MFM analysis of recorded bit patterns of perpendicular media

Read/write characteristics of a perpendicular double-layered medium with various thicknesses of soft magnetic layer δ soft using a ring head were investigated by analyzing the MFM image of the recorded bit pattern and reproduced waveform. It was found that the recording bits were written by the field of the head gap for the medium with δ soft of 20 nm and whole plane of the write pole for the medium with δ soft of 200 nm. It was also found that the bit pattern is disturbed by re-writing in recorded domain for the medium with δ soft of 20 nm and the track width expands for the medium with δ soft of 200 nm because of the effect of the head skew angle. The SNR of the medium with δ soft of 200 nm was 5 dB higher than that with δ soft 20 nm at a bit length of 0.5 μm.