INDUCED ANISOTROPY IN NANOCRYSTALLINE FECUNBSIB

The kinetics of induced anisotropy K-ind was studied in nanocrystallin e Fe73.5Cu1Nb3Si13.5B9, as well as in the amorphous precursor and in a morphous Fe78B13Si9. The nanocrystalline alloy was produced from the p recursor by annealing at 813 K for 1 h and possessed an average FeSi g rain size of 13 nm., as determined from x-ray diffraction. Annealing i n a 0.2 T field at 723-773 K above T-c of the amorphous phase, resulte d in low values of K-ind. The data were compared to the micromagnetic theory of Kronmuller to determine activation energy spectra. K-ind for the nanocrystalline ahoy is well described by this theory, however, w ith an activation energy spectrum that is much narrower than for the a morphous alloys. The limiting value of the anisotropy is K-infinity ap proximate to 13 J/m(3) consistent with that expected for the anisotrop y in Fe-20at%.Si with the DO3 structure.