Hard magnetic properties of Fe-Co-Nd-Dy-B nanocrystalline alloys containing residual amorphous phase

Citation
W. Zhang et al., Hard magnetic properties of Fe-Co-Nd-Dy-B nanocrystalline alloys containing residual amorphous phase, J APPL PHYS, 89(1), 2001, pp. 492-495
Citations number
12
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
JOURNAL OF APPLIED PHYSICS
ISSN journal
0021-8979 → ACNP
Volume
89
Issue
1
Year of publication
2001
Pages
492 - 495
Database
ISI
SICI code
0021-8979(20010101)89:1<492:HMPOFN>2.0.ZU;2-P
Abstract
The glass transition and supercooled liquid region were observed in the com position range of 4 to 56 %Co, 2 to 4 %Nd, and 18 to 30 at%B in melt-spun F e-Co-Nd-0.5 at%Dy-B amorphous alloys. The largest value of the supercooled liquid region defined by the difference between the glass transition temper ature (T-g) and the crystallization temperature (T-x), DeltaT(x)(= T-x-T-g) , was 47 K for Fe67Co9.5Nd3Dy0.5B20 and the T-g and T-x are 798 and 845 K, respectively. The crystallized structure consists of Fe3B, Nd2Fe14B, alpha -Fe, and remaining amorphous phases in the annealing temperature up to abou t 903 K for 420 s and changes to Fe3B, Nd2Fe14B, and alpha -Fe phases in th e higher temperature range. The grain sizes after annealing at 903 K are ab out 20 nm for Fe3B, 10 nm for Nd2Fe14B, 30 nm for alpha -Fe, and 5 nm for t he remaining amorphous phase. The interparticle spacing of the Nd2Fe14B pha se is less than 40 nm. The maximum energy product (BH)(max) was obtained fo r the alloy containing the residual amorphous phase subjected to annealing for 420 s at 903 K. The magnetization at a field of 1256 kA/m, remanence, i ntrinsic coercive force, and (BH)(max) are 1.60 T, 1.36 T, 227 kA/m, and 11 0 kJ/m(3), respectively. The hard magnetic properties are interpreted to re sult from the exchange magnetic coupling among Nd2Fe14B, Fe3B, alpha -Fe, a nd remaining amorphous phases with ferromagnetism at room temperature. The formation of the finely mixed structure caused by the residual amorphous ph ase is concluded to result in the good hard magnetic properties with (BH)(m ax) above 100 kJ/m(3) for the B-rich-type Fe-Co-Nd-Dy-B alloy. (C) 2001 Ame rican Institute of Physics.