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Magnetics, IEEE Transactions on

Issue 6 • Date Nov. 1995

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Displaying Results 1 - 25 of 272
  • Conference Author Index

    Publication Year: 1995
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    Freely Available from IEEE
  • Coupled magnetostatic volume wave straight edge resonators for multipole microwave filtering

    Publication Year: 1995 , Page(s): 3476 - 3478
    Cited by:  Papers (4)
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    Magnetostatic wave coupled straight edge resonators have been experimentally tested by means of a waveguide ferromagnetic resonance experiment to check their potential as microwave coupled filters. Few dB ripples and tens of MHz bandwidths have been obtained for configurations in the range λ/4- to λ-coupling View full abstract»

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  • Magnetic anisotropy and spin dynamics in amorphous thin ferromagnetic films

    Publication Year: 1995 , Page(s): 4035 - 4037
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    An analytic calculation of the initial permeability frequency spectra using the Landau-Lifshitz theory is compared with experimental results obtained on ferromagnetic thin films with an in-plane uniaxial magnetic anisotropy. Agreement between the theoretical and the experimental results may not be very good. This may be due to magnetic anisotropy dispersion in the film. This dispersion is studied and seems to be due to magnetic ripples. Measurement of the ripple effect is done through the measurement of the transverse biased susceptibility and compared with theoretical results obtained with the Hoffmann theory of ripples View full abstract»

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  • Open C-shaped permanent magnets for NMR imaging

    Publication Year: 1995 , Page(s): 3740 - 3742
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    Previously developed design methodology provides a systematic analysis of magnetic structures composed of uniformly magnetized prisms that generate uniform fields. The approach is based on the property of cancellation of field singularities at the interfaces between the media. Applications of this design methodology thus far have been restricted to magnetic structures with concave cavity boundaries. However, convex cavity boundaries may be necessary for C-shaped magnetic structures involved in medical NMR imaging that feature a side opening in addition to openings at both ends. This paper introduces transition structures placed in the region of the magnet opening and analyzes their field properties. The results indicate a remarkable benefit of the transition elements in terms of field uniformity and the size of the imaging region View full abstract»

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  • Comparison of Jiles and Preisach hysteresis models in magnetodynamics

    Publication Year: 1995 , Page(s): 3551 - 3553
    Cited by:  Papers (9)
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    In this paper a comparative study is presented of four hysteresis models with regard to the numerical computation of the fields inside soft magnetic laminations. Addressed topics include parameter identification and precision. All computed results are compared with measurements View full abstract»

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  • Frequency dependence of the piezomagnetic strain coefficient

    Publication Year: 1995 , Page(s): 4038 - 4040
    Cited by:  Patents (1)
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    The frequency dependence of the piezomagnetic strain coefficient (g33) has been investigated through Plane Wave Model characterisation of a Terfenol-D sample. It is found to have a frequency dependence of 1/√ω with a corresponding frequency dependent loss term. It is proposed that this frequency dependence in g33 is a consequence of the mechanical defects in the material which affect the magnetic properties of the material through the magnetomechanical coupling k33 View full abstract»

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  • Degrees of freedom control of a magnetically levitated rotor

    Publication Year: 1995 , Page(s): 4202 - 4204
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    Design and realization of a four active and one passive axis magnetic suspension for vertically high speed rotating rotor are performed. Control is realized directly on the physical degrees of freedom. The mathematical modelling of the dynamic behaviour of the rotor enables the gain of knowledge of its speed limitation and to increase it View full abstract»

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  • Invar properties of the interstitial carbides of Nd2Fe 17

    Publication Year: 1995 , Page(s): 3713 - 3715
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    High-temperature X-ray diffraction experiments from 50°C to 400°C have been carried out to measure the thermal variations of the lattice parameters of Nd2Fe17Cx (x=0.5, 1.0), which has the rhombohedral structure of the Th2Zn17 type, space group R3¯m. The interstitial carbides Nd2Fe17Cx, together with their parent Nd2Fe17, exhibit Invar-like thermal expansion anomalies below their Curie temperatures, T c. Although the introduction of carbon into Nd2Fe 17 leads to lattice expansion and enhancement of Tc, the observed positive spontaneous magnetostriction of the carbides is comparable with that of Nd2Fe17. It is proposed that such a spontaneous magnetostriction can be ascribed to the occurrence of some short Fe-Fe distances and the strong distance dependence of the positive and negative interactions View full abstract»

