Interaction domains in isotropic, fine-grained Sm/sub 2/Fe/sub 17/N/sub 3/ permanent magnets

The magnetization process in fine grained Sm/sub 2/Fe/sub 17/N/sub 3/ permanent magnets were studied with high resolution Kerr microscopy and measurements of the magnetization curves. Different susceptibilities after thermal and DC-demagnetization were observed for HDDR processed samples but not for long milled material. The differences for the HDDR material are interpreted considering cooperative magnetization phenomena ('interaction domains') that produce changes in the degree of frustration between the magnetization directions of neighbouring grains.