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Magnetics in Japan, IEEE Translation Journal on

Issue 1 • Date Jan.-Feb. 1994

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Displaying Results 1 - 25 of 33
  • [Front cover]

    Page(s): c1
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  • List of contributors

    Page(s): nil1
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  • [Breaker page]

    Page(s): nil1
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  • Table of contents

    Page(s): 1 - 2
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  • Opinion

    Page(s): 3
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  • Microstructure, Magnetic Properties and Noise Performance of CoPt Thin Film Media

    Page(s): 4 - 12
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    CoPt thin films sputtered under high and low Ar pressures were found to have different microstructures. Films deposited under high Ar pressures contained an amorphous phase with segregated oxygen. Those prepared under low Ar pressures exhibited Pt modulation within crystal grains, but did not contain an amorphous phase. The magnetic properties of low-Ar pressure films depended on the perpendicular magnetic anisotropy and on the crystal grain size. In the case of films prepared at high Ar pressures, it is thought that other factors affect the coercivity. The dc-erased media noise decreased with decreasing crystal grain size for both types of media. Transition-related media noise also declined as crystal grain sizes shrank for high-Ar pressure films, but not for low-Ar pressure films. View full abstract»

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  • Study on High Resolution Single-Pole Head in Reproduction

    Page(s): 13 - 20
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    A thin main-pole film is required for high linear densities in perpendicular magnetic recording. In our experiments, Co-Zr-Nb films of thickness 0.08 ¿m had sufficiently low coercivity, but their domain wall structure nevertheless changed from Bloch walls to cross-tie walls at thicknesses under 0.1 ¿m. We found that main poles with cross-tie walls had much lower reproduction sensitivity than did those with Bloch walls. The thinnest main pole with a Bloch wall structure was 0.12 ¿m thick. It resulted in a high D50 of 170 kFRPI, and showed no deterioration of sensitivity. View full abstract»

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  • Preparation of Fe-N Films by Sputtering with He Gas

    Page(s): 21 - 25
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    Fe-N films were deposited on glass substrates by rf sputtering with a mixture of Ar, He and N2 gases. The relationship between the properties of the films and the plasma species was investigated by optical emission spectroscopy analysis. In the Ar+He+N2 plasma, many N2+ molecular ions were generated by He atoms in neutral excited metastable states through the Penning ionization, and contributed to the reaction of Fe with nitrogen. Fe-N films prepared with a very low N2 content of less than 0.03% exhibited a larger magnetization than ¿-Fe. View full abstract»

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  • C Axis Orientation and Magnetic Properties of Barium Ferrite Films

    Page(s): 26 - 31
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    Barium ferrite films with various crystal orientations were deposited by sputtering, and their magnetic properties were investigated. The film composition was changed with the position of the substrate. This composition change was partly caused by the changes in composition of the sputtered particles with changing emission angle during sputtering. Compared with particulate media with barium ferrite particles, which have a positive peak in the ¿M curve, the ¿M curve of these films has a negative peak, suggesting that a magnetostatic magnetic interaction is the main interaction between particles in the film. Film with random orientation had a larger negative peak than did film with a c-axis orientation. View full abstract»

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  • MR Properties and Thermal Stabilities of Cu/Co/Cu/NiFe Multilayers

    Page(s): 32 - 37
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    Cu/Co/Cu/NiFe multilayer films prepared by evaporation in an ultrahigh vacuum showed induced ferrimagnetism and giant MR properties. The slope of the linear part of the MR curve near zero field is sensitive to the coercive force and squareness ratio of magnetization of the NiFe layers. The maximum slope was 0.41 %/Oe for Cr(50Å)[Cu (50Å)/Co(10Å)/Cu(50Å)/NiFe(15Å)]×10. The annealing temperature dependence of the slope was due to the interdiffusion of NiFe and Cu layers. Improved thermal stability was obtained by the use of thicker NiFe layers. View full abstract»

