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  • 1
    Electronic Resource
    Electronic Resource
    Study of Co-Cr films for perpendicular magnetic recording using nuclear magnetic resonance (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 705-712 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A 59Co nuclear magnetic resonance measurement and a transmission electron microscope observation are utilized to investigate the compositional distribution of Co-Cr films with and without heat treatment. The spin-echo spectra of evaporated films are found to be entirely different from those of Co-Cr alloy powders. The spectra of films comprise a very complicated hyperfine field distribution and the resonant frequencies are much higher than those of powder samples, implying the existence of various kinds of segregation regions typical of a film. Chrysanthemumlike patterns, which disappear with heat treatment, are also observed for chemically etched films. This disappearance is accompanied by the disappearance of the highest-frequency resonant line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346802
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  • 2
    Electronic Resource
    Electronic Resource
    S/N ratio of thin-film media estimated by computer simulation (abstract) : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5578-5578 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper derives a formula that shows a direct relationship between the noise spectrum and the magnetization configuration of a thin-film medium. This formula was obtained by Fourier transforming the down-track autocorrelation function of jMx-Mz, where Mx and Mz are the longitudinal and vertical components of magnetization. The formula takes into account not only the variance of the magnetization deviation, which is generally used to estimate media noise, but also the correlation between deviations in magnetization. This lets us calculate the noise power spectrum as well as the signal power, once the magnetization configuration in a medium is obtained, which means that the magnetic microstructures such as vortex, zig-zag domain, etc., are automatically included in noise calculation. To investigate the relationships between the noise properties and the magnetic properties of media with various anisotropy fields (Hk), axis orientation of easy magnetization, and stiffness constants (A), recorded magnetization configurations were simulated using the Landau–Lifshitz–Gilbert equation.1,2 The easy axis was oriented from uniaxial direction to random direction in plane. The simulated noise power spectra were maximized at a relatively long wavelength, which was varied by changing Hk, or the easy axis orientation. The noise power was strongly influenced by Hk and the axis orientation of magnetization. This confirms that preferential orientation along the longitudinal direction and a large Hk are effective for improving the S/N ratio. On the other hand, the stiffness constant less improved media noise than Hk and axis orientation, suggesting that the preferential orientation of the easy axis is more effective to reduce media noise than isolating magnetic grains.1
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353656
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  • 3
    Electronic Resource
    Electronic Resource
    A method of measuring anisotropy field of polycrystalline thin-film media (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4720-4722 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferromagnetic resonance (FMR) is used to measure the magnetic anisotropy field Hk and its dispersion of poly-crystalline recording media. This method does not use any single crystal substrate. A high-intensity field is applied vertically to a sample surface to completely saturate the magnetization and a high-frequency (over 50 GHz) magnetic field is applied in the surface. An FMR simulator based on the Landau–Lifshitz–Gilbert equation confirms that the magnetic (exchange and/or magnetostatic) interactions have very little effect on the resonant frequency in the configuration used. The linewidth of the FMR spectrum is affected by the Hk dispersion and damping constant. Methods using a torque or magnetization curve include magnetic interactions, resulting in a systematic error to the value of Hk. This FMR method is applied to CoCrPt-alloy thin-film media with a Cr-alloy underlayer grown on a glass substrate. A conventional torque method is also used for comparison. The axis of hexagonal-close-packed Co magnetic grain is distributed at random in the surface. In an FMR measurement, external magnetic field is applied vertically to the surface up to 55 kOe for two frequencies (71 and 117 GHz). The obtained Hk is 7.0±0.2 kOe, which is a little higher than the Hk of 6.4 kOe estimated with the torque loss method. Important physical parameters that affect the recording performance are also estimated using the linewidth of FMR spectra for different frequencies with a micromagnetic simulation: Hk dispersion=1.2±0.5kOe, Gilbert's damping constant α=0.03±0.01, and a g value=2.19±0.02. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370459
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  • 4
    Electronic Resource
    Electronic Resource
    Method of measuring anisotropy field of a recording medium investigated by computer simulation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5303-5308 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Three methods of measuring anisotropy field of a recording medium with the easy directions in the film plane were examined by computer simulation: (1) applying magnetic fields in a direction slightly tilted from the hard direction of the medium, (2) using rotational hysteresis loss, (3) applying perpendicular field to the film plane. The anisotropy fields obtained with these methods were smaller than the intrinsic anisotropy fields of grains (or particles). A method is proposed for obtaining the intrinsic anisotropy field of grains. In this method, magnetic torques are measured out-of-plane of a film. A method, which is an extension of the above method (1), for measuring the distribution of easy direction, is also examined and a revised method is proposed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359285
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  • 5
    Electronic Resource
    Electronic Resource
