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Magnetics, IEEE Transactions on

Issue 5  Part 2 • Date Sept. 1999

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Displaying Results 1 - 25 of 299
  • Layer selective magnetic moment distribution in an epitaxial double spin valve structure: Si[001]/Cu

    Page(s): 3847 - 3849
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    We determine layer selectively the magnetic moments, spin orientations and thicknessess oP an epitaxial double spin valve structure, Si(00l)/Cn/FeNi/Cu/Co/Cu/FeNi/Cu, using Polarised Neutron Reflectivity (PNR). At saturation, the layer-averaged magnetic moment per CO atom was Pound to be 1.71 ± 0.08 μ, while the top (bottom) FeNi layer moment was 1.08 ± 0.06 μB (0.95 ± 0.08 μB). For an applied field strength Ha smaller than the c0 layer coercive field of ~100 Oe, the CO and FeNi layer magnetisation vectors are Pound to lie in-plane but canted with respect to each other in contrast to the fully antiparallel state predicted by simple energy minimisation. The observed canting is discussed with regard to the role of magnetic domains in the CO layer. View full abstract»

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  • Effect of strain on the magnetic anisotropy of Co in Cu/Co/Ni/Cu/Si[001] epitaxial structures

    Page(s): 3850 - 3852
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    The effect of strain on the magnetic anisotropy of epitaxial Co/Ni/Cu/Si(00l) structures was studied using polar magneto-optic Kerr effect WOKE) magnetometry and reflection high energy electron diffraction (RHEED). CO has the effect of reducing the perpendicular magnetic anisotropy of Ni for the whole range of Ni thicknesses (30 Å to 120 Å) while a variation of the perpendieular CO anisotropy constants with the Ni thickness is observed. The first and second order magnetoelastic coupling coefficients of CO were obtained from this strain-related variation, and are found to have opposite signs. We show that by varying the Ni thickness it is possible to sensitively control the magnetic anisotropy of the CO layer. View full abstract»

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  • Exchange coupling in MBE grown MnPt/NiFe bilayers

    Page(s): 3922 - 3924
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    Exchange anisotropy in MnPt(30 nm)/NiFe(5 nm) bilayers was investigated for films grown by the MBE method on MgO(001) and SrTi03(001) substrates, During the deposition, a static magnetic field of 100 Oe was applied in the film plane. In-situ reflection high-energy electron diffraction observations and ex-situ X-ray diffraction measurements revealed that the MnPt layers have chemical order and have (100) orientation which is an uncompensated plane of antiferromagnetic spin alignment. The bilayers whose MnPt layer was grown on NiFe layer were found to have an exchange anisotropy field (Hex) of 220 Oe (corresponding exchange anisotropy energy of J = 0.084 erg/cm2c) of 43 Oe, while the bilayers whose NiFe layer was grown on MnPt layer show very small Hex and a large Hc. View full abstract»

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  • Conference author index

    Page(s): 4136 - 4145
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    Freely Available from IEEE
  • Static and dynamic magnetic properties of fine CoNi and FeCoNi particles synthesized by the polyol process

    Page(s): 3469 - 3471
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    Fine CoNi and FeCoNi particles elaborated by the polyol process over a wide size range display a core shell texture. From the study of the coercivity and remanence against the particle size, the critical size below which the CoNi particles are single domains is estimated in the 20-40 nm range. The comparison between static and dynamic properties shows that exchange resonance modes are observed for nonsingle domain particles. Anisotropy constants are found to increase as the particle size decreases and as the Co content increases View full abstract»

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  • Optimization of electromagnetic devices using computational intelligence techniques

    Page(s): 3727 - 3729
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    This paper describes the use of computational intelligence techniques, in particular neuro-fuzzy systems and genetic algorithms, for modeling and optimizing electromagnetic devices with a high number of variables. A seven variable loudspeaker problem is investigated. The results obtained indicate the applicability of the various approaches View full abstract»

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  • Application of Taguchi method to robust design of BLDC motor performance

