By Topic

Magnetics, IEEE Transactions on

Issue 5 • Date Sept. 1989

Filter Results

Displaying Results 1 - 25 of 363
  • Comments on "Minimizing power dissipation in a disk file actuator" by E.S. Cooper

    Publication Year: 1989 , Page(s): 4353 - 4354
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (146 KB)  

    The seek control problem that arises in the abovementioned work (see ibid., vol.24, p.2081-91, 1988) is formulated as an optimal control problem with constraints relating directly to specified design limits on input magnitude and power dissipation. The resulting control is optimal for a given peak-to-average power ratio. Power-optimal control and time-optimal control are special cases of this type of control.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Recording experiments on rare-earth transition-metal thin films are studied with Lorentz microscopy

    Publication Year: 1989 , Page(s): 3524 - 3529
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    Domains written thermomagnetically under recording conditions in rare-earth transition-metal thin films are studied with Lorentz microscopy. A novel technique in which the magnetooptical layer is deposited on specially prepared silicon wafer disks provided with Si3N4 windows is described. This technique allows direct observation of the written domain patterns in the electron microscope. It is demonstrated that the nucleation process plays a crucial role when writing in TbFeCo. Different compositions having different temperature dependences of the magnetic properties lead to markedly different domain-formation behavior. With the detailed insight into the shape and structure of domains obtained by Lorentz microscopy, carrier and noise levels obtained from recording experiments can be understood. This is demonstrated with data on GdTbFe. It is shown that magnetic-field modulation, apart from the advantage of direct overwrite, offers the possibility of very-high-density recording View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magneto-resistance, stress effects, and a self-similar expansion model for the magnetization process in amorphous wires

    Publication Year: 1989 , Page(s): 3620 - 3622
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The outer shell magnetization process was investigated from the point of view of its effects on longitudinal and transverse magnetoresistance (MR), magnetization, and domain structure observations as well as their stress effects for a Fe77.5Si7.5B 15 amorphous wire with a diameter of 125 μm prepared by rapid quenching in rotating water. The unusual behavior of the initial negative slope observed in the longitudinal MR is explained in terms of a realistic domain structure. A self-similar expansion model is proposed to explain the dynamical response of such a structure under applied fields and/or tensile stresses. It is suggested that the zig-zag domains of the outer shell are stabilized by a square closure domain which expands uniformly while maintaining a self-similar shape up to a threshold field of about 20 Oe and then deforms towards the saturation magnetization. However, this domain structure was destroyed or much deformed by a tensile stress along the wire axis of about 170 MPa in the sample. Such a critical stress depends on the diameter, quenching conditions, alloy composition, etc. This behavior and stabilization of the zig-zag domain by the closure domains give a novel mechanism for the magnetization processes which follow the re-entrant reversal, and are thus useful for the understanding of re-entrant reversal phenomena themselves View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study of the coercivity for Nd-Fe-B-Ga sintered magnets

    Publication Year: 1989 , Page(s): 3429 - 3430
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The Ga-composition dependence of the Curie temperature, the anisotropy field, and the coercivity are studied for Nd-Fe-B-Ga sintered magnets. It is shown that a smaller addition of Ga atoms increases not only the Curie temperature but also the coercivity. A rise in coercivity does not result from the change of anisotropy field for Nd16Fe77B7-xGax sintered magnets. It is also found that the coercivity for a Nd16Fe 77Ga2B5 magnet, which has lower B content, is controlled by nucleation whereas for the magnet Nd13.5 Dy1.5Fe75Al2B8 (iHc=18 kOe), two kinds of coercivity mechanisms (pinning and nucleation) coexist View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The synthesis of Sm2(Co,Fe,Zr)17 high energy product, 16 to 30 MGOe, thick sputtered films

