Magnetic domains and coercivity in SmCo 2 : 17 type magnets

The coercivity of SmCo 2:17-type magnets is known to be very sensitive to details of the processing procedure. In this study we have found that the same is true with respect to the domain structure of these magnets. Thus in optimally processed high temperature Sm(Co0.784Fe0.1Cu0.088Zr0.028)(7.19) magnets, the typical domain width is less than 1 mu m, but significantly larger than the typical size of 2:17R cells of about 100 nm. On the other hand, quenching straight from the aging temperature of 850 degrees C, i.e. omitting slow cooling, leads to a much coarser domain structure (domain width similar to 10 mu m) and a small coercivity (< 0.1 T). The fine domain structure of the optimally processed bulk magnet can be considered as interaction domains - an alternative phenomenon compared to the zigzag shaped domain walls known for thinned specimen.