Volume magnetostriction and structure of copper mold-cast polycrystalline Fe–Ga alloys

Abstract

The effect of the volume expansion on the total linear magnetostriction of Fe85Ga15, Fe80Ga20, and Fe71Ga29 mold-cast bulk alloys was investigated by measuring the change in length with applied field longitudinal and perpendicular to the temperature gradient during solidification. In the magnetically saturated state, due to the contribution of the volume expansion, the saturation magnetostriction for all three alloys was about 66 % of the total linear magnetostriction. The magnetostriction is strongly dependent on the direction of the temperature gradient, being larger in this direction. The substitution of Fe by Ga atoms increases the lattice constant and causes a change to the A2 crystal structure, which was confirmed by Mössbauer spectroscopy. The thermal-expansion coefficient increases with Ga content at temperatures between 4.2 and 150K.