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Magnetics, IEEE Transactions on

Issue 1 • Date Jan. 1990

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Displaying Results 1 - 25 of 90
  • International Conference on Magentic Recording Media (M.R.M. '89) [table of contents]

    Publication Year: 1990
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  • Magnetic media durability: a system's approach

    Publication Year: 1990 , Page(s): 159 - 164
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    A series of test methods has been identified which can be used to evaluate media durability. Test schemes have been developed for high-density flexible disk media. These schemes are combined test schemes of accelerated failure testing and simulated long-term drive testing. The results were correlated to a final system long-term testing. This final test scheme can be extended to any other media durability test method by modifying the operating conditions and system variables, such as flying height, head-media coupling pressure, and speed, and by using an appropriate head penetration for the system. On the basis of the proposed test schemes, a relative ranking of media durability was assessed. In addition, development of a working hypothesis of wear mechanism was attempted by examining physical wear patterns generated at various states of the testing.<> View full abstract»

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  • Simulation of the recording process on Co-Cr layers with a VSM

    Publication Year: 1990 , Page(s): 216 - 218
    Cited by:  Papers (4)
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    To investigate the role of both perpendicular and in-plane head field components in the recording process, a ring head writing transition in Co-Cr layers was simulated with a vibrating sample magnetometer by changing the field strength and rotating the sample simultaneously. The magnetization components parallel and perpendicular to the field direction were measured. An increase in perpendicular magnetization, which can be larger than 50% at the center of the transition, and a decrease in in-plane magnetization were found in the case where the head field was switched compared to the case where the head field was not switched. These effects decrease with increasing maximum field values and with decreasing effective perpendicular anisotropy of the layer. The in-plane field component appears to play an important role: without this component, these effects were not observed. The results are consistent with recording experiments with ring heads and prove that the extra minima in the frequency response described in an earlier paper have a micromagnetic origin View full abstract»

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  • Computer simulation of bias recording. II. Saturation output level

    Publication Year: 1990 , Page(s): 198 - 203
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    For pt.I see ibid., vol.24, p.2235-46, Sept. 1988. Magnetic recording involving the storage of analog audio signals is investigated by computer simulating the write-read process. Using the magnetic and technical data of the recording system, the calculations result in data on output voltages which are in quantitative agreement with corresponding experimental data. As a concrete example for an application of the model the recording of high-frequency audio signals on cassette recorders is analyzed. The influence and the importance of various media and system data on the saturation output level at 10 kHz are determined on the basis of computer simulation View full abstract»

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  • Transmission line modelling with linear and nonlinear magnetic read signal peak displacement

    Publication Year: 1990 , Page(s): 207 - 209
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    A model with linear pulse superposition and nonlinear pulse displacement is suggested for the magnetic recording system. The isolated read pulse is assumed as definite system response to the write current transition. The pulse displacements have been investigated for a high-density flexible disk system. Two types of pulse shift have been identified, both putting the read pulse in an earlier position. Interference with the foregoing transitions and with the following transition are analyzed. Write precompensations that remove the nonlinear pulse displacement from the read signal are derived View full abstract»

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  • Thermomagnetic study of surface cobalt modified iron oxide particles derived from oxalic precursors

    Publication Year: 1990 , Page(s): 57 - 59
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    The cobalt modification of pure γ-Fe2O3 acicular particles by the so-called epitaxial process has been applied to γ-Fe2O3 particles, derived from oxalic precursors. Six elaboration parameters have been taken into account for the slurry heat treatment: cable content, pH, time, temperature, gas flowing into the solution, and surface activation. A thermomagnetic study including in situ annealing treatments and magnetic measurements at various temperatures in the range 20-380°C has been carried out. The results are compared with those of commercial surface-cobalt-modified pigments View full abstract»

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  • On design of Co-Cr perpendicular recording media for usage of a ring-type head

