Method and apparatus for reproducing data from a magneto-optical recording medium having a readout layer, transfer layer and recording layer

A reproducing apparatus for reproducing data recorded onto a magneto-optical recording medium, wherein said medium comprises:

• a base;
• a readout layer formed on said base, said readout layer having perpendicular magnetization in a temperature range between room temperature and Curie temperature;
• a transfer layer formed on said readout layer, said transfer layer is predominant in-plane magnetization at room temperature, and in which a transition occurs from in-plane magnetization to perpendicular magnetization at a temperature above room temperature;
• a recording layer formed on said transfer layer, said recording layer having a Curie temperature lower than the Curie temperature of the transfer layer and which exhibits perpendicular magnetization in a temperature range between room temperature and Curie temperature;
• and
• wherein said apparatus comprises:
• a magnetic field generation device to generate a subsidiary magnetic field which interacts only with said readout layer;
• wherein the subsidiary magnetic field being generated has an intensity that is higher than an intensity of the coercive force of said readout layer and less than an intensity of the exchange coupling force exerted from said recording layer and said transfer layer to said readout layer;
• a light projection means for projecting a reproducing light beam through first said base and then onto said readout layer so a portion of the magneto-optical recording medium, a central portion, is in a center of the beam spot of the reproducing light, so another portion of the magneto-optical recording medium, a surrounding portion, is within the beam spot and surrounds the central portion, so the in-plane to perpendicular magnetization transition occurs in the central portion of said transfer layer, so the central portion of the transfer layer is in a predetermined temperature range including the highest temperature in the transfer layer within the beam spot, and so the surrounding portion of the transfer layer is at a temperature below said temperature range, thus resulting that the exchange coupling force is exerted from said recording layer and said transfer layer to said readout layer in the central portion;
• and
• wherein said magnetic field generation device is operated while said light projection means projects said reproducing light beam onto said readout layer, so the magnetization direction is copied from said recording layer to said readout layer via said transfer layer by the exchange coupling force in the central portion, and the magnetization in said readout layer is arranged in the direction of the subsidiary magnetic field in the surrounding portion.