Structure and hyperfine interactions in Al-doped FINEMET

Mössbauer spectrometry, TEM and VSM were used to investigate microstructure and properties of amorphous and nanocrystalline Fe73.5−xAlxNb3Cu1Si13.5B9 (0⩽x⩽7) alloys. It was found that aluminum substitution caused changes in many characteristics: Curie temperature of the crystalline phase as well as of the amorphous one, magnetization, mean magnetic moment, mean hyperfine field, isomer shift and crystallization temperature. Character of the reported changes points to heterogeneity of as-quenched alloys and also of crystalline grains in the annealed samples, particularly for higher Al concentration. This is confirmed by Mössbauer temperature measurements performed for the nanocrystalline alloy with maximal Al content. At x=5 the ordering into DO3 structure is observed.