The detectivity of magnetic tunnel junction (MTJ) sensors cannot be improved further because of the existence of 1/f noise. Micro - electromechanical systems (MEMS) integrated with magnetic flux concentrators (MFCs) can be an effective approach to suppressing 1/f noise for modulating low-frequency magnetic fields. The challenge in fabricating small-sized and low-noise MTJ-MEMS hybrid magnetic sensors is associated with the production of high-performance MFCs. For the preparation of MFCs applicable to MTJ-MEMS hybrid magnetic sensors, in this research, a novel Ta/Ni77Fe14Cu5Mo4 laminated structure was adopted to decrease the coercivity of the magnetic film dozens of times. Also, through optimizing the sputtering power, a relative permeability of 3246 was attained. The simulation outcomes demonstrated that the MTJ-MEMS hybrid magnetic sensor which utilized this magnetic film had a modulation efficiency of 65.4%, and it retained a competitive edge among similar magnetic sensors. A sensor prototype was successfully developed with 400-nm- thick MFCs by optimizing the fabrication process, and the MTJ's sensitivity was increased by 2.2 times. In comparison to low-frequency noise, the high-frequency noise of the MTJ showed a reduction in noise power spectral density by a factor of 686. MTJ sensors will be highly competitive candidates in the field of ultra-weak magnetic field detection because of these results.
Jiao et al. (Tue,) studied this question.