Field dependence of magneto-mechanical damping in magnetostrictive material for magnetic field sensing

The magneto-mechanical damping (MMD) in Terfenol-D is investigated by measuring the resonance vibration spectra of Terfenol-D bar. It is observed that MMD in Terfenol-D strongly depends on DC magnetic field (Hdc), and the ratio of the maximum variation of MMD over Hdc to the MMD at zero bias field achieves ∼255%. Taking advantage of this MMD dependence on Hdc, a coil-less DC magnetic field sensor is proposed by attaching a Terfenol-D layer to a piezoelectric micro-transformer. An analytical model for the composite micro-transformer is developed and validated. The results show that the transformer voltage gain is inversely proportional to its damping and therefore depends on Hdc. In addition, the sensor sensitivity can be controlled by changing the input voltage of the composite micro-transformer. Preliminary test results are presented as principle verification with a mesoscale Terfenol-D/Pb(Zr,Ti)O3 composite transformer. The experimental results show that the magneto-electric sensitivity with respect to Hdc achieves ∼5.54 mV/Oe under the excitation of an input voltage with magnitude of 0.5V.