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A feasibility study of a magneto-optical(MO) disk for an NA 0.85 system is presented. The disk noise level in this system was relatively large compared to the conventional NA 0.55 system at the recording density corresponding to this spot size. Two methods were introduced for the improvement. One was the optimization of the groove structure, and the other was the reduction of the metal surface roughness. The former was found to be the typical noise source for optics for a narrower track pitch disk. A UV ashing apparatus was utilized for reduction of the noise. The latter noise source was characteristic for the surface MO recording, and the etching process was found effective for the improvement. By using both these methods, the noise level was drastically decreased, achieving high areal density of 7 Gb/inch2.

In order to investigate the vectorial magnetization process in magnetic recording media, a method of measuring the magnitude and the direction of remanent magnetization using a VSM is proposed. The magnitude and direction ψ of the remanent magnetization were measured as a function of the direction of applied field θ in Co-Cr thin-film media and a metal oblique-evaporated medium and metal particulate medium. The film thickness dependence of the relation between ψ and θ for Co-Cr sputtered film was measured and the thickness of the initial layer was estimated. The relation between ψ and θ was calculated by taking the distribution of the anisotropy fields and the easy axes into account. From the measurements and the calculations, it is shown that the relation between ψ and θ is strongly influenced by not only the saturation magnetization and the anisotropy field but also the distribution of the anisotropy fields and the easy axes.