Effect of grain shape on magnetostrictive polycrystalline Fe–Ga alloys

Polycristalline Fe 100− x Ga x alloys with 15 < x < 30 present high saturation magnetostriction, which depends strongly on the preparation method. We found that the longitudinal magnetostrictions of copper mold-cast polycrystalline Fe 80Ga 20 and Fe 71Ga 29 alloys are three times larger along the axis parallel to the temperature gradient, than those along the axis perpendicularly to the TG. For x = 0 and 29 the magnetostriction increases with decreasing temperature, reaching a value of 150 ppm at 4.2 K in the Fe 71Ga 29 alloy. However for x = 20 a different behavior was found. These results are related to the particular microstructure composed of large and elongated grains and with crystallographic texture.