MAGNETISM, PHASE-COMPOSITION, AND HYPERFINE FIELDS OF MELT-SPUN ND-FE-B ALLOYS WITH A A FEW PERCENT OF NEODYMIUM

Citation
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
Citations number
30
Categorie Soggetti
Physics, Condensed Matter
ISSN journal
01631829
Volume
52
Issue
13
Year of publication
1995
Pages
9427 - 9436
Database
ISI
SICI code
0163-1829(1995)52:13<9427:MPAHFO>2.0.ZU;2-L
Abstract
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.