration appears), the coronal temperature must be less than a critical value Tc, which scales as M/R. This condition is found to be equivalent to the following: for a static helmet streamer to persist, the sonic point above the helmet must not approach closer to the star than 2.2-2.6 stellar radii. Implications for rapid mass loss and X-ray emission from cool giants are pointed out. The results strengthen the case for identifying empirical dividing lines in the H-R diagram with a magnetic topology transition locus (MTTL). Support for the MTTL concept is also provided by considerations of the breakdown of magnetostatic equilibrium.
Voltage control of cavity magnon polariton
Energy Technology Data Exchange (ETDEWEB)
Kaur, S., E-mail: kaurs3@myumanitoba.ca; Rao, J. W.; Gui, Y. S.; Hu, C.-M., E-mail: hu@physics.umanitoba.ca [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Yao, B. M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); National Laboratory for Infrared Physics, Chinese Academy of Sciences, Shanghai 200083 (China)
2016-07-18
We have experimentally investigated the microwave transmission of the cavity-magnon-polariton (CMP) generated by integrating a low damping magnetic insulator onto a 2D microwave cavity. The high tunability of our planar cavity allows the cavity resonance frequency to be precisely controlled using a DC voltage. By appropriately tuning the voltage and magnetic bias, we can observe the cavity photon magnon coupling and the magnetic coupling between a magnetostatic mode and the generated CMP. The dispersion of the generated CMP was measured by either tuning the magnetic field or the applied voltage. This electrical control of CMP may open up avenues for designing advanced on-chip microwave devices that utilize light-matter interaction.
Improved propagation margin in YIG coated LPE garnet films for bubble devices
International Nuclear Information System (INIS)
Hidaka, Y.; Yoshimi, K.; Hibiya, T.; Mikami, M.
1975-01-01
YIG thin layers grown on (Y,Eu,Yb) 3 (Fe,Ga) 5 O 12 LPE films were found to be very effective for improvement of bubble propagation margin as well as for hard bubble suppression. In the ion-implanted rare earth substituted Ga:YIG on (111) GGG with 8 micron bubble, T-bar propagation margin was diminished, because of stretching or oscillating of bubble along the patterns. A 600 A YIG thin layer with in-plane magnetization, grown by CVD at 1065 0 C, obviated these destructive shortcomings and guaranteed the minimum driving field for stable bubble propagation down to 10 Oe. This improvement can be attributed to the magnetostatic interaction between the YIG layer and the bubble supporting layer. (auth)
Domain walls and exchange-interaction in Permalloy/Gd films
International Nuclear Information System (INIS)
Ranchal, R; Aroca, C; Lopez, E
2008-01-01
In this work we study the exchange coupling in Permalloy (Py)/gadolinium (Gd) bilayers. The exchange-coupled Py/Gd system is very temperature dependent and moreover the magnetization process in the Py layer is mainly due to domain wall (DW) displacements which are strongly controlled by pinning effects. We propose that this pinning could be caused by magnetostatic and exchange interactions between Py DWs and the magnetostrictive Gd layer. These effects mask the antiferromagnetic coupling between layers and, depending on temperature and Py thicknesses, apparent ferromagnetic coupling occurs. The study has been performed in the 80-300 K temperature range for different Py layer thicknesses and different Py induced anisotropies
Curious behavior of optically trapped neutral atoms
International Nuclear Information System (INIS)
Wieman, C.; Walker, T.; Sesko, D.; Monroe, C.
1991-01-01
We have studied the behavior of clouds of neutral atoms contained in a spontaneous force optical trap. Because of the low temperatures of the atoms ( 5 atoms. These include the expansion of the cloud as the number is increased and dramatic changes in the distribution of the atoms at higher numbers. We can explain much of the collective behavior using a simple model that includes a 1/r 2 force between the atoms arising from the multiple scattering of photons. Finally, we discuss the optical trapping of atoms directly from a low pressure vapor in a small glass cell. We have used these optically trapped atoms to load a magnetostatic trap in the same cell. This provided a high density sample of atoms with a temperature of less than 2 μK
Energy Technology Data Exchange (ETDEWEB)
Herrmannsfeldt, W.B.
1979-11-01
The SLAC Electron Trajectory Program is described and instructions and examples for users are given. The program is specifically written to compute trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes. Either rectangular or cylindrically symmetric geometry may be used. Magntic fields may be specified using arbitrary configurations of coils, or the output of a magnet program such as Poisson or by an externally calculated array of the axial fields. The program is available in IBM FORTRAN but can be easily converted for use on other brands of hardware. The program is intended to be used with a plotter whose interface the user must provide.
A magnetic nano-particle ink for tunable microwave applications
Ghaffar, Farhan A.
2016-12-19
Inkjet printing or printing for realization of inexpensive and large area electronics has unearthed as an attractive fabrication technique. Though at present, mostly the metallic inks are printed on regular microwave substrates. In this paper, a fully printed multilayer fabrication process is demonstrated where the substrate is also realized through printing. A novel Fe2O3 based magnetic ink is used as a substrate while an in-house silver organo complex (SOC) ink is developed for metallic layers. Complete magnetostatic and microwave characterization of the ink is presented. At the end, a tunable patch antenna is shown as an application using the magnetic ink as the substrate. The antenna shows a tuning range of 12.5 % for a magnetic field strength of 3 kOe.
Pauletta, S; Todesco, Ezio
2002-01-01
In superconducting accelerator magnets, the field quality is mainly determined by conductor position inside the coil. For the LHC, the dipolar field homogeneity must be assured up to 10-5 of the main field component, imposing strict manufacturing tolerances. Magnetic measurements at room temperature provide a fast and economical way to find out assembly errors or the use of faulty components. In order to compute control bounds for the industrial series production, the magnetic measurements performed at room temperature on 27 pre-series collared coils have been statistically analyzed in this work. An automatic tool has been implemented to single out anomalous values of the magnetic field in the measurements. Such cases have been analyzed using a magnetostatic code to work out errors in the manufacturing process and the possible cures.
A fully printed ferrite nano-particle ink based tunable antenna
Ghaffar, Farhan A.
2016-11-02
Inkjet printing or printing in general has emerged as a very attractive method for the fabrication of low cost and large size electronic systems. However, most of the printed designs rely on nano-particle based metallic inks which are printed on conventional microwave substrates. In order to have a fully printed fabrication process, the substrate also need to be printed. In this paper, a fully printed multi-layer process utilizing custom Fe2O3 based magnetic ink and a silver organic complex (SOC) ink is demonstrated for tunable antennas applications. The ink has been characterized for high frequency and magnetostatic properties. Finally as a proof of concept, a microstrip patch antenna is realized using the proposed fabrication technique which shows a tuning range of 12.5 %.
Kordbacheh, A.; Ghahremaninezhad, Roghayeh; Maraghechi, B.
2012-09-01
A three-dimensional analysis of a novel free-electron laser (FEL) based upon a rectangular hybrid wiggler (RHW) is presented. This RHW is designed in a configuration composed of rectangular rings with alternating ferrite and dielectric spacers immersed in a solenoidal magnetic field. An analytic model of RHW is introduced by solution of Laplace's equation for the magnetostatic fields under the appropriate boundary conditions. The single-electron orbits in combined RHW and axial guide magnetic fields are studied when only the first and the third spatial harmonic components of the RHW field are taken into account and the higher order terms are ignored. The results indicate that the third spatial harmonic leads to group III orbits with a strong negative mass regime particularly in large solenoidal magnetic fields. RHW is found to be a promising candidate with favorable characteristics to be used in microwave FEL.
Muniz, Sérgio R.; Bagnato, Vanderlei S.; Bhattacharya, M.
2015-06-01
In a region free of currents, magnetostatics can be described by the Laplace equation of a scalar magnetic potential, and one can apply the same methods commonly used in electrostatics. Here, we show how to calculate the general vector field inside a real (finite) solenoid, using only the magnitude of the field along the symmetry axis. Our method does not require integration or knowledge of the current distribution and is presented through practical examples, including a nonuniform finite solenoid used to produce cold atomic beams via laser cooling. These examples allow educators to discuss the nontrivial calculation of fields off-axis using concepts familiar to most students, while offering the opportunity to introduce themes of current modern research.
Soft thermal contributions to 3-loop gauge coupling
Laine, M.; Schicho, P.; Schröder, Y.
2018-05-01
We analyze 3-loop contributions to the gauge coupling felt by ultrasoft ("magnetostatic") modes in hot Yang-Mills theory. So-called soft/hard terms, originating from dimension-six operators within the soft effective theory, are shown to cancel 1097/1098 of the IR divergence found in a recent determination of the hard 3-loop contribution to the soft gauge coupling. The remaining 1/1098 originates from ultrasoft/hard contributions, induced by dimension-six operators in the ultrasoft effective theory. Soft 3-loop contributions are likewise computed, and are found to be IR divergent, rendering the ultrasoft gauge coupling non-perturbative at relative order O({α}s^{3/2}) . We elaborate on the implications of these findings for effective theory studies of physical observables in thermal QCD.
Directory of Open Access Journals (Sweden)
Boughrara Kamel
2009-01-01
Full Text Available This paper deals with the analytical and numerical analysis of the flux density distribution in the slotted air gap of permanent magnet motors with surface mounted tangentially magnetized permanent magnets. Two methods for magnetostatic field calculations are developed. The first one is an analytical method in which the effect of stator slots is taken into account by modulating the magnetic field distribution by the complex relative air gap permeance. The second one is a numerical method using 2-D finite element analysis with consideration of Dirichlet and anti-periodicity (periodicity boundary conditions and Lagrange Multipliers for simulation of movement. The results obtained by the analytical method are compared to the results of finite-element analysis.
Geoffroy, Olivier; Boust, Nicolas; Chazal, Hervé; Flury, Sébastien; Roudet, James
2018-04-01
This article focuses on the modeling of the hysteresis loop featured by Fe-Cu-Nb-Si-B nanocrystalline alloys with transverse induced anisotropy. The magnetization reversal process of a magnetic correlated volume (CV), characterized by the induced anisotropy Ku, and a deviation of the local easy magnetization direction featuring the effect of a local incoherent anisotropy Ki, is analyzed, taking account of magnetostatic interactions. Solving the equations shows that considering a unique typical kind of CV does not enable accounting for both the domain pattern and the coercivity. Actually, the classical majority CVs obeying the random anisotropy model explains well the domain pattern but considering another kind of CVs, minority, mingled with classical ones, featuring a magnitude of Ki comparable to Ku, is necessary to account for coercivity. The model has been successfully compared with experimental data.
Experimental development of a millimeter wave free electron laser
International Nuclear Information System (INIS)
Radack, D.J.; Bidwell, S.W.; Antonsen, T.M. Jr.; Carmel, Y.; Destler, W.W.; Granatstein, V.L.; Latham, P.E.; Levush, B.; Mayergoyz, I.D.; Rodgers, J.; Zhang, Z.X.
1990-01-01
A 1 MW (cw), millimeter wave FEL (λ 3 ∼ 0.5 mm)is currently under development with an application for heating fusion plasmas. Two salient features of the FEL are the use of a short-period wiggler ell w ≤ 10 mm electromagnet and a mildly relativistic (E beam ≤ 1 MeV) sheet electron beam. The FEL has been designed to operate in the high-gain regime and uses a tapered wiggler. The wiggler provides beam focusing as well as the magnetostatic pump wave. The effectiveness of wiggler focusing is being investigated. Planned experiments will address the critical issues of beam interception and stable single-mode operation. 12 refs., 1 tab
International Nuclear Information System (INIS)
Ibrahim, R.S.
2003-01-01
The equations of magnetohydrodynamic (MHD) equilibria for a plasma in gravitational field are investigated. For equilibria with one ignorable spatial coordinate, the MHD equations are reduced to a single nonlinear elliptic equation for the magnetic potential u-tilde, known as the Grad-Shafranov equation. Specifying the arbitrary functions in this equation, the Bullough-Dodd equation can be obtained. The truncated Painleve expansion and reduction of the partial differential equation to a quadrature problem (RQ method) are described and applied to obtain the travelling wave solutions of the Bullough-Dodd equation for the case of isothermal magnetostatic atmosphere, in which the current density J is proportional to the exponentially of the magnetic flux and moreover falls off exponentially with distance vertical to the base, with an 'e-folding' distance equal to the gravitational scale height
Passive force balancing of an active magnetic regenerative liquefier
Teyber, R.; Meinhardt, K.; Thomsen, E.; Polikarpov, E.; Cui, J.; Rowe, A.; Holladay, J.; Barclay, J.
2018-04-01
Active magnetic regenerators (AMR) have the potential for high efficiency cryogen liquefaction. One active magnetic regenerative liquefier (AMRL) configuration consists of dual magnetocaloric regenerators that reciprocate in a persistent-mode superconducting solenoid. Issues with this configuration are the spatial and temporal magnetization gradients that induce large magnetic forces and winding currents. To solve the coupled problem, we present a force minimization approach using passive magnetic material to balance a dual-regenerator AMR. A magnetostatic model is developed and simulated force waveforms are compared with experimental measurements. A genetic algorithm identifies force-minimizing passive structures with virtually ideal balancing characteristics. Implementation details are investigated which affirm the potential of the proposed methodology.
Correlation between physical structure and magnetic anisotropy of a magnetic nanoparticle colloid
Dennis, C. L.; Jackson, A. J.; Borchers, J. A.; Gruettner, C.; Ivkov, R.
2018-05-01
We show the effects of a time-invariant magnetic field on the physical structure and magnetic properties of a colloid comprising 44 nm diameter magnetite magnetic nanoparticles, with a 24 nm dextran shell, in water. Structural ordering in this colloid parallel to the magnetic field occurs simultaneously with the onset of a colloidal uniaxial anisotropy. Further increases in the applied magnetic field cause the nanoparticles to order perpendicular to the field, producing unexpected colloidal unidirectional and trigonal anisotropies. This magnetic behavior is distinct from the cubic magnetocrystalline anisotropy of the magnetite and has its origins in the magnetic interactions among the mobile nanoparticles within the colloid. Specifically, these field-induced anisotropies and colloidal rearrangements result from the delicate balance between the magnetostatic and steric forces between magnetic nanoparticles. These magnetic and structural rearrangements are anticipated to influence applications that rely upon time-dependent relaxation of the magnetic colloids and fluid viscosity, such as magnetic hyperthermia and shock absorption.
Thermal stability of bubble domains in ferromagnetic discs
International Nuclear Information System (INIS)
Hrkac, G; Bance, S; Goncharov, A; Schrefl, T; Suess, D
2007-01-01
The transition and thermal stability of disc-shaped ferromagnetic particles at the temperature of T = 300 K with a uniaxial anisotropy along the symmetry axis from a bi-domain to a single domain state has been studied. The nudge elastic band method was used to map the energy landscape and to calculate the energy barrier between the transition states. For single FePt disc-shaped particles with perpendicular anisotropy three transition configurations have been found: single domain, stripe- and stable bubble domains at zero applied field. The single domain configuration along the positive anisotropy axis is reached by an annihilation process of the domain wall and the all-down state by a complex domain expansion process. Magnetization configurations in two interacting discs show an increase in thermal stability compared with single disc systems, which is attributed to the interacting magnetostatic energy between the two particles
International Nuclear Information System (INIS)
Hasegawa, R.; Koon, N.C.; Cooper, B.R.
1984-01-01
Various topics on magnetism and magnetic materials are addressed. The subjects considered include: spin glasses, amorphous magnetism, actinide and rare earth intermetallics, magnetic excitation, itinerant magnetism and magnetic structure, valence instabilities, Kondo effect, transport and Hall effects, mixed valence and Kondo compounds, superconductivity and magnetism, d and f electron magnetism and superconductivity, Fe-based microcrystalline and permanent magnetic alloys, hard and soft magnetic materials, and magnetooptics. Also discussed are: numerical methods for magnetic field computation, recording theory and experiments, recording heads and media, magnetic studies via hyperfine interactions, magnetic semiconductors, magnet insulators, transition metal systems, random fields, critical phenomena and magnetoelastic effects and resonance, surfaces and interfaces, magnetostatic waves and resonance, bubble materials and implantation, bubble devices and physics, magnetic separation, ferrofluids, magnetochemistry, new techniques and materials, and new applications
High intensity positron program at LLNL
International Nuclear Information System (INIS)
Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.
1999-01-01
Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy
High intensity positron program at LLNL
International Nuclear Information System (INIS)
Asoka-Kumar, P.; Howell, R.H.; Stoeffl, W.
1998-01-01
Lawrence Livermore National Laboratory (LLNL) is the home of the world's highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectra
Ferrite LTCC-based antennas for tunable SoP applications
Shamim, Atif
2011-07-01
For the first time, ferrite low temperature co-fired ceramic (LTCC) tunable antennas are presented. These antennas are frequency tuned by a variable magnetostatic field produced in a winding that is completely embedded inside the ferrite LTCC substrate. Embedded windings have reduced the typically required magnetic bias field for antenna tuning by over 95%. The fact that large electromagnets are not required for tuning makes ferrite LTCC with embedded bias windings an ideal platform for advanced tunable system-on-package applications. Measurements of rectangular microstrip patch antennas on a ferrite LTCC substrate display a maximum tuning range of 610 MHz near 12 GHz. Two different bias windings and their effect on the antenna performance are discussed, as is the effect of antenna orientation with respect to the bias winding. The antenna radiation patterns are measured under biased and unbiased conditions, showing a stable co-polarized linear gain. © 2011-2012 IEEE.
Zangwill, Andrew
2013-01-01
An engaging writing style and a strong focus on the physics make this comprehensive, graduate-level textbook unique among existing classical electromagnetism textbooks. Charged particles in vacuum and the electrodynamics of continuous media are given equal attention in discussions of electrostatics, magnetostatics, quasistatics, conservation laws, wave propagation, radiation, scattering, special relativity and field theory. Extensive use of qualitative arguments similar to those used by working physicists makes Modern Electrodynamics a must-have for every student of this subject. In 24 chapters, the textbook covers many more topics than can be presented in a typical two-semester course, making it easy for instructors to tailor courses to their specific needs. Close to 120 worked examples and 80 applications boxes help the reader build physical intuition and develop technical skill. Nearly 600 end-of-chapter homework problems encourage students to engage actively with the material. A solutions manual is availa...
Self-generation of dissipative solitons in magnonic quasicrystal active ring resonator
Energy Technology Data Exchange (ETDEWEB)
Grishin, S. V., E-mail: grishfam@sgu.ru; Beginin, E. N.; Morozova, M. A.; Sharaevskii, Yu. P. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Nikitov, S. A. [Laboratory “Metamaterials,” Saratov State University, Saratov 410012 (Russian Federation); Kotel' nikov Institute of Radioengineering and Electronics, Russian Academy of Science, Moscow 125009 (Russian Federation)
2014-02-07
Self-generation of dissipative solitons in the magnonic quasicrystal (MQC) active ring resonator is studied theoretically and experimentally. The developed magnonic crystal has quasiperiodic Fibonacci type structure. Frequency selectivity of the MQC together with the parametric three-wave decay of magnetostatic surface spin wave (MSSW) leads to the dissipative soliton self-generation. The transfer matrix method is used to describe MQC transmission responses. Besides, the model of MQC active ring resonator is suggested. The model includes three coupled differential equations describing the parametric decay of MSSW and two differential equations of linear oscillators describing the frequency selectivity of MQC. Numerical simulation results of dissipative soliton self-generation are in a fair agreement with experimental data.
Individual magnetization reversal of a square dot matrix by common current excitation
International Nuclear Information System (INIS)
Elyasi, Mehrdad; Bhatia, Charanjit S; Yang, Hyunsoo
2015-01-01
We have proposed a method for magnetization reversal of individual sites of a 2 by 2 matrix of perpendicularly magnetized dots by common current excitation. The spin-polarized current signal consists of a dc-biased ac part followed by a pure dc one. The amplitude of the dc and ac parts of the current, as well as the phase and duration of the ac current, determine the reversal sites through the magnetostatic interaction among the dots. We show that the individual selectivity in magnetization reversal occurs through two consecutive steps, dephasing of the matrix dyadic pairs dynamics followed by nonlinear dephasing of the individual elements. This method can be utilized to increase the storage density of magnetic random access memory by enabling common access for four or more bits. (paper)
International Nuclear Information System (INIS)
Ress, R.I.
1976-01-01
Charged particles are entrained in a predetermined direction, independent of their polarity, in a circular orbit by a magnetic field rotating at high speed about an axis in a closed cylindrical or toroidal vessel. The field may be generated by a cylindrical laser structure, whose beam is polygonally reflected from the walls of an excited cavity centered on the axis, or by high-frequency energization of a set of electromagnets perpendicular to the axis. In the latter case, a separate magnetostatic axial field limits the orbital radius of the particles. These rotating and stationary magnetic fields may be generated centrally or by individual magnets peripherally spaced along its circular orbit. Chemical or nuclear reactions can be induced by collisions between the orbiting particles and an injected reactant, or by diverting high-speed particles from one doughnut into the path of counterrotating particles in an adjoining doughnut
Energy Technology Data Exchange (ETDEWEB)
Peng, Y. [College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610066 (China); College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China); Zhao, G.P., E-mail: zhaogp@uestc.edu.cn [College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610066 (China); Morvan, F.J.; Wu, S.Q. [College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610066 (China); Yue, M. [College of Materials Science and Engineering, Beijing University of Technology, Beijing 100124 (China)
2017-01-15
Due to its potential applications in high-density magnetic storage and spin electronic devices, the ferromagnetic resonance absorption phenomenon has recently drawn much attention. By studying the influence of different materials with various shapes on this phenomenon, the new understandings gained could lead to other applications in the future. In this paper, dynamic magnetic susceptibilities of the vortex state in permalloy nanodot arrays have been investigated using a three-dimensional object oriented micromagnetic framework (OOMMF) code with a two-dimensional periodic boundary condition (2D-PBC) extension and compared with those of a single dot carefully. The resonance mode is excited in the vortex state of nanodot arrays by the microwave magnetic field perpendicular to the dot plane. In this case only radially symmetric spin wave modes can be excited. The influence of the geometric parameters on the resonance frequency has been studied systemically, including the dot radius, the number of repeating elements, and the dot distance. One can see that the resonance peak of the dot array is higher than that of a single dot because of the induced stronger magnetostatic coupling. A critical dot distance exists at which the dot array may be treated as a single dot. There is only one resonance peak for both the dot array and the single dot, as the radius changes. - Highlights: • Resonance peak of the dot array is higher than that of a single dot because of the induced stronger magnetostatic coupling. • A critical dot distance exists at which the dot array may be treated as a single dot. • There is only one resonance peak for both the dot array and the single dot, as the radius changes.
The Lifetimes and Evolution of Molecular Cloud Cores
Vázquez-Semadeni, Enrique; Kim, Jongsoo; Shadmehri, Mohsen; Ballesteros-Paredes, Javier
2005-01-01
We discuss the lifetimes and evolution of clumps and cores formed as turbulent density fluctuations in nearly isothermal molecular clouds. In order to maintain a broad perspective, we consider both the magnetic and nonmagnetic cases. In the latter, we argue that clumps are unlikely to reach a hydrostatic state if molecular clouds can in general be described as single-phase media with an effective polytropic exponent γecriticality of their ``parent clouds'' (the numerical boxes). In subcritical boxes, magnetostatic clumps do not form. A minority of moderately gravitationally bound clumps form, which however are dispersed by the turbulence in ~1.3 Myr, suggesting that these few longer lived cores can marginally be ``captured'' by AD to increase their mass-to-flux ratio and eventually collapse, although on timescales not significantly longer than the dynamical ones. In supercritical boxes, some cores manage to become locally supercritical and collapse in typical timescales of 2 tfc (~1 Myr). In the most supercritical simulation, a few longer lived cores are observed, which last for up to ~3 Myr, but these end up re-expanding rather than collapsing, because they are sub-Jeans in spite of being supercritical. Fewer clumps and cores form in these simulations than in their nonmagnetic counterpart. Our results suggest the following: (1) not all cores observed in molecular clouds will necessarily form stars and that a class of ``failed cores'' should exist, which will eventually redisperse and which may be related to the observed starless cores; (2) cores may be out-of-equilibrium, transient structures, rather than quasi-magnetostatic configurations; (3) the magnetic field may help reduce the star formation efficiency by reducing the probability of core formation, rather than by significantly delaying the collapse of individual cores, even in magnetically supercritical clouds.
PARTICLE SCATTERING OFF OF RIGHT-HANDED DISPERSIVE WAVES
Energy Technology Data Exchange (ETDEWEB)
Schreiner, C.; Kilian, P.; Spanier, F., E-mail: cschreiner@astro.uni-wuerzburg.de [Centre for Space Research, North-West University, 2520 Potchefstroom (South Africa)
2017-01-10
Resonant scattering of fast particles off low frequency plasma waves is a major process determining transport characteristics of energetic particles in the heliosphere and contributing to their acceleration. Usually, only Alfvén waves are considered for this process, although dispersive waves are also present throughout the heliosphere. We investigate resonant interaction of energetic electrons with dispersive, right-handed waves. For the interaction of particles and a single wave a variable transformation into the rest frame of the wave can be performed. Here, well-established analytic models derived in the framework of magnetostatic quasi-linear theory can be used as a reference to validate simulation results. However, this approach fails as soon as several dispersive waves are involved. Based on analytic solutions modeling the scattering amplitude in the magnetostatic limit, we present an approach to modify these equations for use in the plasma frame. Thereby we aim at a description of particle scattering in the presence of several waves. A particle-in-cell code is employed to study wave–particle scattering on a micro-physically correct level and to test the modified model equations. We investigate the interactions of electrons at different energies (from 1 keV to 1 MeV) and right-handed waves with various amplitudes. Differences between model and simulation arise in the case of high amplitudes or several waves. Analyzing the trajectories of single particles we find no microscopic diffusion in the case of a single plasma wave, although a broadening of the particle distribution can be observed.