    Page(s): 3700 - 3702
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    This paper describes an approach to the design of brushless dc motors considering cogging torque reduction and running torque optimization to enhance the product robustness. The approach is based on the Taguchi method and utilizes the orthogonal array for design of `'experiments', i.e. the scheme for numerical simulations using a finite element method. The concept of signal-to-noise (S/N) ratio is applied to evaluate the motor performance. A comparison is made between the robust solution and the result obtained using a conventional optimization procedure to demonstrate the effectiveness of the robust design approach View full abstract»

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  • Consideration of contactless power station with selective excitation to moving robot

    Page(s): 3583 - 3585
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    A new method of contactless energy transmission to a moving machine is proposed. This system is useful for application with moving robots, including electric vehicles such as an electric wheelchair, an automatic guided vehicle, and so on. A moving robot was used as a model experimental system with these loads. The primary coils, an arrangement of spiral coils used with the selective excitation system, are located on the floor. A secondary spiral coil is attached to the bottom of the robot. The robot receives the magnetic flux radiating from the primary coils, which serves as the power source for the robot. In terms of electric power, in this experimental system the robot needs at least 2 W to start moving. As the robot moves, the excitation follows its movement. We have studied the characteristics of power transmission when the robot moves from one primary coil to another. This selective excitation system was found to be very effective for the overall efficiency of electric power transmission. We also examined the efficiency of the coil system used herein. Based on a comparison of the closed magnetic loop circuit and the open magnetic loop circuit, the efficiency of the former determined to be 70 [%] and that of the latter was determined to be 9 [%]. A monitoring system was constructed to ascertain which coil was excited. Based on our results, it would be possible to apply this contactless power transmission system to larger systems View full abstract»

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  • Three-dimensional measurement of induced magnetic anisotropy in plastically deformed Ni3Fe alloy

    Page(s): 3802 - 3804
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    The induced magnetic anisotropy in the plastically deformed Ni3Fe ordered alloy is studied by using the spherical specimens and is analyzed three-dimensionally. The easy direction of magnetization is consistently explained by the four slip systems which acts at the same time View full abstract»

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  • Improvements of magnetic properties of Sr ferrite magnets by substitutions of La and Co

    Page(s): 3334 - 3336
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    The effect of the simultaneous partial substitution of Co2+ for Fe3+ and of La3+ for Sr2+ ion in Sr ferrite on the magnetic properties of anisotropic Sr ferrite magnets was investigated. It was found that the coercive force of Sr ferrite magnets is increased without significant decrease in residual flux density by La-Co substitution. Temperature coefficients of coercive force were found to be also improved by La-Co substitution View full abstract»

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  • Numerical analysis of eddy current NDT for a tube with cracks using 3D indirect BIEM

    Page(s): 3724 - 3726
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    In this paper, the 3-dimensional indirect boundary integral equation method (BIEM) is applied to the numerical analysis of eddy current non-destructive testing (NDT) for a tube with cracks. The indirect BIEM is developed in terms of the equivalent surface current density and equivalent surface charge density on the interface. The existence and type of the crack in the pipe can be determined from the distortion of the magnetic charge density distribution. The impedance signal is calculated from the equivalent surface charge density without calculating the self inductance. The axisymmetric and the 90-degree circular outer crack problems are calculated as an example. The result shows the usage of the indirect BIEM in the area of eddy current NDT View full abstract»

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  • Study on the characteristics of superconducting bearing

    Page(s): 4028 - 4030
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    This paper deals with the experiments and simulations of the levitation force between permanent magnet and High Tc Superconductor (HTS), and also the simulations of the dynamic behaviors related to vibration. Levitation force is evaluated numerically on the basis of the magnetic vector potential method and the critical state model. The superconductor is approximated to 2-D axisymmetric model for the simulation View full abstract»

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  • Analysis and optimization of the magnetomechanical properties of Terfenol-D composites at audio frequencies