    Publication Year: 1990 , Page(s): 97 - 99
    Cited by:  Papers (6)  |  Patents (2)
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    Co-Cr double-layer media were studied in order to improve perpendicular magnetic recording by using a ring-type head. A very thin semihard back layer (only 100 Å) with a high saturation moment showed a dramatic increase of reproducing output over a wide density region, while the recording sensitivity was also improved. The reproduced waveform with a sharp single peak desirable for actual systems occurs with peak shift as small as that for a single-layer Co-Cr medium. It is supposed that these improvements are caused by reduced demagnetization in the recording process. Design concepts of the media are discussed View full abstract»

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  • Determination of easy axis distribution in recording media

    Publication Year: 1990 , Page(s): 210 - 212
    Cited by:  Papers (4)
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    A method is reported for measuring the effective easy axis distribution of a two-dimensional system, which is more applicable to recording media. The method is applied to cobalt-phosphorus thin films and to a conventional particulate tape. The method provides a useful quantitative analysis of magnetic texture. The measurement displays clearly the effects of interactions in the thin films. These interactions are not so great in the case of particulate media View full abstract»

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  • Magnetic particles derived from iron nitride

    Publication Year: 1990 , Page(s): 60 - 62
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    Due to its high saturation magnetization (σs(0K)≈208 emu/g) and to the ease of obtaining it as a particulate material, Fe4N could be a suitable magnetic material for replacing highly reactive metallic iron pigments (σ s(0K)≈218 emu/g) in high-density recording. Throughout a nitriding process of properly selected precursors Fe4N can be obtained in either of two morphologies: acicular or isotropic. Further protection of the magnetic particles can be ensured through coating of the precursor particles prior to thermal decomposition in NH3/H2 atmosphere or through substitutions with selected elements. The obtained passivated nitrides are characterized by high magnetic properties (Hc≈600 Oe; σs≈150 emu/g) and chemical stability well adapted for use as magnetic pigments for high-density recording View full abstract»

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  • Anisotropy and switching behavior of recording media: comparison of barium ferrite and acicular particles

    Publication Year: 1990 , Page(s): 225 - 227
    Cited by:  Papers (10)
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    The anisotropy and switching behavior of recording media made with barium ferrite platelets are very different from those of media made with acicular magnetic particles. It was found that the ratio of the anisotropy field to the remanence coercivity increases with the diameter-to-thickness ratio (aspect ratio) of barium ferrite particles and is higher than for acicular particles except for platelets of relatively low aspect ratio. Very strong interparticle interactions, tending to make switching easier when increasing the net magnetization than when decreasing it, are found in all barium ferrite samples studied, but not in acicular materials. These interactions do not appear to depend on the aspect ratio of the barium ferrite particles View full abstract»

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  • Lateral magnetic inhomogeneities in Co-Cr layers detected by FMR

    Publication Year: 1990 , Page(s): 33 - 35
    Cited by:  Papers (3)
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    Co-Cr layers deposited on Ge underlayers were investigated with ferromagnetic resonance (FMR). The thickness of the Co-Cr layers and the substrate temperature (Ts) during deposition were varied. Measurements with a vibrating sample magnetometer showed that an increase of Ts results in an increase of both the bulk saturation magnetization Ms and the perpendicular coercivity Hc. The FMR spectra, obtained with the applied field perpendicular to the sample, showed two resonances for all layers. The effective anisotropy field is positive for both resonances. The difference in effective anisotropy field does not change with thickness of the layer, but increases with increasing Ts. From this it is clear that the two resonances are not due to magnetic inhomogeneities in the growth direction, but must be due to lateral magnetic inhomogeneities. Inhomogeneities in composition, resulting in different values of M s, or in geometric structure, resulting in different values of the demagnetizing factor Nd, are the most probable causes of the observed effects View full abstract»

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  • Effects of anisotropy field distributions on magnetic viscosity in particulate recording media

