Magnetic force microscopy images of ultrahigh-density bit patterns recorded on high-coercivity longitudinal and perpendicular thin-film media

Magnetic bit patterns recorded on high-coercivity longitudinal thin-film media (L1: H-c=2500 Oe, L2: 2850 Oe), and perpendicular thin-film media (P1: H-c=2830 Oe, P2: H-c=3780 Oe) were investigated using magnetic force microscope (MFM). For the longitudinal media, insufficient writing is responsible for limiting the detectable density. By reducing the head fly height from 3 to 2 microinches, the maximum detectable density of L1 is increased from 7000 to 10 500 fr/mm. At this density the well-defined track edge disappears and a complete bit collapse occurs as the hit length becomes much smaller than the average domain size observed in the dc-saturation remanent state. In the case of perpendicular media, contact recording provides sufficient writing and a well-defined track edge at densities above 10 000 fr/mm for both media. A maximum detectable density about 12 000 fr/mm is obtained in both media. At higher recording densities, domain refinement takes place but magnetic interactions within the track also cause the formation of large domains which eventually destroys the bit periodicity. (C) 1996 American Institute of Physics.