On the grain-boundary phase in iron rare-earth boron magnets

Results of structural and microanalytical studies on sintered iron rare-earth boron permanent magnets are presented in this paper. It is shown that the structure of the phase present at the two-grain boundaries is the same as that of the phase at the three-grain junctions; both are fcc with a lattice parameter of 5.24 Å. It is also shown that this fcc phase is stabilized by the presence of significant quantities of oxygen. The possible effects of thin foil preparation by ion milling techniques in producing the observed bcc phase are also briefly discussed.