    Publication Year: 1989 , Page(s): 3788 - 3790
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    Sputtering methods have been developed that allow the synthesis of Sm2(Co,Fe,Zr)17-type films with thicknesses between 20 to 100 μm that exhibit an in-plane static energy product on the order of 20 MGOe. To achieve the energy product range of interest it is necessary that the films exhibit crystallographic texturing such that the crystallite c-axes preferentially lie in the plane of the substrate. This requires that the films be directly crystallized onto heated substrates. It has been found necessary to precoat the sapphire substrates with a boundary layer of oxidized Al-Al2O 3 to allow the films to be strongly adherent to the substrate. Films have been made for a very narrow range of sputtering conditions that exhibit no X-ray reflections that correspond to the presence of crystallites with c-axes skewed out of the film plane. It is also necessary that the films be deposited so as to prevent the formation of a noticeable columnar growth pattern. The presence of such a columnar growth pattern introduces porosity that lowers the effective magnetization value. Such high-energy product films are potentially useful for the fabrication of small-scale integrated electromagnetic components View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Stability of one dimensional steady state domain wall motion

    Publication Year: 1989 , Page(s): 3854 - 3856
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The magnetization configuration and stability limits of one-dimensional domain walls with orthorhombic anisotropy and an applied field normal to the wall are studied in steady-state motion. The calculations are carried out directly on the directional sphere in the lossless instance. The Walker breakdown mechanism, in which the motion breaks down simultaneously along the entire wall profile, is replaced by three distinct mechanisms: domain instability in which the wall motion breaks down asymptotically far from the center of the wall, and two types of domain-wall instability in which the breakdown occurs within the wall. The two types of domain-wall instability are distinct in that only one is identified by Jacobi equation analysis View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetostriction measurements for amorphous wires

    Publication Year: 1989 , Page(s): 3623 - 3625
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Novel accurate and stable measurement methods for the magnetostriction constant λs and the induced anisotropy constant Ku are presented for amorphous wires. The two constants are theoretically expressed using a magnetization rotation model with or without tensile and compressive stresses. Values of flux densities Bs, B r, and Bm are estimated, observing 60 Hz BH characteristics of the amorphous wire to which a compressive stress is applied in order to realize the magnetization rotation behavior. Measured variations of λs and Ku of wires of different compositions for heat treatments with or without stresses are given. A figure of merit for stress sensor constitution is proposed as λsB s/Ku, a maximum value of which is obtained due to a compressive stress anneal for Fe-rich wires View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A variable reluctance sensor

    Publication Year: 1989 , Page(s): 3827 - 3829
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (104 KB)  

    The author presents the characteristics and the performance of a novel variable-reluctance sensor. He describes two designs for this inductive transducer which are very easy to realize. They are based on two shapes, both of which generate a sinusoidal variation of the air gap and therefore an inversely sinusoidal variation of the reluctance. The first shape utilizes an off-centering rotor, the second a buckled surface. The performance, resolution (15 bits), and accuracy (±3 of arc) of the prototype are presented. The prototype demonstrates the good measurement performance of this low-cost shaft-angle transducer, as well as its robustness, reliability, and stability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of applied field inhomogeneities on the magnetization reversal of elongated γ-Fe2O3 particles

    Publication Year: 1989 , Page(s): 3662 - 3664
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    A detailed micromagnetic study of the effects of nonuniform applied fields in elongated particles is given. As a representative case the magnetization reversal is studied in the presence of a recording head field. The investigation is restricted to an important subproblem: the single particle in an inhomogeneous applied field. This case is also interesting with regard to the development of ultrahigh-density recording systems. Reversible and irreversible magnetization processes are computed for the limit of small and large exchange coupling. Results are presented for both longitudinal and perpendicular media View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structure and magnetic properties of Nd2(Fe1-xCox)14B1-y Cy alloys

