Achieving 1/f Noise Reduction with the MEMS Flux Concentrator

Though magnetic tunnel junctions (MTJ) with MgO barriers have magnetoresistance (MR) values as large as 400%, their usefulness as magnetic sensors at low frequencies is limited by 1/f noise. Here we present data showing that our device, the MEMS flux concentrator, does greatly decreases the problem of 1/f noise in magnetic sensors. The device has flux concentrators on MEMS structures that are driven to undergo oscillatory motion at their normal mode resonant frequencies. The motion of the flux concentrators increases the frequency of the field at the position of the sensor to 48 kHz where 1/f noise is much smaller. New modeling results of our recent design are a factor of 30 increase in the percentage of field modulation and a factor of 15 enhancement of the magnetic field. The new design features were using large, stationary flux concentrators that overlap smaller, moving flux concentrators and using the in phase normal mode. Sensors incorporating these features will be able to detect a few pT/Hz(1/2) at 1 Hz.