The magnetic properties and magnetooptic effects of amorphous DyFeCo thin films with various compositions and thicknesses were investigated. The product of magnetization times coercive force of 15-30-nm-thick DyFeCo film gave a high value of 2.5-3 erg/cm3, comparable to that of Tb-enriched rare earth (RE) transition metal (TM) films. The dynamic characteristics of a quadrilayered magnetooptical disk having a reflective layer, i.e., carrier-to-noise ratio (C/N), optimum recording power and jitter were also evaluated. A high reproducing 60-dB C/N performance, comparable to that of Tb-enriched RE-TM films, was obtained by the 15-30-nm-thick DyFeCo films having a room temperature compensation composition. It is concluded that the use of this film is as efficient as the use of Tb films, while at the same time being much more inexpensive.