International Nuclear Information System (INIS)
Peng, Y.; Zhao, G.P.; Morvan, F.J.; Wu, S.Q.; Yue, M.
2017-01-01
Due to its potential applications in high-density magnetic storage and spin electronic devices, the ferromagnetic resonance absorption phenomenon has recently drawn much attention. By studying the influence of different materials with various shapes on this phenomenon, the new understandings gained could lead to other applications in the future. In this paper, dynamic magnetic susceptibilities of the vortex state in permalloy nanodot arrays have been investigated using a three-dimensional object oriented micromagnetic framework (OOMMF) code with a two-dimensional periodic boundary condition (2D-PBC) extension and compared with those of a single dot carefully. The resonance mode is excited in the vortex state of nanodot arrays by the microwave magnetic field perpendicular to the dot plane. In this case only radially symmetric spin wave modes can be excited. The influence of the geometric parameters on the resonance frequency has been studied systemically, including the dot radius, the number of repeating elements, and the dot distance. One can see that the resonance peak of the dot array is higher than that of a single dot because of the induced stronger magnetostatic coupling. A critical dot distance exists at which the dot array may be treated as a single dot. There is only one resonance peak for both the dot array and the single dot, as the radius changes. - Highlights: • Resonance peak of the dot array is higher than that of a single dot because of the induced stronger magnetostatic coupling. • A critical dot distance exists at which the dot array may be treated as a single dot. • There is only one resonance peak for both the dot array and the single dot, as the radius changes.
Computational Analysis of Static and Dynamic Behaviour of Magnetic Suspensions and Magnetic Bearings
Britcher, Colin P. (Editor); Groom, Nelson J.
1996-01-01
Static modelling of magnetic bearings is often carried out using magnetic circuit theory. This theory cannot easily include nonlinear effects such as magnetic saturation or the fringing of flux in air-gaps. Modern computational tools are able to accurately model complex magnetic bearing geometries, provided some care is exercised. In magnetic suspension applications, the magnetic fields are highly three-dimensional and require computational tools for the solution of most problems of interest. The dynamics of a magnetic bearing or magnetic suspension system can be strongly affected by eddy currents. Eddy currents are present whenever a time-varying magnetic flux penetrates a conducting medium. The direction of flow of the eddy current is such as to reduce the rate-of-change of flux. Analytic solutions for eddy currents are available for some simplified geometries, but complex geometries must be solved by computation. It is only in recent years that such computations have been considered truly practical. At NASA Langley Research Center, state-of-the-art finite-element computer codes, 'OPERA', 'TOSCA' and 'ELEKTRA' have recently been installed and applied to the magnetostatic and eddy current problems. This paper reviews results of theoretical analyses which suggest general forms of mathematical models for eddy currents, together with computational results. A simplified circuit-based eddy current model proposed appears to predict the observed trends in the case of large eddy current circuits in conducting non-magnetic material. A much more difficult case is seen to be that of eddy currents in magnetic material, or in non-magnetic material at higher frequencies, due to the lower skin depths. Even here, the dissipative behavior has been shown to yield at least somewhat to linear modelling. Magnetostatic and eddy current computations have been carried out relating to the Annular Suspension and Pointing System, a prototype for a space payload pointing and vibration
Schrödinger Theory of Electrons in Electromagnetic Fields: New Perspectives
Directory of Open Access Journals (Sweden)
Viraht Sahni
2017-03-01
dots in a magnetostatic field, one in a ground state and the other in an excited state. For the time-dependent case, the evolution of the same states of the quantum dots in both a magnetostatic and a time-dependent electric field is described. In each case, the satisfaction of the corresponding “Quantal Newtonian” law is demonstrated.
MAGNUS-3D: Accelerator magnet calculations in 3-dimensions
Pissanetzky, S.
1988-12-01
MAGNUS-3D is a professional finite element code for nonlinear magnetic engineering. MAGNUS-3D can solve numerically any general problem of linear or nonlinear magnetostatics in three dimensions. The problem is formulated in a domain with Dirichlet, Neumann or periodic boundary conditions, that can contain any combination of conductors of any shape in space, nonlinear magnetic materials with magnetic properties specified by magnetization tables, and nonlinear permanent magnets with any given demagnetization curve. MAGNUS-3D uses the two-scalar-potentials formulation of Magnetostatics and the finite element method, has an automatic 3D mesh generator, and advanced post-processing features that include graphics on a variety of supported devices, tabulation, and calculation of design quantities required in Magnetic Engineering. MAGNUS-3D is a general purpose 3D code, but it has been extensively used for accelerator work and many special features required for accelerator engineering have been incorporated into the code. One of such features is the calculation of field harmonic coefficients averaged in the direction of the beam, so important for the design of magnet ends. Another feature is its ability to calculate line integrals of any field component along the direction of the beam, or plot the field as a function of the z coordinate. MAGNUS-3D has found applications to the design of accelerator magnets and spectrometers, steering magnets, wigglers and undulators for free electron lasers, microtrons and magnets for synchrotron light sources, as well as magnets for NMR and medical applications, recording heads and various magnetic devices. There are three more programs closely associated with MAGNUS-3D. MAGNUS-GKS is the graphical postprocessor for the package; it supports a numer of output devices, including color vector or bit map devices. WIRE is an independent program that can calculate the field produced by any configuration of electric conductors in space, at any
International Nuclear Information System (INIS)
Chiolerio, Alessandro; Allia, Paolo; Graziano, Mariagrazia
2012-01-01
Physical limitations foreshadow the eventual end to traditional Complementary Metal Oxide Semiconductor (CMOS) scaling. Therefore, interest has turned to various materials and technologies aimed to succeed to traditional CMOS. Magnetic Quantum dot Cellular Automata (MQCA) are one of these technologies. Working MQCA arrays require very complex techniques and an excellent control on the geometry of the nanomagnets and on the quality of the magnetic thin film, thus limiting the possibility for MQCA of representing a definite solution to cost-effective, high density and low power consumption device demand. Counter-intuitively, moving towards bigger sizes and lighter technologies it is still possible to develop multi-state logic devices, as we demonstrated, whose main advantage is cost-effectiveness. Applications may be seen in low cost logic devices where integration and computational power are not the main issue, eventually using flexible substrates and taking advantage of the intrinsic mechanical toughness of systems where long range interactions do not need wirings. We realized cobalt micrometric MQCA arrays by means of Electron Beam Lithography, exploiting cost-effective processes such as lift-off and RF sputtering that usually are avoided due to their low control on array geometry and film roughness. Information relative to the magnetic configuration of MQCA elements including their eventual magnetic interactions was obtained from Magnetic Force Microscope (MFM) images, enhanced by means of a numerical procedure and presented in differential maps. We report the existence of bi-stable magnetic patterns, as detected by MFM while sampling the z-component of magnetic induction field, arising from dipolar inter-element magnetostatic coupling, able to store and propagate binary information. This is achieved despite the array quality and element magnetic state, which are low and multi-domain, respectively. We discuss in detail shape, inter-element spacing and dot profile
Control of propagation characteristics of spin wave pulses via elastic and thermal effects
Energy Technology Data Exchange (ETDEWEB)
Gómez-Arista, Ivan [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Kolokoltsev, O., E-mail: oleg.kolokoltsev@ccadet.unam.mx [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Acevedo, A.; Qureshi, N. [Centro de Ciencias Aplicadas y Desarrollo Tecnológico, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico); Ordóñez-Romero, César L. [Instituto de Física, Universidad Nacional Autónoma de México, CU, 04510 D.F., México (Mexico)
2017-05-01
A study of the magnetoelastic (ME) and thermal effects governing the phase (φ) and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides is presented. The ME effects were studied in a flexural configuration, under punctual mechanical force (F). Thermally induced ME and demagnetization phenomena were controlled by optically injected thermal power P{sub th}. It was determined that in an unclamped Ga:YIG waveguide, the force F that induces the phase shift Δφ=π, decreases by a quadratic law in the range from 1 mN to nN, and the P{sub th} at which Δφ=π decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. For nano-volume waveguides the ME control energy (E{sub me}) can be of order of aJ, and the thermal control energy (ΔE{sub th}) can be as small as 50 fJ. The response time of these effects lies in the ns time scale. Both the mechanical and the thermo-magnetic forces provide an effective control of MSSW pulse amplitude, in addition to its phase shift. The thermo-magnetic effect allows one to realize variable delays of a MSSW pulse. - Highlights: • The Magneto-elastic (ME) and optically induced thermal effects governing the phase and amplitude of magnetostatic surface spin wave (MSSW) pulses propagating in Ga:YIG/GGG and permalloy magnonic waveguides are presented. • A mechanical force that causes phase shift Δφ=π for spin waves in the waveguides decreases by a quadratic law in the range from 1 mN to nN, and the optical power that induces the phase shift Δφ=π, decreases linearly from mW to μW as the waveguide volume decreases from mm{sup 3} to nm{sup 3}. • The response time of these effects can lie in the ns time scale.
Development and analysis of finite volume methods
International Nuclear Information System (INIS)
Omnes, P.
2010-05-01
This document is a synthesis of a set of works concerning the development and the analysis of finite volume methods used for the numerical approximation of partial differential equations (PDEs) stemming from physics. In the first part, the document deals with co-localized Godunov type schemes for the Maxwell and wave equations, with a study on the loss of precision of this scheme at low Mach number. In the second part, discrete differential operators are built on fairly general, in particular very distorted or nonconforming, bidimensional meshes. These operators are used to approach the solutions of PDEs modelling diffusion, electro and magneto-statics and electromagnetism by the discrete duality finite volume method (DDFV) on staggered meshes. The third part presents the numerical analysis and some a priori as well as a posteriori error estimations for the discretization of the Laplace equation by the DDFV scheme. The last part is devoted to the order of convergence in the L2 norm of the finite volume approximation of the solution of the Laplace equation in one dimension and on meshes with orthogonality properties in two dimensions. Necessary and sufficient conditions, relatively to the mesh geometry and to the regularity of the data, are provided that ensure the second-order convergence of the method. (author)
Determination of ICRF antenna fields in the vicinity of a 3-D Faraday shield structure
Energy Technology Data Exchange (ETDEWEB)
Ryan, P M; Rothe, K E; Whealton, J H; Shepard, T D [Oak Ridge National Lab., TN (USA)
1990-04-01
A three-dimensional (3-D) magnetostatic analysis developed at Oak Ridge National Laboratory has been used to calculate the electromagnetic transmission properties of representative Faraday shield designs. The analysis uses the long-wavelength approximation to obtain a 3-D Laplace solution for the magnetic scalar potential over one poloidal period of the Faraday shield, from which the complete magnetic field distribution may be obtained. Once the magnetic field distributions in the presence and absence of a Faraday shield are known, the flux transmission coefficient can be found, as well as any change in the distributed inductance of the current strap. The distrbuted capacitance of the strap can be found from an analogous 3-D electrostatic calculation, enabling the phase velocity of the slow-wave structure to be determined. Power dissipation in the shield may be estimated by equating the surface current on a perfect conductor with the surface magnetic field and using this surface current in conjunction with the finite conductivities of the shield materials to obtain the power distribution due to eddy current heating. (orig.).
International Nuclear Information System (INIS)
Vaz, C A F; Hayward, T J; Llandro, J; Schackert, F; Morecroft, D; Bland, J A C; Klaeui, M; Laufenberg, M; Backes, D; Ruediger, U; Castano, F J; Ross, C A; Heyderman, L J; Nolting, F; Locatelli, A; Faini, G; Cherifi, S; Wernsdorfer, W
2007-01-01
Ferromagnetic metal rings of nanometre range widths and thicknesses exhibit fundamentally new spin states, switching behaviour and spin dynamics, which can be precisely controlled via geometry, material composition and applied field. Following the discovery of the 'onion state', which mediates the switching to and between vortex states, a range of fascinating phenomena has been found in these structures. In this overview of our work on ring elements, we first show how the geometric parameters of ring elements determine the exact equilibrium spin configuration of the domain walls of rings in the onion state, and we show how such behaviour can be understood as the result of the competition between the exchange and magnetostatic energy terms. Electron transport provides an extremely sensitive probe of the presence, spatial location and motion of domain walls, which determine the magnetic state in individual rings, while magneto-optical measurements with high spatial resolution can be used to probe the switching behaviour of ring structures with very high sensitivity. We illustrate how the ring geometry has been used for the study of a wide variety of magnetic phenomena, including the displacement of domain walls by electric currents, magnetoresistance, the strength of the pinning potential introduced by nanometre size constrictions, the effect of thermal excitations on the equilibrium state and the stochastic nature of switching events
International Nuclear Information System (INIS)
Misguich, J.H.
2004-04-01
As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation
Energy Technology Data Exchange (ETDEWEB)
Han, M., E-mail: mangui@gmail.com [State Key Laboratory of Electronic Thin Films & Integrated Devices, University of Electronic Science and Technology of China, Chengdu (China); Rozanov, K.N.; Zezyulina, P.A. [Institute for Theoretical and Applied Electromagnetics, Russian Academy of Sciences, Moscow (Russian Federation); Wu, Yan-Hui [State Key Laboratory of Electronic Thin Films & Integrated Devices, University of Electronic Science and Technology of China, Chengdu (China)
2015-06-01
Fe–Cu–Nb–Si–B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe{sub 3}(Si) with D0{sub 3} superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite. - Highlights: • Hyperfine interactions have been studied for the Fe-based nanocomposites. Please see Fig. 3. • The distribution of magnetic anisotropy has been derived from the initial magnetization curve of the composite. Please see Fig. 6. • The magnetic loss peak has been reconstructed from the measured permeability of composites and from the anisotropy field distribution. Please see Fig. 9.
International Nuclear Information System (INIS)
Han, M.; Rozanov, K.N.; Zezyulina, P.A.; Wu, Yan-Hui
2015-01-01
Fe–Cu–Nb–Si–B microflakes have been prepared by ball milling. The structural, magnetostatic and microwave permeability of the flakes and flake-filled composites have been studied. Two ferromagnetic phases, nanograins and amorphous matrix, are found in the flakes. The Mössbauer study shows that the nanograins are α-Fe 3 (Si) with D0 3 superlattice structure. High resolution transmission electron microscopy shows that the nanograins are well dispersed in the matrix. The microwave permeability of composites containing the flakes has been measured. The comparison of the intrinsic permeability of the flakes obtained from the permeability measurements and from the anisotropy field distribution reveals a disagreement in the magnetic loss peak location. It is concluded that the low-frequency loss in the composites is not due to the effect of eddy currents. The low-frequency loss may be attributed to other sources, such as domain wall motion or peculiarities of the magnetic structure of the flakes in the composite. - Highlights: • Hyperfine interactions have been studied for the Fe-based nanocomposites. Please see Fig. 3. • The distribution of magnetic anisotropy has been derived from the initial magnetization curve of the composite. Please see Fig. 6. • The magnetic loss peak has been reconstructed from the measured permeability of composites and from the anisotropy field distribution. Please see Fig. 9
Parallel pumping of a ferromagnetic nanostripe: Confinement quantization and off-resonant driving
Yarbrough, P. M.; Livesey, K. L.
2018-01-01
The parametric excitation of spin waves in a rectangular, ferromagnetic nanowire in the parallel pump configuration and with an applied field along the long axis of the wire is studied theoretically, using a semi-classical and semi-analytic Hamiltonian approach. We find that as a function of static applied field strength, there are jumps in the pump power needed to excite thermal spin waves. At these jumps, there is the possibility to non-resonantly excite spin waves near kz = 0. Spin waves with negative or positive group velocity and with different standing wave structures across the wire width can be excited by tuning the applied field. By using a magnetostatic Green's function that depends on both the nanowire's width and thickness—rather than just its aspect ratio—we also find that the threshold field strength varies considerably for nanowires with the same aspect ratio but of different sizes. Comparisons between different methods of calculations are made and the advantages and disadvantages of each are discussed.
Voltage-Controlled Reconfigurable Spin-Wave Nanochannels and Logic Devices
Rana, Bivas; Otani, YoshiChika
2018-01-01
Propagating spin waves (SWs) promise to be a potential information carrier in future spintronics devices with lower power consumption. Here, we propose reconfigurable nanochannels (NCs) generated by voltage-controlled magnetic anisotropy (VCMA) in an ultrathin ferromagnetic waveguide for SW propagation. Numerical micromagnetic simulations are performed to demonstrate the confinement of magnetostatic forward volumelike spin waves in NCs by VCMA. We demonstrate that the NCs, with a width down to a few tens of a nanometer, can be configured either into a straight or curved structure on an extended SW waveguide. The key advantage is that either a single NC or any combination of a number of NCs can be easily configured by VCMA for simultaneous propagation of SWs either with the same or different wave vectors according to our needs. Furthermore, we demonstrate the logic operation of a voltage-controlled magnonic xnor and universal nand gate and propose a voltage-controlled reconfigurable SW switch for the development of a multiplexer and demultiplexer. We find that the NCs and logic devices can even be functioning in the absence of the external-bias magnetic field. These results are a step towards the development of all-voltage-controlled magnonic devices with an ultralow power consumption.
Small planar domains in amorphous thin films: Nucleation and equilibrium conditions (abstract)
Labrune, M.; Hamzaoui, S.; Puchalska, I. B.; Battarel, C.; Hubert, A.
1984-03-01
The purpose of this work is to investigate a new type of small flat domain in the shape of lozenges. Such domains may be used for high-density nonvolatile shift register memories [C. Battarel, R. Morille, and A. Caplain, IEEE Trans. Magn. July (1983)]. Experimental and theoretical results for nucleation and stability of small lozenge domains less than 10 μm in length in Co-Ni-P and CoTi [G. Suran, K. Ounadjela, and J. Sztern (this Proceedings)] amorphous thin films 1500 Å thick are presented. The films have a low coercivity (Hc ˜1 Oe) and a significant in-plane uniaxial anisotropy (HK ˜35 Oe). The domains were observed in an optical microscope by longitudinal Kerr effect using an experimental method described by Prutton. Domain nucleation is obtained by applying a local field higher than HK. It must be emphasized that to stabilize the domain two constant fields having opposite direction are required: H1 applied inside the domain and parallel to its magnetization; H2 parallel to the main magnetization of the film (H1>H2). Experimental results obtained for such configuration of magnetic fields will be presented and compared with numerical computations. The theoretical model will be discussed and the role played by the magnetostatic energy emphasized. The model takes into account the spreading of the magnetic charges which appear at the boundary of the domain. Finally, application to experimental devices as mentioned in the first reference above will be shown.
Novak, R. L.; Garcia, F.; Novais, E. R. P.; Sinnecker, J. P.; Guimarães, A. P.
2018-04-01
Skyrmions are emerging topological spin structures that are potentially revolutionary for future data storage and spintronics applications. The existence and stability of skyrmions in magnetic materials is usually associated to the presence of the Dzyaloshinskii-Moriya interaction (DMI) in bulk magnets or in magnetic thin films lacking inversion symmetry. While some methods have already been proposed to generate isolated skyrmions in thin films with DMI, a thorough study of the conditions under which the skyrmions will remain stable in order to be manipulated in an integrated spintronic device are still an open problem. The stability of such structures is believed to be a result of ideal combinations of perpendicular magnetic anisotropy (PMA), DMI and the interplay between geometry and magnetostatics. In the present work we show some micromagnetic results supporting previous experimental observations of magnetic skyrmions in spin-valve stacks with a wide range of DMI values. Using micromagnetic simulations of cobalt-based disks, we obtain the magnetic ground state configuration for several values of PMA, DMI and geometric parameters. Skyrmion numbers, corresponding to the topological charge, are calculated in all cases and confirm the occurrence of isolated, stable, axially symmetric skyrmions for several combinations of DMI and anisotropy constant. The stability of the skyrmions in disks is then investigated under magnetic field and spin-polarized current, in finite temperature, highlighting the limits of applicability of these spin textures in spintronic devices.
Oblique whistler instability in the earth's foreshock
International Nuclear Information System (INIS)
Sentman, D.D.; Thomsen, M.F.; Gary, S.P.; Feldman, W.C.; Hoppe, M.M.
1983-01-01
The linear Vlasov stability properties of electron velocity distributions, similar to those observed in the upstream foreshock region in association with obliquely propagating whistler waves at approximately 1 Hz, are studied. These distributions are modeled by a sum of bi-Maxwellians with drift speeds parallel to the magnetic field B. We find such distributions to be stable to modes with wavevectors k parallel to B but unstable to whistler waves propagating obliquely to the magnetic field. The frequencies and wavelengths of these unstable modes agree well with those of whistlers observed upstream of the earth's bow shock. The free energy source driving the instability is a region of positive parallel slope partialf/sub e//partialv/sub parallel/>0 at large pitch angles (about 85 0 ) and intermediate energies (about 20 eV), probably corresponding to the solar wind electrons magnetostatically reflected from the magnetic ramp of the bow shock. The whistlers grow via electromagnetic Landau resonance with this free energy source
Full wave simulation of waves in ECRIS plasmas based on the finite element method
Energy Technology Data Exchange (ETDEWEB)
Torrisi, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania, Italy and Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell' Informazione, delle Infrastrutture e dell' Energia Sostenibile (DIIES), Via Graziella, I (Italy); Mascali, D.; Neri, L.; Castro, G.; Patti, G.; Celona, L.; Gammino, S.; Ciavola, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania (Italy); Di Donato, L. [Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica (DIEEI), Viale Andrea Doria 6, 95125 Catania (Italy); Sorbello, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123, Catania, Italy and Università degli Studi di Catania, Dipartimento di Ingegneria Elettrica Elettronica ed Informatica (DIEEI), Viale Andrea Doria 6, 95125 Catania (Italy); Isernia, T. [Università Mediterranea di Reggio Calabria, Dipartimento di Ingegneria dell' Informazione, delle Infrastrutture e dell' Energia Sostenibile (DIIES), Via Graziella, I-89100 Reggio Calabria (Italy)
2014-02-12
This paper describes the modeling and the full wave numerical simulation of electromagnetic waves propagation and absorption in an anisotropic magnetized plasma filling the resonant cavity of an electron cyclotron resonance ion source (ECRIS). The model assumes inhomogeneous, dispersive and tensorial constitutive relations. Maxwell's equations are solved by the finite element method (FEM), using the COMSOL Multiphysics{sup ®} suite. All the relevant details have been considered in the model, including the non uniform external magnetostatic field used for plasma confinement, the local electron density profile resulting in the full-3D non uniform magnetized plasma complex dielectric tensor. The more accurate plasma simulations clearly show the importance of cavity effect on wave propagation and the effects of a resonant surface. These studies are the pillars for an improved ECRIS plasma modeling, that is mandatory to optimize the ion source output (beam intensity distribution and charge state, especially). Any new project concerning the advanced ECRIS design will take benefit by an adequate modeling of self-consistent wave absorption simulations.
Parametric resonant states of charged fermions in the magnetar's crust
Dariescu, Marina-Aura; Dariescu, Ciprian
2013-06-01
We have presently derived the positive-energy solutions to the Dirac equation minimally coupled to a depth-dependent spatially harmonic tangential magnetostatic field to the magnetar crust, similar to the one proposed by Wareing and Hollerbach. It turns out that, for ultra-relativistic fermions and time-intervals much less the characteristic time (comparable to the average Ohmic timescale in the crust), the corresponding linearly independent modes get their depth-dependent amplitudes expressed in terms of Mathieu's functions and therefore, non-trivial resonances arise, leading to instabilities in the system, for computable ranges of the model parameters. In order to detail these features, we have also discussed the current density components, pointing out the regions for which the particle density has a double bounded modulation. Finally as the magnetic field induction is increasing, the instability range gets larger triggering the exponential growth of the amplitudes, once the imaginary part of the Mathieu Characteristic Exponent becomes more and more dominant.
Magnetic fields, stellar feedback, and the geometry of H II regions
Ferland, Gary J.
2009-04-01
Magnetic pressure has long been known to dominate over gas pressure in atomic and molecular regions of the interstellar medium. Here I review several recent observational studies of the relationships between the H+, H0 and H2 regions in M42 (the Orion complex) and M17. A simple picture results. When stars form they push back surrounding material, mainly through the outward momentum of starlight acting on grains, and field lines are dragged with the gas due to flux freezing. The magnetic field is compressed and the magnetic pressure increases until it is able to resist further expansion and the system comes into approximate magnetostatic equilibrium. Magnetic field lines can be preferentially aligned perpendicular to the long axis of quiescent cloud before stars form. After star formation and pushback occurs ionized gas will be constrained to flow along field lines and escape from the system along directions perpendicular to the long axis. The magnetic field may play other roles in the physics of the H II region and associated PDR. Cosmic rays may be enhanced along with the field and provide additional heating of atomic and molecular material. Wave motions may be associated with the field and contribute a component of turbulence to observed line profiles.
