Domain wall pinning sites in Sm(CoFeCuZr)(x) magnets

The magnetic domain structure of Sm(CoFeCuZr)(x) magnets was studied along various crystallographic zone axes with high resolution Focault mode Lorentz microscopy. The domain wall has been observed to be pinned at (1) 60 degrees hexagonal (H) SmCo5 cell boundaries, (2) features parallel to RSm2Co17 c-axis, (3) features parallel to the RSm2Co17 basal plane, and (4) linear features with no specific crystallographic direction. The wall pinning features which are parallel to the c-axis were determined to be RSm2Co17 antiphase boundaries (APE) and possibly vertical section of HSmCo5 cell boundaries. Both these microstructure features were found to have a higher Cu content than the RSm2Co1 matrix. This chemical inhomogeneity leads to local variations in magnetocrystalline anisotropy which assists domain wall pinning, similar to the role of HSmCo5 suggested previously. Since not all the domain wall pinning features observed are in a strained state, this suggested that chemical segregation to nanostructural features such as HSmCo( )cell boundaries and APE play a more important role than coherency strain in determining H-ci.