Magnetoelasticity of Fe Ge (5 ≪ x ≪ 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) 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.