Magneto-optical recording medium with amorphous alloy film layers

A magneto-optical recording medium comprising:

• a transparent substrate;
• a transparent interference layer formed on said transparent substrate;
• a first magneto-optical layer formed on said transparent interference layer, said first magneto-optical layer having a Curie temperature not lower than approximately 250.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force lower than 0.5 kilo-oersted at a temperature ranging from approximately 10.degree. C. to approximately 90.degree. C., and being an amorphous alloy film containing GdFeCo as the main component thereof with a thickness ranging from approximately 100 angstrom to approximately 400 angstrom;
• a second magneto-optical layer formed on said first magneto-optical layer, said second magneto-optical layer having a Curie temperature ranging from approximately 110.degree. C. to approximately 160.degree. C., exhibiting iron series transition metal dominant ferrimagnetism at a temperature ranging from approximately 10.degree. C. to approximately 90.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeCr as the main component thereof with a thickness not lower than approximately 50 angstrom;
• a third magneto-optical layer formed on said second magneto-optical layer, said third magneto-optical layer having a Curie temperature not lower than approximately 190.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force not lower than approximately 1.0 kilo-oersted at a temperature ranging from approximately 110.degree. C. to approximately 160.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeCoCr as the main component thereof with a thickness not lower than approximately 250 angstrom;
• and
• a dielectric protective layer formed on said third magneto-optical layer,
• said first magneto-optical layer, said second magneto-optical layer and said third magneto-optical layer being exchange-coupled at a temperature ranging from approximately 10.degree. C. to approximately 90.degree. C.,
• said first magneto-optical layer and said third magneto-optical layer being not magnetostatically coupled in an external magnetic field for reading use at a temperature at which magnetization of said second magneto-optical layer is substantially diminished, said eternal magnetic field being applied to said magneto-optical recording medium while a laser beam for reading use is moved relatively to said magneto-optical recording medium and irradiated through said transparent substrate to said first magneto-optical layer.

A magneto-optical recording medium comprising:

• a transparent substrate;
• a transparent interference layer formed on said transparent substrate;
• a first magneto-optical layer formed on said transparent interference layer, said first magnetooptical layer having a Curie temperature not lower than 250.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force lower than approximately 0.5 kilo-oersted at a temperature ranging from approximately 10.degree. C. to approximately 90.degree. C., and being an amorphous alloy film containing GdFeCo as the main component thereof with a thickness ranging from approximately 100 angstrom to approximately 200 angstrom;
• a second magneto-optical layer formed on said first magneto-optical layer, said second magneto-optical layer having a Curie temperature ranging from approximately 110.degree. C. to approximately 160.degree. C., exhibiting iron series transition metal dominant ferrimagnetism at a temperature ranging from approximately 10.degree. C. to approximately 90.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeNiCr as the main component thereof with a thickness not lower than 50 angstrom;
• a third magnetooptical layer formed on said second magnetooptical layer, said third magnetooptical layer having a Curie temperature not lower than 190.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force not lower than about 1.0 kilo-oersted at a temperature ranging from about 110.degree. C. to about 160.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeCoNiCr as the main component thereof with a thickness not lower than 250 angstrom;
• and
• a dielectric protective layer formed on said third magnetooptical layer,
• said first magnetooptical layer, said second magnetooptical layer and said third magnetooptical layer being exchange-coupled at a temperature ranging from about 10.degree. C. to about 90.degree. C., and
• said first magnetooptical layer and said third magnetooptical layer being not magnetostatically coupled in an external magnetic field for reading use at a temperature at which magnetization of said second magnetooptical layer is substantially diminished, said external magnetic field being-applied to said magnetooptical recording medium while a laser beam for reading use is moved relatively to said magnetooptical recording medium and irradiated through said transparent substrate to said first magnetooptical layer.

