NANOCRYSTALLINE SOFT MAGNETIC-MATERIALS

Nanocrystalline structures offer a new opportunity for tailoring soft magnetic materials. The most prominent examples are devitrified glassy FeCuNbSiB alloys which reveal a homogeneous ultrafine grain structure of bcc FeSi with grain sizes of typically 10-20 nm and random texture. Owing to the small grain size, the local magneto-crystalline anisotropy is randomly averaged out by exchange interaction, so that there is only a small net anisotropy effect on the magnetization process. Moreover the structural phases present lead to low or vanishing saturation magnetostriction. Both the suppressed magneto-crystalline anisotropy and the low magnetostriction provide the basis for the superior soft magnetic properties comparable with those of permalloys or near-zero magnetostrictive cobalt-based amorphous alloys but at a higher saturation induction.