Some rare earth-transition metal amorphous alloy films prepared by sputtering or evaporation have uniaxial anisotropy perpendicular to the film plane. These amorphous magnetic films are expected as magneto-optical memory material. Although amorphous TbFe magnetic film has a high coercivity and low Curie temperature, the signal level of magneto-optical readout is lower than other amorphous magnetic films. Therefore the higher magneto-optic properties (higher Kerr rotation angle) is desired.
For obtaining a higher Kerr rotation angle, amorphous TbFeCo films was studied. It is found that the suitable Co substitution for Fe caused the increase of the Kerr rotation angle of amorphous TbFeCo magnetic films and θk at 633 nm and 840 nm have peak values 0.42° and 0.52° at X=50 in Tb21(Fe100-XCoX)79, respectively.
Curie temperature of TbFeCo increased linearly with increasing Co concentration and its slope was about 3.6-4 degree.
From the temperature dependence of the Kerr rotation angle it is conjectured that, in Tb21(Fe100-XCoX)79, the transition metal magnetic moment at 0 k becomes a maximum at near X=30 as well as a maximum saturation magnetization in FeCo binary alloy.
