IOP Publishing, Journal of Physics: Condensed Matter, 29(18), p. 6607-6620, 2006
DOI: 10.1088/0953-8984/18/29/004
Full text: Unavailable
Amorphous FeCuNbSiB alloys with composition near Fe 73.5 Cu 1 Nb 3 Si 13.5 B 9 (the well-studied FINEMET alloy) were annealed at 520 °C for different durations of time, t A , varying from 3 to 20 min. Detailed investigation of the structure and composition of crystalline phases formed during the initial stages of crystallization in these alloys using techniques such as x-ray diffraction, Mossbauer spectroscopy, scanning electron microscopy, atomic force microscopy and energy dispersive absorption of x-rays, revealed the following. New crystalline phases, tetragonal Fe 3 B and hexagonal Fe 2 Si, not reported previously, exist in all the nanocrystalline alloys in question in contrast to the well-documented cubic Fe-Si phase with the DO 3 structure which coexists with the Fe 3 B and Fe 2 Si phases in some compositions only. The crystallization of Fe 3 B and Fe 2 Si nanocrystalline grains starts at the surface of the ribbons and then proceeds to the bulk whereas the crystallization of DO 3 Fe-Si gets initiated within the bulk. The average size of the nanocrystalline grains of the Fe 3 B and Fe 2 Si and cubic DO 3 Fe-Si structures in the residual amorphous matrix is around 20 nm but their volume fractions are as low as ≈ 5%, 10%, and 7%, respectively. The cubic Fe-Si nanocrystals of the DO 3 structure have a silicon concentration in the range 15-20 at.%. The magnetic moments in the amorphous precursor point, on average, are 40° out of the ribbon plane while in the nanocrystalline alloys this angle varies between 2° and 19° depending on the Fe concentration.