Studies on the exchange interactions in R2Fe14B, R2Fe14C and R2Co14B by molecular field theory

Abstract

The intra- and inter-sublattice exchange interactions in three series of permanent magnetic materials (R2FC14B, R2Fe14C and R2CO14B, R = rare earth elements) have been studied on the basis of molecular field theory. The effective exchange coupling constant (JCoCo) of Co sublattices in R2CO14B is about 16.61 × 10-22 J, which is nearly three times the values (JFeFe) of Fe sublattices in both R2Fe14B and R2Fe14C. The effective exchange coupling constants (JRT) between rare earth (R) and transition metal (T) are not constant across the series but dependent on the nature of R atoms, which is different from the usual assumption that the JRT are constant across the series due to the similarities of band structures for all R atoms. The molecular fields acting on the rare earth ions are also calculated. The maximum molecular fields are found for R = Sm in each series. © 1997 Published by Elsevier Science Ltd.