Magnetization and susceptibility measurements on pseudobinary alloys Tb0.25Fe0.75−xAlxand Tb0.105Fe0.895−xAlxare reported for temperatures from 1.6 K to about room temperature. The magnetization behavior in the ordered regime indicates that the coupling scheme between the rare‐earth and the transition‐metal moments stays an antiferromagnetic one on Al substitution for the latter. An unusual magnetization behavior is observed at the lowest temperatures (1.6–10 K). Here strongS‐type saturation develops partly with spontaneous increases of magnetization at critical fields of the order of 20 kOe. This is a result of highly energetic domain walls connected with high anisotropy and disorder on crystallographic sites. Coercive forces up to about 14 kOe are observed in the pseudobinary region at 4.2 K.