Fast vortex oscillations in a ferrimagnetic disk near the angular momentum compensation point
Kim, Se Kwon; Tserkovnyak, Yaroslav
2017-07-01
We theoretically study the oscillatory dynamics of a vortex core in a ferrimagnetic disk near its angular momentum compensation point, where the spin density vanishes but the magnetization is finite. Due to the finite magnetostatic energy, a ferrimagnetic disk of suitable geometry can support a vortex as a ground state similar to a ferromagnetic disk. In the vicinity of the angular momentum compensation point, the dynamics of the vortex resemble those of an antiferromagnetic vortex, which is described by equations of motion analogous to Newton's second law for the motion of particles. Owing to the antiferromagnetic nature of the dynamics, the vortex oscillation frequency can be an order of magnitude larger than the frequency of a ferromagnetic vortex, amounting to tens of GHz in common transition-metal based alloys. We show that the frequency can be controlled either by applying an external field or by changing the temperature. In particular, the latter property allows us to detect the angular momentum compensation temperature, at which the lowest eigenfrequency attains its maximum, by performing ferromagnetic resonance measurements on the vortex disk. Our work proposes a ferrimagnetic vortex disk as a tunable source of fast magnetic oscillations and a useful platform to study the properties of ferrimagnets.
International Nuclear Information System (INIS)
Vay, J.L.; Fawley, W.
2000-01-01
AMBER is a Particle-In-Cell (PIC) code which models the evolution of a representative slice of a relativistic electron beam in a linear accelerator. The beam is modeled as a steady flow and therefore no electromagnetic waves: all the fields (external and self-fields) are electrostatic and magnetostatic fields (for a complete description, see chapter 5). The possible elements describing the accelerator lattice are solenoids, accelerating gaps, pipes and apertures. Several kinds of beam distribution can be loaded: KV, gaussian, semi-gaussian, etc. Alternatively, the user can reconstruct (or load) a distribution from the output of another codefile, for example, an interface generating the beam distribution from output produced from EGUN or LSP codes is available as an option. This documentation first describes in detail the input files needed to run AMBER and the procedure to start the executable. The possible data files and graphical output are explained in the two following chapters. The last chapter describes the physics model and numerical techniques used. An example of input files and the result obtained with these inputs are also given in the Appendix
Directory of Open Access Journals (Sweden)
Gift S.
2009-01-01
Full Text Available In this paper, a new Quantum Theory of Magnetic Interaction is proposed. This is done under a relaxation of the requirement of covariance for Lorentz Boost Transformations. A modified form of local gauge invariance in which fermion field phase is allowed to vary with each space point but not each time point, leads to the introduction of a new compensatory field different from the electromagnetic field associated with the photon. This new field is coupled to the magnetic flux of the fermions and has quanta called magnatons, which are massless spin 1 particles. The associated equation of motion yields the Poisson equation for magnetostatic potentials. The magnatons mediate the magnetic interaction between magnetic dipoles including magnets and provide plausi- ble explanations for the Pauli exclusion principle, Chemical Reactivity and Chemical Bonds. This new interaction has been confirmed by numerical experiments. It estab- lishes magnetism as a force entirely separate from the electromagnetic interaction and converts all of classical magnetism into a quantum theory.
International Nuclear Information System (INIS)
Pshenichnikov, A.F.
2012-01-01
A new algorithm for calculating magnetic fields in a concentrated magnetic fluid with inhomogeneous density is proposed. Inhomogeneity of the fluid is caused by magnetophoresis. In this case, the diffusion and magnetostatic parts of the problem are tightly linked together and are solved jointly. The dynamic diffusion equation is solved by the finite volume method and, to calculate the magnetic field inside the fluid, an iterative process is performed in parallel. The solution to the problem is sought in Cartesian coordinates, and the computational domain is decomposed into rectangular elements. This technique eliminates the need to solve the related boundary-value problem for magnetic fields, accelerates computations and eliminates the error caused by the finite sizes of the outer region. Formulas describing the contribution of the rectangular element to the field intensity in the case of a plane problem are given. Magnetic and concentration fields inside the magnetic fluid filling a rectangular cavity generated under the action of the uniform external filed are calculated. - Highlights: ▶ New algorithm for calculating magnetic field intense magnetic fluid with account of magnetophoresis and diffusion of particles. ▶ We do not need to solve boundary-value problem, but we accelerate computations and eliminate some errors. ▶ We solve nonlinear flow equation by the finite volume method and calculate magnetic and focus fields in the fluid for plane case.
Inductive measurements of ferromagnetic resonance
International Nuclear Information System (INIS)
Woodward, R.C.; Kennewell, K.; Crew, D.C.; Stamps, R.L.
2004-01-01
Full text: The rapid advance in magnetic data storage has driven groundbreaking work in the science that underpins the properties of ferromagnetic materials at high frequencies. Recent work in this area has included the use of precession in order to produce ultra-high speed switching of magnetic elements, the generation of excited dynamical structures by application of inhomogeneous field pulses, and examination of the propagation of localized spin waves. This paper describes explorations of ultra-fast magnetization dynamics being undertaken at The University of Western Australia. We have studied the differences in magnetization dynamics in simple permalloy films when a sample is excited with sharp pulse compared to the to the dynamics generated by the application of a small amplitude continuous wave signal. We have observed a difference in the resonant frequency determined from these two excitations and will propose reasons for the different resonance responses of the system. Using the ultra-fast techniques described above we have measured dynamical properties that are significantly different to the static properties. These results are explained by the dynamical measurements being made on time scales smaller than the characteristic relaxation time. Future applications of these devices will be to examine broadening of line widths and frequency shifts associated with the excitation of magnetostatic modes, factors limiting quasiballistic reversal and differences between the dynamic and static properties of magnetic materials
Holzinger, Dennis; Koch, Iris; Burgard, Stefan; Ehresmann, Arno
2015-07-28
An approach for a remotely controllable transport of magnetic micro- and/or nanoparticles above a topographically flat exchange-bias (EB) thin film system, magnetically patterned into parallel stripe domains, is presented where the particle manipulation is achieved by sub-mT external magnetic field pulses. Superparamagnetic core-shell particles are moved stepwise by the dynamic transformation of the particles' magnetic potential energy landscape due to the external magnetic field pulses without affecting the magnetic state of the thin film system. The magnetic particle velocity is adjustable in the range of 1-100 μm/s by the design of the substrate's magnetic field landscape (MFL), the particle-substrate distance, and the magnitude of the applied external magnetic field pulses. The agglomeration of magnetic particles is avoided by the intrinsic magnetostatic repulsion of particles due to the parallel alignment of the particles' magnetic moments perpendicular to the transport direction and parallel to the surface normal of the substrate during the particle motion. The transport mechanism is modeled by a quantitative theory based on the precise knowledge of the sample's MFL and the particle-substrate distance.
Modelling of a free-surface ferrofluid flow
Energy Technology Data Exchange (ETDEWEB)
Habera, M., E-mail: habera@karlin.mff.cuni.cz; Hron, J., E-mail: hron@karlin.mff.cuni.cz
2017-06-01
The Cauchy's stress tensor of a ferrofluid exposed to an external magnetic field is subject to additional magnetic terms. For a linearly magnetizable medium, the terms result in interfacial magnetic force acting on the ferrofluid boundaries. This force changes the characteristics of many free-surface ferrofluid phenomena. The aim of this work is to implement this force into the incompressible Navier-Stokes equations and propose a numerical method to solve them. The interface of ferrofluid is tracked with the use of the characteristic level-set method and additional reinitialization step assures conservation of its volume. Incompressible Navier-Stokes equations are formulated for a divergence-free velocity fields while discrete interfacial forces are treated with continuous surface force model. Velocity-pressure coupling is implemented via the projection method. To predict the magnetic force effect quantitatively, Maxwell's equations for magnetostatics are solved in each time step. Finite element method is utilized for the spatial discretization. At the end of the work, equilibrium droplet shape are compared to known experimental results. - Highlights: • Incompressible Navier-Stokes equations are formulated for the problem of free-surface ferrofluid flow. • Computed equilibrium ferrofluid droplet shape is compared to known experimental result. • Magnetic field substantially changes the dynamics of ferrofluid dripping process.
Study and Design of a Linear Compressor of Voice-Coil Typ
Directory of Open Access Journals (Sweden)
VADAN, I.
2009-06-01
Full Text Available The paper presents the design and Finite Element (FEM analysis of a Linear compressor of voice coil type (LCVCT. This kind of linear compressor will be used in a refrigerator equipment. It is well-known that the replacing of the rotating compressor from a classical refrigerator by a linear compressor leads to an efficiency improving wit about 5% by avoiding the piston side friction, which is very important because of the huge number of refrigerators in operation world-wide. The linear compressor refrigerator is already commercially available in South Korea, equipped with an electromagnetic (fix coil and moving permanent magnet linear compressor. This paper presents a new type of linear compressor - a voice-coil type (fixed permanent magnet and moving coil. The operation principle is the same as for electrodynamic vibrator or electro-dynamic loud-speaker. The designing with rare earth permanent magnet is not a simple problem, because of the nonlinear characteristic of rare earth magnets. A magneto-static FEM analysis has been performed in order to validate the design methodology proposed in the paper.
Activation volume and interaction of metal particulate media
Energy Technology Data Exchange (ETDEWEB)
Tetsukawa, Hiroki [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan)]. E-mail: tetsukaw@arc.sony.co.jp; Kondo, Hirofumi [Sony Corporation, 6-7-35 Kitashinagawa, Shinagawa-ku, Tokyo 141-0001 (Japan)
2005-09-15
We have investigated the activation volume (V{sub ac}) and magnetostatic interaction of metal particulate (MP) media. The activation volume of MP media decreases with the decrease of physical volume (V{sub phy}) of metal particles. The activation volume and the ratio of V{sub phy}/V{sub ac} of advanced metal particles are 6x10{sup -24}m{sup 3} and 1.5, respectively. It can be predicted that the physical volume of metal particle is about 3x10{sup -24}m{sup 3} when the physical volume is equal to the activation volume. This value is agreement with the practical lower limit of physical volume of metal particle predicted by Sharrock. The negative interaction (demagnetization effect) in MP media decreases with low saturation magnetization of the metal particles, a thin magnetic layer, a high orientation of MP media, and a low packing fraction of metal particles in the MP media. The activation volume of the MP media decreased as the negative interactions decreased. In advanced MP media with low M{sub r}.t (M{sub r}=remanent magnetization and t=thickness), the influence of interaction on the activation volume is reduced.
Activation volume and interaction of metal particulate media
International Nuclear Information System (INIS)
Tetsukawa, Hiroki; Kondo, Hirofumi
2005-01-01
We have investigated the activation volume (V ac ) and magnetostatic interaction of metal particulate (MP) media. The activation volume of MP media decreases with the decrease of physical volume (V phy ) of metal particles. The activation volume and the ratio of V phy /V ac of advanced metal particles are 6x10 -24 m 3 and 1.5, respectively. It can be predicted that the physical volume of metal particle is about 3x10 -24 m 3 when the physical volume is equal to the activation volume. This value is agreement with the practical lower limit of physical volume of metal particle predicted by Sharrock. The negative interaction (demagnetization effect) in MP media decreases with low saturation magnetization of the metal particles, a thin magnetic layer, a high orientation of MP media, and a low packing fraction of metal particles in the MP media. The activation volume of the MP media decreased as the negative interactions decreased. In advanced MP media with low M r .t (M r =remanent magnetization and t=thickness), the influence of interaction on the activation volume is reduced
Correction of dynamic multipoles for APPLE-II undulator with flat wires
International Nuclear Information System (INIS)
Kikuchi, Y.; Hosaka, M.; Takashima, Y.; Yamamoto, N.; Adachi, M.; Zen, H.; Katoh, M.
2010-01-01
APPLE-II undulator can produce quasi-monochromatic light of different polarization though it is a relatively simple magnetic circuit. Therefore, it has been installed in many synchrotron radiation facilities and will be installed in Central Japan Synchrotron Radiation Research Facility under construction in Aichi prefecture. APPLE-II undulator also has been installed in UVSOR facility. When the undulator is operated in vertical polarization mode with narrower gap of 40 mm, the lifetime of electron beam through the storage ring significantly decreases.The reason is considered as dynamic multipole kicks in the undulator, which strongly depends on the undulator gap. Multi-wires, which are installed in the upper surface and the under surface of undulator beam duct, are candidate to compensate the multipole effects, because the multi-wires can generate arbitrary magnetic fields. This paper reports the result of numerical investigation on multipoles in the undulator by a three-dimensional magnetostatics computer code RADIA, the orbital calculation based on the numerical analysis and the preliminary experiment with flat wires. (author)
International Nuclear Information System (INIS)
Kusinski, Greg J.; Krishnan, Kannan M.; Thomas, Gareth; Nelson, E. C.
2000-01-01
Highly c-axis oriented Co 95 Cr 5 films with perpendicular anisotropy were grown epitaxially on Si (111), using an Ag seed layer, by physical vapor deposition. Films were characterized by x-ray diffraction, transmission electron microscopy (TEM), selected area electron diffraction, and Lorentz microscopy in a TEM. The following epitaxial relationship was confirmed: (111) Si (parallel sign)(111) Ag (parallel sign)(0001) CoCr ;[2(bar sign)20] Si (parallel sign)[2(bar sign)20] Ag (parallel sign)[1(bar sign)100] CoCr . Magnetic domain structures of these films were observed as a function of thickness; t, in the range, 200 Aa c ≅300 Aa, the magnetization was found to be effectively in-plane of the film, and above t c a regular, stripe-like domain pattern with a significant, alternating in sign, perpendicular component was observed. The spin reorientation transitions of the stripe domains to the in-plane magnetization were studied dynamically by observing the domains as a function of temperature by in situ heating up to 350 degree sign C. The critical transition thickness, t c , which is a function of K u and magnetostatic energy, was found to increase with increasing temperature. The stripe-domain period, L observed at room temperature was found to increase gradually with thickness; L=90 nm at t=300 Aa, and L=110 nm at t=700 Aa. (c) 2000 American Institute of Physics
Plasmas in compact traps: From ion sources to multidisciplinary research
Mascali, D.; Musumarra, A.; Leone, F.; Galatà, A.; Romano, F. P.; Gammino, S.
2017-09-01
In linear (minimum-B) magneto-static traps dense and hot plasmas are heated by electromagnetic radiation in the GHz domain via the Electron Cyclotron Resonance (ECR). The values of plasma density, temperature and confinement times ( n_eτ_i>10^{13} cm ^{-3} s; T_e>10 keV) are similar to the ones of thermonuclear plasmas. The research in this field -devoted to heating and confinement optimization- has been supported by numerical modeling and advanced diagnostics, for probing the plasma especially in a non-invasive way. ECR-based systems are nowadays able to produce extremely intense (tens or hundreds of mA) beams of light ions (p, d, He), and relevant currents of heavier elements (C, O, N) up to heavy ions like Xe, Pb, U. Such beams can be extracted from the trap by a proper electrostatic system. The above-mentioned properties make these plasmas very attractive for interdisciplinary researches also, such as i) nuclear decays rates measurements in stellar-like conditions, ii) energy conversion studies, being exceptional sources of short-wavelength electromagnetic radiation (EUV, X-rays, hard X-rays and gammas, useful in material science and archaeometry), iii) environments allowing precise spectroscopical measurements as benchmarks for magnetized astrophysical plasmas. The talk will give an overview about the state-of-the-art in the field of intense ion sources, and some new perspectives for interdisciplinary research, with a special attention to the developments based at INFN-LNS.
Bias and frequency response of the permeability of CoZrNb/SiO2 multilayers
International Nuclear Information System (INIS)
Louis, E.; Jeong, I.S.; Walser, R.M.
1990-01-01
Compared to single-layer films, CoZrNb/SiO 2 multilayers with amorphous, soft magnetic films exhibit increased high-frequency response (to about 100 MHz) that is not understood. We studied single and multilayer films in this system and observed three distinct types of magnetic bias and frequency responses (phases I--III). The high-frequency responses of phase II and III films were reduced from that of phase I. Phase changes were produced in the single-layer amorphous CoZrNb films by varying the film thickness, and in double-layer (N=2) and multilayer (N>2) films by varying the magnetic layer thickness. The phase boundaries in the former were shifted by magnetostatic coupling of the perpendicular component of M. These studies indicated that phase I films had uniform planar magnetizations, while phase II and III films had perpendicular components. The results are summarized in the form of a phase diagram (film thickness versus inverse film separation), which suggests that the frequency response of multilayer thin films is enhanced when the individual magnetic layers are sufficiently thin to insure a planar magnetization (phase I)
Energy Technology Data Exchange (ETDEWEB)
Misguich, J.H
2004-04-01
As a first step toward a nonlinear renormalized description of turbulence phenomena in magnetized plasmas, the lowest order quasi-linear description is presented here from a unified point of view for collisionless as well as for collisional plasmas in a constant magnetic field. The quasi-linear approximation is applied to a general kinetic equation obtained previously from the Klimontovich exact equation, by means of a generalised Dupree-Weinstock method. The so-obtained quasi-linear description of electromagnetic turbulence in a magnetoplasma is applied to three separate physical cases: -) weak electrostatic turbulence, -) purely magnetic field fluctuations (the classical quasi-linear results are obtained for cosmic ray diffusion in the 'slab model' of magnetostatic turbulence in the solar wind), and -) collisional kinetic equations of magnetized plasmas. This mathematical technique has allowed us to derive basic kinetic equations for turbulent plasmas and collisional plasmas, respectively in the quasi-linear and Landau approximation. In presence of a magnetic field we have shown that the systematic use of rotation matrices describing the helical particle motion allows for a much more compact derivation than usually performed. Moreover, from the formal analogy between turbulent and collisional plasmas, the results derived here in detail for the turbulent plasmas, can be immediately translated to obtain explicit results for the Landau kinetic equation.
Wang, Ren H.
1991-01-01
A method of combined use of magnetic vector potential (MVP) based finite element (FE) formulations and magnetic scalar potential (MSP) based FE formulations for computation of three-dimensional (3D) magnetostatic fields is developed. This combined MVP-MSP 3D-FE method leads to considerable reduction by nearly a factor of 3 in the number of unknowns in comparison to the number of unknowns which must be computed in global MVP based FE solutions. This method allows one to incorporate portions of iron cores sandwiched in between coils (conductors) in current-carrying regions. Thus, it greatly simplifies the geometries of current carrying regions (in comparison with the exclusive MSP based methods) in electric machinery applications. A unique feature of this approach is that the global MSP solution is single valued in nature, that is, no branch cut is needed. This is again a superiority over the exclusive MSP based methods. A Newton-Raphson procedure with a concept of an adaptive relaxation factor was developed and successfully used in solving the 3D-FE problem with magnetic material anisotropy and nonlinearity. Accordingly, this combined MVP-MSP 3D-FE method is most suited for solution of large scale global type magnetic field computations in rotating electric machinery with very complex magnetic circuit geometries, as well as nonlinear and anisotropic material properties.
Magnetoresistance and magnetization in submicron ferromagnetic gratings
Shearwood, C.; Blundell, S. J.; Baird, M. J.; Bland, J. A. C.; Gester, M.; Ahmed, H.; Hughes, H. P.
1994-05-01
A technique for engineering micron and submicron scale structures from magnetic films of transition metals has been developed using a combination of electron- and ion-beam lithography enabling high-quality arrays of submicron magnetic Fe wires to be fabricated. This process can be used to fabricate novel devices from a variety of metal combinations which would not be possible by the usual liftoff metallization method. The structure and magnetic properties are reported of an epitaxial 25 nm Fe(001)/GaAs(001) film and the wire gratings which are fabricated from it. The width of the wires in the grating is 0.5 μm for all structures studied, but the separation of each wire is varied in the range 0.5 to 16 μm. An artificially induced shape anisotropy field of around 1 kG, consistent with a magnetostatic calculation, was observed for all separations studied. The field dependence of the magneto-optic Kerr effect and magnetoresistance (MR) data is consistent with a twisted magnetization configuration across the width of the sample beneath saturation for transverse applied fields. In this case, the detailed form of the field dependence of the MR is strikingly modified from that observed in the continuous film and is consistent with coherent rotation of the magnetization.
Energy Technology Data Exchange (ETDEWEB)
Poduval, B., E-mail: bpoduval@spacescience.org [Space Science Institute, Boulder, CO 80303 (United States)
2016-08-10
This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE–SWS inverse relation exhibited significant temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008–2010 (CRs 2073–2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.
Martin, J. I.; Alija, A.; Sobrado, I.; Perez-Junquera, A.; Rodriguez-Rodriguez, G.; Velez, M.; Alameda, J. M.; Marconi, V. I.; Kolton, A. B.; Parrondo, J. M. R.
2009-03-01
The driven motion of domain walls in extended magnetic films patterned with 2D arrays of asymmetric holes has been found to be subject to two different crossed ratchet effects [1] which results in an inversion of the sign of domain wall motion rectification as a function of the applied magnetic field. This effect can be understood in terms of the competition between drive, elasticity and asymmetric pinning as revealed by a simple 4̂-model. In order to optimize the asymmetric hole design, the relevant energy landscapes for domain wall motion across the array of asymmetric holes have been calculated by micromagnetic simulations as a function of array geometrical characteristics. The effects of a transverse magnetic field on these two crossed ratchet effects will also be discussed in terms of the decrease in domain wall energy per unit area and of the modifications in the magnetostatic barriers for domain wall pinning at the asymmetric inclusions. Work supported by Spanish MICINN.[1] A. Perez-Junquera et al, Phys. Rev. Lett. 100 (2008) 037203
Model-based magnetization retrieval from holographic phase images
Energy Technology Data Exchange (ETDEWEB)
Röder, Falk, E-mail: f.roeder@hzdr.de [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Vogel, Karin [Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Wolf, Daniel [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); Triebenberg Labor, Institut für Strukturphysik, Technische Universität Dresden, D-01062 Dresden (Germany); Hellwig, Olav [Helmholtz-Zentrum Dresden-Rossendorf, Institut für Ionenstrahlphysik und Materialforschung, Bautzner Landstr. 400, D-01328 Dresden (Germany); AG Magnetische Funktionsmaterialien, Institut für Physik, Technische Universität Chemnitz, D-09126 Chemnitz (Germany); HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wee, Sung Hun [HGST, A Western Digital Company, 3403 Yerba Buena Rd., San Jose, CA 95135 (United States); Wicht, Sebastian; Rellinghaus, Bernd [IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, D-01171 Dresden (Germany)
2017-05-15
The phase shift of the electron wave is a useful measure for the projected magnetic flux density of magnetic objects at the nanometer scale. More important for materials science, however, is the knowledge about the magnetization in a magnetic nano-structure. As demonstrated here, a dominating presence of stray fields prohibits a direct interpretation of the phase in terms of magnetization modulus and direction. We therefore present a model-based approach for retrieving the magnetization by considering the projected shape of the nano-structure and assuming a homogeneous magnetization therein. We apply this method to FePt nano-islands epitaxially grown on a SrTiO{sub 3} substrate, which indicates an inclination of their magnetization direction relative to the structural easy magnetic [001] axis. By means of this real-world example, we discuss prospects and limits of this approach. - Highlights: • Retrieval of the magnetization from holographic phase images. • Magnetostatic model constructed for a magnetic nano-structure. • Decomposition into homogeneously magnetized components. • Discretization of a each component by elementary cuboids. • Analytic solution for the phase of a magnetized cuboid considered. • Fitting a set of magnetization vectors to experimental phase images.
FEM Analysis of a New Electromechanical Converter with Rolling Rotor and Axial Air-Gap
Directory of Open Access Journals (Sweden)
UNGUREANU, C.
2015-11-01
Full Text Available The paper presents the modeling of a new type of electromechanical converter with rolling rotor (ECRR in order to obtain an optimisation at functional level. The ECRR prototype comprises a stator composed of twelve magnetic poles and a disk-shaped rolling rotor made of ferromagnetic material, without windings. Each magnetic pole is made of an E-shaped magnetic system and a winding placed on its central column. The electromechanical converter with rolling rotor is analyzed through a magnetic field study with Flux2D software in magnetostatic application. The field study examines the influence of the rotor thickness, axial air-gap size and current density on the magnetic attraction force that changes the position of the disk-shaped rolling rotor. Also, it is analyzed the variation of the magnetic attraction force for different inclination angles of the rolling rotor. The main advantage of the ECRR is represented by a low rotational speed without using mechanical gearboxes. The ECRR prototype can be used in photovoltaic panels tracking systems.
On the role of topological complexity in spontaneous development of current sheets
Energy Technology Data Exchange (ETDEWEB)
Kumar, Sanjay; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)
2015-08-15
The computations presented in this work aim to asses the importance of field line interlacing on spontaneous development of current sheets. From Parker's magnetostatic theorem, such development of current sheets is inevitable in a topologically complex magnetofluid, with infinite electrical conductivity, at equilibrium. Relevant initial value problems are constructed by superposition of two untwisted component fields, each component field being represented by a pair of global magnetic flux surface. The intensity of field line interlacing is then specified by the relative amplitude of the two superposed fields. The computations are performed by varying this relative amplitude. Also to have a direct visualization of current sheet formation, we follow the evolution of flux surfaces instead of the vector magnetic field. An important finding of this paper is in the demonstration that initial field lines having intense interlacing tend to develop current sheets which are distributed throughout the computational domain with no preference for topologically favorable sites like magnetic nulls or field reversal layers. The onsets of these current sheets are attributed to favorable contortions of magnetic flux surfaces where two oppositely directed parts of the same field line or different field lines come to close proximity. However, for less intensely interlaced field lines, the simulations indicate development of current sheets at sites only where the magnetic topology is favorable. These current sheets originate as two sets of anti-parallel complimentary field lines press onto each other.
