A Novel MEMS DC Magnetic Sensor Using Thermomagnetic-Piezoelectric Materials with a Coil-Less Reset Approach

Abstract

We report a novel MEMS DC magnetic sensor using thermomagnetic-piezoelectric materials with a coil-less magnetization-reset approach. The magnetic sensor consists of a silicon MEMS diaphragm, a piezoelectric PZT thin film, and a thermomagnetic Gadolinium (Gd) sheet. Due to the Gd's thermomagnetic property, the sensor at low temperature (for instant, 9 degrees C.; below its Curie temperature which is in room temperature range) can sense ambient DC magnetic fields. Without using on-chip coils, the sensor can be easily reset by heating the sensor higher than its Curie temperature (for example, 45 degrees C. According to experimental results, the sensor successfully senses DC magnetic field from 2 to 100 Gauss and is 45 degrees C. When comparing to conventional NEMS, MEMS, and AMR magnetic sensors (i.e., using magnetic materials requiring on-chip magnetization-reset coils which occupy huge chip footprint), our sensor with the coil-less reset approach can significantly reduce the sensor footprint.