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1. Magnetic-field dependence of the noise in a magnetoresistive sensor having MEMS flux concentrators

Author

Ozbay, Arif, Nowak, E.R., Edelstein, A.S., Fischer, G.A., Nordman, C.A., and Cheng, Shu Fan

Subjects
Microelectromechanical systems -- Acoustic properties, Microelectromechanical systems -- Magnetic properties, Magnetoresistance -- Measurement, Magnetic fields -- Research, Business, Electronics, Electronics and electrical industries
Abstract

We report the dc and ac magnetic field dependence of the low-frequency noise in a microelectromechanical system (MEMS) flux concentrator device containing a giant magnetoresistance spin valve (SV). The noise is dominated by resistance fluctuations having a magnetic origin. Under nominally zero magnetic-field biasing conditions, the noise power is large and varies rapidly with small changes in magnetic field. Metastability between distinct resistive states is observed and can be suppressed with the application of a moderate longitudinal field. Stationary flux concentrators do not contribute excess noise, rather the dominant source of noise is the SVs themselves. This result indicates that the device is likely to increase the sensitivity of many magnetic sensors at low frequencies by orders of magnitude. Index Terms--Field sensor, flux concentrator, magnetometer, magnetoresistance, noise.

Published
2006

4. Low Cost, Low Power, High Sensitivity Magnetometer

Author

ARMY RESEARCH LAB ADELPHI MD, Edelstein, A. S., Burnette, James E., Fischer, Greg A., Koebke, M. G., Olver, Kimberly, Cheng, Shu-Fan, Edelhoff, Jr., William, Nowak, Edmund, ARMY RESEARCH LAB ADELPHI MD, Edelstein, A. S., Burnette, James E., Fischer, Greg A., Koebke, M. G., Olver, Kimberly, Cheng, Shu-Fan, Edelhoff, Jr., William, and Nowak, Edmund

Abstract

Because weapon systems, vehicles, and most communication systems all generate magnetic fields, magnetic sensors can provide useful military information. There has been significant recent progress in magnetometry. This progress includes chip scale magnetometers, magnetoelectric sensors, devices with much larger magnetoresistance (MR) and an ARL invention, the MEMS flux concentrator that is needed at low frequencies to take advantage of the larger MR values. In addition, better algorithms using total field measurements have been developed to take advantage of the improved magnetic sensors. Our main topic is the development of the MEMS flux concentrator. The MEMS flux concentrator has the potential to be a factor of 10 cheaper, consume 1% of the power, be a factor of 100 more sensitive at 1 Hz and occupy 0.001 the volume of the magnetic sensor element currently used in Army sensor systems, the Brown flux gate., See also ADM002187. Presented at Proceedings of the Army Science Conference (26th) held in Orlando, FL on 1-4 December 2008. Published in Army Science Conference (26th) Proceedings, December 2008. The original document contains color images.

Published
2008

5. The MEMS Flux Concentrator: Potential Low-Cost, High-Sensitivity Magnetometer

Author

ARMY RESEARCH LAB ADELPHI MD, Edelstein, Alan S., Fischer, Greg, Bernard, William, Nowak, Edmond, Cheng, Shu Fan, ARMY RESEARCH LAB ADELPHI MD, Edelstein, Alan S., Fischer, Greg, Bernard, William, Nowak, Edmond, and Cheng, Shu Fan

Abstract

Progress on the development of a device, the MEMS flux concentrator, for mitigating the problem of 1/f noise in magnetic sensors will be presented. The MEMS flux concentrator essentially eliminates the effect of 1/f noise by increasing the operating frequency of the sensor to a frequency region where 1/f noise is small. This is accomplished by putting flux concentrators on MEMS structures whose motion modulates the magnetic field at the position of the magnetic sensor. Depending on the sensor, mitigating the effect of 1/f noise will increase the sensitivity of magnetic sensors by one to three orders of magnitude. Combining the MEMS flux concentrator with magnetic tunnel junctions with MgO barriers should lead to low cost magnetic sensors that are able to detect 1 pT signals at 1 Hz., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL on 27-30 November 2006. The original document contains color images.

Published
2006

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