Nanoelectronics High Sensitivity and High Spatial resolution Magnetic Field Sensors

The ability to integrate tunnel junctions in standard CMOS technology together with the readout simplicity (linear resistance variation with respect to external magnetic fields) and the large TMR of CoFeB/MgO/CoFeB make magnetic tunnel junction sensors an ideal interface between electronic platforms and the physical world whenever magnetic fields are involved.

The magnetic sensing ability of magnetic tunnel junctions is being explored at INL aiming a number of different applications :

1) Nanoelectronics: hard disk drive read heads (targeting TMR~100% at RxA~0.1 Ωµm2); magnetic field sensors for the automobile industry (angle, current and mangetic field sensors); magnetic field sensors for hybrid devices (MEMS-Spintronics accelerometers)

2) Nanomedicine: integrated Spintronics  and Microfluids lab-on-chip platform using manetic markers ; high density magnetic imaging matrixes to monitor the human body magnetic activity

The production of high sensitivity sensors is focused on the development of linearization methods of large TMR CoFeB/MgO/CoFeB MTJs (TMR~200%) which are able to provide sensors with reduced coupling and coercive fields (Hc<5Oe, Hk<5Oe), sharp linear response (linear range tunable between 20-100 Oe) and stable domain distribution both in the large area limit (required for devices operating at very low frequency) and in the sub-micron range (required for large spatial resolution devices).

To that end, complex MTJ stacks and methods to produce MTJs with reference layers in opposite directions (required to produce full Wheatstone bridges) are being developed.