IEEE Transactions on Magnetics

We report on studies of the effects of hoop and axial tensile stresses on magnetic flux leakage (MFL) signals from 50% penetration electrochemically milled pits eroded in line pipe steel. It is observed that stress can change the MFL signal by more than 50%, depending on the magnetization of the pipe wall. The studies were performed on pits created in both the absence and presence of 330-MPa hoop ... View full abstract»

Intermodulation distortion in analog magnetic recording is analyzed. Analyses are carried out both for two-signal superimposed recording in audiotape recorders and for color and video signal superimposed recording in video recorders. An error function is used to simulate tape magnetization characteristics assuming a Gaussian switching field distribution. Intermodulation distortion in video color s... View full abstract»

In the alternating current field measurement method, information about the magnetic field distribution above the metal surface is used to detect and size surface-breaking cracks in metals. In this measurement, the incident field is produced by a set of wires carrying a high-frequency current. This paper presents a mathematical technique for the theoretical prediction of the distribution of the mag... View full abstract»

We present an analysis and comparison of magnetization and remanence data from two particulate systems: commercial CrO2 audiotape and a frozen suspension of magnetoferritin particles. The measurements were performed over a range of temperatures, 25°C⩽T⩽120°C for CrO2 and 5 K⩽T⩽10 K for magnetoferritin, and over a range of fields sufficient to saturate ... View full abstract»

At high data rates and information densities, recorded data patterns in digital magnetic recording systems can exhibit severe nonlinearities. Key causes for these nonlinearities are bandwidth limitations of the write path and demagnetizing fields in the recording medium. The present note reviews the structure of these nonlinearities, develops a simple yet generic write-precompensation scheme that ... View full abstract»

Fe-N-Si films have been sputter-deposited in flowing nitrogen (0.3 sccm). Asymmetric X-ray diffraction from the as-deposited films reveals interplanar spacings dhkl that are strong functions of diffracting plane orientation θ relative to the film surface and follow dhklobs(θ)=⟨dhklobs ⟩+Δdhklobs View full abstract»

A general framework for the analysis and design of a class of tubular linear permanent magnet machines is described. The open-circuit and armature reaction magnetic field distributions are established analytically in terms of a magnetic vector potential and cylindrical coordinate formulation, and the results are validated extensively by comparison with finite element analyses. The analytical field... View full abstract»

The average flux densities and their phases through different cross sections of the toroidal core made of ferrimagnetic material have no obvious difference at low frequencies even if the core is excited by several turns of winding current that cover only a very small part of the circumference of the core. However, with the increase of the frequency into the MHz range and the enlargement of the cor... View full abstract»

An approach of readout aperture control for magnetic super-resolution (MSR) readout is described. In order to detect the size of a readout aperture generated by a focused laser beam on an MSR disk, a new mark pattern consisting of short and long marks was recorded. An amplitude ratio of the readout signals between the short and the long marks is proportional to the aperture size. By maintaining th... View full abstract»

The design and analysis of a scale-model suspension test facility for magnetic levitation (maglev) is discussed. We describe techniques for the design, construction, and testing of a prototype electrodynamic suspension (EDS) levitation system. The viability of future high-temperature superconducting magnet designs for maglev has been investigated with regard to their application to active secondar... View full abstract»

We consider a new constraint on stored data in partial response digital magnetic recording. The one-pairs constraint is an upper bound on the maximum number of symbols between pairs of ones in a coded sequence and can be considered as an alternative to the widely used (0, G/I) constraint. The constraint limits quasi-catastrophic error propagation and guarantees the occurrence of superior timing co... View full abstract»

Electrodynamic suspensions (EDS) are highly undamped and require some form of active control or a secondary suspension to achieve adequate ride quality. This paper reports on efforts to develop a version of EDS that uses controllable magnetic forces to eliminate the need for any secondary suspension. The magnetic forces act directly on the guideway and avoid the need to have unsprung weight and a ... View full abstract»

A magneto-optical method, conceived in our laboratory to measure Brown's relaxation frequency of ferrofluids, is compared with Fannin's technique based on impedance measurements (slit toroid). We have developed a complete theory and an experimental setup of the first method and have briefly described the second one. We present a study of Brown's relaxation of cobalt ferrite Fe2CoO4... View full abstract»

The magnetic field of a ring head has been analyzed by Westmijze [1953], using a conformal mapping, and by Fan [1961], using Fourier techniques. Here these methods are reexamined and combined to give, for the first time, an explicit analytic expression for the harmonic coefficients in the Fan solution View full abstract»

A model for error rate analysis including the effect of texture noise is described. The impact of long-range correlated and nonstationary texture noise on system performance is examined for various types of partial response (PR4 and EPR4) channels and replay heads [magnetoresistive and giant magnetoresistive (GMR)]. A higher-order partial response polynomial (EPR4) is found to have better toleranc... View full abstract»

Results on design, fabrication, and testing of silicon micromachined magnetic actuators are presented. Electroplated, low-stress Permalloy (Ni80Fe20) material is the medium for magnetic interaction and force generation. The Permalloy piece is supported by a structural plate, which consists of polycrystalline silicon thin film prepared by low-pressure chemical vapor deposition... View full abstract»

With the rapid development of high-frequency magnetic components, it is important to know the distributions of the electrical and magnetic fields in the ferrimagnetic cores. In this paper, an improved model for analyzing the distributions of electrical and magnetic fields in a toroidal core is given. It supplies the basis for the theoretical analysis of the iron loss in the magnetic cores, which i... View full abstract»

The spectra of internal ac impedance and fluxmetric and energetically effective circular permeabilities are calculated for infinite slab and cylinder in classical and domain models. The domain models assume transverse bar domains for a slab and transverse circular disk domains for a cylinder, with technical magnetization being carried out by domain wall displacements. For each case, a general form... View full abstract»

We present a general analysis method for three-dimensional (3-D) eddy current problems with a moving conductor. The indirect boundary integral equation method (IBIEM) is employed for 3-D electromagnetic field problems including an arbitrarily shaped conductor with constant relative velocity. Since the 3-D motion effect is taken into account in the fundamental Green's function for the governing equ... View full abstract»

Two end cap designs for bird cage coils for application in nuclear magnetic resonance head imaging are presented. The objectives of the new design are to improve the B1 field homogeneity within the coil and to improve the SNR. Design I extends the legs and one end ring of the bird cage coil onto the end cap. The radius of the end ring on the end cap is optimized to maximize the axial fi... View full abstract»