A resonant magnetic microsensor based on magnetic torque with piezoresistive readout

Magnetic sensors with high sensitivity are critical for various technological applications. This paper presents a highly sensitive magnetic sensor based on magnetic torque. The sensor comprises a silicon cantilever with a micro-pillared soft magnet at its end. A piezoresistive strain sensing element is integrated into the silicon cantilever for detecting vibration signals. The prototype of the resonant magnetic sensor is designed, fabricated, and evaluated. When an alternating magnetic field, generated by a coil, is applied to the cantilever, the micro-pillared magnet undergoes pendulum-like vibrations due to magnetic torque. Additionally, the application of the alternating magnetic field, which causes the external magnetic field to change the effective spring constant of the silicon cantilever, results in a change in resonant frequency. The evaluation results demonstrate that the fabricated magnetic sensor achieves a maximum sensitivity of 114.02 Hz/mT and a minimum detectable magnetic field of 35.7 nT. These findings suggest the sensor's potential for high-sensitivity magnetic field measurements in various applications.