Effect of pb on the magnetic interactions of the M-type hexaferrites
Energy Technology Data Exchange (ETDEWEB)
Guerrero, A.L., E-mail: azdlobo@gmail.com [Instituto de Física de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico); Mirabal-García, M. [Instituto de Física de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico); Palomares-Sánchez, S.A.; Martínez, J.R. [Facultad de Ciencias de la Universidad Autónoma de San Luis Potosí, Álvaro Obregón No. 64, Col. Centro, San Luis Potosí, S.L.P. 78000, México (Mexico)
2016-02-01
This work reports the magnetic interactions of M-type lead hexaferrites. The samples were prepared using the solid state reaction method varying the lead concentration and compensating its lost by thermal treatment in order to obtain pure phases. The structural characterization was made through X-ray diffraction and the Rietveld refinement method. The morphology and grain-growth analysis were carried out using scanning electron microscopy. The magnetic interactions were studied through isothermal remanence (IRM) and DC demagnetization (DCD) remanence curves and through the construction of Henkel plots. By analyzing deviations from the Stoner–Wohlfarth model for non-interacting particles, it was determined the way in which lead modifies the interaction state in the hexaferrites. The experimental results show that the demagnetizing interactions prevail in systems with high lead content, and as lead concentration diminishes the intensity of magnetic interactions also decreases giving rise to magnetizing interactions - Highlights: • Construction of Henkel Plots of substituted hexaferrites. • Evaluation of magnetostatic and exchange interactions. • Effect of lead substitution on magnetic properties of the hexaferrites.
Development of a novel two-layer multiplate magnetorheological clutch for high-power applications
International Nuclear Information System (INIS)
Wang, Daoming; Tian, Zuzhi; Meng, Qingrui; Hou, Youfu
2013-01-01
A novel magnetorheological (MR) clutch for high-power applications is designed, simulated and tested. The clutch is implemented in a two-layer multiplate transmission form and adopts a two-way liquid cooling method to improve the heat dissipation capability. In this paper, a brief introduction to the transmission form of the proposed MR clutch is given first. Then, theoretical analyses of the output torque, magnetic circuit and temperature characteristic are conducted and further design details are presented and discussed, followed by a magnetostatic simulation of the designed circuit. A prototype of the clutch was fabricated and several tests were carried out to evaluate the torque transmission, time response and steady slip power of the prototype. The results show that the proposed MR clutch can produce a maximum output torque of 1545 N m and possesses a high steady slip power of up to 35 kW. Therefore, the developed two-layer multiplate MR clutch is promising for applications in many high-power situations. (paper)
Energy Technology Data Exchange (ETDEWEB)
Xue, Xu [Electronic Materials; amp,; Dong, Guohua [Electronic Materials; amp,; Zhou, Ziyao [Electronic Materials; amp,; Xian, Dan [Collaborative Innovation Center of High-End Manufacturing; Hu, Zhongqiang [Electronic Materials; amp,; Ren, Wei [Electronic Materials; amp,; Collaborative Innovation Center of High-End Manufacturing; Ye, Zuo-Guang [Electronic Materials; amp,; Department; Chen, Wei [Materials; Jiang, Zhuang-De [Collaborative Innovation Center of High-End Manufacturing; Liu, Ming [Electronic Materials; amp,; Collaborative Innovation Center of High-End Manufacturing
2017-12-01
Controlling spin dynamics through modulation of spin interactions in a fast, compact, and energy-efficient way is compelling for its abundant physical phenomena and great application potential in next-generation voltage controllable spintronic devices. In this work, we report electric field manipulation of spin dynamics-the two-magnon scattering (TMS) effect in Ni0.5Zn0.5Fe2O4 (NZFO)/Pb(Mg2/3Nb1/3)-PbTiO3 (PMN-PT) multiferroic heterostructures, which breaks the bottleneck of magnetostatic interaction-based magnetoelectric (ME) coupling in multiferroics. An alternative approach allowing spin-wave damping to be controlled by external electric field accompanied by a significant enhancement of the ME effect has been demonstrated. A two-way modulation of the TMS effect with a large magnetic anisotropy change up to 688 Oe has been obtained, referring to a 24 times ME effect enhancement at the TMS critical angle at room temperature. Furthermore, the anisotropic spin-freezing behaviors of NZFO were first determined via identifying the spatial magnetic anisotropy fluctuations. A large spin-freezing temperature change of 160 K induced by the external electric field was precisely determined by electron spin resonance.
Influence of Austenitic Steel Collar Dimensions on Magnetic Field Harmonics in the LHC Main Dipole
Bellesia, B; Todesco, Ezio
2005-01-01
The influence of the geometry of the collars in the main LHC dipole on the magnetic field harmonics is analyzed. The study aims at finding if the collar geometry is the driving mechanism of field quality for some harmonics and if the two different collar suppliers give a special signature on the magnetic field. Data of more than 700 magnets of the LHC series dipoles are analyzed and discussed. The main result of the analysis is that the collar shape is the driving mechanism of the magnetic field harmonics only for b2 and a3 in one of the three Cold Mass Assemblers (Firm3), where only collars of the supplier S2 are used. Two independent observations support this fact: firstly, strong correlations between apertures of the same magnet as expected from the assembly procedure have been found. Secondly, the expected values based on the measured dimensions of the collars and on a magneto-static model agree with magnetic measurements both for the average and for the standard deviation.
Directory of Open Access Journals (Sweden)
G.M. Golenkov
2015-12-01
Full Text Available Purpose. The research of the influence of value and direction of current on the equivalent spring magnetic force based on coaxial-linear motor (CLM – MS. Methodology. We carried out investigation of the equivalent harshness of magnetic spring with determination of electromechanical propulsion performance characteristics by the methods of computer modeling and experimental research of physical model of CLM – MS. The modeling of magnetic spring of CLM – MS is carried out by the finite-element method. The challenge is met as an axisymmetric challenge in cylindrical co-ordinates in magnetostatic approach. The experimental investigattion of the propulsion performance characteristics of magnetic spring is carried out on the test bench. Results. After the computer modeling and the experimental investigation of the electromechanical propulsion performance characteristics of magnetic spring the expressions of equivalent stiffness coefficient depending on the current in winding are obtained. The results of computer modeling are confirmed experimentally. Originality. The determination of equivalent stiffness coefficient of magnetic spring of vibration exciter based on coaxial-linear motor. Practical value. The obtained determination of equivalent stiffness coefficient of magnetic spring may be used in process of designing of vibration machines with devices for change of natural oscillation frequency.
Fliller, Raymond P; Hartung, Walter
2005-01-01
A system was developed at INFN Milano for preparing cesium telluride photo-cathodes and transferring them into an RF gun under ultra-high vacuum. This system has been in use at the Fermilab NICADD Photo-Injector Laboratory (FNPL) since 1997. A similar load-lock system is used at the TeSLA Test Facility at DESY-Hamburg. Two 1.625-cell high duty cycle RF guns have been fabricated for the project. Studies of the photo-emission and field emission ("dark current") behavior of both RF guns have been carried out. Unexpected phenomena were observed in one of the RF guns. In situ changes in the cathode's quantum efficiency and dark current with time were seen during operation of the photo-injector. These changes were correlated with the magnetostatic field at the cathode.* In addition, multipacting is observed in the RF guns under certain conditions. Recent measurements indicate a correlation between multipacting, anomalous photo-emission behavior, and anomalous field emission behavior. Results will be presented.
Joyce, Duncan; Parnell, William J; Assier, Raphaël C; Abrahams, I David
2017-05-01
In Parnell & Abrahams (2008 Proc. R. Soc. A 464 , 1461-1482. (doi:10.1098/rspa.2007.0254)), a homogenization scheme was developed that gave rise to explicit forms for the effective antiplane shear moduli of a periodic unidirectional fibre-reinforced medium where fibres have non-circular cross section. The explicit expressions are rational functions in the volume fraction. In that scheme, a (non-dilute) approximation was invoked to determine leading-order expressions. Agreement with existing methods was shown to be good except at very high volume fractions. Here, the theory is extended in order to determine higher-order terms in the expansion. Explicit expressions for effective properties can be derived for fibres with non-circular cross section, without recourse to numerical methods. Terms appearing in the expressions are identified as being associated with the lattice geometry of the periodic fibre distribution, fibre cross-sectional shape and host/fibre material properties. Results are derived in the context of antiplane elasticity but the analogy with the potential problem illustrates the broad applicability of the method to, e.g. thermal, electrostatic and magnetostatic problems. The efficacy of the scheme is illustrated by comparison with the well-established method of asymptotic homogenization where for fibres of general cross section, the associated cell problem must be solved by some computational scheme.
3D electromagnetic simulation of spatial autoresonance acceleration of electron beams
International Nuclear Information System (INIS)
Dugar-Zhabon, V D; Orozco, E A; González, J D
2016-01-01
The results of full electromagnetic simulations of the electron beam acceleration by a TE 112 linear polarized electromagnetic field through Space Autoresonance Acceleration mechanism are presented. In the simulations, both the self-sustaned electric field and selfsustained magnetic field produced by the beam electrons are included into the elaborated 3D Particle in Cell code. In this system, the space profile of the magnetostatic field maintains the electron beams in the acceleration regime along their trajectories. The beam current density evolution is calculated applying the charge conservation method. The full magnetic field in the superparticle positions is found by employing the trilinear interpolation of the mesh node data. The relativistic Newton-Lorentz equation presented in the centered finite difference form is solved using the Boris algorithm that provides visualization of the beam electrons pathway and energy evolution. A comparison between the data obtained from the full electromagnetic simulations and the results derived from the motion equation depicted in an electrostatic approximation is carried out. It is found that the self-sustained magnetic field is a factor which improves the resonance phase conditions and reduces the beam energy spread. (paper)
International Nuclear Information System (INIS)
Cunha, F.R.; Couto, H.L.G.
2011-01-01
Magnetostatic attraction may lead to formation of aggregates in stable colloidal magnetic suspensions and magneto-rheological suspensions. The aggregation problem of magnetic composites under differential sedimentation is a key problem in the control of the instability of non-Brownian suspensions. Against these attractive forces are the electrostatic repulsion and the hydrodynamic interactions acting as stabilizing effects to the suspension. This work concerns an investigation of the pairwise interaction of magnetic particles in a dilute sedimenting suspension. We focus attention on suspensions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number (negligible inertia) is small. The suspension is composed of magnetic micro-spheres of different radius and density immersed in a Newtonian fluid moving under the action of gravity. The theoretical calculations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of low particle Reynolds number. From the limiting trajectory in which aggregation occurs, we calculate the collision efficiency, representing the dimensionless rate at which aggregates are formed. The numerical results show clear evidence that the hydrodynamic interactions are of fundamental relevance in the process of magnetic particle aggregation. We compare the stabilizing effects between electrostatic repulsion and hydrodynamic interactions.
Head and bit patterned media optimization at areal densities of 2.5 Tbit/in2 and beyond
International Nuclear Information System (INIS)
Bashir, M.A.; Schrefl, T.; Dean, J.; Goncharov, A.; Hrkac, G.; Allwood, D.A.; Suess, D.
2012-01-01
Global optimization of writing head is performed using micromagnetics and surrogate optimization. The shape of the pole tip is optimized for bit patterned, exchange spring recording media. The media characteristics define the effective write field and the threshold values for the head field that acts at islands in the adjacent track. Once the required head field characteristics are defined, the pole tip geometry is optimized in order to achieve a high gradient of the effective write field while keeping the write field at the adjacent track below a given value. We computed the write error rate and the adjacent track erasure for different maximum anisotropy in the multilayer, graded media. The results show a linear trade off between the error rate and the number of passes before erasure. For optimal head media combinations we found a bit error rate of 10 -6 with 10 8 pass lines before erasure at 2.5 Tbit/in 2 . - Research Highlights: → Global optimization of writing head is performed using micromagnetics and surrogate optimization. → A method is provided to optimize the pole tip shape while maintaining the head field that acts in the adjacent tracks. → Patterned media structures providing an area density of 2.5 Tbit/in 2 are discussed as a case study. → Media reliability is studied, while taking into account, the magnetostatic field interactions from neighbouring islands and adjacent track erasure under the influence of head field.
Critical fields of an exchange coupled two-layer composite particle
International Nuclear Information System (INIS)
Goll, D.; Kronmueller, H.
2008-01-01
High-density recording systems require magnetic bits with perpendicular easy axis and large magnetocrystalline anisotropy to guarantee thermal stability. However, the large magnetic fields up to 10 T for the reversal of magnetization cannot be afforded by conventional write heads. Therefore, composite exchange coupled spring systems of soft and hard magnetic layers may be used to reduce the switching field. In this case the reversal of magnetization in general takes place in two steps: a nucleation process in the soft layer and a depinning process for the displacement of the domain wall at the phase boundary of the soft and the hard magnetic layer. The nucleation and depinning fields are determined on the basis of the continuum theory of micromagnetism. It is shown that the nucleation fields decrease according to a 1/L 2 law with increasing thickness L of the soft layer and the depinning field of the charged Neel wall may be reduced by factors of 3-6 in comparison with the ideal nucleation field of the hard magnetic phase. One-step rectangular hysteresis loops are obtained for thicknesses of the soft layer smaller than the exchange length of the magnetostatic field
Wei, Songrui; Liao, Xiaoqi; Gao, Yipeng; Yang, Sen; Wang, Dong; Song, Xiaoping
2017-11-08
Extensive efforts have been made in searching enhanced functionalities near the so-called morphotropic phase boundaries (MPBs) in both ferroelectric and ferromagnetic materials. Due to the exchange anti-symmetry of the wave function of fermions, it is widely recognized that the exchange interaction plays a critical role in ferromagnetism. As a quantum effect, the exchange interaction is magnitudes larger than electric interaction, leading to a fundamental difference between ferroelectricity and ferromagnetism. In this paper, we establish an energetic model capturing the interplay among the anisotropy energy, magnetostatic energy and the exchange energy to investigate systematically the effects of the exchange energy on the behavior of the ferromagnetic MPB. For the first time, it is found that the exchange energy can narrow the width of MPB region in the composition temperature phase diagram for ferromagnetic MPB systems. As temperature increases, MPB region becomes wider because of the weakening of the exchange interaction. Our simulation results suggest that the exchange energy play a critical role on the unique behavior of ferromagnetic MPB, which is in contrast different from that of ferroelectric MPB.
Self-organizing magnetic beads for biomedical applications
International Nuclear Information System (INIS)
Gusenbauer, Markus; Kovacs, Alexander; Reichel, Franz; Exl, Lukas; Bance, Simon; Özelt, Harald; Schrefl, Thomas
2012-01-01
In the field of biomedicine magnetic beads are used for drug delivery and to treat hyperthermia. Here we propose to use self-organized bead structures to isolate circulating tumor cells using lab-on-chip technologies. Typically blood flows past microposts functionalized with antibodies for circulating tumor cells. Creating these microposts with interacting magnetic beads makes it possible to tune the geometry in size, position and shape. We developed a simulation tool that combines micromagnetics and discrete particle dynamics, in order to design micropost arrays made of interacting beads. The simulation takes into account the viscous drag of the blood flow, magnetostatic interactions between the magnetic beads and gradient forces from external aligned magnets. We developed a particle–particle particle–mesh method for effective computation of the magnetic force and torque acting on the particles. - Highlights: ► We propose to use self-organized bead structures to isolate circulating tumor cells. ► Flexible ways are important to get a high probability of catching cancer cells. ► The beads make it possible to tune the geometry in size position and shape.
Necking down of sausages in current-carrying plasma pinches
International Nuclear Information System (INIS)
Trubnikov, B.A.; Zhdanov, S.K.
1986-01-01
The evolution of long-wave perturbations is shown to be equivalent, for various unstable media, to the dynamics of a gas with a negative adiabatic index γ. This evolution is described (for various values at N) by the quasi-Chaplygin system of equations Several examples of such media are considered, including a ''Chaplygin gas'' (N = 3), drops on a ceiling or ''solitons which have broken'' (N = 0), necks in a current-carrying plasma pinch with a skin effect, for both incompressible and compressible models (N = 2), and the breakup of liquid jets into drops (N = 3/2). A principle for selecting evolutionary solutions corresponding to the absence of perturbations in the limit t → -∞ is formulated. In the cases N = 0 and N = 2, a hodograph transformation reduces system (1) to a magnetostatic equation (ΔA)/sub phi/ = -(4π/c)j/sub phi/ and all the instability modes are equivalent to multipoles of circular currents which are localized on a circle. Exact solutions are given for periodic and isolated (localized) perturbations. The breakup of a medium into distinct blobs, in particular, the rupture of necks in a current-carrying plasma pinch, is demonstrated
Production, Characterization, and Acceleration of Optical Microbunches
Energy Technology Data Exchange (ETDEWEB)
Sears, Christopher M.S. [Stanford Univ., CA (United States)
2008-06-20
Optical microbunches with a spacing of 800 nm have been produced for laser acceleration research. The microbunches are produced using a inverse Free-Electron-Laser (IFEL) followed by a dispersive chicane. The microbunched electron beam is characterized by coherent optical transition radiation (COTR) with good agreement to the analytic theory for bunch formation. In a second experiment the bunches are accelerated in a second stage to achieve for the first time direct net acceleration of electrons traveling in a vacuum with visible light. This dissertation presents the theory of microbunch formation and characterization of the microbunches. It also presents the design of the experimental hardware from magnetostatic and particle tracking simulations, to fabrication and measurement of the undulator and chicane magnets. Finally, the dissertation discusses three experiments aimed at demonstrating the IFEL interaction, microbunch production, and the net acceleration of the microbunched beam. At the close of the dissertation, a separate but related research effort on the tight focusing of electrons for coupling into optical scale, Photonic Bandgap, structures is presented. This includes the design and fabrication of a strong focusing permanent magnet quadrupole triplet and an outline of an initial experiment using the triplet to observe wakefields generated by an electron beam passing through an optical scale accelerator.
Suppression of superconductivity in Nb by IrMn in IrMn/Nb bilayers
Wu, B. L.
2013-10-10
Effect of antiferromagnet on superconductivity has been investigated in IrMn/Nb bilayers. Significant suppression of both transition temperature (Tc) and lower critical field (Hc1) of Nb is found in IrMn/Nb bilayers as compared to a single layer Nb of same thickness; the suppression effect is even stronger than that of a ferromagnet in NiFe/Nb bilayers. The addition of an insulating MgO layer at the IrMn-Nb interface nearly restores Tc to that of the single layer Nb, but Hc1 still remains suppressed. These results suggest that, in addition to proximity effect and magnetic impurity scattering, magnetostatic interaction also plays a role in suppressing superconductivity of Nb in IrMn/Nb bilayers. In addition to reduced Tc and Hc1, the IrMn layer also induces broadening in the transition temperature of Nb, which can be accounted for by a finite distribution of stray field from IrMn.
Quantal density-functional theory in the presence of a magnetic field
International Nuclear Information System (INIS)
Yang Tao; Pan Xiaoyin; Sahni, Viraht
2011-01-01
We generalize the quantal density-functional theory (QDFT) of electrons in the presence of an external electrostatic field E(r)=-∇v(r) to include an external magnetostatic field B(r)=∇xA(r), where (v(r),A(r)) are the respective scalar and vector potentials. The generalized QDFT, valid for nondegenerate ground and excited states, is the mapping from the interacting system of electrons to a model of noninteracting fermions with the same density ρ(r) and physical current density j(r), and from which the total energy can be obtained. The properties (ρ(r),j(r)) constitute the basic quantum-mechanical variables because, as proved previously, for a nondegenerate ground state they uniquely determine the potentials (v(r),A(r)). The mapping to the noninteracting system is arbitrary in that the model fermions may be either in their ground or excited state. The theory is explicated by application to a ground state of the exactly solvable (two-dimensional) Hooke's atom in a magnetic field, with the mapping being to a model system also in its ground state. The majority of properties of the model are obtained in closed analytical or semianalytical form. A comparison with the corresponding mapping from a ground state of the (three-dimensional) Hooke's atom in the absence of a magnetic field is also made.
Topological Magnonics: A Paradigm for Spin-Wave Manipulation and Device Design
Wang, X. S.; Zhang, H. W.; Wang, X. R.
2018-02-01
Conventional magnonic devices use magnetostatic waves whose properties are sensitive to device geometry and the details of magnetization structure, so the design and the scalability of the device or circuitry are difficult. We propose topological magnonics, in which topological exchange spin waves are used as information carriers, that do not suffer from conventional problems of magnonic devices with additional nice features of nanoscale wavelength and high frequency. We show that a perpendicularly magnetized ferromagnet on a honeycomb lattice is generically a topological magnetic material in the sense that topologically protected chiral edge spin waves exist in the band gap as long as a spin-orbit-induced nearest-neighbor pseudodipolar interaction (and/or a next-nearest-neighbor Dzyaloshinskii-Moriya interaction) is present. The edge spin waves propagate unidirectionally along sample edges and domain walls regardless of the system geometry and defects. As a proof of concept, spin-wave diodes, spin-wave beam splitters, and spin-wave interferometers are designed by using sample edges and domain walls to manipulate the propagation of topologically protected chiral spin waves. Since magnetic domain walls can be controlled by magnetic fields or electric current or fields, one can essentially draw, erase, and redraw different spin-wave devices and circuitry on the same magnetic plate so that the proposed devices are reconfigurable and tunable. The topological magnonics opens up an alternative direction towards a robust, reconfigurable and scalable spin-wave circuitry.
HOW SOFT GAMMA REPEATERS MIGHT MAKE FAST RADIO BURSTS
Energy Technology Data Exchange (ETDEWEB)
Katz, J. I., E-mail: katz@wuphys.wustl.edu [Department of Physics and McDonnell Center for the Space Sciences, Washington University, St. Louis, Mo. 63130 (United States)
2016-08-01
There are several phenomenological similarities between soft gamma repeaters (SGRs) and fast radio bursts (FRBs), including duty factors, timescales, and repetition. The sudden release of magnetic energy in a neutron star magnetosphere, as in popular models of SGRs, can meet the energy requirements of FRBs, but requires both the presence of magnetospheric plasma, in order for dissipation to occur in a transparent region, and a mechanism for releasing much of that energy quickly. FRB sources and SGRs are distinguished by long-lived (up to thousands of years) current-carrying coronal arches remaining from the formation of the young neutron star, and their decay ends the phase of SGR/AXP/FRB activity even though “magnetar” fields may persist. Runaway increases in resistance when the current density exceeds a threshold, releases magnetostatic energy in a sudden burst, and produces high brightness GHz emission of FRB by a coherent process. SGRs are produced when released energy thermalizes as an equlibrium pair plasma. The failures of some alternative FRB models and the non-detection of SGR 1806-20 at radio frequencies are discussed in the appendices.
Study of high coercive force films made by vacuum deposition of cobalt onto chromium
International Nuclear Information System (INIS)
Randet, Denis
1969-01-01
A new method to make high coercive force films, by successive evaporations of chromium and cobalt, was demonstrated in 1966 at the 'Laboratoire d'Electronique et de Technologie de l'Informatique'. This work first contains a description of the magnetic properties of these films according to the conditions of preparation. These properties, which are isotropic in the plane of the film, are then related to the crystallographic structure of chromium and cobalt, in particular through electron microscopy. It is concluded that the coercive force is essentially due to the high magneto-crystalline anisotropy of cobalt in its hexagonal phase and depends, altogether with the shape of the hysteresis loop, on the magnetostatic coupling between the grains, which varies according to their dimensions. The chromium underlayer, if its surface is free enough of oxygen contamination, induces the growth of the hexagonal phase and influences the grain size of cobalt by a sort of epitaxy. At last, the behaviour of the Co/Cr films as a magnetic recording material is briefly examined and discussed. (author) [fr
International Nuclear Information System (INIS)
Samardak, Alexander; Sukovatitsina, Ekaterina; Ognev, Alexey; Stebliy, Maksim; Davydenko, Alexander; Chebotkevich, Ludmila; Keun Kim, Young; Nasirpouri, Forough; Janjan, Seyed-Mehdi; Nasirpouri, Farzad
2014-01-01
Magnetic states of nickel nanogranular films were studied in two distinct structures of individual and agglomerated granules electrodeposited on n-type Si(1 1 1) surface from a modified Watts bath at a low pH of 2. Magnetic force microscopy and micromagnetic simulations revealed three-dimensional out-of-plane magnetic vortex states in stand-alone hemispherical granules and their arrays, and multi-domain patterns in large agglomerates and integrated films. Once the granules coalesce into small chains or clusters, the coercivity values increased due to the reduction of inter-granular spacing and strengthening of the magnetostatic interaction. Further growth leads to the formation of a continuous granulated film which strongly affected the coercivity and remanence. This was characterized by the domain wall nucleation and propagation leading to a stripe domain pattern. Magnetoresistance measurements as a function of external magnetic field are indicative of anisotropic magnetoresistance (AMR) for the continuous films electrodeposited on Si substrate. - Highlights: • Magnetic states of electrodeposited nickel in isolated spherical and agglomerated nanogranules, and a continuous film. • Preferential magnetization reversal mechanism in isolated granules is vortex state. • Micromagnetic simulations confirm the three-dimensional vortex. • Transition between the vortex state and multi-domain magnetic pattern causes a significant decrease in the coercive force. • Continuous nickel films electrodeposited on silicon substrate exhibit AMR whose magnitude increases with the film thickness
Leung, Chung Ming; Zhuang, Xin; Xu, Junran; Li, Jiefang; Zhang, Jitao; Srinivasan, G.; Viehland, D.
