Abstract This paper reports on the magnetic data of Fe 100− x Si x (15< x<34) alloys obtained by rapid quenching from the melt, complementing the data in the literature existing for low silicon content ( x<25). The X-ray diffraction experiments shows that the basically cubic structure change from DO3 structures below 28 at.% Si to B2 structure around x=33. The thermomagnetic curves show a single ferro-paramagnetic transition on heating in the whole concentration range. Our saturation magnetization and Curie temperature data for high Si contents represent an extension of low Si content data up to 34 at.% where we could successfully prepare these alloys with cubic structure. The spin wave stiffness versus Curie temperature relation is approximately linear up to x=37.5 at.% Si. The soft magnetic metastable, nanocrystalline Fe 67Si 33 ribbon with M s =0.6 T and a large resistivity of 200 μΩ cm is a hopeful candidate for powder core applications at high frequencies.