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-fi lm media (L1: H-c=2500 Oe, L2: 2850 Oe), and perpendicular thin-film m edia (P1: H-c=2830 Oe, P2: H-c=3780 Oe) were investigated using magnet ic force microscope (MFM). For the longitudinal media, insufficient wr iting is responsible for limiting the detectable density. By reducing the head fly height from 3 to 2 microinches, the maximum detectable de nsity of L1 is increased from 7000 to 10 500 fr/mm. At this density th e well-defined track edge disappears and a complete bit collapse occur s as the hit length becomes much smaller than the average domain size observed in the dc-saturation remanent state. In the case of perpendic ular media, contact recording provides sufficient writing and a well-d efined track edge at densities above 10 000 fr/mm for both media. A ma ximum detectable density about 12 000 fr/mm is obtained in both media. At higher recording densities, domain refinement takes place but magn etic interactions within the track also cause the formation of large d omains which eventually destroys the bit periodicity. (C) 1996 America n Institute of Physics.