Moessbauer effect and magnetization studies of Er-Fe-B permanent magnetic materials

Moessbauer and saturation magnetization studies have been carried out at room temperature on Er2-xYxFe14B and Er2Fe14-xSixB permanent magnetic materials with x = 0.0, 0.5, 1.0, 1.5 and 2.0. A simple charge transfer from the rare-earth sublattice to the 3d band of iron accounts for the observed increase in the saturation magnetization and 57Fe hyperfine field with the substitution of Y for Er. This can also be explained on the basis of the reduction in the strength of the Er-Fe negative exchange interaction and an increase in the Fe-Fe exchange interaction strength due to lattice expansion on Y substitution. The decrease in the saturation magnetization and the 57Fe hyperfine field when Fe is partially replaced by Si is attributed to the reduction in the number of Fe neighbours and also to the reduction in the Fe magnetic moment due to an effective charge transfer from Si to the Fe 3d band. The Fe sublattice magnetization is found to be slightly affected by the type of rare-earth ion in the rare-earth sublattice. (author)