    Publication Year: 1990 , Page(s): 244 - 246
    Cited by:  Papers (7)
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    Theoretical predictions are made of the time-dependent behavior and the irreversible susceptibility of a system of uniaxial, single-domain particles. These results are used to predict the fluctuation field Hf. These predictions are consistent with experimental data on particulate recording media View full abstract»

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  • Influence of porosity and preparation conditions on the properties of γ-Fe2O3

    Publication Year: 1990 , Page(s): 237 - 240
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    A summary is presented of the results of a development program for γ-Fe2O3 particle synthesis which lasted two years and whose aim was the preparation of improved products for magnetic recording. The focus of the exercise was the achievement of improved high-frequency recording characteristics. The goal has been achieved in two steps: the first was the realization of the limits of coercivity attainable by decreasing the particles size, while the second was entirely related to the optimization of the total amount and of the type of porosity and porosity distributions. Important conclusions on the correlation between the size of the switching unit (dependent, among other things, on porosity) and the applicative properties can be drawn from the results View full abstract»

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  • Influence of Cr concentration on recording characteristics of Co-Cr media

    Publication Year: 1990 , Page(s): 103 - 105
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    Investigating the optimum Cr concentration for single-layer Co100-xCrx media with high storage capabilities, the authors have prepared 300-nm-thick layers with x=11-34 at.% Cr by coevaporation on polyimide substrates. The values of M s, Δθ, Hk, and H c (perpen) change slowly and continuously with the Cr concentration x. The degree of the perpendicular crystallographic and magnetic orientation increases with Cr content. Recording tests with VHS-type video heads on 3.5-in. flexible disks, protected by a 40-nm-thick sputtered a-C layer, give clear evidence of a change of the recording mode at ~22 at.% Cr. Only for higher x is the preferred perpendicular recording signal obtained. Due to the use of ring heads, the D50 values show a strong correlation with Hk, whereas no obvious correlation with Δθ and Hc (perpen) is found. For Cr concentrations >25 at.%, D50 values of more than 90 kfci are obtained View full abstract»

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  • Ferromagnetic resonance studies of particulate media

    Publication Year: 1990 , Page(s): 135 - 137
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    Ferromagnetic resonance (FMR) was used to characterize particles dispersed in a nonmagnetic matrix. A sequence of media was prepared in which high-aspect-ratio CrO2 particles were dispersed in a binder matrix with volumetric packing fractions (p) in the range 0.05 to 0.50. The resonant cavity FMR spectrometer operated at 33 GHz with the DC fields at resonance sufficient to magnetically saturate the specimens. No hysteretical effects were observed in the FMR spectra. The FMR spectra of the longitudinally oriented samples were characterized by a single response with an effective anisotropy field favoring in-plane orientation. The FMR spectra for the perpendicularly oriented samples were more complicated, with two observed resonances corresponding to effective anisotropy fields favoring perpendicular and in-plane orientations. As p was increased the response associated with the effective in-plane anisotropy field increased in strength. At p=0.44 the strengths of the two responses were comparable. In unoriented media the response associated with the effective anisotropy field favoring perpendicular orientation was also observed, but at very much smaller strengths. Thus the FMR technique simultaneously provides information regarding in-plane and perpendicular orientations of the media studied. The FMR response has been show to be sensitive to particle misorientation View full abstract»

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  • Transition structure in longitudinal thin film magnetic media

    Publication Year: 1990 , Page(s): 204 - 206
    Cited by:  Papers (5)
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    A two-dimensional micromagnetic model of longitudinal thin-film media is developed using a self-consistent technique. The model is used to investigate the effects of thickness and alignment of easy axes upon hysteresis properties and transition width. The model predicts hysteresis properties close to those observed in real media and shows that in the track direction the transition can be considered to be a smooth function (either arctangent or error function) with superimposed noise. Further results support a widely used relationship for the variation of transition width with media properties and indicate that variations in media properties in the vicinity of the transition can have significant effects on the transition parameter View full abstract»

