Sendust ribbons, about 20μm thick, 5.5∼6.5 mm wide and several meters long are made by a rapid quenching method. Ribbons obtained are so mechanically flexible that it is possible to wind them easily around a lod of 10 mm in diameter. The DC hysteresis loss changes with a flux density approximately as (B)
1.8. The iron loss increases with frequency as

and with flux density as (B)
1.9. The eddy current loss increases with frequency as

and with flux density as

. The iron loss is lower than 19 × 10
5W/m
3in the composition range around 9.5% Si and 5.6∼6.2% Al at the frequency of 100 kHz and at the flux density of 400 mT.