Substituent effects in Nd 2Fe 14B-based alloys interpreted on a crystal field model

Abstract

The substitution of iron in Nd 2Fe 14B by various elements leads to a change in spin reorientation temperature T sr . The changes in T sr observed experimentally bear no direct relationship to the anisotropy of the transition metal sublattices, as one might superficially have expected. This suggests that crystal field effects are the primary cause of the changes in T sr . The effects observed are accounted for using a hamiltonian of the form H = B 2 0O 2 0 + B 4 0O 4 0 + 2(g − 1)μ B¦H exch¦ It is shown that the substituent dependence of T sr can be explained by crystal field theory, using a single-ion model. Specifically, changes in T sr can be related to changes in ¦H exch¦ and hence related to the magnetic moment of the transition metal sublattices.