MFM studies of recording phenomena in high density longitudinal recordings

The Magnetic Force Microscopy (MFM) technique is demonstrated to provide quantitative information on not only micromagnetics but also on recording performance. A novel method is introduced for analyzing MFM images of recorded bit patterns to determine recording parameters such as signal and signal-to-noise ratio. The results are compared with those measured by a read head. Both signal and signal-to-noise ratio are found to be higher in the CoCrTaPt/CrMo medium than in CoCrTa/Cr medium for linear densities greater than 150 kfci. Recorded patterns can be observed in CoCrTaPt for linear densities up to 370 kfci while the patterns in CoCrTa start to deteriorate for densities higher than 250 kfci. Better high density performance of CoCrTaPt results from the finer structure of an isolated recorded transition which is attributed to reduced magnetostatic and exchange intergranular interactions. The direct overwrite patterns for CoCrTaPt exhibit narrower erase bands and less interactions between the old and new data; the overwrite at 232 kfci is 28 dB.