Magnetization processes in nanocrystalline ferromagnets

Abstract We have investigated the grain size dependence of the characteristic magnetic properties as the initial susceptibility, the coercivity and the Rayleigh constant of nanocrystalline Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 . Before there is any significant change in the grain size all the magnetic properties change their values by several orders of magnitude due to a change of the magnetization process. At low annealing temperatures (small grains) we found irreversible domain wall movements which could be well described by the statistical potential theory. After higher annealing temperatures the magnetic properties changed drastically and the magnetization occurs by rotational processes. The strong decrease of the Rayleigh constant and the corresponding change in the magnetization process is attributed to increased pinning of domain walls due to the precipitation of crystalline Fe-B compounds.