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  • 1
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Many recent studies of recording and playback in magnetic recording systems have been based on the computer simulation of micromagnetic models of magnetic recording media. Medium models are capable of representing a large class of recording media by selection of appropriate values of model parameters representing the intrinisic properties of the recording medium material. Such parameters include grain size, anisotropy energy density, and exchange energy constant. Largely missing in these studies, however, has been a discussion of how to identify a set of parameter values to represent a particular medium of interest. In this presentation, we describe an identification procedure for selecting the values of the five intrinsic parameters of a micromagnetic medium model to represent a recording medium for which the following hysteresis properties are known: remanent magnetization, coercivity, remanence squareness, and coercivity squareness. Calculation of hysteresis loops verifies that the particular instance of the medium model identified by this procedure reproduces the hysteresis behavior of the medium of interest. Comparison of computer simulations of recording operations to measured recording performance of a medium on a laboratory tester may then be meaningfully made.© 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 2343-2345 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Semiconductor alloys like Hg1−xCdxTe and Al1−xGaxAs, where there is a close lattice constant match between the constituents, are nearly random. Consider mesoscopic size scales of radius r that are large compared with a lattice constant (∼25 A〈r〈∼250 A), but small compared with typical device dimensions. In such regions the number of substitutional sites is small enough so the root-mean-square concentration fluctuation 〈(Δx)2〉1/2 is sufficiently large to produce random arrays of mesoscopic "quantum dots" that adversely affect many device properties. The influence of the adverse effects differ among various properties—for example, electron and hole mobilities, lifetimes, and so on—but, in general, are worse the smaller the fundamental gap becomes. These kinds of fluctuations are suppressed in lattice-mismatched alloys like Hg1−xZnxTe and Ga1−xInxAs because there is a long-range strain energy penalty associated with them. Thus, lattice-mismatched alloys are more spatially uniform than lattice-matched alloys. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of such medium properties as magnetic unit size, film thickness, and strength of anisotropy, dipolar, and exchange interactions on the storage capacity limit of a thin-film recording medium is investigated. Relationships are derived for media with different properties that have equivalent capacity. The physically realizable range of material properties and their effect on the capacity bound are explored. Results on edge effects for capacity bound computations are presented. The results indicate that media for which anisotropy is the dominant source of magnetic energy have the greatest potential for information storage.
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A randomized microstructure based on the Voronoi diagram is proposed for micromagnetic models. Simulations illustrate variability of extrinsic magnetic properties with microstructure, medium noise dependence on medium properties, and jitter dependence on trackwidth. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A simple model that represents the microstructure of magnetic medium as a rectangular tesselation predicts that the mean-square jitter is inversely proportional to the track width. We test this prediction using different width heads as well as creating different track widths by partially erasing the original track. We also simulate these experiments using a micromagnetic model. Our experimental and simulation results are found to be in agreement with the prediction. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2027-2028 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe an in situ nondestructive method to measure the intergranular coupling in magnetic thin film recording media based on Stoner–Wohlfarth switching theory [Philos. Trans. Roy. Soc. London A 240, 599 (1948)]. The method uses recording write and read heads and a disk test stand to measure a medium's remanence curves from saturation and demagnetization. Using this technique, we have measured Henkel plots [Phys. Status. Solidi 7, 919 (1964)] for single layer and multiple layer longitudinal media, as well as a Henkel plot for a perpendicular thin film with a highly permeable underlayer, which cannot be obtained by the conventional vibrating sample magnetometer method.
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  • 7
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed an experimental method for investigating the interaction between two dc track edges by studying the track edge noise. We conclude that two edges do not interact when they are several micrometers apart, but the noise reduces nearly to zero when their separation is less than about half a micrometer. There is a transition region that exists between these two limits. The net track edge noise power from two dc edges is quantized, implying that in our experiment track edges interact around the complete revolution of the disk or not at all.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 50 (1963), S. 325-326 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4683-4685 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Track edge fluctuations on recording media affect signal-to-noise ratio and servo control, and can provide clues to the medium's magnetic microstructure. We write track edges on longitudinal thin-film magnetic recording media by dc erasing the medium and writing a saturated dc track of opposite magnetization direction on the erased band. We then "read'' the position fluctuations of the x-component reversal of one edge of the written track by centering a head on that edge, and by stepping the head across the edge. Since a straight track edge would not produce any flux change in the read head coil, the voltage output of the head arises from flux changes due to track edge fluctuations. The spectrum of the fluctuations can be deduced by decorrelating the read head sensitivity function from the voltage spectrum. We have used this procedure with several low- and high-noise thin-film media and we find in each case a k−b spectrum (k=wave number) with b near 1. We propose a model which interprets the fluctuations as a superposition of uncorrelated protuberances from a nominal straight edge, and we deduce the size distribution of the protuberances which will generate the observed fluctuation spectrum. Simulated reconstruction of the track edge resulting from a weighted superposition of the protuberances permits semiquantitative inferences to be drawn from the model about the medium microstructure.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4994-4996 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin-stand experiments were performed to study the effect of temperature and demagnetizing fields on the stability of magnetic recordings. Tracks of varying linear bit densities were written on a low Mrδ medium that was heated in situ to different temperatures. The readback amplitude, which reflects the changes in the magnetization of the recordings, was observed from 32 ms to 12 h after the tracks were written. The readback amplitude was found to decay with time. The rate of decay increased at higher densities due to higher demagnetizing fields. A further increase in the decay rate was observed at higher temperatures. This increase in decay rate exceeded that predicted by proportional temperature scaling. © 1999 American Institute of Physics.
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