Magnetostriction of transition-metal-metalloid glasses: Temperature dependence

Linear, saturation magnetostrictions λₛ of a variety of (FeCoNi)₈₀{B}₂₀$ glasses have been studied as a function of temperature. Magnetostrictions over the range $4.2 K{}T{}{T}C$ for selected glasses, ${Fe}₈₀B₂₀, Co₄₀{Ni}₄₀B₂₀, and Ni₅₀{Fe}₃₀B₂₀, are shown to follow reasonably well the theory of Callen and Callen for single-ion anisotropy of uniaxial-strain symmetry, i.e., λₛ(T)λₛ(0)=^I5/2(X)≡I5/2(X)I1/2(X) with I3/2(X)≡m(T), the reduced magnetization. The anomalous temperature dependence of the magnetostriction observed in the cobalt-rich (FeCo)₈₀{B}₂₀$ glasses is attributed to the combination of a positive two-ion (anisotropic-exchange) term plus a stronger, negative, one-ion (crystal-field) term. A change of sign in ${{λ}}ₛ$ occurs along the Co-Ni side of the triangular Fe-Co-Ni(${B}₂₀$) diagram due to a change in sign of the dominant single-ion mechanism. This sign change results from a change in the orbital character of the states at the Fermi energy as it passes from the top of the cobalt or nickel 3d^↓ band to the bottom of the iron 3d^↓ band.