Magnetostrictive Properties of Fe-Ga/Ni Bimorph Layers

Abstract

Giant magnetostrictive Fe-Ga alloys are expected as actuator/sensor materials with high respective velocity and large stress created by the magnetostriction. To develop magnetostrictive material induced by low magnetic fields, we investigated magnetostrictive (positive magnetostriction/negative magnetostriction) bimorph layers, that is, Fe₈₀Ga₂₀ ribbon (146 μm)/Ni (14 μm) film produced by magnetron sputtering. The Fe₈₀Ga₂₀ ribbon was prepared by rapid solidification. The magnetostrictive property of the cantilever-type foil was determined experimentally using the optical lever method. The displacement of the upper part of the foil with a length of 22 mm was 530 μm under a low steady magnetic field of 40 kAm⁻¹ and exhibits little hysteresis. These magnetostrictive properties are also maintained under a low-frequency alternating magnetic field. Moreover, the displacement of the foil at the mechanical resonance frequency exhibits a peak and reaches 2.0 mm at a weak magnetic field of 4 kAm⁻¹. The magnetostrictive bimorph layers are useful for applications in microdevices such as micropumps.