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  • American Institute of Physics (AIP)  (50)
  • BioMed Central  (38)
  • 2015-2019  (52)
  • 1990-1994  (36)
  • 1
    Electronic Resource
    Electronic Resource
    On the switching characteristics of Co and CoPtCr thin films (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7731-7734 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the influence of intergranular magnetic coupling on switching characteristics in Co and CoPtCr thin films. The strength of the intergranular interactions was varied by changing the sputtering pressure and film or underlayer thickness. For each sample we have measured the deviation δM from the behavior expected for noninteracting single-domain particles and correlated the results to the magnetic layer and under layer thickness and to the microstructure of the recording film. We show a correlation between δM and the strength of magnetic coupling. Where similar magnetic parameters allow a comparison, we find a correlation between media noise and the trend in δM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347549
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of Er3+-doped glasses by fluorescence line narrowing (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 6799-6811 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Stark levels of the 4I15/2 ground state manifold have been determined for Er3+-doped fluorozirconate, fluorophosphate, phosphate, and silicate bulk glasses from fluorescence-line-narrowing (FLN) measurements at 4.2 K. Splittings between adjacent Stark levels were observed to be 10–140 cm−1 and the total energy spread of the manifold was found to range from 335 to 400 cm−1. The position of a given Stark level varies up to 60 cm−1 depending on the particular Er3+ sites excited. Using the 4.2-K results, homogeneous broadening is found to be a reasonable approximation for the 300-K luminescence band of the glasses examined. Results are also presented for silica preforms as well as for a barium-zinc-lutetium-thorium fluoride composition. The FLN studies together with a Judd–Ofelt [Phys. Rev. 127, 750 (1962); J. Chem. Phys. 37, 511 (1962)] analysis of the absorption data suggest similarities in the local environment between the fluorozirconates and the high-fluorine fluorophosphates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347669
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  • 3
    Electronic Resource
    Electronic Resource
    2.5 μm GaInAsSb lattice-matched to GaSb by liquid phase epitaxy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 5936-5938 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaSb lattice-matched Ga1−xInxAsySb1−y has been grown by liquid phase epitaxy on (100) and (111)B oriented substrates using initial melt supersaturation ΔT varying from 10 to 30 °C, at growth temperatures 〉600 °C. It is shown that the band-gap cutoff wavelength, measured at room temperature by the electroreflectance method, is ∼2.38 μm for (100) layers whatever ΔT, and increases from 2.38 μm up to 2.51 μm for (111)B oriented layers when ΔT is increased from 15 to 25 °C. Photoluminescence experiments at 2 K confirm the band-gap reduction occurring at high ΔT with the (111)B orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346925
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence spectra in an applied magnetic field for excitons bound to ionized donors in high-purity, epitaxial GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 4909-4918 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic-field dependence (0–6.4 T) of the photoluminescence spectra of ionized donor-bound excitons [(D+, X)] has been studied for high-purity GaAs grown by organometallic vapor phase epitaxy. Detailed data were taken on circularly polarized emission, leading to an electron-hole-coupling model which yields total angular momentum values of J=1,2. The effective magnetic-moment g values describing the substate splittings between MJ = +1 and −1 are found to be 0.86 and ≈0.5 for the J=1 and 2 states, respectively. The studies were performed on material with background, donor impurities identified as Si and Ge, yielding a chemical shift between (D+Si, X) and (D+Ge, X) of 0.15 meV at 6.4 T. Well-resolved (D+, X) features were only observed in the highest-purity material (impurity concentrations ≈ low 1014 cm−3). Some results are also reported for a layer grown by molecular-beam epitaxy whose lack of neutral-donor-related features permits the high-energy (D+, X) components to be observed at high fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349036
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  • 5
    Electronic Resource
    Electronic Resource
    Role of atomic mass of underlayer material in the transition noise of longitudinal media (abstract) : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4749-4749 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and recording properties of CoPtCr on Mo and W underlayers were investigated and compared to Cr underlayers over the sputtering pressure range of 3–24 mTorr. Normalized media transition noise decreases with increasing pressure in all cases, and the reduction can be attributed to a reduced intergrain exchange coupling due to isolation of the magnetic grains. In the low-pressure regime, the transition noise increases with increasing atomic mass of the underlayer, Cr〈Mo〈W. This trend can be attributed to the growth features of the underlayers which change from a partially coupled structure for Cr to closely coupled grains for W. We attribute this behavior in the low-pressure regime to increasing mobility with increasing atomic mass since the energy flux of the sputtered atoms and the back-reflected argon atoms increases with the atomic mass of the target. In the high-pressure regime, all underlayers produce an isolated grain morphology in the magnetic layer, which indicates sufficient thermalization of the atoms during the transport resulting in similarly low values of transition noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348269
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  • 6
    Electronic Resource
    Electronic Resource
