INDUCED ANISOTROPY IN NANOCRYSTALLINE FECUNBSIB

The kinetics of induced anisotropy K-ind was studied in nanocrystalline Fe73.5Cu1Nb3Si13.5B9, as well as in the amorphous precursor and in amorphous Fe78B13Si9. 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-c of the amorphous phase, resulted 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, with an activation energy spectrum that is much narrower than for the amorphous alloys. The limiting value of the anisotropy is K-infinity approximate to 13 J/m(3) consistent with that expected for the anisotropy in Fe-20at%.Si with the DO3 structure.