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Magnetics, IEEE Transactions on

Issue 1 • Date January 1987

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Displaying Results 1 - 25 of 80
  • [Front cover and table of contents]

    Publication Year: 1987 , Page(s): 0
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    Freely Available from IEEE
  • Acknowledgements and exhibitors

    Publication Year: 1987 , Page(s): 8
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    Freely Available from IEEE
  • Magnetic recording media '86 highlights

    Publication Year: 1987 , Page(s): 6 - 7
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    First Page of the Article
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  • Information storage technologies -- Some recent trends and current prospects analysed from the media manufacturer standpoint

    Publication Year: 1987 , Page(s): 9 - 15
    Cited by:  Papers (1)
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    Three years after the FERRARA meeting in 1983, the PARMA MRM conference was an opportunity to analyse the current trends of the information storage industry. The impact of the insane competition between media manufacturers during the three last years has now come to a point where this problem also concerns the future of new recording technologies. Factors of merit of modern mass storage systems cannot be based exclusively upon technical criteria. A survey of main trends in magnetic and optical recording is proposed with consideration to some technical and the non technical parameters. View full abstract»

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  • Co-modified pigments in magnetic recording

    Publication Year: 1987 , Page(s): 16 - 21
    Cited by:  Papers (13)  |  Patents (3)
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    This paper surveys the physical properties and storage performance of the class of 650 Oe pigments, which are presently mainly being used for home video, high-quality audio and will in the future be intended for high-density digital storage applications. The temperature dependence of coercivity, the change of coercivity by annealing of a sample in a magnetic field and various aspects of the switching field distribution are shown up in detail. The different data are discussed within a newly developed comprehensive model of Co-modified particles. The model correlates morphological and chemical data with physical properties and storage performance, especially print-through data and erasability effects. View full abstract»

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  • Hexagonal ferrite particles for perpendicular recording prepared by the precursor method

    Publication Year: 1987 , Page(s): 22 - 24
    Cited by:  Papers (3)
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    Single domain MFe12O19(M=Ba Sr) hexagonal ferrite particles have been prepared by the precursor or liquid mix technique. It is shown that single phase samples with different mean diameter and diameter to thickness ratio may be prepared by modifications of thermal treatments. It is shown as well that surface spin canting has been formed and that the magnetocrystalline anisotropy is reduced by the platelet-like shape anisotropy. View full abstract»

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  • Barium ferrite magnetic recording media

    Publication Year: 1987 , Page(s): 25 - 28
    Cited by:  Papers (6)
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    Barium ferrite particulate media have generated a lot of interest for advanced magnetic recording applications because they offer the potential to combine high recording densities with relatively low manufacturing cost. They consist of small (sub-tenth micron) plateletshaped particles with competing orthogonal anisotropies (crystalline and shape) of comparable magnitude. These anisotropies, along with the quasi-perpendicular characteristics of the barium ferrite coatings impart to them many subtle and surprising properties, requiring a careful and judicious choice of parameters for each application. The choices include the aspect ratio of the particles, their coercivity, the particle-to-binder loading, and the degree and direction of magnetic orientation. The problem areas include dispersion and orientation of the particles, overwrite characteristics of the coatings, thermal coefficients of the magnetic parameters and maintaining media coercivities at moderate levels. I this paper, we discuss the effect of the particle and coating parameters on the ensuing magnetic and recording properties of the media, and the types of choices that should be made to minimize the impact of some of the potential problems mentioned above. View full abstract»

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  • Preparation of M- and W-type hexaferrite particles by the glass crystalization method on the basis of the pseudo-ternary system Fe2O3- BaO - B2O3

