Mechanism of Large Magnetostriction of Galfenol

Galfenol (Fe_100-xGa_x) and related alloys are very promising new magnetostrictive materials for broad applications. Using the density-functional full-potential linearized augmented plane wave method, we performed systematic theoretical investigations to explore the mechanism that governs the large enhancement of magnetostriction in Galfenol. Here, we review our main theoretical findings on factors that lead to 1) the increase of magnetoelastic coupling; 2) the decrease of the tetragonal shear modulus; and 3) the phase instability. Several ternary FeGaX alloys (X=Zn, Pt, Ir, Ge) were predicted to have large magnetostrictive coefficients, through manipulating electron population and strength of spin-orbit coupling.