Perpendicular magnetic anisotropy (PMA) is induced in Co/Ni multilayers when they are grown on a (111) textured Au seed layer, provided it is at least 2 nm thick. The anisotropy increases with increasing Au thickness due to improved crystallinity. Postannealing treatments of as-grown [Co(0.3)/Ni(0.6)]5 (thicknesses in nanometer) multilayers enhance the coercivity and PMA up to an annealing temperature of 250 °C, but higher temperatures lead to intermixing of Co and Ni which diminishes PMA. The easy axis becomes in-plane for samples annealed at 400 °C. The improvement in PMA in Co/Ni layers due to annealing is limited by the Au seed layer thickness. Annealing also reduces the saturation magnetization by ∼ 15% due to the formation of superparamagnetic islands. Our results show that the PMA in Co/Ni multilayers can be improved by annealing up to 350 °C, which is required for the thermal stability of spin transfer torque memories.
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