Structure and temperature dependence of magnetic properties in the nanocrystalline Fe74SixB22-xCu1Nb3 alloys

We have examined the structure and magnetic properties in terms of the temperature dependence of magnetic permeability and magnetization for the Fe74SixB22-xCu1Nb3 (x=8-18) alloys. The temperature dependence of the permeability of the alloys shows various characteristic behaviors depending on the alloy composition (x=8-18) and annealing temperature (450-630 degrees C). The permeability of the samples having coexisting alpha-Fe(Si) and amorphous phases decreases abruptly near the Curie temperature of the amorphous materials, while the permeability of the samples containing precipitated Fe-B compounds is not appreciably affected by the magnetism in the residual amorphous region. The precipitation of Fe-B compound depends on the composition of the mother alloys. The Fe-B compounds precipitated in the amorphous region upon annealing at high temperature are mainly Fe23B6 for x = 14, Fe3B for x = 18, and Fe2B for the composition x less than 12.