The coercivity mechanism of the precipitation-hardened magnets at different temperature have been investigated by micromagnetic calculations. It was found that the coercivity mechanism varies with the temperature. The magnetization reversal is mainly controlled by domain-wall pinning when the temperature is lower than 800 K, while it is dominated by coherent rotation at higher temperature. The quantitative analysis shows that the reduced coercivity is linearly related to the difference of domain-wall energy between 1:5 and 2:17 phases at , while it is mainly determined by the ratio of exchange constant between the two phases at . The temperature dependence of coercivity is the competitive result of the microstructure parameter and the anisotropy field. The anomalous near the Curie temperature of 1:5 phase is caused by the fast drop of intergrain exchange coupling and thus the fast increase of . The micromagnetic calculations show that the anomalous also can be obtained in the nanocomposite-type with an appropriate microstructure.
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