2018-05-01
This report is on a new class of magnetostatically tunable magneto-impedance and magneto-capacitance devices based on a composite of ferromagnetic Metglas and ferroelectric lead zirconate titanate (PZT). Layered magneto-electric (ME) composites with annealed Metglas and PZT were studied in a longitudinal in-plane magnetic field-transverse electric field (L-T) mode. It was found that the degree of tunability was dependent on the annealing temperature of Metglas. An impedance tunability (ΔZ/Z0) of ≥400% was obtained at the electromechanical resonance (EMR) frequency (fr) for a sample with Metglas layers annealed at Ta = 500oC. This tunability is a factor of two higher than for composites with Metglas annealed at 350oC. The tunability of the capacitance, (ΔC/C0), was found to be 290% and -135k% at resonance and antiresonance, respectively, for Ta = 500oC. These results provide clear evidence for improvement in static magnetic field tunability of impedance and capacitance of ME composites with the use of annealed Metglas and are of importance for their potential use in tunable electronic applications.
Magnetic behavior of arrays of nickel nanowires
International Nuclear Information System (INIS)
Karim, S.; Maaz, K.; Ahmed, M.; Nisar, A.
2012-01-01
Recently, there is an increasing interest in magnetic nano wires because of their unusual properties compared to the bulk materials. To understand the complexity of nano wire arrays and to improve their potential in various applications more studies are still needed, for example, to understand completely the effect of geometrical factors, i.e. aspect ratio, areal density etc., on magnetic properties of these arrays. In this work, arrays of nickel nano wires with aspect ratio is proportional to 1200 and diameter ranging between 25-100 nm were fabricated by electrodeposition in etched ion track templates. Samples with areal density from 1 X 10/sup 6/ cm/sup -2/ to 1 X 10/ sup 8/ cm/sup -2/ were prepared. Measurements of magnetic hysteresis loops were performed at room temperature with SQUID magnetometer and magnetic properties of arrays of different diameters and aspect ratios were compared. Coercivity of the wires showed strong dependence on aspect ratio, diameter and microstructure. Room temperature coercivity of the wires showed a maximum at is proportional to 40 nm diameter and arrays with high density of nano wires showed lower coercivity. The results were discussed by taking into account anisotropies originating from the shape, crystalline structure and magnetostatic interactions among the wires and by previous experimental observations in literature. (Orig./A.B.)
Simulation models for computational plasma physics: Concluding report
International Nuclear Information System (INIS)
Hewett, D.W.
1994-01-01
In this project, the authors enhanced their ability to numerically simulate bounded plasmas that are dominated by low-frequency electric and magnetic fields. They moved towards this goal in several ways; they are now in a position to play significant roles in the modeling of low-frequency electromagnetic plasmas in several new industrial applications. They have significantly increased their facility with the computational methods invented to solve the low frequency limit of Maxwell's equations (DiPeso, Hewett, accepted, J. Comp. Phys., 1993). This low frequency model is called the Streamlined Darwin Field model (SDF, Hewett, Larson, and Doss, J. Comp. Phys., 1992) has now been implemented in a fully non-neutral SDF code BEAGLE (Larson, Ph.D. dissertation, 1993) and has further extended to the quasi-neutral limit (DiPeso, Hewett, Comp. Phys. Comm., 1993). In addition, they have resurrected the quasi-neutral, zero-electron-inertia model (ZMR) and began the task of incorporating internal boundary conditions into this model that have the flexibility of those in GYMNOS, a magnetostatic code now used in ion source work (Hewett, Chen, ICF Quarterly Report, July--September, 1993). Finally, near the end of this project, they invented a new type of banded matrix solver that can be implemented on a massively parallel computer -- thus opening the door for the use of all their ADI schemes on these new computer architecture's (Mattor, Williams, Hewett, submitted to Parallel Computing, 1993)
Magnetic force acting on a magnetic dipole over a superconducting thin film
International Nuclear Information System (INIS)
Wei, J.C.; Chen, J.L.; Horng, L.; Yang, T.J.
1996-01-01
The magnetostatic interaction energy and corresponding magnetic force acting on a magnetic point dipole placed above a type-II thin superconducting film in the mixed state with a single vortex are calculated using electromagnetics coupled with the London theory of superconductivity. If a vortex is trapped by a circular defect of radius b 1, where a is the separation between the dipole and the thin film, the only difference between two results is in the cutoff length, i.e., in the case of a circular defect the only difference in the critical position calculation is the cutoff at radius b rather than at coherence length ξ. The pinning force of a single vortex by a circular defect is also calculated. Further, we investigate the conditions of the vortex creation for various cases (including the first, second, and third vortices) for a free of pinning center in the examining region. It is found that the creation of a new single vortex in the thin film causes an abrupt change in vertical levitation force: the force changed discontinuously. copyright 1996 The American Physical Society
Iron nanoparticle assemblies: structures and magnetic behavior
International Nuclear Information System (INIS)
Farrell, D; Cheng, Y; Kan, S; Sachan, M; Ding, Y; Majetich, S A; Yang, L
2005-01-01
Self-assembly of spherical, surfactant-coated nanoparticles is discussed, an examples are presented to demonstrate the variety of structures that can be formed, and the conditions that lead to them. The effect of the concentration on the magnetic properties is then examined for 8.5 nm Fe nanoparticles. Dilute dispersions, arrays formed by evaporation of the dispersions, and nanoparticle crystals grown by slow diffusion of a poorly coordinating solvent were characterized by zero field-cooled magnetization, remanent hysteresis loop, and magnetic relaxation measurements. The average spacing between the particles was determined from a combination of transmission electron microscopy and small angle x-ray scattering. In the arrays the spacing was 2.5 nm between the edges of the particle cores, while in the nanoparticle crystals the particles were more tightly packed, with a separation of 1.1 nm. The reduced separation increased the magnetostatic interaction strength in the nanoparticle crystals, which showed distinctly different behavior in the rate of approach to saturation in the remanent hysteresis loops, and in the faster rate of time-dependent magnetic relaxation
Transparency of Magnetized Plasma at Cyclotron Frequency; TOPICAL
International Nuclear Information System (INIS)
G. Shvets; J.S. Wurtele
2002-01-01
Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration
Ngnegueu, Triomphant; Terme, Claude; Mailhot, Michel
1993-03-01
In this paper, the finite element method is applied for the computation of the magnetostatic field in the windings of a shell-form reactor. The modeling is carried out in 3D, using FLUX3D, a software developed at the Laboratoire d'Electrotechnique de Grenoble. The results are compared to those obtained in 2D. These calculation results are also compared to some test results. Dans cet article, nous décrivons une application de la méthode des éléments finis pour la modélisation du champ magnétostatique dans les enroulements d'une réactance cuirassée de grande puissance. La modélisation est conduite en 3D, en utilisant le logiciel FLUX3D. Les résultats du calcul sont comparés avec ceux obtenus en 2D. Quelques comparaisons sont aussi effectuées avec des résultats de mesure.
Directory of Open Access Journals (Sweden)
Frédéric Dubas
2017-10-01
Full Text Available This paper presents a new scientific contribution to the two-dimensional red(2-D subdomain technique in polar coordinates taking into account the finite relative permeability of the ferromagnetic material. The constant relative permeability corresponds to the linear part of the nonlinear B ( H curve. As in the conventional technique, the separation of variables method and the Fourier series are used for the resolution of magnetostatic Maxwell equations in each region. The general solutions of the magnetic field in subdomains, as well as the boundary conditions (BCs between regions are different from the conventional method. In the proposed method, the magnetic field solution in each subdomain is a superposition of two magnetic quantities in the two directions (i.e., r- and Θ -axis, and the BCs between two regions are also in both directions. For example, the scientific contribution has been applied to an air- or iron-cored coil supplied by a constant current. The distribution of local quantities (i.e., the magnetic vector potential and flux density has been validated by a corresponding 2-D finite-element analysis (FEA. The obtained semi-analytical results are in very good agreement with those of the numerical method.
International Nuclear Information System (INIS)
Clark, G.F.; Tanner, B.K.
1982-01-01
The domain structure changes occurring during magnetization of a (110) oriented disc of Tbsub(0.27) Dysub(0.73) Fe 2 have been studied by synchrotron X-radiation topography. Despite there being two easy directions in the specimen surface the commonest demagnetized configuration consisted of 71 0 walls on (001) between domains magnetized parallel to [111] and [1 bar 1 1], or [1 bar 1 1] and [1 bar 1 bar 1 1], etc. In each case one direction is inclined to the specimen surface and the configuration would appear to be somewhat unfavourable magnetostatically. Domain-wall energy calculations are presented for many possible wall geometries in the easy system, including magneto-elastic terms in the wall energy. These show that the 71 0 (001) walls have a very low wall energy. During magnetization in a field applied along principal crystallographic directions in the surface, a structure of skew 109 0 walls formed in low fields. This structure, between domains both magnetized in directions inclined to the surface, and having equal components of magnetization in the specimen plane, is immobile and does not move in the highest fields available. This explains the slow approach to saturation, following an initial rapid rise, observed in bulk magnetization experiments. (author)
Spin-transfer phenomena in layered magnetic structures: Physical phenomena and materials aspects
International Nuclear Information System (INIS)
Gruenberg, P.; Buergler, D.E.; Dassow, H.; Rata, A.D.; Schneider, C.M.
2007-01-01
During the past 20 years, layered structures consisting of ferromagnetic layers and spacers of various material classes with a thickness of only a few nanometers have revealed a variety of exciting and potentially very useful phenomena not present in bulk material. Representing distinct manifestations of spin-transfer processes, these phenomena may be categorized into interlayer exchange coupling (IEC), giant magnetoresistance (GMR), tunneling magnetoresistance (TMR), and the more recently discovered spin-transfer torque effect leading to current-induced magnetization switching (CIMS) and current-driven magnetization dynamics. These phenomena clearly confer novel material properties on magnetic layered structures with respect to the (magneto-)transport and the magnetostatic as well as magnetodynamic behavior. Here, we will first concentrate on the less well understood aspects of IEC across insulating and semiconducting interlayers and relate the observations to TMR in the corresponding structures. In this context, we will also discuss more recent advances in TMR due to the use of electrodes made from Heusler alloys and the realization of coherent tunneling in epitaxial magnetic tunneling junctions. Finally, we will review our results on CIMS in epitaxial magnetic nanostructures showing that normal and inverse CIMS can occur simultaneously in a single nanopillar device. In all cases discussed, material issues play a major role in the detailed understanding of the spin-transfer effects, in particular in those systems that yield the largest effects and are thus of utmost interest for applications
Pilan, N.; Antoni, V.; De Lorenzi, A.; Chitarin, G.; Veltri, P.; Sartori, E.
2016-02-01
A scheme of a neutral beam injector (NBI), based on electrostatic acceleration and magneto-static deflection of negative ions, is proposed and analyzed in terms of feasibility and performance. The scheme is based on the deflection of a high energy (2 MeV) and high current (some tens of amperes) negative ion beam by a large magnetic deflector placed between the Beam Source (BS) and the neutralizer. This scheme has the potential of solving two key issues, which at present limit the applicability of a NBI to a fusion reactor: the maximum achievable acceleration voltage and the direct exposure of the BS to the flux of neutrons and radiation coming from the fusion reactor. In order to solve these two issues, a magnetic deflector is proposed to screen the BS from direct exposure to radiation and neutrons so that the voltage insulation between the electrostatic accelerator and the grounded vessel can be enhanced by using compressed SF6 instead of vacuum so that the negative ions can be accelerated at energies higher than 1 MeV. By solving the beam transport with different magnetic deflector properties, an optimum scheme has been found which is shown to be effective to guarantee both the steering effect and the beam aiming.
Energy Technology Data Exchange (ETDEWEB)
Pilan, N., E-mail: nicola.pilan@igi.cnr.it; Antoni, V.; De Lorenzi, A.; Chitarin, G.; Veltri, P.; Sartori, E. [Consorzio RFX—Associazione EURATOM-ENEA per la Fusione, Corso Stati Uniti 4, 35127 Padova (Italy)
2016-02-15
A scheme of a neutral beam injector (NBI), based on electrostatic acceleration and magneto-static deflection of negative ions, is proposed and analyzed in terms of feasibility and performance. The scheme is based on the deflection of a high energy (2 MeV) and high current (some tens of amperes) negative ion beam by a large magnetic deflector placed between the Beam Source (BS) and the neutralizer. This scheme has the potential of solving two key issues, which at present limit the applicability of a NBI to a fusion reactor: the maximum achievable acceleration voltage and the direct exposure of the BS to the flux of neutrons and radiation coming from the fusion reactor. In order to solve these two issues, a magnetic deflector is proposed to screen the BS from direct exposure to radiation and neutrons so that the voltage insulation between the electrostatic accelerator and the grounded vessel can be enhanced by using compressed SF{sub 6} instead of vacuum so that the negative ions can be accelerated at energies higher than 1 MeV. By solving the beam transport with different magnetic deflector properties, an optimum scheme has been found which is shown to be effective to guarantee both the steering effect and the beam aiming.
The MICHELLE 2D/3D ES PIC Code Advances and Applications
Petillo, John; De Ford, John F; Dionne, Norman J; Eppley, Kenneth; Held, Ben; Levush, Baruch; Nelson, Eric M; Panagos, Dimitrios; Zhai, Xiaoling
2005-01-01
MICHELLE is a new 2D/3D steady-state and time-domain particle-in-cell (PIC) code* that employs electrostatic and now magnetostatic finite-element field solvers. The code has been used to design and analyze a wide variety of devices that includes multistage depressed collectors, gridded guns, multibeam guns, annular-beam guns, sheet-beam guns, beam-transport sections, and ion thrusters. Latest additions to the MICHELLE/Voyager tool are as follows: 1) a prototype 3D self magnetic field solver using the curl-curl finite-element formulation for the magnetic vector potential, employing edge basis functions and accumulating current with MICHELLE's new unstructured grid particle tracker, 2) the electrostatic field solver now accommodates dielectric media, 3) periodic boundary conditions are now functional on all grids, not just structured grids, 4) the addition of a global optimization module to the user interface where both electrical parameters (such as electrode voltages)can be optimized, and 5) adaptive mesh ref...
Numerical computation of gravitational field for general axisymmetric objects
Fukushima, Toshio
2016-10-01
We developed a numerical method to compute the gravitational field of a general axisymmetric object. The method (I) numerically evaluates a double integral of the ring potential by the split quadrature method using the double exponential rules, and (II) derives the acceleration vector by numerically differentiating the numerically integrated potential by Ridder's algorithm. Numerical comparison with the analytical solutions for a finite uniform spheroid and an infinitely extended object of the Miyamoto-Nagai density distribution confirmed the 13- and 11-digit accuracy of the potential and the acceleration vector computed by the method, respectively. By using the method, we present the gravitational potential contour map and/or the rotation curve of various axisymmetric objects: (I) finite uniform objects covering rhombic spindles and circular toroids, (II) infinitely extended spheroids including Sérsic and Navarro-Frenk-White spheroids, and (III) other axisymmetric objects such as an X/peanut-shaped object like NGC 128, a power-law disc with a central hole like the protoplanetary disc of TW Hya, and a tear-drop-shaped toroid like an axisymmetric equilibrium solution of plasma charge distribution in an International Thermonuclear Experimental Reactor-like tokamak. The method is directly applicable to the electrostatic field and will be easily extended for the magnetostatic field. The FORTRAN 90 programs of the new method and some test results are electronically available.
Wang, Xiang-Hua; Yin, Wen-Yan; Chen, Zhi Zhang David
2013-09-09
The one-step leapfrog alternating-direction-implicit finite-difference time-domain (ADI-FDTD) method is reformulated for simulating general electrically dispersive media. It models material dispersive properties with equivalent polarization currents. These currents are then solved with the auxiliary differential equation (ADE) and then incorporated into the one-step leapfrog ADI-FDTD method. The final equations are presented in the form similar to that of the conventional FDTD method but with second-order perturbation. The adapted method is then applied to characterize (a) electromagnetic wave propagation in a rectangular waveguide loaded with a magnetized plasma slab, (b) transmission coefficient of a plane wave normally incident on a monolayer graphene sheet biased by a magnetostatic field, and (c) surface plasmon polaritons (SPPs) propagation along a monolayer graphene sheet biased by an electrostatic field. The numerical results verify the stability, accuracy and computational efficiency of the proposed one-step leapfrog ADI-FDTD algorithm in comparison with analytical results and the results obtained with the other methods.
Magnetization process and domains in MTJ
Energy Technology Data Exchange (ETDEWEB)
Czapkiewicz, M.; Zoladz, M.; Wrona, J.; Wisniowski, P.; Rak, R.; Stobiecki, T. [Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland); Kim, C.G.; Kim, C.O. [Department of Materials Engineering, Chungnam National University, 305-764 Daejon (Korea); Takahashi, M.; Tsunoda, M. [Department of Electronic Engineering, Tohoku University, 980-8579 Sendai (Japan)
2004-06-01
The magnetization process and domain structure of free layers in as deposited and annealed magnetic tunnel junctions (MTJ) of Si/Ta/Cu/Ta/NiFe/Cu/IrMn(10)/CoFe(2.5)/Al-O(1.5)/CoFe(2.5)/NiFe(t)/Ta, where t=10, 30 and 100 nm, were investigated by Kerr microscopy, R-VSM and MOKE magnetometers. Different types of domain patterns observed in free layers (CoFe(2.5)/NiFe(t)) depending on the mutual relation between interlayer coupling energy and free layer magnetostatic energy. For as deposited samples fuzzy domains with fine irregular ''patches'' pattern, typical for weak interlayer coupling, are observed. Annealed MTJs, however, are characterized by large domains superimposed by crossed stripes, which led to the blocking of coherent rotation of magnetization. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
A ferrite nano-particles based fully printed process for tunable microwave components
Ghaffar, Farhan A.
2016-08-15
With the advent of nano-particles based metallic inks, inkjet printing emerged as an attractive medium for fast prototyping as well as for low cost and flexible electronics. However, at present, it is limited to printing of metallic inks on conventional microwave substrates. For fully printed designs, ideally, the substrate must also be printed. In this work, we demonstrate a fully printed process utilizing a custom Fe2O3 based magnetic ink for functional substrate printing and a custom silver-organo-complex (SOC) ink for metal traces printing. Due to the magnetic nature of the ink, this process is highly suitable for tunable microwave components. The printed magnetic substrate is characterized for the magnetostatic as well as microwave properties. The measured B(H) curve shows a saturation magnetization and remanence of 1560 and 350 Gauss respectively. As a proof of concept, a patch antenna is implemented in the proposed stack up which shows a tuning range of 4 % around the center frequency. © 2016 IEEE.
Directory of Open Access Journals (Sweden)
Gurubasavaraju T. M.
2018-01-01
Full Text Available Magnetorheological fluids are smart materials, which are responsive to the external stimulus and changes their rheological properties. The damper performance (damping force is dependent on the magnetic flux density induced at the annular gap. Magnetic flux density developed at fluid flow gap of MR damper due to external applied current is also dependent on materials properties of components of MR damper (such as piston head, outer cylinder and piston rod. The present paper discus about the influence of different materials selected for components of the MR damper on magnetic effect using magnetostatic analysis. Different materials such as magnetic and low carbon steels are considered for piston head of the MR damper and magnetic flux density induced at fluid flow gap (filled with MR fluid is computed for different DC current applied to the electromagnetic coil. Developed magnetic flux is used for calculating the damper force using analytical method for each case. The low carbon steel has higher magnetic permeability hence maximum magnetic flux could pass through the piston head, which leads to higher value of magnetic effect induction at the annular gap. From the analysis results it is observed that the magnetic steel and low carbon steel piston head provided maximum magnetic flux density. Eventually the higher damping force can be observed for same case.
International Nuclear Information System (INIS)
Sarawate, Neelesh N; Dapino, Marcelo J
2010-01-01
This paper presents an overview of the characterization and modeling of single crystal ferromagnetic shape memory Ni–Mn–Ga. A continuum thermodynamics model is presented which describes the magnetomechanical characterization of single crystal Ni–Mn–Ga for the following behavior: (i) sensing effect; (ii) actuation effect; (iii) blocked force (stress generation). The thermodynamic potentials, namely the magnetic Gibbs energy and the Gibbs energy, are obtained from the Helmholtz energy in order to arrive at the set of required independent and dependent variables; the potentials include magnetic energy consisting of Zeeman, magnetostatic and anisotropy components, and mechanical energy consisting of elastic and twinning components. Mechanical dissipation and the microstructure of Ni–Mn–Ga are incorporated in the continuum model through the internal state variables volume fraction, domain fraction, and magnetization rotation angle. The constitutive response of the material is obtained by restricting the process through the second law of thermodynamics. The model requires only seven parameters identified from two simple experiments. Several interesting characteristics of Ni–Mn–Ga are examined in concert with the magnetomechanical characterization
Magnetoactive elastomer as an element of a magnetic retina fixator
Makarova, L. A.; Nadzharyan, T. A.; Alekhina, Yu A.; Stepanov, G. V.; Kazimirova, E. G.; Perov, N. S.; Kramarenko, E. Yu
2017-09-01
We explore the possibility of creating an effective retinal fixator on the basis of magnetoactive elastomers (MAEs) and systems of permanent magnets. MAEs consist of silicone elastomer matrix with embedded magnetic iron microparticles. We study theoretically and experimentally magnetic forces acting between MAE samples and permanent magnets in various configurations. The theoretical model is based around classical magnetostatics and Maxwell equations with different parameters accounting for peculiarities of the material and the setup. Approximation of the experimentally measured magnetization curves for MAE samples was used to find input parameters for the theoretical model. To test the model, we conducted a series of experimental measurements of magnetic forces accompanied by model predictions for the system of one cylindrical magnet and a cuboid MAE sample. Calculated dependences of the average pressure arising from magnetic interactions on the distance between the closest faces of MAE samples and a permanent magnet are in a good agreement with the experimental data. The proof on concept for smaller magnetic systems required for eye surgery includes data for 10 magnets configuration and a thin MAE band. This research demonstrates high prospects of using MAE as an element of a magnetic fixator for treatment of complicated retinal detachments.
Xue, Xu; Dong, Guohua; Zhou, Ziyao; Xian, Dan; Hu, Zhongqiang; Ren, Wei; Ye, Zuo-Guang; Chen, Wei; Jiang, Zhuang-De; Liu, Ming
2017-12-13
Controlling spin dynamics through modulation of spin interactions in a fast, compact, and energy-efficient way is compelling for its abundant physical phenomena and great application potential in next-generation voltage controllable spintronic devices. In this work, we report electric field manipulation of spin dynamics-the two-magnon scattering (TMS) effect in Ni 0.5 Zn 0.5 Fe 2 O 4 (NZFO)/Pb(Mg 2/3 Nb 1/3 )-PbTiO 3 (PMN-PT) multiferroic heterostructures, which breaks the bottleneck of magnetostatic interaction-based magnetoelectric (ME) coupling in multiferroics. An alternative approach allowing spin-wave damping to be controlled by external electric field accompanied by a significant enhancement of the ME effect has been demonstrated. A two-way modulation of the TMS effect with a large magnetic anisotropy change up to 688 Oe has been obtained, referring to a 24 times ME effect enhancement at the TMS critical angle at room temperature. Furthermore, the anisotropic spin-freezing behaviors of NZFO were first determined via identifying the spatial magnetic anisotropy fluctuations. A large spin-freezing temperature change of 160 K induced by the external electric field was precisely determined by electron spin resonance.
International Nuclear Information System (INIS)
Kryshtal, R.G.; Medved, A.V.
2015-01-01
Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW – magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW – magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW – magnonic crystals are promising for signal processing in the GHz range. - Highlights: • Spin waves nonreciprocity in YIG magnonic crystals with SAW was studied. • SAW was shown to create nonreciprocity for spin waves in YIG–GGG even without metal. • Frequency and width of magnonic band gaps were measured versus metal conductivity. • Conductivity for practical use of spin waves in the structure YIG–metal was defined
Xue, Xu; Zhou, Ziyao; Dong, Guohua; Feng, Mengmeng; Zhang, Yijun; Zhao, Shishun; Hu, Zhongqiang; Ren, Wei; Ye, Zuo-Guang; Liu, Yaohua; Liu, Ming
2017-09-26
Electric field control of dynamic spin interactions is promising to break through the limitation of the magnetostatic interaction based magnetoelectric (ME) effect. In this work, electric field control of the two-magnon scattering (TMS) effect excited by in-plane lattice rotation has been demonstrated in a La 0.7 Sr 0.3 MnO 3 (LSMO)/Pb(Mn 2/3 Nb 1/3 )-PbTiO 3 (PMN-PT) (011) multiferroic heterostructure. Compared with the conventional strain-mediated ME effect, a giant enhancement of ME effect up to 950% at the TMS critical angle is precisely determined by angular resolution of the ferromagnetic resonance (FMR) measurement. Particularly, a large electric field modulation of magnetic anisotropy (464 Oe) and FMR line width (401 Oe) is achieved at 173 K. The electric-field-controllable TMS effect and its correlated ME effect have been explained by electric field modulation of the planar spin interactions triggered by spin-lattice coupling. The enhancement of the ME effect at various temperatures and spin dynamics control are promising paradigms for next-generation voltage-tunable spintronic devices.
Transparency of Magnetized Plasma at Cyclotron Frequency
International Nuclear Information System (INIS)
G. Shvets; J.S. Wurtele
2002-03-01
Electromagnetic radiation is strongly absorbed by a magnetized plasma if the radiation frequency equals the cyclotron frequency of plasma electrons. It is demonstrated that absorption can be completely canceled in the presence of a magnetostatic field of an undulator or a second radiation beam, resulting in plasma transparency at the cyclotron frequency. This effect is reminiscent of the electromagnetically induced transparency (EIT) of the three-level atomic systems, except that it occurs in a completely classical plasma. Unlike the atomic systems, where all the excited levels required for EIT exist in each atom, this classical EIT requires the excitation of the nonlocal plasma oscillation. The complexity of the plasma system results in an index of refraction at the cyclotron frequency that differs from unity. Lagrangian description was used to elucidate the physics and enable numerical simulation of the plasma transparency and control of group and phase velocity. This control naturally leads to applications for electromagnetic pulse compression in the plasma and electron/ion acceleration
International Nuclear Information System (INIS)
Vazquez, M.; Pirota, K.; Torrejon, J.; Navas, D.; Hernandez-Velez, M.
