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Magnetics, IEEE Transactions on

Issue 4 • Date July 1999

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Displaying Results 1 - 18 of 18
  • Correction to "Williams-Comstock model with finite-length transition functions"

    Publication Year: 1999 , Page(s): 2197
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (31 KB)  

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  • Accurate approximation of fields and spectral response functions for perpendicular recording heads

    Publication Year: 1999 , Page(s): 2172 - 2179
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Solutions for the magnetic potential in rectangular regions with simple boundary conditions are used to approximate the two-dimensional potential in the head face plane of a recording head. This method of approximation can be applied to any recording head with rectangular corners, in the presence of an underlayer. The slot approximation is demonstrated for ring heads and shielded (magnetoresistive) pole heads. The quarter plane approximation is given for application to finite-length heads. Estimates of the field components and the spectral response function are derived from the approximate potential. The simple slot approximation is shown to be at least as accurate as other, often more complicated, methods of approximation. Most significantly, both the slot and the quarter-plane approximations are easy to apply and need no prior knowledge of the head field of the particular geometry under consideration View full abstract»

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  • Approximate Fourier coefficients for gapped magnetic recording heads

    Publication Year: 1999 , Page(s): 2180 - 2186
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    An investigation is presented of the number of exact Fourier terms needed to evaluate the field components of a ring head, a slotted plane, and planar heads of various dimension ratios to specified accuracy. Simple approximate formulas for the coefficients of a ring head and a slotted plane are given, and two approximations to the coefficients of a planar head of given dimensions are provided. The accuracy of the field components and the spectral response function, each evaluated with the approximate coefficients, is used to assess the usefulness of these approximations. Both of the approximations for the coefficients of planar heads lead to excellent estimates of the field components View full abstract»

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  • New hybrid technology for planar fluxgate sensor fabrication

    Publication Year: 1999 , Page(s): 2111 - 2117
    Cited by:  Papers (8)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    We have adapted a new printed circuit board (PCB) technology to the fabrication of ultraflat and sensitive fluxgate magnetic field sensors. The two outer layers of the PCB stack compose the electrical windings of fluxgates, while the inner layer is made of a micro-patterned amorphous magnetic ribbon with extremely high relative magnetic permeability (μr≈100 000). Two basic configurations were considered: one based on a toroidal magnetic core and the other on a rectangular core with and without an air gap. The field response and sensitivity of the fluxgate devices have been studied as a function of the gap length, the excitation current, and excitation frequency. Compared to fluxgate sensors of similar size, a relatively high sensitivity of 60 V/T was found at 30 kHz for a five-winding detection coil wound around a rectangular E-shaped magnetic core. This high performance is primarily attributable to the high-permeability magnetic core. The results clearly show the potential of this fluxgate device for application as a magnetic sensor View full abstract»

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  • Quantitative analysis of magnetic resonance radio-frequency coils based on method of moments

    Publication Year: 1999 , Page(s): 2118 - 2127
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2712 KB)  

    To investigate both spectral and spatial domain characteristics of radio-frequency coils in magnetic resonance experiments, we have developed a new approach based on the method of moments. Instead of the conventional point-matching scheme, the loop testing function is used. Such a testing function decreases the complexity of computation and elevates the efficiency of simulation. With the proposed testing function incorporated with a pulse basis function based on coil geometry topology, performance of both surface coil and volume coil can be predicted with consistent results compared with experimental data View full abstract»

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  • New method for measurement of complex magnetic permeability in the millimeter-wave range, part II: hexaferrites

    Publication Year: 1999 , Page(s): 2104 - 2110
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    Magneto-optical methods were applied for the first time in millimeter wavelength range for characterization of anisotropic ferrites. The principles of the free-space magneto-optical method are presented and the new experimental procedures leading to the determination of millimeter-wave permeability and permittivity in anisotropic ferrite materials are described. The measurements were performed with a computer-controlled W-band (70-120 GHz) quasi-optical-waveguide bridge. A backward-wave oscillator was used as a source of tunable millimeter wave radiation. The oriented Sr-hexaferrite ceramic was selected for the verification of millimeter-wave magneto-optical method. The magneto optical measurements in transverse configuration revealed strong anomalous dispersion in the millimeter-wave refractive index spectrum for Sr hexaferrite, mainly due to the frequency variation of magnetic permeability. Computer simulations revealed a good agreement of measured parameters with known data for Sr hexaferrite. It was shown that the free-carrier absorption (σ~0.05 Ω-1 cm-1) and magnetic permeability contribute to the relatively high millimeter-wave losses in hexaferrite ceramics. The frequency dependence of Faraday rotation in the millimeter-wave range was measured, and the experimental results are discussed. The results presented in this paper demonstrate that this new magneto-optical method is capable of providing accurate dielectric and magnetic data in the millimeter-wavelength range View full abstract»

