Abstract
Thickness dependence of noise characteristics have been investigated for CoCr_<19>Pt_<10> and CoCr_<17>Ta_4 single-layer perpendicular media. The maximum S/N ratios are observed for both-type media when the recording layer thickness is around 25 nm. Good correlation between the magnetic domain size observed by MFM and the noise value measured by MR head shows that it is necessary to decrease the magnetic domain size to reduce the medium noise. A fairly large magnetization fluctuations are observed in the MFM image of CoCrPt perpendicular media with high Mr/Ms ratio, which are expected to show low noise property because of the small volume fraction of reversed domains. This result indicates that the high Mr/Ms is not always a satisfactory condition to get a low noise perpendicular medium. Further study focusing on the magnetization structure is still necessary to improve the noise characteristics.
