Soft Magnetic Properties of Carbide-Dispersed Nanocrystalline Fe-Si-Hf-C Films

The structural and soft magnetic properties of (Fe1-xSix)-Hf-C films (0¿x¿0.27) crystallized from the amorphous state were investigated as functions of the Si concentration. The samples crystallized with a nanocrystalline microstructure including dispersed ultrafine HfC particles. Most of the Si in the films was dissolved in bec Fe after crystallization. By increasing the Si concentration to x=0.13, the upper limit to the thermal stability of the soft magnetic properties becomes 50K higher than that of Fe-Hf-C films. Moreover, the high-frequency permeability is improved owing to a four to five-fold increase in electrical resistivity. A sufficiently high saturation magnetization of 1.3 T was obtained even for x=0.13. For films with x larger than 0.15, good soft magnetic properties could not be obtained, probably because of the stress-induced anisotropy and the coexistence of an amorphous phase with a low Curie temperature.