Coercivity of sintered Nd(Fe0.92−xGaxB0.08)5.5 permanent magnets

The temperature dependence of the coercive field of Nd(Fe0.92−xGaxB0.08)5.5 compounds with x=0 and 0.01 has been measured from 10 K up to the Curie temperatures in fields applied parallel or perpendicular to the magnetic alignment direction and has been analyzed in terms of a micromagnetic model. Two temperature ranges in which different mechanisms control the coercivity can clearly be distinguished. At temperatures above 170 K, a nucleation process of reversed domains determines the coercivity mechanism. From the micromagnetism point of view, partial substitution of Fe by Ga into NdFeB magnets leads to a reduction of the local effective demagnetization field (−NeffMs) which makes the nucleation of reversed domains more difficult, and therefore enhances the coercivity.