Recent developments of new soft magnetic materials

This paper reports three large topics for recent soft magnetic materials: ultrathin grain-oriented silicon steels, nanocrystalline magnetic materials and 6.5 wt% Si-Fe alloy sheets. The ultrathin grain-oriented silicon steels are known to have extremely low iron loss. Recently it has reported the domain width of ultrathin grain-oriented silicon steels can be controlled by changing the grain size, so that very low iron losses can be realized without an additional domain-refining technique. The nanocrystalline magnetic materials are made by recrystallizing amorphous materials. Since the grain size is about 10 nm, the effective magnetic anisotropy is small, so the nanocrystalline materials have fine soft magnetic properties. The 6.5 wt% Si-Fe alloy has small magnetostriction, but has not been manufactured because of its poor ductility. Recently the sheets have been commercially developed and used for high-frequency transformers.