    Publication Year: 1987 , Page(s): 29 - 32
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    The preparation of M- and W-type Ba-hexaferrite particles by the glass crystallization method was investigated. For this purpose that part of the pseudoternary phase diagram Fe2O3-BaO-B2O3was elaborated in which primary crystallization of BaFe12O19occurs. This three-dimensional region was found to be located within the triangle Fe2O3-BaB2O4-BaFeO2,5. The lowest temperature of primary crystallization of BaFe12O19is close to 800°C near the composition 55 mol% BaO, 20 mol% B2O3and 25 mol% Fe2O3. Using the knowledge of that system it was also possible to synthesize W-type Ba-hexaferrite particles (BaZn2Fe16O27) by the glass crystallization method. Magnetic data of M- and W-type hexaferrite pigments prepared by that method are given. Particle size from a tenth of a micron to more than ten microns was obtained. View full abstract»

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  • Duplex reactive fluorocarbon films with spin-off resistant characteristics

    Publication Year: 1987 , Page(s): 33 - 35
    Cited by:  Papers (5)  |  Patents (1)
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    As a group, fluorocarbons are by far the most common disc lubricants used in rotating storage memories. They possess excellent properties including chemical inertness, low surface tension, low volativity and moisture repellancy. They have, however, one serious limitation: the continual loss of lubricant from the rotating disc surface due to centrifugal migration. This leads to increased head to disc interference and may eventually cause complete failure of the head-disc assembly (HDA) unit. A unique solution to this problem is described in this paper. It was arrived at by combining two fluorocarbon films, one chemically and permanently bonded to the media surface, the other a normally applied lubricant which is overcoated onto the primed disc surface. These duplex films retain the excellent lubricant properties of the single film but dramatically reduce the lubricant loss by spinoff. Experimental data for duplex and single lubricant systems are presented including spinoff curves, stiction and friction measurements and start-stop wear testing. Finally, a mechanism based upon polymer chain entanglement is proposed to explain the retention of lubricant in this newly discovered system. View full abstract»

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  • Improved quality chromium dioxide particles

    Publication Year: 1987 , Page(s): 36 - 38
    Cited by:  Papers (1)
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    Improvements in chromium dioxide particle properties and performance have been achieved by altering the synthesis process. Solubilization of seed crystal precursors during the paste premix stage of the process led to improved friability, dispersibility, and tape noise and outputs in audio and video formats. The improvements are attributed to the presence of fewer aggregates and to narrower crystal size distribution. Both factors accrue from the more uniform crystal growth conditions provided by solubilization of the seed crystal precursors. View full abstract»

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  • The effect of annealing on the structure of cobalt modified iron oxide particles. Part II

    Publication Year: 1987 , Page(s): 39 - 41
    Cited by:  Papers (3)
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    A new high coercivity cobalt modified iron oxide particle series has been prepared by annealing in a nitrogen atmosphere. The dependence of coercivity (Hc), Hc-aging, temperature dependence of Hc, and magnetic tape properties have been studied as a function of annealing temperature. X-ray photoelectron spectroscopy (XPS) has been used to correlate the changes in magnetic properties to the cobalt concentration gradient near the particle surface. As in Part I of the study, most of the changes observed are consistent with diffusion of cobalt from the surface into the particle core. View full abstract»

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  • High-field magnetism in non-polar γ-Fe2O3recording particles

    Publication Year: 1987 , Page(s): 42 - 44
    Cited by:  Papers (3)
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    Fine γ-Fe2O3particles produced by a process which involves hydrothermal conversion of iron hydroxides to α-Fe2O3have been investigated. Such particles appear to lack pores or dentrites which cause internal magnetic poles, and exhibit superior properties for magnetic recording. Mössbauer spectroscopy, x-ray diffraction, and transmission electron-microscopy were used. The particles were of length 250-500 nm and width 35-50 nm; some samples had cobalt adsorbed onto the surface. Mössbauer spectra were collected at temperatures from 4.2 to 300 K, and in zero and 5 T applied magnetic fields. In general the patterns are typical of bulk γ-Fe2O3. The 300 K spectra of Co-doped samples show sub-patterns of weak intensity associated with at least two distinct additional components with reduced splitting. One of these has Bhf= 45.2(2) T; its origin is suggested to be iron-atoms lying in or close to the cobalt-modified surface. In a 5 T field, the iron-atom moments deviate from the applied field direction by average angles in the range 13-15°. Because the angle for conventional similarly sized γ-Fe2O3is \sim 13\deg , it is concluded that the improved particle morphology does not lead to an improvement in the high-field alignment. View full abstract»

