Observation of surface step bunch induced perpendicular magnetic anisotropy using spin-polarized low energy electron microscopy.

Using spin-polarized low energy electron microscopy (SPLEEM), we observed surface step bunch induced perpendicular magnetic anisotropy in Fe/Ni bilayers grown on Cu(001) single crystal as well as in Ni/Co/Pd trilayers grown on W(110) crystal. On Cu(100) the formation of step bunches can be stimulated or suppressed by high- or low-temperature annealing cycles, respectively. SPLEEM images resolving the three dimensional magnetization vector in the Fe/Ni films grown on step bunched Cu(100) reveal an additional perpendicular magnetic anisotropy in regions near step bunches. In contrast, no extra perpendicular magnetic anisotropy is observed on low-temperature annealed Cu(100) featuring single-atom height step arrays. Additional investigation of Ni/Co/Pd trilayers on W(110) reveals the influence of step bunch orientation on magnetic anisotropy. Our observations may lead to opportunities for tailoring or patterning anisotropy in magnetic thin-films by controlling film morphology.