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Multilayer Pt/CoCrTa thin-film structures have been prepared which display little intergranular exchange coupling and nearly 100% remanence in the perpendicular direction. Magnetic recordings of continuous square wave patterns have been made and characterized using an inductive contact recording transducer and by magnetic force microscopy. Written transitions appear to retain good fidelity at more than 300 000 transitions per inch. With exchange isolation of the grains, media noise becomes negligible relative to thermal noise from the recording system electronics. Analysis of magnetic force microscopy images yields a signal to integrated noise ratio of 17 dB at 309 000 transitions per inch written in a 4 μm wide track, which is comparable to a measured signal to total noise ratio of 8 dB at 350 000 reversals per inch measured using an inductive transducer at 100 in./s. These results are contrasted with observations on exchange coupled Pt/Co multilayers.

A procedure for removing cumulative drift and white noise from scanning probe microscope images has been constructed. Smooth amorphous carbon overcoats on superpolished hard disk media in particular were examined using a scanning probe microscope. The surfaces typically had a ∼1 nm rms roughness over a scan length of 10 μm. The low roughness yielded a relatively low signal to noise ratio in the unfiltered image. While a conventional filter removes a great deal of noise, an optimal Fourier (Wiener) filter that more selectively removes noise from the image is discussed. White noise and drift were modeled and their contributions to the power spectrum are estimated, resulting in an open clamshell-shaped two-dimensional filter. The effect of the filter was demonstrated by subjecting filtered images of unworn and worn areas to a smooth surface to second derivative calculations in different directions. Anisotropy in the wear process associated with the wear direction is apparent in the optimally filtered images.

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