The best linear fit of Hc(T)/Ms(T) vs 2k1(T)/μ0M s2(T) infers that Hc is determin ed by a nucleation process in nanocrystalline two-phase magnet. The condition o f the grain shapes is improved after adding Hf and Ga, but the surfa ces are deter iorated by some precipitates on the boundary. Taking into account the values of α, Neff, the results of TEM, and Moessbauer spectroscopy, the mag netic field heat -treatment not only induces grain refinement but also causes a uniform distribu t ion of the soft and hard phases. It is one recommendable method to improve the condition of the microstructure. Both the remanence and energy product values are increased by 20%-30% for all ribbons after annealing with magnetic field. The ma gnetic interaction in Nd2Fe14B/Fe3B+αFe based nanocrystalline tw o-phase magnets is studied using δM plots in this paper. It is found that the exchange coup led interaction is greatly enhanced in the sample annealed with magnetic heat-treat ment, specially, Nd4Fe76Co3Hf0.5Ga0.5B16 which achie ves the highest energy product (BH)max=126.4 kJ/m3.
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