Noise Characterization of Perpendicular Recording Media by Cluster Size Measurements

New methodology to obtain reliable correlation between magnetic cluster details measured using magnetic force microscopy (MFM) and noise in perpendicular recording media is reported. In addition to the ac demagnetized state, which is often studied by several researchers, magnetic clusters were examined at two other magnetic states of the recording medium to obtain details on thermally unstable and relatively nonreversible clusters that would increase noise and bit-error rates. The proposed method was employed to study magnetic clusters of media samples fabricated at different conditions. Measurements on various samples demonstrated that the MFM can be used to understand the thermally unstable and irreversible clusters in a perpendicular recording medium. A direct correlation between the signal-to-noise ratio of the medium measured using spin-stand and magnetic cluster details from MFM images is obtained. The trend can also be used to understand and distinguish the source of noise (such as writing issues or the media microstructure issues).