By Topic

Magnetics, IEEE Transactions on

Issue 1  Part 2 • Date Jan. 1997

Filter Results

Displaying Results 1 - 25 of 51
  • Evolution of bicrystal media development

    Page(s): 885 - 890
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1194 KB)  

    A general review of studies on microstructure, magnetic properties and recording performance of bicrystal media grown on single crystal substrates, a NiP/AI substrate and a glass substrate is given. With similar magnetic properties, a direct experimental comparison of recording performance of CoCrPtTa /Cr/NiP films between the media with Cr (200) and Cr (110) textures on glass ceramic substrate is provided. Typically, 5-6 dB SNR improvement is observed for medium with Cr (200) texture from recording densities of 40kfci to 140kfci. Medium with Cr (200) texture has ~100 % bicrystal cluster microstructure and has smaller and more uniform Cr grains. A noise mechanism is discussed that relates the bicrystal microstructure to an effective random anisotropy field magnitude. Micromagnetic simulations show the latter will reduce medium noise when there is relatively large intergranular exchange coupling between the grains. However, when the intergranular exchange coupling is small, the introduction of random anisotropy field magnitude will increase the medium noise. The other noise mechainsm could be due to larger Cr grain size. A bigger magnetic cluster could be formed because more CO alloy grains on a larger Cr grain are coupled together through stronger inner intergranular exchange force, which leads to higher media noise. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A review of finite element open boundary techniques for static and quasi-static electromagnetic field problems

    Page(s): 663 - 676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1588 KB)  

    This paper presents a review of finite element open boundary techniques for the computation of static and quasistatic electromagnetic fields. The underlying assumptions and ideas behind these techniques are outlined and explained. The advantages and shortcomings of each technique are discussed. The goal of this review is to aid those working on numerical solutions of open boundary problems using the finite element method to gain perspectives on the variety of techniques presently available or being developed. This review is also intended to facilitate the communication of numerical techniques between the low-frequency field computation community and those in the high-frequency community View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Scanning magnetoresistance microscopy (SMRM) as a diagnostic for high density recording

    Page(s): 891 - 896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    Scanning Magneto-Resistance Microscopy (SMRM) is a technique which we have developed whereby commercial magneto-resistive (MR) heads are used to both image and record magnetic media. A high resolution, linearized positioning stage is used to raster-scan the recording media (either a hard disk platter or tape coupon) with respect to the MR read/inductive write head. The scanning is performed with the slider in physical contact with the media. Thermal asperities are not present since the contact is continuous rather than intermittent, and the scan speed is slow. This report describes the SMRM hardware, and SMRM measurements of isolated transitions from two different types of MR heads are analyzed and compared to corresponding spin stand data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Media requirements for proximity recording

    Page(s): 908 - 911
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    The tribological characteristics of the magnetic media that are compatible with the proximity recording head-media systems have been evaluated. The media were evaluated in terms of surface roughness, overcoat type and thickness, and lubricant type and thickness. The proximity recording media evaluated included currently available disks with different types of protective overcoat films, namely, nitrogenated carbon, hydrogenated carbon and argon sputtered carbon. The lubricant system had perfluoropolyethers with additives to improve the lubricant stability. The media with low glide and above described material characteristics passed the long term reliability tests View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • DC-free run-length-limited codes for magnetic recording

    Page(s): 868 - 874
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    In this paper, a method to design high-efficiency codes with combined run-length and dc-null constraints is presented. Using the new method, two new dc-free (1,7) codes, with rates of 12/20 and 16/26 were developed. The code efficiencies are 89.31 and 91.6%, respectively. The proposed approach is more general than the technique used to design the existing dc-free d=1 code. The performances of the new codes are also compared with that of the rate 8/10 dc-free (0,4) code. The minimum distance analysis and the bit error rate simulation both show that while at low densities the proposed codes exhibit performance degradation compared to the higher rate (0,4) code, they perform better than the latter as density increases, despite the code rate disadvantage View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analytical solutions describing the operation of a rotating magnetic field transducer

