Magnetoelasticity of Fe $_{100-x}$ Ge $_{x}(5 \ll x \ll 18)$ Single Crystals From 81 K to 300 K

Temperature dependent magnetoelastic properties of Fe _{100 - x}Ge_x(5 < x < 18) single crystals have been measured. Tetragonal magnetostriction (3/2) lambda₁₀₀ measurements at x = 5.7, 12.1, 14.9, and 17.7 were performed between 78 K and 426 K and resonant ultrasound spectroscopy measurements were used to determine the shear elastic constant c´ from 5 K to 300 K for x = 6.4, 7.2, 10.8, 14.6, 17.7 , and 17.9 . A clear distinction was observed between the temperature dependencies of lambda₁₀₀ for the A2 and D0₃ phases of Fe_100-xGex . The elastic constant c´ displays a monotonic decrease with concentration through the different phases (6 < x < 18) and at all temperatures. Experimental values of the tetragonal magnetoelastic coupling constant -b ₁ at 81 K were remarkably consistent with theoretical values determined by density functional calculations at 0 K.