Thermally enhanced perpendicular magnetic anisotropy behaviors of ultrathin [Co/Pd]_n multilayers via NiO_x capping layer

We report the enhanced perpendicular magnetic anisotropy (PMA) features of ultrathin [Co/Pd]₃ multilayers (MLs) employing a NiO_x insertion layer at high annealing temperatures. Thermally enhanced PMA in [Co/Pd]₃/NiO_x (capping layer) MLs were achieved at a specific capping layer thickness, while no PMA responses were observed for a NiO_x (buffer layer)/[Co/Pd]₃ ML, regardless of NiO_x thickness. X-ray diffraction observations, including rocking curves, identified the relatively different crystalline characteristics of the NiO_x capping and buffer layers. Origin of the enhanced PMAs of [Co/Pd]₃ MLs containing a NiO_x capping layer is described based on the NiO_x capping effect possibly providing additional Co/Oxide i-PMA under high-temperature annealing