Reproducing characteristics of perpendicular magnetic recording

The effects of magnetic properties and thickness of single-layer Co-Cr film media on perpendicular recording with a ring head are investigated. The effects of the reproducing head gap length and the reproducing head-to-medium spacing on reproduction are also discussed. Experiments are performed using ring heads for recording and reproducing and using single layer Co-Cr film media whose effective perpendicular anisotropy field Hk,eff from the in-plane hysteresis curve is greater than 5 kOe. The following results are obtained: (I) The reproduced voltage Ep at long wavelength is nearly proportional to the thickness δ of the medium and to the coercive force in the normal direction of the film. (2) Epis independent of the saturation magnetization Ms. (3) The -6dB wavelength λ50is independent of δ. (4) λ50gradually increases as or Msincreases. These results are well explained by a model of perpendicularly-recorded magnetization which assumes zero transition width and self-demagnetization in the medium. Calculations based on our model predict that the wavelength response of the reproduced voltage strongly depends on the reproducing head gap length and the reproducing head-to-medium spacing rather than on , Msand δ. An excellent high recording density (λ50of 0.45 μm or 113 kBPI) can be obtained by a medium and a head-to-medium interface suitable for high-density recording.