Nanocrystalline Soft Magnetic Fe-M-B (M = Zr, Hf, Nb) “NANOPERM,” Fe-M-O (M = Zr, Hf, Rare Earth) Alloys and Their Applications

ABSTRACTNew soft magnetic nanocrystalline materials in Fe-M-B (M = Zr, Hf, Nb) and Fe-M-O (M = Zr, Hf, rare earth) systems have been fabricated by use of partial crystallization of melt-spun amorphous phase and sputtering-induced partial crystallization, respectively. These alloys have a mixed structure of nanoscale a-Fe grains and an amorphous phase containing large amount of M, B and M, O, respectively. This structural property should be a dominant factor for achieving good soft magnetic properties in both alloys. The Fe85.5Zr2Nb4B8.5 ribbon exhibits a high mag- netic flux density (Bs) of 1.64 T and a high permeability of 60,000 at 1 kHz as well as a very low core loss of 0.09 W/kg at B = 1.4 T and 50 Hz. The soft magnetic Fe-M-O films with high O content of 10-35 at.% maintain high permeability up to the high frequency above 100 MHz be- cause of higher electrical resistively of 6 to 23 µΩm than those of other conventional soft mag- netic alloy films. The Fe-M-B ribbons "NANOPERM" should be more suitable for low frequen- cy transformers. The Fe-M-O films are useful for high frequency applications such as thin-film inductors and transformers for micro switching converters for portable electric equipment.