Challenges for Sub-PicoTesla Magnetic-Tunnel-Junction Sensors

Published

October 12, 2021

Author(s)

Robert McMichael, Philip Pong, John Unguris, William F. Egelhoff Jr., A Edelstein, E Nowak, Sean R. Parkin

Abstract

The extension of small, inexpensive, low-power magnetic sensors into the sub-picoTesla regime, which is currently dominated by fluxgates and SQUIDS, would be a paradigm shift for the field of magnetic sensors. The necessary elements for sub-picoTesla MTJ sensors have been successfully demonstrated separately in the past year. If these elements can be integrated into operational systems without significant losses in performance then, in principle, sensitivities of a few femtoTesla/rt(Hz) at 1 Hz may be possible. Theoretical modeling indicates that an MTJ sensor incorporating those developments and equaling existing MTJs in other respects would have an ultimate noise floor (above which fields could be detected) of 5.5 femtoTesla/rt(Hz) at 1 Hz. This sensitivity is more than a factor of 104 better than existing magnetoresistive sensors. This paper presents the results of theoretical modeling, illustrates the experimental challenges involved in the integration of these developments into actual sensors, illustrates the trade-offs faced if there are losses in performance upon integration, and discusses issues associated with real-world applications of these sensors to ultra-low field measurements.

Citation

Journal of Applied Physics

Pub Type

Journals

Keywords

magnetic sonsor, sub-picotesla, tunnel junction MEMS

Citation

McMichael, R. , Pong, P. , Unguris, J. , Egelhoff Jr., W. , Edelstein, A. , Nowak, E. and Parkin, S. (2021), Challenges for Sub-PicoTesla Magnetic-Tunnel-Junction Sensors, Journal of Applied Physics (Accessed October 14, 2025)