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Increases in recording areal density have propelled the disk drive industry in the last dozen years. Several studies and research programs strive to accomplish an areal density of 1 Tb/[in.sup.2]. At present, the future of the hard disk drive technology appears predicated on monotonic and unbound areal density growth. The system consequences of using large areal densities are the subject of this paper. It is argued that the limited signal-to-noise ratio (SNR) predicted at 1 Tb/[in.sup.2], as well as the extreme mechanical demands on the system, will cause the user capacity not to grow linearly with areal density, as has been the case in the past. This is due, among other reasons, to the increased servo overhead, the increased error-correction code overhead, and the mechanical requirements that compel the reduction of the size of the mechanism. Without casting in doubt the feasibility of magnetic bit recording at 1 Tb/[in.sup.2], scaling laws nevertheless show that there may be limited rewards for the technical efforts directed toward accomplishing 1 Tb/[in.sup.2],. Unless the system SNR can be maintained at about 18 dB, areal density gains will not result in proportional user-capacity gains. Index Terms--Digital magnetic recording, disk drive, recording limits, scaling, servo systems, signal-to-noise ratio (SNR), track misregistration.

Measurements were made on the variation of the noise power and signal with the widths of written micro tracks in high areal density recording systems. A analysis was then made on the width of these recorded micro tracks and an equivalent reader width. Results were compared with the prediction that the jitter varies as the inverse square root of the read track width. For two head-media combinations, the jitter exponents were found to be -0.34 and -0.43.

We have simultaneously demonstrated high areal density and high data rate, in an experiment that closely mimics the operation of disc drive products. The system involves thin-film media, GMR merged heads, broad bandwidth electronics, and an EPR4 channel with post-processing. The results presented reflect a statistical sample of components, rather than one-of-a-kind devices. In order to determine the areal density accomplished, we demanded that the bit error rate performance be insensitive to significant deviations of the head position from the recorded track center. We present a thorough description of the components and the SNR budget. The areal density accomplished varies between 15.1 Gb/[in.sup.2] at 193 Mb/s, and 17.1 Gb/[in.sup.2] at 214 Mb/s. A series of areal density capability assessments was obtained by applying various margin conditions. This was done to demonstrate robust experimental results. The outcome of this work may be applied to product development. Index Terms--Recording heads, recording media, recording systems.

Presents information on a study which made measurements using various head-media combinations of the variation of the media jitter with recorded track width in magnetic recording systems. Theory and experimental method; Results and discussion; Conclusions.

Presents information on a study which measured the magnetization fluctuations of uniformly magnetized media in sputtered CoP thin films as a function of Cr underlayer thickness. Experimental procedure; Results and discussion; Conclusions.