Over write capable magnetooptical recording method using two beams, and magnetooptical recording apparatus therefor

Claim 1

An over write capable magnetooptical recording apparatus using a multilayered magnetic recording medium that includes a first layer having a perpendicular magnetic anisotropy acting as a recording layer and a second layer having a perpendicular magnetic anisotropy acting as a reference layer, said first and second layers being coupled to each other so that an exchange coupling force influences said first and second layers, and comprising: (a) initial field applying means for applying initial field to at least a part of said medium without influencing the direction of magnetization of said first layer and so that the direction of magnetization of said second layer is aligned either upward or downward; (b) an optical system; (c) erasing means for applying an erasing laser beam through said optical system to said part of said medium after the applying of said initial field to said medium, said erasing means applying said erasing laser beam so that one of a bit having upward magnetization and a bit having downward magnetization is formed in a portion of said first layer corresponding to said part of said medium, the intensity of said erasing laser beam being a predetermined level; (d) writing means for applying a writing laser beam through said optical system to said part of said medium; (e) displacement means for providing relative displacement between said medium and said two laser beams of said erasing means and said writing means, said erasing means and said writing means being disposed so that said erasing means applies said erasing laser beam to said part of said medium prior to the applying of said writing laser beam to said part of said medium; (f) pulse modulating means for causing said writing means to pulse-modulate the intensity of said writing laser beam between a first level and a second level depending upon binary data to be recorded, said first level being higher than said predetermined level and causing said first layer to reach a predetermined temperature suitable for forming the other of said bits, said second level being equal to or lower than said predetermined level; and (g) bias field applying means for applying bias field to said part of said medium in order to form said other bit in the portion of said first layer corresponding to said part of said medium when said writing means applies said writing laser beam to said part.