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  • The magnetic moment of CrO2fine particles

    Publication Year: 1987 , Page(s): 45 - 47
    Cited by:  Papers (1)
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    Commercially available, reductively stabilized CrO2particles have a saturation moment of about 80 emu/g or about 80% of the theoretical maximum (100 emu/g) when extrapolated to infinite field. A reduction process used to stabilize the moment accounts for about 10 emu/g or 10% of the difference from the theoretical. The remaining 10 emu/g or 10% difference from the theoretical moment appears to be due to an effectively non-magnetic surface layer. Spin canting, which was previously suggested to cause the reduction, does not appear to be responsible. In addition, supermagnetism was found in batches of very small particles. For example, 48 m2/g CrO2particles (< 150 Å diameter with an aspect ratio of 10) contained about 20% superparamagnetic particles. View full abstract»

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  • Reversible coercivity vs. temperature losses in activated cobalt adsorbed iron oxides

    Publication Year: 1987 , Page(s): 48 - 52
    Cited by:  Papers (11)
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    Most properties of CrO2in magnetic recording media can be matched -and in some cases superseeded- by Surface-Cobalt Modified Iron Oxides. However, while the variation of coercivity with temperature for CrO2is a fully reversible process such variation is partially irreversible for Cobalt Iron Oxides. This relative weakness of Co-iron oxides could become a limiting factor in high density recording systems (such as the IBM 3480 and/or high density microdiskettes). This paper presents experimental evidence on a new Cobalt adsorption system which yealds products whose coercivity losses are fully and completely reversible in the whole range of temperature up to 100°C. In the process of comparing the properties of CrO2vs. Cobalt-Iron Oxides this paper also shows the equivalence of the applicative properties of the two products in terms of output vs. writing current and magnetostrictive effects. View full abstract»

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  • Magnetic alumite disc for perpendicular recording

    Publication Year: 1987 , Page(s): 53 - 55
    Cited by:  Papers (2)
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    Details of making are given of perpendicular magnetic alumite, discs obtained by an aid of anodization with the additional new process named "pore widening" which was effective to control the coercive force. The electrodeposited fine iron needles were in single crystalline state. The perpendicular orientation of magnetization was confirmed. The magnetic recording, characteristics of rigid discs indicated a hilgh potential for use as a perpendicular recording medium. View full abstract»

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  • Influences of sputtering gas pressure on microtexture and crystallographic characteristics of Ba-ferrite thin films for high density recording media

    Publication Year: 1987 , Page(s): 56 - 58
    Cited by:  Papers (6)  |  Patents (3)
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    Ba-ferrite films with small c-axis dispersion angle Δθ50are suitable for ultrahigh density recording media. The dependences of partial oxygen gas pressure PO2and total discharge gas pressure PTotalon the characteristics of Ba-ferrite films were clarified. It was found that there were three regions, where films were composed of single layer of spinel type ferrite(PO2≤0.002mTorr), mixed layer of spinel and magnetoplumbite type ferrites ( 0.003 \leq P_{O2} \leq 0.2 mTorr) and single layer of magnetoplumbite type ferrite (PO2>0.3 mTorr). In the range of P02between 0.005 and 0.2 mTorr, spinel-like ferrite layer plays very important role as an underlayer to decrease the Δθ50of the Ba-ferrite layer. Films deposited at relatively low PO2and PTotalexhibit very smooth surface and Δθ50as small as 2.5\sim3.5\deg . View full abstract»

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  • Effect of pH on crystallographic orientation of plated cobalt films

