Nippon Hoso' Kyokai

Mitsui Petrochemical Industries, Ltd.

Yuji Togami

Nobuo Saito

Kunihiko Mizumoto

Hirokazu Kejiura

Magnetooptical recording media according to the present invention are disclosed. By virtue of comprising films of Nd-Dy-Co, Nd-M-Fe or Nd-M-Fe-Co alloy system (in which M denotes Tb, Dy or Ho) having a magnetic easy axis perpendicular to the film, the present magnetooptical recording media have such advantages that there is not any fear of lowering magnetic properties owing to the oxidation of the alloy films, and that there is no need of heating substrates when said alloy films are intended to be formed on the substrates. Accordingly, these alloy films can be formed even on such substrates composed of organic materials such as plastics. Moreover, magnetooptical recording media which comprise the alloy films in accordance with the present invention have excellent magnetic properties such as perpendicular magnetic, anisotropic energy in direction normal to the film, coercive force and saturation magnetization, particularly in point of coercive force.

Magnetooptical recording media and processes for production thereof

A recording medium consists of a composite amorphous magnetic material layer comprising a rare earth metal and an iron family metal, the composition ratio thereof being nonuniform in the perpendicular direction. Because of the nonuniform composition ratio, a minute magnetic domain can be formed stably, so that thermo magnetic recording at extremely high density and sensitivity can be effected. Where GdFe is employed as a suitable material, the thickness of a portion of the magnetic layer, which portion has a larger perpendicular magnetic anisotropy caused by the nonuniform composition ratio, is increased preferably in comparison with the other portion. Uniform thermo magnetic recording can be performed on the large area medium by covering the same with a transparent dielectric material layer having nonuniform thickness.

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Isehara, Japan

Yuji Togami