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  • Theory of high-gradient magnetic filter performance

    Publication Year: 1999 , Page(s): 2128 - 2132
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB)  

    A unique general model for high-gradient magnetic filters is presented. The functional dependence of the filter performance on the system's physical and geometrical parameters is derived. The derived theoretical expression makes it possible to explain both of the two different, apparently opposite, experimental results reported in the literature. The new quality factor does not include the suspension viscosity, but instead depends on the suspension density, which leads to the application of the formula for a larger class of filtration media including liquids, gases, and vapors View full abstract»

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  • Experimental study of Hopkinson effect in single domain CoFe2 O4 particles

    Publication Year: 1999 , Page(s): 2155 - 2161
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Nanosize particles of CoFe2O4 have been synthesized by the citrate precursor technique. Considerably higher coercive force (1.68 kOe) than that obtained by the conventional technique (1.00 kOe) is associated with the nanostructure of CoFe2 O4. These nanosize ferrimagnetic CoFe2O4 particles exhibit chainlike clusters indicating strong interparticle interactions and reduced magnetic moment, which is attributed to anisotropy and canted spin structure at the surface of the particle. The magnetization shows a peak just below the Curie temperature Tc during heating in the presence of a small magnetic field (the Hopkinson effect), On the other hand, the magnetization increases monotonically when the system is cooled from T c. This peak is associated with the single domain behavior of nanocrystalline CoFe2O4 particles and explained within the mathematical formalism given by Stoner and Wohlfarth in conjunction with other explanations of Hopkinson effect View full abstract»

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  • Method for measuring and characterizing core loss in a motor

    Publication Year: 1999 , Page(s): 2146 - 2151
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    Because of the complex shape and variable flux densities of the toothed cores of motors, characterization of their core losses has been difficult. Manufacturers' material specification sheets usually refer only to Epstein tests, based on sinusoidally varying flux densities in simple geometries. Here, a more accurate and direct method for measuring core loss is presented. The method spins the motor core in a magnetic field and then measures the spin speed and drag torque imposed on the core. This test was used to successfully characterize the core loss in a small dc brushless spindle motor. Among the parameters examined were the turning speed, maximum gap flux, lamination material, lamination thickness, and the effects of stress-relief annealing. Mathematical models of the core loss were constructed for specific core geometries based upon an assumed form for the empirical data. The actual core losses were higher than would have been predicted from conventional Epstein tests View full abstract»

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  • Analytical study of radial stability of permanent-magnet synchronous couplings

    Publication Year: 1999 , Page(s): 2133 - 2136
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    Magnetic couplings are used to transmit a torque through a magnetic separation wall without any mechanical contact between the two rotors. But the usual cylindrical-airgap magnetic coupling is radially unstable. This instability can be computed from the analytical formulas of the force components exerted between two magnets. The instability can then be analyzed. We present a structure for an astable coupling. Such a coupling does not generate any radial force when a radial displacement occurs. It is a perfect mechanical filter View full abstract»

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  • Formation and magnetostructural characterization of the novel ternary compound Ce3Fe29-xMox

    Publication Year: 1999 , Page(s): 2162 - 2165
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (124 KB)  

    Formation and magnetostructural properties of the novel ternary ferromagnetic compound Ce3Fe29-xMox is reported. It was obtained in alloys with nominal compositions Ce3 Fe29-xMox, x=1.4, 1.5, and 1.6, prepared by arc melting and annealing during three weeks at 950°C. The crystal structure was well resolved as monoclinic with space group A2/m (No 12). Quantitative phase analysis, based on the processing of the X-ray diffraction patterns by the Rietveld method, was performed. Ce3 Fe29-xMox is the main phase (78-72 wt.%) with lattice parameters a=10.553(1) Å, b=8.511(1) Å, c=9.688(1) Å, and β=96.78(1)°. It coexists with Ce(Fe,Mo) 12 as main spurious phase. Atomic positions and mean Fe-Fe interatomic distances are reported. Temperature-dependent magnetic susceptibility shows well-defined transitions at 7 and 115°C, which correspond to the 3:29 and 1:12 phases, respectively. Saturation magnetization at 4.2 K is 123 emu/g View full abstract»