    Page(s): 697 - 702
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    This work presents the analytical solutions describing the operation of a rotating magnetic field transducer used in the eddy current defectoscopy for detecting the long flaws situated parallelly to the inspected piece generatrix. The method uses the expanding of the real transducer's three-phase system into an infinite sequence of axial and longitudinal currents whose intensity is given by a Fourier expansion, estimating the electromotive voltage induced in the transducer. By solving the equation of diffusion for the three media and considering the boundary conditions, the vector magnetic potential is determined for each medium. This work also presents the most important theoretical parameters of the transducer, as well as the experimental graphs obtained for cases of the transducer's applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Temperature dependence of activation volumes in Tb-Fe-Co magneto-optic thin films

    Page(s): 795 - 798
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    In this paper, we present the results of an investigation into the temperature dependence of fluctuation fields, activation volumes, and coercivity in Tb-Fe-Co magneto-optic thin films. Using the model of domain wall dynamics developed by Gaunt (1976), both the temperature dependence of the intrinsic energy barrier distribution and the domain wall pinning regime are examined. The results show that at elevated temperatures, the intrinsic energy barrier distribution changes in a way that assists magnetization reversal, leading to greater activation volumes as the magneto-optic write temperature is approached. Analysis of coercivity as a function of temperature shows that these magneto-optic thin films are subject to a strong domain wall pinning regime View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Iron loss analysis of Mn-Zn ferrite cores

    Page(s): 728 - 734
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (812 KB)  

    Iron loss measurements of Mn-Zn ferrite cores up to the megahertz range are reported. Taking the dc magnetic hysteresis, the eddy, and displacement currents into account, magnetic and electric field distributions in the cores are computed with the cylindrical coordinates and Bessel functions. The computed iron loss due to the magnetic and electric fields is compared with the experimental value at different exciting frequencies. It is noted that the computed iron loss becomes considerably smaller than the experimental at high frequencies. In order to explain the difference between the computed and experimental iron losses, a new magnetic field component yielding a dynamic magnetic loss is assumed and added to the magnetic field intensity of the dc magnetic hysteresis. This assumption is verified by evaluating the iron losses in different size cores composed of the same ferrite material. Displacement current distribution in a ferrite core depends on the cross-sectional area of the magnetic flux path, which brings about the dependence of the frequency characteristics of the iron loss upon core size View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Media tribology optimization for proximity recording

    Page(s): 897 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    The demand for data storage capacity has increased dramatically in recent years. Areal density has been increasing at a 50 to 60% annual compound growth rate. In order to support this growth rate, especially for inductive recording, the magnetic spacing loss between the recording head and the disk must be reduced. The introduction of the general class of “proximity” recording heads has provided the drive designer with a way to mitigate this requirement. However, because these heads allow for continuous or at least semi-continuous head disk contact during drive operation, the formula for successful mechanical performance of the head disk interface has changed. Several areas of tribology must be re-addressed to meet the challenges of proximity recording: texturing must be done in manner which minimizes variation in head/media spacing; the durability and wear resistance of the disk overcoat must be optimized and lubricants with high thermal stability and resistance to catalytic breakdown must be used. The lubrication process itself is another important area of focus to insure proper lubricant conformation and hydrophobic behavior of the finished media surface. The traditional CSS based evaluation of head/media reliability has to be augmented by on-track flyability testing as well as seek based testing. When the tribology system is optimized, on-track flyability testing indicates that head build-up is minimized and neither the recording performance nor the flyability of the head is compromised. Seek based CSS testing and traditional stiction/friction measurements in several environments further establishes the viability of the proximity recording head/media interface View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A quantitative analysis of the separation of aluminum cans out of a waste stream based on eddy current induced levitation

    Page(s): 772 - 781
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1484 KB)  

