A high-resolution MEMS magnetoresistive sensor utilizing magnetic tunnel junction motion modulation driven by the piezoelectric resonator
Haoqi Lyu, Zhenxi Liu, Zheng Wang, Wuhao Yang, Xingyin Xiong, Jiamin Chen, Xudong Zou
Abstract
High-sensitivity MEMS magnetoresistive (MR) sensors have attracted ever-increasing attention due to their ability to detect weak magnetic fields, but the resolution is severely limited by the 1/f noise. This paper reports a MEMS MR sensor that can effectively suppress the 1/f noise by modulating the magnetic field signal to the higher frequency region utilizing magnetic tunnel junction vertical motion modulation based on the MEMS piezoelectric cantilever resonator. The magnetic sensitivity can be increased to 2283.3%/mT with a high magnetic gain of 39.3 by integrating the structure-optimized fixed magnetic flux concentrators. The signal-to-noise ratio of the MEMS MR sensor can be improved by three orders of magnitude and the 160 pT/√Hz resolution can be reached. These results make the MEMS MR sensor based on the MTJ motion modulation a competitive candidate in the pico-Tesla magnetic detection.