Observation of parallel-antiparallel magnetic coupling in ultrathin CoFeB-MgO based structures with perpendicular magnetic anisotropy
A series of MgO/CoFeB/Ta(x)/CoFeB/MgO multilayered structures is fabricated by sputtering. Magnetic parallel-antiparallel oscillatory behavior is observed as a function of Ta thickness, while perpendicular magnetic anisotropy (PMA) also exists due to the MgO stabilization. The oscillatory period is ∼1.3 nm with a maximum interlayer exchange coupling (IEC) of ∼0.02 erg/cm2. The Ta spacer can be replaced by a layer of other metals to form a general perpendicular synthetic antiferromagnetic structure. The tuning of IEC and PMA by insertion of Ru is discussed.