Scheduled System Maintenance:
Some services will be unavailable Sunday, March 29th through Monday, March 30th. We apologize for the inconvenience.
By Topic

Magnetics, IEEE Transactions on

Issue 6 • Date Nov 1991

Filter Results

Displaying Results 1 - 25 of 319
  • Transverse susceptibility and anisotropy fields of iron-oxide pigments

    Publication Year: 1991 , Page(s): 4639 - 4641
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The transverse susceptibility of oriented iron oxide samples was measured. The results are in qualitative agreement with theoretical curves. From singular points of the transverse susceptibility the anisotropy fields of the pigments were determined. For Co-free pigments these agree well with the chain of spheres model. The anisotropy fields of the Co-modified pigments depend significantly on the kind of modification. This is interpreted with differences in the strength of uniaxiality of the anisotropy View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of computationally efficient forms of FDTS/DF against PR4-ML

    Publication Year: 1991 , Page(s): 4567 - 4572
    Cited by:  Papers (7)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    The authors compare the error-rate performance and circuit complexity of fixed-delay tree search with decision-feedback (FDTS/DF) to that of Class IV partial response equalization followed by Viterbi detection (PR4-ML). The impact of realistic impulse responses, misequalization, phase errors, and offtrack interference on both detection strategies is explored. Two computationally efficient methods for implementing FDTS/DF are presented. These FDTS/DF architectures avoid explicit multiplication-one uses a RAM-based table lookup and the other uses binary equalization over the tree-depth View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A switched reluctance motor model with mutual coupling and multi-phase excitation

    Publication Year: 1991 , Page(s): 5423 - 5425
    Cited by:  Papers (22)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A novel switched reluctance motor (SRM) magnetic equivalent circuit model with mutual coupling and multiphase excitation is presented which successfully predicts the magnetic behavior of an SRM with multiple phase at a time excitation. The model is new in that it spreads the saturable elements throughout the machine rather than at the tooth tips. This allows the dominant mutual coupling effect, core saturation during multi-phase excitation, to be modeled. The authors describe methods for calculating or functionally representing values for the circuit elements given the machine geometry and a minimum number of finite-element models, a method for modeling saturable materials, and a method for solving the resulting mesh for flux values given excitation levels. The model results are compared with intermediate finite-element results View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlinear effects of transition broadening

    Publication Year: 1991 , Page(s): 4831 - 4833
    Cited by:  Papers (16)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Nonlinear broadening of closely spaced transitions has been studied using micromagnetics simulations. Results show a large increase in the width of a transition due to the demagnetizing field effect of earlier transitions. Based on this observation, a simple recording channel model is developed to investigate the effects of nonlinear transition broadening on detection performance. This analysis shows that the conventional peak detector is much less sensitive to the detrimental effects of nonlinearity than the more advanced partial response maximum likelihood (PRML) scheme, mainly due to the extra transition spacing provided by the minimum run-length-limited constraint. This result suggests that in order to preserve the improved signal detection capability of advanced signal processing schemes like PRML, reduction of nonlinearity is essential in the media design View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects on magnetic toners in AC and DC magnetic fields

    Publication Year: 1991 , Page(s): 5426 - 5428
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Magnetic forces acting on moving magnetic toners have been investigated by dropping the toners through DC and AC magnetic fields. A CCD (charge coupled device) camera system was used to observe the effects on magnetic toners in the magnetic fields, The distribution of toner chains in a DC magnetic field depends on the distribution of applied DC magnetic force. After applying an AC magnetic field greater than the coercivity of the toners, the length of toner chains was reduced and the sliding velocity of the toner chains was increased as the applied AC magnetic field was increased. The effects on magnetic toners by applying an AC magnetic field can be considered as an AC demagnetizing effect View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Submicron magnetizing and its detection based on the point magnetic recording concept

    Publication Year: 1991 , Page(s): 5286 - 5288
    Cited by:  Papers (8)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The authors investigate submicron magnetic bit recording and detection using a tip of a magnetic force microscope as both the single-pole head and the magnetic field detector. To attain high sensitivity, the magnetic tip mounted at the end of the 200-μm cantilever is photolithographically fabricated as a monoblock. The recording medium is double-layered cobalt-chromium and permalloy. The Permalloy tip and an exciting coil placed on the side of the medium opposite the tip (radius=0.8-0.1 μm) concentrate magnetic flux when bringing the tip into contact with the medium. The mechanically modulated tip scanning about 400-120 nm above the medium easily detects the changes of the magnetic force gradient. Regions about 1 through 0.5 μm in diameter can be magnetized, and they can be erased by an inverse magnetic field. Sharper tips will allow magnetization and its detection in even smaller regions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic and magneto-optical properties of Ga doped EuIG single crystals

