FIELD SENSITIVITY IN SPIN-VALVE SANDWICHES WITH ANTIFERROMAGNETIC NIOFILMS

We have investigated the MR ratios and the field sensitivities in Ni-8 1/Fe-19/Cu/Ni81Fe19 spin-valve sandwiches grown on antiferromagnetic N iO films as a function of the NiO thickness and the uniaxial depositio n field. The MR ratio has a maximum value of 4.5% at 420 Angstrom of N iO and 180 Oe of uniaxial deposition field, and a field sensitivity of 0.6 %/Oe. In older to obtain a higher MR ratio and field sensitivity, we have studied the effects of adding a Co layer between the interfac es of NiFe and Cu and also the effects of a NiO film on top or at bott om on the spin-valve sandwiches. The MR ratios sandwiches with the Co layer increases however, the sensitivity decreases to 0.37 %/Oe due to the high coercivity of Co. The Co inserted structure with the NiO fil m on top has a low MR ratio of 5.7% and a high sensitivity of 5.8 %/Oe The thermal stability of the sandwiches with the NiO film on top is s uperior to that of the NiO film at bottom.