Fabrication of giant magnetostrictive thin film actuators

Abstract

Sputterdeposited magnetostrictive films present an interesting opportunity to realize actuators in microsystems as they offer features like contactless, high frequency operation, simple actuator designs and a cost-effective manufacturing technique. Amorphous magnetostrictive films of the binary compound SmFe as well as of the ternary compound TbDyFe were prepared by d.c. magnetron sputtering using either a multitarget arrangement with pure element targets or cast composite-type targets. Depending upon the composition and the sputtering conditions, particulary upon the BIAS voltage, amorphous films with a giant magnetostriction of about 250 ppm (-220 ppm) at 0.1 T and 400 ppm (-300 ppm) at 0.5 T for the TbDyFe (SmFe) and an adjustable magnetic easy axis could be prepared. In view of applications in microsystem technologies (e.g. pumps, valves, positioning elements) these films have been tested in cantilever or membrane arrangements. The design of the actuators, such as the lateral patterning of the magnetostrictive films, have been modulated by means of fmite element calculations. For double clamped beams or clamped membranes, these calculations revealed that lateral patteming of the magnetostrictive films is essential in order to obtain large deflections.