    Publication Year: 1987 , Page(s): 59 - 61
    Cited by:  Papers (1)
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    Data is presented which contrasts the crystallographic and magnetic properties of films plated at low and at high pH. Plating from a simple CoSO4bath, an abrupt transition in preferred orientation is observed to occur in the region of pH 4, from orientation of the hexagonal c-axis predominantly parallel to the plane of the films below a pH of 4.0 changing to c-axis orientation predominantly perpendicular to the film plane in the pH range 4.0-6.5, together with corresponding changes in magnetic properties. A mechanism based on hydrolysis of Cobalt ions at the cathode interface is proposed to explain this behavior, which is supported by results from plating baths containing Boric acid. View full abstract»

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  • Inhomogeneous Cr concentration as origin of the perpendicular coercivity in Co-Cr films

    Publication Year: 1987 , Page(s): 62 - 64
    Cited by:  Papers (2)
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    Cr segregation at grain boundaries of columnar Co-Cr films as found by different authors may result in obstacles to domain wall motion or even in a breakdown of the exchange coupling between neighbouring grains. Both effects introduce an increase of the perpendicular coercivity. Its magnitude is estimated on the base of two different models: the wall-displacement model for exchange coupled grains and the model of rotational magnetization for exchange isolated columns. There is a satisfying agreement with experimental results for exchange coupled grains whereas the theoretical coercivities of exchange isolated columns are generally too high. View full abstract»

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  • Domains in CoCr investigated by neutron depolarization

    Publication Year: 1987 , Page(s): 65 - 67
    Cited by:  Papers (2)
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    Polarized neutrons (λ = 0.47 nm) are transmitted through RF and magnetron sputtered CoCr films (0.3-5 μm thick) with the polarization vector in the plane or perpendicular to the plane of the film. In the former case we can deduce from the depolarization the effective height heffof the domains and from the angular dependence of the depolarization the section width δ (which is proportional to the domain width) in the remanent states after perpendicular and after in-plane saturation. As expected, heffappears to be larger after perpendicular saturation and for a film thickness h ∼ 400 nm, heffapproaches h. This is attributed to the disappearance of reversed spike domains in the thinnest films. The lower hefffound in magnetron films with a lower surface/bulk coercivity ratio is also consistent with spike domain theory. The section width δ is found to he proportional to hx with x depending on the preparation or magnetic history of the film between 0.6 and 0.8. For magnetron films δ is ∼ 1.5 as large as in RF films of equal thickness, in qualitative agreement only with the fact that K1is twice as large as for RF films. View full abstract»

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  • Control of coercive force of Co-Cr sputtered films

    Publication Year: 1987 , Page(s): 68 - 70
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    The role of c-axis orientation of the crystallites in the sputtered Co-Cr thin films has been investigated aiming for the control of the coercive force of the film. It has been confirmed that the c-axis orientation plays a very important role to control the coercive force, Hc \perp and Hc \parallel . When the c-axis of the film is well oriented, only Hc \perp changes with the increase of the substrate temperature Ts leaving Hc \parallel rather constant. However, both Hc \perp and Hc \parallel change together with the increase of Ts when the film is poorly oriented. It has been considered that Ts is only the factor adjustable for controlling Hc of the films, but the results in this study indicate that the c-axis orientation is the another factor to control Hc \perp and Hc \parallel , separately. View full abstract»

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  • Compositionally modulated Gd-Co amorphous films by bias sputtering

    Publication Year: 1987 , Page(s): 71 - 73
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    The new sputtering technique was developed in which film deposition and ion bombardments were performed alternately and independently. By the technique, amorphous Gd-Co films were prepared with various thickness of the periodically deposited layers (td). It was confirmed that ion bombardments by applying the bias of -100 \sim-200 V change the composition within only about two atomic layers near the surface. The films with the compositional modulation of amplitude of a few at.% were synthesized in the range of tdlarger than about 0.6 nm. A large anisotropy perpendicular to the film plane appeared abruptly at tdlarger than 2.0 nm and the anisotropy decreased as tdincreased. The results obtained may be interpreted qualitatively by the improved pair-ordering model. View full abstract»

