Induced anisotropy in nanocrystalline FeCuNbSiB

The kinetics of induced anisotropy K/sub ind/ was studied in nanocrystalline Fe/sub 73.5/Cu/sub 1/Nb/sub 3/Si/sub 13.5/B/sub 9/, as well as in the amorphous precursor and in amorphous Fe/sub 78/B/sub 13/Si/sub 9/. The nanocrystalline alloy was produced from the precursor by annealing at 813 K for 1 h and possessed an average FeSi grain size of 13 nm, as determined from X-ray diffraction. Annealing in a 0.2 T field at 723-773 K, above T/sub c/ of the amorphous phase, resulted in low values of K/sub ind/. The data were compared to the micromagnetic theory of Kronmuller to determine activation energy spectra. K/sub ind/ for the nanocrystalline alloy is well described by this theory, however, with an activation energy spectrum that is much narrower than for the amorphous alloys. The limiting value of the anisotropy is K/sub /spl infin///spl ap/13 J/m/sup 3/ consistent with that expected for the anisotropy in Fe-20at%.Si with the DO/sub 3/ structure.<
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