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  • Magnetic fluid based variable inductors for inductively coupled plasma applications

    Publication Year: 1995 , Page(s): 4175 - 4177
    Cited by:  Papers (2)
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    This paper identifies a resonant LCC circuit zero voltage switched power supply topology which can be used in conjunction with a variable inductor in inductively coupled plasma applications. Steady state, fundamental component, simulation results confirm that the use of a variable inductor allows the operating power range for zero voltage switching to be extended without having to change the switching frequency View full abstract»

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  • A study on kinetic characteristics of a cylindrical moving coil linear DC motor for a vibrator

    Publication Year: 1995 , Page(s): 3725 - 3727
    Cited by:  Papers (1)
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    A cylindrical moving coil linear DC motor has been developed for a vibrator which is driven at a high frequency with a short stroke. The actuator is supposed to be driven using resonances of spring plates which are placed at the end of the permanent magnet and the armature, respectively. This paper describes the investigation of stroke to frequency characteristics as the kinetic characteristics of the actuator View full abstract»

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  • 90° domains and coupling in Co/Cu giant magnetoresistance superlattices on Si(100) substrates

    Publication Year: 1995 , Page(s): 3921 - 3923
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    Giant magnetoresistance and interlayer coupling in Co/Cu superlattices grown by e-beam evaporation have been investigated with the combined three-axis magneto-optical Kerr effect, magnetotransport measurements, X-ray diffraction, and transmission electron microscopy. Correlations between 90° alignment of the magnetization in adjacent layers and magnetoresistance oscillation curves suggest that the GMR in superlattices with imperfect interfaces results from 90° relative orientation of domains in adjacent Co layers View full abstract»

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  • Thick yttrium-iron-garnet (YIG) films produced by pulsed laser deposition (PLD) for integration applications

    Publication Year: 1995 , Page(s): 3832 - 3834
    Cited by:  Papers (5)
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    High magnetic and dielectric quality, thick (50-100 μm), epitaxial, yttrium-iron-garnet (YIG) films were deposited at high rate by PLD. A two-step (low temperature deposition followed by rapid thermal anneal) low thermal budget PLD process was demonstrated suitable to deposit thick polycrystalline YIG films on metallized Si and GaAs. A modified PLD apparatus is used to deposit uniform, 80-100 μm, thick YIG films on 3-inch semiconductor wafers for integrated microwave circulator fabrication View full abstract»

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  • High speed variable-inductor controlled with DC-DC converter

    Publication Year: 1995 , Page(s): 4247 - 4249
    Cited by:  Papers (3)
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    This paper describes a fundamental consideration on high speed control of the orthogonal-core type variable-inductor. The variable-inductor is applicable to a VAR compensation in the electric power system. The transient characteristics of the variable-inductor under the condition of DC control are discussed based on simulation and experiment. For high speed operation, we present an instantaneous control of the primary current. A simple control circuit using a DC-DC converter is demonstrated in this paper View full abstract»

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  • Experiment and analysis of levitation-melting method of induction furnace

    Publication Year: 1995 , Page(s): 4205 - 4207
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    This paper presents basic data on the effect of a high-frequency induction coil in the levitation-melting method. The buoyant force is measured with a digital balance under the constant 30 kW output, and the effect of the coil's position on the buoyancy is investigated experimentally. In addition, the flux distribution in the actual coil which has asymmetric shape, is calculated with the three-dimensional boundary element method. The rotating motion of a levitating metal caused by an asymmetric flux distribution is discussed. In the paper we show that controlling the movement of ingot may be a solution to the problem of uniform heating in this system View full abstract»

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  • Performance simulation of hysteresis motors using accurate rotor media models

