Magnetic properties of the BCC phase at grain boundaries in the Nd-Fe-B permanent magnet

Structural and magnetic studies have been carried out on a bcc phase that appears in melt-spun rare earth-iron based alloys during a heat treatment at temperatures ranging from 700K to 770K. It has been found that the bcc phase has a lattice constant very close to that for α-Fe and that it is a soft magnet with Curie temperatures in a 400-450K range. Relation of this phase to a bcc boundary phase in sintered Nd-Fe-B magnet and its role in the magnetic hardening mechanism in the Nd-Fe-B magnets is discussed.