A magnetooptical recording medium comprising:

• a transparent substrate;
• a transparent interference layer formed on said transparent substrate;
• a first magnetooptical layer formed on said transparent interference layer, said first magnetooptical layer having a Curie temperature not lower than about 250.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force lower than 0.5 kilo-oersted at a temperature ranging from about 10.degree. C. to about 90.degree. C., and being an amorphous alloy film containing GdFeCo as the main component thereof with a thickness ranging from about 100 angstrom to about 400 angstrom;
• a second magnetooptical layer formed on said first magnetooptical layer, said second magnetooptical layer having a Curie temperature ranging from about 110.degree. C. to about 160.degree. C., exhibiting iron series transition metal dominant ferrimagnetism at a temperature ranging from about 10.degree. C. to about 90.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeTa as the main component thereof with a thickness not lower than 50 angstrom;
• a third magnetooptical layer formed on said second magnetooptical layer, said third magnetooptical layer having a Curie temperature not lower than 190.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a high coercive force not lower than 1.0 kilo-oersted at a temperature ranging from about 110.degree. C. to about 160.degree. C., and being an amorphous alloy film containing perpendicularly magnetizable TbFeCoTa as the main component thereof with a thickness not lower than 250 angstrom;
• and
• a dielectric protective layer formed on said third magnetooptical layer,
• said first magnetooptical layer, said second magnetooptical layer and said third magnetooptical layer being exchange-coupled at a temperature ranging from about 10.degree. C. to about 90.degree. C.,
• said first magnetooptical layer and said third magnetooptical layer being not magnetostatically coupled in an external magnetic field for reading use at a temperature at which a magnetization of said second magnetooptical layer is substantially diminished, said external magnetic field being applied to said magnetooptical recording medium while a laser beam for reading use is moved relatively to said magnetooptical recording medium and irradiated through said transparent substrate to said first magnetooptical layer.

A magnetooptical recording medium comprising:

• a transparent substrate;
• a transparent interference layer formed on said transparent substrate;
• a first magnetooptical layer formed on said transparent interference layer, said first magnetooptical layer having a Curie temperature not lower than 250.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force lower than 0.5 kilo-oersted at a temperature ranging from about 10.degree. C. to about 90.degree. C., and being an amorphous alloy film consisting essentially of an iron series transition metal and a rare earth-transition metal with a thickness ranging from about 100 angstrom to 400 angstrom;
• a second magnetooptical layer formed on said first magnetooptical layer, said second magnetooptical layer having a Curie temperature ranging from about 110.degree. C. to about 160.degree. C., exhibiting iron series transition metal dominant ferrimagnetism at a temperature ranging from about 10.degree. C. to about 90.degree. C., and being a perpendicularly magnetizable amorphous alloy film consisting essentially of an iron series transition metal and a rare earth transition metal with a thickness not lower than 50 angstrom;
• a third magnetooptical layer formed on said second magnetooptical layer, said third magnetooptical layer having a Curie temperature not lower than 190.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force not lower than 1.0 kilo-oersted at a temperature ranging from about 110.degree. C. to about 160.degree. C., and being a perpendicularly magnetizable amorphous alloy film containing an iron series transition metal and a rare earth transition metal with a thickness not lower than 250 angstrom;
• a fourth magnetooptical layer formed on said third magnetooptical layer, said fourth magnetooptical layer having a Curie temperature not lower than 250.degree. C., exhibiting iron series transition metal dominant ferrimagnetism with a coercive force lower than 0.5 kilo-oersted at a temperature ranging from about 10.degree. C. to about 90.degree. C., and being substantially an intra-surface-magnetizable amorphous alloy containing GdFeCo as the main component thereof;
• and
• a dielectric protective layer formed on said fourth magnetooptical layer,
• said first magnetooptical layer, said second magnetooptical layer and said third magnetooptical layer being exchange-coupled at a temperature ranging from about 10.degree. C. to about 90.degree. C.,
• said first magnetooptical layer and said third magnetooptical layer being not magnetostatically coupled in an external magnetic field for reading use at a temperature at which magnetization of said second magnetooptical layer is substantially diminished, said external magnetic field being applied to said magnetooptical recording medium while a laser beam for reading use is moved relatively to said magnetooptical recording medium and irradiated through said transparent substrate to said first magnetooptical layer.