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We have investigated high-density magneto-optical recording on a conventionally structured disk with a diameter of 64 millimeters using magnetic field modulation to achieve a capacity of 650 Mbytes. With the groove conditions optimized, the jitter with cross-talk from adjacent tracks was 7.2% and the recording power margin including overwriting and crosswriting was ±20%. As a result of minimizing cross-talk, a sufficient tilt margin of ±0.82 degree and ±0.63 degree in the radial and tangential direction, respectively, was obtained.

SNR of a polycarbonate MO disk with a narrow track of 0.85 μm and with a quadrilayer structure was improved by optimizing and improving the groove geometry, film composition / thickness, and birefringence of the substrate. By using a 690 nm LD, an NA of 0.55, magnetic field modulation, and RLL(1,7) coding, a high areal recording density of 2.5 Gbit/in2 was obtained. Moreover, the PRML detection of PR(1,2,1) increased the density up to 2.9 Gbit/in2.