7.5 Conclusions

In order to improve the magnetic properties of pinning controlled Sm(Co,Fe,Cu,Zr)$_z$ magnets the thickness and the composition of the cell boundary phase have to be optimized. As the difference in the domain wall energy between the cells and the cell boundary phase increases, the pinning field and, as a result, the coercive field of the magnet increase in the regime of attractive as well as in that of repulsive pinning. Our detailed study of the pinning behavior of domain walls has revealed, that the dependence of the pinning field on the thickness of the intercellular phase is equivalent for attractive and repulsive domain wall pinning. However, our simulations show, that the cellular structure of Sm(Co,Fe,Cu,Zr)$_z$ magnets plays a crucial role for domain wall pinning. The cell boundary phase must not be too thin, for the domain wall to ``fit in'' and it must not be thicker than 4 times the domain wall width. Within this range the thickness of the cell boundary phase reduces the pinning field linearly with increasing relative thickness of the intercellular phase.