Amorphous rare earth-transition metal films as media of magneto-optical memory are described. Improvements of amorphous GdCo film in stabilizing recorded bits and in making uniform film were performed. High speed recording and reading experiment were carried out on GdCo disk of 150 mm in diameter, and excellent stability of recorded bits, considerable uniformity, and high sensitivity for recording were confirmed. Thermal stability and spectra of Kerr rotation angle of GdCo film were also measured. It is shown that GdCo film is very promising material for magneto-optical memory.