Fabrication and simulation of magnetostrictive thin-film actuators

Abstract

Sputter-deposited 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 have been 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, particularly upon the bias voltage, amorphous films with a giant magnetostriction of about 250 ppm (−220 ppm) at 0.1 T and 440 ppm (−300 ppm) at 0.5 T for TbDyFe (SmFe) and an adjustable magnetic easy axis can be prepared. In view of their applications in microsystem technologies (e.g., pumps, valves, positioning elements), these films have been tested in cantilever arrangements. The design of the actuators, such as the lateral patterning of the magnetostrictive films, has been modulated by means of finite-element calculations. For double-clamped beams or clamped membranes, these calculations reveal that lateral patterning of the magnetostrictive films is essential in order to obtain large deflections.