Magnetic actuation of bending and torsional vibrations for 2D optical-scanner application

This paper deals with a magnetically actuated microresonator as a test devi ce for Light deflection applications (optical scanners). 2D scanning of a l aser spot was achieved with this device and an optical scanning window of n early 24 degrees was attained. Giant magnetostrictive thin films are used. They present the novel feature to produce wireless actuation in both bendin g and torsional modes, which can be decoupled at the corresponding resonanc e frequencies. In addition, depending on working conditions (bias field, ma gnetization orientation), the ratio between bending and torsional responses can be adjusted over a very large scale. We show how this ratio can be fix ed by two methods: (i) by an appropriate choice of the initial state of the magnetic thin film during its deposition, and (ii) by a DC magnetic field, which is applied during the device operation. The mechanical characterizat ion of the cantilever is presented. Anharmonic behavior due to large deflec tions was obtained. This nonlinear behavior is lessened with a folded-type mechanical structure. Torsional deflections up to 23 mu m, corresponding to mechanical rotations of +/-5.9 degrees angles have been attained at a fiel d as low as 3.5 mT, corresponding to only 2% of the anisotropy field. Bendi ng deflection can be twice in similar conditions. (C) 2000 Elsevier Science S.A. All rights reserved.