A Edelstein, J Burnette, Greg Fischer, S F. Cheng, William F. Egelhoff Jr., Robert McMichael, E Nowak
Recent innovations may lead to magnetic sensors that are smaller, more sensitive and/or cost less than current magnetometers. Examples of this are the chip scale atomic magnetometer, magnetic tunnel junctions with MgO barriers, and a device for minimizing the effect of 1/f noise, the MEMS flux concentrator. In the chip scale atomic magnetometer researchers have been able to fabricate the light source, optics, heater, optical cell, and photodiode detector in a stack that passes through a silicon wafer. Theoretical and subsequent experimental work led to the observation of magnetoresistance values of 400% at room temperature in magnetic tunnel junctions with MgO barriers. The large magnetoresistance occurs because electrons in the majority band can tunnel more easily through the MgO barrier than electronics in the minority band. The MEMS flux concentrator has the potential to increase the sensitivity of magnetic sensors at low frequencies by more than an order of magnitude. The MEMS flux concentrator does this by shifting the operating frequency to higher frequencies where 1/f noise is unimportant. The shift occurs because the motion of flux concentrators on MEMS flaps modulates the field at kHz frequencies at the position of the sensor. Though miniaturization is generally beneficial, tradeoffs are necessary because some properties sich as noise worsen with decreasing size.
Journal of Vacuum Science and Technology
low frequency, magnetic sensors, magnetometers, magnetoresistance, miniatureization
, Burnette, J.
, Fischer, G.
, Cheng, S.
, Egelhoff Jr., W.
, McMichael, R.
and Nowak, E.
Advances in Magnetometry Through Miniaturization, Journal of Vacuum Science and Technology
(Accessed December 11, 2023)