Abstract
The time decay of magnetization (ΔM/ln t) and the irreversible susceptibility (X irr) were measured for Co-Cr/Ti perpendicular and Co-Cr-Pt-Ta/Cr longitudinal recording media in various reverse magnetic fields in the temperature range from 200 to 423 K. This experiment showed that ΔM/ln t of Co-Cr/Ti perpendicular recording media gradually increased with increasing temperature in a reverse magnetic field. In the case of Co-Cr/Ti perpendicular recording media, the value of the activation volume (Vact × Ms), which is correlated with the medium noise, is independent of the reverse magnetic field, in contrast to the tendency in Co-Cr-Pt-Ta/Cr longitudinal recording media. The temperature variation of the coercivity (Δ Hc/Δ T) of these recording media increased as (Vact × Ms) decreased, as in the case of rare-earth magnets.
