Micro-magnetostrictive vibrator using iron–gallium alloy

A micro-magnetostrictive vibrator using an iron–gallium alloy (Galfenol) drive element was investigated. Galfenol is an iron-based magnetostrictive material with magnetostrictions greater than 200 ppm, a high relative permeability μr > 70 and a Young’s modulus of ∼70 GPa. This material is machinable by conventional cutting techniques, and can operate under tensile, bending, and impact loads without degradation in performance. A micro-actuator using Galfenol, therefore, has advantages over a PZT type actuator in design simplicity, low drive voltage requirements, high robustness, and a wide temperature operating range. This paper describes the design, fabrication process, and performance of a micro-vibrator which utilizes either an un-annealed or stress-annealed Galfenol pin as the drive element. A displacement of 1.2 μm was observed with a high bandwidth of 30 kHz and a high tensile robustness withstanding a suspended weight of 500 g (6 MPa). The vibrator was also verified to be useful as a speaker which can generate clear sound from the power of a portable music player.