Magnetic field dependence of galfenol elastic properties

Elastic shear moduli measurements on Fe100-xGax (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 X 100 near x=28. Exceedingly high Delta E effects (similar to 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 Fe71.2Ga28.8. (c) 2005 American Institute of Physics.