    Publication Year: 1989 , Page(s): 3298 - 3299
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    The reorientation temperature and magnetocrystalline anisotropy field (Ha) of Nd2(Fe1-xCox)14B1-y Cy in the temperature range 200-450 K were determined by AC initial susceptibility measurements and the singular point detection technique, respectively. The temperature dependence of saturation magnetization was measured on finely powdered polycrystalline samples in an extraction magnetometer in fields up to 80 kOe. It was found that the Nd2(Fe1-xCox)14 C (X⩽0.4) series consisted of a mixture of two phases, Nd2(Fe,Co)17Cx and α-(Fe,Co), irrespective of heat treatment schedules. Partial substitution of C for boron led to a slight increase of Ha, whereas substitution of Co for Fe (at low Co concentration) causes an increase of Ha at low temperature. Although the concentration dependence of Ms is reminiscent of the Slater-Pauling curve, no maximum was found at either 1.5 K or 300 K, as one would expect in Fe-Co and Nd2(Fe,Co)14B alloys View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Formation of magnetic grating on steel plates by electron/laser beam irradiation

    Publication Year: 1989 , Page(s): 3830 - 3832
    Cited by:  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    The steels examined were a ferromagnetic carbon steel, S35C (equivalent to AISI 1035), and a nonmagnetic austenitic stainless steel, SUS 304 (equivalent to AISI 304). The gratings formed were magnetized in a 5.4-kOe field and the profile of the vertical component of magnetic flux leakage from each magnetized grating was measured. Changes of microstructure and mechanical strength of the beam-irradiated portions of the steel plates were also investigated. The measurements of the leakage flux profiles revealed the existence of remanent magnetism in the gratings. Metallographic and mechanical-hardness examinations showed that the original mixed ferrite/pearlite phase in the S35C steel was changed to martensite by beam irradiation. This increased its mechanical hardness. It was also determined that small grains of the ferrimagnetic ferrite phase were precipitated in the base of the nonmagnetic austenitic phase in the SUS 304 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An improved magnetic position sensor

    Publication Year: 1989 , Page(s): 3833 - 3835
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    Significant improvement in the overall performance of a position sensor based on the effective permeability of a slender ferromagnetic core element is obtained by modifying the construction. The need for a bias field is eliminated by tilting the polarizing magnet(s) in the magnetic-core plane. The resulting longitudinally asymmetric magnetizing fields divide the core element into oppositely polarized regions having unequal intensities of remanent magnetization with distinctive incremental permeabilities. The magnet position determines the relative length of each region and therefore the effective permeability of the core element as a whole. When the effective permeability is determined from the inductance of a solenoid wound over the core element, nonlinearities due to various end effects and the magnet's proximity can be corrected by local variation of the winding pitch. Application-specific nonlinear transfer functions are also obtained in this manner View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A study on magnetization model for particulate media

    Publication Year: 1989 , Page(s): 3665 - 3667
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The leakage magnetic field of a single γ-Fe2O3 particle is observed by electron holography to be approximately single domain and uniaxial. On the basis of this result, a vector magnetization model is introduced in which curling and rotation in unison modes for a prolate take place. Using this model and the particle size and orientation distributions in γ-Fe2O3 particulate media observed by high-resolution scanning electron microscopy, M-H loops and Hc-Ω characteristics of the film are calculated. Moreover, read/write simulations of the isolated pulses are performed using the finite element method. These calculated results agree fairly well with measurements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Spectral analysis of electromagnetic vibrations in DC machines through the finite element method

    Publication Year: 1989 , Page(s): 3590 - 3592
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    The authors describe the FLUXMECA software package for calculating the mechanical transfer function of electrical machines, either static or with moving parts, for applied currents of any waveform. The solution method is based on magnetic sampling in space and time and on mechanical analysis in frequency space. The magnetic field is computed by the classical finite-element method for static machines coupled with the boundary integral method for machines with moving parts in order to take movement into account. Mechanical computations are performed by the finite-element method. The calculation of excitation forces, which uses a surface distribution of the local force density on ferromagnetic materials, leads to a correct determination of the resulting mechanical response of the structure. Consequently, the determination of the Fourier spectrum is quite easy even if it requires a large volume of data to take into account the movement of the rotor and its shaft View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The influence of rare earth (RE) constituents on the magnetic and optical properties of RE-FeCo thin films