    Computer simulation of thin-film media noise using an autocorrelation function along the track direction (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1190-1200 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The causes of thin-film media noise are discussed by deriving a formula which shows a direct relationship between the noise spectrum and the magnetization configuration of a thin-film medium. This formula is derived by Fourier-transforming the autocorrelation function of jMx-Mz along the track direction, where Mx and Mz are the longitudinal and vertical components of magnetization, respectively. Noise and signal spectra are computed by means of this formula. The computed noise spectra are the maximum for a relatively long wavelength. Their form and intensity are shown to be strongly affected by the anisotropy constant and the axis orientation of easy magnetization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356475
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of longitudinal bias field on magnetization distribution in magnetoresistive head with shield films (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 1036-1040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization distribution in the magnetoresistive (MR) film has been calculated by self-consistently solving the three-dimensional field of the MR head. The magnetization distribution was calculated based on the Landau–Lifshitz–Gilbert equation and the head field was obtained by the Maxwell equation. The longitudinal bias field for the domain control was generated by exchange-coupled antiferromagnetic or permanent magnetic films which were formed outside the sensing region of the MR film. The resistance change of the MR film was calculated from the magnetization distribution with shield films and without shield films. It was found that the resistance change with the antiferromagnetic film without the shields was about two times larger than that with the permanent magnetic film with the remanence Br of 0.7 T. The difference between them was reduced when the shields were formed because the stray field from the permanent magnetic film which is applied to the MR film was decreased by the shields. Further, the effect of the longitudinal bias field on the magnetization distribution was analyzed for the MR film without the shields. The influence of the antiferromagnetic film reached the region of 2–3 μm from the end of the film, while that of the permanent magnetic film reached more than 10 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356484
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  • 7
    Electronic Resource
    Electronic Resource
    Dependence of switching coefficient on damping constant of thin-film magnetic recording media (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5672-5674 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated the relationship between the switching time of thin film media and the Gilbert damping constant α through numerical calculations. The switching coefficient, Sw (the required energy for switching) of thin-film media was estimated from the time integration of the external field over switching field, Hcro(∫[H(t)−Hcro]dt). With decreasing α, Sw of a two-dimensional random thin-film medium with an uniaxial anisotropy field Hk of 6.5 kOe, reached a minimum (fastest) value of 50 ns Oe at α of about 0.1 and then increases slightly to 88 ns Oe at α=0.03. This value was nearly equal to the Sw value of 101 ns Oe at α=1.0. The value of α (about 0.1) that gave a minimum Sw did not change significantly with Hk or saturation flux density Bs. We showed analytically that the value of α for the fastest switching was less than 1.0, when an effective field was applied in a direction different from the easy axis of a magnetic grain. The switching time was in proportion to the rate of Sw/Hk of a thin-film media. These results show that high-speed recording at frequencies of up to 1 GHz can be achieved at α=0.03 in terms of the switching time of longitudinal thin-film media. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372485
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  • 8
    Electronic Resource
    Electronic Resource
    Magnetic properties and media noise of Co-Ni-P plated disks (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 270-275 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic properties and read-write characteristics of Co-Ni-P plated disks are examined. In-plane coercive force and squareness increase with increasing the thickness of an Ni-P layer which is formed between the substrate layer (Cu-Sn) and Co-Ni-P film. However, media noise increases with thickening of the Ni-P layer. The relationships between magnetic properties and media noise are investigated by measuring rotational hysteresis (Wr) and its integral (RH). As a result, it is found that media noise closely correlates RH values: smaller RH values cause less media noise. This result shows that media noise is dominated by the magnetization process, and magnetic thin film in which the magnetization process occurs through coherent rotation is desirable for magnetic recording media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341421
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  • 9
    Electronic Resource
    Electronic Resource
    Sensitivity-enhanced electron holography and its application to magnetic recording investigations (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 2000-2004 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The sensitivity for electron-phase measurement in electron holography has been improved to better than 2π/100 by the application of digital interferometry at the optical reconstruction stage. This enables quantitative measurement of magnetic flux as small as (1/100)(h/e)(=4.1×10−17 Wb), hitherto undetectable, with high spatial resolution. With this technique, we have observed the distribution of leakage magnetic field from a thin cross section of a perpendicularly magnetized recording film (cobalt-chromium) with a recording density as high as 300 kFCI (85 nm bit length), the highest density ever directly observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342891
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  • 10
    Electronic Resource
    Electronic Resource
    New oxide catalysts with perovskite-related structure for reduction of nitric oxide with ammonia (1978)
    s.l. : American Chemical Society
    Environmental science & technology 12 (1978), S. 185-189 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es60138a009
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