Validation of the microelectromechanical system flux concentrator concept for minimizing the effect of 1/f noise

Abstract

With the microelectromechanical system (MEMS) flux concentrator, we have been able to increase the operating frequency of small magnetic sensors above the region where 1/f noise dominates. The device accomplished this by modulating the field via the oscillatory motion of flux concentrators on MEMS flaps. Electrostatic comb drives were used to drive the MEMS flaps. We have demonstrated an increase in the signal to noise ratio at 1 Hz, that the power signal correctly depends on V4 where V is the amplitude of the voltage energizing the comb drives, and that the signal increases dramatically with vacuum packaging.

Field noise in tunneling magnetoresistance sensors with variable sensitivity

“…These indicate decisive role of anisotropy-induced noise reduction in overcoming noise-sensitivity scaling limit at low frequency. Integration of these sensors with high gain flux concentrator, 14 micromechanical flux concentrator, 15,16 or in series-parallel configuration 17 will lead to significant improvement in the field detectivity of high sensitivity TMR sensors. …”

Low frequency noise in La0.7Sr0.3MnO3 based magnetic tunnel junctions

“…However, they are not widely used in magnetic sensing application due to the poor noise floor exhibited, despite several alternative techniques proposed to overcome this problem. 6,7 Manganite-based MTJs, as for example, La 0.7 Sr 0.3 MnO 3 (LSMO)/SrTiO 3 (STO)/LSMO, exhibit TMR ratios as high as 1800% at low bias and temperature. [8][9][10][11] Nevertheless, in order to obtain a highly performing sensor noise features have to be characterized, especially the 1/f noise when the device is meant to be operated at low frequency.…”

Magnetostatic detection using magnetoresistive sensors with vertical motion flux modulation

“…Although some chopping techniques were taken for TMR sensors by Jander et al, only a slight improvement on the MSD ability was obtained. 3 Recently, flux modulation has been proposed to reduce the 1/f noise of MR sensors by Edelstein et al [4][5][6] In their prototypes, the detected magnetic field was modulated to higher frequency (tens of kHz) with a pair of flux concentrators driven by an electrostatic comb, which resulted in that the 1/f noise of a spin-valve GMR element was hundreds even thousands of times reduced. Subsequently, the electrostatic cantilevers and torsionators with flux guides were used to modulate the detected magnetostatic field (DMSF) by Guedes et al [7][8][9] So far, the 1/f noise of MR sensors has been reduced successfully, but the MSD ability still suffers from the poor modulation efficiency (mostly lower than 11%).…”