Magnetic Properties of Nanocrystalline Materials

This chapter discusses the magnetic properties of nanocrystalline materials. The development of new soft magnetic materials with excellent characteristics of high magnetic flux density (B_s)of more than 1.5T combined with high ?e of more than 10⁵ at 1kHz was achieved by nanocrystallization of Fe-Zr-Nb-B-Cu amorphous alloys. The Cu-free quaternary Fe_85.5Zr₂Nb₄B_8.5 alloy which exhibits high Bs of 1.64T and high ?e of 6.0 × 104 at 1kHz simultaneously, was also developed. In addition, it was found that the simultaneous addition of 1 at% P and 0.1 at% Cu to the Nb-poor Fe₈₅Nb₆B₉ alloy results in good magnetic properties of high B_s of more than 1.6T and high ?e of more than 4 × 10⁴ at 1 kHz as well as good productivity. Furthermore, the dissolution of oxygen in the remaining amorphous phase caused significant improvement of high-frequency permeability of 10³ in the frequency range 1 to 100 MHz by a drastic increase in ?_RT to 103??m. Considering that these characteristics had not been previously reported, nanostructure control is concluded to be a useful method for the development of new types of high functional materials. The future progress of nanostructure-controlled materials is expected to enable the fabrication of new materials exhibiting useful characteristics which have not been achieved for conventional materials.