Analysis of the magnetic hardening mechanism in RE-FeB permanent magnets

For the interpretation of extremely high coercive fields of RE-NdB permanent magnets in general either models of pinning or nucleation mechanisms are considered. In both cases the magnetic properties of the phase boundaries between the grains are suggested to be responsible for the actual value of Hc. In this paper a detailed analysis of the temperature dependence of Hc is given on the basis of the predictions of micromagnetic theories for pinning and nucleation mechanisms. It is shown that the nucleation theory leads to a far more coherent interpretation of all relevant properties of Hc than the pinning theory if the effects of misaligned grains, local stray fields and reduced anisotropies in grain boundaries are taken into account.