Perpendicular Magnetic Recording Media on Various Hard-Disk Substrates
Co-Cr perpendicular media on rigid substrates were studied. We used untextured glass substrates for perpendicular magnetic hard disks, but the reproduced output at short wavelengths was influenced by the surface roughness of the magnetic recording media. We therefore fabricated Co-Cr perpendicular hard disk media deposited onto different substrates: untextured glass, silicon single crystal, chemically textured alumite, and Mn-Zn ferrite. We compared these substrates with respect to their crystallographic properties, head-to-medium spacing, and record/playback characteristics.
Faraday Rotation of Broad-Spectrum Polychromatic Light and Its Quantum Description
For polychromatic light having a broad spectrum width, the effective Faraday rotation angle ≪¿<inf>F</inf>≫ is defined operationally as ≪¿<inf>F</inf>≫ = ¿¿<sup>¿</sup><inf>F</inf>S<sup>¿</sup>P<sup>¿</sup>d¿/¿s<sup>¿</sup>p<sup>¿</sup>d¿. Here ¿<sup>¿</sup>, S<sup>¿</sup> and P<sup>¿</sup> are the Faraday rotation angle, photodetector sensitivity, and light intensity, respectively, at wavelength ¿. Integration is performed over the spectral width of the polychromatic light. From classical electromagnetic wave theory we derived the above equation, to which we gave a consistent quantum description of the photon image. Experiments on an FR-5 glass sample using a halogen lamp as a polychromatics light source supported our calculations.
Effect of third‐element additions on properties of Co‐Cr‐based films
The fundamental effects of adding several elements to the Co‐Cr system on the properties of Co‐Cr‐based films were extensively investigated. Tantalum, molybdenum, vanadium, and rhenium were chosen as the additives. A large amount of each element was added to a Co–17‐at. % Cr film. Ta addition improved the squareness and suppressed the in‐plane coercive force without lowering the perpendicular coercive force for the films with perpendicular magnetization. All the additives were effective in suppressing the grain growth. The ternary alloy films were likely to have finer grains than Co‐Cr films. Ta was found to be the most advantageous in a wide range of the content, from the total balance of squareness, coercive force, and grain size. The recording characteristics of Co‐Cr‐Ta films were also examined in comparison with those of Co‐Cr films. The recording density and the signal‐to‐noise ratio of Co‐Cr‐Ta films were appreciably higher than those of Co‐Cr films.