Program Highlights

Low-Power Picotesla Magnetoresistive Sensor

S. H. Liou and David Sellmyer
Nebraska MRSEC

Stephen E. Russek, Ranko Heindl, F. C. S. Da Silva, John Moreland, David P. Pappas
National Institute of Standards and Technology, Boulder, CO

L. Yuan and J. Shen
Western Digital Corporation, Fremont, CA

We have developed a low power, compact, magnetoresistive sensor that combines a 64 element magnetic tunnel junction bridge and a set of low noise magnetic flux concentrators. Sensitivity in the range of a few picotesla at 1 kHz has been achieved. Magnetic field sensitivities of our prototype magnetic sensor are about 4.5 pT/Hz1/2 at 1 kHz, and 222 pT/Hz1/2 at 1 Hz. The magnetic sensor only dissipates 6 mW of power while operating.

This research is supported by the National Science Foundation, Division of Materials Research, Materials Research Sciences and Engineering Program, Grant 0820521.

Our prototype magnetoresistive sensor is operated by a set of coin-cell (3 volts) batteries. The two bulk pieces lying on both sides of the MR sensor are magnetic flux concentrators. The MTJs was arranged as an asymmetric bridge in between the two magnetic flux concentrators. The operating power is less than 6 mW.