Upper Limit for the Coercive Force in NdFeB and PrFeB Magnets

Abstract:

Hysteresis loops were calculated according the Stoner-Wohlfarth model. Using as values for constants of magnetocrystalline anisotropy K₁ =4.5 and K₂=0.66 (J m⁻³), and 1.61 T for magnetization of saturation of Nd₂Fe₁₄B, the maximum coercivity for isotropic Nd₂Fe₁₄B was predicted as mi0 H = 2.95 T (29.5kOe). For a very well aligned magnet, with M_r/M_s=0.96, following the f (alpha)=cosⁿ(alpha) distribution, the theoretical coercivity limit was estimated as mi0 H = 3.6 T (36 kOe). These estimates are valid for the ternary Nd₂Fe₁₄B alloy. It is predicted the upper limit for the coercive field as function of grain size for NdFeB and PrFeB magnets. Addition of Praseodymium is an effective method for increasing coercivity of NdFeB magnets.

• Periodical: Materials Science Forum (Volume 802)
• Pages: 596-600
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.802.596
• Online since: December 2014
• Authors: Marcos Flavio de Campos, Fernanda A.S. da Silva, José A. de Castro
• Keywords: Coercivity, Grain Size, Hysteresis, Magnets, NdFeB

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