Joulian magnetostriction of Galfenol Fe83Ga17

The volume change on magnetic saturation of a large single crystal of Fe83Ga17 is measured by Joule's liquid displacement method. The crystal was tested in the as-grown state, and after annealing at 760 °C followed by slow cooling at 10 °C/min or quenching in water. In each case an upper limit to any volume change is < 5 ppm, establishing that the linear magnetostriction is volume-conserving. The conclusion agrees with that drawn from a study of a dozen small crystals of FeGa by the strain gauge method, but the demonstration of volume conservation using Joule's original method is more direct.