Effects of heat treatment in air on soft magnetic properties of FeCoSiBPC amorphous core

The oxidation behavior and soft magnetic properties of industrially prepared Fe80Co3Si3B10P1C3 amorphous cores were investigated under heat treatment in air. Results indicate that the FeCoSiBPC amorphous core heat-treated in air can obtain higher permeability (μi) and maximum saturation magnetic induction (Bm) than that annealed in vacuum. The improvement of soft magnetic properties originates from the formation of a Co-rich layer between the oxide layer and the amorphous substrate after the selective oxidation of Fe. The core loss (Pcm) of the amorphous cores decreases after annealing at 280 ℃ in air for 30 min, and increases with the annealing time extend to 60 min. The Pcm of the samples treated in air is inferior to that of the ones annealed in vacuum for 30 min. The variation of Pcm can be explained by the thinning of the amorphous substrate based on the Gyorgy's model and simple models of domain wall pinning.