Zh. Cheng et al., MAGNETISM, PHASE-COMPOSITION, AND HYPERFINE FIELDS OF MELT-SPUN ND-FE-B ALLOYS WITH A A FEW PERCENT OF NEODYMIUM, Physical review. B, Condensed matter, 52(13), 1995, pp. 9427-9436
It is possible that melt-spun Nd-Fe-B alloys with a few percent of neo
dymium can be used as a raw material for inexpensive and bonded perman
ent magnets. After an appropriate heat treatment, melt-spun Nd4Fe77.5B
18.5 alloy has a coercive field of 3 kOe, a remanent magnetization of
12.5 kG, and an energy product of 13 MG Oe. However, at present, there
is some debate on the origin of its hard magnetic properties. In the
present work, the phase composition, magnetism, and hyperfine fields o
f melt-spun Nd-Fe-B alloys are studied. The effect of rare-earth eleme
nt substitution for Nd, such as Pr, Gd, and Dy, on B-11 and Fe-57 magn
etic hyperfine fields is also investigated. On the basis of the experi
mental results, the origin of the hard magnetic properties is discusse
d. The results indicate that (1) the melt-spun Nd-Fe-B alloys with a l
ow Nd concentration annealed under an optimal heat treatment consist o
f body-centered-tetragonal Fe3B (bct-Fe3B) and a few percent of alpha-
Fe and no Nd2Fe14B magnetically hard phase; (2) about 5 at. % Fe atoms
in Fe-III(8g) site of bct-Fe3B are replaced by Nd atoms in the sample
s annealed under optimal condition. NMR radio frequency (rf) enhanceme
nt effect results demonstrate that bct-Fe3B containing Nd atoms has be
tter permanent magnetic properties; (3) the substitution of some rare-
earth elements, such as Pr, Gd, and Dy, does not influence the hyperfi
ne field for Fe-57 in alpha-Fe; however, the hyperfine held for B-11 i
n bct-Fe3B increases with the addition of Gd or Dy. Thus, it can be co
ncluded that the hard magnetic properties of melt-spun Nd-Fe-B with a
few percent of neodymium result from bct-Fe3B containing Nd atoms, and
not from the presence of the Nd2Fe14B magnetically hard phase.