Bimorph-type Magnetostrictive Actuator/Sensor Thin Films

Giant magnetostrictive Fe-Pd and Fe-Ga thin films are expected as actuator/ sensor materials with high respective velocity and huge stress created by the magnetostriction. In order to develop magnetostrictive material induced by low magnetic field, we investigated bimorph-type magnetostrictive (positive magnetostriction / substrate / negative magnetostriction) thin films, that is, Fe-Pd(1, 3µm) or Fe-Ga(1, 3µm)/substlate /Ni(1, 3µm) by magnetron sputtering system. The substrate is Al(50µm) or kapton foil (125µm). Displacement of a upper part of these films was measured using an optical lever method. The displacement of the Fe70-Pd30(3µm )/ Al(50µm)/Ni(3µm)film ( length is 20 mm) was 280 μm under low DC magnetic field of 500 Oe and exhibits little hysteresis. These magnetostrictive properties are maintained under low alternating magnetic field. Moreover, the displacement of the film at the resonance frequency exhibits a peak and reached to 1.4 mm. The bimorph-type magnetostrictive thin film is useful for application in micro device as micro-pomp.