Experimental evidence is presented to support the idea that the boron content, which influences the Fe-Fe pair distances and the electronic structure, determines the magnetic properties of amorphous Fe-Si-B alloys. Magnetic moment variations are ascribed to the local environment of the iron atoms and to the electronic structure of the amorphous Fe-Si-B alloys while the T-c changes are due to the increase of the Fe-Fe pair distances. The mean atomic magnetic moments per iron atoms were extrapolated at 0 K. Radial Distribution Analysis combined with Rietveld refinement achieved an estimation of Fe-Fe distances in amorphous and partially crystallized specimens, while the peculiarities in crystallization were revealed by HRTEM. (C) 2003 Elsevier Ltd. All rights reserved.