Domain wall pinning versus nucleation of reversed domains in R-Fe-B magnets (invited)

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Abstract
The validity of nucleation and domain wall pinning models has been examined in R‐Fe‐B magnets by correlating the hard magnetic properties with the microstructure and magnetic domain structure. The nucleation model can be used to explain the magnetic properties of R‐Fe‐B magnets at low temperatures, but it fails at high temperatures. On the other hand, domain wall pinning can explain the magnetic properties over a much wider temperature range (up to the Curie temperature). The magnetic and structural data suggest that the coercivities (Hc) of powders and stoichiometric melt‐spun ribbons are due to ‘‘strong pinning’’ by a random distribution of pins while the Hc of sintered magnets and ribbons with off‐stoichiometric composition are due to ‘‘localized pinning’’ at grain boundaries.