Soft magnetic properties of Fe-B-M-Cu (M=Hf,Zr,Nb) alloys with nanocrystalline and amorphous hybrid structure

The change in magnetic properties with B content and annealing temperature was investigated for Fe-B-M-Cu (M=Hf,Zr,Nb) alloys. In the high B alloys over 8 at% B, the optimum annealing temperatures revealing the excellent soft magnetic properties were below the crystallization temperatures The annealed microstructure had ultrafine BCC-Fe phase grains with a diameter of 5-7 nm and a considerably high fraction (30-50 vol.%) of interfacial amorphous phase. For these alloys, very low core loss and high effective permeability were obtained in the frequency range up to 1 MHz. These behaviors were interpreted to be due their hybrid microstructure and high electrical resistivity.>