Effect of cooling rate on dynamic magnetization of Fe86Zr7B6Cu nanocrystalline alloy

The complex permeability spectra in Fe86Zr7B6Cu nanocrystalline alloy are studied by varying ac field amplitude and the cooling rate after annealing. It is shown that the initial permeability and the relaxation frequency strongly depend on the extent of domain wall pining. Slow cooling may result in the nucleation of the short-range atomic ordering in domain walls, whereas fast cooling may induce internal stress. Both the too slow cooling and the too fast cooling would make the additional pinning sites form in domain walls, which may strengthen the domain wall pining and make the permeability decrease and the relaxation frequency increase. The control of cooling rate is one of most important factors to improve the soft magnetic properties of Fe86Zr7B6Cu nanocrystalline alloy.