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  • CEMs and Faraday rotation study of γ-Fe2O3- Fe3O4films obtained by a new pyrolisis technique

    Publication Year: 1987 , Page(s): 74 - 76
    Cited by:  Papers (1)
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    Thin film iron oxides prepared by a new pyrolisis technique are studied by means of CEM spectroscopy and Faraday rotation measurements. It is shown that Fe3O4spinel oxides are obtained when the deposition is performed under Ar atmosphere. These spinel-ferrite films present an important magnetization component perpendicular to the film plane. It is also shown that the Fe3O4films are converted to γ-Fe2O3by oxidation in air while retaining a uniaxial magnetic anisotropy. We interpret this induced magnetic anisotropy as arising from a magnetoelastic coupling with the substrate. Faraday rotation hysteresis loops confirm the existence of a strong induced uniaxial magnetic anisotropy in these films. View full abstract»

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  • Simultaneous substitution of Co2+and Zn2+ions in submicronic acicular γ - Fe2O3particles

    Publication Year: 1987 , Page(s): 77 - 79
    Cited by:  Papers (4)
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    In iron sesquioxide of acicular shaded γ-Fe2O3simultaneous substitution of Co2+and Zn2+ions leads to the formation of mixed-defect ferrites and modulation of magnetic properties is of interest for their application to high density magnetic recording. It is shown that the coercive force, remanent magnetization and saturation-magnetization are controlled by a judicious choice of the contents of Co2+and Zn2+, while it is indispensable to optimize the morphological features like the average size of the crystallites, the shape, the size and texture of the particles. A high value of coercive force (650-700 Oe) and of the remanent magnetization (35-45 emu/g) had been obtained with a minimal content of cobalt ions (Co2+= 2.5 to 3% by wt.) permitting limits to the magnetocrystalline anisotropy of these compounds and their thermal variation near the ambient temperature. The influence of the zinc content had been systematically studied notably in relation to its effect on the structural, morphological and magnetic properties of the ferrites. View full abstract»

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  • Morphology of ultra fine iron particles

    Publication Year: 1987 , Page(s): 80 - 82
    Cited by:  Papers (1)
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    Variation in morphology of the silica thin film coated ultra fine goethite particles(length:140 nm, aspect ratio:11/1, surface area:95 m2/g, SiO2/Fe:3.4 wt%) in the process of decomposition and subsequent reduction was examined by means of gas adsorption and electron microscopy. Microporous hematite particles, prepared by decomposition of the silica-coated ultra fine goethite particles at 250°C in vacuo, were subjected to heat-treatment at 700°C in air to form the nonporous hematite particles without degradation of the acicular shape. The highly acicular and nonporous ultra fine iron particles(length:110 nm, aspect ratio:10/1, surface area: 80 m2/g) were obtained as a result of shrinkage of the particles in the reduction process of the nonporous hematite particles at 400°C in hydrogen gas. Coercivity of the ultra fine iron particles was 1660 Oe. View full abstract»

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  • Thermal stabilization processes on CrO2powders modified with Fe dopants

    Publication Year: 1987 , Page(s): 83 - 85
    Cited by:  Papers (1)  |  Patents (1)
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    Various thermal treatment are employed on CrO2powders doped by 2.23% (by weight) of Fe and 0.30% of Sb in order to prevent the chemical degradation of the particle surface. Generally, these treatments do not influence the magnetic properties of pure CrO2powders, but in the case of CrO2doped with Fe they can produce a degradation of the magnetic properties, reducing the improvements due to the dopants. Several magnetic and structure parameters of the doped powders are examined after the thermal treatment; particularly: the coercivity, the squareness ratio, the switching field distribution, the rotational hysteresis, the X-ray diffraction peaks. The degradation of the magnetic properties is correlated to the crystal deterioration because of the Fe dopant migration. On experimental basis, suitable conditions of the thermal stabilization process are established in order to avoid an excessive reduction of the magnetic advantages produced by the Fe dopants. 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.

Full Aims & Scope

Meet Our Editors

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