Angle-Dependent In-Plane Magnetic Field Detection by MEMS Resonant Sensor

Miniaturized piezoelectric/magnetostrictive resonators have been proven to be effective magnetometers with the $\Delta $ E effect. Here, we reported the magnetic field angle-sensitive behavior of compact piezoelectric/magnetostrictive Lamb mode resonators. Utilizing magneto-optic Kerr effect (MOKE) microscopy, we observed magnetic domain reversals over in-plane angles from 0° to 90°. This revealed shifts in remnant magnetizations and coercive fields of the device in response to the external magnetic field. Additionally, we analyzed the angle dependence of frequency shift on the external magnetic field directions. The largest shift was approximately 90 kHz at 90°. As the angle decreased, frequency shifts gradually reduced, approaching the minimal at 0°. The MEMS resonant sensor reached the highest sensitivity of 25 Hz/ $\mu $ T when the magnetic field was along at 90°.