Nanodevices & Nanostructures

Magnetic Tunnel Junction Nanosensors
MgO based magnetic tunnel junction (MTJ) stacks exhibiting large tunneling magnetoresistance (TMR) and a low resistance-area product (RxA) stand out as the best starting point for nanometric sensing devices.
In collaboration with INL we developed nanoscale MTJ sensors with stack incorporated bias which yielded top sensitivities reported for nanometric devices without using external biasing. Furthermore, these values are very competitive with those reported for single micrometric spin-valve sensors ~ 1 %/mT without adding flux-guides or permanent magnets.  Our design has thus the major advantage of having a high spatial resolution allied to a linear operation range (and thus sensitivity) controlled by the biased sensing layer . 

Spin Valve Nanosensors

When combined with magnetic flux concentrators, spin valve sensors may provide the desired features for room temperature detection of low magnetic fields within the sub-nanoTesla range. To fulfill such requirements os high spatial resolution one solution relies on the miniaturization of the magnetoresistive sensors down to sub-micrometric or nanometric scale dimensions, depending on the desired resolution.
However, a reduction in the sensor size leads to a significant increase in the demagnetizing effects which leads to a decrease in sensitivity. Strategies focusing either on the materials side or by employing external elements are developed towards significant gains in sensitivity recovering in part the loss due to shrinking size.