Effect of Ru thickness on spin flop in synthetic spin valves

Synthetic spin valves with structure of sub/Ta/NiFe/IrMn/AP2/Ru/AP1/Cu/CoFe/Ta were systematically studied by varying the Ru thickness in the artificial antiferromagnetic structure. Spin-valve films were deposited using a Nordiko 9606 PVD system and annealed in a magnetic field of 6 kOe parallel to the easy axis of the free layer. MR(H) and M(H) curves of these spin valves were experimentally measured and quantitatively simulated using Boltzmann transport equation and coherent magnetization rotation model. The corresponding interlayer exchange coupling and pinning angle of these spin valves were determined from simulation. Both experimental measurement and simulation results have shown that the characteristics of synthetic spin valves depend strongly on the thickness of Ru. The pinning field for spin valves with ultrathin Ru layer was canted. This was evidenced in the reduction of the measured MR ratio and shape of MR curve when Ru is thinner than 0.5 nm. It is concluded that the pinning angle is determined by the spin-flop angle of one of the pinned layers (AP2) at spin-valve annealing temperature, which is in turn determined by the final balance between the interlayer antiferromagnetic coupling field and the external applied magnetic field during annealing. (C) 2002 American Institute of Physics.