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Nd2Fe14B/FeCo Anisotropic Nanocomposite Films with a Large Maximum Energy Product

2012年10月26日(金)

Advanced Materials ( Volume 24, Issue 48, pages 6530–6535, December 18, 2012 )
Wei-Bin Cui ( NIMS )
Yukiko K. Takahashi ( NIMS )
Kazuhiro Hono ( NIMS )

[Publication]
Advanced Materials
Volume 24, Issue 48, pages 6530–6535, December 18, 2012
DOI: 10.1002/adma.201202328

abstract

Nd-Fe-B permanent magnets have recently regained intense research interest due to their broadening applications in the traction motors of hybrid and pure electric vehicles and wind generators.
A large maximum energy product (BH) max can be obtained in anisotropic sintered magnets due to the relatively high saturation magnetization of the Nd2 Fe14 B main phase and its large magnetocrystalline anisotropy energy.
The typical value of the (BH) max of the highest grade commercial Nd-Fe-B sintered magnets is about 400 kJ m−3 with an intrinsic coercivity of μ0 Hc ≈ 1.2 T.
A highest value of 475 kJ m−3 has been reported for a laboratory scale Nd-Fe-B sintered magnet with a small fraction of the secondary Nd-rich phase and a strong (001) texture, which gives rise to a large remanence of μ0 Mr =1.55. [ 1 ]
However, the coercivity is only 0.8 T, which is only marginally higher than the minimal requirement, μ0 Mr /2, to obtain the maximum energy product, m0 Mr2 /4, that is expected for a magnet with an ideally rectangular demagnetization curve.
Although the detailed mechanism is not known, the low coercivity of the high remanence magnet is thought to occur from the avalanche expansion of reversed domains among magnetically coupled highly aligned Nd 2 Fe 14 B grains.


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