Phase distribution, grain size and coercivity in nanocomposite permanent materials

Abstract Phase distribution and grain size are the key factors controlling the coercivity in nanocomposite permanent magnets. Assuming three simple physical models with different phase distributions, we have calculated the dependence of coercivity on the grain size and volume fraction of hard phase by using the statistical mean. The calculations show that the different phase distributions leads to the variation of the dependence of coercivity on the grain size and volume fraction of hard phase. High coercivity can be probably obtained by designing an ideal phase distribution with the clusters of soft grains and controlling the hard grain size. Besides, the calculated results also indicate that the experimental enhancement of the coercivity with reducing hard grain size depends on the effects of the grain size and phase distribution on the fraction of soft–hard grain interface.