FROM BULK TO FILM MAGNETOSTRICTIVE ACTUATORS

Bulk 3d-4f intermetallic compounds exhibiting a giant magnetostriction at room temperature have been developed since 1975 by A.E. Clark. Unt il recently, attempts to obtain thin films with high magnetoelastic co upling had failed, due to the sperimagnetic character of amorphous R-F e-2 alloys. Two ways have been recently proposed for overcoming this p roblem, namely preparing (i) R-Fe-2 nanocrystalline alloys, and (ii) R -Co-2 amorphous alloys. Both methods have shown to be promising while still further improved performances have been reached using composite materials as for example multilayer systems (similar to the spring-mag nets), which exhibit giant magnetostrictivity (exceeding 1000 MPaT-1 u nder only 2 mT). We shall review these new materials of interest for m icrosystems. (C) 1998 Elsevier Science S.A.