The effect of partial substitution of Ge for Ga on the elastic and magnetoelastic properties of Fe–Ga alloys

Both components of the tetragonal magnetoelastic constant b1: the saturation magnetostriction, λγ,2=(3/2)λ100, and the magnetic-field saturated shear elasticity, c′=(c11−c12)/2, were investigated over a wide temperature range for the magnetostrictive Fe1−x−yGaxGey alloys, (x+y≅0.125, 0.185, and 0.245; x/y≅1 and 3). The magnetostriction was measured from 77 to 425 K using standard strain gage techniques. Both shear elastic constants (c′ and c44) were measured from 5 to 300 K using resonant ultrasound spectroscopy. Six alloy compositions were prepared to cover three important regions: (I) the disordered solute α-Fe region, (II) a richer solute region containing both disordered and ordered phases, and (III) a rich solute region containing ordered multiphases. Our observations reveal that, when the data is presented versus the total electron/atom (e/a) ratio, the above regions for both the ternary and binary alloys are in almost perfect alignment. Following this analysis, we find that the magnetoelastic coupl...