The effects of grain condition on magnetic properties in Nd4Fe76Co3(Hf1−xGax)B16 alloy

Abstract

The best linear fit of Hc(T)/Ms(T) versus implies that Hc is determined by a nucleation process in nanocrystalline two-phase magnets. The condition of the grain shapes is improved after adding Hf and Ga, but the surfaces are deteriorated by some precipitates on the boundary. Taking into account the values of α, Neff, the results of transmission electron microscopy (TEM), and Mössbauer spectroscopy, the magnetic field heat treatment not only induces grain refinement but also causes a uniform distribution of the soft and hard phases. Both the remanence and energy product values are increased by 20–30% for all ribbons after annealing with magnetic field. The magnetic interaction in Nd2Fe14B/Fe3B + αFe-based nanocrystalline two-phase magnets is studied using δM plots in this paper. It is found that the exchange-coupled interaction is greatly enhanced in the sample annealed with magnetic heat treatment, especially Nd4Fe76Co3Hf0.5Ga0.5B16, which achieves the highest energy product (BH)max = 15.8 MGOe.