Ab initio calculations of phase behaviour and subsequent magnetostriciton in Fe_1-xGa_x within the disordered local moment picture

Abstract

A holistic approach for studying both the nature of atomic order and finite-temperature magnetostrictive behavior in the binary alloy Galfenol (Fe$_{1−x}$Ga$_x$ , $0 \leq x \leq 0.25$) is presented. The phase behavior is studied via atomistic modeling with inputs from ab initio calculations, and the ordered phases of interest at nonstoichiometric concentrations are verified to exhibit B2- and D0₃-like order. The finite-temperature magnetoelasticity of these phases, in particular the magnetoelastic constant $B_1$, is obtained within the same ab initio framework using disordered local moment theory. Our results provide an explanation for the origin of the experimentally observed peak and subsequent fall in the material’s magnetostriction at $x\sim0.19$, which has been disputed. In addition, we show that it is possible to enhance the magnetostriction of D0₃−Fe₃Ga by removing a small fraction of electrons from the system, suggesting that a Fe-Ga-Cu or Fe-Ga-Zn alloy could exhibit greater magnetostrictive properties than Galfenol.