Composition dependence of field induced anisotropy in ferromagnetic (Co,Fe)_(89)Zr_7B_4 and (Co,Fe)_(88)Zr_7B_4Cu_1 amorphous and nanocrystalline ribbons

摘要

The composition dependence of field induced anisotropy K_U of field annealed soft ferromagnetic (Co_(1-x)Fe_x)_(89)Zr_7B_4 and (Co_(1-x)Fe_x)_(88)Zr_7B_4Cu_1 amorphous and amorphousanocrystalline "nanocomposite" melt spun ribbons is investigated. With the exception of the highest Co-containing alloys (x< ～0.10), the observations are discussed in terms of a superposition of directional pair ordering of Fe,Co atoms and an additional contribution presumably due to the presence of Zr and B in both the field crystallized and field annealed amorphous ribbons. The highest Co-containing alloys (x< ～0.10) contain multiple nanocrystalline phases (bcc, fee, and hep) for which a peak in K_U is observed (K_U～2000-2500 J/m~3). In this framework, asymmetry in the compositional dependence of K_U resulting in larger values for Co-rich alloys relative to Fe-rich alloys for both the field crystallized and field annealed amorphous alloys is explained in terms of a strong dependence of the Curie temperature of the amorphous phase on the Co content.