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  • Dependence of Magnetoresistance on Preparation Conditions and Annealing in Co/Cu Multilayers

    Page(s): 38 - 43
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    The structure of sputter-deposited Co/Cu multilayer film depends strongly on such preparation conditions as the Ar gas pressure (PAr) and the substrate bias voltage (VB). For films deposited at VB=0 V, the interfaces were flat and the (111) plane orientation was good at low PAr. The (111) orientation was better for ¿30 V films than for 0 V films. The interface was flat at high PAr, in contrast with 0 V films. The giant magnetoresistance (GMR) depended heavily on the layer flatness, the film density, and the existence of crystal grains with an fcc (200) orientation. The effect of annealing on the film structure and GMR was also investigated. Annealing for 10 min. at 200°C in vacuum did not change the film structure very much, but the first GMR peak height of 0 V films decreased significantly, in contrast to the stable second GMR peak. View full abstract»

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  • Magnetoresistance in Ni-Fe/Cu Multilayers

    Page(s): 44 - 48
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    Ni80Fe20/Cu multilayer films were prepared on glass substrate by magnetron sputtering. The dependence of the magnetoresistance on the thickness of the Cu layer, the thickness of the Ni-Fe layer, the thickness of the buffer layers for Fe, Ni80Fe20 and Cu, and the number of bilayers, was investigated. The MR ratio peaked at dCu= 10Å, where the MR ratio was about 20% at room temperature. When the thickness of the Ni80Fe20 layer was varied, the MR ratio had a broad peak from dNi-Fe=15 to 30Å. The interlayer exchange interaction was evaluated as 3×10¿2 erg/cm2, irrespective of the thickness of the buffer layer. The MR ratio increased with the number of bilayers N, and reached saturation when the total film thickness was about 800 to 1000Å. View full abstract»

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  • Magnetooptical Spectra in Pt-Ni Alloys and Multilayers

    Page(s): 49 - 53
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    Pt-Fe, Pt-Co and Pt-NiCo alloys and multilayer films were prepared on a SiO2 substrate by the dc magnetron sputtering technique. The reflectivity spectra and magnetooptical Kerr spectra of these specimens were measured, and the diagonal and off-diagonal elements of the conductivity tensor were deduced. The results of this work are as follows: (1) The peak energy position of the magnetooptical Kerr rotation spectra showed a systematic shift to lower energies as the transition metal was changed from Fe to Ni, both in multilayer and alloy samples. (2) Simulation using the above-determined conductivity tensor for alloys revealed that alloy layers exist at the interfaces between Pt and the transition metal in all the Pt-based multilayer films investigated. (3) Obvious effects of plasma enhancement were confirmed in the short-wavelength magnetooptical Kerr spectra of the Pt-based alloys. View full abstract»

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  • Nonequilibrium Dynamics and Chaos of Domain-Wall Motion

    Page(s): 54 - 58
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    The study of magnetic domain wall motion is important in both the field of power-magnetic microcores and in magnetic recording applications. The nonlinear differential equation for Bloch wall motion is obtained by modification of the Landau-Lifshitz-Gilbert equation. The terms of the nonlinear force of restitution and eddy current damping are added, and the equation is solved by using fourth order Runge-Kutta method. The tendency for the amplitude of magnetic domain wall motion to decrease with increasing layering frequency of the CoZrMo/SiO2 multilayered core is well reproduced by computer simulation. The irregular oscillation of the domain wall is found to be chaotic because a fractal structure is observed in the Poincare map. This result leads to a method for investigating energy loss and irregular phenomena (error or noise in magnetic recording systems) arising from magnetic domain wall oscillations. View full abstract»

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  • Domain Structures and High-Frequency Response of Magnetization for CoNbZr Stripe Films