2005-01-01
Densely packed arrays of magnetic nanowires with hexagonal symmetry have been prepared by electrodeposition filling of the nanopores in alumina membranes previously formed by self-assembling induced by anodization. The influence of geometrical characteristics of arrays of Ni nanowires on their hysteresis loops have been studied. These characteristics are controlled by suitable choosing of preparation parameters: nanowires diameter ranges between 18 and 80 nm for lattice parameter of hexagonal symmetry of 65 and 105 nm, while length of nanowires is taken between 500 and 2000 nm. Additionally, the temperature dependence of coercivity when applying the field parallel to the nanowires or in-plane of the membrane has been measured. All these results allows us to conclude that magnetic behaviour is determined by the balance between different energy contributions, namely, the shape anisotropy of individual nanowires, the magnetostatic interaction among nanowires (confirmed to play a decisive role), and seemingly the magnetoelastic anisotropy induced in the nanowires by the alumina matrix through temperature changes as a consequence of their different thermal expansion coefficients
The magnetic structure and palaeomagnetic recording fidelity of sub-micron greigite (Fe3S4)
Valdez-Grijalva, Miguel A.; Nagy, Lesleis; Muxworthy, Adrian R.; Williams, Wyn; Fabian, Karl
2018-02-01
We present the results of a finite-element micromagnetic model of 30nm to 300nm greigite (Fe3S4) grains with a variety of equant morphologies. This grain size range covers the magnetic single-domain (SD) to pseudo single-domain (PSD) transition, and possibly also the PSD to multi-domain (MD) transition. The SD-PSD threshold d0 is determined to be 50nm ≤d0 ≤ 56nm depending on grain shape. The nudged elastic-band method was used to determine the room temperature energy barriers between stable states and thus the blocking volumes. It is found that, in the absence of interparticle magnetostatic interactions, the magnetisation of equant SD greigite is not stable on a geological scale and only PSD grains ≥ 70nm can be expected to carry a stable magnetisation over billion-year timescales, i.e., all non-interacting SD particles are essentially superparamagnetic. We further identify a mechanism for the PSD to multi-domain (MD) transition, which is of a continuous nature from PSD nucleation up to 300nm, when structures typical of MD behaviour like closure domains begin to form.
3-D magnetic field calculations for wiggglers using MAGNUS-3D
International Nuclear Information System (INIS)
Pissanetzky, S.; Tompkins, P.
1988-01-01
The recent but steady trend toward increased magnetic and geometric complexity in the design of wigglers and undulators, of which tapered wigglers, hybrid structures, laced electromagnetic wigglers, magnetic cladding, twisters and magic structures are examples, has caused a need for reliable 3-D computer models and a better understanding of the behavior of magnetic systems in three dimensions. The capabilities of the MAGNUS-3D Group of Programs are ideally suited to solve this class of problems and provide insight into 3-D effects. MAGNUS-3D can solve any problem of Magnetostatics involving permanent magnets, linear or nonlinear ferromagnetic materials and electric conductors of any shape in space. The magnetic properties of permanent magnets are described by the complete nonlinear demagnetization curve as provided by the manufacturer, or, at the user's choice, by a simpler approximation involving the coercive force, the residual induction and the direction of magnetization. The ferromagnetic materials are described by a magnetization table and an accurate interpolation relation. An internal library with properties of common industrial steels is available. The conductors are independent of the mesh and are described in terms of conductor elements from an internal library
3D accelerator magnet calculations using MAGNUS-3D
International Nuclear Information System (INIS)
Pissanetzky, S.; Miao, Y.
1989-01-01
The steady trend towards increased magnetic and geometric complexity in the design of accelerator magnets has caused a need for reliable 3D computer models and a better understanding of the behavior of magnetic system in three dimensions. The capabilities of the MAGNUS-3D family of programs are ideally suited to solve this class of problems and provide insight into 3D effects. MAGNUS-3D can solve any problem of magnetostatics involving permanent magnets, nonlinear ferromagnetic materials and electric conductors. MAGNUS-3D uses the finite element method and the two-scalar-potentials formulation of Maxwell's equations to obtain the solution, which can then be used interactively to obtain tables of field components at specific points or lines, plots of field lines, function graphs representing a field component plotted against a coordinate along any line in space (such as the beam line), and views of the conductors, the mesh and the magnetic bodies. The magnetic quantities that can be calculated include the force or torque on conductors or magnetic parts, the energy, the flux through a specified surface, line integrals of any field component along any line in space, and the average field or potential harmonic coefficients. We describe the programs with emphasis placed on their use for accelerator magnet design, and present an advanced example of actual calculations. (orig.)
Accelerating large-scale phase-field simulations with GPU
Directory of Open Access Journals (Sweden)
Xiaoming Shi
2017-10-01
Full Text Available A new package for accelerating large-scale phase-field simulations was developed by using GPU based on the semi-implicit Fourier method. The package can solve a variety of equilibrium equations with different inhomogeneity including long-range elastic, magnetostatic, and electrostatic interactions. Through using specific algorithm in Compute Unified Device Architecture (CUDA, Fourier spectral iterative perturbation method was integrated in GPU package. The Allen-Cahn equation, Cahn-Hilliard equation, and phase-field model with long-range interaction were solved based on the algorithm running on GPU respectively to test the performance of the package. From the comparison of the calculation results between the solver executed in single CPU and the one on GPU, it was found that the speed on GPU is enormously elevated to 50 times faster. The present study therefore contributes to the acceleration of large-scale phase-field simulations and provides guidance for experiments to design large-scale functional devices.
Maxwell: A new vision of the world
Maystre, Daniel
2014-05-01
The paper outlines the crucial contributions of James Clerk Maxwell to Physics and more generally to our vision of the world. He achieved 150 years ago a synthesis of the pioneering works in magnetostatics, electrostatics, induction and, by introducing the notion of displacement current, gave birth to Electromagnetics. Then, he deduced the existence of electromagnetic waves and identified light as one of them. Maxwell equations deeply changed a Newtonian conception of the world based on particle interactions by pointing out the vital role of waves in physics. This new conception had a strong influence on the development of quantum physics. Finally, the invariance of light velocity in Galilean frames led to Lorentz transformations, a key step toward the theory of relativity. Par ailleurs, les équations de Maxwell ont profondément changé une conception du monde newtonienne basée sur l'interaction entre particules en révélant le rôle essentiel des ondes en physique, ce qui eut une influence déterminante sur le développement de la physique quantique. Enfin, l'invariance de la vitesse de la lumière dans les repères galiléens a entraîné la découverte des transformations de Lorentz, une étape capitale vers la théorie de la relativité.
Nadzharyan, T. A.; Makarova, L. A.; Kazimirova, E. G.; Perov, N. S.; Kramarenko, E. Yu
2018-03-01
We study the effects the geometric configuration has on magnetic interactions between a magnetoactive elastomer (MAE) sample and various systems of permanent magnets for problems with both flat and curved geometry. MAEs consist of a silicone polymer matrix and iron filler microparticles embedded in it. Permanent magnets are cylindrical neodymium magnets arranged in a line on a flat or curved solid surfaces. We use computer simulations, namely the finite element method, in order to study the interaction force and magnetic pressure in a system with an MAE sample and permanent magnets. The model is based on classical Maxwell magnetostatics and two factors taking into account field dependence of MAE’s magnetic properties and inhomogeneities caused by local demagnetization. We calculate magnetic pressure dependences on various geometric parameters of the system, namely, the diameter and the height of permanent magnets, the distance between the magnets and dimensions of MAE samples. This research aims to create a set of guidelines for choosing the geometric configuration of a retina fixator based on MAE seals to be used in eye surgery for retinal detachment treatment.
Vortex formation in narrow ferromagnetic rings
International Nuclear Information System (INIS)
Klaeui, M; Vaz, C A F; Lopez-Diaz, L; Bland, J A C
2003-01-01
The high-symmetry ring geometry is shown to exhibit a wide range of intriguing magnetostatic and magnetodynamic properties, which we survey in this topical review. We consider first the patterning and deposition techniques, which are used to fabricate ring structures (diameters between 0.1 and 2 μm) and discuss their respective advantages and disadvantages. The results of direct nanoscale imaging of the novel magnetization configurations present in rings with different geometrical parameters (including discs) are discussed. These results give valuable insight into the influence of the magnetic anisotropies governing the magnetic states. The different types of domain walls that arise are compared quantitatively to micromagnetic simulations. The magnetodynamic switching between the different magnetic states is described in detail. In particular we elaborate on the different geometry-dependent magnetic switchings, since the different transitions occurring allow us to determine which energy terms govern the reversal process. We discuss a process by which fast (sub-ns) and controlled switching can be achieved, therefore making rings an attractive geometry for applications, in addition to studying fundamental issues of nanomagnetism. (topical review)
International Nuclear Information System (INIS)
Lipso, K.W.; Nielsen, K.K.; Christensen, D.V.; Bahl, C.R.H.; Engelbrecht, K.; Theil Kuhn, L.; Smith, A.
2011-01-01
The effect of demagnetization in a stack of gadolinium plates is determined experimentally by using spatially resolved measurements of the adiabatic temperature change due to the magnetocaloric effect. The number of plates in the stack, the spacing between them and the position of the plate on which the temperature is measured are varied. The orientation of the magnetic field is also varied. The measurements are compared to a magnetostatic model previously described. The results show that the magnetocaloric effect, due to the change in the internal field, is sensitive to the stack configuration and the orientation of the applied field. This may have significant implications for the construction of a magnetic cooling device. - Highlights: → The magnetocaloric effect is used as an indirect measure of the internal magnetic field. → To our knowledge nobody has published experimental determination of demagnetizing field in stack configurations of plates of magnetic material. → We present good agreement between the experimental results and an established numerical model. → This serves to show that the model may be used further to predict, e.g., optimal configurations.
A half mode inkjet printed tunable ferrite isolator
Ghaffar, Farhan A.
2017-10-24
A novel half mode waveguide based ferrite isolator design is presented in this work. For the first time, tunability of the isolation band is demonstrated for a ferrite isolator. Instead of using the conventional antisymmetric bias the isolator requires a single direction of the magnetic bias field due to the half mode operation. Yttrium Iron Garnet (YIG) is used as the substrate for the device. The metallic walls of the waveguide are realized using inkjet printing. The magnetic biasing applied to the waveguide causes the RF waves to experience negative permeability in one direction of propagation hence providing isolation for this direction. For an applied bias of 3000 Oe, the device provides a maximum isolation figure of merit of 76.7 dB at 7.5 GHz. The isolation band can be controlled by changing the applied magnetostatic bias. As the bias is varied from 1500 Oe to 3500 Oe the center frequency of the isolation band varies from 4.45 GHz to 9 GHz. The measured response of the isolator shows that it can be integrated in any RF system requiring lower cost and good isolation.
Investigation and Prediction of RF Window Performance in APT Accelerators
International Nuclear Information System (INIS)
Humphries, S. Jr.
1997-01-01
The work described in this report was performed between November 1996 and May 1997 in support of the APT (Accelerator Production of Tritium) Program at Los Alamos National Laboratory. The goal was to write and to test computer programs for charged particle orbits in RF fields. The well-documented programs were written in portable form and compiled for standard personal computers for easy distribution to LANL researchers. They will be used in several APT applications including the following. Minimization of multipactor effects in the moderate β superconducting linac cavities under design for the APT accelerator. Investigation of suppression techniques for electron multipactoring in high-power RF feedthroughs. Modeling of the response of electron detectors for the protection of high power RF vacuum windows. In the contract period two new codes, Trak-RF and WaveSim, were completed and several critical benchmark etests were carried out. Trak-RF numerically tracks charged particle orbits in combined electrostatic, magnetostatic and electromagnetic fields. WaveSim determines frequency-domain RF field solutions and provides a key input to Trak-RF. The two-dimensional programs handle planar or cylindrical geometries. They have several unique characteristics
Vaseem, Mohammad
2018-01-30
The field of printed electronics is still in its infancy and most of the reported work is based on commercially available nanoparticle-based metallic inks. Although fully printed devices that employ dielectric/semiconductor inks have recently been reported, there is a dearth of functional inks that can demonstrate controllable devices. The lack of availability of functional inks is a barrier to the widespread use of fully printed devices. For radio-frequency electronics, magnetic materials have many uses in reconfigurable components but rely on expensive and rigid ferrite materials. A suitable magnetic ink can facilitate the realization of fully printed, magnetically controlled, tunable devices. This report presents the development of an iron oxide nanoparticle-based magnetic ink. First, a tunable inductor is fully printed using iron oxide nanoparticle-based magnetic ink. Furthermore, iron oxide nanoparticles are functionalized with oleic acid to make them compatible with a UV-curable SU8 solution. Functionalized iron oxide nanoparticles are successfully embedded in the SU8 matrix to make a magnetic substrate. The as-fabricated substrate is characterized for its magnetostatic and microwave properties. A frequency tunable printed patch antenna is demonstrated using the magnetic and in-house silver-organo-complex inks. This is a step toward low-cost, fully printed, controllable electronic components.
Computational micromagnetics: prediction of time dependent and thermal properties
International Nuclear Information System (INIS)
Schrefl, T.; Scholz, W.; Suess, Dieter; Fidler, J.
2001-01-01
Finite element modeling treats magnetization processes on a length scale of several nanometers and thus gives a quantitative correlation between the microstructure and the magnetic properties of ferromagnetic materials. This work presents a novel finite element/boundary element micro-magnetics solver that combines a wavelet-based matrix compression technique for magnetostatic field calculations with a BDF/GMRES method for the time integration of the Gilbert equation of motion. The simulations show that metastable energy minima and nonuniform magnetic states within the grains are important factors in the reversal dynamics at finite temperature. The numerical solution of the Gilbert equation shows how reversed domains nucleate and expand. The switching time of submicron magnetic elements depends on the shape of the elements. Elements with slanted ends decrease the overall reversal time, as a transverse demagnetizing field suppresses oscillations of the magnetization. Thermal activated processes can be included adding a random thermal field to the effective magnetic field. Thermally assisted reversal was studied for CoCrPtTa thin-film media
Linear field demagnetisation of artificial magnetic square ice
Directory of Open Access Journals (Sweden)
Jason Phillip Morgan
2013-12-01
Full Text Available We have studied experimentally the states formed in artificial square ice nanomagnet systems following demagnetisation in a rotating in-plane applied magnetic field that reduces to zero in a manner that is linear in time. The final states are found to be controlled via the system's lattice constant, which determines the strength of the magnetostatic interactions between the elements, as well as the field ramping rate. We understand these effects as a requirement that the system undergoes a sufficiently large number of active rotations within the critical field window in which elements may be reversed, such that the interactions are allowed to locally exert their influence if the ground state is to be approached. On the other hand, if quenched disorder is too strong when compared to the interaction strength, any close approach to the ground state is impossible. These results show that it is not necessary for there to be any ac component to the field amplitude that is applied to the system during demagnetisation, which is the method almost exclusively employed in field protocols reported to date. Furthermore, by optimising the parameters of our linear demagnetisation protocol, the largest field-generated ground state domains yet reported are found.
Magnetic interactions in anisotropic Nd-Dy-Fe-Co-B/α-Fe multilayer magnets
Dai, Z. M.; Liu, W.; Zhao, X. T.; Han, Z.; Kim, D.; Choi, C. J.; Zhang, Z. D.
2016-10-01
The magnetic properties and the possible interaction mechanisms of anisotropic soft- and hard-magnetic multilayers have been investigated by altering the thickness of different kinds of spacer layers. The metal Ta and the insulating oxides MgO, Cr2O3 have been chosen as spacer layers to investigate the characteristics of the interactions between soft- and hard-magnetic layers in the anisotropic Nd-Dy-Fe-Co-B/α-Fe multilayer system. The dipolar and exchange interaction between hard and soft phases are evaluated with the help of the first order reversal curve method. The onset of the nucleation field and the magnetization reversal by domain wall movement are also evident from the first-order-reversal-curve measurements. Reversible/irreversible distributions reveal the natures of the soft- and hard-magnetic components. Incoherent switching fields are observed and the calculations show the semiquantitative contributions of hard and soft components to the system. An antiferromagnetic spacer layer will weaken the interaction between ferromagnetic layers and the effective interaction length decreases. As a consequence, the dipolar magnetostatic interaction may play an important role in the long-range interaction in anisotropic multilayer magnets.
Study of interlayer coupling between FePt and FeCoB thin films through MgO spacer layer
Singh, Sadhana; Kumar, Dileep; Gupta, Mukul; Reddy, V. Raghvendra
2017-05-01
Interlayer exchange coupling between hard-FePt and soft-FeCoB magnetic layers has been studied with increasing thickness of insulator MgO spacer layer in FePt/MgO/FeCoB sandwiched structure. A series of the samples were prepared in identical condition using ion beam sputtering method and characterized for their magnetic and structural properties using magneto-optical Kerr effect (MOKE) and X-ray reflectivity measurements. The nature of coupling between FePt and FeCoB was found to be ferromagnetic which decreases exponentially with increasing thickness of MgO layer. At very low thickness of MgO layer, both layers were found strongly coupled thus exhibiting coherent magnetization reversal. At higher thickness, both layers were found decoupled and magnetization reversal occurred at different switching fields. Strong coupling at very low thickness is attributed to pin holes in MgO layer which lead to direct coupling whereas on increasing thickness, coupling may arise due to magneto-static interactions.
Mapping of spin wave propagation in a one-dimensional magnonic crystal
Energy Technology Data Exchange (ETDEWEB)
Ordóñez-Romero, César L., E-mail: cloro@fisica.unam.mx; Lazcano-Ortiz, Zorayda; Aguilar-Huerta, Melisa; Monsivais, Guillermo [Instituto de Física, Universidad Nacional Autónoma de México, CU, México D.F. 04510 (Mexico); Drozdovskii, Andrey; Kalinikos, Boris [St. Petersburg Electrotechnical University, 197376 St. Petersburg (Russian Federation); International laboratory “MultiferrLab,” ITMO University, 197101 St. Petersburg (Russian Federation); Domínguez-Juárez, J. L. [Cátedras CONACyT, CFATA, Universidad Nacional Autónoma de México, Juriquilla, Querétaro 76230 (Mexico); Lopez-Maldonado, Guillermo [Universidad Autónoma Metropolitana, Lerma de Villada, 52006 Estado de México (Mexico); Qureshi, Naser; Kolokoltsev, Oleg [CCADET, Universidad Nacional Autónoma de México, CU, México D.F. 04510 (Mexico)
2016-07-28
The formation and evolution of spin wave band gaps in the transmission spectrum of a magnonic crystal have been studied. A time and space resolved magneto inductive probing system has been used to map the spin wave propagation and evolution in a geometrically structured yttrium iron garnet film. Experiments have been carried out using (1) a chemically etched magnonic crystal supporting the propagation of magnetostatic surface spin waves, (2) a short microwave pulsed excitation of the spin waves, and (3) direct spin wave detection using a movable magneto inductive probe connected to a synchronized fast oscilloscope. The results show that the periodic structure not only modifies the spectra of the transmitted spin waves but also influences the distribution of the spin wave energy inside the magnonic crystal as a function of the position and the transmitted frequency. These results comprise an experimental confirmation of Bloch′s theorem in a spin wave system and demonstrate good agreement with theoretical observations in analogue phononic and photonic systems. Theoretical prediction of the structured transmission spectra is achieved using a simple model based on microwave transmission lines theory. Here, a spin wave system illustrates in detail the evolution of a much more general physical concept: the band gap.
The Study of Spherical Cores with a Toroidal Magnetic Field Configuration
Energy Technology Data Exchange (ETDEWEB)
Gholipour, Mahmoud [Research Institute for Astronomy and Astrophysics of Maragha (RIAAM)—Maragha, P.O. Box 55134-441 (Iran, Islamic Republic of)
2017-04-01
Observational studies of the magnetic fields in molecular clouds have significantly improved the theoretical models developed for the structure and evolution of dense clouds and for the star formation process as well. The recent observational analyses on some cores indicate that there is a power-law relationship between magnetic field and density in the molecular clouds. In this study, we consider the stability of spherical cores with a toroidal magnetic field configuration in the molecular clouds. For this purpose, we model a spherical core that is in magnetostatic equilibrium. Herein, we propose an equation of density structure, which is a modified form of the isothermal Lane–Emden equation in the presence of the toroidal magnetic field. The proposed equation describes the effect of the toroidal magnetic field on the cloud structure and the mass cloud. Furthermore, we found an upper limit for this configuration of magnetic field in the molecular clouds. Then, the virial theorem is used to consider the cloud evolution leading to an equation in order to obtain the lower limit of the field strength in the molecular cloud. However, the results show that the field strength of the toroidal configuration has an important effect on the cloud structure, whose upper limit is related to the central density and field gradient. The obtained results address some regions of clouds where the cloud decomposition or star formation can be seen.
Effects of particle size on the spin reorientation transition in R2F14B (R=Nd, Er) hard magnets
International Nuclear Information System (INIS)
Foldeaki, M.; Koszegi, L.; Dunlap, R.A.
1991-01-01
Spin reorientation transitions (SRTs) were observed via ac-susceptibility measurements in powdered and as-cast R 2 F 14 B (R=Nd, Er) alloys. The temperature dependence of the susceptibility was found to be largely structure sensitive: powdered samples showed a moderate increase before the transition and a sharp decrease following the transition, while a sharp cusp in the susceptibility preceeded the transition in bulk samples. At the same time, the transition temperature and the relative intensity of the effects did not show any frequency dependence in the 0.1-10 kHz range. The results were compared with existing theoretical models assuming different magnetization mechanisms such as rotation of the magnetization vector, domain wall bowing and domain wall displacement. Domain wall contributions to the overall susceptibility cannot be neglected in either sample. At the same time, the rotational susceptibility is more significantly influenced by the sign reversal of the anisotropy constant, and this is the main contribution to the susceptibility maximum at the SRT. In powders, the expected sharp increase of the rotational susceptibility is counterbalanced by magnetostatic surface effects (''μ * effect''). In bulk materials the influence of surface effects is less significant and the cusp can be observed. (orig.)
Calculation of the Magnetic Fields of the Electric Power Line
Directory of Open Access Journals (Sweden)
Patsiuk V.
2016-12-01
Full Text Available The task of calculation of per unit length parameters of multi-conductor electrical overhead transmission lines has been treated in the paper. The calculation of distribution of electric and magnetic fields has been performed by means of the finite volume method for entire span of the line. The theoretical justification of the method for calculation the parameters of electromagnetic field taking into account the change of the vector of magnetic potential along the line has been given. The problems of electrostatic and magnetostatic for a single electric conductor and unlimited long conductor with current have been solved. For the inner and total inductivities of a single conductor under the current have been obtained relationships and drawn dependences. Dependence between the speeds of light and of electromagnetic wave’s propagation has been presented. Based on the characteristics of distribution of electric and magnetic fields of multi-conductor lines has been provided the method of calculation of the matrix of own and mutual capacitances and inductivities the calculated values of per unit length parameters of compact 110 kV electric line which is in concordance with one of basic physical constant – the speed of light.
MUMAX: A new high-performance micromagnetic simulation tool
International Nuclear Information System (INIS)
Vansteenkiste, A.; Van de Wiele, B.
2011-01-01
We present MUMAX, a general-purpose micromagnetic simulation tool running on graphical processing units (GPUs). MUMAX is designed for high-performance computations and specifically targets large simulations. In that case speedups of over a factor 100 x can be obtained compared to the CPU-based OOMMF program developed at NIST. MUMAX aims to be general and broadly applicable. It solves the classical Landau-Lifshitz equation taking into account the magnetostatic, exchange and anisotropy interactions, thermal effects and spin-transfer torque. Periodic boundary conditions can optionally be imposed. A spatial discretization using finite differences in two or three dimensions can be employed. MUMAX is publicly available as open-source software. It can thus be freely used and extended by community. Due to its high computational performance, MUMAX should open up the possibility of running extensive simulations that would be nearly inaccessible with typical CPU-based simulators. - Highlights: → Novel, open-source micromagnetic simulator on GPU hardware. → Speedup of ∝100x compared to other widely used tools. → Extensively validated against standard problems. → Makes previously infeasible simulations accessible.
Van der Waals enhancement of optical atom potentials via resonant coupling to surface polaritons.
Kerckhoff, Joseph; Mabuchi, Hideo
2009-08-17
Contemporary experiments in cavity quantum electrodynamics (cavity QED) with gas-phase neutral atoms rely increasingly on laser cooling and optical, magneto-optical or magnetostatic trapping methods to provide atomic localization with sub-micron uncertainty. Difficult to achieve in free space, this goal is further frustrated by atom-surface interactions if the desired atomic placement approaches within several hundred nanometers of a solid surface, as can be the case in setups incorporating monolithic dielectric optical resonators such as microspheres, microtoroids, microdisks or photonic crystal defect cavities. Typically in such scenarios, the smallest atom-surface separation at which the van der Waals interaction can be neglected is taken to be the optimal localization point for associated trapping schemes, but this sort of conservative strategy generally compromises the achievable cavity QED coupling strength. Here we suggest a new approach to the design of optical dipole traps for atom confinement near surfaces that exploits strong surface interactions, rather than avoiding them, and present the results of a numerical study based on (39)K atoms and indium tin oxide (ITO). Our theoretical framework points to the possibility of utilizing nanopatterning methods to engineer novel modifications of atom-surface interactions. (c) 2009 Optical Society of America
HOW SOFT GAMMA REPEATERS MIGHT MAKE FAST RADIO BURSTS
International Nuclear Information System (INIS)
Katz, J. I.