    Eddy current induced levitation can be employed to separate conducting from nonconducting materials as in the recycling of aluminum products. To investigate magnetic fields, eddy currents, and forces, a multiple strategy involving analytical, numerical, and experimental analysis techniques is implemented. In particular, the configuration of an aluminum can over an arrangement of multiple coils is investigated with a two-dimensional parametric finite element model. The results from these simulations are compared to measurements of a practical levitation device. To establish the fidelity of the finite element model, we applied the method to two simplified geometries of a thick and a thin slab extended over a conducting wire. For the first case, an analytical inverse Laplace-transform model for the eddy current density is developed. For the second case, Lorentz forces exerted on the thin slab are analytically obtained by employing Maxwell's moving image method. In addition, an approximation to the moving image method is derived which can be described by an equivalent resonance circuit View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Laser zone texturing on glass and glass-ceramic substrates

    Page(s): 944 - 949
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (808 KB)  

    A RF driven CO2 laser is used to create laser bumps on glass and glass-ceramic substrates. The resulting bump height is found to be a function of laser parameters such as pulse width, spot size, and pulse energy. Composition, structure and chemical strengthening of the substrates also affect the laser bump topography. Laser bumps on glass-ceramic, non-strengthened glass, or strengthened glass substrates, all exhibit net volume gain. Possible mechanisms for the volume increase include density change due to glass quenched to a subcooled state and/or due to phase transition from the crystalline phase to the glass phase. Stress release may play a role in the case of chemically strengthened glass substrates. The tribological performance of laser texture on glass and glass-ceramic substrates again shows low stiction and low friction build-up View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of disk vibrations on aluminum and alternate substrates

    Page(s): 968 - 973
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB)  

    Aluminum disk platters in 3.5 inch disk drives have been shown to vibrate at their natural frequencies due to air flow excitation. This causes track misregistration that can limit the tracks per inch (TPI). This was shown to be a characteristic behavior of 95×0.8 mm aluminum disks. Measurement methods which are useful in characterizing disk vibrations are described. A laser doppler vibrometer, focused on the disk surface, is used as a velocity sensor to measure force hammer excited frequency response functions, spin-up waterfall plots, and constant speed power spectra. These measurement methods were used to characterize disk platter vibrations on aluminum and alternate substrates in 3.5 inch disk drives. Alternate substrates which have significantly higher stiffness to density ratios (specific stiffness), dramatically reduce the amplitude of these disk vibrations and may provide higher TPI capability View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A hysteresis model for hard magnetic core materials

    Page(s): 723 - 727
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    This paper presents a hysteresis model for hard magnetic core materials which is based on the theory of ferromagnetic hysteresis. Furthermore, an easy technique is demonstrated for calculation of the model parameters from measured data. The mathematical model exhibits all the main features of hysteresis and consists of only nine parameters. Additionally, this model can be realized by a macromodel which is completely compatible with the well-known circuit simulator SPICE2 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical modeling in induction heating for axisymmetric geometries

    Page(s): 739 - 745
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    This paper deals with numerical simulation of induction heating for axisymmetric geometries. A mathematical model is presented, together with a numerical scheme based on the Finite Element Method. A numerical simulation code was implemented using the model presented in this paper. A comparison between results given by the code and experimental measurements is provided View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Texture induced noise and its impact on system performance

    Page(s): 950 - 955
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    In this work, the effect of substrate texture on thin film disk noise and its impact on system performance are systematically examined. The surface structures of thin film disks with different substrate textures are characterized using Atomic Force Microscopy (AFM). Recording spectral analysis and AFM measurement yield disk surface parameters, surface roughness, correlation lengths of the texturing process both parallel and perpendicular to the texture line direction, and cross-hatch angle, all of which are used to characterize the texture noise. An error rate model that includes correlated texture noise is developed. Results are presented for various recorded patterns on disks with different textures. Error rate measurements are also performed. In general, it is shown that an improved system error rate results from a shorter perpendicular correlation length, smaller cross-hatch angle, and a smoother disk surface. The impact of texture on high density recording is also examined and discussed in detail View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A simple transition response model for magnetoresistive heads on thin-film media

