Nanoscale structure and magnetic properties of Nd-Fe-Nb-B-C permanent magnets

Author

Chen, X.Y. ; Jiang, Zh L. ; Zhang, L. ; Yang, Ch P. ; Bai, F.M. ; Wang, X.F. ; Chen, H.M. ; Zhu, J.

Author_Institution

Dept. of Mater. Sci. & Eng., Tsinghua Univ., Beijing, China

Volume

39

Issue

5

fYear

2003

Firstpage

2194

Lastpage

2197

Abstract

We investigated the nanoscale structure and magnetic properties of Nd₂(FeNb)₁₄(BC)/α-Fe. We studied several alloy compositions and the effect of C and Nb on the properties, and thus produced a new alloy of Nd₉Fe_85.5Nb_1.0B₄C_0.5. Its mean grain size is about 40 nm. Grain refinement enhanced the remanence, because of greater ferromagnetic exchange coupling between the hard and soft magnetic phase grains. Annealing improved the properties further. By optimizing the processing conditions, we obtained relatively high performance [J_r=1.099 T, H_ci=518.3 kA/m, J_r/J_s=0.82, (BH)_max=137.8 kJ/m³] when the alloy was annealed at 700°C for 15 min. We examined the magnetic domain structure in the nanophase alloy by magnetic force microscopy. The length of the magnetic contrast in the alloy is in the range of 450-550 nm, much bigger than the mean grain size. Here, we interpret the length in terms of interaction domains, which originate from the exchange coupling effect.

Keywords

annealing; boron alloys; coercive force; exchange interactions (electron); ferromagnetic materials; grain refinement; grain size; iron alloys; magnetic domains; magnetic force microscopy; nanostructured materials; neodymium alloys; niobium alloys; permanent magnets; remanence; 15 min; 40 nm; 450 to 550 nm; 700 C; Nd-Fe-Nb-B-C permanent magnets; Nd₂(FeNb)₁₄(BC)/α-Fe; Nd₉Fe_85.5Nb_1.0B₄C_0.5; alloy compositions; annealing; ferromagnetic exchange coupling; grain refinement; hard magnetic phase grains; interaction domains; magnetic contrast length; magnetic domain structure; magnetic force microscopy; magnetic properties; mean grain size; nanophase alloy; nanoscale structure; processing conditions optimization; remanence enhancement; soft magnetic phase grains; Annealing; Grain size; Iron alloys; Magnetic domains; Magnetic properties; Nanostructures; Neodymium; Niobium alloys; Permanent magnets; Soft magnetic materials;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/TMAG.2003.817070

Filename

1233434