Magnetoelectric cantilever sensors under inhomogeneous magnetic field excitation

Abstract

The behavior of strain-coupled composite magnetoelectric cantilever sensors under excitation with an inhomogeneous magnetic field is investigated. We consider a local excitation generated by a ring-shaped copper coil with one winding, variably positioned around the sensor. 3D finite-element-method simulations of the sensitivity along the longitudinal sensor axis are conducted and compared to the experimental results. The investigated sensor consists of a 2 µm thick magnetostrictive layer [(Fe90Co10)78Si12B10] and a 2 µm thick AlN piezoelectric layer on the opposite sides of a 350 µm thick silicon cantilever of 26.25 mm length and 2.45 mm width. The sensitivity along the sensor axis is investigated for three different frequencies—one below the resonance frequency, one at resonance, and one above resonance. A rich position-dependent sensitivity behavior is observed in simulations and experiments with a maximum sensitivity at ∼4 mm from the fixed end of the cantilever for all three frequencies. Below and at the resonance frequency, a monotonously decreasing sensitivity is observed toward the free end of the cantilever. For the frequency above resonance, we observe a position of zero sensitivity at ∼17 mm from the fixed end and a subsequent second maximum of sensitivity. We attribute the zero sensitivity to the destructive interference of local excitation and resonance effects.