The magnetization of Sm-2(Co, Fe, Cu, Zr)(17) is determined by the motion o
f domain boundary walls that are subject to pinning. Measurements have been
made of the relationship between the reversible magnetization M-rev and th
e irreversible magnetization M-irr components in Sm-2(Co, Fe, Cu, Zr)(17).
The results are consistent with a model in which rapid nucleation of domain
walls occurs at the beginning of magnetization reversal followed by gradua
l unpinning of the domain walls. For Sm-2(Co, Fe, Cu, Zr)(17) the parameter
eta, defined as eta=(dM(rev)/dM(irr))(H) is similar in form to previously
observed variations of eta in sintered NdFeB but very different from eta va
riations due to Stoner-Wohlfarth coherent rotation of magnetization vectors
. (C) 1999 American Institute of Physics. [S0021-8979(99)44608-0].