Soft Magnetic Properties and Corrosion Resistance of Nanocrystalline Fe-Al-Ta-C Films

The effect of addition of Al to sputtered nanocrystalline Fe-Ta-C films on the film structure, soft magnetic properties and corrosion resistance were investigated. Films were crystallized from an amorphous state to a nanocrystalline state in which ultra-fine TaC particles were dispersed. Most of the Al in the films was dissolved in ¿-Fe after crystallization. When the Al concentration was increased, the high-frequency permeability improved owing to the increase in electrical resistivity. The thermal stability of the soft magnetic properties was also improved over that of Fe-Ta-C films, and the film corrosion resistance improved sufficiently, probably because of the Al dissolved in ¿-Fe. An Fe66.6Al10.6Ta10.5C12.3 nanocrystalline film after annealing at 823K exhibited a high saturation point of 1.25 T, a high permeability of 3200 at 1 MHz, a high electrical resistivity of 1.32 ¿¿-m, and excellent corrosion resistance and noble pitting potential.