    Publication Year: 1989 , Page(s): 3746 - 3748
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The polar Kerr effect and perpendicular anisotropy of various rare-earth (RE)-FeCo films were measured and were found to have different dependencies upon the RE composition of the films. The polar Kerr effect was found to be largest for those films where Gd dominated the RE composition. Also, the polar Kerr effect was seen to decrease monotonically as increasingly heavy RE elements from Gd to Er dominated the RE composition. The other RE elements in this range are Tb, Dy, and Ho. In contrast, the perpendicular anisotropy of the same films was seen to be largest when Tb dominated the RE composition. The perpendicular anisotropy decreased rapidly when Gd was substituted for Tb and decreased gradually when increasingly heavy RE elements were substituted for Tb. It is also shown that the dependence of the Curie temperature upon RE composition for these RE-FeCo films correlates strongly with the dependence of the Curie temperature upon composition for pure RE alloys over a similar range of elements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Natural frequencies of sliders and transducers used to detect slider-disk contacts

    Publication Year: 1989 , Page(s): 3725 - 3727
    Cited by:  Papers (12)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    The natural frequencies of the various transducers and sliders were studied by finite element modeling and experimentation. Finite element analysis shows that the lowest ringing frequency of a 3370 slider is around 310 kHz. This value has been verified by the laser Doppler vibrometer and AE (acoustic emission) measurements. It is determined that the lowest natural frequency of a mini-Winchester slider is around 130 kHz. The 140-kHz frequencies reported in the literature using the two-rail sliders with piezoelectric transducers attached to the slider and the 160-kHz frequencies reported using AE transducers attached to the suspension mount are associated with the natural frequencies of these transducers and not of the sliders View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 2-dimensional observation of recorded magnetization transitions in perpendicular recording

    Publication Year: 1989 , Page(s): 4162 - 4164
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Two-dimensional magnetic transition shapes written in a perpendicular recording medium were studied using a large-scale model which simulates a system consisting of a single-pole head and a double-layer medium. The magnetization distribution shapes are calculated from the measured stray field distribution on the surface of the recording medium. The authors describe the experimental method and the results derived for a large-scale medium. They observed a tail-like structure at the corner of the track and transition edges along the track, which can be interpreted as the effect of the demagnetization field from the DC-erased magnetization. The shape of the track edge is similar to that of the transition edge, which suggests that perpendicular recording is suitable for narrow-track recording View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic field near a concrete wall during a lightning stroke

    Publication Year: 1989 , Page(s): 4006 - 4008
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    The authors highlight the electromagnetic behavior of a lightning protection system with reference to a concrete wall making use of iron rods as vertical down conductors and horizontal equipotential conductors. The electrical model is obtained by dividing each rod into elementary cells, each represented by an equivalent symmetric π network. During a lightning flash the current flowing through each cell and the magnetic field generated by it can be computed at any point in space at any time. The performance of this structure is compared with that of a conventional lightning protection system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetization process in NiFe alloys with vanishing anisotropies

    Publication Year: 1989 , Page(s): 3973 - 3975
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    The magnetization process in NiFeMo alloys with vanishing anisotropies and variable grain sizes has been investigated through complementary hysteresis loop studies and Barkhausen effect experiments. It is found that the coercive field Hs-1 , while the constants a and b of the Rayleigh law I=aH+bH2 are proportional to s and s2 respectively. Barkhausen noise power spectra show the same shape as in materials with significant anisotropy, i.e. SiFe, even though their amplitudes are two to three orders of magnitude lower. They show a strong dependence on s, approximately decaying as s-2 at high analysis frequencies. The results, though inconclusive, point to domain-wall motion as an important mechanism in the magnetization process of low-anisotropy NiFe alloys View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The temperature dependence of coercivity in cobalt-aluminum fine-particle ferromagnets