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  • The Curie temperature of multilayer films with aperiodic compositional modulation

    Publication Year: 1990 , Page(s): 213 - 215
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    The influence of random fluctuations in modulation amplitude, thickness of layers, and width of interdiffusion zones on the Curie temperature of compositionally modulated magnetic films is studied in the molecular field approximation. The Curie temperature has been found to be most sensitive to the fluctuations in the modulation amplitude, which give rise to some kind of localized magnetism in the film View full abstract»

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  • Numerical and analytical modeling of pulsed eddy currents in a conducting half-space

    Publication Year: 1990 , Page(s): 299 - 307
    Cited by:  Papers (22)
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    A weighted-residual-based finite-element model for the computation of transient two-dimensional and axisymmetric magnetic vector potential and eddy-current distributions is formulated. The numerical field predictions are quantitatively tested against two analytical models in the time domain employing inverse Laplace transforms. The basis for the comparison is the determination of the eddy-current distribution in a conducting, nonmagnetic half-space due to either a suspended infinite wire or a suspended current loop. Although the excitation source for both methods is unit step current, the extension to arbitrary transient excitation currents and their corresponding eddy-current responses can be carried out by means of convolution. The resulting numerical temporal and spatial eddy-current distributions at various depths in the half-space are in excellent agreement with analytical distributions, thus quantitatively validating the numerical approach as a viable technique applicable to realistic nondestructive testing situations where field interactions with often arbitrary flaw geometries are of concern View full abstract»

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  • Magnetization reversal in cobalt-surface-coated iron-oxide particles

    Publication Year: 1990 , Page(s): 231 - 233
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    The reduced critical field hn for magnetization reversal by curling of Co-surface-coated iron-oxide particles has been investigated in terms of the atomic layer model (ALM). The most simple case is a rectangular Co distribution (particle composed of a γ-Fe2O3 core and a shell of CoFe2O4). In this case, the results agree very well with the curves calculated by A. Aharoni (J. Appl. Phys., vol.92, p.2576-7, 1987) in the frame of micromagnetism. Furthermore, the influence of Co diffusion into the particle core is taken into account. It turns out that hn first increases considerably with proceeding diffusion. Depending on the anisotropy magnitude, the further alteration may be either positive or negative. This behavior offers the possibility to explain the different temperature dependences of the coercivity before and after annealing View full abstract»

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  • Interaction effects in the remanence curves of CoTi-doped BaFe systems

    Publication Year: 1990 , Page(s): 228 - 230
    Cited by:  Papers (8)
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    Measurements are reported on doped barium ferrite particles produced through chemical coprecipitation. The data are analyzed using a parameter ΔM(H). The behavior of ΔM (H) is reported to be strongly dependent on the doping and consequently the coercivity of the media. High-coercive-force media exhibit a net magnetizing effect in ΔM(H), which changes to a net demagnetizing effect as the coercivity decreases. This is interpreted in terms of changes in the particle interactions introduced through doping View full abstract»

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  • Deposition of Co-Cr films by magnetron sputtering with highly efficient target utilization

    Publication Year: 1990 , Page(s): 112 - 114
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    A new type of magnetron sputtering method which can highly improve the utilization efficiency of a Co-Cr alloy target and suppress the bombardment of high-energy particles to substrate has been developed by forming the uniform magnetic flux confined in front of the target plane. The target utilization efficiencies in area and volume were as high as about 90% and 65%, respectively. The maximum deposition rate was about 0.26 μ/min. All Co-Cr films deposited by using this method were composed of HCP phase crystallites with c-axis orientation Δθ50 ranging from 8 to 14°. The easy direction of magnetization was perpendicular to the film plane. The saturization magnetization Ms and the perpendicular coercivity Hc⊥ are in the ranges of 400-550 emu/cm3 and more than 1000 Oe, respectively. Accordingly, a plasma confining type of sputtering method may be useful for depositing Co-Cr films at a high rate and high target utilization efficiency without damage by plasma View full abstract»

