Approaching the theoretical coercivity of Nd{sub 2}Fe{sub 14}B: Microstructural evaluation and interparticle interactions

Journal Article · Wed Nov 01 04:00:00 EST 2000 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.1313782· OSTI ID:40204953

Girt, Er; Krishnan, Kannan M; Thomas, G; Altounian, Z; Dikeakos, M

The microstructure of melt--spun rapidly quenched Nd{sub {delta}}Fe{sub 13.1}B (2.05{<=}{delta}{<=}147.6) and Nd{sub {delta}}Fe{sub 14}B ({delta}=40.6,151.7) ribbons was tailored by appropriate annealing from strongly interacting to magnetically isolated single domain Nd{sub 2}Fe{sub 14}B grains embedded in a nonmagnetic matrix of {alpha}-Nd and {gamma}-Nd. This microstructure, as characterized by a variation in the magnetic interaction between Nd{sub 2}Fe{sub 14}B grains, was found to have a large impact on coercivity, {mu}{sub 0}H{sub c}, i.e., coercivity increases with an increase in the Nd concentration from 1.2 T in Nd{sub 2.05}Fe{sub 13.1}B to 2.75 T in Nd{sub 147.6}Fe{sub 13.1}B at 290 K. A detailed study of the microstructure of Nd{sub {delta}}Fe{sub 13.1}B ({delta}=38.1,148.7), carried out by conventional transmission electron microscopy, energy-filtered imaging, and energy dispersive x-ray microanalysis, showed that the majority of the Nd{sub 2}Fe{sub 14}B grains are completely isolated only in Nd{sub 147.6}Fe{sub 13.1}B. The Nd{sub 2}Fe{sub 14}B grains, in Nd{sub 147.6}Fe{sub 13.1}B, are found to be randomly oriented platelets with the c axis normal to the platelet and an average size of 100x40x25 nm. For these randomly oriented, noninteracting, single domain Nd{sub 2}Fe{sub 14}B grains, the coercivity was calculated using the Stoner--Wohlfarth model and including the shape anisotropy of the grains. The observed coercivity of Nd{sub 2}Fe{sub 14}B in Nd{sub 147.6}Fe{sub 13.1}B is {approx}83% of this theoretical value and is the largest so far reported for Nd{sub 2}Fe{sub 14}B.

• Sponsoring Organization: (US)
• OSTI ID: 40204953
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 9 Vol. 88; ISSN 0021-8979
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
ANNEALING
EVALUATION
MICROANALYSIS
MICROSTRUCTURE
PHYSICS
SHAPE
TRANSMISSION ELECTRON MICROSCOPY