An investigation of amorphous Tb-Fe thin films for magneto-optic memory application

Amorphous Tb
x
Fe
1-x
(
0.16 < x < 0.35
) thin films produced by rf co-sputtering have been investigated for magneto-optic memory media application. The anisotropy, hysteresis and coercivity of the films were investigated as a function of composition and film thickness. The sputtered films were overcoated with thermally evaporated SiO. The effect of SiO thickness on the Kerr magneto-optic enhancement and the reflectivity was also measured. It was found that the magnetization and coercivity of those films having perpendicular anisotropy change dramatically not only with target composition but also with film thickness. Thin films having a high hysteresis loop squareness and a coercivity appropriate for magneto-optic recording (500 to 2000 Oe.) were produced from film compositions near the compensation composition of 22.3 at. % Tb. Thermomagnetic writing and reading of the TbFe films were made with a GaAs laser. The results show that the films have a high writing sensitivity (threshold energy of 0.2 nJ and saturation energy of 0.3 nJ) and a high reading contrast for bit sizes of 1 micron.