    Page(s): 799 - 808
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    Using an analysis similar to that of Potter (1975), we develop a model to describe the transition response for magnetoresistive (MR) heads. The model developed is called the Lorentzian-gap model and includes the effects of shield gap length and MR element thickness. By bringing in a small frequency-independent phase shift, the left-right asymmetry of the transition response and baseline offset for isolated pulse measurements can be modeled. Applying the Lorentzian-gap model to geometrical parameters of the head-media system (HMS) results in a transition response which is close to the measured one. Further improvement of the modeling can be obtained by using the tanh transition model instead of the commonly used arctan model View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Toward a new paradigm for final test of magnetic media for hard disc drives

    Page(s): 962 - 967
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    This paper proposes a new approach to the final test of rigid disc magnetic media. The conventional approach to the final test of magnetic media is to construct an analog of the disc drive consisting of a spin stand and calibrated test heads mounted on air bearing sliders. The properties of the test head (both initial and time evolving) must be accounted for In interpreting the test results. The new approach outlined in this paper replaces the calibrated test heads with a combination of transducers that are maintained at a fixed and relatively large distance from the disc surface. Scanning optical interferometry is proposed as a method of monitoring film integrity. Film integrity is defined to be the absence of asperities with heights greater than a specified maximum and a distribution of flaws (film voids, delaminations, depressions) that meet the requirements of the disc drive manufacturer. It is proposed that the film magnetic properties be monitored directly through the characteristics of the remanent hysteresis loop, rather than inferred indirectly from the recording performance properties of the head-medium ensemble. The guiding principles behind this approach are twofold: 1. The test transducers should never contact the surface of the disc in any way. This requirement preserves the transducer characteristics over long periods of time and reduces or eliminates the need for transducer replacement or re-calibration and minimizes the opportunities for the transfer of contaminants to the disc surface. 2. The measured properties of the medium should be fundamental, and consequently universal. This will simplify the test process and eliminate unnecessary confusion. Thus one measures coercivity and coercive squareness, not overwrite and one measures the flaw size in μm, not as the number of bits in error View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Some improved formulas for the Westmijze head

    Page(s): 820 - 825
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    New analytic formulas for the response of the Westmijze head are presented. The first is calculated by a moment method based on entire domain expansion and test functions which incorporate the correct edge behavior of the field. It is shown that two such functions are enough for getting an excellent convergence of the solution, and that the result agrees with the Westmijze numerical results obtained through a conformal mapping approach. The second formula is based on an interpolation between Karlqvist and the thin head formulas, but in a different way from that which was previously performed. This new formula agrees very well with the results obtained by Westmijze (1953) View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Proximity recording design considerations

    Page(s): 903 - 907
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    “Proximity recording” terminology has been used for the head/media system with the head flying close to the media surface. With current media technology, the glide avalanche is about 1 μin; a head which flies at less than 2 μin has been considered to be in the proximity regime. To date there has been sparse amounts of literature or study on this subject. This paper proposes a new regime of the head/media interface that the proximity recording technology is based upon. It is called the pseudo contact regime. This paper presents new considerations in the designs of airbearing and suspensions for the proximity recording head as well as additional tribological issues View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetic microstructures produced by compositional separation in Co-Cr based alloy thin films

    Page(s): 879 - 884
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1788 KB)  

    Compositional separation (CS) has been observed to occur in Co-Cr based alloy thin films producing fine, Co-enriched, strongly ferromagnetic regions within the crystal grains. This CS exhibits a strong correlation with film magnetic properties and may hold the potential for engineering a “particulate type” magnetic microstructure suitable for high density magnetic recording. In this study, we first investigated the effect on CS of varying several growth parameters, with the aim of better understanding how to control the compositional and magnetic microstructures. In particular, reduction in film thickness was found to be very effective for enhancing CS and producing finer in-grain ferromagnetic regions with less coalescence. We therefore proceeded to perform point magnetic recording in Co-Cr films of various thicknesses and found that, although thinner films do support smaller bits, further studies on control of CS and promotion of magnetic isolation of Co-enriched, ferromagnetic regions will he necessary in order to utilize the full potential of CS View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of amorphous diamond-like carbon-nitrogen films as wear protective coatings on thin film media and thin film head sliders

