Effect of Ge on soft magnetic properties at elevated temperature for Si-rich Finemet-type alloy

Abstract

• The effect of Ge doping on the soft magnetic properties is investigated for Si-rich Finement-type alloy. • The Curie temperature is enhanced by doping Ge in Si-rich Finemet-type alloy. • The initial permeability μ i of 540°C-annealed Fe 72 Ge 2.5 Cu 1 Nb 3 Si 17.5 B 5 alloy possesses a relatively large value of 5000 until 600°C. The results obtained by partially substituting Ge for Fe in the Fe-based nanocrystalline alloy for improving the magnetic properties at high temperatures are presented in this work. These studies were performed on the Fe 74.5- x Ge x Cu 1 Nb 2 Si 17.5 B 5 ( x =2.5, 5, 7.5) alloys. The nanocrystallization and the Curie temperature are dependent on the Ge concentration. The onset temperature of primary crystallization decreases with the increase of Ge, indicating that the dual-phase nanocrystalline structure could be formed at a relatively lower temperature compared with the Ge-free alloy . For the alloy with x =2.5at%, the Curie temperature of the amorphous alloy is enhanced to 405°C. The initial permeability μ i of 540°C-annealed alloy possesses a relatively large value of 5000 until 600°C. Such a magnetic softness at elevated temperature is superior to that of Finemet-type Fe-based nanocrystalline alloys ever reported.