Magnetic and Surface Properties of High-Induction Nanocrystalline Fe-Nb-Cu-B/P-Si Ribbons

High-induction Si-poor Fe-Nb-Cu-B-Si Finemet ribbons annealed in inert gas ambience are known to build oxides and prefer surface crystallization. Phosphorus-3 at% of P instead of B was substituted to see how it can influence these surface effects. The off-axis magnetic anisotropy caused by surfaces squeezing the ribbon interior was reduced and it was found out that the major source of the squeeze is the surface crystallization and not the oxides. Phosphorus appears to hamper preferentially the surface crystallization. The substitution also improves the magnetic softness of vacuum-annealed ribbons by grain size reduction. Slight reduction of saturation induction is a minor sacrifice to the improvements.