TRIPLE-LAYERED NDCO AMORPHOUS-ALLOY FILMS FOR MAGNETOOPTICAL MEDIA

Magneto-optical recording materials with high remanent Kerr rotation at a short wavelength were successfully obtained in a trilayer form. NdCo amorphous films with an in-plane magnetization were sandwiched between TbFeCo amorphous films with strong perpendicular anisotropy and high coercivity. The thickness of the top layer of the TbFeCo film facing an incident laser beam is less than the light-penetration depth. Triple-layered films [Tb18Fe49Co33 (5 nm thickness)/Nd18Co82(10 nm)/Tb18Fe49Co33(200 nm)] thus obtained show a remanent Kerr rotation angle theta-Kr = 0.37-degrees-0.46-degrees at wavelength lambda = 400-850 nm, coercivity H(c) = 2 kOe, and good square loop (M(r)/M(s) = 1). The figure of merit square-root-R-theta-K, where R is reflectivity, is 0.24-0.31 at lambda = 400-850 nm, which is higher than that of conventional TbFeCo amorphous films (square-root-R-theta-K = 0.12-0.27 at lambda = 400-850 nm).