Time‐temperature‐transformation study of a nanocrystalline Fe91Zr7B2 soft magnetic alloy

The structure, soft magnetic properties, magnetostriction, grain size and volume fraction of the residual amorphous phase have been studied for an amorphous Fe91Zr7B2 alloy annealed for periods of 60 s–1080 ks, at temperatures of 823–973 K. The highest permeability (at 1 kHz and 0.4 A/m) 31,000 and smallest coercivity 4.2 A/m are obtained for the sample annealed at 923 K for 60 s, where a small grain size (≊12 nm) and about 35% of the residual amorphous phase are measured. The coercivity of the nanocrystalline alloy varies as the 3rd power of the grain size, corresponding to the case where the magnetically coupled region has a dimensionality between two and three. This slightly low dimensionality is presumed to be due to the alignment of the magnetization in the sample plane.