Co-(Pr,Nd,Gd,Dy,Er) amorphous binary alloy films were fabricated by vacuum evaporation, and the perpendicular magnetic anisotropy constant K⊥ and magnetostriction λ were systematically examined. For Dy-Co alloy films the maximum value of K⊥ at 77 K, 9 × 106 erg/cm3, was obtained at 25 at% Dy. For Gd-Co films, K⊥ remained close to zero, regardless of the Gd concentration. In Er-Co films, K⊥ at 77 K took on a minimum of -2.5 × 106 erg/cm3 around 19 at% Er. The λ of Gd-Co films decreased monotonically from 60 × 10-6 at 17.1 at% Gd to 15 × 10-6 at 55.1 at% Gd. For Dy-Co films, the maximum value of λ was about 220 × 10-6 at 31.5 at% Dy. In Er-Co films, the sign of λ changed around 17 at% Er. The change in the maximum value of K⊥ (77 K) as the rare-earth (RE) element was varied was similar to the expected change of uniaxial anisotropy due to different rare-earth ions in a Gd-based crystal. This suggests that the mechanism of perpendicular magnetic anisotropy in these amorphous films can be satisfactorily explained by a single-RE-ion model and the local atomic order of the RE atoms.
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