Magnetooptical recording medium
AssigneeNikon Corporation
InventorHaruhisa Iida
Life of this patent
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Abstract
A magnetooptical recording medium includes a substrate formed with a guide groove for tracking a laser beam, and first and second magnetic layers which are stacked on the substrate and each of which consists of an amorphous heavy rare earth-transition metal alloy. The first and second magnetic layers are magnetically coupled to each other. The first magnetic layer has a relatively high Curie temperature and a relatively low coercivity at room temperature, and the second magnetic layer has a relatively low Curie temperature and a relatively high coercivity at room temperature. The film thickness t.sub.1 of the first magnetic layer and the film thickness t.sub.2 of the second magnetic layer satisfy a condition t.sub.2 /t.sub.1 .gtoreq.2.5.
Claims1
A magnetooptical recording medium comprising:
- a substrate formed with a guide groove for tracking a laser beam;
- and
- first and second magnetic layers which are stacked on said substrate, the first magnetic layer consisting of GdFeCo and the second magnetic layer consisting of an amorphous heavy rare earth-transition metal alloy, said first and second magnetic layers being magnetically coupled to each other, said first magnetic layer having a Curie temperature that is higher than the Curie temperature of said second magnetic layer and having a coercivity at room temperature that is lower than the coercivity of said second magnetic layer at room temperature,
- wherein a film thickness t.sub.1 of said first magnetic layer and a film thickness t.sub.2 of said second magnetic layer satisfy:
- t.sub.2 /t.sub.1 .gtoreq.2.5.
Dependencies are inferred from the claim text.