    Page(s): 3829 - 3831
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    The magnetic and magnetostrictive properties of polymer-bonded Terfenol-D rods, compacted from powders with different phenol binder content, are measured in static and dynamic conditions. Magnetic measurements were made up to 40 kHz using a custom made amorphous yoke. Magnetostrictive characterization was performed with prestress up to 15 Mpa in quasi-static and dynamic conditions (up to 40 Hz). A maximum deformation of about 6×10-4, producing work, can be achieved with a variable phenol content. Dynamic magnetic properties were simulated using the dynamic Preisach model, obtaining an estimate value for conductivity. The inclusion of a non-conductive phenol binder increases the mechanical strength and favors a reduction of eddy current losses, for applications at sonic or ultrasonic frequency View full abstract»

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  • Magnetic properties of CoZrNb thin films deposited on amorphous SmCo

    Page(s): 3394 - 3396
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    Amorphous CoZrNb thin films mere deposited on amorphous SmCo thin films. The amorphous SmCo layer generated magnetic bias field for the soft film, and this bias field was increased as the length of easy direction was reduced. The bias field of 60Oe was measured for the sample with the dimension 3 mm×0.5 mm. The magnetization process of the biased soft film was different from that of a single layer film View full abstract»

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  • New method for the reconstruction of the distribution of fine particle magnetic moments in a ferrofluid

    Page(s): 4064 - 4066
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    We present a new method to reconstruct the distribution of magnetic moments ρ(μ) of ferrofluid particles from the magnetization curve measured on a ferrofluid in the liquid state. The method employs the solution of the integral equation describing the magnetization of the fine particle system in an external field and requires no a priori assumptions concerning the shape of ρ(μ). Reconstruction results for both the computer simulated magnetization curves and the experimental data obtained on Co-ferrofluids are presented. In the latter case comparison of the reconstructed distribution with ρ(μ) calculated from the particle size distribution obtained via electron microscopy shows good quantitative agreement View full abstract»

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  • Injection molded Sm2Fe17N3 anisotropic magnet using reduction and diffusion method

    Page(s): 3340 - 3342
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    High performance injection molded Sm2Fe17N 3 anisotropic magnet is developed from the powder made by reduction and diffusion method. Remanence, coercivity and maximum energy product are 0.77 T, 0.78 T and 103 kT/m3, respectively in the density of 4.77 Mg/m3. The temperature coefficient of remanence is -0.07%/K. The initial irreversible flux loss is 5% at 100°C at a permanence of two View full abstract»

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  • 3-Dimensional eddy current analysis of a conducting shell of a superconducting generator by using IBIEM

    Page(s): 4091 - 4093
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    To ensure reliable operation of superconducting field windings of a superconducting generator it is necessary to screen the field windings from time-varying magnetic fields. An electrothermal shield is used for this screening in order to protect the superconducting material from quench phenomena. This screening effect is due to the eddy currents in the electrothermal shield. In this paper, these eddy currents in the conducting shell are analyzed numerically by using a 3-dimensional indirect boundary integral equation method (IBIEM) View full abstract»

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  • Atomic migration in CoGaxFe2-xO4

    Page(s): 3418 - 3420
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    Co-Ga ferrite has been studied with X-ray diffraction, vibrating sample magnetometer and Mossbauer spectroscopy. The crystal structure for this system is spinel and lattice constants is in accord with Vegard's law. The Neel temperature decreases linearly with Ga concentration suggesting the superexchange interaction Co-O-Fe link is stronger than that for the Ga-O-Fe link. Atomic migration of CoGa0.1Fe1.9O4 starts near 350 K and increases rapidly with increasing temperature to such a degree that 73% of the ferric ions as the A sites have moved to the B site by 700 K. The temperature dependence of the magnetic hyperfine field and magnetization of CoGa0.1Fe1.9O4 is explained by the Neel theory of ferrimagnetism using three superexchange integrals: JA-B=-11.5 kB, JA-A=9.8 kB, JB-B=21.3 kB View full abstract»

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  • Design and control of the 3 degrees of freedom actuator by controlling the electromagnetic force

    Page(s): 3607 - 3609
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    The novel spherical actuator with 3 DOF and its control method are proposed. The proposed 3 DOF spherical actuator is composed of a rotor and a stator which have multi-poles made of permanent magnets and electromagnets, respectively. The rotor can make an arbitrary orientation and a spin by interactions among multi-poles of the rotor and the stator. Also the governing equation for torque generation is derived to control the suggested model. This model is controlled with the suggested governing equation and PD control law. The various experimental results are presented to show the validity of the proposed spherical actuator View full abstract»

