Title :
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
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 Nd9Fe85.5Nb1.0B4C0.5. 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 [Jr=1.099 T, Hci=518.3 kA/m, Jr/Js=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; Nd9Fe85.5Nb1.0B4C0.5; 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;
Journal_Title :
Magnetics, IEEE Transactions on
DOI :
10.1109/TMAG.2003.817070
