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  • 1
    Electronic Resource
    Electronic Resource
    Crystallographic orientation of textured CoCrTa/Cr sputtered thin film media for longitudinal recording (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5117-5124 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the influence of deposition conditions on the structure and properties of Co84Cr14Ta2 alloy magnetic thin films and Cr underlayers sputtered onto circumferentially textured and smooth polished NiP/Al substrates. Suitable processing conditions provide in-plane magnetic anisotropy in the textured media, with enhanced coercivity (Hc) and coercivity squareness (S*) in the circumferential direction and reduced Hc and S* in the radial direction. The crystallography in these films was studied by transmission electron microscopy (TEM) to address the origin of the observed magnetic anisotropy. The CoCrTa alloy grains are found to grow semicoherently on the chromium underlayer, resulting in vertical 〈200(approximately-greater-than) Cr and 〈112¯0(approximately-greater-than) CoCrTa axes. This requires an in-plane orientation of the CoCrTa c axis, which is observed to be nearly random by high-resolution TEM. Microdiffraction shows apparent preferred c-axis alignment locally at texture lines, but this observation is primarily attributable to asymmetric tilting of the vertical growth direction caused by the substrate topography. The 〈112¯0(approximately-greater-than) growth axis appears to be perpendicular to the local grooved surface, not the bulk surface, requiring a local c-axis out-of-plane tilt near the grooves. The anisotropic surface topography induces a corresponding anisotropy in the out-of-plane component of the magnetically easy c axis in the CoCrTa alloy, which we suggest has implications on the bulk magnetic anisotropy in such films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353785
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic, recording, and crystalline properties of multilayered longitudinal thin-film media : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4727-4729 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Multilayered longitudinal CoCrTa and CoCrPt media were evaluated for magnetic and recording properties. Depending on the alloy, multilayering produced 150–500 Oe increases in coercivity over equivalent single-layer media. These coercivity increases were also found to depend on the chromium underlayer and spacer layer thickness. The coercive squareness of the CoCrPt media was found to decrease upon multilayering, while S* of the CoCrTa double layer showed a slight increase with thicker Cr spacer layers. Double layering of the CoCrPt alloy produced up to a 4-dB increase in signal-to-noise ratio, while double-layer CoCrTa media demonstrated a 2.7-dB increase. Differences between the magnetic and recording properties of CoCrPt multilayers deposited on Cr underlayers of varying thicknesses are analyzed in terms of changes in crystalline anisotropy introduced by the multilayering process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348261
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  • 3
    Electronic Resource
    Electronic Resource
    Laser texturing for low-flying-height media : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5745-5747 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel selective-area texturing process using a pulsed laser to produce a new form of texture in only the landing zone is discussed. By rotating the media under the focused pulsed-laser beam, a row of crater shaped dimples are created in the landing zone only. The rest of the disk remains smooth and untextured. Contact start-stop (CSS) test results from a lubricated C/CoCrTa/Cr media on the laser-textured substrate exhibited a constant static friction coefficient of 0.17 even after 12-K CSS cycles, with no apparent friction buildup. This unique behavior is attributed to the rounded and smooth surface topography of the laser-textured media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347908
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of angular coercivity in various magnetic media (abstract) (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4713-4713 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Angular coercivity provides a method for studying magnetization-reversal mechanisms and has stimulated theoretical interests particularly for recording materials.1 This paper reports our experimental results on the angular variation of coercivity in different magnetic media prepared by various means, and compares these data. These include CoNiCr/Cr-type longitudinal media and Ba-ferrite–type particulate longitudinal media for hard-disk applications, and CoNi-type oblique evaporated longitudinal media for video recording. Results from sputtered CoNiCr/Cr media showed a symmetric M-type curve and the peak height decreased with intergranular coupling.2 In addition, the peak position also changed systematically with grain decoupling. M-type curves were also observed when the underlayer Cr thickness was varied, but the peak location remained unchanged. Results from Ba-ferrite media prepared with different packing densities exhibit similar curves as those for CoNiCr/Cr media. However, oriented Ba-ferrite media prepared by having a magnetic field applied at 30° and 60° with respect to the film plane show a very unique behavior. In contrast, CoNi films which were prepared by oblique evaporation in the presence of oxygen showed a canted columnar morphology with an easy axis of magnetization out of the film plane. The resultant angular coercivity featured a shifted M-type unsymmetric curve, and the shift angle increased with the oxygen content in the film. It is noted that at high O2 concentrations the curve deviates significantly from a shifted M-type nature. The microstructures of the aforementioned media will also be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344810
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  • 5
    Electronic Resource
    Electronic Resource
    Delta-M, vertical component, and media noise of NiP- and Cr-underlayer media for longitudinal recording : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5542-5544 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Media having Cr-underlayer and NiP-underlayer were compared using transmission electron microscopy (TEM), delta-M, torque (vertical component), and media noise measurements. TEM micrographs show that NiP-underlayer media were more isolated than Cr-underlayer media. Of the Cr-underlayer media, CoCrTa media seem to exhibit grain isolation. The grain size of NiP-underlayer media was smaller (30 nm) than that of Cr-underlayer media (60 nm). Results indicate that media with isolated grains seem to have higher vertical component than media with more continuous grains. The NiP-underlayer media exhibits lower media noise than the Cr-underlayer media. This is attributed to smaller and more isolated grains in the NiP-underlayer media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353644