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  • Hexagonal ferrite particles for perpendicular recording prepared by ion exchange

    Publication Year: 1990 , Page(s): 18 - 20
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    Particles of nonstoichiometric M-type barium hexaferrite with the chemical formula BaFe10.5M0.25O17.05 (M=Mg, Cd, Co, Ni, Nd Zn) have been prepared by ion exchange in Ba containing molten salts from precursor ferrites with the β- or β"-alumina structure. The particles possess a plateletlike shape with diameters as low as 0.2 μm and as diameter-to-thickness ratio between 5 and 10. The Curie temperature is close to 470°C. Saturation magnetization values σs up to 64 emu g and coercive fields jHc ranging from 0.5 to 1.5 kOe were found View full abstract»

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  • Effect of media properties on side erase bands

    Publication Year: 1990 , Page(s): 132 - 134
    Cited by:  Papers (2)  |  Patents (2)
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    The erase bands on CoNiCr/Cr longitudinal media with coercivities ranging from 176 to 1390 Oe have been studied using a two-frequency, triple-track profile method. In this method, the two side tracks are recorded at 10 kfci and the central track ranges from 0 to 40 kfci. The write and the erase widths are measured by the Bitter method. Media properties such as coercivity, coercivity squareness, and remanence-thickness product are correlated with the total write width. It is shown that media with high coercivity squareness contribute to a reduction in the width of a side erase band. The magnetic structure of the triple-track profile has been characterized by high-resolution Bitter patterns using scanning electron microscopy, showing domain structures within bit cells and along track edges. The relationship of the erase band to the magnetic structure is discussed View full abstract»

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  • Electrodeposition of magnetic materials for thin-film heads

    Publication Year: 1990 , Page(s): 328 - 332
    Cited by:  Papers (4)  |  Patents (1)
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    Electrodeposition processes have been extensively used in thin-film head fabrication. Extremely fine features can be produced using photolithographic pattern definition followed by electroplating. Permalloy has been exclusively used for the pole material. Some critical aspects, such as film composition, magnetostriction, and stress level, were found to have a significant effect on head performance. Attempts were made to produce single-domain pole structures by lamination to eliminate output instability caused by nonrepeatable domain wall motions. Alternative improvements were brought about by increasing H k and thus reducing the size of the closure domains. Electroplated CoFe and CoFe ternary alloy thin films were found to have very high saturation magnetization (~1.9 T). The CoFe ternary alloy has rotatable anisotropy. Higher permeability can be obtained by electroplating under an alternatingly switched field View full abstract»

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  • Effect of RF substrate bias on crystalline orientation of chromium and magnetic characteristics of 84% Co-16% Cr films

    Publication Year: 1990 , Page(s): 109 - 111
    Cited by:  Papers (2)  |  Patents (4)
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    A report is presented on the conditions for the formation of Cr films with a (110) planar orientation on glass substrates as a function of 13.56-MHz RF substrate bias and sputtering pressure. The Cr (110) planar orientation is dependent on the RF bias voltage as well as on the argon pressure. The developed DC bias voltages from the applied RF substrate bias voltages were measured with respect to ground. At zero bias and at 3-mtorr pressure, Cr films exhibit a weak (110) planar crystalline orientation, but at 10-mtorr pressure they exhibit a random orientation and/or microcrystalline structure. Experimental results show that an optimum bias voltage (-150 V) and pressure (10 mtorr) occur for maximum Cr (110) planar orientation. Co84Cr16 (at.%) alloy films were evaluated relative to their crystalline orientation as a function of RF substrate bias and pressure. The magnetic properties of Co84Cr16 films at optimum bias and argon pressure were evaluated on Cr underlayers with maximum (110) planar orientation on glass substrates View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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