LAUSR

Abstract Nanocrystalline soft magnetic materials are widely used in power electronic applications due to their high permeability, magnetization and low core loss. In this paper, Fe 73.5 Cu 1 Nb 3 Si 15.5 B 7 (at%) nanocrystalline alloy ribbons, with ultra-thin thickness of 14 µm, and also 18 and 22 µm, were prepared by a planar flow casting method with a single roller device. Soft magnetic properties of these ribbons were analyzed after nanocrystallization annealing. The experiments were conducted on toroidal samples using IWATSU B-H Analyzer over a frequency range of 10–100 kHz, at induction amplitudes of 100–500 mT, at room temperature. It was found that the excess eddy current loss P ex was the dominant factor in the overall core loss above 10 kHz. The toroidal samples made of the 14 µm thickness ribbon exhibit very low total core loss of 48 W/kg at a frequency of 100 kHz and magnetic flux density of 300  mT. The ratio of the P ex was up to 89% at 100 kHz. The ribbon with lower thickness exhibits lower P ex and therefore lower total core loss. The domain structure evidences were found. It indicates that the ribbons with small thickness are preferable for application in high frequency condition.