Noise and overwrite characteristics for perpendicular magnetic recording on a sputtered Co‐Cr medium

This paper describes noise, overwrite, and pattern peakshift characteristics for a Co‐Cr medium that is used in perpendicular magnetic recording by means of a ring head. Uniform Co‐Cr (20 wt% Cr) films of about 1 μm thickness were formed by rf sputtering on A1 disk substrates, whose saturation magnetization and coercive field were 205 emu/cc and 700 Oe, respectively. Magnetic recording tests were performed for them using a Mn‐Zn ferrite ring head of 0.28‐μm gap length and 100‐μm track width at a relative speed of 2.5 m/s. The maximum D50 recording density was 70 kBPI, with a signal‐to‐noise ratio of 40 dB at 60 kBPI. Overwrite characteristics were measured by writing a 66 kBPI signal over a 35 kBPI signal that had previously been written in. The ratio of the output of the 66 kBPI signal to that of the remaining 35 kBPI signal was 24 dB. The peakshift for the worst pattern in MFM coding was 50% of the detection window at 60 kBPI. From these results, it was deduced that the Co‐Cr medium described above is f...