Magnetic hardening of nanocrystalline Sm-Fe-Mo synthesized by mechanical alloying

Materials based on rare-earth and iron have drawn much attention due to their high performance properties for permanent magnet application. The structural and magnetic properties of Sm-2(Fe, Mo)(17) and its carbide are investigated by means of powder X-ray diffraction, magnetic measurements and transmission electron microscopy (TEM). In this work, the Rietveld analysis reveals a phase transformation obtained by an appropriate heat treatment. The structure of these new phases is hexagonal. Moreover, it points out a lattice expansion along the c axis after Mo substitution for Fe and reveals 2e preferential occupation for Mo atoms in the 2/17 hexagonal precursor (1/9). Upon carbonation, the lattice expansion favors the Curie temperature increase for the novel 1/9 carbide. The Curie temperature and the coercive field of the 1/9 carbides are higher than those of 2/17 ones. This makes the hexagonal precursor a competitive candidate for use as permanent magnet.