    Page(s): 926 - 931
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2216 KB)  

    As the magnetic data storage industry strives to achieve ultra-high recording densities requiring fly heights of less than one microinch, the tribology of the head-disk interface (HDI) is a limiting factor in disk drive design. Amorphous diamond-like-carbon (DLC) films have been the materials of choice for wear-protective coatings. Various amorphous DLC type coatings have been developed. The earliest DLC material was DC magnetron sputtered pure carbon films. Recent developments have produced C:H (hydrogenated-carbon) and C:N (carbon-nitrogen) films with greater wear-resistance than pure C film. Our intent is to describe and evaluate the wear-resistance performance of amorphous C:N films as wear-protective overcoats on thin film media and thin film sliders. Both C:H and C:N films have demonstrated superiority over DC magnetron sputtered pure carbon films. The bond character, microhardness, surface roughness features, and the physical nature of initial wear damage influence wear-resistance performance significantly. A recent report of nano-indentor measurements and wear-resistance performance confirmed the superiority of RF diode and DC magnetron Facing Target Sputtering (FTS) of thin C:N coatings over other DLC films View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The coupling of boundary elements and finite elements for nondestructive testing applications

    Page(s): 677 - 681
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    In this paper, the coupling of finite elements and boundary elements, referred to as BEM-FEM coupling, is used to numerically treat a nondestructive testing (NDT) problem based on eddy currents. BEM-FEM coupling is especially well suited for NDT problems because it greatly reduces the discretization effort. A general formulation for such problems involving FEM and BEM is given. The coupling of both methods is achieved using the boundary conditions on the common boundaries between FEM and BEM domains. Only the conducting parts and the exciting coil are discretized by finite elements. The surrounding air space is taken into account by boundary elements. As an example, problem no. 8 (coil above a crack) of the TEAM workshop (Testing Electromagnetic Analysis Methods) is considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Antenna array of circular patches on ferrite substrate

    Page(s): 735 - 738
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The steering properties of a circular patch antenna array fabricated on a yttrium-iron-garnet substrate containing 6×6 elements have been calculated. The formulation assumes the interaction between patch elements can be neglected. Also, the Voigt permeability is used as the effective permeability of the substrate. As such, the steering rate of the radiation beam at 12 GHz is found to be 1.67°/Oe at the broad side direction. Hexagonal ferrites are suggested to avoid permanent external magnetic bias View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-dimensional analysis and magnetic shield design for an electromagnetic valve by an FE code

    Page(s): 692 - 696
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The effect on a proportional electromagnetic valve of a strong external magnetic field orthogonal to the valve's axis and the optimal design of a magnetic shield are presented in this paper. The valve is used to control the gas flow in a fusion device, and its throughput should not be influenced by the external field. The valve, the shield and the perturbing field are modeled by using a 3-D finite-element code based on the reduced scalar potential formulation. An optimization procedure is applied to minimize the volume of the shield together with the effect of the perturbing field on the force produced by the valve's magnetic circuit View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Imaging of media lubricant spacing contributions by readback signal analysis

    Page(s): 974 - 977
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1068 KB)  

    An in situ method for measuring media lubricant spacing contributions in a hard disk drive by analysis of the magnetic readback signal is presented. Amplitude modulation (AM) is mapped over an area of the disk and the image is scaled into equivalent spacing loss using the known transition length and the Wallace spacing loss equation. The first image acquired is used as a reference for all subsequent measurements. Changes in head to media spacing are created by the removal of a localized area of lubricant in the imaged region on the disk. The area is re-imaged and subtracted from the reference in order to measure the resulting changes in head/media spacing. Spacing changes from 0.6 mm to 0.7 mm were measured after either a Freon TF or a trifluoroethanol wash 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