Magnetic and R/W properties of CoPt-SiO2 granular media

We fabricated Co80Pt20-SiO2/Cr granular media by sputtering and studied their structure and their magnetic and read/write (R/W) properties while varying the volume ratio of CoPt to SiO2. Transmission electron microscopy (TEM) images revealed that the diameter of CoPt particles increased with an increase in volume ratio. The maximum coercivity (about 2700 Oe) was obtained at 65vol% of CoPt. On the other hand,at over 40vol% of CoPt media, the signal to media noise ratio (S/N-m) rapidly decreased with an increase in the volume ratio. This indicates that media with finer grains exhibit low noise. In the same way, the instability of the magnetization was diminished with an increase in volume. This instability is very sensitive to the grain size of CoPt.