    Publication Year: 1989 , Page(s): 3878 - 3880
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    A model based on coherent rotation has been developed to describe quantitatively the magnetic hardening exhibited by heat-treated β-CoAl alloys. The coercivity of these fine-particle ferromagnets was measured over the temperature range from 77 to 757 K and correlated with the calculated values based on the proposed model. The model incorporates both crystal anisotropy constants, K1 and K2, as well as the shape anisotropy of the particles. The unusual minimum observed at elevated temperatures is predicted by the model and shown to derive directly from the interplay between the crystal and shape anisotropies of the elongated single-domain particles. The magnetic properties of the particles are shown to depend critically on the crystallography of the solid-state transformation and particle morphology, which were determined by transmission electron microscopy and diffraction View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Substrate effects on the magnetic characteristics of sputtered media

    Publication Year: 1989 , Page(s): 3887 - 3889
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The magnetic characteristics of C/CoNiCr/Cr longitudinal recording media on NiCuP-plated substrates and various Al-Mg alloy substrates were investigated and compared with the conventional NiP-plated substrates. It was found that the media on the NiCuP-plated substrates had a flatter envelope waveform. The error characteristics of the media directly sputter-deposited on the Al-Mg alloy substrate made from high-purity Al ground metal or by rapid solidification were almost the same as those of the media on the NiP substrates. The Al-Mg alloy substrate finished by electrolytic abrasive polishing exhibited a higher resistance to corrosion than that finished by diamond turning View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • MR vector sensor with trimmable sense axis direction

    Publication Year: 1989 , Page(s): 3836 - 3838
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    Magnetoresistive bridge sensors fabricated from thin-film Permalloy elements are biased by mutually opposing fields on adjacent arms of the bridge using integral thin-film bias magnets. The sensors have excellent vector response and good linearity in applied fields up to 1.5 Oe. It is shown both theoretically and experimentally that the axis of peak sensitivity is not aligned with any geometric edge of the sensor pattern but can be adjusted by varying the bias field. This ability to trim the sense-axis direction is discussed in relation to the production of three-axis sensor systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A servo method for a large-capacity floppy disk drive with downward compatibility

    Publication Year: 1989 , Page(s): 3375 - 3377
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A novel servo method, in which a linear voice coil motor (LVCM) with a simple optical scale is controlled by a μCPU, has been developed. It has a downward read-compatible mode with 135 tracks/in (TPI) and a large-capacity 16-MByte mode with 542 TPI, and it achieves an average seeking time of 25 ms. The drive is expected to be used in such applications as peripheral memories and hard-disk-drive back-ups View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Recorded magnetizations and magnetic fields in media derived by computer simulation

    Publication Year: 1989 , Page(s): 3668 - 3670
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    The parameters of magnetic media dependences of the half pulse width, PW50, and output voltage of isolated pulse, E 0, were investigated using computer simulation. It was found that the squareness in the x direction (Sx) dependences of PW50 and E0 are different from the saturation magnetization dependences of PW50 and E 0 and that PW50 hardly changes with Sx for high S* (PW50Sx0.04), although it is proportional to Sx0.48 for low S *. The corresponding magnetization and the total magnetic field are also investigated for high Sx and low Sx media in three steps. These are the reversed write current, removed head, and reproducing process steps. It is confirmed that transition regions are formed mainly during the reversed write step View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical modelization of transient current in relay

    Publication Year: 1989 , Page(s): 3593 - 3595
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    The authors describe the application of software for magnetic-field computation to the evaluation of transient current in the coil of a relay. The AZIMUT software package is used to compute the induced current in the coil and the electromagnetic force acting on the mobile part of the relay. This force is introduced in a simple mechanical equation to determine the change of position of the mobile part. The software has been modified to take into account the electromotive force induced by the movement. Some of the difficulties met in coupling the mechanical and electrical problems are discussed. The current measured in a relay fed with a voltage step is then compared to a computed curve. The shapes of the curves are similar. Several reasons for the differences between them are suggested 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