    Publication Year: 1995 , Page(s): 3542 - 3544
    Cited by:  Papers (6)
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    Recently, there has been an increased demand for small and medium sized brushless-type synchronous motors. Among these types, hysteresis motors have been especially used in those applications requiring precise speed and constant starting torque capabilities. In the past, several digital techniques for simulating the performance of hysteresis motors have been developed. These technique, however, involved significant approximations to the rotor magnetic properties. The purpose of this paper is to present a numerical approach through which enact rotor magnetic properties can be incorporated in the developed simulation techniques by utilizing Preisach-type hysteresis models. Numerous simulations for a sample 3-phase motor have been performed. It is found that predicted v-i characteristics qualitatively matches similar published experimental results. Other results concerning the developed torque and harmonic content are also given in the paper View full abstract»

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  • Fine magnetic particles in layered silicates and zeolites

    Publication Year: 1995 , Page(s): 3784 - 3786
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    Ultrafine Ni particles have been generated at ambient temperatures in clay (montmorillonite) and zeolite (mordenite) matrices. The synthesis involves a reduction in aqueous solutions of the ion-exchanged clay or zeolite with sodium borohydride. SQUID magnetometer measurements reveal single domain Ni particles with superparamagnetic properties. While the Ni particles in clay have a narrow distribution of blocking temperatures Tb and particle size, they seem to have in zeolites a broader distribution of Tb and particle size. Time decay measurements of thermoremanent magnetization also support single domain characteristics View full abstract»

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  • Dynamic behavior of dissolved oxygen under magnetic fields

    Publication Year: 1995 , Page(s): 4259 - 4261
    Cited by:  Papers (2)
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    It is an interesting question whether or not magnetic fields have any influence on dissolved oxygen in living tissues and cells. This study focuses on the behavior of dissolved oxygen under strong magnetic fields of up to 8 T with the gradient of 50 T/m. We used a horizontal type of superconducting magnet. We placed a water chamber in the magnet's bore for 1 hour, then we took it out of the fields to measure the dissolved oxygen concentration. When oxygen gases were introduced into the distilled water to increase oxygen concentration more than 11 mg/l, we observed clear redistribution of dissolved oxygen concentration. The degree of the redistribution was dependent on the dissolved oxygen concentration at the initial condition. Redistribution of dissolved oxygen was not observed in an equilibratory state of oxygen pressure at the air atmosphere. We also observed that the increase and decrease In dissolved oxygen concentration during and after magnetic field exposures exponentially changed. The time constants for the increase and decrease were 17 min-18 min and 7 min-8 min, respectively View full abstract»

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  • Precession of conduction-electron spins near an interface between normal and magnetic metals

    Publication Year: 1995 , Page(s): 3871 - 3873
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    A current crossing the interface between a ferromagnetic layer F 1 and a normal layer N induces a magnetization in the conduction-electron gas near the interface. This “spin-injection” manifests itself as a DC voltage between N and a second ferromagnetic layer F2 deposited on N. We treat the case where the magnetizations of F1 and F2 are perpendicular. The spin <s&oarr;> of injected conduction electrons precesses around the exchange field present in F2. As a result, the direction of the local conduction-electron spin density in F 2 is a function of the distance from the N-F2 interface View full abstract»

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  • Power losses of soft magnetic ferrite under controlled magnetizing condition

    Publication Year: 1995 , Page(s): 4056 - 4058
    Cited by:  Papers (1)
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    Power losses of a soft magnetic ferrite were measured under several controlled magnetizing conditions, in which the magnetic induced voltage was strictly controlled to be required waveforms; sine, rectangle and rectangle with steps. Different power losses in one magnetizing cycle are obtained even under the magnetizing conditions in which the same eddy current and hysteresis losses are expected. Power losses under sinusoidal excitations are higher than those under rectangular voltage excitations. It is considered that the hysteresis losses, which are generally believed to be constant and independent of magnetizing frequency, should depend on the magnetizing waveform, that is, the change of the magnetizing speed View full abstract»

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  • Influence of microstructure on micromagnetic Barkhausen emissions in AISI 4140 steel

    Publication Year: 1995 , Page(s): 4053 - 4055
    Cited by:  Papers (2)
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    The effects of microstructure on the micromagnetic Barkhausen signal emissions in AISI 4140 steel are reported. The Barkhausen signal amplitude is known to be highly sensitive to the type and distribution of microstructural inhomogeneities, such as grain boundaries, precipitates and dislocations. The Barkhausen measurements were taken on samples having pearlitic, spheroidized and bainitic microstructures. The Barkhausen emissions were measured in terms of rms voltage peak-to-peak voltage and number of events per cycle. It is shown that Barkhausen signals can be used to distinguish between pearlitic and bainitic microstructures View full abstract»

