Induced Magnetic Anisotropy and Magnetic Properties of Nanocrystalline Fe-Cu-Nb-Si-B Alloys

The induced magnetic anisotropy and magnetic properties of nanocrystalline Fe-Cu-Nb-Si-B alloys were investigated by changing the field annealing condition. The induced anisotropy increased with the field annealing time. A high relative initial permeability μr, a flat B-H loop. and low remanence were obtained by transverse field annealing for a short time. The maximum value of the relative initial permeability, over 130,000, occurred not at zero anisotropy but at a low value, Ku=2.5 J/m3, of the transverse anisotropy. Nanocrystalline Fe-Cu-Nb-Si-B alloys are used in several applications such as choke coils for noise filters, pulse transformers, and current transformers. We found a proportionality between the μr-1 value and the induced anisotropy Ku. However, the proportionality factor depended on the direction of Ku. The above types of behavior are similar to those of Co-based amorphous alloys.