Nucleation and pinning of magnetic domains at Co7Sm2 precipitates in Co5Sm crystals

By means of the magneto-optical Kerr effect the domain configuration in Co5Sm-crystals is investigated in dependence on the applied magnetic field. The observed change of the domain structure is interpreted in terms of a micromagnetic theory for the magnetization curve of uniaxial single crystals. The displacement of domain walls took place at an initial field of 265 Oe which is interpreted as the intrinsic coercive field due to the Peierls potential and randomly distributed lattice defects. The density of the interaction energy per extension of the wall is determined to be {article}{empty}{document}E₀ √ρ /L = 30\,erg/cm⁴{document} in the case of a rigid wall. The nucleation of reversed domains is observed in the phase boundary between precipitate and matrix. Furthermore precipitates in grain boundaries are found to act as sources of nucleation centres. These results are interpreted by the nucleation of reversed domains in regions of low crystal anisotropy or of irregular precipitate-surface.