2016-01-01
There are several phenomenological similarities between soft gamma repeaters (SGRs) and fast radio bursts (FRBs), including duty factors, timescales, and repetition. The sudden release of magnetic energy in a neutron star magnetosphere, as in popular models of SGRs, can meet the energy requirements of FRBs, but requires both the presence of magnetospheric plasma, in order for dissipation to occur in a transparent region, and a mechanism for releasing much of that energy quickly. FRB sources and SGRs are distinguished by long-lived (up to thousands of years) current-carrying coronal arches remaining from the formation of the young neutron star, and their decay ends the phase of SGR/AXP/FRB activity even though “magnetar” fields may persist. Runaway increases in resistance when the current density exceeds a threshold, releases magnetostatic energy in a sudden burst, and produces high brightness GHz emission of FRB by a coherent process. SGRs are produced when released energy thermalizes as an equlibrium pair plasma. The failures of some alternative FRB models and the non-detection of SGR 1806-20 at radio frequencies are discussed in the appendices.
Energy Technology Data Exchange (ETDEWEB)
Kryshtal, R.G.; Medved, A.V., E-mail: avm@ms.ire.rssi.ru
2015-12-01
Experimental results of investigations of nonreciprocity for surface magnetostatic spin waves (SMSW) in the magnonic crystal created by surface acoustic waves (SAW) in yttrium iron garnet films on a gallium gadolinium garnet substrate as without metallization and with aluminum films with different electrical conductivities (thicknesses) are presented. In structures without metallization, the frequency of magnonic gaps is dependent on mutual directions of propagation of the SAW and SMSW, showing nonreciprocal properties for SMSW in SAW – magnonic crystals even with the symmetrical dispersion characteristic. In metalized SAW – magnonic crystals the shift of the magnonic band gaps frequencies at the inversion of the biasing magnetic field was observed. The frequencies of magnonic band gaps as functions of SAW frequency are presented. Measured dependencies, showing the decrease of magnonic gaps frequency and the expansion of the magnonic band gap width with the decreasing of the metal film conductivity are given. Such nonreciprocal properties of the SAW – magnonic crystals are promising for signal processing in the GHz range. - Highlights: • Spin waves nonreciprocity in YIG magnonic crystals with SAW was studied. • SAW was shown to create nonreciprocity for spin waves in YIG–GGG even without metal. • Frequency and width of magnonic band gaps were measured versus metal conductivity. • Conductivity for practical use of spin waves in the structure YIG–metal was defined.
Energy Technology Data Exchange (ETDEWEB)
Cunha, F.R., E-mail: frcunha@unb.b [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil); Couto, H.L.G. [Universidade de Brasilia, Faculdade de Tecnologia, Depto. de Engenharia Mecanica, Grupo de Mecanica dos Fluidos de Escoamentos Complexos - VORTEX, Campus Universitario Darcy Ribeiro, 70910-900, Brasilia, DF (Brazil)
2011-01-15
Magnetostatic attraction may lead to formation of aggregates in stable colloidal magnetic suspensions and magneto-rheological suspensions. The aggregation problem of magnetic composites under differential sedimentation is a key problem in the control of the instability of non-Brownian suspensions. Against these attractive forces are the electrostatic repulsion and the hydrodynamic interactions acting as stabilizing effects to the suspension. This work concerns an investigation of the pairwise interaction of magnetic particles in a dilute sedimenting suspension. We focus attention on suspensions where the Peclet number is large (negligible Brownian motion) and where the Reynolds number (negligible inertia) is small. The suspension is composed of magnetic micro-spheres of different radius and density immersed in a Newtonian fluid moving under the action of gravity. The theoretical calculations are based on direct computations of the hydrodynamic and the magnetic interactions among the rigid spheres in the regime of low particle Reynolds number. From the limiting trajectory in which aggregation occurs, we calculate the collision efficiency, representing the dimensionless rate at which aggregates are formed. The numerical results show clear evidence that the hydrodynamic interactions are of fundamental relevance in the process of magnetic particle aggregation. We compare the stabilizing effects between electrostatic repulsion and hydrodynamic interactions.
Macroscopic kinematics of the Hall electric field under influence of carrier magnetic moments
International Nuclear Information System (INIS)
Sakai, Masamichi
2016-01-01
The relativistic effect on electromagnetic forces yields two types of forces which depend on the velocity of the relevant particles: (i) the usual Lorentz force exerted on a moving charged particle and (ii) the apparent Lorentz force exerted on a moving magnetic moment. In sharp contrast with type (i), the type (ii) force originates due to the transverse field induced by the Hall effect (HE). This study incorporates both forces into a Drude-type equation with a fully spin-polarized condition to investigate the effects of self-consistency of the source and the resultant fields on the HE. We also examine the self-consistency of the carrier kinematics and electromagnetic dynamics by simultaneously considering the Drude type equation and Maxwell equations at low frequencies. Thus, our approach can predict both the dc and ac characteristics of the HE, demonstrating that the dc current condition solely yields the ordinary HE, while the ac current condition yields generation of both fundamental and second harmonic modes of the HE field. When the magnetostatic field is absent, the simultaneous presence of dc and ac longitudinal currents generates the ac HE that has both fundamental frequency and second harmonic.
Cylindrical prominences and the magnetic influence of the photospheric boundary
International Nuclear Information System (INIS)
Lerche, I.; Chicago Univ., IL; Low, B.C.
1980-01-01
We construct exact, non-linear, solutions for an horizontal, cylindrical, current-carrying, prominence supported against solar gravity by the action of a Lorentz force. The solutions incorporate the photosphere boundary condition, proposed by van Tend and Kuperus (1978), and analyzed by them for line filaments. Our solutions have finite radius for the prominence material and, as well as satisfying the equations of magnetostatic equilibrium, they allow for the continuity of gas pressure, and of the normal and tangential components of magnetic field across the circular prominence boundary. We show that an infinity of solutions is possible and we illustrate the basic behavior by investigation of a special case. We also give a prescription for constructing equilibrium fields for any horizontal prominence with arbitrary cross-section and with an arbitrary external magnetic field. The prescription is ideally suited for numerical codes and we suggest that both the equilibrium of such shapes can easily be accomplished numerically together with their evolutionary history. (orig.)
FastMag: Fast micromagnetic simulator for complex magnetic structures (invited)
Chang, R.; Li, S.; Lubarda, M. V.; Livshitz, B.; Lomakin, V.
2011-04-01
A fast micromagnetic simulator (FastMag) for general problems is presented. FastMag solves the Landau-Lifshitz-Gilbert equation and can handle multiscale problems with a high computational efficiency. The simulator derives its high performance from efficient methods for evaluating the effective field and from implementations on massively parallel graphics processing unit (GPU) architectures. FastMag discretizes the computational domain into tetrahedral elements and therefore is highly flexible for general problems. The magnetostatic field is computed via the superposition principle for both volume and surface parts of the computational domain. This is accomplished by implementing efficient quadrature rules and analytical integration for overlapping elements in which the integral kernel is singular. Thus, discretized superposition integrals are computed using a nonuniform grid interpolation method, which evaluates the field from N sources at N collocated observers in O(N) operations. This approach allows handling objects of arbitrary shape, allows easily calculating of the field outside the magnetized domains, does not require solving a linear system of equations, and requires little memory. FastMag is implemented on GPUs with ?> GPU-central processing unit speed-ups of 2 orders of magnitude. Simulations are shown of a large array of magnetic dots and a recording head fully discretized down to the exchange length, with over a hundred million tetrahedral elements on an inexpensive desktop computer.
High intensity positron program at LLNL
International Nuclear Information System (INIS)
Asoka-Kumar, P.; Howell, R.; Stoeffl, W.; Carter, D.
1999-01-01
Lawrence Livermore National Laboratory (LLNL) is the home of the world close-quote s highest current beam of keV positrons. The potential for establishing a national center for materials analysis using positron annihilation techniques around this capability is being actively pursued. The high LLNL beam current will enable investigations in several new areas. We are developing a positron microprobe that will produce a pulsed, focused positron beam for 3-dimensional scans of defect size and concentration with submicron resolution. Below we summarize the important design features of this microprobe. Several experimental end stations will be available that can utilize the high current beam with a time distribution determined by the electron linac pulse structure, quasi-continuous, or bunched at 20 MHz, and can operate in an electrostatic or (and) magnetostatic environment. Some of the planned early experiments are: two-dimensional angular correlation of annihilation radiation of thin films and buried interfaces, positron diffraction holography, positron induced desorption, and positron induced Auger spectroscopy. copyright 1999 American Institute of Physics
The Mechanics of a Chain or Ring of Spherical Magnets
Hall, Cameron L.; Vella, Dominic; Goriely, Alain
2013-01-01
Strong magnets, such as neodymium-iron-boron magnets, are increasingly being manufactured as spheres. Because of their dipolar characters, these spheres can easily be arranged into long chains that exhibit mechanical properties reminiscent of elastic strings or rods. While simple formulations exist for the energy of a deformed elastic rod, it is not clear whether or not they are also appropriate for a chain of spherical magnets. In this paper, we use discrete-to-continuum asymptotic analysis to derive a continuum model for the energy of a deformed chain of magnets based on the magnetostatic interactions between individual spheres. We find that the mechanical properties of a chain of magnets differ significantly from those of an elastic rod: while both magnetic chains and elastic rods support bending by change of local curvature, nonlocal interaction terms also appear in the energy formulation for a magnetic chain. This continuum model for the energy of a chain of magnets is used to analyze small deformations of a circular ring of magnets and hence obtain theoretical predictions for the vibrational modes of a circular ring of magnets. Surprisingly, despite the contribution of nonlocal energy terms, we find that the vibrations of a circular ring of magnets are governed by the same equation that governs the vibrations of a circular elastic ring. Copyright © by SIAM.
Magnetic particles in medical research - a review
International Nuclear Information System (INIS)
Sajid, K.M.
2001-01-01
Magnetic (or magnetizable) particles have assumed increasing importance in medical and biological research since 1966 when the effect of a magnetic field on the movement of suspended particles was initially studied. In fields like haematology, cell biology, microbiology, biochemistry and immunoassays, they currently provide the basis for separation techniques, which previously relied on gravitational forces. The body cells (e.g., blood cells) can be made magnetic by incubating them in a medium containing several Fe/sub 3/O/sub 4/ particles, which are adsorbed to the membrane surfaces. Some bacteria (also called magnetostatic bacteria) respond to externally applied magnetic lines of force due to their intracellular magnetic particles. These properties are useful in the isolation of these cells/bacteria. In biochemistry magnetic particles are used to immobilize enzymes without any loss of enzyme activity. The immobilized enzymes can facilitate the separation of end products without extensive instrumentation. In immunoassays the antibodies are covalently linked to polymer coated iron oxide particles. An electromagnet is used to sediment these particles after reaction. This excludes the use of centrifuge to separate antigen-antibody complexes. In pharmacy and pharmacology the magnetic particles are important in drug transport. In techniques like ferrography, nuclear magnetic resonance imaging (NMRI), spectroscopic studies and magnetic resonance imaging (MRI) the magnetic particles serve as contrast agents and give clinically important spatial resolution. Magnetic particles also find extensive applications in cancer therapy, genetic engineering, pneumology, nuclear medicine, radiology and many other fields. This article reviews these applications. (author)
Energy Technology Data Exchange (ETDEWEB)
Grigor’eva, N. A., E-mail: natali@lns.pnpi.spb.ru [St. Petersburg State University (Russian Federation); Eckerlebe, H. [Helmholtz-Zentrum Geesthacht (Germany); Eliseev, A. A.; Lukashin, A. V.; Napol’skii, K. S. [Moscow State University (Russian Federation); Kraje, M. [Reactor Institute Delft (Netherlands); Grigor’ev, S. V. [St. Petersburg State University (Russian Federation)
2017-03-15
The structural and magnetic properties of the mesoporous systems based on silicon dioxide with a regular hexagonal arrangement of pores several microns in length and several nanometers in diameter, which are filled with iron compound nanofilaments in various chemical states, are studied in detail. The studies are performed using the following mutually complementary methods: transmission electron microscopy, SQUID magnetometry, electron spin resonance, Mössbauer spectroscopy, polarized neutron small-angle diffraction, and synchrotron radiation diffraction. It is shown that the iron nanoparticles in pores are mainly in the γ phase of Fe{sub 2}O{sub 3} with a small addition of the α phase and atomic iron clusters. The effective magnetic field acting on a nanofilament from other nanofilaments is 11 mT and has a dipole nature, the ferromagnetic–paramagnetic transition temperature is in the range 76–94 K depending on the annealing temperature of the samples, and the temperature that corresponds to the change in the magnetic state of the iron oxide nanofilaments is T ≈ 50–60 K at H = 0 and T ≈ 80 K at H = 300 mT. It is also shown that the magnetization reversal of an array of nanofilaments is caused by the magnetostatic interaction between nanofilaments at the fields that are lower than the saturation field.
Faraday rotation due to excitation of magnetoplasmons in graphene microribbons.
Tymchenko, Mykhailo; Nikitin, Alexey Yu; Martín-Moreno, Luis
2013-11-26
A single graphene sheet, when subjected to a perpendicular static magnetic field, provides a Faraday rotation that, per atomic layer, greatly surpasses that of any other known material. In continuous graphene, Faraday rotation originates from the cyclotron resonance of massless carriers, which allows dynamical tuning through either external electrostatic or magneto-static setting. Furthermore, the rotation direction can be controlled by changing the sign of the carriers in graphene, which can be done by means of an external electric field. However, despite these tuning possibilities, the requirement of large magnetic fields hinders the application of the Faraday effect in real devices, especially for frequencies higher than a few terahertz. In this work we demonstrate that large Faraday rotation can be achieved in arrays of graphene microribbons, through the excitation of the magnetoplasmons of individual ribbons, at larger frequencies than those dictated by the cyclotron resonance. In this way, for a given magnetic field and chemical potential, structuring graphene periodically can produce large Faraday rotation at larger frequencies than what would occur in a continuous graphene sheet. Alternatively, at a given frequency, graphene ribbons produce large Faraday rotation at much smaller magnetic fields than in continuous graphene.
Babinec, Peter; Krafcík, Andrej; Babincová, Melánia; Rosenecker, Joseph
2010-08-01
Magnetic nanoparticles for therapy and diagnosis are at the leading edge of the rapidly developing field of bionanotechnology. In this study, we have theoretically studied motion of magnetic nano- as well as micro-particles in the field of cylindrical Halbach array of permanent magnets. Magnetic flux density was modeled as magnetostatic problem by finite element method and particle motion was described using system of ordinary differential equations--Newton law. Computations were done for nanoparticles Nanomag-D with radius 65 nm, which are often used in magnetic drug targeting, as well as microparticles DynaBeads-M280 with radius 1.4 microm, which can be used for magnetic separation. Analyzing snapshots of trajectories of hundred magnetite particles of each size in the water as well as in the air, we have found that optimally designed magnetic circuits of permanent magnets in quadrupolar Halbach array have substantially shorter capture time than simple blocks of permanent magnets commonly used in experiments, therefore, such a Halbach array may be useful as a potential source of magnetic field for magnetic separation and targeting of magnetic nanoparticles as well as microparticles for delivery of drugs, genes, and cells in various biomedical applications.
International Nuclear Information System (INIS)
Priest, E.R.
1982-01-01
Solar MHD is an important tool for understanding many solar phenomena. It also plays a crucial role in explaining the behaviour of more general cosmical magnetic fields and plasmas, since the Sun provides a natural laboratory in which such behaviour may be studied. While terrestrial experiments are invaluable in demonstrating general plasma properties, conclusions from them cannot be applied uncritically to solar plasmas and have in the past given rise to misconceptions about solar magnetic field behaviour. Important differences between a laboratory plasma on Earth and the Sun include the nature of boundary conditions, the energy balance, the effect of gravity and the size of the magnetic Reynolds number (generally of order unity on the Earth and very much larger on the Sun). The overall structure of the book is as follows. It begins with two introductory chapters on solar observations and the MHD equations. Then the fundamentals of MHD are developed in chapters on magnetostatics, waves, shocks, and instabilities. Finally, the theory is applied to the solar phenomena of atmospheric heating, sunspots, dynamos, flares, prominences, and the solar wind. (Auth.)
Ferromagnetic resonance in low interacting permalloy nanowire arrays
Energy Technology Data Exchange (ETDEWEB)
Raposo, V.; Zazo, M.; Flores, A. G.; Iñiguez, J. [Departamento de Física Aplicada, University of Salamanca, E-37071 Salamanca (Spain); Garcia, J.; Vega, V.; Prida, V. M. [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain)
2016-04-14
Dipolar interactions on magnetic nanowire arrays have been investigated by various techniques. One of the most powerful techniques is the ferromagnetic resonance spectroscopy, because the resonance field depends directly on the anisotropy field strength and its frequency dependence. In order to evaluate the influence of magnetostatic dipolar interactions among ferromagnetic nanowire arrays, several densely packed hexagonal arrays of NiFe nanowires have been prepared by electrochemical deposition filling self-ordered nanopores of alumina membranes with different pore sizes but keeping the same interpore distance. Nanowires’ diameter was changed from 90 to 160 nm, while the lattice parameter was fixed to 300 nm, which was achieved by carefully reducing the pore diameter by means of Atomic Layer Deposition of conformal Al{sub 2}O{sub 3} layers on the nanoporous alumina templates. Field and frequency dependence of ferromagnetic resonance have been studied in order to obtain the dispersion diagram which gives information about anisotropy, damping factor, and gyromagnetic ratio. The relationship between resonance frequency and magnetic field can be explained by the roles played by the shape anisotropy and dipolar interactions among the ferromagnetic nanowires.
Arabi, Eyad A.
2015-01-01
Tunable filters that are based on ferrite materials often require large and bulky electromagnets. In this work, we present a tunable filter in the Ku-band, which is realized in multilayer ferrite LTCC substrate with embedded bias windings, thus negating the need of a large electromagnet. Also, because of the embedded windings, the bias fields are not lost at the air-substrate interface and therefore the field and current requirements are reduced by an order of magnitude as compared to the previously reported filters. A simulation strategy that uses full permeability tensor with arbitrarily directed magnetic fields has been used to model the filter on a partially magnetized ferrite substrate. Special attention has also been paid to approximate the non-uniform magneto-static fields produced by the embedded windings. The complete design is implemented in 10 layers of ferrite LTCC, making it the first magnetically tunable filter with embedded windings and extremely small size [(5 × 5 × 1.1)mm3]. The filter demonstrates a measured tunability of 4% and an insertion loss of 2.3 dB. With the small form factor, embedded windings, and low bias requirements, the design is highly suitable for compact and tunable SoP applications.
Particle modeling of plasmas computational plasma physics
International Nuclear Information System (INIS)
Dawson, J.M.
1991-01-01
Recently, through the development of supercomputers, a powerful new method for exploring plasmas has emerged; it is computer modeling of plasmas. Such modeling can duplicate many of the complex processes that go on in a plasma and allow scientists to understand what the important processes are. It helps scientists gain an intuition about this complex state of matter. It allows scientists and engineers to explore new ideas on how to use plasma before building costly experiments; it allows them to determine if they are on the right track. It can duplicate the operation of devices and thus reduce the need to build complex and expensive devices for research and development. This is an exciting new endeavor that is in its infancy, but which can play an important role in the scientific and technological competitiveness of the US. There are a wide range of plasma models that are in use. There are particle models, fluid models, hybrid particle fluid models. These can come in many forms, such as explicit models, implicit models, reduced dimensional models, electrostatic models, magnetostatic models, electromagnetic models, and almost an endless variety of other models. Here the author will only discuss particle models. He will give a few examples of the use of such models; these will be taken from work done by the Plasma Modeling Group at UCLA because he is most familiar with work. However, it only gives a small view of the wide range of work being done around the US, or for that matter around the world
Energy Technology Data Exchange (ETDEWEB)
Menushenkov, V.P., E-mail: menushenkov@gmail.com; Gorshenkov, M.V.; Shchetinin, I.V.; Savchenko, A.G.; Savchenko, E.S.; Zhukov, D.G.
2015-09-15
Fe{sub 2}NiAl-based alloy with the nominal composition Fe{sub 51.1}Ni{sub 23.5}Al{sub 23.7}Si{sub 1.7} was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500–900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β{sub 2} phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force H{sub c}~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β{sub 2} phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at T{sub ag}>700 °C that decreases H{sub c}≤350 Oe. The dependence δ{sub M}(H) was measured and negative values of δ{sub M}(H) in the H=0–2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β′- and β{sub 2}′ type phases were formed after aging the ribbons at T{sub ag}>500 °C. At T{sub ag}>700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β{sub 2} phases develops by the coalescence of the primary DP products that
Electrodynamics of Magnetoactive Media
International Nuclear Information System (INIS)
Browning, P K
2004-01-01
'Electrodynamics of Magnetoactive Media' is an unusual book in that it cuts across conventional physics discipline boundaries. The unifying theme allowing this is, quite simply, the physics of magnetic fields in various media. I believe the authors are correct in stating that the book is unique in specifically covering electrodynamic phenomena associated with magnetic fields, though of course some of the more elementary aspects are covered in the classical textbooks on electromagnetism, which are duly acknowledged. This interdisciplinarity makes the book very interesting to people with a range of backgrounds. For example, as a plasma physicist, I was familiar with most of the material on plasmas, but liquid crystals and superconductors were entirely new territory for me. These chapters were indeed both accessible and interesting, and it was surprising for me to see how much commonality there is in the physics of these various media. The first part of the book covers some fundamentals of electrodynamics and magnetostatics, and of electromagnetic waves. Most of this material is covered in textbooks on electromagnetism, and some of it is very basic (for example, LRC circuit theory, surely covered in most first year physics courses, is included) but it is perhaps a useful prelude for what is to come. The generic topic of charged particle motion in electromagnetic fields is well covered. Three main magnetoactive media are then discussed: plasmas (focusing on waves), liquid crystals and superconductors. It is all too easy to criticise a book on the grounds of omitted material, but I do feel that a chapter on magnetostatics in plasmas would have been very helpful, covering force-free fields and so on. Some interesting analogies could then have been exploited. For example, I was intrigued to discover an equation for magnetic fields in superconductors (equation (9.36)) which, apart from a change of sign, is identical to the Helmholtz equation used to model linear force
International Nuclear Information System (INIS)
Menushenkov, V.P.; Gorshenkov, M.V.; Shchetinin, I.V.; Savchenko, A.G.; Savchenko, E.S.; Zhukov, D.G.
2015-01-01
Fe 2 NiAl-based alloy with the nominal composition Fe 51.1 Ni 23.5 Al 23.7 Si 1.7 was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500–900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β 2 phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force H c ~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β 2 phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at T ag >700 °C that decreases H c ≤350 Oe. The dependence δ M (H) was measured and negative values of δ M (H) in the H=0–2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β′- and β 2 ′ type phases were formed after aging the ribbons at T ag >500 °C. At T ag >700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β 2 phases develops by the coalescence of the primary DP products that decrease H c ≤250 Oe. MFM image of the magnetic structure
Three-dimensional magnetic engineering: The programs magnus and epilog
Fan, Mingwu; Pissanetzky, Sergio
1988-10-01
We present the post-processor EPILOG for the well established finite element program MAGNUS for three-dimensional magnetic engineering. MAGNUS solves problems of magnetostatics with nonlinear magnetic materials, permanent magnets and electric currents, for any 3-D geometry. The two-scalar-potentials formulation of magnetostatics used by MAGNUS combines numerical accuracy and computational efficiency, and is considered state of the art. The well known program KUBIK is used as a pre-processor to describe the geometry and finite element mesh. KUBIK is highly interactive and allows the user to effectively control all geometric details. The needs of magnetic engineers, however, go far beyond the simple availability of a mathematical solution. Once the solution has been obtained by MAGNUS in the form of a continuous magnetic scalar potential function defined at every point in the solution domain, those needs are met by EPILOG. EPILOG is command operated. Commands are independent of each other and can be used in any order, or not used at all. The purpose of each command is to use the solution for the calculation of a derived quantity or the production of a plot or table. The following derived quantities can be obtained: the magnetic energy in specific regions, the magnetic force on specified conductors in space, the magnetic torque on specified conductors, the magnetic flux across a given surface in space, the inductance of a circuit, and a variety of line integrals for specified lines in space. A useful facility is the automatic calculation of harmonic multipoles averaged along the beam direction for accelerator magnets, essential for end analysis and the integral effect of the magnetic field on the beam. Graphical facilities include color plots of the shapes of the conductors, the geometry, field lines and surfaces of constant magnetic scalar potential in specified regions of space. EPILOG produces a device independent graphical metafile, which can be seen on any device
High density plasmas and new diagnostics: An overview (invited)
International Nuclear Information System (INIS)
Celona, L.; Gammino, S.; Mascali, D.
