Improvement of soft magnetic properties of nanocrystalline Fe-M-B (M=Zr and Nb) alloys and their applications

With the aim of developing good soft magnetic materials, we examined the magnetic properties of nanocrystalline Fe-M-B alloys containing various additional elements. The nanoscale bcc Fe-Zr-Nb-B-Cu alloys exhibited excellent soft magnetic characteristics of 1.5 to 1.6 T for saturation magnetization (B_z), 1 to 2 A/m for coercive force (H_c), 10×10⁴ to 12×10⁴ for permeability (μ_e) at 1 kHz and nearly zero saturated magnetostriction (λ₅) which had not been achieved for soft magnetic materials reported up to date. The excellent soft magnetic characteristics have already enabled the practical use as pulse transformers for portable telephones which require high μ_e above 10⁵ at 1 kHz and high B_z above 1.5 T. The application fields are hereafter expected to increase significantly because of the excellent soft magnetic properties which have been obtained only for the present materials.