    Publication Year: 1991 , Page(s): 5340 - 5342
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Magnetization and Faraday rotation measurements at 1150 nm have been performed on Eu3Fe5-zGazO12 single crystals (0⩽z<0.9) quenched at two temperatures, Tq=1200 and 1473 K, as a function of temperature and magnetic field. The heat treatments, which have a greater influence on magnetization than Faraday rotation, shift the magnetic compensation temperature towards lower T when T q increases. The magnetization results are interpreted on the basis of an induced moment of Eu3+ in agreement with W.P. Wolf and J.H. Van Vleck, and G.F. Dionne's model of ferrimagnetic garnets, assuming that the distribution of Ga on the different sites is the same as YIG:Ga crystals. The contribution of Eu to Faraday rotation in EuIG shows that the gyroelectric magnetooptical coefficient of the model of W.A. Crossley et al., is a linear function of temperature for T>50 K (gEu constant) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetostrictive direct drive rotary motor development

    Publication Year: 1991 , Page(s): 5355 - 5357
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    Highly Magnetostrictive materials such as Tb0.3Dy0.7Fe2, commercially known as Terfenol-D, have been used to date in a variety of devices such as high-power actuators and linear motors. The larger magnetostriction available in twinned single-crystal Terfenol-D, approximately 2000 p.p.m. at moderate magnetic field strengths, makes possible a new generation of magneto-mechanical devices. The authors are investigating the potential of this material as the basis of a direct micro-stepping rotary motor. Such a motor would be a high torque micro-radian stepper, capable of precision movements and self-braking in the power off state. A motor prototype being developed based on the proven `inch worm' technique is presented. Results of mathematical modeling techniques are presented, including magnetic, structural, and both linear and nonlinear dynamic calculations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic recording channel model with intertrack interference

    Publication Year: 1991 , Page(s): 4834 - 4836
    Cited by:  Papers (13)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    The authors propose a multichannel model for saturation recording which includes interference from adjacent tracks. In saturation recording, the signal is recorded as a series of flux reversals on the medium. Each track is a pulse amplitude modulated (PAM) signal, where the pulse shape is the system response to a flux reversal. The old information (OI) in each guard band is also modeled as a single PAM signal. The side reading properties of the head are modeled using the reciprocity integral to compute flux transition response. Using a result of D.A. Lindholm (1977) to represent the field of an inductive head, the authors compute specific channel models for various values of misregistration. They determine the pulse shape as a function of the head-to-track registration for each adjacent track and OI track View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A stress-dependent magnetic Preisach hysteresis model

    Publication Year: 1991 , Page(s): 4796 - 4798
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    The authors present a generalization of the classical Preisach model which handles coupled magnetic and mechanical hysteresis. Magnetostrictive materials are known to have hysteresis with respect to both magnetic field H and mechanical stress λ. To test the validity of the model, experiments where the two components H and λ have been verified in many different ways have been performed on Terfenol-D and compared to results computed from the model. Some of these results are presented. This stress-dependent model is found to have an accuracy comparable to that of the classical Preisach model View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Small magnetic patterns written with a scanning tunneling microscope

    Publication Year: 1991 , Page(s): 5289 - 5291
    Cited by:  Papers (4)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    The authors present a technique for writing submicron magnetic bit patterns on double-layered perpendicular recording media by using a scanning tunneling microscope (STM) with an amorphous magnetic tip and observing them with a magnetic force microscope (MFM). The proposed technique provides a very small tip-to-medium spacing on the order of angstroms. It is shown that the magnetization of the extremity of an amorphous tip can be reversed by switching the external field. The possibility of writing magnetic bit patterns in double-layered perpendicular media at a high areal density equivalent to 1 Gb/in2 or more by means of this technology is demonstrated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Matched filter limits and code performance in digital magnetic recording

    Publication Year: 1991 , Page(s): 4594 - 4599
    Cited by:  Papers (6)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (492 KB)  

    Presents a method for evaluating the performance of recording channels and codes for systems with additive spectral Gaussian noise. Starting with a noise-whitened isolated pulse, matched filters are calculated for the amplitude and timing channels which have the maximum signal-to-noise ratio (SNR) and minimum jitter, respectively. In high-density recording systems, the pulse slimming equalization required to control intersymbol interference degrades the SNR and jitter. For the timing channel, a detector SNR is defined whose error statistics are nearly identical to the amplitude channel SNR. Procedures for calculating losses relative to the matched filter SNR are developed that facilitate performance comparisons of both channels. A series of runs for the Lorentzian input pulse and cosn equalized output pulses compares the performance of several modulation codes and detection techniques. Write equalization and partial response type four equalization are examined View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interpretation of magnetic domain images and electron diffraction patterns in Lorentz microscopy

