GMR properties of spin valves using multilayered Co₉₀Fe₁₀ for free magnetic layer

To achieve higher GMR ratios in spin valves, Co₉₀Fe₁₀ films were used as the free and the pinned layer. A single layer of CoFe 100 Å and a multilayer of CoFe 18 Å/(Cu 8 Å/CoFe 18 Å)₅ were used as the free layer. Although the single layer CoFe showed large coercivities of 58 Oe along the easy axis and 40 Oe along the hard axis, the multilayer CoFe 18 Å/(Cu 8 Å/CoFe 18 Å)₅ showed smaller coercivities of 10 Oe along the easy axis and 1.5 Oe along the hard axis on a 100 Å thick Ta underlayer. The anisotropy field of the multilayer was 20 Oe. The film structures of the free layer were evaluated and it was found that the multilayer had higher oriented (111) texture than the single layer. The reason why the multilayer had higher oriented (111) texture was that the Cu layers between CoFe layers helped to have highly oriented (111) texture. To reduce the anisotropy field, the film was annealed in a magnetic field perpendicular to the initial easy axis at several temperatures. As the result, the anisotropy field was reduced to 3 Oe and the coercivity was 4 Oe after annealing at 140 °C. The GMR ratio of the spin valve of Ta 100 Å/CoFe 18 Å/(Cu 8 Å/CoFe 18 Å)₄XCu 24 Å/CoFe 30 Å/FeMn 150 Å/Ta 50 Å was 7% after the annealing.