Advanced Magnetics and Spintronic Sensors

We develop magnetic sensor devices based tunneling magnetoresistance (TMR) effect. TMR device consists from two ferromagnetic layers separated by a thin nonmagnetic barrier. When a current is applied to one of those two ferromagnets, while their magnetization directions are parallel, the electrons can tunnel through the barrier and TMR shows low resistance (R_min). In contrary, an antiparallel magnetization provides a high resistance (R_max). The performance of the device is therefore determined by TMR ratio (%) = (R_max-R_min)/ R_min. We do linearization for the resistance (R)-magnetic field (H) change by the two-step annealing technique. We produce a very linear R-H curve indicating coherent rotation of magnetization of the sensing layer together with the reference layer, ensuring a very low noise sensor with detectivity 2 nT/Hz^0.5 @ 10 Hz. We also fabricate gas sensor devices using transition metal oxides as sensing layers.