Enhancement of giant magnetoresistance properties of NiO spin valves with an oxidized free layer naturally in the air

The effect of specular electron scattering on the natural oxidation of a free layer in NiO spin valves has been investigated. The magnetoresistance ratio and the exchange biasing field (Hex) of NiO(600Aa)/Ni81Fe19(50Aa)/Co(7Aa)/Cu(20Aa)/Ni81Fe19(70Aa) spin valves were increased from 4.9% to 7.3%, and 110 to 170 Oe after the natural oxidation in the atmosphere for 80 days, respectively. The sheet resistance ρ decreased from 28 to 17 μΩm, but Δρ did almost not change after the oxidation. The spin valves enhanced by the specular electron scattering in the naturally oxidized Co/NiFe/NiFeOx free layer were confirmed from the depth profiles using Auger electron spectroscopy. [copyright] 2001 American Institute of Physics