Hydrogenated amorphous carbon dielectric coatings for magneto-optic data storage media

Thin films of hydrogenated amorphous carbon (a-C) have been evaluated as quarter-wave, antireflection dielectric coatings for application in magneto-optic data storage media. The films, which are produced by plasma deposition from methane, have low optical absorption at 830 nm wavelength, high refractive index (n≊2.1), and provide enhancement of the polar Kerr rotation (θk) when used in conjunction with rare-earth-transition-metal (RE-TM), TbFe, or TbFeCo alloys. The chemical stability, inertness, and homogeneity of the carbon films makes them effective diffusion barriers to oxygen or water vapor and thus provides excellent protection against environmental oxidation of the RE-TM layer. Dynamic disk performance data show improved write sensitivity of the media when used with a-C dielectric layers.