Metallic Gd1-xCox films (0.75 < × <0.85) obtained in the amorphous state by an rf-sputtering were investigated using the Kerr polar magneto-optic effect. These films exhibit perpendicular anisotropy sufficient to sustain magnetic cylindrical domains. The magnetic properties obtained with a Kerr hysteresigraph from these films can be described in terms of the wall energy model developed originally for nonmetallic single-crystal bubble material. An analysis based on a simple molecular field description of the magnetization and a mean field approximation of the exchange constant A gives estimates of the uniaxial anisotropy energy Ku. The results indicate that for the composition range studied A increases linearly from 5.7 to 6.6 (10-7 erg/cm), while Ku ranges between 1 and 7 (105 erg/cm3). The saturation magnetization Ms varies between 30 and 180 G. The moderate anisotropy (Q=Ku/ 2πMs2 = 1-9) and low wall motion coercivity of less than 1 Oe are favorable to bubble device applications. The effect of thermal and magnetic annealing on the magnetic properties is also discussed. © 1974 American Institute of Physics.