Strain and Vibration Sensor Based on Inverse Magnetostriction of Amorphous Magnetostrictive Films

High-sensitivity strain and vibration sensors were fabricated based on the inverse magnetostriction effect (Villari effect) of amorphous FeSiB films. To control the anisotropy of FeSiB, we used the residual stress of the laminated structure after annealing, which depends on the mechanical properties of the substrate, a nonmagnetic molybdenum film, and the FeSiB film. The anisotropy of the rectangular FeSiB film was induced in the width axis for a cover glass substrate and in the longitudinal direction for a Si wafer substrate. The sensors detect strain and vibration based on the impedance change associated with a high-frequency permeability change in the FeSiB film. A gauge factor of 19 900 was obtained for the sensor element on the Si wafer. When an edge load of 2 g was attached to the free edge of a cantilever structure for the sensor element on the cover glass substrate, weak vibrations with an acceleration of 0.1 m/s
²
in a frequency range of 10-100 Hz could be detected.