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 b(1): the saturation magnetostriction, lambda(gamma,2)=(3/2)lambda(100), and the magnetic-field saturated shear elasticity, c' = (c(11)-c(12))/2, were investigated over a wide temperature range for the magnetostrictive Fe1-x-yGaxGey alloys, (x+y congruent to 0.125, 0.185, and 0.245; x/y congruent to 1 and 3). The magnetostriction was measured from 77 to 425 K using standard strain gage techniques. Both shear elastic constants (c' and c(44)) 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 alpha-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 coupling, b(1), peaks for both the binary and the ternary alloys at e/a similar to 1.35. The values of c' as well as of lambda(gamma,2) in region I of the ternary alloys, when plotted versus e/a, fall appropriately between the binary limits. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3368108]