Effects of orientation and interaction of grains on coercivity for sintered NdFeB magnets |
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Authors: | Ruwei Gao Wei Li Jiancheng Zhang Liangxue Wu and Xiaojun Yu |
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Institution: | (1) Department of Physics, Shandong University, 250100 Jinan, China;(2) Central Iron & Steel Research Institute, 100080 Beijing, China |
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Abstract: | The coercivity of NdFeB magnets is determined by the coercivity of individual grains and the interaction between the grains
composed of the magnets. The coercivity of individual grains and the intergrain interaction depend on the degree of the grain
alignment, “tanθ type” Gaussian function is applied to describing the degree of the grain alignment. According to different
coercivity mechanisms, there are different formula on the coercivity and the angular dependence of coercivity. The interaction
between grains can be classified as the long-range magnetostatic interaction and the exchange-coupling interaction of neighboring
grains. For the sintered magnet, the grain size is large and the grain boundaries are mostly separated by the non-magnetic
phase. So, the long-range magnetostatic interaction is much stronger than the exchange coupling interaction and it makes the
coercivity of the magnet composed of misaligned grains be bigger than that of the magnet composed of ideally aligned grains.
The effects of coercivity of individual grains and the intergrain interactions are taken into account, and the starting field
theory is in agreement with the experimental result for the coercivity of sintered NdFeB magnets.
Project supported by the National Natural Science Foundation of China (Grant No. 59571017). |
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Keywords: | NdFeB sintermagnets grain alignment exchange-coupling interaction long-range magnetostatic interaction coercivity starting field theory |
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