Mechanical Resonant Magnetic Sensor Utilizing Magnetically Induced Compressive Load from Magnetostrictive Material

Abstract

A novel magnetic sensor composed of a silicon mechanical resonator and a magnetostrictive material is proposed, fabricated, and theoretically and experimentally evaluated. The sensor's measurement principle relies on the resonant-frequency change caused by a magnetically-induced compressive load resulting from a change in the size of the magnetostrictive material; the material expands upon application of an external magnetic field, and the resulting compressive load on the resonator changes its resonant frequency. The theoretical magnetic sensitivity and magnetic response are calculated based on material mechanics and thermomechanical noise. In our experiments, we evaluate the frequency response and fluctuation. The resonant frequency of the sensor linearly decreases as the magnetic field increases, which corresponds to a theoretical equation. The experimental magnetic resolution is 1.56×10^-4 T, while the theoretical one is 4.62×10^-10 T. This difference between theory and experiment is due to the low frequency stability of the device. The device sensitivity is improved by reducing the frequency fluctuation and sensor size. Our results indicate the feasibility of performing high-sensitivity measurements using the proposed mechanical resonant magnetic sensor.