Magnetoresistance effects in spin-valve multilayers including three Ni-Fe-Co layers

Magnetoresistance effects have been investigated in spin-valve multilayers including three Ni–Fe–Co layers. The layered structure of the spin-valve multilayers are [AF1/Ni–Fe–Co/Cu/Ni–Fe–Co/Cu/Ni–Fe–Co/AF2/Si], where AF1 and AF2 are antiferromagnetic layers. The spin-valve multilayers including three Ni–Fe–Co layers show magneto-resistance ratios Δρ/ρ of 3.7% and 5.6% at around 1.5 kA/m. These values are higher than the 2.2% of a spin-valve sandwich that includes two Ni–Fe–Co layers, [Ni–Fe–Co/Cu/Ni–Fe–Co/Fe–Mn/Cu/Hf/Si]. It is found that the total resistivity changes (Δρ) of the spin-valve multilayers including three Ni–Fe–Co layers are twice that for the spin-valve sandwich that includes two Ni–Fe–Co layers. This is due to the fact that the number of Ni–Fe–Co/Cu interfaces in the spin-valve multilayers that include three Ni–Fe–Co layers is double that in the spin-valve sandwich that includes two Ni–Fe–Co layers.