Magnetic properties of amorphous Fe100-XGdX (18≤X≤70) alloys were prepared by melt-quenching and analyzed by molecular field theory with twosublattice model. Spin structure is of simple ferrimagnetic ordering and the moment of Fe has about 2 μB with wide concentration range, which is conspicuously in contrast to that of amorphous thin film. Curie temperatures were higher than those for the thin films by about 60∼100 degrees. The temperature dependence of the magnetization can be fitted by the molecular field theory with three exchange constants as the fitting parameters. The results are discussed for concentration dependence of exchange parameters in comparison with thin film case.