    Page(s): 59 - 66
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    The domain structures and high-frequency response of the magnetization of amorphous soft magnetic CoNbZr films were studied, using the Bitter method and scanning Kerr-effect microscopy. A Lifshitz-type domain structure, characterized by wedge-shaped domains, was observed in the films (stripe-shaped, over 100 ¿m wide and 1 ¿m thick). The change in magnetization associated with 180° domain wall movement increased with increasing frequency, reaching a maximum near 5 to 10 MHz, whereas the change in magnetization at the walls of the wedge-shaped domains or at 90° domain walls was highest near 30 MHz. The loss factors due to these magnetization changes were three to six times that due to magnetization rotation at frequencies between 20 MHz and 40 MHz. These results imply that the changes in magnetization due to the wedge-shaped domain walls and 90° domain walls exert some influence on the Q factor of thin-film inductors at high frequencies above 10 MHz. View full abstract»

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  • (110) [001] Grain Growth in Silicon Steel Sheets of 30 μm Thickness

    Page(s): 67 - 72
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    Thin grain-oriented silicon steel sheets have the lowest iron loss at a thickness of 30 μm. We observed the recrystallization behavior and magnetic properties of 30 μm thick silicon steel sheets, and compared the results with those of 60 μm thick silicon steel sheets. The recrystallization processes in the two types of sheet were found to be different. The primary recrystallized 30 μm thick silicon steel sheets did not have a strong (110) [001] texture or other orientation; consequently secondary recrystallization did not occur. However, at annealing temperatures above 1050°C, (110) [001] grains grew selectively. Thus we were able to obtain very thin grain-oriented silicon steel sheets with a thickness of 30 μm. View full abstract»

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  • New Servo System for Large Capacity Floppy Disk

    Page(s): 73 - 79
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    A low-cost, simplified continuous servo system employing a single servo signal detector is proposed. The servo record on the media consists of two frequency components, and the higher frequency component has a different phase on alternate tracks. The tracking error is detected from the phase difference of the two frequency components extracted from the single servo detector. The system was inspected using a test system with a 6 ¿m servo track pitch. The magnetic recording performance for floppy disks was evaluated using 7 ¿m and 9 ¿m track widths. Based on the results, a 3.5" floppy disk system with a 100 to 200 MB capacity could be developed for practical use. View full abstract»

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  • Magnetic Properties and Film Structure of Multiple-Structure Multilayered Co/Pd Films

    Page(s): 80 - 86
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    Co/Pd, Co/Pt and Co/Au multilayer films exhibit large perpendicular magnetic anisotropy. We studied multiple-structure, multilayer Co/Pd films, composed of a number of thin multilayer Co/Pd films with unity squareness ratio, stacked in a periodic structure, separated by thin nonmagnetic metallic Pd film layers. The magnetization curves of multiple-structure, multilayer films have multistage shapes, caused by differences in coercive force of each of the Co/Pd film layers. X-ray diffraction was used to study the structure of multiple-structure multilayer films. Theoretical calculations of X-ray diffraction patterns agree with the experimental results. View full abstract»

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  • High-Speed Track Access Technique Based on Model Following Control for Disk Drives

    Page(s): 87 - 94
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    This article discribes a model following control system enabling disk drives to achieve high-speed track access. In this kind of control system, a prediction from a model plays an important role in reducing access time. We propose a new reference model based on a numerical model of the VCM (voice coil motor) used as the disk drive actuator. Taking the VCM actuator dynamics into account, the reference model generates a reference trajectory to achieve high-speed head positioning. Simulation and experimental results for a typical hard disk drive indicate the validity of the proposed method. View full abstract»

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  • Head Pad Positioning Control System for Hard Disk Drives

    Page(s): 95 - 102
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    High track densities and short access times have been achieved using an H¿ controller with a sector servo system. The authors studied the difference in control performance for a system designed using the weighted mixed-sensitivity problem and one designed using the four block problem. By designing a two-degrees-of-freedom controller using H2 optimal theory, fast seeking was realized. On applying these servo systems to a hard disk drive, ±0.2¿m head positioning accuracy and a 2.5 ms one-track seek time were achieved. View full abstract»

