Elasticity and magnetoelasticity of Fe-Ga solid solutions

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 1/2(C-11-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 1/2(C-11-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 0<X-Ga<0.23 with only one adjustable parameter. Its value suggests a cluster size of 12 atoms. (C) 2002 American Institute of Physics.