Strong antiferromagnetic interlayer exchange coupling induced by small additions of Re to an Ir interlayer in synthetic antiferromagnetic systems

Synthetic antiferromagnetic (AF) pinned layers are widely used in order to reduce the stray field of the pinned layer and stabilize the magnetic alignment of the reference layer in perpendicular magnetic tunnel junctions (MTJs). Here, a detailed study of Re concentration dependence of the magnitude of interlayer exchange coupling (|J_ex|) in a synthetic AF system with an Ir-Re interlayer is conducted. We observed strong AF interlayer exchange coupling caused by small amounts of Re addition and phase shift of the AF peak to thinner interlayer region in synthetic AF systems with Ir-Re interlayer. A synthetic AF system with an Ir-Re interlayer has strong AF interlayer exchange coupling and perpendicular magnetic anisotropy which are stable up to 673K annealing, which is compatible with CMOS back-end of line (BEOL) processing. First-principles calculations demonstrate good agreement with experiments, which show a peak of |J_ex| around Re concentration of less than 5 atomic%. The observed Ir-Re interlayer would be one of the promising interlayer materials for MTJs with the synthetic AF structure and be useful for future nonvolatile high-speed memories and logic circuits.