Elasticity and magnetoelasticity of Fe–Ga solid solutions

Abstract

Continuous-wave measurements of the shear elastic constants of bcc Fe–Ga solid solutions show that the constant $C_{44}$ is independent of the gallium composition while the constant $\frac{1}{2}{\mathrm{(C}}_{11}{\mathrm{–C}}_{12})$ decreases linearly and extrapolates to zero at 26 at. % Ga. This result indicates that the Fe–Ga solid solution is inhomogeneous and contains clusters consisting of embryos of a martensitic phase. The increasing softness of $\frac{1}{2}{\mathrm{(C}}_{11}{\mathrm{–C}}_{12})$ then reflects an increase of the embryo density. A model assuming that the clusters are centered around next-nearest Ga pairs reproduces the known composition dependence of the magnetostrictive constant ${\lambda }_{100}$ in the composition range ${\text{0<X}}_{\mathrm{Ga}}\text{<0.23}$ with only one adjustable parameter. Its value suggests a cluster size of 12 atoms.