    Publication Year: 1991 , Page(s): 5190 - 5192
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Lorentz TEM (transmission electron microscopy) images and associated electron diffraction patterns of magnetic domains recorded on thin-film media under various conditions are described. Various patterns of deflected diffraction spots are observed, depending on the state of magnetization of the specimen. Black and white contrast in Foucault images is controlled by the position of the aperture and results from both the magnetization distribution in the ferromagnetic thin-film specimen and the fringing fields above and below the specimen. Also shown is the effect of overwrite currents on the domain images View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic recording channel front-ends

    Publication Year: 1991 , Page(s): 4503 - 4508
    Cited by:  Papers (8)  |  Patents (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Readback front-end electronics for both inductive and magnetic recording (MR) heads are investigated. For inductive front-ends, it is shown that the channel bandwidth is determined by the transfer of the induced head voltage to the front-end input terminals. The parameters limiting this bandwidth are calculated. A noise analysis shows that the signal-to-noise ratio can be optimized and gives the parameter values for which this happens. The effect of noise matching of the head to the front-end is demonstrated. For MR front-ends the principles of auto bias and relative resistance sensing are presented. Front-end configurations producing voltage biasing and current biasing are discussed. Two examples of signal conditioning in MR front-ends are given: an on-the-chip equalizer compensating the frequency roll-off introduced by the head cable inductance, and a signal-adaptive circuit for removing thermal asperities View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Terfenol based magnetostrictive diode laser magnetometer

    Publication Year: 1991 , Page(s): 5358 - 5360
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    A simple, rugged Terfenol-based magnetostrictive magnetometer prototype has been developed. Experiments were performed to determine the optimum operating point for the transducer and to study the characteristic of the diode laser sensor. A laboratory prototype has been constructed and evaluated under different field strengths and frequencies. Nonlinear responses were observed and their origin examined. The origin of the nonlinearity was interpreted as a result of running the diode laser sensor at an improper operating point. The device has an ultimate sensitivity of 160×10-6 A/m (=2 μ-Oe) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of acid-base interaction on magnetic dispersion containing α-Fe metal particles

    Publication Year: 1991 , Page(s): 4648 - 4650
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    The importance of Lewis acid-based interaction in magnetic dispersions was investigated to understand how it plays a role in determining the dispersion stability and dispersibility of α-Fe metal particles used for high density recording media. To prevent aggregation of metal particles, surface treatment on the passivated oxide surface layer with organic dispersants or metallo-organic coupling agents was carried out to render the metal particle surface more compatible for binders. Being used as binder resins in tape formulation, polyurethanes were found to be predominantly basic, while viny alcohol copolymers were predominantly acidic. It was also found that if basic polymers are chosen as binders, they allow good dispersion of ferromagnetic particles with predominantly acidic surface only, as evidenced by the enhanced absorption of polyurethane onto the surface of α-Fe particles with acidic surfactant treatments View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fluidity and adsorption force of lubricants on thin film magnetic rigid disks

    Publication Year: 1991 , Page(s): 5172 - 5174
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The relationship between the fluidity and adsorption force of lubricant on thin film magnetic rigid disks has been investigated. The adsorption force of lubricants to carbon surfaces increases with an increase in relative dielectric constant of benzene derivative end groups. Disks coated with perfluoropolyether having high adsorption forces show high CSS (contact start/stop) durability. It is found that lubricant layers can be divided into fluid and adsorption parts. The ratios of the fluid to the adsorption parts in the coating affect mechanical durability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interlayer exchange coupling in Co/Cr/Co double-layered recording films studied by spin-wave Brillouin scattering

    Publication Year: 1991 , Page(s): 5064 - 5066
    Cited by:  Papers (5)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Exchange coupling between Co layers through a Cr interlayer in sputtered Co/Cr/Co films has been studied by Brillouin scattering of spin waves by changing the thickness of the Cr interlayer up to 50 Å. The Brillouin spectrum consists of two spin-wave modes due to the Co double-layered structure which depends on the Cr-layer thickness. From the frequencies of the spin-wave modes, the interlayer exchange coupling A12 varying with the Cr layer is determined by using Hillebrands' theory. The exchange coupling through the nonmagnetic layer decreases with increase of the Cr thickness and becomes negligible for the Cr layer thicker than 20 Å. The result is compared with the media noise in double-layered CoCrPt alloy films with a Cr interlayer View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Improvement on error rate performance for FM recording code

