Development of strain and vibration sensor using magnetostriction of magnetic thin film

We fabricated a strain sensor using the inverse-magnetostrictive effect of magnetoelastic thin films, and applied it for vibration sensor. The sensor element consisted of 1 turn meander-patterned molybdenum (Mo) film as conductive layer and FeSiB magnetostrictive films that laminated a part of the meander. After annealing the element, the FeSiB films of the sensor element were subject to residual stress from Mo film and Si substrate, which induced a magnetic anisotropy of the FeSiB film via magnetoelastic coupling. From the impedance change of the element under compressive strain the sensor exhibited a gauge factor of 2, 160 at a carrier frequency of 150MHz under compressive strain. In addition, a phase-difference detection circuit was fabricated to evaluate the element as a vibration sensor. When an edge load of 20g was attached to the element, the maximum signal of 288mV (45mV/deg. ) correspond to vibration was obtained at the mechanical resonance frequency of 20. 8Hz.