Magneto-optical disk

Stock material or miscellaneous articles – Circular sheet or circular blank – Recording medium or carrier

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428 646, 428 647, 428 649, 428336, 428694ML, 428694DE, 428694RE, 428694NF, 428694KL, 428694AM, 428698, 428704, 428900, 360131, 365122, 369 13, 369288, G11B 566

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056678622

ABSTRACT:
A magneto-optical disk having a four-layer structure formed of a first protective dielectric layer, a recording magnetic layer, a second protective dielectric layer and a reflective metal layer is disclosed. The constraints for the film thicknesses of the various layers are determined not only from the optical and magneto-optical aspects, but from the aspect of the dynamic thermal response.
The recording magnetic layer is a magnetic layer mainly formed of TbFeCo and having a film thickness of not less than 180 .ANG. and not more than 280 .ANG.. The first protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.2 and not more than 0.35 times the wavelength of the laser light employed. The second protective dielectric layer is a nitride film having a film thickness such that the product of its refractive index and the film thickness is not less than 0.1 and not more than 0.15 times the wavelength of the laser light employed. The the reflective metal layer is a metal layer having a film thickness of not less than 500 .ANG. and not more than 1000 .ANG., with the metal being electro-chemically less noble than the material of the recording magnetic layer and having a reflectivity at the boundary with the second protective dielectric material of not less than 70%.

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Gueugnon, C. et al. "Computation of optical properties of multilayered media for magnetooptical memories." J. Appl. Phys., vol. 57 (Apr. 15, 1985) pp. 3891-3893.
Mansuripur, M. et al., "Optimum Disk Structures and Energetics of Domain Formation in magnetooptical recording." IEEE Transactions on Magnetics, vol. 18 (Nov. 6, 1982) pp. 1241-1243.
Mansuriper, M. et al., "Erasable Optical Disks for Data Storage:Principles and Applications", Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, pp. 80-84.
Chen, T. et al. "Thickness Dependence of Magneto-Optic Effects in Tb-Fe Film". Optical Data Storage Conference at Incline Village, Nev., Jan. 17-20, 1983.
Proceedings of the SPIE, vol. 420, 1983; "Magneto-Optic Recording", by M. Mansuripur et al., pp. 222-230.

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