Longitudinal Recording Media Research Articles

Effects of argon pressure and substrate heating on the chromium underlayer used for high-density longitudinal CoNiCr media

Sputtered CoNiCr on Cr is one of the preferred material systems for high-density longitudinal recording media. dc magnetron sputtered Cr films, on Al substrates, were investigated for the effects of argon pressure and substrate temperature on the microstructure. High-resolution scanning electron micrographs reveal that the films made at lower argon pressures have acicular-shaped grains changing to faceted grain structures at higher argon pressures. The effect of substrate heating prior to deposition was to change the structure from acicular shape to cubic shape. X-ray diffraction work reveals a bcc(110) orientation for films deposited at lower argon pressures changing to a mixed phase at higher argon pressures. Increased substrate temperature caused a mixture of (110) and (200) orientation.

Longitudinal and perpendicular magnetic thin film media noise

Comparison of the magnetic media noise measured for perpendicular and longitudinal Co-Cr media producing the same signal amplitude indicates that the perpendicular media noise is smaller than the longitudinal media noise in both the kilohertz and the megahertz frequency spectra. A simple theory based on magnetic domain wall distortion is presented which yields results that are consistent with these experimental observations. Whereas previous researchers have measured a 6 dB difference in the megahertz range, we have found that the perpendicular recording media noise is at least 2 to 3 dB lower than the longitudinal recording media noise in the kilohertz range.

Noise in high performance thin-film longitudinal magnetic recording media

The problem of noise in thin-film longitudinal media is analyzed experimentally and theoretically. The physical mechanism for the noise is shown to be fluctuations in the geometry of the zig-zag transitions separating bit cells. The shifted-transition noise model is introduced as a means of quantifying the noise processes. Spatial, spectral, and autocorrelation properties are introduced. A calculation of the RMS noise voltage yields the characteristic noise versus density curves found experimentally, and clarifies their interpretation with respect to the signal-to-noise ratio. The corresponding experimental data for several plated and sputtered media are presented and analyzed in the light of the model predictions.

Amorphous CoSm thin films: A new material for high density longitudinal recording

Amorphous thin films of Sm <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">100-x</inf> Co <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">75 &lt; x &lt; 90</tex> ) were prepared by vacuum deposition in a magnetic field. The preparation conditions and magnetic properties are described. The films exhibit a pronounced uniaxial anisotropy in the film plane with a rectangular shaped hysteresis loop. The magnetization and coercivity are mainly determined by composition. With increasing Sm content the coercivity increases from 30 to 100 kA/m. The magnetization reversal is studied by the angular dependence of the hysteresis properties and by domain observations indicating a nonuniform reversal process. The recording performance measured on 5-in disks shows an improvement in recording density and signal-to-noise ratio compared to traditional longitudinal recording media.