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

Temperature dependent magnetoelastic properties of Fe
<sub>100

-

x</sub>
Ge
_x
(5 < x < 18) single crystals have been measured. Tetragonal magnetostriction (3/2) lambda
₁₀₀
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 lambda
₁₀₀
for the A2 and D0
₃
phases of Fe
_100-x
Ge
x
. 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.