Tuning the magnetic field sensitivity of planar Hall effect sensors by using a Cr spacer layer in a NiFe/Cr/IrMn trilayer structure

Planar Hall effect (PHE)-based magnetic field sensors have recently received considerable attention due to their fascinating properties. For the NiFe/spacer/IrMn trilayer PHE sensor structures, tuning the exchange bias via a spacer layer is very crucial due to its direct effects on the sensor's magnetic field sensitivity. Here the effect of Cr spacer layer thickness on PHE sensitivity and exchange bias is investigated in NiFe (10 nm)/Cr (t$_{Cr})$/IrMn (20 nm) trilayer structures where the t$_{Cr}$ varied between 0.0 nm and 1 nm with a step of 0.1 nm. As the t$_{Cr}$ increased, we observed a fast decrease in exchange bias field. When the thickness of Cr spacer layer increased up to 0.7 nm, a maximum sensitivity of 4.4 $\mu $V/(Oe$\cdot $mA) was obtained. Besides, sensor voltage exhibited \textpm 100 nV noise level. With this noise level, a 1.6 $\mu $T magnetic field resolution was achieved.