Magnetoresistive properties and thermal stability of CoNbZr-based spin valves with Co₈₀Fe₂₀ ferromagnet

We investigated the dependence of CoFe composition on the magnetoresistance and thermal stability behavior of the CoNbZr-based SV. CoNbZr/Co ₈₀Fe₂₀/Cu/Co₈₀Fe₂₀/IrMn/CoNbZr stacks were sputter-deposited on Si/SiO₂ substrates. A comparison was also made with CoNbZr-based SV using a Co₉₀Fe₁₀ ferromagnet. MR ratio, exchange bias field (H_ex) and Δρof a CoNbZr/Co₈₀Fe₂₀ SV increased up to about 51% (3.5% →5.6%), 52% (280 Oe→348 Oe) and 19% (0.5 μΩcm→0.59 μΩ cm), respectively. The MR ratio of the CoNbZr/Co₈₀Fe ₂₀ SV was enhanced because of higher spin polarization of the Co ₈₀Fe₂₀ than that of the Co₉₀Fe₁₀. When the samples were annealed at 300°C for 10 min, MR ratio and H _ex of CoNbZr/Co₈₀Fe₂₀ SV increased about 48% (from 5.6% to 8.1%) and 52% (from 346 Oe to 536 Oe), respectively. According to the AES depth profile, Mn diffused outward direction (surface) predominantly in the CoNbZr/Co₈₀Fe₂₀ SV and to form Mn-oxides.