Abstract The low temperature magnetization of amorphous Fe x Pd 82− x Si 18, 2 ⩽ x ⩽ 25, approaches saturation like 1/ H. RKKY-type cluster-cluster interactions and single impurity effects are indicated. The effective strength of the RKKY interaction decreases with increasing x. The magnetization of both spin glass-like and weakly ferromagnetic alloys exhibits Bloch's T 3 2 dependence. The spin wave stiffness constants increase linearly with 2 ⩽ x ⩽ 25. The range of exchange interactions decreases with increasing x.