Structural and mossbauer effect investigations of amorphous FeCuNbSiB alloys nanocrystallized (VITROPERM) in magnetic field

Abstract

Melt-spun amorphous ribbons of nominal composition Fe₇₃Cu₁Nb₃Si₁₆B₇, annealed at 560-580 °C for 1 hour in a magnetic field (H) applied along the width in the ribbon plane, develop uniaxial magnetic anisotropy with easy axis along H and exhibit several novel attributes. The samples labelled as S₂₀ and S₁₅₀ are nanocomposites consisting of ferromagnetic nanocrystalline grains (volume fraction ≈ 84% and 81%) of mean size d = 13(2) nm embedded in a ferromagnetic amorphous matrix and possess a magnetic permeability as large as 20,000 and 150,000, respectively. While nearly 55% of the nanocrystalline grains have a cubic DO₃Fe₃Si-like structure with actual Si concentration of about 22 at.%, the remaining 45% nanocrystalline grains have tetragonal Fe₃B and hexagonal Fe₂Si structure. Since the crystalline volume fraction of Fe₃B and Fe₂Si nanocrystals is more in the sample S₂₀, this sample exhibits stronger local magnetic anisotropy and hence lower permeability.