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  • Analysis of the reduction of detent force in a permanent magnet linear synchronous motor

    Publication Year: 1995 , Page(s): 3728 - 3730
    Cited by:  Papers (28)
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    The problem in improving the positioning precision of a permanent magnet linear synchronous motor (LSM) is the large detent force caused by the permanent magnet. The detent force is thought to arise from the difference of the position of a permanent magnet end and a tooth position. If one detent force is independent from the other, we can reduce the total detent force of the permanent magnet linear synchronous motor by the arrangement of a permanent magnet end and a tooth. This paper presents are improvement of the arrangement of the permanent magnet end of a linear synchronous motor in order to reduce the detent force by using numerical analysis View full abstract»

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  • Magnetic properties of NiFe sputtered on sloping surfaces

    Publication Year: 1995 , Page(s): 3817 - 3819
    Cited by:  Papers (9)
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    RF diode sputtered NiFe films deposited on tilted surfaces can exhibit a 90° rotation of the magnetic easy axis from the direction of applied magnetic field. The rotation is largely independent of the sign of the magnetostriction, indicating a shape anisotropy originating with film crystallite morphology. It is less prevalent with increasing substrate bias. At low powers a large magnetic anisotropy is observed perpendicular to the plane defined by the tilted surface normal and the substrate holder normal. It is important for the function of thin film heads that films deposited on slanted surfaces have good magnetic properties, particularly near the apex region of inductive film heads. Evaporation experiments have shown that the magnetic properties of thin NiFe films depend critically on deposition angle-of-incidence. The situation for sputtered films is more complex since the source is large and close to the substrate being coated. However, even for sputtering when the surface being coated is tilted with respect to the substrate holder and target surfaces, material will impinge asymmetrically with respect to the slanted surface normal, so some sort of averaged angle-of-incidence effect can be expected View full abstract»

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  • Exchange coupling and microstructure in annealed cobalt-rich amorphous alloys

    Publication Year: 1995 , Page(s): 4015 - 4019
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    Low-field magnetic properties have been measured in annealed ribbons of amorphous Co95-xFe5(BSi)x. The M-H loops show coercivities of order 100 mOe and weak but consistent exchange anisotropy of order 10 to 100 mOe. The direction of the field offset can be reversed by reversing the ribbons in the pickup coil or by applying a negative field of order 30 to 40 Oe. We have made an extensive microstructural investigation of these alloys to understand the origin and nature of the exchange-coupling component responsible for the offset. Annealing in air first causes surface oxidation to B2 O3 and SiO2 which reduces the glass-former content in the underlying amorphous material. Continued heating well below the bulk crystallization temperature results in premature crystallization of a layer of order 10 to 100 nm in thickness. The crystallization product is either fcc or hcp Co (plus solutes). The fcc cobalt is highly-faulted which seems to be necessary for the exchange anisotropy View full abstract»

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  • Magnetic field analysis of air-core superconducting transformer

    Publication Year: 1995 , Page(s): 4124 - 4126
    Cited by:  Papers (5)
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    In the applications of the superconducting wires to the AC power field, the magnetic field analysis is very important in order to investigate their power loss and stability. In this paper, a calculation method of magnetic field in the air-core transformer, which is one type of the superconducting transformer, is introduced. Then, based on this method, the magnetic field acting on the transformer winding is analyzed. Results of analysis and that the magnetic field of the air-core superconducting transformer does not distribute uniformly and that the magnetic field under load has a rotating component View full abstract»

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  • A phase shift in the coupling in Co1-xAgxCu/Co1-xAgx systems

    Publication Year: 1995 , Page(s): 3924 - 3926
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    Upon the addition of Ag impurities in the Co layers of high quality molecular-beam-epitaxy grown Co/Cu(111) trilayers, the antiparallel coupling observed in the Co/Cu/Co trilayers for tCu <12 Å has been transformed to a parallel coupling which appears as a significant shift in the phase of the interlayer coupling. In addition, the amplitude of the exchange coupling oscillations appears to decrease exponentially with increasing Cu layer thickness 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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Meet Our Editors

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