Magnetic Field Characteristics in the Quadri-Layered M-O Film with Overwritability

The authors investigated the external magnetic field characteristics of exchange-coupled quadrilayer magnetooptic film in direct overwriting by optical modulation. The external field dependence of the recording characteristics was studied through the temperature dependence of the reversal field and the mechanism of direct overwriting. In direct overwriting by optical modulation, an upper limit to the external field exists due to the "low" process. Here the process of initialization of the writing layer, unique to the quadrilayer film, did not affect the lower limit of the external field. A wide external field margin was obtained under conditions of practical use, and effective fluctuations in the external field did not affect the recording laser power margin.