| 摘要 |
PURPOSE:To prevent the excessive deterioration in a reading out characteristic even if the thickness of a magnetic layer is reduced by freshly providing a 2nd dielectric layer and adequately setting the film thicknesses and refractive indices of the respective layers. CONSTITUTION:A 1st dielectric layer 2, the magnetic layer 3 and the 2nd dielectric layer 4 are successively provided on a transparent substrate 1 and the refractive indices of the 1st and 2nd dielectric layers are adjusted to >=2. The film thickness of the 2nd dielectric layer is so adjusted as to maximize the reading out performance index at the wavelength of the laser light to be used. The reading out performance index F refers to the value obtd. by multiplying the square root of an intensity reflectivity R by a magneto-optic Kerr rotating angle thetak and is designated as the quantity to indicate the defectiveness or non-defectiveness of the reading out characteristic when a medium is detected by using a photodetector such as PIN photodiode having a self-multiplying characteristic. The reason for adjusting the refractive indices of the 1st and 2nd dielectric layer to >=2 lies in that the effect of light interference is admittedly decreased if such indices are smaller than 2 and that the purpose of providing such dielectric layers is lost. |
