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 similar to 1.3 nm with a maximum interlayer exchange coupling (IEC) of similar to 0.02 erg/cm(2). 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. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745905]