2016-01-01
One of the limiting factors for the full understanding of Electron Cyclotron Resonance Ion Sources (ECRISs) fundamental mechanisms consists of few types of diagnostic tools so far available for such compact machines. Microwave-to-plasma coupling optimisation, new methods of density overboost provided by plasma wave generation, and magnetostatic field tailoring for generating a proper electron energy distribution function, suitable for optimal ion beams formation, require diagnostic tools spanning across the entire electromagnetic spectrum from microwave interferometry to X-ray spectroscopy; these methods are going to be implemented including high resolution and spatially resolved X-ray spectroscopy made by quasi-optical methods (pin-hole cameras). The ion confinement optimisation also requires a complete control of cold electrons displacement, which can be performed by optical emission spectroscopy. Several diagnostic tools have been recently developed at INFN-LNS, including “volume-integrated” X-ray spectroscopy in low energy domain (2-30 keV, by using silicon drift detectors) or high energy regime (>30 keV, by using high purity germanium detectors). For the direct detection of the spatially resolved spectral distribution of X-rays produced by the electronic motion, a “pin-hole camera” has been developed also taking profit from previous experiences in the ECRIS field. The paper will give an overview of INFN-LNS strategy in terms of new microwave-to-plasma coupling schemes and advanced diagnostics supporting the design of new ion sources and for optimizing the performances of the existing ones, with the goal of a microwave-absorption oriented design of future machines
3-Dimensional Modeling of Capacitively and Inductively Coupled Plasma Etching Systems
Rauf, Shahid
2008-10-01
Low temperature plasmas are widely used for thin film etching during micro and nano-electronic device fabrication. Fluid and hybrid plasma models were developed 15-20 years ago to understand the fundamentals of these plasmas and plasma etching. These models have significantly evolved since then, and are now a major tool used for new plasma hardware design and problem resolution. Plasma etching is a complex physical phenomenon, where inter-coupled plasma, electromagnetic, fluid dynamics, and thermal effects all have a major influence. The next frontier in the evolution of fluid-based plasma models is where these models are able to self-consistently treat the inter-coupling of plasma physics with fluid dynamics, electromagnetics, heat transfer and magnetostatics. We describe one such model in this paper and illustrate its use in solving engineering problems of interest for next generation plasma etcher design. Our 3-dimensional plasma model includes the full set of Maxwell equations, transport equations for all charged and neutral species in the plasma, the Navier-Stokes equation for fluid flow, and Kirchhoff's equations for the lumped external circuit. This model also includes Monte Carlo based kinetic models for secondary electrons and stochastic heating, and can take account of plasma chemistry. This modeling formalism allows us to self-consistently treat the dynamics in commercial inductively and capacitively coupled plasma etching reactors with realistic plasma chemistries, magnetic fields, and reactor geometries. We are also able to investigate the influence of the distributed electromagnetic circuit at very high frequencies (VHF) on the plasma dynamics. The model is used to assess the impact of azimuthal asymmetries in plasma reactor design (e.g., off-center pump, 3D magnetic field, slit valve, flow restrictor) on plasma characteristics at frequencies from 2 -- 180 MHz. With Jason Kenney, Ankur Agarwal, Ajit Balakrishna, Kallol Bera, and Ken Collins.
Fabrication and magnetic investigations of highly uniform CoNiGa alloy nanowires
Energy Technology Data Exchange (ETDEWEB)
Li, Wen-Jing; Khan, U.; Irfan, Muhammad [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190 (China); Javed, K. [Department of Physics, Forman Christian College, Lahore 5400 (Pakistan); Liu, P. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190 (China); School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021 (China); Ban, S.L. [School of Physical Science and Technology, Inner Mongolia University, Hohhot 010021 (China); Han, X.F., E-mail: xfhan@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190 (China)
2017-06-15
Highlights: • Highly ordered CoNiGa alloy nanowires with different compositions were fabricated by DC electrodeposition. • The magnetic properties of CoNiGa nanowires can be easily tailored by varying its components. • Magnetostatic interactions plays an important role in the magnetization reversal process. • A linear dependence of coercivity on temperature was found for Co{sub 55}Ni{sub 28}Ga{sub 17} samples. - Abstract: CoNiGa ternary alloy nanowire arrays were successfully fabricated by simple DC electrodeposition into the anodized aluminum oxide (AAO) templates. A systematic study of the potential and components of the electrolyte were conducted to obtain different components of CoNiGa nanowires. The largest Ga content in the prepared alloy nanowires was about 17%, while for Co and Ni contents which can be controlled in a wide range by adjusting the composition and pH value of the electrolyte appropriately. X-ray diffraction analysis confirmed that the as-grown CoNiGa nanowire arrays were polycrystal with fcc phase of Co where Co atoms partially substituted by Ni and Ga. Magnetization curves of samples with different composition were measured at room temperature as well as low temperature. The results showed that the components of the alloy nanowires have a great impact on its magnetic properties. For Co{sub 55}Ni{sub 28}Ga{sub 17} nanowires, the magnetization reversal mode changes from curling mode to coherent rotation as the angle increases, and the temperature dependence of coercivity can be well described by the thermal activation effect.
Laser induced local modification of magnetic domain in Co/Pt multilayer
International Nuclear Information System (INIS)
Talapatra, A.; Mohanty, J.
2016-01-01
Manipulation of magnetic system by the use of laser has drawn the attention of contemporary research. We demonstrate here the modification of magnetic domain in perpendicularly magnetized Co/Pt multilayer by using ultrashort laser pulse. The as-prepared sample shows an out-of-plane saturation magnetic field of 803.4 mT and almost zero remanence with a labyrinth-like domain pattern at room temperature. Atomistic simulation showed that interaction with femto-second laser results in demagnetization of the material in 200 fs followed by a slower recovery. As it indicates a net loss in magnetization, so magnetic force microscopy is carried out to investigate the equilibrium state after the system is relaxed. Demagnetized random domains appeared at the centre of the laser spot with having a rim at the boundary which signifies a deterministic switching with respect to the neighbouring area. Rotation of domains at the central area with the application of small transverse field (100 mT) proves the region to be magnetically weaker. Systematic 3D micromagnetic simulation has been performed to model the laser induced change by selective reduction of anisotropy which is discussed in detail. This shows shrinking of domains to a near circular pattern to minimize the magnetostatic energy. 50% reduction in anisotropy energy is observed with increasing the total energy of the system and a sharp increase in demagnetization energy also takes place simultaneously. This also satisfies the anisotropy in domain rotation with the application of transverse field. - Highlights: • Laser induced magnetization dynamics. • Local manipulation of magnetic domains. • Deterministic switching of domains with laser. • Modeling magnetic domain structure with local anisotropy distribution.
X-ray detected magnetic resonance of YIG thin films in the nonlinear regime of spin waves
Energy Technology Data Exchange (ETDEWEB)
Goulon, J., E-mail: goulon@esrf.f [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Rogalev, A.; Wilhelm, F.; Goujon, G. [European Synchrotron Radiation Facility (ESRF), B.P. 220, F-38043 Grenoble Cedex (France); Brouder, Ch. [Institut de Mineralogie et de Physique des Milieux Condenses, UMR-CNRS 7590, Universite Paris VI-VII, 4 place Jussieu, F-75252 Paris Cedex 05 (France); Yaresko, A. [Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart (Germany); Ben Youssef, J.; Indenbom, M.V. [Laboratoire de Magnetisme de Bretagne, CNRS FRE 2697, UFR Sciences et Techniques, F-29328 Brest Cedex (France)
2010-08-15
We discuss the information content of element/edge resolved X-ray detected magnetic resonance (XDMR) experiments carried out on yttrium iron garnet (YIG) thin films. Starting with a phenomenological approach, it is shown that the photoionisation of deep atomic core levels by circularly polarized X-rays can be used to probe the precession dynamics of spin or orbital magnetization components in empty final states of proper symmetry. Crude estimates of the opening angle of the uniform precession mode were tentatively deduced from the ratio of the XDMR and XMCD absorption cross-sections either at the iron or yttrium absorbing sites. The implications of the most recent experimental results collected at the ESRF are analyzed, keeping in mind that: (i) the Fe K-edge XDMR signal is largely dominated by the precession of orbital magnetization components at the tetrahedral iron sites; (ii) the Y L-edges XDMR signal essentially describes the precession of induced spin magnetization involving the 4d states of yttrium. In the magnetostatic regime, we produce clear experimental evidence of collective excitations of orbital magnetization waves, especially under high pumping power. Several coupling mechanisms could explain our observations, starting with pseudo-dipolar interactions in ferromagnetic systems. In ferrimagnetic systems in which orbital degeneracy and orbital ordering make the excitation of orbitons possible, one may envisage additional modes of excitation or relaxation of orbital magnetization waves. This interpretation looks fully consistent with the results of band structure calculations carried out recently on YIG with fully relativistic LMTO-LSDA methods.
Radiation tolerance of a spin-dependent tunnelling magnetometer for space applications
International Nuclear Information System (INIS)
Persson, Anders; Thornell, Greger; Nguyen, Hugo
2011-01-01
To meet the increasing demand for miniaturized space instruments, efforts have been made to miniaturize traditional magnetometers, e.g. fluxgate and spin-exchange relaxation-free magnetometers. These have, for different reasons, turned out to be difficult. New technologies are needed, and promising in this respect are tunnelling magnetoresistive (TMR) magnetometers, which are based on thin film technology. However, all new space devices first have to be qualified, particularly in terms of radiation resistance. A study on TMR magnetometers' vulnerability to radiation is crucial, considering the fact that they employ a dielectric barrier, which can be susceptible to charge trapping from ionizing radiation. Here, a TMR-based magnetometer, called the spin-dependent tunnelling magnetometer (SDTM), is presented. A magnetometer chip consisting of three Wheatstone bridges, with an angular pitch of 120°, was fabricated using microstructure technology. Each branch of the Wheatstone bridges consists of eight pairs of magnetic tunnel junctions (MTJs) connected in series. Two such chips are used to measure the three-dimensional magnetic field vector. To investigate the SDTM's resistance to radiation, one branch of a Wheatstone bridge was irradiated with gamma rays from a Co 60 source with a dose rate of 10.9 rad min −1 to a total dose of 100 krad. The TMR of the branch was monitored in situ, and the easy axis TMR loop and low-frequency noise characteristics of a single MTJ were acquired before and after irradiation with the total dose. It was concluded that radiation did not influence the MTJs in any noticeable way in terms of the TMR ratio, coercivity, magnetostatic coupling or low-frequency noise
International Nuclear Information System (INIS)
Sauter, O.
1992-05-01
Heating of tokamak plasmas up to temperatures of the order of 10 keV (∼10 8 o K) is one of the main subjects in plasma physics research. Much experimental and theoretical effort has been devoted to the improvement of the heating efficiency and to the understanding of the beam-particle or wave-particle interactions. We have studied the latter subject. In present day experiments, the temperature of the particles is very high. Increasing numbers of experiments use heating scenarii at high harmonic frequencies. Because these cases can no longer be studied using a local model, we have developed a 'nonlocal' model which is not limited by the size of the Larmor radii nor by the harmonic considered. This model is based on the global wave approach and therefore can treat a variety of problems. Nevertheless, we have limited our work to uni-dimensional geometry, Maxwellian equilibrium distribution functions and slowly-varying equilibrium magnetic field. We have also neglected k y in the conductivity tensor, where y is the direction normal to the direction of the inhomogeneity and to the magnetostatic field. Starting from the linearized Vlasov-Maxwell equations, we have derived the equations in the Fourier and the configuration spaces. We have also derived a formulation of the local power absorption allowing us to determine the profile of absorption of the wave by the particles. The equations are solved numerically using the finite element method. We have developed two codes, SEAL and SEMAL, which calculate the wave field in the electrostatic and electromagnetic cases, respectively. These codes have been tested. We have shown that the local model was inadequate and have studied in more detail the effect of temperature and the strong influence of the alpha particle concentration. (author) figs., tabs., 91 refs
Investigation of the Dynamics of Magnetic Vortices and Antivortices Using Micromagnetic Simulations
Asmat-Uceda, Martin Antonio
This thesis is focused on investigating the dynamic properties of spin textures in patterned magnetic structures by using micromagnetic simulations. These textures become particularly relevant at sub-micron length scales where the interplay between magnetostatic and exchange energy leads to unique properties that are of great interest both from a fundamental perspective and for the development of new technologies. Two different systems, a magnetic antivortex (AV) stabilized in the intersection of perpendicular microwires, and three interacting vortices in an equilateral arrangement, were considered for this study. For the first system, the AV, the formation process and the excitation spectra were investigated. Since the AV is a metastable state, the design of a host structure capable of stabilizing it requires careful consideration and it is desirable to have general guidelines that could help to optimize the AV formation rate. The role of the shape anisotropy and the field dependence of the AV formation process is discussed in detail. Micromagnetic simulations along with magneto-optical Kerr effect and magnetic force microscopy measurements demonstrated that the asymmetry in the structure can be used to promote the formation of such AV's and that regions with lower shape anisotropy lead the reversal process, while simulations of the dynamic response show that when the system is excited with in-plane and out-of-plane external magnetic fields, normal modes with azimuthal and radial characteristics are found, respectively, in addition to the low frequency gyrotropic mode. The modes are influenced by the spin texture in the intersection, which offers additional possibilities for manipulating spin waves (SW). For the second system, three interacting vortices are simulated and compared with a simple analytical model that considers only dipolar interactions. It was found that when a fitting parameter is introduced to the model, the main features of the simulations are
International Nuclear Information System (INIS)
Yazdani-Asrami, Mohammad; Mirzaie, Mohammad; Shayegani Akmal, Amir Abbas
2013-01-01
Transformers are basically designed to operate under nominal voltage, rated frequency and also, pure sinusoidal load current. In recent decade, change in the type of loads and increasing use of power electronic devices with their nonsinusoidal current waveform has distorted the system voltage waveform as well. The losses of transformers include load and no-load losses. No-load loss continuously led to loss of energy in transformers that are connected to the network in all 24 h. With respect to high significance of energy and undesirable impacts of losses on the aging of transformers, the no-load loss is considered as a critical factor. Nowadays, it is necessary to apply a suitable method for calculation of no-load loss in presence of the voltage harmonics and over-excite conditions, especially for distribution transformers, as a result of harmonic increase in the voltage and current in the network and particular applications. In this paper, Finite Element Method (FEM) has been used to simulate nonsinusoidal voltage effects on no-load loss of transformers. Such simulation enables the software to simulate and analyze different electromagnetic parameters such as flux lines, flux density, losses, and etc under different input sources and with high accuracy. In addition, effect of nonsinusoidal voltages on no-load loss has been investigated by a typical experimental transformer using several practical tests. - Highlights: ► FEM has been employed to loss calculation of distribution transformer under distorted voltages. ► This method gives accurate results in comparison with standard or circuit based methods. ► A new version of 3D FEM has been used, this approach is electromagnetic based. ► In literature, FEM always used for study of transformer load loss and most of them based on magneto-static FEM. ► FEM results are validated by experiment for small test transformer
A Critical Appraisal of the "Day" Diagram
Roberts, Andrew P.; Tauxe, Lisa; Heslop, David; Zhao, Xiang; Jiang, Zhaoxia
2018-04-01
The "Day" diagram (Day et al., 1977, https://doi.org/10.1016/0031-9201(77)90108-X) is used widely to make inferences about the domain state of magnetic mineral assemblages. Based on theoretical and empirical arguments, the Day diagram is demarcated into stable "single domain" (SD), "pseudo single domain" ("PSD"), and "multidomain" (MD) zones. It is straightforward to make the necessary measurements for a sample and to plot results within the "domain state" framework based on the boundaries defined by Day et al. (1977, https://doi.org/10.1016/0031-9201(77)90108-X). We discuss 10 issues that limit Day diagram interpretation, including (1) magnetic mineralogy, (2) the associated magnetocrystalline anisotropy type, (3) mineral stoichiometry, (4) stress state, (5) surface oxidation, (6) magnetostatic interactions, (7) particle shape, (8) thermal relaxation, (9) magnetic particle mixtures, and (10) definitional/measurement issues. In most studies, these variables are unknowns and cannot be controlled for, so that hysteresis parameters for single bulk samples are nonunique and any data point in a Day diagram could result from infinite combinations of relevant variables. From this critical appraisal, we argue that the Day diagram is fundamentally ambiguous for domain state diagnosis. Widespread use of the Day diagram has also contributed significantly to prevalent but questionable views, including underrecognition of the importance of stable SD particles in the geological record and reinforcement of the unhelpful PSD concept and of its geological importance. Adoption of approaches that enable correct domain state diagnosis should be an urgent priority for component-specific understanding of magnetic mineral assemblages and for quantitative rock magnetic interpretation.
Microwave magnetoelectric fields: An analytical study of topological characteristics
Energy Technology Data Exchange (ETDEWEB)
Joffe, R., E-mail: ioffr1@gmail.com [Microwave Magnetic Laboratory, Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer Sheva (Israel); Department of Electrical and Electronics Engineering, Shamoon College of Engineering, Beer Sheva (Israel); Shavit, R.; Kamenetskii, E.O. [Microwave Magnetic Laboratory, Department of Electrical and Computer Engineering, Ben Gurion University of the Negev, Beer Sheva (Israel)
2015-10-15
The near fields originated from a small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillations are the fields with broken dual (electric-magnetic) symmetry. Numerical studies show that such fields – called the magnetoelectric (ME) fields – are distinguished by the power-flow vortices and helicity parameters (E.O. Kamenetskii, R. Joffe, R. Shavit, Phys. Rev. E 87 (2013) 023201). These numerical studies can well explain recent experimental results with MDM ferrite disks. In the present paper, we obtain analytically topological characteristics of the ME-field modes. For this purpose, we used a method of successive approximations. In the second approximation we take into account the influence of the edge regions of an open ferrite disk, which are excluded in the first-approximation solving of the magnetostatic (MS) spectral problem. Based on the analytical method, we obtain a “pure” structure of the electric and magnetic fields outside the MDM ferrite disk. The analytical studies can display some fundamental features that are non-observable in the numerical results. While in numerical investigations, one cannot separate the ME fields from the external electromagnetic (EM) radiation, the present theoretical analysis allows clearly distinguish the eigen topological structure of the ME fields. Importantly, this ME-field structure gives evidence for certain phenomena that can be related to the Tellegen and bianisotropic coupling effects. We discuss the question whether the MDM ferrite disk can exhibit properties of the cross magnetoelectric polarizabilities. - Highlights: • We obtain analytically topological characteristics of the ME-field modes. • We take into account the influence of the edge regions of an open ferrite disk. • We obtain a “pure” structure of the electromagnetic fields outside the ferrite disk. • Analytical studies show features that are non-observable in the numerical results. • ME-field gives evidence for
Microwave magnetoelectric fields: An analytical study of topological characteristics
International Nuclear Information System (INIS)
Joffe, R.; Shavit, R.; Kamenetskii, E.O.
2015-01-01
The near fields originated from a small quasi-two-dimensional ferrite disk with magnetic-dipolar-mode (MDM) oscillations are the fields with broken dual (electric-magnetic) symmetry. Numerical studies show that such fields – called the magnetoelectric (ME) fields – are distinguished by the power-flow vortices and helicity parameters (E.O. Kamenetskii, R. Joffe, R. Shavit, Phys. Rev. E 87 (2013) 023201). These numerical studies can well explain recent experimental results with MDM ferrite disks. In the present paper, we obtain analytically topological characteristics of the ME-field modes. For this purpose, we used a method of successive approximations. In the second approximation we take into account the influence of the edge regions of an open ferrite disk, which are excluded in the first-approximation solving of the magnetostatic (MS) spectral problem. Based on the analytical method, we obtain a “pure” structure of the electric and magnetic fields outside the MDM ferrite disk. The analytical studies can display some fundamental features that are non-observable in the numerical results. While in numerical investigations, one cannot separate the ME fields from the external electromagnetic (EM) radiation, the present theoretical analysis allows clearly distinguish the eigen topological structure of the ME fields. Importantly, this ME-field structure gives evidence for certain phenomena that can be related to the Tellegen and bianisotropic coupling effects. We discuss the question whether the MDM ferrite disk can exhibit properties of the cross magnetoelectric polarizabilities. - Highlights: • We obtain analytically topological characteristics of the ME-field modes. • We take into account the influence of the edge regions of an open ferrite disk. • We obtain a “pure” structure of the electromagnetic fields outside the ferrite disk. • Analytical studies show features that are non-observable in the numerical results. • ME-field gives evidence for
Microwave permeability of stripe patterned FeCoN thin film
Energy Technology Data Exchange (ETDEWEB)
Wu, Yuping [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Yang, Yong, E-mail: tslyayo@nus.edu.sg [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Ma, Fusheng; Zong, Baoyu; Yang, Zhihong [Temasek Laboratories, National University of Singapore, 5A Engineering Drive 1, Singapore 117411 (Singapore); Ding, Jun [Department of Materials Science and Engineering, National University of Singapore, Singapore 117574 (Singapore)
2017-03-15
Magnetic stripe patterns are of great importance for microwave applications owing to their highly tunable microwave permeability by adjusting the geometrical dimensions. In this work, stripe patterned FeCoN films with 160 nm thickness are fabricated by using standard UV photolithography. Their microwave permeability are investigated systematically via both experiment and micromagnetic simulation. The good agreement between experimental and simulation results suggests that stripe width is crucial for the microwave magnetic properties of the stripe pattern. It is demonstrated by simulation that with increasing stripe width from 1 to 80 µm the initial permeability shows a continuous growth from about 8–322, whiles the resonance frequency drops dramatically from 18.7 to 3.1 GHz at 4 µm gap size. Smaller gap size would result in slightly increased initial permeability due to larger magnetic volume ratio, accompanied by decreased resonance frequency because of stronger magnetostatic interaction. Moreover, the experimental investigation on stripe length effect indicates that the stripe length should be kept as long as possible to achieve uniform bulk resonance mode and high permeability value. Insufficient stripe length would result in low frequency edge mode and decayed bulk mode. This study could provide valuable guidelines on the selection of proper geometry dimensions of FeCoN stripe patterns for high frequency applications. - Highlights: • This work presents a systematic study on permeability of FeCoN stripe pattern. • Geometrical parameters of the stripe pattern are systematically optimized. • Several important conclusions has been obtained. • The results offer guideline on FeCoN stripe patterns for high frequency applications.
EGUN, Charged Particle Trajectories in Electromagnetic Focusing System
International Nuclear Information System (INIS)
Herrmannsfeldt, W.B.
2002-01-01
1 - Description of problem or function: EGUN computes trajectories of charged particles in electrostatic and magnetostatic focusing systems including the effects of space charge and self-magnetic fields. Starting options include Child's Law conditions on cathodes of various shapes, user-specified conditions input for each ray, and a combination of Child's Law conditions and user specifications. Either rectangular or cylindrically symmetric geometry may be used. Magnetic fields may be specified using an arbitrary configuration of coils, or the output of a magnet program, such as Poisson, or by an externally calculated array of the axial fields. 2 - Method of solution: The program first solves Laplace's equation. Next, the first iteration of electron trajectories is started using one of the four starting options. On the first iteration cycle, space charge forces are calculated from the assumption of paraxial flow. As the rays are traced, space charge is computed and stored. After all the electron trajectories have been calculated, the program begins the second cycle by solving the Poisson equation with the space charge from the first iteration. Subsequent iteration cycles follow this pattern. The Poisson equation is solved by an alternate column relaxation technique known as the semi-iterative Chebyshev method. A fourth-order Runge-Kutta method is used to solve the relativistic differential equations of the trajectory calculations. 3 - Restrictions on the complexity of the problem - Maxima of: 9001 mesh points in a square mesh, 300 mesh points in the axial direction, 100 mesh points in the radial direction, 101 potentials, 51 rays. In the cylindrical coordinates, the magnetic fields are axially symmetric. In rectangular coordinates, the external field is assumed to be normal to the plane of the problem, which is assumed to be the median plane
Phase separation and exchange bias effect in Ca doped EuCrO{sub 3}
Energy Technology Data Exchange (ETDEWEB)
Deng, Dongmei, E-mail: dmdeng@shu.edu.cn [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Wang, Xingyu; Zheng, Jiashun; Qian, Xiaolong [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Yu, Dehong; Sun, Dehui [Bragg Institute, Australian Nuclear Science and Technology Organization, Kirrawee DC, NSW 2232 (Australia); Jing, Chao [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China); Lu, Bo [Analysis and Measurement Center and Laboratory for Microstructures of Shanghai University, Shanghai 200444 (China); Kang, Baojuan; Cao, Shixun; Zhang, Jincang [Department of Physics and Materials Genome Institute, Shanghai University, Shanghai 200444 (China)
2015-12-01
The rare-earth chromites have attracted increasing interests in recent years, as a member of a few single-phase multiferroic materials. We studied the structure and magnetic property of a series of Ca-doped EuCrO{sub 3} samples by using X-ray powder diffraction and Physical Property Measurement System. Phase separation, rotation of magnetization in M(T) curve and exchange bias effect have been identified. The Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3} polycrystalline sample may be intrinsically phase-separated, with Cr{sup 3+}-rich, Cr{sup 4+}-rich canted antiferromagnetic regions surrounded by spin glass-like frustrated phase, resulting in several magnetic features including: (1) a broad and slow increase of M(T) curve with the decrease of temperature; (2) rotation of magnetization with increasing cooling field; (3) exchange bias and glassy magnetism. The rotation of magnetization is ascribed to the rotation of the moment of Cr{sup 4+}-rich regions, arising from the competition between exchange coupling energy and magnetostatic energy. The exchange bias effect suggests the formation of weak ferromagnetic unidirectional anisotropy during field cooling, due to the exchange coupling among weak ferromagnetic domains and surrounding spin glass-like regions. This result helps understanding the interaction among different magnetic domains and phases in a complex system. - Highlights: • Exchange bias effect and glassy magnetism were observed in Eu{sub 0.7}Ca{sub 0.3}CrO{sub 3}. • Rotation of the moments of Cr{sup 4+}-rich regions result in the rotation of magnetization in M(T) curve. • Spin glass-like regions contribute to the observed exchange bias effect.