    Correlation between the photoreflectance response at E1 and carrier concentration in n- and p-GaAs (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2525-2531 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the photoreflectance (PR) response of metalorganic chemical vapor deposition-grown n- and p-type GaAs at the higher-energy transition E1(≈2.9 eV). The doping level range of interest was 2×1016–4×1018 cm−3 for Si:GaAs and 6×1016– 1×1019 cm−3 for Zn:GaAs. Both the position and the broadening parameter, Γ1, of the E1 transition within the doping concentration range were investigated. The evaluation of Γ1's, based on the curve fitting of the PR response and the Kramers–Kronig analyzed data reveal a nearly linear relation between Γ1 and the logarithm of the carrier concentration. This observation has the potential application for contactless determination of carrier concentration in moderate and heavily doped nanoscale films. Secondary-ion mass spectroscopy measurements show that there is relatively large compensation in Si:GaAs samples, but it does not correlate with the broadening of the E1 structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348691
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  • 7
    Electronic Resource
    Electronic Resource
    Media noise in periodic multilayered magnetic films with perpendicular anisotropy (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1791-1795 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Periodic, finely multilayered thin-film magnetic structures (≤200 A(ring)) with high in-plane coercivity suitable for longitudinal recording investigations have been fabricated. CoPt20/Pd and CoPt12Cr17/Pd periodic multilayers can exhibit a perpendicular orientation, originating from surface anisotropy effects, with a magnitude depending on the thickness of the component layers. The perpendicular orientation influences the transition noise, but for the particular systems studied, the results suggest that for a given value of coercivity squareness, (approximately-less-than)0.8, the greatest improvements in media noise performance can be achieved through reduced exchange in films with a well-defined, in-plane orientation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346611
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  • 8
    Electronic Resource
    Electronic Resource
    Role of atomic mass of underlayer material in the transition noise of longitudinal media (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1837-1840 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and recording properties of CoPtCr on Mo and W underlayers were investigated and compared to Cr underlayers over the sputtering pressure range of 3–24 mTorr. Normalized media transition noise decreases with increasing pressure in all cases, and the reduction can be attributed to a reduced intergrain exchange coupling due to isolation of the magnetic grains. In the low-pressure regime, the transition noise increases with increasing atomic mass of the underlayer, Cr〈Mo〈W. This trend can be attributed to the growth features of the underlayers which change from a partially coupled structure for Cr to closely coupled grains for W. We attribute this behavior in the low-pressure regime to increasing mobility with increasing atomic mass since the energy flux of the sputtered atoms and the backreflected argon atoms increases with the atomic mass of the target. In the high-pressure regime, all underlayers produce an isolated grain morphology in the magnetic layer, which indicates sufficient thermalization of the atoms during the transport, resulting in similarly low values of transition noise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349500
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  • 9
    Electronic Resource
    Electronic Resource
    Beyond discrete tracks: Other aspects of patterned media : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4724-4726 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface of a thin-film disk can be patterned using standard lithographic techniques to form discrete tracks as narrow as 0.5 μm. These studies have been extended to patterns formed when an etched track is broken into discrete segments by etching away some portions of a discrete track. Abrupt changes in the magnetization can be obtained by dc erasing the medium, giving readback signals with ∼50% of the amplitude of conventional transitions when the gap of the readback head is aligned with the edge of the media pattern. The implications of these results for servo and read-only applications are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348260
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  • 10
    Electronic Resource
    Electronic Resource
    Magnetic force microscopy: General principles and application to longitudinal recording media (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 1169-1183 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper discusses the principles of magnetic force microscopy (MFM) and its application to magnetic recording studies. We use the ac detection method which senses the force gradient acting on a small magnetic tip due to fields emanating from the domain structure in the sample. Tip fabrication procedures are described for two types of magnetic tips: etched tungsten wires with a sputter-deposited magnetic coating and etched nickel wires. The etched nickel wires are shown to have an apex radius on the order of 30 nm and a taper half-angle of approximately 3°. Lorentz-mode transmission electron microscopy of the nickel tips reveals that the final 20 μm is essentially single domain with magnetization approximately parallel with the tip axis. Images of written bit transitions are presented for several types of magnetic media, including CoPtCr, CoSm, and CoCr thin films, as well as γ-Fe2O3 particulate media. In general, the written magnetization patterns are seen with high contrast and with resolution better than 100 nm. A number of magnetic recording applications are discussed, including the investigation of overwrite behavior and the writing characteristics in CoSm media at high data density. Computer calculations were performed to simulate the MFM response to written magnetic transitions. By including the extended geometry of the tip, the nonparallel orientation of the cantilever, and the finite width of the magnetic transitions, good agreement with experiment was obtained. The model calculations correctly predict the experimentally observed change in image contrast that occurs as a function of tip orientation. Computer calculations showing the dependence of resolution on tip geometry are also presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346713
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