Perpendicular Magnetic Anisotropy and Magnetostriction of Evaporated Co-(Pr,Nd,Gd,Dy,Er) Amorphous Binary Alloy Films

Co-(Pr, Nd, Gd, Dy, Er) amorphous binary alloy films were fabricated by vacuum evaporation, and the perpendicular magnetic anisotropy constant K_⊥ and magnetostriction A 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 K_⊥^max (77 K) as the RE element was varied, was found to be similar to that of the uniaxial anisotropy expected from ions of the different rare earths in a Gd-based crystal. This fact suggests that the mechanism of perpendicular magnetic anisotropy in these amorphous films can be satisfactorily explained by a model of single RE ions in crystals, together with the local atomic order of RE atoms.