[Ni/Mn] superlattice-based spin-valves with high thermal stabilities

Ni/Mn superlattice-based spin-valve films were fabricated by dc sputtering method. Coercivity (H_c) of the pinned layer and exchange coupling field (H_ex) between the pinned layer and pinning Ni/Mn superlattice with an antiferromagnetic phase were investigated in order to optimize the deposition conditions and annealing process. The thickness of each layer was controlled by deposition time. The H_ex and H_c of Ni/Mn superlattice-based spin-valves increased gradually with the number of annealing cycles and number of bilayers. At the Ni composition of 38 at.% for the annealing time of 12 hours, the largest H_ex and H_c of glass/[Ni/Mn]₅₀/NiFe(60 Å)/Cu(30 Å)/NiFe(60 Å) spin-valves are 305 Oe and 245 Oe, respectively. However, the magnetoresistance (MR) ratio is small, due to the shunting effect of Ni/Mn superlattice and the interdiffusion between NiFe and Cu