    Publication Year: 1991 , Page(s): 4464 - 4469
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A partial response (PR) equalization technique for an FM recording code is proposed. First, the noise power spectrum and the eye patterns at the discrimination point for the PR system are compared with those for Veillard's system. Then, the bit-error rates of bit-by-bit decoding and Viterbi coding for these systems are obtained by computer simulation. The results show that the PR system has improved performance, both for bit-by-bit decoding and for Viterbi decoding, over Veillard's system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetic deceleration of metallic spheres

    Publication Year: 1991 , Page(s): 4400 - 4403
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    The author reports the results of an approximate model of the potential of static magnetic fields, producible by permanent magnets, to decelerate spherical metal samples by eddy currents induced in the materials. It is assumed that the velocity of the sample is low enough that the magnetic field diffusion time is significantly less than the time required for the samples to pass through a half cycle of the magnetic field. Thus, the interaction between the sample and the field will be fully resistive, and the sample's kinetic energy will be converted directly into heat by joule heating. The mode incorporates the effects of magnetic field strength and system geometry, and it predicts that a useful braking device can be constructed. The results of the theoretical analysis are also compared against preliminary tests using a laboratory model View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of a new coding scheme for the peak detecting magnetic recording channel

    Publication Year: 1991 , Page(s): 4804 - 4806
    Cited by:  Papers (3)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A code designed for the magnetic recording channel with peak detection is compared with the industry standard (1,7) code. The coding technique produces two different peaks in the readback waveform which differ in both amplitude and phase. The detector for the code must distinguish between two different types of peaks in addition to determining the existence of these peaks. Using a simple linear model, results indicate that the code outperforms a (1,7) coded system for density ratios above a certain critical value. For a Lorentzian transition response and for the measured transition responses from both helical scan tape recorder and a thin film disk system this critical density ratio is approximately 1.5 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of anisotropy in obliquely oriented media

    Publication Year: 1991 , Page(s): 4864 - 4866
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The uniaxial anisotropy energy Ku and angle of the intrinsic easy axis to the perpendicular direction, α, which does not include the effect of the shape anisotropy of the film, of an obliquely oriented medium were analyzed, based on magnetic torque analysis method (β is the angle of the easy axis to the perpendicular direction, which includes the effect of the shape anisotropy of the film) to determine Ku and α in obliquely oriented media on the basis of a non-approximated theoretical calculation. It is pointed out that the β+45° torque analysis method is also applicable to media with an easy axis in the oblique direction View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Interaction of barium ferrite particles with phosphate ester dispersants

    Publication Year: 1991 , Page(s): 4663 - 4665
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    Using the technique of flow microcalorimetry, both the heat and extent of adsorption of commercially available phosphate ester dispersants on Co and Ti doped and undoped barium ferrite particles were measured. To better understand specific chemical interactions between the dispersants and particles, the authors performed XPS analysis before and after adsorption. Experimental results show distinct differences in the reactivity of doped and undoped particles toward the dispersants. The heats of adsorption of phosphate ester dispersants onto doped ferrite particles were as large as -60 kcal/mole, indicating strong chemical interactions in this system. XPS measurements also show evidence for strong chemical interactions between barium ferrite particles and organo-phosphate dispersants View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A high resolution flying magnetic disc recording system with zero reproduce spacing loss

    Publication Year: 1991 , Page(s): 4549 - 4554
    Cited by:  Papers (16)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    A novel method has been developed for reducing the reproduce spacing loss and thereby potentially allowing increased linear densities on a disc media while maintaining a reasonable flying height. A laminated magnetic recording media is composed of a high coercivity layer in which the data signals are stored, and a thin, low coercivity, high permeability overlayer called a keeper layer. A small DC bias applied to the head saturates a section of the keeper layer, forming a virtual gap that is in direct contact with the high coercivity storage layer. This virtual gap functions as a transducing zone that enables a signal flux to be transferred from unsaturated keeper regions to the pole pieces of the flying head. Experimental results show that a considerable reduction, if not elimination, of the reproduce spacing loss is achieved using the keepered disc. Additionally the keepered disc virtual gap was found to be about 10% smaller than the physical gap in the flying head that induced it. A series of simulations were conducted using finite difference models which confirmed the trends observed in the experimental data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of electromagnetic systems

    Publication Year: 1991 , Page(s): 4509 - 4515
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Modeling techniques are presented for simulation of hybrid (partly electrical, partly magnetic) networks on electrical network simulators. The frequency dependence of the permeability is modeled by a relaxation description, which leads to frequency-independent component values in the network model. The hybrid models can be used for analyses in both the time and frequency domain and for noise analyses. The modeling techniques are applied to a ferrite ring and a ferrite head View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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.

Full Aims & Scope

Meet Our Editors

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