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of microstructural features on media noise in longitudinal recording media : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5566-5568 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High-resolution transmission-electron microscopy (HRTEM) has been used to analyze CoCrTa, CoCrPt, and CoNiCrPt alloy thin films deposited under similar conditions onto NiP plated Al substrates with a Cr underlayer. Apparent ∼50 nm Co alloy grains observed by bright field TEM are found to be clusters of smaller 10–20 nm grains with a common growth orientation. Subtle differences have also been observed in the stacking fault density, Co alloy fcc phase concentration, lattice mismatch, and grain separation in the films. In particular, HRTEM shows that the CoCrTa film has clear physical separation between the 10 and 20 nm grains, which is not observed in the other media. Despite similar hysteresis loop properties, the signal-to-noise ratio of CoCrTa is 2.3 dB higher than CoCrPt and 4.6 dB higher than CoNiCrPt. Small isolated grains have been shown to improve media noise, as is observed in CoCrTa media.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353652
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  • 7
    Electronic Resource
    Electronic Resource
    The role of stress-induced anisotropy in longitudinal thin film magnetic recording media : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 5342-5344 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measurements of stress and magnetostriction have been made in longitudinal CoCrTa magnetic recording media. The stress in Cr and CoCrTa/Cr films deposited onto grooved substrates is higher parallel to the grooves compared to perpendicular to the grooves by up to a few hundred MPa. Combined with a magnetostriction coefficient of −3×10−5 in CoCr10Ta6/Cr, magnetostriction makes a contribution to the in-plane anisotropy observed in such media. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361914
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  • 8
    Electronic Resource
    Electronic Resource
    Noise properties and microstructure of oriented CoCrTa/Cr media : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6144-6146 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Magnetic and noise properties of oriented CoCrTa/Cr media sputtered at temperatures from ambient to 250 °C were studied and correlated with microstructural data from HRSEM and HRTEM micrographs. Coercivity increases monotonically and loop squareness decreases with substrate temperature. Transition and uniform magnetization noise power are highest for media sputtered at 150 °C. Micrographs and noise powers show that the media sputtered at 150 °C is relatively highly exchange-coupled. Media sputtered below 150 °C shows topographic isolation, and those sputtered above 150 °C exhibit increasing intergranular isolation of about 10 A(ring) and thus lower exchange. Coercivity varies linearly but exchange drops abruptly at high temperature. Other mechanisms besides exchange contribute to the coercivity variation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.355436
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  • 9
    Electronic Resource
    Electronic Resource
    The role of NiAl underlayers in longitudinal recording media (abstract) : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4369-4369 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: NiAl has been proposed as a replacement for the Cr underlayer in longitudinal recording media.1 NiAl has a B2 ordered structure with a lattice parameter close to that of Cr. Hence the same epitaxial relationships that exist in CoCrPt/Cr could also exist in CoCrPt/NiAl. Although high coercivity media have been made using a NiAl underlayer, a detailed microstructural study of the CoCrPt/NiAl is lacking. We have investigated the crystal orientation and epitaxial relationships in CoCrPt/NiAl bilayers deposited by DCM sputtering at a range of deposition temperatures up to 250 °C and sputter rates of 0.5–10 nm/s. Samples were examined by high resolution transmission electron microscopy in cross section and plan view. None of the samples showed the (002) NiAl/(11¨20)Co orientation that would be expected by analogy to CoCrPt/Cr films deposited at high temperatures. The CoCrPt crystals in the CoCrPt/NiAl are oriented with their c axes at a range of angles to the film plane, accounting for the lower squareness (Sq) of the magnetic hysteresis loop compared to samples on Cr underlayers. There is no evidence of the "bicrystal" structure in CoCrPt/NiAl as is seen on films grown on Cr.2 Grain size in NiAl is smaller than in Cr giving a smaller grain size in the CoCrPt overlayer and potentially lower medium noise. However, coercivity of CoCrPt/NiAl is lower than CoCrPt/Cr. The coercivity increases as the NiAl film thickness increases, and this is believed to be caused by topographic isolation of the magnetic grains.3 Recording measurements on CoCrPt/NiAl and CoCrPt/Cr media show that noise is lower in isotropic media made on the NiAl underlayer compared to oriented media made on the Cr underlayer. The microstructural results will be compared with previously published results on NiAl underlayers and the utility of NiAl as an underlayer in high density media will be assessed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364825
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  • 10
    Electronic Resource
    Electronic Resource
    Low-noise metal medium for high-density longitudinal recording (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 3260-3262 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-noise medium that shows potential for future high-density longitudinal magnetic recording applications has been prepared and studied. The disk consists of a CoCr-based ternary alloy and a few percent of a third transition metal sputter deposited on a Cr underlayer. The media noise power is low and nearly frequency independent up to 80 kfci, in sharp contrast to the noise power spectra typical of metal films. Because of the exceptionally low media noise, we have obtained signal-to-noise ratios (SNR) greater than 35 dB up to 30 kfci on media having a 70% amplitude density (D70) of 20 kfci. Other characteristics of the media include overwrite better than −35 dB, saturation magnetization of 500 emu/cm3, and coercivity of 1300 Oe. The grain diameter, coercivity, and D70 depend strongly upon the Cr underlayer thickness. The data suggest that the low-noise results from reduced intergranular exchange coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340805
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