MEMS-based narrow-bandwidth magnetic field sensors: preliminary assessment of prototypes regarding coercivity, remanence, and sensitivity.

Objectives: This study evaluates micro-electro-mechanical systems (MEMS) devices comprising cantilever piezoelectric resonators with powder-based permanent magnets (micromagnets) at the tip. Fabricated using a well-known PowderMEMS process given by the Fraunhofer Institute for Silicon Technology, these devices function as magnetic field sensors based on the magnetic torque detection principle, which arises from the interaction between the given micromagnets' dipole moment and the to-be-measured magnetic field. The study investigates how the magnetic state of the micromagnets influences the overall sensitivity of the provided Prototype MEMS-devices.

Methods: The performance of the first prototypes of this narrow-band magnetic field sensor was evaluated using two approaches: (1) a Vibrating Sample Magnetometer (VSM) to analyze the magnetic hysteresis loop and (2) sensitivity measurements at resonance frequency to determine the provided sensitivity under a predefined external magnetic flux density.

Results: Among the four prototypes analyzed, the device with the highest remanence and coercivity demonstrated superior sensing performance, achieving a sensitivity of 1,090 kV/T at the resonance frequency. The analysis showcased substantial variations in noise amplitude spectral density, and sensitivity, emphasizing the importance of magnetic hysteresis properties in sensor performance.

Conclusions: These findings highlight the potential of MEMS-devices with enhanced coercivity and remanence for enhanced sensing capabilities in compact sensor designs, particularly useful for array sensor configurations in narrow-bandwith medical applications.