A thermomagnetic-piezoelectric MEMS AC magnetic-field sensor demonstrating a novel room-temperature-range coil-less resetting/demagnetizing approach

Abstract

We report a novel thermomagnetic-piezoelectric MEMS AC magnetic-field sensor. The magnetic sensor consists of a silicon MEMS diaphragm, a piezoelectric PZT thin film, and a thermomagnetic Gadolinium (Gd) film covered by a Pt anti-oxidation layer. Due to the thermomagnetic-Gd/piezoelectric-PZT layered structure, the sensor not only can sense AC magnetic field, but also can be reset/demagnetized automatically at temperature higher than Gd’s Curie temperature which is in room-temperature range. Experimental results show that the sensor successfully senses AC magnetic field from 1 to 14 Gauss at 9 °C, and is automatically reset/demagnetized at 45 °C. While conventional MEMS and AMR magnetic sensors using magnetic materials require on-chip resetting/demagnetizing coils which need a huge footprint of the chip, our sensor utilizing the coil-less resetting/demagnetizing approach significantly reduces the sensor footprint. In the other hand, when comparing to conventional coil-less resetting/demagnetizing method (i.e., annealing magnetic material at hundreds °C), our coil-less resetting/demagnetizing approach is at room-temperature range (for instant, 45 °C).