Magnetic field dependence of galfenol elastic properties

Elastic shear moduli measurements on Fe 100 − x Ga x ( x = 12 - 33 ) single crystals (via resonant ultrasound spectroscopy) with and without a magnetic field and within 4-300 K are reported. The pronounced softening of the tetragonal shear modulus c ′ is concluded to be, based on magnetoelastic coupling, the cause of the second peak in the tetragonal magnetostriction constant λ 100 near x = 28 . Exceedingly high Δ E effects ( ∼ 25 % ) , combined with the extreme softness in c ′ ( c ′ < 10 GPa ) , suggest structural changes take place, yet, gradual in nature, as the moduli show a smooth dependence on Ga concentration, temperature, and magnetic field. Shear anisotropy ( c 44 ∕ c ′ ) as high as 14.7 was observed for Fe 71.2 Ga 28.8 .