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  • Magneto-optical recording on CoPtRe alloy films as a novel material

    Publication Year: 1999 , Page(s): 2166 - 2171
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    Magneto-optical (MO) disks using CoPtRe ternary alloy films have been investigated as a novel recording material for a blue laser recording. For various types of disk structure, the Kerr rotation, the Kerr ellipticity, and the figure of merit were calculated and an optimum structure was estimated. Magneto-optical recordings were made on a CoPtRe MO disk at wavelengths of 830 and 530 nm. The recording properties were almost equivalent to those for Co/Pt multilayers View full abstract»

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  • Hysteresis modeling based on similarity

    Publication Year: 1999 , Page(s): 2090 - 2096
    Cited by:  Papers (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    A principle of constructing hysteresis models with stable minor loops is proposed. It has been found that a modeled reversal curve of any order can be obtained by copying (transplanting) the segment of the first-order curve that has the same overall dimensions and is the nearest to the modeled curve in the M- (or B-) direction. It is discussed how models with different grades of accuracy can be implemented within the framework of the approach. For the case when experimental first-order curves are absent, a procedure for their generation is suggested. The modeling is in remarkably good agreement with experimental data View full abstract»

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  • Single phase 1-kVA amorphous core transformer: design, experimental tests, and performance after annealing

    Publication Year: 1999 , Page(s): 2152 - 2154
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    The design and experimental implementation of a single-phase power transformer operating at 1 kVA, 110/220 V, and 60 Hz, with an amorphous alloy core are described. The prototype core material is annealed in an argon atmosphere, under a DC magnetic field applied along the ribbon length. The experimental results are presented to compare the amorphous core transformer performance with another transformer with the same rated power, but with a silicon steel core View full abstract»

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  • Reduced complexity maximum likelihood sequence estimation for multitrack high-density magnetic recording channels

    Publication Year: 1999 , Page(s): 2187 - 2193
    Cited by:  Papers (10)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    In this paper we investigate the problem of designing reduced complexity detectors for multitrack high-density magnetic recording systems. The detectors derived in this work operate on superstate sets and carry several survivors for each set. We show that such a reduced state increased survivor approach provides near optimal performance to the maximum likelihood method, namely the Viterbi Algorithm (VA), but operate at a fractional complexity of the VA View full abstract»

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  • Self-regulating permanent magnet linear motor

    Publication Year: 1999 , Page(s): 2137 - 2145
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    A new type of self-regulating permanent magnet linear motor (PMLM) is proposed. This PMLM utilizes chiefly permanent magnets and a ferromagnetic yoke for producing a force to propel a flying vehicle. A detailed structure and the theory of the proposed PMLM are given View full abstract»

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  • Frequency analysis of classical Preisach model

    Publication Year: 1999 , Page(s): 2097 - 2103
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (164 KB)  

    The paper contains an analysis of the classical Preisach model from a frequency point of view. A Fourier analysis retrieves the necessary and sufficient conditions on the Preisach weighting function to have an output with half-wave symmetry; i.e., only odd harmonics are present. For a wide class of weighting functions, it is shown that all odd frequencies are present. As a consequence, a filtering method is suggested that enhances time-series data from sinusoidal input, which can be used for Preisach model identification View full abstract»

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  • Analysis of magnetic aftereffects in nanocrystalline SmFeCo by the Preisach hysteresis model

    Publication Year: 1999 , Page(s): 2194 - 2196
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (96 KB)  

    Magnetic viscosity measurements performed on nanocrystalline SmFeCo spring magnets with different Fe content are analyzed by the Preisach hysteresis model. The model gives a unified description of hysteresis and relaxation properties. Comparison between calculated and measured viscosity permits one to estimate the aftereffect activation volume υ. Calculated υ1/3 values are approximately equal to the average grain size of the hard phase 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