Optimization of the Multilayer Structures for a High Field-Sensitivity Biochip Sensor Based on the Planar Hall Effect

We have investigated the planar Hall effect (PHE) in three multilayer structures such as a bilayer, a spin-valve and a weak exchange bias coupling bilayer structure introduced a very thin Cu spacer layer between the antiferromagnetic and ferromagnetic layers. These thin films are Ta(3)/NiFe(10)/IrMn(10)/Ta(3) (nm), Ta(3)/NiFe(10)/Cu(1.2)/NiFe(2)/IrMn(10)/Ta(3) (nm), and Ta(3)/NiFe(10)/Cu(0.2)/IrMn(10)/Ta(3) (nm), respectively. The active layers in all three structures were kept constant. The field-sensitivity of the fabricated PHE sensors obtained for the respected structures are about 1.6 muV middot Oe^-1, 5 muV middot Oe^-1, and 12 muV middot Oe^-1, respectively. The results suggest that the sensor based on a weak exchange bias coupling structure has the highest field-sensitivity compared with the others. The proposed weak exchange bias coupling structure emphasizes for the development of the PHE sensor materials.