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  • Giant Magnetoresistance in NiFeCo/Cu Multilayers

    Page(s): 103 - 109
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    NiFeCo/Cu multilayer films with NiFeCo buffer layers, prepared by rf magnetron sputtering, show a giant magnetoresistance (MR) effect which oscillates as a function of the Cu thickness. At the second peak of this oscillation, multilayer films have an MR ratio of 12% in fields as low as 50 Oe. The film structure and MR properties are stable with respect to annealing at temperatures up to about 300°C. A field sensitivity of about 0.4%/Oe was obtained over the minor loop of the MR curve, measured using a field in the hard-axis direction. The field sensitivity was almost constant up to a frequency of 1 MHz. View full abstract»

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  • Optimum Design of an Orthogonal Core Based on a Magnetic Circuit

    Page(s): 110 - 115
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    The operating characteristics of parametric transformers and dc-ac converters with an orthogonal core depend heavily on the core shape. Accordingly, to obtain the optimal design for such devices, the quantitative relationship between the orthogonal core shape and the operating characteristics of the application device are determined. In this paper, the application characteristics are discussed analytically in terms of the orthogonal core shape, with reference to a magnetic circuit model of the core. View full abstract»

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  • Soft Magnetic Properties and Corrosion Resistance of Nanocrystalline Fe-Al-Ta-C Films

    Page(s): 116 - 123
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    The effect of addition of Al to sputtered nanocrystalline Fe-Ta-C films on the film structure, soft magnetic properties and corrosion resistance were investigated. Films were crystallized from an amorphous state to a nanocrystalline state in which ultra-fine TaC particles were dispersed. Most of the Al in the films was dissolved in ¿-Fe after crystallization. When the Al concentration was increased, the high-frequency permeability improved owing to the increase in electrical resistivity. The thermal stability of the soft magnetic properties was also improved over that of Fe-Ta-C films, and the film corrosion resistance improved sufficiently, probably because of the Al dissolved in ¿-Fe. An Fe66.6Al10.6Ta10.5C12.3 nanocrystalline film after annealing at 823K exhibited a high saturation point of 1.25 T, a high permeability of 3200 at 1 MHz, a high electrical resistivity of 1.32 ¿¿-m, and excellent corrosion resistance and noble pitting potential. View full abstract»

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  • Tb-Fe Sputtered Films with Large Magnetostriction for Use in Magnetomechanical Thin-Film Devices

    Page(s): 124 - 128
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    We examined the magnetostriction and coercive force of amorphous Tb-Fe films sputter-deposited under different conditions (rf input power, Ar gas pressure, Tb content, etc.). Here we discuss the possibility of obtaining both soft magnetic properties and a large magnetostriction in this system. Soft magnetic properties and large magnetostriction were obtained simultaneously in sputtered Tb-Fe thin films prepared with a Tb content of 45 to 50 at%, under an Ar gas pressure of 4 mTorr and with an rf input power of 200 W. This material has strong potential for use in magnetomechanical thin-film devices. View full abstract»

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  • Magnetostriction of Sm-Fe Thin Films Fabricated by a Sputtering Method

    Page(s): 129 - 133
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    The magnetostriction and magnetic properties of sputtered SmxFe100-x (3¿x¿54) thin films at room temperature were investigated. Films had an amorphous structure for x¿12. The magnetostriction ¿ of the films increased rapidly under weak fields (≪1 kOe) and reached maximum values in the range 130 to 160×10¿6 at 16 kOe for x=30 to 40, suggesting that Sm-Fe films can be used in microactuators and sensors. The magnetic properties did not show a clear dependence on the sputtering conditions, such as the input power, Ar gas pressure, or substrate temperature (¿250°C). View full abstract»

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Aims & Scope

IEEE Translation Journal on Magnetics in Japan is a publication of the IEEE Magnetics Society published between 1985 and 1994.

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Meet Our Editors

Editor-in-Chief
James E. Opfer
Hewlett-Packard