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  • New micromachined inductors on silicon substrates

    Page(s): 3547 - 3549
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    Microinductors with two layer vertically stacked spiral-type copper conductor lines and permalloy core have been fabricated, characterized, and compared using micromachining techniques. In this research, micromachined inductors with vertically laminated magnetic alloy cores are found to have better high frequency characteristics such as high inductance, high quality factor, and low AC resistance resulting in low magnetic core losses at high frequencies, than non-laminated types View full abstract»

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  • Design of magnet wheel integrated own drive

    Page(s): 4013 - 4015
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    We have proposed the “magnet wheel” which is a magnetic wheel with the functions of induction repulsive-type magnetic levitation and linear thrust using mechanically revolving permanent magnets. We designed and produced a magnet wheel installed winding for own drive. In the unit, a synchronous motor is constructed by adding only the armature winding because the strong magnets of the magnet wheel are used in common for the field pole of synchronous motor. For the design, the relational expression between the lift force and the driving power is shown. Compared with arrangements using a separate motor, a very compact and light magnet wheel can be constructed. The produced magnet wheel with outside diameter of 190 mm has the payload of about 10 kg at the mechanical clearance of 15 mm View full abstract»

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  • Magnetostriction of Terfenol-D heat treated under compressive stress

    Page(s): 3817 - 3819
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    Heat treatment at temperatures >835°C and compressive stresses >80 MPa substantially increased the magnetostrictive performance of Terfenol-D (Tb0.3Dy0.7Fe1.92 ) under the condition of zero loading. This heat treatment created a built-in prestress which significantly increased the low stress magnetostriction and substantially altered the magnetization curve by reducing its initial susceptibility. For measurements at compressive stresses >15 MPa the effect of the built-in stress was minimal and the magnetostrictive performance was not appreciably altered View full abstract»

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  • Effect of Ir content and sputtering conditions on unidirectional anisotropy of Ni-Fe/Mn-Ir films fabricated under the extremely clean sputtering process

    Page(s): 3919 - 3921
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    An effect of the Ir content and sputtering conditions of Mn-Ir films on the strength of exchange anisotropy was investigated in Ni-Fe/Mn-Ir layers fabricated under the extremely clean sputtering process. We found that the unidirectional anisotropy constant Jk monotonously increased with increasing the Ir content and decreasing the deposition rate of Mn-Ir films. The change of Jk against the deposition rate of Mn-Ir films is possibly caused by the quite slight changes of the microstructure of Mn-Ir films, which were undetectable with XRD View full abstract»

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  • Finite element modeling of nanocomposite magnets

    Page(s): 3223 - 3228
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    Finite element modeling treats magnetization processes within the framework of micromagnetic theory, taking into account the complex microstructure of a magnet. The numerical integration of the Gilbert equation of motion provides the time evolution of the magnetization and thus shows how reversed domains nucleate and expand. The numerical results of static micromagnetic calculations reveal the influence of the intrinsic magnetic properties on the remanence and the coercive field of nanocomposite Nd2Fe14B/α-Fe/Fe3B magnets. An increase of the hard phase anisotropy of only 8% increases the coercive field from 340 kA/m to 450 kA/m in two phase Nd2Fe14B/α-Fe magnets. This effect becomes less pronounced with increasing Fe3B content. In two phase Nd 2Fe14B/Fe3B, the reduction of the soft phase magnetization and/or the soft phase exchange constant leads to an improvement of the coercive field without a significant loss in remanence. The magnetostatic interactions between the magnetic particles of bonded, nanocomposite magnets slightly reduce the remanence and the coercive field View full abstract»

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  • Starting oscillations of an autonomous induction generator

    Page(s): 3562 - 3564
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    The paper presents experimental results concerning the starting oscillation effect for an autonomous induction generator. These results show the importance of the values of the capacitor in parallel to the generator windings and the resistor in series with them. The resistor value is significant especially for small machines. The experimental results are connected with the known theories about autonomous induction generators View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology