Magnetic force microscopy studies of ultrahigh density magnetic recording on longitudinal and perpendicular media

It has been demonstrated using magnetic force microscopy (MFM) that magnetic recording patterns with linear densities in excess of 230 kfci can be sustained by isotropic longitudinal media with H_c=2500 Oe and perpendicular media with H_c=1800 Oe. It was found that the size of magnetic cluster domains limited the linear recording density sustainable by a longitudinal medium and that the cluster size decreased with increasing medium coercivity. As the bit size approached the minimum cluster size observed in the magnetic background of longitudinal medium, the bits tended to percolate within the track resulting in a complete disappearance of a recorded pattern. In the case of the perpendicular medium, the bit transitions remained sharp at high densities. As the bit size approached minimum cluster domain size, the signal amplitude approached the noise amplitude thus limiting the detectability of the recorded bit pattern