Effect of annealing cycle on exchange biasing in [Ni/Mn] superlattice-based spin-valves

Spin-valves of [Ni/Mn](40)/NiFe/Cu/NiFe films were fabricated by the de sputtering method. The exchange coupling field (H-ex) and coercivity (H-c) between the pinned layer and pinning [Ni/Mn] superlattice with an antiferromagnetic phase were investigated in order to optimize the deposition conditions and the annealing process. The maximum values of H-ex and H-c of the [Ni(2 Angstrom)/Mn(3 Angstrom)](40)/NiFe(70 Angstrom)/Cu(30 Angstrom)/NiFe(60 Angstrom) films were 220 Oe and 110 Oe, respectively. However, the magnetoresistance ratio was as small as 0.4 % similar to 1.2 % due to a shunting effect and an interdiffusion between NiFe and Cu. The thermal stability of the film with a Ni-layer thickness of 1.8 Angstrom. and a pinned NiFe layer of 100 Angstrom was the best for the variations tried. From the results of an annealing cycle experiment on the spin-valves based on a [Ni/Mn] superlattice, the blocking temperature is expected to be over 300 degrees C.